1 
2 /* pngrutil.c - utilities to read a PNG file
3  *
4  * Last changed in libpng 1.6.35 [July 15, 2018]
5  * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
6  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
7  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
8  *
9  * This code is released under the libpng license.
10  * For conditions of distribution and use, see the disclaimer
11  * and license in png.h
12  *
13  * This file contains routines that are only called from within
14  * libpng itself during the course of reading an image.
15  */
16 
17 #include "pngpriv.h"
18 
19 #ifdef PNG_READ_SUPPORTED
20 
21 png_uint_32 PNGAPI
png_get_uint_31(png_const_structrp png_ptr,png_const_bytep buf)22 png_get_uint_31(png_const_structrp png_ptr, png_const_bytep buf)
23 {
24    png_uint_32 uval = png_get_uint_32(buf);
25 
26    if (uval > PNG_UINT_31_MAX)
27       png_error(png_ptr, "PNG unsigned integer out of range");
28 
29    return (uval);
30 }
31 
32 #if defined(PNG_READ_gAMA_SUPPORTED) || defined(PNG_READ_cHRM_SUPPORTED)
33 /* The following is a variation on the above for use with the fixed
34  * point values used for gAMA and cHRM.  Instead of png_error it
35  * issues a warning and returns (-1) - an invalid value because both
36  * gAMA and cHRM use *unsigned* integers for fixed point values.
37  */
38 #define PNG_FIXED_ERROR (-1)
39 
40 static png_fixed_point /* PRIVATE */
png_get_fixed_point(png_structrp png_ptr,png_const_bytep buf)41 png_get_fixed_point(png_structrp png_ptr, png_const_bytep buf)
42 {
43    png_uint_32 uval = png_get_uint_32(buf);
44 
45    if (uval <= PNG_UINT_31_MAX)
46       return (png_fixed_point)uval; /* known to be in range */
47 
48    /* The caller can turn off the warning by passing NULL. */
49    if (png_ptr != NULL)
50       png_warning(png_ptr, "PNG fixed point integer out of range");
51 
52    return PNG_FIXED_ERROR;
53 }
54 #endif
55 
56 #ifdef PNG_READ_INT_FUNCTIONS_SUPPORTED
57 /* NOTE: the read macros will obscure these definitions, so that if
58  * PNG_USE_READ_MACROS is set the library will not use them internally,
59  * but the APIs will still be available externally.
60  *
61  * The parentheses around "PNGAPI function_name" in the following three
62  * functions are necessary because they allow the macros to co-exist with
63  * these (unused but exported) functions.
64  */
65 
66 /* Grab an unsigned 32-bit integer from a buffer in big-endian format. */
png_uint_32(PNGAPI png_get_uint_32)67 png_uint_32 (PNGAPI
68 png_get_uint_32)(png_const_bytep buf)
69 {
70    png_uint_32 uval =
71        ((png_uint_32)(*(buf    )) << 24) +
72        ((png_uint_32)(*(buf + 1)) << 16) +
73        ((png_uint_32)(*(buf + 2)) <<  8) +
74        ((png_uint_32)(*(buf + 3))      ) ;
75 
76    return uval;
77 }
78 
79 /* Grab a signed 32-bit integer from a buffer in big-endian format.  The
80  * data is stored in the PNG file in two's complement format and there
81  * is no guarantee that a 'png_int_32' is exactly 32 bits, therefore
82  * the following code does a two's complement to native conversion.
83  */
png_int_32(PNGAPI png_get_int_32)84 png_int_32 (PNGAPI
85 png_get_int_32)(png_const_bytep buf)
86 {
87    png_uint_32 uval = png_get_uint_32(buf);
88    if ((uval & 0x80000000) == 0) /* non-negative */
89       return (png_int_32)uval;
90 
91    uval = (uval ^ 0xffffffff) + 1;  /* 2's complement: -x = ~x+1 */
92    if ((uval & 0x80000000) == 0) /* no overflow */
93       return -(png_int_32)uval;
94    /* The following has to be safe; this function only gets called on PNG data
95     * and if we get here that data is invalid.  0 is the most safe value and
96     * if not then an attacker would surely just generate a PNG with 0 instead.
97     */
98    return 0;
99 }
100 
101 /* Grab an unsigned 16-bit integer from a buffer in big-endian format. */
png_uint_16(PNGAPI png_get_uint_16)102 png_uint_16 (PNGAPI
103 png_get_uint_16)(png_const_bytep buf)
104 {
105    /* ANSI-C requires an int value to accommodate at least 16 bits so this
106     * works and allows the compiler not to worry about possible narrowing
107     * on 32-bit systems.  (Pre-ANSI systems did not make integers smaller
108     * than 16 bits either.)
109     */
110    unsigned int val =
111        ((unsigned int)(*buf) << 8) +
112        ((unsigned int)(*(buf + 1)));
113 
114    return (png_uint_16)val;
115 }
116 
117 #endif /* READ_INT_FUNCTIONS */
118 
119 /* Read and check the PNG file signature */
120 void /* PRIVATE */
png_read_sig(png_structrp png_ptr,png_inforp info_ptr)121 png_read_sig(png_structrp png_ptr, png_inforp info_ptr)
122 {
123    size_t num_checked, num_to_check;
124 
125    /* Exit if the user application does not expect a signature. */
126    if (png_ptr->sig_bytes >= 8)
127       return;
128 
129    num_checked = png_ptr->sig_bytes;
130    num_to_check = 8 - num_checked;
131 
132 #ifdef PNG_IO_STATE_SUPPORTED
133    png_ptr->io_state = PNG_IO_READING | PNG_IO_SIGNATURE;
134 #endif
135 
136    /* The signature must be serialized in a single I/O call. */
137    png_read_data(png_ptr, &(info_ptr->signature[num_checked]), num_to_check);
138    png_ptr->sig_bytes = 8;
139 
140    if (png_sig_cmp(info_ptr->signature, num_checked, num_to_check) != 0)
141    {
142       if (num_checked < 4 &&
143           png_sig_cmp(info_ptr->signature, num_checked, num_to_check - 4))
144          png_error(png_ptr, "Not a PNG file");
145       else
146          png_error(png_ptr, "PNG file corrupted by ASCII conversion");
147    }
148    if (num_checked < 3)
149       png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
150 }
151 
152 /* Read the chunk header (length + type name).
153  * Put the type name into png_ptr->chunk_name, and return the length.
154  */
155 png_uint_32 /* PRIVATE */
png_read_chunk_header(png_structrp png_ptr)156 png_read_chunk_header(png_structrp png_ptr)
157 {
158    png_byte buf[8];
159    png_uint_32 length;
160 
161 #ifdef PNG_IO_STATE_SUPPORTED
162    png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_HDR;
163 #endif
164 
165    /* Read the length and the chunk name.
166     * This must be performed in a single I/O call.
167     */
168    png_read_data(png_ptr, buf, 8);
169    length = png_get_uint_31(png_ptr, buf);
170 
171    /* Put the chunk name into png_ptr->chunk_name. */
172    png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(buf+4);
173 
174    png_debug2(0, "Reading %lx chunk, length = %lu",
175        (unsigned long)png_ptr->chunk_name, (unsigned long)length);
176 
177    /* Reset the crc and run it over the chunk name. */
178    png_reset_crc(png_ptr);
179    png_calculate_crc(png_ptr, buf + 4, 4);
180 
181    /* Check to see if chunk name is valid. */
182    png_check_chunk_name(png_ptr, png_ptr->chunk_name);
183 
184    /* Check for too-large chunk length */
185    png_check_chunk_length(png_ptr, length);
186 
187 #ifdef PNG_IO_STATE_SUPPORTED
188    png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_DATA;
189 #endif
190 
191    return length;
192 }
193 
194 /* Read data, and (optionally) run it through the CRC. */
195 void /* PRIVATE */
png_crc_read(png_structrp png_ptr,png_bytep buf,png_uint_32 length)196 png_crc_read(png_structrp png_ptr, png_bytep buf, png_uint_32 length)
197 {
198    if (png_ptr == NULL)
199       return;
200 
201    png_read_data(png_ptr, buf, length);
202    png_calculate_crc(png_ptr, buf, length);
203 }
204 
205 /* Optionally skip data and then check the CRC.  Depending on whether we
206  * are reading an ancillary or critical chunk, and how the program has set
207  * things up, we may calculate the CRC on the data and print a message.
208  * Returns '1' if there was a CRC error, '0' otherwise.
209  */
210 int /* PRIVATE */
png_crc_finish(png_structrp png_ptr,png_uint_32 skip)211 png_crc_finish(png_structrp png_ptr, png_uint_32 skip)
212 {
213    /* The size of the local buffer for inflate is a good guess as to a
214     * reasonable size to use for buffering reads from the application.
215     */
216    while (skip > 0)
217    {
218       png_uint_32 len;
219       png_byte tmpbuf[PNG_INFLATE_BUF_SIZE];
220 
221       len = (sizeof tmpbuf);
222       if (len > skip)
223          len = skip;
224       skip -= len;
225 
226       png_crc_read(png_ptr, tmpbuf, len);
227    }
228 
229    if (png_crc_error(png_ptr) != 0)
230    {
231       if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) != 0 ?
232           (png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) == 0 :
233           (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_USE) != 0)
234       {
235          png_chunk_warning(png_ptr, "CRC error");
236       }
237 
238       else
239          png_chunk_error(png_ptr, "CRC error");
240 
241       return (1);
242    }
243 
244    return (0);
245 }
246 
247 /* Compare the CRC stored in the PNG file with that calculated by libpng from
248  * the data it has read thus far.
249  */
250 int /* PRIVATE */
png_crc_error(png_structrp png_ptr)251 png_crc_error(png_structrp png_ptr)
252 {
253    png_byte crc_bytes[4];
254    png_uint_32 crc;
255    int need_crc = 1;
256 
257    if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) != 0)
258    {
259       if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
260           (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
261          need_crc = 0;
262    }
263 
264    else /* critical */
265    {
266       if ((png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE) != 0)
267          need_crc = 0;
268    }
269 
270 #ifdef PNG_IO_STATE_SUPPORTED
271    png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_CRC;
272 #endif
273 
274    /* The chunk CRC must be serialized in a single I/O call. */
275    png_read_data(png_ptr, crc_bytes, 4);
276 
277    if (need_crc != 0)
278    {
279       crc = png_get_uint_32(crc_bytes);
280       return ((int)(crc != png_ptr->crc));
281    }
282 
283    else
284       return (0);
285 }
286 
287 #if defined(PNG_READ_iCCP_SUPPORTED) || defined(PNG_READ_iTXt_SUPPORTED) ||\
288     defined(PNG_READ_pCAL_SUPPORTED) || defined(PNG_READ_sCAL_SUPPORTED) ||\
289     defined(PNG_READ_sPLT_SUPPORTED) || defined(PNG_READ_tEXt_SUPPORTED) ||\
290     defined(PNG_READ_zTXt_SUPPORTED) || defined(PNG_SEQUENTIAL_READ_SUPPORTED)
291 /* Manage the read buffer; this simply reallocates the buffer if it is not small
292  * enough (or if it is not allocated).  The routine returns a pointer to the
293  * buffer; if an error occurs and 'warn' is set the routine returns NULL, else
294  * it will call png_error (via png_malloc) on failure.  (warn == 2 means
295  * 'silent').
296  */
297 static png_bytep
png_read_buffer(png_structrp png_ptr,png_alloc_size_t new_size,int warn)298 png_read_buffer(png_structrp png_ptr, png_alloc_size_t new_size, int warn)
299 {
300    png_bytep buffer = png_ptr->read_buffer;
301 
302    if (buffer != NULL && new_size > png_ptr->read_buffer_size)
303    {
304       png_ptr->read_buffer = NULL;
305       png_ptr->read_buffer = NULL;
306       png_ptr->read_buffer_size = 0;
307       png_free(png_ptr, buffer);
308       buffer = NULL;
309    }
310 
311    if (buffer == NULL)
312    {
313       buffer = png_voidcast(png_bytep, png_malloc_base(png_ptr, new_size));
314 
315       if (buffer != NULL)
316       {
317          memset(buffer, 0, new_size); /* just in case */
318          png_ptr->read_buffer = buffer;
319          png_ptr->read_buffer_size = new_size;
320       }
321 
322       else if (warn < 2) /* else silent */
323       {
324          if (warn != 0)
325              png_chunk_warning(png_ptr, "insufficient memory to read chunk");
326 
327          else
328              png_chunk_error(png_ptr, "insufficient memory to read chunk");
329       }
330    }
331 
332    return buffer;
333 }
334 #endif /* READ_iCCP|iTXt|pCAL|sCAL|sPLT|tEXt|zTXt|SEQUENTIAL_READ */
335 
336 /* png_inflate_claim: claim the zstream for some nefarious purpose that involves
337  * decompression.  Returns Z_OK on success, else a zlib error code.  It checks
338  * the owner but, in final release builds, just issues a warning if some other
339  * chunk apparently owns the stream.  Prior to release it does a png_error.
340  */
341 static int
png_inflate_claim(png_structrp png_ptr,png_uint_32 owner)342 png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
343 {
344    if (png_ptr->zowner != 0)
345    {
346       char msg[64];
347 
348       PNG_STRING_FROM_CHUNK(msg, png_ptr->zowner);
349       /* So the message that results is "<chunk> using zstream"; this is an
350        * internal error, but is very useful for debugging.  i18n requirements
351        * are minimal.
352        */
353       (void)png_safecat(msg, (sizeof msg), 4, " using zstream");
354 #if PNG_RELEASE_BUILD
355       png_chunk_warning(png_ptr, msg);
356       png_ptr->zowner = 0;
357 #else
358       png_chunk_error(png_ptr, msg);
359 #endif
360    }
361 
362    /* Implementation note: unlike 'png_deflate_claim' this internal function
363     * does not take the size of the data as an argument.  Some efficiency could
364     * be gained by using this when it is known *if* the zlib stream itself does
365     * not record the number; however, this is an illusion: the original writer
366     * of the PNG may have selected a lower window size, and we really must
367     * follow that because, for systems with with limited capabilities, we
368     * would otherwise reject the application's attempts to use a smaller window
369     * size (zlib doesn't have an interface to say "this or lower"!).
370     *
371     * inflateReset2 was added to zlib 1.2.4; before this the window could not be
372     * reset, therefore it is necessary to always allocate the maximum window
373     * size with earlier zlibs just in case later compressed chunks need it.
374     */
375    {
376       int ret; /* zlib return code */
377 #if ZLIB_VERNUM >= 0x1240
378       int window_bits = 0;
379 
380 # if defined(PNG_SET_OPTION_SUPPORTED) && defined(PNG_MAXIMUM_INFLATE_WINDOW)
381       if (((png_ptr->options >> PNG_MAXIMUM_INFLATE_WINDOW) & 3) ==
382           PNG_OPTION_ON)
383       {
384          window_bits = 15;
385          png_ptr->zstream_start = 0; /* fixed window size */
386       }
387 
388       else
389       {
390          png_ptr->zstream_start = 1;
391       }
392 # endif
393 
394 #endif /* ZLIB_VERNUM >= 0x1240 */
395 
396       /* Set this for safety, just in case the previous owner left pointers to
397        * memory allocations.
398        */
399       png_ptr->zstream.next_in = NULL;
400       png_ptr->zstream.avail_in = 0;
401       png_ptr->zstream.next_out = NULL;
402       png_ptr->zstream.avail_out = 0;
403 
404       if ((png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED) != 0)
405       {
406 #if ZLIB_VERNUM >= 0x1240
407          ret = inflateReset2(&png_ptr->zstream, window_bits);
408 #else
409          ret = inflateReset(&png_ptr->zstream);
410 #endif
411       }
412 
413       else
414       {
415 #if ZLIB_VERNUM >= 0x1240
416          ret = inflateInit2(&png_ptr->zstream, window_bits);
417 #else
418          ret = inflateInit(&png_ptr->zstream);
419 #endif
420 
421          if (ret == Z_OK)
422             png_ptr->flags |= PNG_FLAG_ZSTREAM_INITIALIZED;
423       }
424 
425 #if ZLIB_VERNUM >= 0x1290 && \
426    defined(PNG_SET_OPTION_SUPPORTED) && defined(PNG_IGNORE_ADLER32)
427       if (((png_ptr->options >> PNG_IGNORE_ADLER32) & 3) == PNG_OPTION_ON)
428          /* Turn off validation of the ADLER32 checksum in IDAT chunks */
429          ret = inflateValidate(&png_ptr->zstream, 0);
430 #endif
431 
432       if (ret == Z_OK)
433          png_ptr->zowner = owner;
434 
435       else
436          png_zstream_error(png_ptr, ret);
437 
438       return ret;
439    }
440 
441 #ifdef window_bits
442 # undef window_bits
443 #endif
444 }
445 
446 #if ZLIB_VERNUM >= 0x1240
447 /* Handle the start of the inflate stream if we called inflateInit2(strm,0);
448  * in this case some zlib versions skip validation of the CINFO field and, in
449  * certain circumstances, libpng may end up displaying an invalid image, in
450  * contrast to implementations that call zlib in the normal way (e.g. libpng
451  * 1.5).
452  */
453 int /* PRIVATE */
png_zlib_inflate(png_structrp png_ptr,int flush)454 png_zlib_inflate(png_structrp png_ptr, int flush)
455 {
456    if (png_ptr->zstream_start && png_ptr->zstream.avail_in > 0)
457    {
458       if ((*png_ptr->zstream.next_in >> 4) > 7)
459       {
460          png_ptr->zstream.msg = "invalid window size (libpng)";
461          return Z_DATA_ERROR;
462       }
463 
464       png_ptr->zstream_start = 0;
465    }
466 
467    return inflate(&png_ptr->zstream, flush);
468 }
469 #endif /* Zlib >= 1.2.4 */
470 
471 #ifdef PNG_READ_COMPRESSED_TEXT_SUPPORTED
472 #if defined(PNG_READ_zTXt_SUPPORTED) || defined (PNG_READ_iTXt_SUPPORTED)
473 /* png_inflate now returns zlib error codes including Z_OK and Z_STREAM_END to
474  * allow the caller to do multiple calls if required.  If the 'finish' flag is
475  * set Z_FINISH will be passed to the final inflate() call and Z_STREAM_END must
476  * be returned or there has been a problem, otherwise Z_SYNC_FLUSH is used and
477  * Z_OK or Z_STREAM_END will be returned on success.
478  *
479  * The input and output sizes are updated to the actual amounts of data consumed
480  * or written, not the amount available (as in a z_stream).  The data pointers
481  * are not changed, so the next input is (data+input_size) and the next
482  * available output is (output+output_size).
483  */
484 static int
png_inflate(png_structrp png_ptr,png_uint_32 owner,int finish,png_const_bytep input,png_uint_32p input_size_ptr,png_bytep output,png_alloc_size_t * output_size_ptr)485 png_inflate(png_structrp png_ptr, png_uint_32 owner, int finish,
486     /* INPUT: */ png_const_bytep input, png_uint_32p input_size_ptr,
487     /* OUTPUT: */ png_bytep output, png_alloc_size_t *output_size_ptr)
488 {
489    if (png_ptr->zowner == owner) /* Else not claimed */
490    {
491       int ret;
492       png_alloc_size_t avail_out = *output_size_ptr;
493       png_uint_32 avail_in = *input_size_ptr;
494 
495       /* zlib can't necessarily handle more than 65535 bytes at once (i.e. it
496        * can't even necessarily handle 65536 bytes) because the type uInt is
497        * "16 bits or more".  Consequently it is necessary to chunk the input to
498        * zlib.  This code uses ZLIB_IO_MAX, from pngpriv.h, as the maximum (the
499        * maximum value that can be stored in a uInt.)  It is possible to set
500        * ZLIB_IO_MAX to a lower value in pngpriv.h and this may sometimes have
501        * a performance advantage, because it reduces the amount of data accessed
502        * at each step and that may give the OS more time to page it in.
503        */
504       png_ptr->zstream.next_in = PNGZ_INPUT_CAST(input);
505       /* avail_in and avail_out are set below from 'size' */
506       png_ptr->zstream.avail_in = 0;
507       png_ptr->zstream.avail_out = 0;
508 
509       /* Read directly into the output if it is available (this is set to
510        * a local buffer below if output is NULL).
511        */
512       if (output != NULL)
513          png_ptr->zstream.next_out = output;
514 
515       do
516       {
517          uInt avail;
518          Byte local_buffer[PNG_INFLATE_BUF_SIZE];
519 
520          /* zlib INPUT BUFFER */
521          /* The setting of 'avail_in' used to be outside the loop; by setting it
522           * inside it is possible to chunk the input to zlib and simply rely on
523           * zlib to advance the 'next_in' pointer.  This allows arbitrary
524           * amounts of data to be passed through zlib at the unavoidable cost of
525           * requiring a window save (memcpy of up to 32768 output bytes)
526           * every ZLIB_IO_MAX input bytes.
527           */
528          avail_in += png_ptr->zstream.avail_in; /* not consumed last time */
529 
530          avail = ZLIB_IO_MAX;
531 
532          if (avail_in < avail)
533             avail = (uInt)avail_in; /* safe: < than ZLIB_IO_MAX */
534 
535          avail_in -= avail;
536          png_ptr->zstream.avail_in = avail;
537 
538          /* zlib OUTPUT BUFFER */
539          avail_out += png_ptr->zstream.avail_out; /* not written last time */
540 
541          avail = ZLIB_IO_MAX; /* maximum zlib can process */
542 
543          if (output == NULL)
544          {
545             /* Reset the output buffer each time round if output is NULL and
546              * make available the full buffer, up to 'remaining_space'
547              */
548             png_ptr->zstream.next_out = local_buffer;
549             if ((sizeof local_buffer) < avail)
550                avail = (sizeof local_buffer);
551          }
552 
553          if (avail_out < avail)
554             avail = (uInt)avail_out; /* safe: < ZLIB_IO_MAX */
555 
556          png_ptr->zstream.avail_out = avail;
557          avail_out -= avail;
558 
559          /* zlib inflate call */
560          /* In fact 'avail_out' may be 0 at this point, that happens at the end
561           * of the read when the final LZ end code was not passed at the end of
562           * the previous chunk of input data.  Tell zlib if we have reached the
563           * end of the output buffer.
564           */
565          ret = PNG_INFLATE(png_ptr, avail_out > 0 ? Z_NO_FLUSH :
566              (finish ? Z_FINISH : Z_SYNC_FLUSH));
567       } while (ret == Z_OK);
568 
569       /* For safety kill the local buffer pointer now */
570       if (output == NULL)
571          png_ptr->zstream.next_out = NULL;
572 
573       /* Claw back the 'size' and 'remaining_space' byte counts. */
574       avail_in += png_ptr->zstream.avail_in;
575       avail_out += png_ptr->zstream.avail_out;
576 
577       /* Update the input and output sizes; the updated values are the amount
578        * consumed or written, effectively the inverse of what zlib uses.
579        */
580       if (avail_out > 0)
581          *output_size_ptr -= avail_out;
582 
583       if (avail_in > 0)
584          *input_size_ptr -= avail_in;
585 
586       /* Ensure png_ptr->zstream.msg is set (even in the success case!) */
587       png_zstream_error(png_ptr, ret);
588       return ret;
589    }
590 
591    else
592    {
593       /* This is a bad internal error.  The recovery assigns to the zstream msg
594        * pointer, which is not owned by the caller, but this is safe; it's only
595        * used on errors!
596        */
597       png_ptr->zstream.msg = PNGZ_MSG_CAST("zstream unclaimed");
598       return Z_STREAM_ERROR;
599    }
600 }
601 
602 /*
603  * Decompress trailing data in a chunk.  The assumption is that read_buffer
604  * points at an allocated area holding the contents of a chunk with a
605  * trailing compressed part.  What we get back is an allocated area
606  * holding the original prefix part and an uncompressed version of the
607  * trailing part (the malloc area passed in is freed).
608  */
609 static int
png_decompress_chunk(png_structrp png_ptr,png_uint_32 chunklength,png_uint_32 prefix_size,png_alloc_size_t * newlength,int terminate)610 png_decompress_chunk(png_structrp png_ptr,
611     png_uint_32 chunklength, png_uint_32 prefix_size,
612     png_alloc_size_t *newlength /* must be initialized to the maximum! */,
613     int terminate /*add a '\0' to the end of the uncompressed data*/)
614 {
615    /* TODO: implement different limits for different types of chunk.
616     *
617     * The caller supplies *newlength set to the maximum length of the
618     * uncompressed data, but this routine allocates space for the prefix and
619     * maybe a '\0' terminator too.  We have to assume that 'prefix_size' is
620     * limited only by the maximum chunk size.
621     */
622    png_alloc_size_t limit = PNG_SIZE_MAX;
623 
624 # ifdef PNG_SET_USER_LIMITS_SUPPORTED
625    if (png_ptr->user_chunk_malloc_max > 0 &&
626        png_ptr->user_chunk_malloc_max < limit)
627       limit = png_ptr->user_chunk_malloc_max;
628 # elif PNG_USER_CHUNK_MALLOC_MAX > 0
629    if (PNG_USER_CHUNK_MALLOC_MAX < limit)
630       limit = PNG_USER_CHUNK_MALLOC_MAX;
631 # endif
632 
633    if (limit >= prefix_size + (terminate != 0))
634    {
635       int ret;
636 
637       limit -= prefix_size + (terminate != 0);
638 
639       if (limit < *newlength)
640          *newlength = limit;
641 
642       /* Now try to claim the stream. */
643       ret = png_inflate_claim(png_ptr, png_ptr->chunk_name);
644 
645       if (ret == Z_OK)
646       {
647          png_uint_32 lzsize = chunklength - prefix_size;
648 
649          ret = png_inflate(png_ptr, png_ptr->chunk_name, 1/*finish*/,
650              /* input: */ png_ptr->read_buffer + prefix_size, &lzsize,
651              /* output: */ NULL, newlength);
652 
653          if (ret == Z_STREAM_END)
654          {
655             /* Use 'inflateReset' here, not 'inflateReset2' because this
656              * preserves the previously decided window size (otherwise it would
657              * be necessary to store the previous window size.)  In practice
658              * this doesn't matter anyway, because png_inflate will call inflate
659              * with Z_FINISH in almost all cases, so the window will not be
660              * maintained.
661              */
662             if (inflateReset(&png_ptr->zstream) == Z_OK)
663             {
664                /* Because of the limit checks above we know that the new,
665                 * expanded, size will fit in a size_t (let alone an
666                 * png_alloc_size_t).  Use png_malloc_base here to avoid an
667                 * extra OOM message.
668                 */
669                png_alloc_size_t new_size = *newlength;
670                png_alloc_size_t buffer_size = prefix_size + new_size +
671                    (terminate != 0);
672                png_bytep text = png_voidcast(png_bytep, png_malloc_base(png_ptr,
673                    buffer_size));
674 
675                if (text != NULL)
676                {
677                   memset(text, 0, buffer_size);
678 
679                   ret = png_inflate(png_ptr, png_ptr->chunk_name, 1/*finish*/,
680                       png_ptr->read_buffer + prefix_size, &lzsize,
681                       text + prefix_size, newlength);
682 
683                   if (ret == Z_STREAM_END)
684                   {
685                      if (new_size == *newlength)
686                      {
687                         if (terminate != 0)
688                            text[prefix_size + *newlength] = 0;
689 
690                         if (prefix_size > 0)
691                            memcpy(text, png_ptr->read_buffer, prefix_size);
692 
693                         {
694                            png_bytep old_ptr = png_ptr->read_buffer;
695 
696                            png_ptr->read_buffer = text;
697                            png_ptr->read_buffer_size = buffer_size;
698                            text = old_ptr; /* freed below */
699                         }
700                      }
701 
702                      else
703                      {
704                         /* The size changed on the second read, there can be no
705                          * guarantee that anything is correct at this point.
706                          * The 'msg' pointer has been set to "unexpected end of
707                          * LZ stream", which is fine, but return an error code
708                          * that the caller won't accept.
709                          */
710                         ret = PNG_UNEXPECTED_ZLIB_RETURN;
711                      }
712                   }
713 
714                   else if (ret == Z_OK)
715                      ret = PNG_UNEXPECTED_ZLIB_RETURN; /* for safety */
716 
717                   /* Free the text pointer (this is the old read_buffer on
718                    * success)
719                    */
720                   png_free(png_ptr, text);
721 
722                   /* This really is very benign, but it's still an error because
723                    * the extra space may otherwise be used as a Trojan Horse.
724                    */
725                   if (ret == Z_STREAM_END &&
726                       chunklength - prefix_size != lzsize)
727                      png_chunk_benign_error(png_ptr, "extra compressed data");
728                }
729 
730                else
731                {
732                   /* Out of memory allocating the buffer */
733                   ret = Z_MEM_ERROR;
734                   png_zstream_error(png_ptr, Z_MEM_ERROR);
735                }
736             }
737 
738             else
739             {
740                /* inflateReset failed, store the error message */
741                png_zstream_error(png_ptr, ret);
742                ret = PNG_UNEXPECTED_ZLIB_RETURN;
743             }
744          }
745 
746          else if (ret == Z_OK)
747             ret = PNG_UNEXPECTED_ZLIB_RETURN;
748 
749          /* Release the claimed stream */
750          png_ptr->zowner = 0;
751       }
752 
753       else /* the claim failed */ if (ret == Z_STREAM_END) /* impossible! */
754          ret = PNG_UNEXPECTED_ZLIB_RETURN;
755 
756       return ret;
757    }
758 
759    else
760    {
761       /* Application/configuration limits exceeded */
762       png_zstream_error(png_ptr, Z_MEM_ERROR);
763       return Z_MEM_ERROR;
764    }
765 }
766 #endif /* READ_zTXt || READ_iTXt */
767 #endif /* READ_COMPRESSED_TEXT */
768 
769 #ifdef PNG_READ_iCCP_SUPPORTED
770 /* Perform a partial read and decompress, producing 'avail_out' bytes and
771  * reading from the current chunk as required.
772  */
773 static int
png_inflate_read(png_structrp png_ptr,png_bytep read_buffer,uInt read_size,png_uint_32p chunk_bytes,png_bytep next_out,png_alloc_size_t * out_size,int finish)774 png_inflate_read(png_structrp png_ptr, png_bytep read_buffer, uInt read_size,
775     png_uint_32p chunk_bytes, png_bytep next_out, png_alloc_size_t *out_size,
776     int finish)
777 {
778    if (png_ptr->zowner == png_ptr->chunk_name)
779    {
780       int ret;
781 
782       /* next_in and avail_in must have been initialized by the caller. */
783       png_ptr->zstream.next_out = next_out;
784       png_ptr->zstream.avail_out = 0; /* set in the loop */
785 
786       do
787       {
788          if (png_ptr->zstream.avail_in == 0)
789          {
790             if (read_size > *chunk_bytes)
791                read_size = (uInt)*chunk_bytes;
792             *chunk_bytes -= read_size;
793 
794             if (read_size > 0)
795                png_crc_read(png_ptr, read_buffer, read_size);
796 
797             png_ptr->zstream.next_in = read_buffer;
798             png_ptr->zstream.avail_in = read_size;
799          }
800 
801          if (png_ptr->zstream.avail_out == 0)
802          {
803             uInt avail = ZLIB_IO_MAX;
804             if (avail > *out_size)
805                avail = (uInt)*out_size;
806             *out_size -= avail;
807 
808             png_ptr->zstream.avail_out = avail;
809          }
810 
811          /* Use Z_SYNC_FLUSH when there is no more chunk data to ensure that all
812           * the available output is produced; this allows reading of truncated
813           * streams.
814           */
815          ret = PNG_INFLATE(png_ptr, *chunk_bytes > 0 ?
816              Z_NO_FLUSH : (finish ? Z_FINISH : Z_SYNC_FLUSH));
817       }
818       while (ret == Z_OK && (*out_size > 0 || png_ptr->zstream.avail_out > 0));
819 
820       *out_size += png_ptr->zstream.avail_out;
821       png_ptr->zstream.avail_out = 0; /* Should not be required, but is safe */
822 
823       /* Ensure the error message pointer is always set: */
824       png_zstream_error(png_ptr, ret);
825       return ret;
826    }
827 
828    else
829    {
830       png_ptr->zstream.msg = PNGZ_MSG_CAST("zstream unclaimed");
831       return Z_STREAM_ERROR;
832    }
833 }
834 #endif /* READ_iCCP */
835 
836 /* Read and check the IDHR chunk */
837 
838 void /* PRIVATE */
png_handle_IHDR(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)839 png_handle_IHDR(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
840 {
841    png_byte buf[13];
842    png_uint_32 width, height;
843    int bit_depth, color_type, compression_type, filter_type;
844    int interlace_type;
845 
846    png_debug(1, "in png_handle_IHDR");
847 
848    if ((png_ptr->mode & PNG_HAVE_IHDR) != 0)
849       png_chunk_error(png_ptr, "out of place");
850 
851    /* Check the length */
852    if (length != 13)
853       png_chunk_error(png_ptr, "invalid");
854 
855    png_ptr->mode |= PNG_HAVE_IHDR;
856 
857    png_crc_read(png_ptr, buf, 13);
858    png_crc_finish(png_ptr, 0);
859 
860    width = png_get_uint_31(png_ptr, buf);
861    height = png_get_uint_31(png_ptr, buf + 4);
862    bit_depth = buf[8];
863    color_type = buf[9];
864    compression_type = buf[10];
865    filter_type = buf[11];
866    interlace_type = buf[12];
867 
868    /* Set internal variables */
869    png_ptr->width = width;
870    png_ptr->height = height;
871    png_ptr->bit_depth = (png_byte)bit_depth;
872    png_ptr->interlaced = (png_byte)interlace_type;
873    png_ptr->color_type = (png_byte)color_type;
874 #ifdef PNG_MNG_FEATURES_SUPPORTED
875    png_ptr->filter_type = (png_byte)filter_type;
876 #endif
877    png_ptr->compression_type = (png_byte)compression_type;
878 
879    /* Find number of channels */
880    switch (png_ptr->color_type)
881    {
882       default: /* invalid, png_set_IHDR calls png_error */
883       case PNG_COLOR_TYPE_GRAY:
884       case PNG_COLOR_TYPE_PALETTE:
885          png_ptr->channels = 1;
886          break;
887 
888       case PNG_COLOR_TYPE_RGB:
889          png_ptr->channels = 3;
890          break;
891 
892       case PNG_COLOR_TYPE_GRAY_ALPHA:
893          png_ptr->channels = 2;
894          break;
895 
896       case PNG_COLOR_TYPE_RGB_ALPHA:
897          png_ptr->channels = 4;
898          break;
899    }
900 
901    /* Set up other useful info */
902    png_ptr->pixel_depth = (png_byte)(png_ptr->bit_depth * png_ptr->channels);
903    png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->width);
904    png_debug1(3, "bit_depth = %d", png_ptr->bit_depth);
905    png_debug1(3, "channels = %d", png_ptr->channels);
906    png_debug1(3, "rowbytes = %lu", (unsigned long)png_ptr->rowbytes);
907    png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth,
908        color_type, interlace_type, compression_type, filter_type);
909 }
910 
911 /* Read and check the palette */
912 void /* PRIVATE */
png_handle_PLTE(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)913 png_handle_PLTE(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
914 {
915    png_color palette[PNG_MAX_PALETTE_LENGTH];
916    int max_palette_length, num, i;
917 #ifdef PNG_POINTER_INDEXING_SUPPORTED
918    png_colorp pal_ptr;
919 #endif
920 
921    png_debug(1, "in png_handle_PLTE");
922 
923    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
924       png_chunk_error(png_ptr, "missing IHDR");
925 
926    /* Moved to before the 'after IDAT' check below because otherwise duplicate
927     * PLTE chunks are potentially ignored (the spec says there shall not be more
928     * than one PLTE, the error is not treated as benign, so this check trumps
929     * the requirement that PLTE appears before IDAT.)
930     */
931    else if ((png_ptr->mode & PNG_HAVE_PLTE) != 0)
932       png_chunk_error(png_ptr, "duplicate");
933 
934    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
935    {
936       /* This is benign because the non-benign error happened before, when an
937        * IDAT was encountered in a color-mapped image with no PLTE.
938        */
939       png_crc_finish(png_ptr, length);
940       png_chunk_benign_error(png_ptr, "out of place");
941       return;
942    }
943 
944    png_ptr->mode |= PNG_HAVE_PLTE;
945 
946    if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0)
947    {
948       png_crc_finish(png_ptr, length);
949       png_chunk_benign_error(png_ptr, "ignored in grayscale PNG");
950       return;
951    }
952 
953 #ifndef PNG_READ_OPT_PLTE_SUPPORTED
954    if (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
955    {
956       png_crc_finish(png_ptr, length);
957       return;
958    }
959 #endif
960 
961    if (length > 3*PNG_MAX_PALETTE_LENGTH || length % 3)
962    {
963       png_crc_finish(png_ptr, length);
964 
965       if (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
966          png_chunk_benign_error(png_ptr, "invalid");
967 
968       else
969          png_chunk_error(png_ptr, "invalid");
970 
971       return;
972    }
973 
974    /* The cast is safe because 'length' is less than 3*PNG_MAX_PALETTE_LENGTH */
975    num = (int)length / 3;
976 
977    /* If the palette has 256 or fewer entries but is too large for the bit
978     * depth, we don't issue an error, to preserve the behavior of previous
979     * libpng versions. We silently truncate the unused extra palette entries
980     * here.
981     */
982    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
983       max_palette_length = (1 << png_ptr->bit_depth);
984    else
985       max_palette_length = PNG_MAX_PALETTE_LENGTH;
986 
987    if (num > max_palette_length)
988       num = max_palette_length;
989 
990 #ifdef PNG_POINTER_INDEXING_SUPPORTED
991    for (i = 0, pal_ptr = palette; i < num; i++, pal_ptr++)
992    {
993       png_byte buf[3];
994 
995       png_crc_read(png_ptr, buf, 3);
996       pal_ptr->red = buf[0];
997       pal_ptr->green = buf[1];
998       pal_ptr->blue = buf[2];
999    }
1000 #else
1001    for (i = 0; i < num; i++)
1002    {
1003       png_byte buf[3];
1004 
1005       png_crc_read(png_ptr, buf, 3);
1006       /* Don't depend upon png_color being any order */
1007       palette[i].red = buf[0];
1008       palette[i].green = buf[1];
1009       palette[i].blue = buf[2];
1010    }
1011 #endif
1012 
1013    /* If we actually need the PLTE chunk (ie for a paletted image), we do
1014     * whatever the normal CRC configuration tells us.  However, if we
1015     * have an RGB image, the PLTE can be considered ancillary, so
1016     * we will act as though it is.
1017     */
1018 #ifndef PNG_READ_OPT_PLTE_SUPPORTED
1019    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1020 #endif
1021    {
1022       png_crc_finish(png_ptr, (png_uint_32) (length - (unsigned int)num * 3));
1023    }
1024 
1025 #ifndef PNG_READ_OPT_PLTE_SUPPORTED
1026    else if (png_crc_error(png_ptr) != 0)  /* Only if we have a CRC error */
1027    {
1028       /* If we don't want to use the data from an ancillary chunk,
1029        * we have two options: an error abort, or a warning and we
1030        * ignore the data in this chunk (which should be OK, since
1031        * it's considered ancillary for a RGB or RGBA image).
1032        *
1033        * IMPLEMENTATION NOTE: this is only here because png_crc_finish uses the
1034        * chunk type to determine whether to check the ancillary or the critical
1035        * flags.
1036        */
1037       if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_USE) == 0)
1038       {
1039          if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) != 0)
1040             return;
1041 
1042          else
1043             png_chunk_error(png_ptr, "CRC error");
1044       }
1045 
1046       /* Otherwise, we (optionally) emit a warning and use the chunk. */
1047       else if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) == 0)
1048          png_chunk_warning(png_ptr, "CRC error");
1049    }
1050 #endif
1051 
1052    /* TODO: png_set_PLTE has the side effect of setting png_ptr->palette to its
1053     * own copy of the palette.  This has the side effect that when png_start_row
1054     * is called (this happens after any call to png_read_update_info) the
1055     * info_ptr palette gets changed.  This is extremely unexpected and
1056     * confusing.
1057     *
1058     * Fix this by not sharing the palette in this way.
1059     */
1060    png_set_PLTE(png_ptr, info_ptr, palette, num);
1061 
1062    /* The three chunks, bKGD, hIST and tRNS *must* appear after PLTE and before
1063     * IDAT.  Prior to 1.6.0 this was not checked; instead the code merely
1064     * checked the apparent validity of a tRNS chunk inserted before PLTE on a
1065     * palette PNG.  1.6.0 attempts to rigorously follow the standard and
1066     * therefore does a benign error if the erroneous condition is detected *and*
1067     * cancels the tRNS if the benign error returns.  The alternative is to
1068     * amend the standard since it would be rather hypocritical of the standards
1069     * maintainers to ignore it.
1070     */
1071 #ifdef PNG_READ_tRNS_SUPPORTED
1072    if (png_ptr->num_trans > 0 ||
1073        (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tRNS) != 0))
1074    {
1075       /* Cancel this because otherwise it would be used if the transforms
1076        * require it.  Don't cancel the 'valid' flag because this would prevent
1077        * detection of duplicate chunks.
1078        */
1079       png_ptr->num_trans = 0;
1080 
1081       if (info_ptr != NULL)
1082          info_ptr->num_trans = 0;
1083 
1084       png_chunk_benign_error(png_ptr, "tRNS must be after");
1085    }
1086 #endif
1087 
1088 #ifdef PNG_READ_hIST_SUPPORTED
1089    if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_hIST) != 0)
1090       png_chunk_benign_error(png_ptr, "hIST must be after");
1091 #endif
1092 
1093 #ifdef PNG_READ_bKGD_SUPPORTED
1094    if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_bKGD) != 0)
1095       png_chunk_benign_error(png_ptr, "bKGD must be after");
1096 #endif
1097 }
1098 
1099 void /* PRIVATE */
png_handle_IEND(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)1100 png_handle_IEND(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1101 {
1102    png_debug(1, "in png_handle_IEND");
1103 
1104    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0 ||
1105        (png_ptr->mode & PNG_HAVE_IDAT) == 0)
1106       png_chunk_error(png_ptr, "out of place");
1107 
1108    png_ptr->mode |= (PNG_AFTER_IDAT | PNG_HAVE_IEND);
1109 
1110    png_crc_finish(png_ptr, length);
1111 
1112    if (length != 0)
1113       png_chunk_benign_error(png_ptr, "invalid");
1114 
1115    PNG_UNUSED(info_ptr)
1116 }
1117 
1118 #ifdef PNG_READ_gAMA_SUPPORTED
1119 void /* PRIVATE */
png_handle_gAMA(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)1120 png_handle_gAMA(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1121 {
1122    png_fixed_point igamma;
1123    png_byte buf[4];
1124 
1125    png_debug(1, "in png_handle_gAMA");
1126 
1127    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1128       png_chunk_error(png_ptr, "missing IHDR");
1129 
1130    else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
1131    {
1132       png_crc_finish(png_ptr, length);
1133       png_chunk_benign_error(png_ptr, "out of place");
1134       return;
1135    }
1136 
1137    if (length != 4)
1138    {
1139       png_crc_finish(png_ptr, length);
1140       png_chunk_benign_error(png_ptr, "invalid");
1141       return;
1142    }
1143 
1144    png_crc_read(png_ptr, buf, 4);
1145 
1146    if (png_crc_finish(png_ptr, 0) != 0)
1147       return;
1148 
1149    igamma = png_get_fixed_point(NULL, buf);
1150 
1151    png_colorspace_set_gamma(png_ptr, &png_ptr->colorspace, igamma);
1152    png_colorspace_sync(png_ptr, info_ptr);
1153 }
1154 #endif
1155 
1156 #ifdef PNG_READ_sBIT_SUPPORTED
1157 void /* PRIVATE */
png_handle_sBIT(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)1158 png_handle_sBIT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1159 {
1160    unsigned int truelen, i;
1161    png_byte sample_depth;
1162    png_byte buf[4];
1163 
1164    png_debug(1, "in png_handle_sBIT");
1165 
1166    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1167       png_chunk_error(png_ptr, "missing IHDR");
1168 
1169    else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
1170    {
1171       png_crc_finish(png_ptr, length);
1172       png_chunk_benign_error(png_ptr, "out of place");
1173       return;
1174    }
1175 
1176    if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sBIT) != 0)
1177    {
1178       png_crc_finish(png_ptr, length);
1179       png_chunk_benign_error(png_ptr, "duplicate");
1180       return;
1181    }
1182 
1183    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1184    {
1185       truelen = 3;
1186       sample_depth = 8;
1187    }
1188 
1189    else
1190    {
1191       truelen = png_ptr->channels;
1192       sample_depth = png_ptr->bit_depth;
1193    }
1194 
1195    if (length != truelen || length > 4)
1196    {
1197       png_chunk_benign_error(png_ptr, "invalid");
1198       png_crc_finish(png_ptr, length);
1199       return;
1200    }
1201 
1202    buf[0] = buf[1] = buf[2] = buf[3] = sample_depth;
1203    png_crc_read(png_ptr, buf, truelen);
1204 
1205    if (png_crc_finish(png_ptr, 0) != 0)
1206       return;
1207 
1208    for (i=0; i<truelen; ++i)
1209    {
1210       if (buf[i] == 0 || buf[i] > sample_depth)
1211       {
1212          png_chunk_benign_error(png_ptr, "invalid");
1213          return;
1214       }
1215    }
1216 
1217    if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1218    {
1219       png_ptr->sig_bit.red = buf[0];
1220       png_ptr->sig_bit.green = buf[1];
1221       png_ptr->sig_bit.blue = buf[2];
1222       png_ptr->sig_bit.alpha = buf[3];
1223    }
1224 
1225    else
1226    {
1227       png_ptr->sig_bit.gray = buf[0];
1228       png_ptr->sig_bit.red = buf[0];
1229       png_ptr->sig_bit.green = buf[0];
1230       png_ptr->sig_bit.blue = buf[0];
1231       png_ptr->sig_bit.alpha = buf[1];
1232    }
1233 
1234    png_set_sBIT(png_ptr, info_ptr, &(png_ptr->sig_bit));
1235 }
1236 #endif
1237 
1238 #ifdef PNG_READ_cHRM_SUPPORTED
1239 void /* PRIVATE */
png_handle_cHRM(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)1240 png_handle_cHRM(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1241 {
1242    png_byte buf[32];
1243    png_xy xy;
1244 
1245    png_debug(1, "in png_handle_cHRM");
1246 
1247    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1248       png_chunk_error(png_ptr, "missing IHDR");
1249 
1250    else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
1251    {
1252       png_crc_finish(png_ptr, length);
1253       png_chunk_benign_error(png_ptr, "out of place");
1254       return;
1255    }
1256 
1257    if (length != 32)
1258    {
1259       png_crc_finish(png_ptr, length);
1260       png_chunk_benign_error(png_ptr, "invalid");
1261       return;
1262    }
1263 
1264    png_crc_read(png_ptr, buf, 32);
1265 
1266    if (png_crc_finish(png_ptr, 0) != 0)
1267       return;
1268 
1269    xy.whitex = png_get_fixed_point(NULL, buf);
1270    xy.whitey = png_get_fixed_point(NULL, buf + 4);
1271    xy.redx   = png_get_fixed_point(NULL, buf + 8);
1272    xy.redy   = png_get_fixed_point(NULL, buf + 12);
1273    xy.greenx = png_get_fixed_point(NULL, buf + 16);
1274    xy.greeny = png_get_fixed_point(NULL, buf + 20);
1275    xy.bluex  = png_get_fixed_point(NULL, buf + 24);
1276    xy.bluey  = png_get_fixed_point(NULL, buf + 28);
1277 
1278    if (xy.whitex == PNG_FIXED_ERROR ||
1279        xy.whitey == PNG_FIXED_ERROR ||
1280        xy.redx   == PNG_FIXED_ERROR ||
1281        xy.redy   == PNG_FIXED_ERROR ||
1282        xy.greenx == PNG_FIXED_ERROR ||
1283        xy.greeny == PNG_FIXED_ERROR ||
1284        xy.bluex  == PNG_FIXED_ERROR ||
1285        xy.bluey  == PNG_FIXED_ERROR)
1286    {
1287       png_chunk_benign_error(png_ptr, "invalid values");
1288       return;
1289    }
1290 
1291    /* If a colorspace error has already been output skip this chunk */
1292    if ((png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
1293       return;
1294 
1295    if ((png_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) != 0)
1296    {
1297       png_ptr->colorspace.flags |= PNG_COLORSPACE_INVALID;
1298       png_colorspace_sync(png_ptr, info_ptr);
1299       png_chunk_benign_error(png_ptr, "duplicate");
1300       return;
1301    }
1302 
1303    png_ptr->colorspace.flags |= PNG_COLORSPACE_FROM_cHRM;
1304    (void)png_colorspace_set_chromaticities(png_ptr, &png_ptr->colorspace, &xy,
1305        1/*prefer cHRM values*/);
1306    png_colorspace_sync(png_ptr, info_ptr);
1307 }
1308 #endif
1309 
1310 #ifdef PNG_READ_sRGB_SUPPORTED
1311 void /* PRIVATE */
png_handle_sRGB(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)1312 png_handle_sRGB(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1313 {
1314    png_byte intent;
1315 
1316    png_debug(1, "in png_handle_sRGB");
1317 
1318    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1319       png_chunk_error(png_ptr, "missing IHDR");
1320 
1321    else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
1322    {
1323       png_crc_finish(png_ptr, length);
1324       png_chunk_benign_error(png_ptr, "out of place");
1325       return;
1326    }
1327 
1328    if (length != 1)
1329    {
1330       png_crc_finish(png_ptr, length);
1331       png_chunk_benign_error(png_ptr, "invalid");
1332       return;
1333    }
1334 
1335    png_crc_read(png_ptr, &intent, 1);
1336 
1337    if (png_crc_finish(png_ptr, 0) != 0)
1338       return;
1339 
1340    /* If a colorspace error has already been output skip this chunk */
1341    if ((png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
1342       return;
1343 
1344    /* Only one sRGB or iCCP chunk is allowed, use the HAVE_INTENT flag to detect
1345     * this.
1346     */
1347    if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_INTENT) != 0)
1348    {
1349       png_ptr->colorspace.flags |= PNG_COLORSPACE_INVALID;
1350       png_colorspace_sync(png_ptr, info_ptr);
1351       png_chunk_benign_error(png_ptr, "too many profiles");
1352       return;
1353    }
1354 
1355    (void)png_colorspace_set_sRGB(png_ptr, &png_ptr->colorspace, intent);
1356    png_colorspace_sync(png_ptr, info_ptr);
1357 }
1358 #endif /* READ_sRGB */
1359 
1360 #ifdef PNG_READ_iCCP_SUPPORTED
1361 void /* PRIVATE */
png_handle_iCCP(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)1362 png_handle_iCCP(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1363 /* Note: this does not properly handle profiles that are > 64K under DOS */
1364 {
1365    png_const_charp errmsg = NULL; /* error message output, or no error */
1366    int finished = 0; /* crc checked */
1367 
1368    png_debug(1, "in png_handle_iCCP");
1369 
1370    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1371       png_chunk_error(png_ptr, "missing IHDR");
1372 
1373    else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
1374    {
1375       png_crc_finish(png_ptr, length);
1376       png_chunk_benign_error(png_ptr, "out of place");
1377       return;
1378    }
1379 
1380    /* Consistent with all the above colorspace handling an obviously *invalid*
1381     * chunk is just ignored, so does not invalidate the color space.  An
1382     * alternative is to set the 'invalid' flags at the start of this routine
1383     * and only clear them in they were not set before and all the tests pass.
1384     */
1385 
1386    /* The keyword must be at least one character and there is a
1387     * terminator (0) byte and the compression method byte, and the
1388     * 'zlib' datastream is at least 11 bytes.
1389     */
1390    if (length < 14)
1391    {
1392       png_crc_finish(png_ptr, length);
1393       png_chunk_benign_error(png_ptr, "too short");
1394       return;
1395    }
1396 
1397    /* If a colorspace error has already been output skip this chunk */
1398    if ((png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
1399    {
1400       png_crc_finish(png_ptr, length);
1401       return;
1402    }
1403 
1404    /* Only one sRGB or iCCP chunk is allowed, use the HAVE_INTENT flag to detect
1405     * this.
1406     */
1407    if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_INTENT) == 0)
1408    {
1409       uInt read_length, keyword_length;
1410       char keyword[81];
1411 
1412       /* Find the keyword; the keyword plus separator and compression method
1413        * bytes can be at most 81 characters long.
1414        */
1415       read_length = 81; /* maximum */
1416       if (read_length > length)
1417          read_length = (uInt)length;
1418 
1419       png_crc_read(png_ptr, (png_bytep)keyword, read_length);
1420       length -= read_length;
1421 
1422       /* The minimum 'zlib' stream is assumed to be just the 2 byte header,
1423        * 5 bytes minimum 'deflate' stream, and the 4 byte checksum.
1424        */
1425       if (length < 11)
1426       {
1427          png_crc_finish(png_ptr, length);
1428          png_chunk_benign_error(png_ptr, "too short");
1429          return;
1430       }
1431 
1432       keyword_length = 0;
1433       while (keyword_length < 80 && keyword_length < read_length &&
1434          keyword[keyword_length] != 0)
1435          ++keyword_length;
1436 
1437       /* TODO: make the keyword checking common */
1438       if (keyword_length >= 1 && keyword_length <= 79)
1439       {
1440          /* We only understand '0' compression - deflate - so if we get a
1441           * different value we can't safely decode the chunk.
1442           */
1443          if (keyword_length+1 < read_length &&
1444             keyword[keyword_length+1] == PNG_COMPRESSION_TYPE_BASE)
1445          {
1446             read_length -= keyword_length+2;
1447 
1448             if (png_inflate_claim(png_ptr, png_iCCP) == Z_OK)
1449             {
1450                Byte profile_header[132]={0};
1451                Byte local_buffer[PNG_INFLATE_BUF_SIZE];
1452                png_alloc_size_t size = (sizeof profile_header);
1453 
1454                png_ptr->zstream.next_in = (Bytef*)keyword + (keyword_length+2);
1455                png_ptr->zstream.avail_in = read_length;
1456                (void)png_inflate_read(png_ptr, local_buffer,
1457                    (sizeof local_buffer), &length, profile_header, &size,
1458                    0/*finish: don't, because the output is too small*/);
1459 
1460                if (size == 0)
1461                {
1462                   /* We have the ICC profile header; do the basic header checks.
1463                    */
1464                   const png_uint_32 profile_length =
1465                      png_get_uint_32(profile_header);
1466 
1467                   if (png_icc_check_length(png_ptr, &png_ptr->colorspace,
1468                       keyword, profile_length) != 0)
1469                   {
1470                      /* The length is apparently ok, so we can check the 132
1471                       * byte header.
1472                       */
1473                      if (png_icc_check_header(png_ptr, &png_ptr->colorspace,
1474                          keyword, profile_length, profile_header,
1475                          png_ptr->color_type) != 0)
1476                      {
1477                         /* Now read the tag table; a variable size buffer is
1478                          * needed at this point, allocate one for the whole
1479                          * profile.  The header check has already validated
1480                          * that none of this stuff will overflow.
1481                          */
1482                         const png_uint_32 tag_count = png_get_uint_32(
1483                             profile_header+128);
1484                         png_bytep profile = png_read_buffer(png_ptr,
1485                             profile_length, 2/*silent*/);
1486 
1487                         if (profile != NULL)
1488                         {
1489                            memcpy(profile, profile_header,
1490                                (sizeof profile_header));
1491 
1492                            size = 12 * tag_count;
1493 
1494                            (void)png_inflate_read(png_ptr, local_buffer,
1495                                (sizeof local_buffer), &length,
1496                                profile + (sizeof profile_header), &size, 0);
1497 
1498                            /* Still expect a buffer error because we expect
1499                             * there to be some tag data!
1500                             */
1501                            if (size == 0)
1502                            {
1503                               if (png_icc_check_tag_table(png_ptr,
1504                                   &png_ptr->colorspace, keyword, profile_length,
1505                                   profile) != 0)
1506                               {
1507                                  /* The profile has been validated for basic
1508                                   * security issues, so read the whole thing in.
1509                                   */
1510                                  size = profile_length - (sizeof profile_header)
1511                                      - 12 * tag_count;
1512 
1513                                  (void)png_inflate_read(png_ptr, local_buffer,
1514                                      (sizeof local_buffer), &length,
1515                                      profile + (sizeof profile_header) +
1516                                      12 * tag_count, &size, 1/*finish*/);
1517 
1518                                  if (length > 0 && !(png_ptr->flags &
1519                                      PNG_FLAG_BENIGN_ERRORS_WARN))
1520                                     errmsg = "extra compressed data";
1521 
1522                                  /* But otherwise allow extra data: */
1523                                  else if (size == 0)
1524                                  {
1525                                     if (length > 0)
1526                                     {
1527                                        /* This can be handled completely, so
1528                                         * keep going.
1529                                         */
1530                                        png_chunk_warning(png_ptr,
1531                                            "extra compressed data");
1532                                     }
1533 
1534                                     png_crc_finish(png_ptr, length);
1535                                     finished = 1;
1536 
1537 # if defined(PNG_sRGB_SUPPORTED) && PNG_sRGB_PROFILE_CHECKS >= 0
1538                                     /* Check for a match against sRGB */
1539                                     png_icc_set_sRGB(png_ptr,
1540                                         &png_ptr->colorspace, profile,
1541                                         png_ptr->zstream.adler);
1542 # endif
1543 
1544                                     /* Steal the profile for info_ptr. */
1545                                     if (info_ptr != NULL)
1546                                     {
1547                                        png_free_data(png_ptr, info_ptr,
1548                                            PNG_FREE_ICCP, 0);
1549 
1550                                        info_ptr->iccp_name = png_voidcast(char*,
1551                                            png_malloc_base(png_ptr,
1552                                            keyword_length+1));
1553                                        if (info_ptr->iccp_name != NULL)
1554                                        {
1555                                           memcpy(info_ptr->iccp_name, keyword,
1556                                               keyword_length+1);
1557                                           info_ptr->iccp_proflen =
1558                                               profile_length;
1559                                           info_ptr->iccp_profile = profile;
1560                                           png_ptr->read_buffer = NULL; /*steal*/
1561                                           info_ptr->free_me |= PNG_FREE_ICCP;
1562                                           info_ptr->valid |= PNG_INFO_iCCP;
1563                                        }
1564 
1565                                        else
1566                                        {
1567                                           png_ptr->colorspace.flags |=
1568                                              PNG_COLORSPACE_INVALID;
1569                                           errmsg = "out of memory";
1570                                        }
1571                                     }
1572 
1573                                     /* else the profile remains in the read
1574                                      * buffer which gets reused for subsequent
1575                                      * chunks.
1576                                      */
1577 
1578                                     if (info_ptr != NULL)
1579                                        png_colorspace_sync(png_ptr, info_ptr);
1580 
1581                                     if (errmsg == NULL)
1582                                     {
1583                                        png_ptr->zowner = 0;
1584                                        return;
1585                                     }
1586                                  }
1587                                  if (errmsg == NULL)
1588                                     errmsg = png_ptr->zstream.msg;
1589                               }
1590                               /* else png_icc_check_tag_table output an error */
1591                            }
1592                            else /* profile truncated */
1593                               errmsg = png_ptr->zstream.msg;
1594                         }
1595 
1596                         else
1597                            errmsg = "out of memory";
1598                      }
1599 
1600                      /* else png_icc_check_header output an error */
1601                   }
1602 
1603                   /* else png_icc_check_length output an error */
1604                }
1605 
1606                else /* profile truncated */
1607                   errmsg = png_ptr->zstream.msg;
1608 
1609                /* Release the stream */
1610                png_ptr->zowner = 0;
1611             }
1612 
1613             else /* png_inflate_claim failed */
1614                errmsg = png_ptr->zstream.msg;
1615          }
1616 
1617          else
1618             errmsg = "bad compression method"; /* or missing */
1619       }
1620 
1621       else
1622          errmsg = "bad keyword";
1623    }
1624 
1625    else
1626       errmsg = "too many profiles";
1627 
1628    /* Failure: the reason is in 'errmsg' */
1629    if (finished == 0)
1630       png_crc_finish(png_ptr, length);
1631 
1632    png_ptr->colorspace.flags |= PNG_COLORSPACE_INVALID;
1633    png_colorspace_sync(png_ptr, info_ptr);
1634    if (errmsg != NULL) /* else already output */
1635       png_chunk_benign_error(png_ptr, errmsg);
1636 }
1637 #endif /* READ_iCCP */
1638 
1639 #ifdef PNG_READ_sPLT_SUPPORTED
1640 void /* PRIVATE */
png_handle_sPLT(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)1641 png_handle_sPLT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1642 /* Note: this does not properly handle chunks that are > 64K under DOS */
1643 {
1644    png_bytep entry_start, buffer;
1645    png_sPLT_t new_palette;
1646    png_sPLT_entryp pp;
1647    png_uint_32 data_length;
1648    int entry_size, i;
1649    png_uint_32 skip = 0;
1650    png_uint_32 dl;
1651    size_t max_dl;
1652 
1653    png_debug(1, "in png_handle_sPLT");
1654 
1655 #ifdef PNG_USER_LIMITS_SUPPORTED
1656    if (png_ptr->user_chunk_cache_max != 0)
1657    {
1658       if (png_ptr->user_chunk_cache_max == 1)
1659       {
1660          png_crc_finish(png_ptr, length);
1661          return;
1662       }
1663 
1664       if (--png_ptr->user_chunk_cache_max == 1)
1665       {
1666          png_warning(png_ptr, "No space in chunk cache for sPLT");
1667          png_crc_finish(png_ptr, length);
1668          return;
1669       }
1670    }
1671 #endif
1672 
1673    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1674       png_chunk_error(png_ptr, "missing IHDR");
1675 
1676    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
1677    {
1678       png_crc_finish(png_ptr, length);
1679       png_chunk_benign_error(png_ptr, "out of place");
1680       return;
1681    }
1682 
1683 #ifdef PNG_MAX_MALLOC_64K
1684    if (length > 65535U)
1685    {
1686       png_crc_finish(png_ptr, length);
1687       png_chunk_benign_error(png_ptr, "too large to fit in memory");
1688       return;
1689    }
1690 #endif
1691 
1692    buffer = png_read_buffer(png_ptr, length+1, 2/*silent*/);
1693    if (buffer == NULL)
1694    {
1695       png_crc_finish(png_ptr, length);
1696       png_chunk_benign_error(png_ptr, "out of memory");
1697       return;
1698    }
1699 
1700 
1701    /* WARNING: this may break if size_t is less than 32 bits; it is assumed
1702     * that the PNG_MAX_MALLOC_64K test is enabled in this case, but this is a
1703     * potential breakage point if the types in pngconf.h aren't exactly right.
1704     */
1705    png_crc_read(png_ptr, buffer, length);
1706 
1707    if (png_crc_finish(png_ptr, skip) != 0)
1708       return;
1709 
1710    buffer[length] = 0;
1711 
1712    for (entry_start = buffer; *entry_start; entry_start++)
1713       /* Empty loop to find end of name */ ;
1714 
1715    ++entry_start;
1716 
1717    /* A sample depth should follow the separator, and we should be on it  */
1718    if (length < 2U || entry_start > buffer + (length - 2U))
1719    {
1720       png_warning(png_ptr, "malformed sPLT chunk");
1721       return;
1722    }
1723 
1724    new_palette.depth = *entry_start++;
1725    entry_size = (new_palette.depth == 8 ? 6 : 10);
1726    /* This must fit in a png_uint_32 because it is derived from the original
1727     * chunk data length.
1728     */
1729    data_length = length - (png_uint_32)(entry_start - buffer);
1730 
1731    /* Integrity-check the data length */
1732    if ((data_length % (unsigned int)entry_size) != 0)
1733    {
1734       png_warning(png_ptr, "sPLT chunk has bad length");
1735       return;
1736    }
1737 
1738    dl = (png_uint_32)(data_length / (unsigned int)entry_size);
1739    max_dl = PNG_SIZE_MAX / (sizeof (png_sPLT_entry));
1740 
1741    if (dl > max_dl)
1742    {
1743       png_warning(png_ptr, "sPLT chunk too long");
1744       return;
1745    }
1746 
1747    new_palette.nentries = (png_int_32)(data_length / (unsigned int)entry_size);
1748 
1749    new_palette.entries = (png_sPLT_entryp)png_malloc_warn(png_ptr,
1750        (png_alloc_size_t) new_palette.nentries * (sizeof (png_sPLT_entry)));
1751 
1752    if (new_palette.entries == NULL)
1753    {
1754       png_warning(png_ptr, "sPLT chunk requires too much memory");
1755       return;
1756    }
1757 
1758 #ifdef PNG_POINTER_INDEXING_SUPPORTED
1759    for (i = 0; i < new_palette.nentries; i++)
1760    {
1761       pp = new_palette.entries + i;
1762 
1763       if (new_palette.depth == 8)
1764       {
1765          pp->red = *entry_start++;
1766          pp->green = *entry_start++;
1767          pp->blue = *entry_start++;
1768          pp->alpha = *entry_start++;
1769       }
1770 
1771       else
1772       {
1773          pp->red   = png_get_uint_16(entry_start); entry_start += 2;
1774          pp->green = png_get_uint_16(entry_start); entry_start += 2;
1775          pp->blue  = png_get_uint_16(entry_start); entry_start += 2;
1776          pp->alpha = png_get_uint_16(entry_start); entry_start += 2;
1777       }
1778 
1779       pp->frequency = png_get_uint_16(entry_start); entry_start += 2;
1780    }
1781 #else
1782    pp = new_palette.entries;
1783 
1784    for (i = 0; i < new_palette.nentries; i++)
1785    {
1786 
1787       if (new_palette.depth == 8)
1788       {
1789          pp[i].red   = *entry_start++;
1790          pp[i].green = *entry_start++;
1791          pp[i].blue  = *entry_start++;
1792          pp[i].alpha = *entry_start++;
1793       }
1794 
1795       else
1796       {
1797          pp[i].red   = png_get_uint_16(entry_start); entry_start += 2;
1798          pp[i].green = png_get_uint_16(entry_start); entry_start += 2;
1799          pp[i].blue  = png_get_uint_16(entry_start); entry_start += 2;
1800          pp[i].alpha = png_get_uint_16(entry_start); entry_start += 2;
1801       }
1802 
1803       pp[i].frequency = png_get_uint_16(entry_start); entry_start += 2;
1804    }
1805 #endif
1806 
1807    /* Discard all chunk data except the name and stash that */
1808    new_palette.name = (png_charp)buffer;
1809 
1810    png_set_sPLT(png_ptr, info_ptr, &new_palette, 1);
1811 
1812    png_free(png_ptr, new_palette.entries);
1813 }
1814 #endif /* READ_sPLT */
1815 
1816 #ifdef PNG_READ_tRNS_SUPPORTED
1817 void /* PRIVATE */
png_handle_tRNS(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)1818 png_handle_tRNS(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1819 {
1820    png_byte readbuf[PNG_MAX_PALETTE_LENGTH];
1821 
1822    png_debug(1, "in png_handle_tRNS");
1823 
1824    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1825       png_chunk_error(png_ptr, "missing IHDR");
1826 
1827    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
1828    {
1829       png_crc_finish(png_ptr, length);
1830       png_chunk_benign_error(png_ptr, "out of place");
1831       return;
1832    }
1833 
1834    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tRNS) != 0)
1835    {
1836       png_crc_finish(png_ptr, length);
1837       png_chunk_benign_error(png_ptr, "duplicate");
1838       return;
1839    }
1840 
1841    if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
1842    {
1843       png_byte buf[2];
1844 
1845       if (length != 2)
1846       {
1847          png_crc_finish(png_ptr, length);
1848          png_chunk_benign_error(png_ptr, "invalid");
1849          return;
1850       }
1851 
1852       png_crc_read(png_ptr, buf, 2);
1853       png_ptr->num_trans = 1;
1854       png_ptr->trans_color.gray = png_get_uint_16(buf);
1855    }
1856 
1857    else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
1858    {
1859       png_byte buf[6];
1860 
1861       if (length != 6)
1862       {
1863          png_crc_finish(png_ptr, length);
1864          png_chunk_benign_error(png_ptr, "invalid");
1865          return;
1866       }
1867 
1868       png_crc_read(png_ptr, buf, length);
1869       png_ptr->num_trans = 1;
1870       png_ptr->trans_color.red = png_get_uint_16(buf);
1871       png_ptr->trans_color.green = png_get_uint_16(buf + 2);
1872       png_ptr->trans_color.blue = png_get_uint_16(buf + 4);
1873    }
1874 
1875    else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1876    {
1877       if ((png_ptr->mode & PNG_HAVE_PLTE) == 0)
1878       {
1879          /* TODO: is this actually an error in the ISO spec? */
1880          png_crc_finish(png_ptr, length);
1881          png_chunk_benign_error(png_ptr, "out of place");
1882          return;
1883       }
1884 
1885       if (length > (unsigned int) png_ptr->num_palette ||
1886          length > (unsigned int) PNG_MAX_PALETTE_LENGTH ||
1887          length == 0)
1888       {
1889          png_crc_finish(png_ptr, length);
1890          png_chunk_benign_error(png_ptr, "invalid");
1891          return;
1892       }
1893 
1894       png_crc_read(png_ptr, readbuf, length);
1895       png_ptr->num_trans = (png_uint_16)length;
1896    }
1897 
1898    else
1899    {
1900       png_crc_finish(png_ptr, length);
1901       png_chunk_benign_error(png_ptr, "invalid with alpha channel");
1902       return;
1903    }
1904 
1905    if (png_crc_finish(png_ptr, 0) != 0)
1906    {
1907       png_ptr->num_trans = 0;
1908       return;
1909    }
1910 
1911    /* TODO: this is a horrible side effect in the palette case because the
1912     * png_struct ends up with a pointer to the tRNS buffer owned by the
1913     * png_info.  Fix this.
1914     */
1915    png_set_tRNS(png_ptr, info_ptr, readbuf, png_ptr->num_trans,
1916        &(png_ptr->trans_color));
1917 }
1918 #endif
1919 
1920 #ifdef PNG_READ_bKGD_SUPPORTED
1921 void /* PRIVATE */
png_handle_bKGD(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)1922 png_handle_bKGD(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1923 {
1924    unsigned int truelen;
1925    png_byte buf[6];
1926    png_color_16 background;
1927 
1928    png_debug(1, "in png_handle_bKGD");
1929 
1930    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1931       png_chunk_error(png_ptr, "missing IHDR");
1932 
1933    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0 ||
1934        (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
1935        (png_ptr->mode & PNG_HAVE_PLTE) == 0))
1936    {
1937       png_crc_finish(png_ptr, length);
1938       png_chunk_benign_error(png_ptr, "out of place");
1939       return;
1940    }
1941 
1942    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_bKGD) != 0)
1943    {
1944       png_crc_finish(png_ptr, length);
1945       png_chunk_benign_error(png_ptr, "duplicate");
1946       return;
1947    }
1948 
1949    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1950       truelen = 1;
1951 
1952    else if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1953       truelen = 6;
1954 
1955    else
1956       truelen = 2;
1957 
1958    if (length != truelen)
1959    {
1960       png_crc_finish(png_ptr, length);
1961       png_chunk_benign_error(png_ptr, "invalid");
1962       return;
1963    }
1964 
1965    png_crc_read(png_ptr, buf, truelen);
1966 
1967    if (png_crc_finish(png_ptr, 0) != 0)
1968       return;
1969 
1970    /* We convert the index value into RGB components so that we can allow
1971     * arbitrary RGB values for background when we have transparency, and
1972     * so it is easy to determine the RGB values of the background color
1973     * from the info_ptr struct.
1974     */
1975    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1976    {
1977       background.index = buf[0];
1978 
1979       if (info_ptr != NULL && info_ptr->num_palette != 0)
1980       {
1981          if (buf[0] >= info_ptr->num_palette)
1982          {
1983             png_chunk_benign_error(png_ptr, "invalid index");
1984             return;
1985          }
1986 
1987          background.red = (png_uint_16)png_ptr->palette[buf[0]].red;
1988          background.green = (png_uint_16)png_ptr->palette[buf[0]].green;
1989          background.blue = (png_uint_16)png_ptr->palette[buf[0]].blue;
1990       }
1991 
1992       else
1993          background.red = background.green = background.blue = 0;
1994 
1995       background.gray = 0;
1996    }
1997 
1998    else if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0) /* GRAY */
1999    {
2000       if (png_ptr->bit_depth <= 8)
2001       {
2002          if (buf[0] != 0 || buf[1] >= (unsigned int)(1 << png_ptr->bit_depth))
2003          {
2004             png_chunk_benign_error(png_ptr, "invalid gray level");
2005             return;
2006          }
2007       }
2008 
2009       background.index = 0;
2010       background.red =
2011       background.green =
2012       background.blue =
2013       background.gray = png_get_uint_16(buf);
2014    }
2015 
2016    else
2017    {
2018       if (png_ptr->bit_depth <= 8)
2019       {
2020          if (buf[0] != 0 || buf[2] != 0 || buf[4] != 0)
2021          {
2022             png_chunk_benign_error(png_ptr, "invalid color");
2023             return;
2024          }
2025       }
2026 
2027       background.index = 0;
2028       background.red = png_get_uint_16(buf);
2029       background.green = png_get_uint_16(buf + 2);
2030       background.blue = png_get_uint_16(buf + 4);
2031       background.gray = 0;
2032    }
2033 
2034    png_set_bKGD(png_ptr, info_ptr, &background);
2035 }
2036 #endif
2037 
2038 #ifdef PNG_READ_eXIf_SUPPORTED
2039 void /* PRIVATE */
png_handle_eXIf(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)2040 png_handle_eXIf(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2041 {
2042    unsigned int i;
2043 
2044    png_debug(1, "in png_handle_eXIf");
2045 
2046    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2047       png_chunk_error(png_ptr, "missing IHDR");
2048 
2049    if (length < 2)
2050    {
2051       png_crc_finish(png_ptr, length);
2052       png_chunk_benign_error(png_ptr, "too short");
2053       return;
2054    }
2055 
2056    else if (info_ptr == NULL || (info_ptr->valid & PNG_INFO_eXIf) != 0)
2057    {
2058       png_crc_finish(png_ptr, length);
2059       png_chunk_benign_error(png_ptr, "duplicate");
2060       return;
2061    }
2062 
2063    info_ptr->free_me |= PNG_FREE_EXIF;
2064 
2065    info_ptr->eXIf_buf = png_voidcast(png_bytep,
2066              png_malloc_warn(png_ptr, length));
2067 
2068    if (info_ptr->eXIf_buf == NULL)
2069    {
2070       png_crc_finish(png_ptr, length);
2071       png_chunk_benign_error(png_ptr, "out of memory");
2072       return;
2073    }
2074 
2075    for (i = 0; i < length; i++)
2076    {
2077       png_byte buf[1];
2078       png_crc_read(png_ptr, buf, 1);
2079       info_ptr->eXIf_buf[i] = buf[0];
2080       if (i == 1 && buf[0] != 'M' && buf[0] != 'I'
2081                  && info_ptr->eXIf_buf[0] != buf[0])
2082       {
2083          png_crc_finish(png_ptr, length);
2084          png_chunk_benign_error(png_ptr, "incorrect byte-order specifier");
2085          png_free(png_ptr, info_ptr->eXIf_buf);
2086          info_ptr->eXIf_buf = NULL;
2087          return;
2088       }
2089    }
2090 
2091    if (png_crc_finish(png_ptr, 0) != 0)
2092       return;
2093 
2094    png_set_eXIf_1(png_ptr, info_ptr, length, info_ptr->eXIf_buf);
2095 
2096    png_free(png_ptr, info_ptr->eXIf_buf);
2097    info_ptr->eXIf_buf = NULL;
2098 }
2099 #endif
2100 
2101 #ifdef PNG_READ_hIST_SUPPORTED
2102 void /* PRIVATE */
png_handle_hIST(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)2103 png_handle_hIST(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2104 {
2105    unsigned int num, i;
2106    png_uint_16 readbuf[PNG_MAX_PALETTE_LENGTH];
2107 
2108    png_debug(1, "in png_handle_hIST");
2109 
2110    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2111       png_chunk_error(png_ptr, "missing IHDR");
2112 
2113    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0 ||
2114        (png_ptr->mode & PNG_HAVE_PLTE) == 0)
2115    {
2116       png_crc_finish(png_ptr, length);
2117       png_chunk_benign_error(png_ptr, "out of place");
2118       return;
2119    }
2120 
2121    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_hIST) != 0)
2122    {
2123       png_crc_finish(png_ptr, length);
2124       png_chunk_benign_error(png_ptr, "duplicate");
2125       return;
2126    }
2127 
2128    num = length / 2 ;
2129 
2130    if (num != (unsigned int) png_ptr->num_palette ||
2131        num > (unsigned int) PNG_MAX_PALETTE_LENGTH)
2132    {
2133       png_crc_finish(png_ptr, length);
2134       png_chunk_benign_error(png_ptr, "invalid");
2135       return;
2136    }
2137 
2138    for (i = 0; i < num; i++)
2139    {
2140       png_byte buf[2];
2141 
2142       png_crc_read(png_ptr, buf, 2);
2143       readbuf[i] = png_get_uint_16(buf);
2144    }
2145 
2146    if (png_crc_finish(png_ptr, 0) != 0)
2147       return;
2148 
2149    png_set_hIST(png_ptr, info_ptr, readbuf);
2150 }
2151 #endif
2152 
2153 #ifdef PNG_READ_pHYs_SUPPORTED
2154 void /* PRIVATE */
png_handle_pHYs(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)2155 png_handle_pHYs(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2156 {
2157    png_byte buf[9];
2158    png_uint_32 res_x, res_y;
2159    int unit_type;
2160 
2161    png_debug(1, "in png_handle_pHYs");
2162 
2163    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2164       png_chunk_error(png_ptr, "missing IHDR");
2165 
2166    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2167    {
2168       png_crc_finish(png_ptr, length);
2169       png_chunk_benign_error(png_ptr, "out of place");
2170       return;
2171    }
2172 
2173    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_pHYs) != 0)
2174    {
2175       png_crc_finish(png_ptr, length);
2176       png_chunk_benign_error(png_ptr, "duplicate");
2177       return;
2178    }
2179 
2180    if (length != 9)
2181    {
2182       png_crc_finish(png_ptr, length);
2183       png_chunk_benign_error(png_ptr, "invalid");
2184       return;
2185    }
2186 
2187    png_crc_read(png_ptr, buf, 9);
2188 
2189    if (png_crc_finish(png_ptr, 0) != 0)
2190       return;
2191 
2192    res_x = png_get_uint_32(buf);
2193    res_y = png_get_uint_32(buf + 4);
2194    unit_type = buf[8];
2195    png_set_pHYs(png_ptr, info_ptr, res_x, res_y, unit_type);
2196 }
2197 #endif
2198 
2199 #ifdef PNG_READ_oFFs_SUPPORTED
2200 void /* PRIVATE */
png_handle_oFFs(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)2201 png_handle_oFFs(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2202 {
2203    png_byte buf[9];
2204    png_int_32 offset_x, offset_y;
2205    int unit_type;
2206 
2207    png_debug(1, "in png_handle_oFFs");
2208 
2209    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2210       png_chunk_error(png_ptr, "missing IHDR");
2211 
2212    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2213    {
2214       png_crc_finish(png_ptr, length);
2215       png_chunk_benign_error(png_ptr, "out of place");
2216       return;
2217    }
2218 
2219    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_oFFs) != 0)
2220    {
2221       png_crc_finish(png_ptr, length);
2222       png_chunk_benign_error(png_ptr, "duplicate");
2223       return;
2224    }
2225 
2226    if (length != 9)
2227    {
2228       png_crc_finish(png_ptr, length);
2229       png_chunk_benign_error(png_ptr, "invalid");
2230       return;
2231    }
2232 
2233    png_crc_read(png_ptr, buf, 9);
2234 
2235    if (png_crc_finish(png_ptr, 0) != 0)
2236       return;
2237 
2238    offset_x = png_get_int_32(buf);
2239    offset_y = png_get_int_32(buf + 4);
2240    unit_type = buf[8];
2241    png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y, unit_type);
2242 }
2243 #endif
2244 
2245 #ifdef PNG_READ_pCAL_SUPPORTED
2246 /* Read the pCAL chunk (described in the PNG Extensions document) */
2247 void /* PRIVATE */
png_handle_pCAL(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)2248 png_handle_pCAL(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2249 {
2250    png_int_32 X0, X1;
2251    png_byte type, nparams;
2252    png_bytep buffer, buf, units, endptr;
2253    png_charpp params;
2254    int i;
2255 
2256    png_debug(1, "in png_handle_pCAL");
2257 
2258    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2259       png_chunk_error(png_ptr, "missing IHDR");
2260 
2261    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2262    {
2263       png_crc_finish(png_ptr, length);
2264       png_chunk_benign_error(png_ptr, "out of place");
2265       return;
2266    }
2267 
2268    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_pCAL) != 0)
2269    {
2270       png_crc_finish(png_ptr, length);
2271       png_chunk_benign_error(png_ptr, "duplicate");
2272       return;
2273    }
2274 
2275    png_debug1(2, "Allocating and reading pCAL chunk data (%u bytes)",
2276        length + 1);
2277 
2278    buffer = png_read_buffer(png_ptr, length+1, 2/*silent*/);
2279 
2280    if (buffer == NULL)
2281    {
2282       png_crc_finish(png_ptr, length);
2283       png_chunk_benign_error(png_ptr, "out of memory");
2284       return;
2285    }
2286 
2287    png_crc_read(png_ptr, buffer, length);
2288 
2289    if (png_crc_finish(png_ptr, 0) != 0)
2290       return;
2291 
2292    buffer[length] = 0; /* Null terminate the last string */
2293 
2294    png_debug(3, "Finding end of pCAL purpose string");
2295    for (buf = buffer; *buf; buf++)
2296       /* Empty loop */ ;
2297 
2298    endptr = buffer + length;
2299 
2300    /* We need to have at least 12 bytes after the purpose string
2301     * in order to get the parameter information.
2302     */
2303    if (endptr - buf <= 12)
2304    {
2305       png_chunk_benign_error(png_ptr, "invalid");
2306       return;
2307    }
2308 
2309    png_debug(3, "Reading pCAL X0, X1, type, nparams, and units");
2310    X0 = png_get_int_32((png_bytep)buf+1);
2311    X1 = png_get_int_32((png_bytep)buf+5);
2312    type = buf[9];
2313    nparams = buf[10];
2314    units = buf + 11;
2315 
2316    png_debug(3, "Checking pCAL equation type and number of parameters");
2317    /* Check that we have the right number of parameters for known
2318     * equation types.
2319     */
2320    if ((type == PNG_EQUATION_LINEAR && nparams != 2) ||
2321        (type == PNG_EQUATION_BASE_E && nparams != 3) ||
2322        (type == PNG_EQUATION_ARBITRARY && nparams != 3) ||
2323        (type == PNG_EQUATION_HYPERBOLIC && nparams != 4))
2324    {
2325       png_chunk_benign_error(png_ptr, "invalid parameter count");
2326       return;
2327    }
2328 
2329    else if (type >= PNG_EQUATION_LAST)
2330    {
2331       png_chunk_benign_error(png_ptr, "unrecognized equation type");
2332    }
2333 
2334    for (buf = units; *buf; buf++)
2335       /* Empty loop to move past the units string. */ ;
2336 
2337    png_debug(3, "Allocating pCAL parameters array");
2338 
2339    params = png_voidcast(png_charpp, png_malloc_warn(png_ptr,
2340        nparams * (sizeof (png_charp))));
2341 
2342    if (params == NULL)
2343    {
2344       png_chunk_benign_error(png_ptr, "out of memory");
2345       return;
2346    }
2347 
2348    /* Get pointers to the start of each parameter string. */
2349    for (i = 0; i < nparams; i++)
2350    {
2351       buf++; /* Skip the null string terminator from previous parameter. */
2352 
2353       png_debug1(3, "Reading pCAL parameter %d", i);
2354 
2355       for (params[i] = (png_charp)buf; buf <= endptr && *buf != 0; buf++)
2356          /* Empty loop to move past each parameter string */ ;
2357 
2358       /* Make sure we haven't run out of data yet */
2359       if (buf > endptr)
2360       {
2361          png_free(png_ptr, params);
2362          png_chunk_benign_error(png_ptr, "invalid data");
2363          return;
2364       }
2365    }
2366 
2367    png_set_pCAL(png_ptr, info_ptr, (png_charp)buffer, X0, X1, type, nparams,
2368        (png_charp)units, params);
2369 
2370    png_free(png_ptr, params);
2371 }
2372 #endif
2373 
2374 #ifdef PNG_READ_sCAL_SUPPORTED
2375 /* Read the sCAL chunk */
2376 void /* PRIVATE */
png_handle_sCAL(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)2377 png_handle_sCAL(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2378 {
2379    png_bytep buffer;
2380    size_t i;
2381    int state;
2382 
2383    png_debug(1, "in png_handle_sCAL");
2384 
2385    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2386       png_chunk_error(png_ptr, "missing IHDR");
2387 
2388    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2389    {
2390       png_crc_finish(png_ptr, length);
2391       png_chunk_benign_error(png_ptr, "out of place");
2392       return;
2393    }
2394 
2395    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sCAL) != 0)
2396    {
2397       png_crc_finish(png_ptr, length);
2398       png_chunk_benign_error(png_ptr, "duplicate");
2399       return;
2400    }
2401 
2402    /* Need unit type, width, \0, height: minimum 4 bytes */
2403    else if (length < 4)
2404    {
2405       png_crc_finish(png_ptr, length);
2406       png_chunk_benign_error(png_ptr, "invalid");
2407       return;
2408    }
2409 
2410    png_debug1(2, "Allocating and reading sCAL chunk data (%u bytes)",
2411        length + 1);
2412 
2413    buffer = png_read_buffer(png_ptr, length+1, 2/*silent*/);
2414 
2415    if (buffer == NULL)
2416    {
2417       png_chunk_benign_error(png_ptr, "out of memory");
2418       png_crc_finish(png_ptr, length);
2419       return;
2420    }
2421 
2422    png_crc_read(png_ptr, buffer, length);
2423    buffer[length] = 0; /* Null terminate the last string */
2424 
2425    if (png_crc_finish(png_ptr, 0) != 0)
2426       return;
2427 
2428    /* Validate the unit. */
2429    if (buffer[0] != 1 && buffer[0] != 2)
2430    {
2431       png_chunk_benign_error(png_ptr, "invalid unit");
2432       return;
2433    }
2434 
2435    /* Validate the ASCII numbers, need two ASCII numbers separated by
2436     * a '\0' and they need to fit exactly in the chunk data.
2437     */
2438    i = 1;
2439    state = 0;
2440 
2441    if (png_check_fp_number((png_const_charp)buffer, length, &state, &i) == 0 ||
2442        i >= length || buffer[i++] != 0)
2443       png_chunk_benign_error(png_ptr, "bad width format");
2444 
2445    else if (PNG_FP_IS_POSITIVE(state) == 0)
2446       png_chunk_benign_error(png_ptr, "non-positive width");
2447 
2448    else
2449    {
2450       size_t heighti = i;
2451 
2452       state = 0;
2453       if (png_check_fp_number((png_const_charp)buffer, length,
2454           &state, &i) == 0 || i != length)
2455          png_chunk_benign_error(png_ptr, "bad height format");
2456 
2457       else if (PNG_FP_IS_POSITIVE(state) == 0)
2458          png_chunk_benign_error(png_ptr, "non-positive height");
2459 
2460       else
2461          /* This is the (only) success case. */
2462          png_set_sCAL_s(png_ptr, info_ptr, buffer[0],
2463              (png_charp)buffer+1, (png_charp)buffer+heighti);
2464    }
2465 }
2466 #endif
2467 
2468 #ifdef PNG_READ_tIME_SUPPORTED
2469 void /* PRIVATE */
png_handle_tIME(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)2470 png_handle_tIME(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2471 {
2472    png_byte buf[7];
2473    png_time mod_time;
2474 
2475    png_debug(1, "in png_handle_tIME");
2476 
2477    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2478       png_chunk_error(png_ptr, "missing IHDR");
2479 
2480    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tIME) != 0)
2481    {
2482       png_crc_finish(png_ptr, length);
2483       png_chunk_benign_error(png_ptr, "duplicate");
2484       return;
2485    }
2486 
2487    if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2488       png_ptr->mode |= PNG_AFTER_IDAT;
2489 
2490    if (length != 7)
2491    {
2492       png_crc_finish(png_ptr, length);
2493       png_chunk_benign_error(png_ptr, "invalid");
2494       return;
2495    }
2496 
2497    png_crc_read(png_ptr, buf, 7);
2498 
2499    if (png_crc_finish(png_ptr, 0) != 0)
2500       return;
2501 
2502    mod_time.second = buf[6];
2503    mod_time.minute = buf[5];
2504    mod_time.hour = buf[4];
2505    mod_time.day = buf[3];
2506    mod_time.month = buf[2];
2507    mod_time.year = png_get_uint_16(buf);
2508 
2509    png_set_tIME(png_ptr, info_ptr, &mod_time);
2510 }
2511 #endif
2512 
2513 #ifdef PNG_READ_tEXt_SUPPORTED
2514 /* Note: this does not properly handle chunks that are > 64K under DOS */
2515 void /* PRIVATE */
png_handle_tEXt(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)2516 png_handle_tEXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2517 {
2518    png_text  text_info;
2519    png_bytep buffer;
2520    png_charp key;
2521    png_charp text;
2522    png_uint_32 skip = 0;
2523 
2524    png_debug(1, "in png_handle_tEXt");
2525 
2526 #ifdef PNG_USER_LIMITS_SUPPORTED
2527    if (png_ptr->user_chunk_cache_max != 0)
2528    {
2529       if (png_ptr->user_chunk_cache_max == 1)
2530       {
2531          png_crc_finish(png_ptr, length);
2532          return;
2533       }
2534 
2535       if (--png_ptr->user_chunk_cache_max == 1)
2536       {
2537          png_crc_finish(png_ptr, length);
2538          png_chunk_benign_error(png_ptr, "no space in chunk cache");
2539          return;
2540       }
2541    }
2542 #endif
2543 
2544    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2545       png_chunk_error(png_ptr, "missing IHDR");
2546 
2547    if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2548       png_ptr->mode |= PNG_AFTER_IDAT;
2549 
2550 #ifdef PNG_MAX_MALLOC_64K
2551    if (length > 65535U)
2552    {
2553       png_crc_finish(png_ptr, length);
2554       png_chunk_benign_error(png_ptr, "too large to fit in memory");
2555       return;
2556    }
2557 #endif
2558 
2559    buffer = png_read_buffer(png_ptr, length+1, 1/*warn*/);
2560 
2561    if (buffer == NULL)
2562    {
2563       png_chunk_benign_error(png_ptr, "out of memory");
2564       return;
2565    }
2566 
2567    png_crc_read(png_ptr, buffer, length);
2568 
2569    if (png_crc_finish(png_ptr, skip) != 0)
2570       return;
2571 
2572    key = (png_charp)buffer;
2573    key[length] = 0;
2574 
2575    for (text = key; *text; text++)
2576       /* Empty loop to find end of key */ ;
2577 
2578    if (text != key + length)
2579       text++;
2580 
2581    text_info.compression = PNG_TEXT_COMPRESSION_NONE;
2582    text_info.key = key;
2583    text_info.lang = NULL;
2584    text_info.lang_key = NULL;
2585    text_info.itxt_length = 0;
2586    text_info.text = text;
2587    text_info.text_length = strlen(text);
2588 
2589    if (png_set_text_2(png_ptr, info_ptr, &text_info, 1) != 0)
2590       png_warning(png_ptr, "Insufficient memory to process text chunk");
2591 }
2592 #endif
2593 
2594 #ifdef PNG_READ_zTXt_SUPPORTED
2595 /* Note: this does not correctly handle chunks that are > 64K under DOS */
2596 void /* PRIVATE */
png_handle_zTXt(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)2597 png_handle_zTXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2598 {
2599    png_const_charp errmsg = NULL;
2600    png_bytep       buffer;
2601    png_uint_32     keyword_length;
2602 
2603    png_debug(1, "in png_handle_zTXt");
2604 
2605 #ifdef PNG_USER_LIMITS_SUPPORTED
2606    if (png_ptr->user_chunk_cache_max != 0)
2607    {
2608       if (png_ptr->user_chunk_cache_max == 1)
2609       {
2610          png_crc_finish(png_ptr, length);
2611          return;
2612       }
2613 
2614       if (--png_ptr->user_chunk_cache_max == 1)
2615       {
2616          png_crc_finish(png_ptr, length);
2617          png_chunk_benign_error(png_ptr, "no space in chunk cache");
2618          return;
2619       }
2620    }
2621 #endif
2622 
2623    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2624       png_chunk_error(png_ptr, "missing IHDR");
2625 
2626    if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2627       png_ptr->mode |= PNG_AFTER_IDAT;
2628 
2629    /* Note, "length" is sufficient here; we won't be adding
2630     * a null terminator later.
2631     */
2632    buffer = png_read_buffer(png_ptr, length, 2/*silent*/);
2633 
2634    if (buffer == NULL)
2635    {
2636       png_crc_finish(png_ptr, length);
2637       png_chunk_benign_error(png_ptr, "out of memory");
2638       return;
2639    }
2640 
2641    png_crc_read(png_ptr, buffer, length);
2642 
2643    if (png_crc_finish(png_ptr, 0) != 0)
2644       return;
2645 
2646    /* TODO: also check that the keyword contents match the spec! */
2647    for (keyword_length = 0;
2648       keyword_length < length && buffer[keyword_length] != 0;
2649       ++keyword_length)
2650       /* Empty loop to find end of name */ ;
2651 
2652    if (keyword_length > 79 || keyword_length < 1)
2653       errmsg = "bad keyword";
2654 
2655    /* zTXt must have some LZ data after the keyword, although it may expand to
2656     * zero bytes; we need a '\0' at the end of the keyword, the compression type
2657     * then the LZ data:
2658     */
2659    else if (keyword_length + 3 > length)
2660       errmsg = "truncated";
2661 
2662    else if (buffer[keyword_length+1] != PNG_COMPRESSION_TYPE_BASE)
2663       errmsg = "unknown compression type";
2664 
2665    else
2666    {
2667       png_alloc_size_t uncompressed_length = PNG_SIZE_MAX;
2668 
2669       /* TODO: at present png_decompress_chunk imposes a single application
2670        * level memory limit, this should be split to different values for iCCP
2671        * and text chunks.
2672        */
2673       if (png_decompress_chunk(png_ptr, length, keyword_length+2,
2674           &uncompressed_length, 1/*terminate*/) == Z_STREAM_END)
2675       {
2676          png_text text;
2677 
2678          if (png_ptr->read_buffer == NULL)
2679            errmsg="Read failure in png_handle_zTXt";
2680          else
2681          {
2682             /* It worked; png_ptr->read_buffer now looks like a tEXt chunk
2683              * except for the extra compression type byte and the fact that
2684              * it isn't necessarily '\0' terminated.
2685              */
2686             buffer = png_ptr->read_buffer;
2687             buffer[uncompressed_length+(keyword_length+2)] = 0;
2688 
2689             text.compression = PNG_TEXT_COMPRESSION_zTXt;
2690             text.key = (png_charp)buffer;
2691             text.text = (png_charp)(buffer + keyword_length+2);
2692             text.text_length = uncompressed_length;
2693             text.itxt_length = 0;
2694             text.lang = NULL;
2695             text.lang_key = NULL;
2696 
2697             if (png_set_text_2(png_ptr, info_ptr, &text, 1) != 0)
2698                errmsg = "insufficient memory";
2699          }
2700       }
2701 
2702       else
2703          errmsg = png_ptr->zstream.msg;
2704    }
2705 
2706    if (errmsg != NULL)
2707       png_chunk_benign_error(png_ptr, errmsg);
2708 }
2709 #endif
2710 
2711 #ifdef PNG_READ_iTXt_SUPPORTED
2712 /* Note: this does not correctly handle chunks that are > 64K under DOS */
2713 void /* PRIVATE */
png_handle_iTXt(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length)2714 png_handle_iTXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2715 {
2716    png_const_charp errmsg = NULL;
2717    png_bytep buffer;
2718    png_uint_32 prefix_length;
2719 
2720    png_debug(1, "in png_handle_iTXt");
2721 
2722 #ifdef PNG_USER_LIMITS_SUPPORTED
2723    if (png_ptr->user_chunk_cache_max != 0)
2724    {
2725       if (png_ptr->user_chunk_cache_max == 1)
2726       {
2727          png_crc_finish(png_ptr, length);
2728          return;
2729       }
2730 
2731       if (--png_ptr->user_chunk_cache_max == 1)
2732       {
2733          png_crc_finish(png_ptr, length);
2734          png_chunk_benign_error(png_ptr, "no space in chunk cache");
2735          return;
2736       }
2737    }
2738 #endif
2739 
2740    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2741       png_chunk_error(png_ptr, "missing IHDR");
2742 
2743    if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2744       png_ptr->mode |= PNG_AFTER_IDAT;
2745 
2746    buffer = png_read_buffer(png_ptr, length+1, 1/*warn*/);
2747 
2748    if (buffer == NULL)
2749    {
2750       png_crc_finish(png_ptr, length);
2751       png_chunk_benign_error(png_ptr, "out of memory");
2752       return;
2753    }
2754 
2755    png_crc_read(png_ptr, buffer, length);
2756 
2757    if (png_crc_finish(png_ptr, 0) != 0)
2758       return;
2759 
2760    /* First the keyword. */
2761    for (prefix_length=0;
2762       prefix_length < length && buffer[prefix_length] != 0;
2763       ++prefix_length)
2764       /* Empty loop */ ;
2765 
2766    /* Perform a basic check on the keyword length here. */
2767    if (prefix_length > 79 || prefix_length < 1)
2768       errmsg = "bad keyword";
2769 
2770    /* Expect keyword, compression flag, compression type, language, translated
2771     * keyword (both may be empty but are 0 terminated) then the text, which may
2772     * be empty.
2773     */
2774    else if (prefix_length + 5 > length)
2775       errmsg = "truncated";
2776 
2777    else if (buffer[prefix_length+1] == 0 ||
2778       (buffer[prefix_length+1] == 1 &&
2779       buffer[prefix_length+2] == PNG_COMPRESSION_TYPE_BASE))
2780    {
2781       int compressed = buffer[prefix_length+1] != 0;
2782       png_uint_32 language_offset, translated_keyword_offset;
2783       png_alloc_size_t uncompressed_length = 0;
2784 
2785       /* Now the language tag */
2786       prefix_length += 3;
2787       language_offset = prefix_length;
2788 
2789       for (; prefix_length < length && buffer[prefix_length] != 0;
2790          ++prefix_length)
2791          /* Empty loop */ ;
2792 
2793       /* WARNING: the length may be invalid here, this is checked below. */
2794       translated_keyword_offset = ++prefix_length;
2795 
2796       for (; prefix_length < length && buffer[prefix_length] != 0;
2797          ++prefix_length)
2798          /* Empty loop */ ;
2799 
2800       /* prefix_length should now be at the trailing '\0' of the translated
2801        * keyword, but it may already be over the end.  None of this arithmetic
2802        * can overflow because chunks are at most 2^31 bytes long, but on 16-bit
2803        * systems the available allocation may overflow.
2804        */
2805       ++prefix_length;
2806 
2807       if (compressed == 0 && prefix_length <= length)
2808          uncompressed_length = length - prefix_length;
2809 
2810       else if (compressed != 0 && prefix_length < length)
2811       {
2812          uncompressed_length = PNG_SIZE_MAX;
2813 
2814          /* TODO: at present png_decompress_chunk imposes a single application
2815           * level memory limit, this should be split to different values for
2816           * iCCP and text chunks.
2817           */
2818          if (png_decompress_chunk(png_ptr, length, prefix_length,
2819              &uncompressed_length, 1/*terminate*/) == Z_STREAM_END)
2820             buffer = png_ptr->read_buffer;
2821 
2822          else
2823             errmsg = png_ptr->zstream.msg;
2824       }
2825 
2826       else
2827          errmsg = "truncated";
2828 
2829       if (errmsg == NULL)
2830       {
2831          png_text text;
2832 
2833          buffer[uncompressed_length+prefix_length] = 0;
2834 
2835          if (compressed == 0)
2836             text.compression = PNG_ITXT_COMPRESSION_NONE;
2837 
2838          else
2839             text.compression = PNG_ITXT_COMPRESSION_zTXt;
2840 
2841          text.key = (png_charp)buffer;
2842          text.lang = (png_charp)buffer + language_offset;
2843          text.lang_key = (png_charp)buffer + translated_keyword_offset;
2844          text.text = (png_charp)buffer + prefix_length;
2845          text.text_length = 0;
2846          text.itxt_length = uncompressed_length;
2847 
2848          if (png_set_text_2(png_ptr, info_ptr, &text, 1) != 0)
2849             errmsg = "insufficient memory";
2850       }
2851    }
2852 
2853    else
2854       errmsg = "bad compression info";
2855 
2856    if (errmsg != NULL)
2857       png_chunk_benign_error(png_ptr, errmsg);
2858 }
2859 #endif
2860 
2861 #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
2862 /* Utility function for png_handle_unknown; set up png_ptr::unknown_chunk */
2863 static int
png_cache_unknown_chunk(png_structrp png_ptr,png_uint_32 length)2864 png_cache_unknown_chunk(png_structrp png_ptr, png_uint_32 length)
2865 {
2866    png_alloc_size_t limit = PNG_SIZE_MAX;
2867 
2868    if (png_ptr->unknown_chunk.data != NULL)
2869    {
2870       png_free(png_ptr, png_ptr->unknown_chunk.data);
2871       png_ptr->unknown_chunk.data = NULL;
2872    }
2873 
2874 #  ifdef PNG_SET_USER_LIMITS_SUPPORTED
2875    if (png_ptr->user_chunk_malloc_max > 0 &&
2876        png_ptr->user_chunk_malloc_max < limit)
2877       limit = png_ptr->user_chunk_malloc_max;
2878 
2879 #  elif PNG_USER_CHUNK_MALLOC_MAX > 0
2880    if (PNG_USER_CHUNK_MALLOC_MAX < limit)
2881       limit = PNG_USER_CHUNK_MALLOC_MAX;
2882 #  endif
2883 
2884    if (length <= limit)
2885    {
2886       PNG_CSTRING_FROM_CHUNK(png_ptr->unknown_chunk.name, png_ptr->chunk_name);
2887       /* The following is safe because of the PNG_SIZE_MAX init above */
2888       png_ptr->unknown_chunk.size = (size_t)length/*SAFE*/;
2889       /* 'mode' is a flag array, only the bottom four bits matter here */
2890       png_ptr->unknown_chunk.location = (png_byte)png_ptr->mode/*SAFE*/;
2891 
2892       if (length == 0)
2893          png_ptr->unknown_chunk.data = NULL;
2894 
2895       else
2896       {
2897          /* Do a 'warn' here - it is handled below. */
2898          png_ptr->unknown_chunk.data = png_voidcast(png_bytep,
2899              png_malloc_warn(png_ptr, length));
2900       }
2901    }
2902 
2903    if (png_ptr->unknown_chunk.data == NULL && length > 0)
2904    {
2905       /* This is benign because we clean up correctly */
2906       png_crc_finish(png_ptr, length);
2907       png_chunk_benign_error(png_ptr, "unknown chunk exceeds memory limits");
2908       return 0;
2909    }
2910 
2911    else
2912    {
2913       if (length > 0)
2914          png_crc_read(png_ptr, png_ptr->unknown_chunk.data, length);
2915       png_crc_finish(png_ptr, 0);
2916       return 1;
2917    }
2918 }
2919 #endif /* READ_UNKNOWN_CHUNKS */
2920 
2921 /* Handle an unknown, or known but disabled, chunk */
2922 void /* PRIVATE */
png_handle_unknown(png_structrp png_ptr,png_inforp info_ptr,png_uint_32 length,int keep)2923 png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
2924     png_uint_32 length, int keep)
2925 {
2926    int handled = 0; /* the chunk was handled */
2927 
2928    png_debug(1, "in png_handle_unknown");
2929 
2930 #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
2931    /* NOTE: this code is based on the code in libpng-1.4.12 except for fixing
2932     * the bug which meant that setting a non-default behavior for a specific
2933     * chunk would be ignored (the default was always used unless a user
2934     * callback was installed).
2935     *
2936     * 'keep' is the value from the png_chunk_unknown_handling, the setting for
2937     * this specific chunk_name, if PNG_HANDLE_AS_UNKNOWN_SUPPORTED, if not it
2938     * will always be PNG_HANDLE_CHUNK_AS_DEFAULT and it needs to be set here.
2939     * This is just an optimization to avoid multiple calls to the lookup
2940     * function.
2941     */
2942 #  ifndef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
2943 #     ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
2944    keep = png_chunk_unknown_handling(png_ptr, png_ptr->chunk_name);
2945 #     endif
2946 #  endif
2947 
2948    /* One of the following methods will read the chunk or skip it (at least one
2949     * of these is always defined because this is the only way to switch on
2950     * PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
2951     */
2952 #  ifdef PNG_READ_USER_CHUNKS_SUPPORTED
2953    /* The user callback takes precedence over the chunk keep value, but the
2954     * keep value is still required to validate a save of a critical chunk.
2955     */
2956    if (png_ptr->read_user_chunk_fn != NULL)
2957    {
2958       if (png_cache_unknown_chunk(png_ptr, length) != 0)
2959       {
2960          /* Callback to user unknown chunk handler */
2961          int ret = (*(png_ptr->read_user_chunk_fn))(png_ptr,
2962              &png_ptr->unknown_chunk);
2963 
2964          /* ret is:
2965           * negative: An error occurred; png_chunk_error will be called.
2966           *     zero: The chunk was not handled, the chunk will be discarded
2967           *           unless png_set_keep_unknown_chunks has been used to set
2968           *           a 'keep' behavior for this particular chunk, in which
2969           *           case that will be used.  A critical chunk will cause an
2970           *           error at this point unless it is to be saved.
2971           * positive: The chunk was handled, libpng will ignore/discard it.
2972           */
2973          if (ret < 0)
2974             png_chunk_error(png_ptr, "error in user chunk");
2975 
2976          else if (ret == 0)
2977          {
2978             /* If the keep value is 'default' or 'never' override it, but
2979              * still error out on critical chunks unless the keep value is
2980              * 'always'  While this is weird it is the behavior in 1.4.12.
2981              * A possible improvement would be to obey the value set for the
2982              * chunk, but this would be an API change that would probably
2983              * damage some applications.
2984              *
2985              * The png_app_warning below catches the case that matters, where
2986              * the application has not set specific save or ignore for this
2987              * chunk or global save or ignore.
2988              */
2989             if (keep < PNG_HANDLE_CHUNK_IF_SAFE)
2990             {
2991 #              ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
2992                if (png_ptr->unknown_default < PNG_HANDLE_CHUNK_IF_SAFE)
2993                {
2994                   png_chunk_warning(png_ptr, "Saving unknown chunk:");
2995                   png_app_warning(png_ptr,
2996                       "forcing save of an unhandled chunk;"
2997                       " please call png_set_keep_unknown_chunks");
2998                       /* with keep = PNG_HANDLE_CHUNK_IF_SAFE */
2999                }
3000 #              endif
3001                keep = PNG_HANDLE_CHUNK_IF_SAFE;
3002             }
3003          }
3004 
3005          else /* chunk was handled */
3006          {
3007             handled = 1;
3008             /* Critical chunks can be safely discarded at this point. */
3009             keep = PNG_HANDLE_CHUNK_NEVER;
3010          }
3011       }
3012 
3013       else
3014          keep = PNG_HANDLE_CHUNK_NEVER; /* insufficient memory */
3015    }
3016 
3017    else
3018    /* Use the SAVE_UNKNOWN_CHUNKS code or skip the chunk */
3019 #  endif /* READ_USER_CHUNKS */
3020 
3021 #  ifdef PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
3022    {
3023       /* keep is currently just the per-chunk setting, if there was no
3024        * setting change it to the global default now (not that this may
3025        * still be AS_DEFAULT) then obtain the cache of the chunk if required,
3026        * if not simply skip the chunk.
3027        */
3028       if (keep == PNG_HANDLE_CHUNK_AS_DEFAULT)
3029          keep = png_ptr->unknown_default;
3030 
3031       if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
3032          (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
3033           PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
3034       {
3035          if (png_cache_unknown_chunk(png_ptr, length) == 0)
3036             keep = PNG_HANDLE_CHUNK_NEVER;
3037       }
3038 
3039       else
3040          png_crc_finish(png_ptr, length);
3041    }
3042 #  else
3043 #     ifndef PNG_READ_USER_CHUNKS_SUPPORTED
3044 #        error no method to support READ_UNKNOWN_CHUNKS
3045 #     endif
3046 
3047    {
3048       /* If here there is no read callback pointer set and no support is
3049        * compiled in to just save the unknown chunks, so simply skip this
3050        * chunk.  If 'keep' is something other than AS_DEFAULT or NEVER then
3051        * the app has erroneously asked for unknown chunk saving when there
3052        * is no support.
3053        */
3054       if (keep > PNG_HANDLE_CHUNK_NEVER)
3055          png_app_error(png_ptr, "no unknown chunk support available");
3056 
3057       png_crc_finish(png_ptr, length);
3058    }
3059 #  endif
3060 
3061 #  ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
3062    /* Now store the chunk in the chunk list if appropriate, and if the limits
3063     * permit it.
3064     */
3065    if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
3066       (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
3067        PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
3068    {
3069 #     ifdef PNG_USER_LIMITS_SUPPORTED
3070       switch (png_ptr->user_chunk_cache_max)
3071       {
3072          case 2:
3073             png_ptr->user_chunk_cache_max = 1;
3074             png_chunk_benign_error(png_ptr, "no space in chunk cache");
3075             /* FALLTHROUGH */
3076          case 1:
3077             /* NOTE: prior to 1.6.0 this case resulted in an unknown critical
3078              * chunk being skipped, now there will be a hard error below.
3079              */
3080             break;
3081 
3082          default: /* not at limit */
3083             --(png_ptr->user_chunk_cache_max);
3084             /* FALLTHROUGH */
3085          case 0: /* no limit */
3086 #  endif /* USER_LIMITS */
3087             /* Here when the limit isn't reached or when limits are compiled
3088              * out; store the chunk.
3089              */
3090             png_set_unknown_chunks(png_ptr, info_ptr,
3091                 &png_ptr->unknown_chunk, 1);
3092             handled = 1;
3093 #  ifdef PNG_USER_LIMITS_SUPPORTED
3094             break;
3095       }
3096 #  endif
3097    }
3098 #  else /* no store support: the chunk must be handled by the user callback */
3099    PNG_UNUSED(info_ptr)
3100 #  endif
3101 
3102    /* Regardless of the error handling below the cached data (if any) can be
3103     * freed now.  Notice that the data is not freed if there is a png_error, but
3104     * it will be freed by destroy_read_struct.
3105     */
3106    if (png_ptr->unknown_chunk.data != NULL)
3107       png_free(png_ptr, png_ptr->unknown_chunk.data);
3108    png_ptr->unknown_chunk.data = NULL;
3109 
3110 #else /* !PNG_READ_UNKNOWN_CHUNKS_SUPPORTED */
3111    /* There is no support to read an unknown chunk, so just skip it. */
3112    png_crc_finish(png_ptr, length);
3113    PNG_UNUSED(info_ptr)
3114    PNG_UNUSED(keep)
3115 #endif /* !READ_UNKNOWN_CHUNKS */
3116 
3117    /* Check for unhandled critical chunks */
3118    if (handled == 0 && PNG_CHUNK_CRITICAL(png_ptr->chunk_name))
3119       png_chunk_error(png_ptr, "unhandled critical chunk");
3120 }
3121 
3122 /* This function is called to verify that a chunk name is valid.
3123  * This function can't have the "critical chunk check" incorporated
3124  * into it, since in the future we will need to be able to call user
3125  * functions to handle unknown critical chunks after we check that
3126  * the chunk name itself is valid.
3127  */
3128 
3129 /* Bit hacking: the test for an invalid byte in the 4 byte chunk name is:
3130  *
3131  * ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97))
3132  */
3133 
3134 void /* PRIVATE */
png_check_chunk_name(png_const_structrp png_ptr,const png_uint_32 chunk_name)3135 png_check_chunk_name(png_const_structrp png_ptr, const png_uint_32 chunk_name)
3136 {
3137    int i;
3138    png_uint_32 cn=chunk_name;
3139 
3140    png_debug(1, "in png_check_chunk_name");
3141 
3142    for (i=1; i<=4; ++i)
3143    {
3144       int c = cn & 0xff;
3145 
3146       if (c < 65 || c > 122 || (c > 90 && c < 97))
3147          png_chunk_error(png_ptr, "invalid chunk type");
3148 
3149       cn >>= 8;
3150    }
3151 }
3152 
3153 void /* PRIVATE */
png_check_chunk_length(png_const_structrp png_ptr,const png_uint_32 length)3154 png_check_chunk_length(png_const_structrp png_ptr, const png_uint_32 length)
3155 {
3156    png_alloc_size_t limit = PNG_UINT_31_MAX;
3157 
3158 # ifdef PNG_SET_USER_LIMITS_SUPPORTED
3159    if (png_ptr->user_chunk_malloc_max > 0 &&
3160        png_ptr->user_chunk_malloc_max < limit)
3161       limit = png_ptr->user_chunk_malloc_max;
3162 # elif PNG_USER_CHUNK_MALLOC_MAX > 0
3163    if (PNG_USER_CHUNK_MALLOC_MAX < limit)
3164       limit = PNG_USER_CHUNK_MALLOC_MAX;
3165 # endif
3166    if (png_ptr->chunk_name == png_IDAT)
3167    {
3168       png_alloc_size_t idat_limit = PNG_UINT_31_MAX;
3169       size_t row_factor =
3170          (size_t)png_ptr->width
3171          * (size_t)png_ptr->channels
3172          * (png_ptr->bit_depth > 8? 2: 1)
3173          + 1
3174          + (png_ptr->interlaced? 6: 0);
3175       if (png_ptr->height > PNG_UINT_32_MAX/row_factor)
3176          idat_limit = PNG_UINT_31_MAX;
3177       else
3178          idat_limit = png_ptr->height * row_factor;
3179       row_factor = row_factor > 32566? 32566 : row_factor;
3180       idat_limit += 6 + 5*(idat_limit/row_factor+1); /* zlib+deflate overhead */
3181       idat_limit=idat_limit < PNG_UINT_31_MAX? idat_limit : PNG_UINT_31_MAX;
3182       limit = limit < idat_limit? idat_limit : limit;
3183    }
3184 
3185    if (length > limit)
3186    {
3187       png_debug2(0," length = %lu, limit = %lu",
3188          (unsigned long)length,(unsigned long)limit);
3189       png_chunk_error(png_ptr, "chunk data is too large");
3190    }
3191 }
3192 
3193 /* Combines the row recently read in with the existing pixels in the row.  This
3194  * routine takes care of alpha and transparency if requested.  This routine also
3195  * handles the two methods of progressive display of interlaced images,
3196  * depending on the 'display' value; if 'display' is true then the whole row
3197  * (dp) is filled from the start by replicating the available pixels.  If
3198  * 'display' is false only those pixels present in the pass are filled in.
3199  */
3200 void /* PRIVATE */
png_combine_row(png_const_structrp png_ptr,png_bytep dp,int display)3201 png_combine_row(png_const_structrp png_ptr, png_bytep dp, int display)
3202 {
3203    unsigned int pixel_depth = png_ptr->transformed_pixel_depth;
3204    png_const_bytep sp = png_ptr->row_buf + 1;
3205    png_alloc_size_t row_width = png_ptr->width;
3206    unsigned int pass = png_ptr->pass;
3207    png_bytep end_ptr = 0;
3208    png_byte end_byte = 0;
3209    unsigned int end_mask;
3210 
3211    png_debug(1, "in png_combine_row");
3212 
3213    /* Added in 1.5.6: it should not be possible to enter this routine until at
3214     * least one row has been read from the PNG data and transformed.
3215     */
3216    if (pixel_depth == 0)
3217       png_error(png_ptr, "internal row logic error");
3218 
3219    /* Added in 1.5.4: the pixel depth should match the information returned by
3220     * any call to png_read_update_info at this point.  Do not continue if we got
3221     * this wrong.
3222     */
3223    if (png_ptr->info_rowbytes != 0 && png_ptr->info_rowbytes !=
3224           PNG_ROWBYTES(pixel_depth, row_width))
3225       png_error(png_ptr, "internal row size calculation error");
3226 
3227    /* Don't expect this to ever happen: */
3228    if (row_width == 0)
3229       png_error(png_ptr, "internal row width error");
3230 
3231    /* Preserve the last byte in cases where only part of it will be overwritten,
3232     * the multiply below may overflow, we don't care because ANSI-C guarantees
3233     * we get the low bits.
3234     */
3235    end_mask = (pixel_depth * row_width) & 7;
3236    if (end_mask != 0)
3237    {
3238       /* end_ptr == NULL is a flag to say do nothing */
3239       end_ptr = dp + PNG_ROWBYTES(pixel_depth, row_width) - 1;
3240       end_byte = *end_ptr;
3241 #     ifdef PNG_READ_PACKSWAP_SUPPORTED
3242       if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
3243          /* little-endian byte */
3244          end_mask = (unsigned int)(0xff << end_mask);
3245 
3246       else /* big-endian byte */
3247 #     endif
3248       end_mask = 0xff >> end_mask;
3249       /* end_mask is now the bits to *keep* from the destination row */
3250    }
3251 
3252    /* For non-interlaced images this reduces to a memcpy(). A memcpy()
3253     * will also happen if interlacing isn't supported or if the application
3254     * does not call png_set_interlace_handling().  In the latter cases the
3255     * caller just gets a sequence of the unexpanded rows from each interlace
3256     * pass.
3257     */
3258 #ifdef PNG_READ_INTERLACING_SUPPORTED
3259    if (png_ptr->interlaced != 0 &&
3260        (png_ptr->transformations & PNG_INTERLACE) != 0 &&
3261        pass < 6 && (display == 0 ||
3262        /* The following copies everything for 'display' on passes 0, 2 and 4. */
3263        (display == 1 && (pass & 1) != 0)))
3264    {
3265       /* Narrow images may have no bits in a pass; the caller should handle
3266        * this, but this test is cheap:
3267        */
3268       if (row_width <= PNG_PASS_START_COL(pass))
3269          return;
3270 
3271       if (pixel_depth < 8)
3272       {
3273          /* For pixel depths up to 4 bpp the 8-pixel mask can be expanded to fit
3274           * into 32 bits, then a single loop over the bytes using the four byte
3275           * values in the 32-bit mask can be used.  For the 'display' option the
3276           * expanded mask may also not require any masking within a byte.  To
3277           * make this work the PACKSWAP option must be taken into account - it
3278           * simply requires the pixels to be reversed in each byte.
3279           *
3280           * The 'regular' case requires a mask for each of the first 6 passes,
3281           * the 'display' case does a copy for the even passes in the range
3282           * 0..6.  This has already been handled in the test above.
3283           *
3284           * The masks are arranged as four bytes with the first byte to use in
3285           * the lowest bits (little-endian) regardless of the order (PACKSWAP or
3286           * not) of the pixels in each byte.
3287           *
3288           * NOTE: the whole of this logic depends on the caller of this function
3289           * only calling it on rows appropriate to the pass.  This function only
3290           * understands the 'x' logic; the 'y' logic is handled by the caller.
3291           *
3292           * The following defines allow generation of compile time constant bit
3293           * masks for each pixel depth and each possibility of swapped or not
3294           * swapped bytes.  Pass 'p' is in the range 0..6; 'x', a pixel index,
3295           * is in the range 0..7; and the result is 1 if the pixel is to be
3296           * copied in the pass, 0 if not.  'S' is for the sparkle method, 'B'
3297           * for the block method.
3298           *
3299           * With some compilers a compile time expression of the general form:
3300           *
3301           *    (shift >= 32) ? (a >> (shift-32)) : (b >> shift)
3302           *
3303           * Produces warnings with values of 'shift' in the range 33 to 63
3304           * because the right hand side of the ?: expression is evaluated by
3305           * the compiler even though it isn't used.  Microsoft Visual C (various
3306           * versions) and the Intel C compiler are known to do this.  To avoid
3307           * this the following macros are used in 1.5.6.  This is a temporary
3308           * solution to avoid destabilizing the code during the release process.
3309           */
3310 #        if PNG_USE_COMPILE_TIME_MASKS
3311 #           define PNG_LSR(x,s) ((x)>>((s) & 0x1f))
3312 #           define PNG_LSL(x,s) ((x)<<((s) & 0x1f))
3313 #        else
3314 #           define PNG_LSR(x,s) ((x)>>(s))
3315 #           define PNG_LSL(x,s) ((x)<<(s))
3316 #        endif
3317 #        define S_COPY(p,x) (((p)<4 ? PNG_LSR(0x80088822,(3-(p))*8+(7-(x))) :\
3318            PNG_LSR(0xaa55ff00,(7-(p))*8+(7-(x)))) & 1)
3319 #        define B_COPY(p,x) (((p)<4 ? PNG_LSR(0xff0fff33,(3-(p))*8+(7-(x))) :\
3320            PNG_LSR(0xff55ff00,(7-(p))*8+(7-(x)))) & 1)
3321 
3322          /* Return a mask for pass 'p' pixel 'x' at depth 'd'.  The mask is
3323           * little endian - the first pixel is at bit 0 - however the extra
3324           * parameter 's' can be set to cause the mask position to be swapped
3325           * within each byte, to match the PNG format.  This is done by XOR of
3326           * the shift with 7, 6 or 4 for bit depths 1, 2 and 4.
3327           */
3328 #        define PIXEL_MASK(p,x,d,s) \
3329             (PNG_LSL(((PNG_LSL(1U,(d)))-1),(((x)*(d))^((s)?8-(d):0))))
3330 
3331          /* Hence generate the appropriate 'block' or 'sparkle' pixel copy mask.
3332           */
3333 #        define S_MASKx(p,x,d,s) (S_COPY(p,x)?PIXEL_MASK(p,x,d,s):0)
3334 #        define B_MASKx(p,x,d,s) (B_COPY(p,x)?PIXEL_MASK(p,x,d,s):0)
3335 
3336          /* Combine 8 of these to get the full mask.  For the 1-bpp and 2-bpp
3337           * cases the result needs replicating, for the 4-bpp case the above
3338           * generates a full 32 bits.
3339           */
3340 #        define MASK_EXPAND(m,d) ((m)*((d)==1?0x01010101:((d)==2?0x00010001:1)))
3341 
3342 #        define S_MASK(p,d,s) MASK_EXPAND(S_MASKx(p,0,d,s) + S_MASKx(p,1,d,s) +\
3343             S_MASKx(p,2,d,s) + S_MASKx(p,3,d,s) + S_MASKx(p,4,d,s) +\
3344             S_MASKx(p,5,d,s) + S_MASKx(p,6,d,s) + S_MASKx(p,7,d,s), d)
3345 
3346 #        define B_MASK(p,d,s) MASK_EXPAND(B_MASKx(p,0,d,s) + B_MASKx(p,1,d,s) +\
3347             B_MASKx(p,2,d,s) + B_MASKx(p,3,d,s) + B_MASKx(p,4,d,s) +\
3348             B_MASKx(p,5,d,s) + B_MASKx(p,6,d,s) + B_MASKx(p,7,d,s), d)
3349 
3350 #if PNG_USE_COMPILE_TIME_MASKS
3351          /* Utility macros to construct all the masks for a depth/swap
3352           * combination.  The 's' parameter says whether the format is PNG
3353           * (big endian bytes) or not.  Only the three odd-numbered passes are
3354           * required for the display/block algorithm.
3355           */
3356 #        define S_MASKS(d,s) { S_MASK(0,d,s), S_MASK(1,d,s), S_MASK(2,d,s),\
3357             S_MASK(3,d,s), S_MASK(4,d,s), S_MASK(5,d,s) }
3358 
3359 #        define B_MASKS(d,s) { B_MASK(1,d,s), B_MASK(3,d,s), B_MASK(5,d,s) }
3360 
3361 #        define DEPTH_INDEX(d) ((d)==1?0:((d)==2?1:2))
3362 
3363          /* Hence the pre-compiled masks indexed by PACKSWAP (or not), depth and
3364           * then pass:
3365           */
3366          static PNG_CONST png_uint_32 row_mask[2/*PACKSWAP*/][3/*depth*/][6] =
3367          {
3368             /* Little-endian byte masks for PACKSWAP */
3369             { S_MASKS(1,0), S_MASKS(2,0), S_MASKS(4,0) },
3370             /* Normal (big-endian byte) masks - PNG format */
3371             { S_MASKS(1,1), S_MASKS(2,1), S_MASKS(4,1) }
3372          };
3373 
3374          /* display_mask has only three entries for the odd passes, so index by
3375           * pass>>1.
3376           */
3377          static PNG_CONST png_uint_32 display_mask[2][3][3] =
3378          {
3379             /* Little-endian byte masks for PACKSWAP */
3380             { B_MASKS(1,0), B_MASKS(2,0), B_MASKS(4,0) },
3381             /* Normal (big-endian byte) masks - PNG format */
3382             { B_MASKS(1,1), B_MASKS(2,1), B_MASKS(4,1) }
3383          };
3384 
3385 #        define MASK(pass,depth,display,png)\
3386             ((display)?display_mask[png][DEPTH_INDEX(depth)][pass>>1]:\
3387                row_mask[png][DEPTH_INDEX(depth)][pass])
3388 
3389 #else /* !PNG_USE_COMPILE_TIME_MASKS */
3390          /* This is the runtime alternative: it seems unlikely that this will
3391           * ever be either smaller or faster than the compile time approach.
3392           */
3393 #        define MASK(pass,depth,display,png)\
3394             ((display)?B_MASK(pass,depth,png):S_MASK(pass,depth,png))
3395 #endif /* !USE_COMPILE_TIME_MASKS */
3396 
3397          /* Use the appropriate mask to copy the required bits.  In some cases
3398           * the byte mask will be 0 or 0xff; optimize these cases.  row_width is
3399           * the number of pixels, but the code copies bytes, so it is necessary
3400           * to special case the end.
3401           */
3402          png_uint_32 pixels_per_byte = 8 / pixel_depth;
3403          png_uint_32 mask;
3404 
3405 #        ifdef PNG_READ_PACKSWAP_SUPPORTED
3406          if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
3407             mask = MASK(pass, pixel_depth, display, 0);
3408 
3409          else
3410 #        endif
3411          mask = MASK(pass, pixel_depth, display, 1);
3412 
3413          for (;;)
3414          {
3415             png_uint_32 m;
3416 
3417             /* It doesn't matter in the following if png_uint_32 has more than
3418              * 32 bits because the high bits always match those in m<<24; it is,
3419              * however, essential to use OR here, not +, because of this.
3420              */
3421             m = mask;
3422             mask = (m >> 8) | (m << 24); /* rotate right to good compilers */
3423             m &= 0xff;
3424 
3425             if (m != 0) /* something to copy */
3426             {
3427                if (m != 0xff)
3428                   *dp = (png_byte)((*dp & ~m) | (*sp & m));
3429                else
3430                   *dp = *sp;
3431             }
3432 
3433             /* NOTE: this may overwrite the last byte with garbage if the image
3434              * is not an exact number of bytes wide; libpng has always done
3435              * this.
3436              */
3437             if (row_width <= pixels_per_byte)
3438                break; /* May need to restore part of the last byte */
3439 
3440             row_width -= pixels_per_byte;
3441             ++dp;
3442             ++sp;
3443          }
3444       }
3445 
3446       else /* pixel_depth >= 8 */
3447       {
3448          unsigned int bytes_to_copy, bytes_to_jump;
3449 
3450          /* Validate the depth - it must be a multiple of 8 */
3451          if (pixel_depth & 7)
3452             png_error(png_ptr, "invalid user transform pixel depth");
3453 
3454          pixel_depth >>= 3; /* now in bytes */
3455          row_width *= pixel_depth;
3456 
3457          /* Regardless of pass number the Adam 7 interlace always results in a
3458           * fixed number of pixels to copy then to skip.  There may be a
3459           * different number of pixels to skip at the start though.
3460           */
3461          {
3462             unsigned int offset = PNG_PASS_START_COL(pass) * pixel_depth;
3463 
3464             row_width -= offset;
3465             dp += offset;
3466             sp += offset;
3467          }
3468 
3469          /* Work out the bytes to copy. */
3470          if (display != 0)
3471          {
3472             /* When doing the 'block' algorithm the pixel in the pass gets
3473              * replicated to adjacent pixels.  This is why the even (0,2,4,6)
3474              * passes are skipped above - the entire expanded row is copied.
3475              */
3476             bytes_to_copy = (1<<((6-pass)>>1)) * pixel_depth;
3477 
3478             /* But don't allow this number to exceed the actual row width. */
3479             if (bytes_to_copy > row_width)
3480                bytes_to_copy = (unsigned int)/*SAFE*/row_width;
3481          }
3482 
3483          else /* normal row; Adam7 only ever gives us one pixel to copy. */
3484             bytes_to_copy = pixel_depth;
3485 
3486          /* In Adam7 there is a constant offset between where the pixels go. */
3487          bytes_to_jump = PNG_PASS_COL_OFFSET(pass) * pixel_depth;
3488 
3489          /* And simply copy these bytes.  Some optimization is possible here,
3490           * depending on the value of 'bytes_to_copy'.  Special case the low
3491           * byte counts, which we know to be frequent.
3492           *
3493           * Notice that these cases all 'return' rather than 'break' - this
3494           * avoids an unnecessary test on whether to restore the last byte
3495           * below.
3496           */
3497          switch (bytes_to_copy)
3498          {
3499             case 1:
3500                for (;;)
3501                {
3502                   *dp = *sp;
3503 
3504                   if (row_width <= bytes_to_jump)
3505                      return;
3506 
3507                   dp += bytes_to_jump;
3508                   sp += bytes_to_jump;
3509                   row_width -= bytes_to_jump;
3510                }
3511 
3512             case 2:
3513                /* There is a possibility of a partial copy at the end here; this
3514                 * slows the code down somewhat.
3515                 */
3516                do
3517                {
3518                   dp[0] = sp[0]; dp[1] = sp[1];
3519 
3520                   if (row_width <= bytes_to_jump)
3521                      return;
3522 
3523                   sp += bytes_to_jump;
3524                   dp += bytes_to_jump;
3525                   row_width -= bytes_to_jump;
3526                }
3527                while (row_width > 1);
3528 
3529                /* And there can only be one byte left at this point: */
3530                *dp = *sp;
3531                return;
3532 
3533             case 3:
3534                /* This can only be the RGB case, so each copy is exactly one
3535                 * pixel and it is not necessary to check for a partial copy.
3536                 */
3537                for (;;)
3538                {
3539                   dp[0] = sp[0]; dp[1] = sp[1]; dp[2] = sp[2];
3540 
3541                   if (row_width <= bytes_to_jump)
3542                      return;
3543 
3544                   sp += bytes_to_jump;
3545                   dp += bytes_to_jump;
3546                   row_width -= bytes_to_jump;
3547                }
3548 
3549             default:
3550 #if PNG_ALIGN_TYPE != PNG_ALIGN_NONE
3551                /* Check for double byte alignment and, if possible, use a
3552                 * 16-bit copy.  Don't attempt this for narrow images - ones that
3553                 * are less than an interlace panel wide.  Don't attempt it for
3554                 * wide bytes_to_copy either - use the memcpy there.
3555                 */
3556                if (bytes_to_copy < 16 /*else use memcpy*/ &&
3557                    png_isaligned(dp, png_uint_16) &&
3558                    png_isaligned(sp, png_uint_16) &&
3559                    bytes_to_copy % (sizeof (png_uint_16)) == 0 &&
3560                    bytes_to_jump % (sizeof (png_uint_16)) == 0)
3561                {
3562                   /* Everything is aligned for png_uint_16 copies, but try for
3563                    * png_uint_32 first.
3564                    */
3565                   if (png_isaligned(dp, png_uint_32) &&
3566                       png_isaligned(sp, png_uint_32) &&
3567                       bytes_to_copy % (sizeof (png_uint_32)) == 0 &&
3568                       bytes_to_jump % (sizeof (png_uint_32)) == 0)
3569                   {
3570                      png_uint_32p dp32 = png_aligncast(png_uint_32p,dp);
3571                      png_const_uint_32p sp32 = png_aligncastconst(
3572                          png_const_uint_32p, sp);
3573                      size_t skip = (bytes_to_jump-bytes_to_copy) /
3574                          (sizeof (png_uint_32));
3575 
3576                      do
3577                      {
3578                         size_t c = bytes_to_copy;
3579                         do
3580                         {
3581                            *dp32++ = *sp32++;
3582                            c -= (sizeof (png_uint_32));
3583                         }
3584                         while (c > 0);
3585 
3586                         if (row_width <= bytes_to_jump)
3587                            return;
3588 
3589                         dp32 += skip;
3590                         sp32 += skip;
3591                         row_width -= bytes_to_jump;
3592                      }
3593                      while (bytes_to_copy <= row_width);
3594 
3595                      /* Get to here when the row_width truncates the final copy.
3596                       * There will be 1-3 bytes left to copy, so don't try the
3597                       * 16-bit loop below.
3598                       */
3599                      dp = (png_bytep)dp32;
3600                      sp = (png_const_bytep)sp32;
3601                      do
3602                         *dp++ = *sp++;
3603                      while (--row_width > 0);
3604                      return;
3605                   }
3606 
3607                   /* Else do it in 16-bit quantities, but only if the size is
3608                    * not too large.
3609                    */
3610                   else
3611                   {
3612                      png_uint_16p dp16 = png_aligncast(png_uint_16p, dp);
3613                      png_const_uint_16p sp16 = png_aligncastconst(
3614                         png_const_uint_16p, sp);
3615                      size_t skip = (bytes_to_jump-bytes_to_copy) /
3616                         (sizeof (png_uint_16));
3617 
3618                      do
3619                      {
3620                         size_t c = bytes_to_copy;
3621                         do
3622                         {
3623                            *dp16++ = *sp16++;
3624                            c -= (sizeof (png_uint_16));
3625                         }
3626                         while (c > 0);
3627 
3628                         if (row_width <= bytes_to_jump)
3629                            return;
3630 
3631                         dp16 += skip;
3632                         sp16 += skip;
3633                         row_width -= bytes_to_jump;
3634                      }
3635                      while (bytes_to_copy <= row_width);
3636 
3637                      /* End of row - 1 byte left, bytes_to_copy > row_width: */
3638                      dp = (png_bytep)dp16;
3639                      sp = (png_const_bytep)sp16;
3640                      do
3641                         *dp++ = *sp++;
3642                      while (--row_width > 0);
3643                      return;
3644                   }
3645                }
3646 #endif /* ALIGN_TYPE code */
3647 
3648                /* The true default - use a memcpy: */
3649                for (;;)
3650                {
3651                   memcpy(dp, sp, bytes_to_copy);
3652 
3653                   if (row_width <= bytes_to_jump)
3654                      return;
3655 
3656                   sp += bytes_to_jump;
3657                   dp += bytes_to_jump;
3658                   row_width -= bytes_to_jump;
3659                   if (bytes_to_copy > row_width)
3660                      bytes_to_copy = (unsigned int)/*SAFE*/row_width;
3661                }
3662          }
3663 
3664          /* NOT REACHED*/
3665       } /* pixel_depth >= 8 */
3666 
3667       /* Here if pixel_depth < 8 to check 'end_ptr' below. */
3668    }
3669    else
3670 #endif /* READ_INTERLACING */
3671 
3672    /* If here then the switch above wasn't used so just memcpy the whole row
3673     * from the temporary row buffer (notice that this overwrites the end of the
3674     * destination row if it is a partial byte.)
3675     */
3676    memcpy(dp, sp, PNG_ROWBYTES(pixel_depth, row_width));
3677 
3678    /* Restore the overwritten bits from the last byte if necessary. */
3679    if (end_ptr != NULL)
3680       *end_ptr = (png_byte)((end_byte & end_mask) | (*end_ptr & ~end_mask));
3681 }
3682 
3683 #ifdef PNG_READ_INTERLACING_SUPPORTED
3684 void /* PRIVATE */
png_do_read_interlace(png_row_infop row_info,png_bytep row,int pass,png_uint_32 transformations)3685 png_do_read_interlace(png_row_infop row_info, png_bytep row, int pass,
3686     png_uint_32 transformations /* Because these may affect the byte layout */)
3687 {
3688    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
3689    /* Offset to next interlace block */
3690    static PNG_CONST unsigned int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
3691 
3692    png_debug(1, "in png_do_read_interlace");
3693    if (row != NULL && row_info != NULL)
3694    {
3695       png_uint_32 final_width;
3696 
3697       final_width = row_info->width * png_pass_inc[pass];
3698 
3699       switch (row_info->pixel_depth)
3700       {
3701          case 1:
3702          {
3703             png_bytep sp = row + (size_t)((row_info->width - 1) >> 3);
3704             png_bytep dp = row + (size_t)((final_width - 1) >> 3);
3705             unsigned int sshift, dshift;
3706             unsigned int s_start, s_end;
3707             int s_inc;
3708             int jstop = (int)png_pass_inc[pass];
3709             png_byte v;
3710             png_uint_32 i;
3711             int j;
3712 
3713 #ifdef PNG_READ_PACKSWAP_SUPPORTED
3714             if ((transformations & PNG_PACKSWAP) != 0)
3715             {
3716                 sshift = ((row_info->width + 7) & 0x07);
3717                 dshift = ((final_width + 7) & 0x07);
3718                 s_start = 7;
3719                 s_end = 0;
3720                 s_inc = -1;
3721             }
3722 
3723             else
3724 #endif
3725             {
3726                 sshift = 7 - ((row_info->width + 7) & 0x07);
3727                 dshift = 7 - ((final_width + 7) & 0x07);
3728                 s_start = 0;
3729                 s_end = 7;
3730                 s_inc = 1;
3731             }
3732 
3733             for (i = 0; i < row_info->width; i++)
3734             {
3735                v = (png_byte)((*sp >> sshift) & 0x01);
3736                for (j = 0; j < jstop; j++)
3737                {
3738                   unsigned int tmp = *dp & (0x7f7f >> (7 - dshift));
3739                   tmp |= (unsigned int)(v << dshift);
3740                   *dp = (png_byte)(tmp & 0xff);
3741 
3742                   if (dshift == s_end)
3743                   {
3744                      dshift = s_start;
3745                      dp--;
3746                   }
3747 
3748                   else
3749                      dshift = (unsigned int)((int)dshift + s_inc);
3750                }
3751 
3752                if (sshift == s_end)
3753                {
3754                   sshift = s_start;
3755                   sp--;
3756                }
3757 
3758                else
3759                   sshift = (unsigned int)((int)sshift + s_inc);
3760             }
3761             break;
3762          }
3763 
3764          case 2:
3765          {
3766             png_bytep sp = row + (png_uint_32)((row_info->width - 1) >> 2);
3767             png_bytep dp = row + (png_uint_32)((final_width - 1) >> 2);
3768             unsigned int sshift, dshift;
3769             unsigned int s_start, s_end;
3770             int s_inc;
3771             int jstop = (int)png_pass_inc[pass];
3772             png_uint_32 i;
3773 
3774 #ifdef PNG_READ_PACKSWAP_SUPPORTED
3775             if ((transformations & PNG_PACKSWAP) != 0)
3776             {
3777                sshift = (((row_info->width + 3) & 0x03) << 1);
3778                dshift = (((final_width + 3) & 0x03) << 1);
3779                s_start = 6;
3780                s_end = 0;
3781                s_inc = -2;
3782             }
3783 
3784             else
3785 #endif
3786             {
3787                sshift = ((3 - ((row_info->width + 3) & 0x03)) << 1);
3788                dshift = ((3 - ((final_width + 3) & 0x03)) << 1);
3789                s_start = 0;
3790                s_end = 6;
3791                s_inc = 2;
3792             }
3793 
3794             for (i = 0; i < row_info->width; i++)
3795             {
3796                png_byte v;
3797                int j;
3798 
3799                v = (png_byte)((*sp >> sshift) & 0x03);
3800                for (j = 0; j < jstop; j++)
3801                {
3802                   unsigned int tmp = *dp & (0x3f3f >> (6 - dshift));
3803                   tmp |= (unsigned int)(v << dshift);
3804                   *dp = (png_byte)(tmp & 0xff);
3805 
3806                   if (dshift == s_end)
3807                   {
3808                      dshift = s_start;
3809                      dp--;
3810                   }
3811 
3812                   else
3813                      dshift = (unsigned int)((int)dshift + s_inc);
3814                }
3815 
3816                if (sshift == s_end)
3817                {
3818                   sshift = s_start;
3819                   sp--;
3820                }
3821 
3822                else
3823                   sshift = (unsigned int)((int)sshift + s_inc);
3824             }
3825             break;
3826          }
3827 
3828          case 4:
3829          {
3830             png_bytep sp = row + (size_t)((row_info->width - 1) >> 1);
3831             png_bytep dp = row + (size_t)((final_width - 1) >> 1);
3832             unsigned int sshift, dshift;
3833             unsigned int s_start, s_end;
3834             int s_inc;
3835             png_uint_32 i;
3836             int jstop = (int)png_pass_inc[pass];
3837 
3838 #ifdef PNG_READ_PACKSWAP_SUPPORTED
3839             if ((transformations & PNG_PACKSWAP) != 0)
3840             {
3841                sshift = (((row_info->width + 1) & 0x01) << 2);
3842                dshift = (((final_width + 1) & 0x01) << 2);
3843                s_start = 4;
3844                s_end = 0;
3845                s_inc = -4;
3846             }
3847 
3848             else
3849 #endif
3850             {
3851                sshift = ((1 - ((row_info->width + 1) & 0x01)) << 2);
3852                dshift = ((1 - ((final_width + 1) & 0x01)) << 2);
3853                s_start = 0;
3854                s_end = 4;
3855                s_inc = 4;
3856             }
3857 
3858             for (i = 0; i < row_info->width; i++)
3859             {
3860                png_byte v = (png_byte)((*sp >> sshift) & 0x0f);
3861                int j;
3862 
3863                for (j = 0; j < jstop; j++)
3864                {
3865                   unsigned int tmp = *dp & (0xf0f >> (4 - dshift));
3866                   tmp |= (unsigned int)(v << dshift);
3867                   *dp = (png_byte)(tmp & 0xff);
3868 
3869                   if (dshift == s_end)
3870                   {
3871                      dshift = s_start;
3872                      dp--;
3873                   }
3874 
3875                   else
3876                      dshift = (unsigned int)((int)dshift + s_inc);
3877                }
3878 
3879                if (sshift == s_end)
3880                {
3881                   sshift = s_start;
3882                   sp--;
3883                }
3884 
3885                else
3886                   sshift = (unsigned int)((int)sshift + s_inc);
3887             }
3888             break;
3889          }
3890 
3891          default:
3892          {
3893             size_t pixel_bytes = (row_info->pixel_depth >> 3);
3894 
3895             png_bytep sp = row + (size_t)(row_info->width - 1)
3896                 * pixel_bytes;
3897 
3898             png_bytep dp = row + (size_t)(final_width - 1) * pixel_bytes;
3899 
3900             int jstop = (int)png_pass_inc[pass];
3901             png_uint_32 i;
3902 
3903             for (i = 0; i < row_info->width; i++)
3904             {
3905                png_byte v[8]; /* SAFE; pixel_depth does not exceed 64 */
3906                int j;
3907 
3908                memcpy(v, sp, pixel_bytes);
3909 
3910                for (j = 0; j < jstop; j++)
3911                {
3912                   memcpy(dp, v, pixel_bytes);
3913                   dp -= pixel_bytes;
3914                }
3915 
3916                sp -= pixel_bytes;
3917             }
3918             break;
3919          }
3920       }
3921 
3922       row_info->width = final_width;
3923       row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, final_width);
3924    }
3925 #ifndef PNG_READ_PACKSWAP_SUPPORTED
3926    PNG_UNUSED(transformations)  /* Silence compiler warning */
3927 #endif
3928 }
3929 #endif /* READ_INTERLACING */
3930 
3931 static void
png_read_filter_row_sub(png_row_infop row_info,png_bytep row,png_const_bytep prev_row)3932 png_read_filter_row_sub(png_row_infop row_info, png_bytep row,
3933     png_const_bytep prev_row)
3934 {
3935    size_t i;
3936    size_t istop = row_info->rowbytes;
3937    unsigned int bpp = (row_info->pixel_depth + 7) >> 3;
3938    png_bytep rp = row + bpp;
3939 
3940    PNG_UNUSED(prev_row)
3941 
3942    for (i = bpp; i < istop; i++)
3943    {
3944       *rp = (png_byte)(((int)(*rp) + (int)(*(rp-bpp))) & 0xff);
3945       rp++;
3946    }
3947 }
3948 
3949 static void
png_read_filter_row_up(png_row_infop row_info,png_bytep row,png_const_bytep prev_row)3950 png_read_filter_row_up(png_row_infop row_info, png_bytep row,
3951     png_const_bytep prev_row)
3952 {
3953    size_t i;
3954    size_t istop = row_info->rowbytes;
3955    png_bytep rp = row;
3956    png_const_bytep pp = prev_row;
3957 
3958    for (i = 0; i < istop; i++)
3959    {
3960       *rp = (png_byte)(((int)(*rp) + (int)(*pp++)) & 0xff);
3961       rp++;
3962    }
3963 }
3964 
3965 static void
png_read_filter_row_avg(png_row_infop row_info,png_bytep row,png_const_bytep prev_row)3966 png_read_filter_row_avg(png_row_infop row_info, png_bytep row,
3967     png_const_bytep prev_row)
3968 {
3969    size_t i;
3970    png_bytep rp = row;
3971    png_const_bytep pp = prev_row;
3972    unsigned int bpp = (row_info->pixel_depth + 7) >> 3;
3973    size_t istop = row_info->rowbytes - bpp;
3974 
3975    for (i = 0; i < bpp; i++)
3976    {
3977       *rp = (png_byte)(((int)(*rp) +
3978          ((int)(*pp++) / 2 )) & 0xff);
3979 
3980       rp++;
3981    }
3982 
3983    for (i = 0; i < istop; i++)
3984    {
3985       *rp = (png_byte)(((int)(*rp) +
3986          (int)(*pp++ + *(rp-bpp)) / 2 ) & 0xff);
3987 
3988       rp++;
3989    }
3990 }
3991 
3992 static void
png_read_filter_row_paeth_1byte_pixel(png_row_infop row_info,png_bytep row,png_const_bytep prev_row)3993 png_read_filter_row_paeth_1byte_pixel(png_row_infop row_info, png_bytep row,
3994     png_const_bytep prev_row)
3995 {
3996    png_bytep rp_end = row + row_info->rowbytes;
3997    int a, c;
3998 
3999    /* First pixel/byte */
4000    c = *prev_row++;
4001    a = *row + c;
4002    *row++ = (png_byte)a;
4003 
4004    /* Remainder */
4005    while (row < rp_end)
4006    {
4007       int b, pa, pb, pc, p;
4008 
4009       a &= 0xff; /* From previous iteration or start */
4010       b = *prev_row++;
4011 
4012       p = b - c;
4013       pc = a - c;
4014 
4015 #ifdef PNG_USE_ABS
4016       pa = abs(p);
4017       pb = abs(pc);
4018       pc = abs(p + pc);
4019 #else
4020       pa = p < 0 ? -p : p;
4021       pb = pc < 0 ? -pc : pc;
4022       pc = (p + pc) < 0 ? -(p + pc) : p + pc;
4023 #endif
4024 
4025       /* Find the best predictor, the least of pa, pb, pc favoring the earlier
4026        * ones in the case of a tie.
4027        */
4028       if (pb < pa)
4029       {
4030          pa = pb; a = b;
4031       }
4032       if (pc < pa) a = c;
4033 
4034       /* Calculate the current pixel in a, and move the previous row pixel to c
4035        * for the next time round the loop
4036        */
4037       c = b;
4038       a += *row;
4039       *row++ = (png_byte)a;
4040    }
4041 }
4042 
4043 static void
png_read_filter_row_paeth_multibyte_pixel(png_row_infop row_info,png_bytep row,png_const_bytep prev_row)4044 png_read_filter_row_paeth_multibyte_pixel(png_row_infop row_info, png_bytep row,
4045     png_const_bytep prev_row)
4046 {
4047    unsigned int bpp = (row_info->pixel_depth + 7) >> 3;
4048    png_bytep rp_end = row + bpp;
4049 
4050    /* Process the first pixel in the row completely (this is the same as 'up'
4051     * because there is only one candidate predictor for the first row).
4052     */
4053    while (row < rp_end)
4054    {
4055       int a = *row + *prev_row++;
4056       *row++ = (png_byte)a;
4057    }
4058 
4059    /* Remainder */
4060    rp_end = rp_end + (row_info->rowbytes - bpp);
4061 
4062    while (row < rp_end)
4063    {
4064       int a, b, c, pa, pb, pc, p;
4065 
4066       c = *(prev_row - bpp);
4067       a = *(row - bpp);
4068       b = *prev_row++;
4069 
4070       p = b - c;
4071       pc = a - c;
4072 
4073 #ifdef PNG_USE_ABS
4074       pa = abs(p);
4075       pb = abs(pc);
4076       pc = abs(p + pc);
4077 #else
4078       pa = p < 0 ? -p : p;
4079       pb = pc < 0 ? -pc : pc;
4080       pc = (p + pc) < 0 ? -(p + pc) : p + pc;
4081 #endif
4082 
4083       if (pb < pa)
4084       {
4085          pa = pb; a = b;
4086       }
4087       if (pc < pa) a = c;
4088 
4089       a += *row;
4090       *row++ = (png_byte)a;
4091    }
4092 }
4093 
4094 static void
png_init_filter_functions(png_structrp pp)4095 png_init_filter_functions(png_structrp pp)
4096    /* This function is called once for every PNG image (except for PNG images
4097     * that only use PNG_FILTER_VALUE_NONE for all rows) to set the
4098     * implementations required to reverse the filtering of PNG rows.  Reversing
4099     * the filter is the first transformation performed on the row data.  It is
4100     * performed in place, therefore an implementation can be selected based on
4101     * the image pixel format.  If the implementation depends on image width then
4102     * take care to ensure that it works correctly if the image is interlaced -
4103     * interlacing causes the actual row width to vary.
4104     */
4105 {
4106    unsigned int bpp = (pp->pixel_depth + 7) >> 3;
4107 
4108    pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub;
4109    pp->read_filter[PNG_FILTER_VALUE_UP-1] = png_read_filter_row_up;
4110    pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg;
4111    if (bpp == 1)
4112       pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
4113          png_read_filter_row_paeth_1byte_pixel;
4114    else
4115       pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
4116          png_read_filter_row_paeth_multibyte_pixel;
4117 
4118 #ifdef PNG_FILTER_OPTIMIZATIONS
4119    /* To use this define PNG_FILTER_OPTIMIZATIONS as the name of a function to
4120     * call to install hardware optimizations for the above functions; simply
4121     * replace whatever elements of the pp->read_filter[] array with a hardware
4122     * specific (or, for that matter, generic) optimization.
4123     *
4124     * To see an example of this examine what configure.ac does when
4125     * --enable-arm-neon is specified on the command line.
4126     */
4127    PNG_FILTER_OPTIMIZATIONS(pp, bpp);
4128 #endif
4129 }
4130 
4131 void /* PRIVATE */
png_read_filter_row(png_structrp pp,png_row_infop row_info,png_bytep row,png_const_bytep prev_row,int filter)4132 png_read_filter_row(png_structrp pp, png_row_infop row_info, png_bytep row,
4133     png_const_bytep prev_row, int filter)
4134 {
4135    /* OPTIMIZATION: DO NOT MODIFY THIS FUNCTION, instead #define
4136     * PNG_FILTER_OPTIMIZATIONS to a function that overrides the generic
4137     * implementations.  See png_init_filter_functions above.
4138     */
4139    if (filter > PNG_FILTER_VALUE_NONE && filter < PNG_FILTER_VALUE_LAST)
4140    {
4141       if (pp->read_filter[0] == NULL)
4142          png_init_filter_functions(pp);
4143 
4144       pp->read_filter[filter-1](row_info, row, prev_row);
4145    }
4146 }
4147 
4148 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
4149 void /* PRIVATE */
png_read_IDAT_data(png_structrp png_ptr,png_bytep output,png_alloc_size_t avail_out)4150 png_read_IDAT_data(png_structrp png_ptr, png_bytep output,
4151     png_alloc_size_t avail_out)
4152 {
4153    /* Loop reading IDATs and decompressing the result into output[avail_out] */
4154    png_ptr->zstream.next_out = output;
4155    png_ptr->zstream.avail_out = 0; /* safety: set below */
4156 
4157    if (output == NULL)
4158       avail_out = 0;
4159 
4160    do
4161    {
4162       int ret;
4163       png_byte tmpbuf[PNG_INFLATE_BUF_SIZE];
4164 
4165       if (png_ptr->zstream.avail_in == 0)
4166       {
4167          uInt avail_in;
4168          png_bytep buffer;
4169 
4170          while (png_ptr->idat_size == 0)
4171          {
4172             png_crc_finish(png_ptr, 0);
4173 
4174             png_ptr->idat_size = png_read_chunk_header(png_ptr);
4175             /* This is an error even in the 'check' case because the code just
4176              * consumed a non-IDAT header.
4177              */
4178             if (png_ptr->chunk_name != png_IDAT)
4179                png_error(png_ptr, "Not enough image data");
4180          }
4181 
4182          avail_in = png_ptr->IDAT_read_size;
4183 
4184          if (avail_in > png_ptr->idat_size)
4185             avail_in = (uInt)png_ptr->idat_size;
4186 
4187          /* A PNG with a gradually increasing IDAT size will defeat this attempt
4188           * to minimize memory usage by causing lots of re-allocs, but
4189           * realistically doing IDAT_read_size re-allocs is not likely to be a
4190           * big problem.
4191           */
4192          buffer = png_read_buffer(png_ptr, avail_in, 0/*error*/);
4193 
4194          png_crc_read(png_ptr, buffer, avail_in);
4195          png_ptr->idat_size -= avail_in;
4196 
4197          png_ptr->zstream.next_in = buffer;
4198          png_ptr->zstream.avail_in = avail_in;
4199       }
4200 
4201       /* And set up the output side. */
4202       if (output != NULL) /* standard read */
4203       {
4204          uInt out = ZLIB_IO_MAX;
4205 
4206          if (out > avail_out)
4207             out = (uInt)avail_out;
4208 
4209          avail_out -= out;
4210          png_ptr->zstream.avail_out = out;
4211       }
4212 
4213       else /* after last row, checking for end */
4214       {
4215          png_ptr->zstream.next_out = tmpbuf;
4216          png_ptr->zstream.avail_out = (sizeof tmpbuf);
4217       }
4218 
4219       /* Use NO_FLUSH; this gives zlib the maximum opportunity to optimize the
4220        * process.  If the LZ stream is truncated the sequential reader will
4221        * terminally damage the stream, above, by reading the chunk header of the
4222        * following chunk (it then exits with png_error).
4223        *
4224        * TODO: deal more elegantly with truncated IDAT lists.
4225        */
4226       ret = PNG_INFLATE(png_ptr, Z_NO_FLUSH);
4227 
4228       /* Take the unconsumed output back. */
4229       if (output != NULL)
4230          avail_out += png_ptr->zstream.avail_out;
4231 
4232       else /* avail_out counts the extra bytes */
4233          avail_out += (sizeof tmpbuf) - png_ptr->zstream.avail_out;
4234 
4235       png_ptr->zstream.avail_out = 0;
4236 
4237       if (ret == Z_STREAM_END)
4238       {
4239          /* Do this for safety; we won't read any more into this row. */
4240          png_ptr->zstream.next_out = NULL;
4241 
4242          png_ptr->mode |= PNG_AFTER_IDAT;
4243          png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
4244 
4245          if (png_ptr->zstream.avail_in > 0 || png_ptr->idat_size > 0)
4246             png_chunk_benign_error(png_ptr, "Extra compressed data");
4247          break;
4248       }
4249 
4250       if (ret != Z_OK)
4251       {
4252          png_zstream_error(png_ptr, ret);
4253 
4254          if (output != NULL)
4255             png_chunk_error(png_ptr, png_ptr->zstream.msg);
4256 
4257          else /* checking */
4258          {
4259             png_chunk_benign_error(png_ptr, png_ptr->zstream.msg);
4260             return;
4261          }
4262       }
4263    } while (avail_out > 0);
4264 
4265    if (avail_out > 0)
4266    {
4267       /* The stream ended before the image; this is the same as too few IDATs so
4268        * should be handled the same way.
4269        */
4270       if (output != NULL)
4271          png_error(png_ptr, "Not enough image data");
4272 
4273       else /* the deflate stream contained extra data */
4274          png_chunk_benign_error(png_ptr, "Too much image data");
4275    }
4276 }
4277 
4278 void /* PRIVATE */
png_read_finish_IDAT(png_structrp png_ptr)4279 png_read_finish_IDAT(png_structrp png_ptr)
4280 {
4281    /* We don't need any more data and the stream should have ended, however the
4282     * LZ end code may actually not have been processed.  In this case we must
4283     * read it otherwise stray unread IDAT data or, more likely, an IDAT chunk
4284     * may still remain to be consumed.
4285     */
4286    if ((png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED) == 0)
4287    {
4288       /* The NULL causes png_read_IDAT_data to swallow any remaining bytes in
4289        * the compressed stream, but the stream may be damaged too, so even after
4290        * this call we may need to terminate the zstream ownership.
4291        */
4292       png_read_IDAT_data(png_ptr, NULL, 0);
4293       png_ptr->zstream.next_out = NULL; /* safety */
4294 
4295       /* Now clear everything out for safety; the following may not have been
4296        * done.
4297        */
4298       if ((png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED) == 0)
4299       {
4300          png_ptr->mode |= PNG_AFTER_IDAT;
4301          png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
4302       }
4303    }
4304 
4305    /* If the zstream has not been released do it now *and* terminate the reading
4306     * of the final IDAT chunk.
4307     */
4308    if (png_ptr->zowner == png_IDAT)
4309    {
4310       /* Always do this; the pointers otherwise point into the read buffer. */
4311       png_ptr->zstream.next_in = NULL;
4312       png_ptr->zstream.avail_in = 0;
4313 
4314       /* Now we no longer own the zstream. */
4315       png_ptr->zowner = 0;
4316 
4317       /* The slightly weird semantics of the sequential IDAT reading is that we
4318        * are always in or at the end of an IDAT chunk, so we always need to do a
4319        * crc_finish here.  If idat_size is non-zero we also need to read the
4320        * spurious bytes at the end of the chunk now.
4321        */
4322       (void)png_crc_finish(png_ptr, png_ptr->idat_size);
4323    }
4324 }
4325 
4326 void /* PRIVATE */
png_read_finish_row(png_structrp png_ptr)4327 png_read_finish_row(png_structrp png_ptr)
4328 {
4329    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
4330 
4331    /* Start of interlace block */
4332    static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
4333 
4334    /* Offset to next interlace block */
4335    static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
4336 
4337    /* Start of interlace block in the y direction */
4338    static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
4339 
4340    /* Offset to next interlace block in the y direction */
4341    static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
4342 
4343    png_debug(1, "in png_read_finish_row");
4344    png_ptr->row_number++;
4345    if (png_ptr->row_number < png_ptr->num_rows)
4346       return;
4347 
4348    if (png_ptr->interlaced != 0)
4349    {
4350       png_ptr->row_number = 0;
4351 
4352       /* TO DO: don't do this if prev_row isn't needed (requires
4353        * read-ahead of the next row's filter byte.
4354        */
4355       memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
4356 
4357       do
4358       {
4359          png_ptr->pass++;
4360 
4361          if (png_ptr->pass >= 7)
4362             break;
4363 
4364          png_ptr->iwidth = (png_ptr->width +
4365             png_pass_inc[png_ptr->pass] - 1 -
4366             png_pass_start[png_ptr->pass]) /
4367             png_pass_inc[png_ptr->pass];
4368 
4369          if ((png_ptr->transformations & PNG_INTERLACE) == 0)
4370          {
4371             png_ptr->num_rows = (png_ptr->height +
4372                 png_pass_yinc[png_ptr->pass] - 1 -
4373                 png_pass_ystart[png_ptr->pass]) /
4374                 png_pass_yinc[png_ptr->pass];
4375          }
4376 
4377          else  /* if (png_ptr->transformations & PNG_INTERLACE) */
4378             break; /* libpng deinterlacing sees every row */
4379 
4380       } while (png_ptr->num_rows == 0 || png_ptr->iwidth == 0);
4381 
4382       if (png_ptr->pass < 7)
4383          return;
4384    }
4385 
4386    /* Here after at the end of the last row of the last pass. */
4387    png_read_finish_IDAT(png_ptr);
4388 }
4389 #endif /* SEQUENTIAL_READ */
4390 
4391 void /* PRIVATE */
png_read_start_row(png_structrp png_ptr)4392 png_read_start_row(png_structrp png_ptr)
4393 {
4394    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
4395 
4396    /* Start of interlace block */
4397    static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
4398 
4399    /* Offset to next interlace block */
4400    static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
4401 
4402    /* Start of interlace block in the y direction */
4403    static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
4404 
4405    /* Offset to next interlace block in the y direction */
4406    static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
4407 
4408    unsigned int max_pixel_depth;
4409    size_t row_bytes;
4410 
4411    png_debug(1, "in png_read_start_row");
4412 
4413 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
4414    png_init_read_transformations(png_ptr);
4415 #endif
4416    if (png_ptr->interlaced != 0)
4417    {
4418       if ((png_ptr->transformations & PNG_INTERLACE) == 0)
4419          png_ptr->num_rows = (png_ptr->height + png_pass_yinc[0] - 1 -
4420              png_pass_ystart[0]) / png_pass_yinc[0];
4421 
4422       else
4423          png_ptr->num_rows = png_ptr->height;
4424 
4425       png_ptr->iwidth = (png_ptr->width +
4426           png_pass_inc[png_ptr->pass] - 1 -
4427           png_pass_start[png_ptr->pass]) /
4428           png_pass_inc[png_ptr->pass];
4429    }
4430 
4431    else
4432    {
4433       png_ptr->num_rows = png_ptr->height;
4434       png_ptr->iwidth = png_ptr->width;
4435    }
4436 
4437    max_pixel_depth = (unsigned int)png_ptr->pixel_depth;
4438 
4439    /* WARNING: * png_read_transform_info (pngrtran.c) performs a simpler set of
4440     * calculations to calculate the final pixel depth, then
4441     * png_do_read_transforms actually does the transforms.  This means that the
4442     * code which effectively calculates this value is actually repeated in three
4443     * separate places.  They must all match.  Innocent changes to the order of
4444     * transformations can and will break libpng in a way that causes memory
4445     * overwrites.
4446     *
4447     * TODO: fix this.
4448     */
4449 #ifdef PNG_READ_PACK_SUPPORTED
4450    if ((png_ptr->transformations & PNG_PACK) != 0 && png_ptr->bit_depth < 8)
4451       max_pixel_depth = 8;
4452 #endif
4453 
4454 #ifdef PNG_READ_EXPAND_SUPPORTED
4455    if ((png_ptr->transformations & PNG_EXPAND) != 0)
4456    {
4457       if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
4458       {
4459          if (png_ptr->num_trans != 0)
4460             max_pixel_depth = 32;
4461 
4462          else
4463             max_pixel_depth = 24;
4464       }
4465 
4466       else if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
4467       {
4468          if (max_pixel_depth < 8)
4469             max_pixel_depth = 8;
4470 
4471          if (png_ptr->num_trans != 0)
4472             max_pixel_depth *= 2;
4473       }
4474 
4475       else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
4476       {
4477          if (png_ptr->num_trans != 0)
4478          {
4479             max_pixel_depth *= 4;
4480             max_pixel_depth /= 3;
4481          }
4482       }
4483    }
4484 #endif
4485 
4486 #ifdef PNG_READ_EXPAND_16_SUPPORTED
4487    if ((png_ptr->transformations & PNG_EXPAND_16) != 0)
4488    {
4489 #  ifdef PNG_READ_EXPAND_SUPPORTED
4490       /* In fact it is an error if it isn't supported, but checking is
4491        * the safe way.
4492        */
4493       if ((png_ptr->transformations & PNG_EXPAND) != 0)
4494       {
4495          if (png_ptr->bit_depth < 16)
4496             max_pixel_depth *= 2;
4497       }
4498       else
4499 #  endif
4500       png_ptr->transformations &= ~PNG_EXPAND_16;
4501    }
4502 #endif
4503 
4504 #ifdef PNG_READ_FILLER_SUPPORTED
4505    if ((png_ptr->transformations & (PNG_FILLER)) != 0)
4506    {
4507       if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
4508       {
4509          if (max_pixel_depth <= 8)
4510             max_pixel_depth = 16;
4511 
4512          else
4513             max_pixel_depth = 32;
4514       }
4515 
4516       else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB ||
4517          png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
4518       {
4519          if (max_pixel_depth <= 32)
4520             max_pixel_depth = 32;
4521 
4522          else
4523             max_pixel_depth = 64;
4524       }
4525    }
4526 #endif
4527 
4528 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
4529    if ((png_ptr->transformations & PNG_GRAY_TO_RGB) != 0)
4530    {
4531       if (
4532 #ifdef PNG_READ_EXPAND_SUPPORTED
4533           (png_ptr->num_trans != 0 &&
4534           (png_ptr->transformations & PNG_EXPAND) != 0) ||
4535 #endif
4536 #ifdef PNG_READ_FILLER_SUPPORTED
4537           (png_ptr->transformations & (PNG_FILLER)) != 0 ||
4538 #endif
4539           png_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
4540       {
4541          if (max_pixel_depth <= 16)
4542             max_pixel_depth = 32;
4543 
4544          else
4545             max_pixel_depth = 64;
4546       }
4547 
4548       else
4549       {
4550          if (max_pixel_depth <= 8)
4551          {
4552             if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
4553                max_pixel_depth = 32;
4554 
4555             else
4556                max_pixel_depth = 24;
4557          }
4558 
4559          else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
4560             max_pixel_depth = 64;
4561 
4562          else
4563             max_pixel_depth = 48;
4564       }
4565    }
4566 #endif
4567 
4568 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) && \
4569 defined(PNG_USER_TRANSFORM_PTR_SUPPORTED)
4570    if ((png_ptr->transformations & PNG_USER_TRANSFORM) != 0)
4571    {
4572       unsigned int user_pixel_depth = png_ptr->user_transform_depth *
4573          png_ptr->user_transform_channels;
4574 
4575       if (user_pixel_depth > max_pixel_depth)
4576          max_pixel_depth = user_pixel_depth;
4577    }
4578 #endif
4579 
4580    /* This value is stored in png_struct and double checked in the row read
4581     * code.
4582     */
4583    png_ptr->maximum_pixel_depth = (png_byte)max_pixel_depth;
4584    png_ptr->transformed_pixel_depth = 0; /* calculated on demand */
4585 
4586    /* Align the width on the next larger 8 pixels.  Mainly used
4587     * for interlacing
4588     */
4589    row_bytes = ((png_ptr->width + 7) & ~((png_uint_32)7));
4590    /* Calculate the maximum bytes needed, adding a byte and a pixel
4591     * for safety's sake
4592     */
4593    row_bytes = PNG_ROWBYTES(max_pixel_depth, row_bytes) +
4594        1 + ((max_pixel_depth + 7) >> 3U);
4595 
4596 #ifdef PNG_MAX_MALLOC_64K
4597    if (row_bytes > (png_uint_32)65536L)
4598       png_error(png_ptr, "This image requires a row greater than 64KB");
4599 #endif
4600 
4601    if (row_bytes + 48 > png_ptr->old_big_row_buf_size)
4602    {
4603       png_free(png_ptr, png_ptr->big_row_buf);
4604       png_free(png_ptr, png_ptr->big_prev_row);
4605 
4606       if (png_ptr->interlaced != 0)
4607          png_ptr->big_row_buf = (png_bytep)png_calloc(png_ptr,
4608              row_bytes + 48);
4609 
4610       else
4611          png_ptr->big_row_buf = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
4612 
4613       png_ptr->big_prev_row = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
4614 
4615 #ifdef PNG_ALIGNED_MEMORY_SUPPORTED
4616       /* Use 16-byte aligned memory for row_buf with at least 16 bytes
4617        * of padding before and after row_buf; treat prev_row similarly.
4618        * NOTE: the alignment is to the start of the pixels, one beyond the start
4619        * of the buffer, because of the filter byte.  Prior to libpng 1.5.6 this
4620        * was incorrect; the filter byte was aligned, which had the exact
4621        * opposite effect of that intended.
4622        */
4623       {
4624          png_bytep temp = png_ptr->big_row_buf + 32;
4625          int extra = (int)((temp - (png_bytep)0) & 0x0f);
4626          png_ptr->row_buf = temp - extra - 1/*filter byte*/;
4627 
4628          temp = png_ptr->big_prev_row + 32;
4629          extra = (int)((temp - (png_bytep)0) & 0x0f);
4630          png_ptr->prev_row = temp - extra - 1/*filter byte*/;
4631       }
4632 
4633 #else
4634       /* Use 31 bytes of padding before and 17 bytes after row_buf. */
4635       png_ptr->row_buf = png_ptr->big_row_buf + 31;
4636       png_ptr->prev_row = png_ptr->big_prev_row + 31;
4637 #endif
4638       png_ptr->old_big_row_buf_size = row_bytes + 48;
4639    }
4640 
4641 #ifdef PNG_MAX_MALLOC_64K
4642    if (png_ptr->rowbytes > 65535)
4643       png_error(png_ptr, "This image requires a row greater than 64KB");
4644 
4645 #endif
4646    if (png_ptr->rowbytes > (PNG_SIZE_MAX - 1))
4647       png_error(png_ptr, "Row has too many bytes to allocate in memory");
4648 
4649    memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
4650 
4651    png_debug1(3, "width = %u,", png_ptr->width);
4652    png_debug1(3, "height = %u,", png_ptr->height);
4653    png_debug1(3, "iwidth = %u,", png_ptr->iwidth);
4654    png_debug1(3, "num_rows = %u,", png_ptr->num_rows);
4655    png_debug1(3, "rowbytes = %lu,", (unsigned long)png_ptr->rowbytes);
4656    png_debug1(3, "irowbytes = %lu",
4657        (unsigned long)PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->iwidth) + 1);
4658 
4659    /* The sequential reader needs a buffer for IDAT, but the progressive reader
4660     * does not, so free the read buffer now regardless; the sequential reader
4661     * reallocates it on demand.
4662     */
4663    if (png_ptr->read_buffer != NULL)
4664    {
4665       png_bytep buffer = png_ptr->read_buffer;
4666 
4667       png_ptr->read_buffer_size = 0;
4668       png_ptr->read_buffer = NULL;
4669       png_free(png_ptr, buffer);
4670    }
4671 
4672    /* Finally claim the zstream for the inflate of the IDAT data, use the bits
4673     * value from the stream (note that this will result in a fatal error if the
4674     * IDAT stream has a bogus deflate header window_bits value, but this should
4675     * not be happening any longer!)
4676     */
4677    if (png_inflate_claim(png_ptr, png_IDAT) != Z_OK)
4678       png_error(png_ptr, png_ptr->zstream.msg);
4679 
4680    png_ptr->flags |= PNG_FLAG_ROW_INIT;
4681 }
4682 #endif /* READ */
4683