1 
2 /* pngerror.c - stub functions for i/o and memory allocation
3  *
4  * Copyright (c) 2018 Cosmin Truta
5  * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
6  * Copyright (c) 1996-1997 Andreas Dilger
7  * 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 provides a location for all error handling.  Users who
14  * need special error handling are expected to write replacement functions
15  * and use png_set_error_fn() to use those functions.  See the instructions
16  * at each function.
17  */
18 
19 #include "pngpriv.h"
20 
21 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
22 
23 static PNG_FUNCTION(void, png_default_error,PNGARG((png_const_structrp png_ptr,
24     png_const_charp error_message)),PNG_NORETURN);
25 
26 #ifdef PNG_WARNINGS_SUPPORTED
27 static void /* PRIVATE */
28 png_default_warning PNGARG((png_const_structrp png_ptr,
29     png_const_charp warning_message));
30 #endif /* WARNINGS */
31 
32 /* This function is called whenever there is a fatal error.  This function
33  * should not be changed.  If there is a need to handle errors differently,
34  * you should supply a replacement error function and use png_set_error_fn()
35  * to replace the error function at run-time.
36  */
37 #ifdef PNG_ERROR_TEXT_SUPPORTED
38 PNG_FUNCTION(void,PNGAPI
39 png_error,(png_const_structrp png_ptr, png_const_charp error_message),
40     PNG_NORETURN)
41 {
42 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
43    char msg[16];
44    if (png_ptr != NULL)
45    {
46       if ((png_ptr->flags &
47          (PNG_FLAG_STRIP_ERROR_NUMBERS|PNG_FLAG_STRIP_ERROR_TEXT)) != 0)
48       {
49          if (*error_message == PNG_LITERAL_SHARP)
50          {
51             /* Strip "#nnnn " from beginning of error message. */
52             int offset;
53             for (offset = 1; offset<15; offset++)
54                if (error_message[offset] == ' ')
55                   break;
56 
57             if ((png_ptr->flags & PNG_FLAG_STRIP_ERROR_TEXT) != 0)
58             {
59                int i;
60                for (i = 0; i < offset - 1; i++)
61                   msg[i] = error_message[i + 1];
62                msg[i - 1] = '\0';
63                error_message = msg;
64             }
65 
66             else
67                error_message += offset;
68          }
69 
70          else
71          {
72             if ((png_ptr->flags & PNG_FLAG_STRIP_ERROR_TEXT) != 0)
73             {
74                msg[0] = '0';
75                msg[1] = '\0';
76                error_message = msg;
77             }
78          }
79       }
80    }
81 #endif
82    if (png_ptr != NULL && png_ptr->error_fn != NULL)
83       (*(png_ptr->error_fn))(png_constcast(png_structrp,png_ptr),
84           error_message);
85 
86    /* If the custom handler doesn't exist, or if it returns,
87       use the default handler, which will not return. */
88    png_default_error(png_ptr, error_message);
89 }
90 #else
91 PNG_FUNCTION(void,PNGAPI
92 png_err,(png_const_structrp png_ptr),PNG_NORETURN)
93 {
94    /* Prior to 1.5.2 the error_fn received a NULL pointer, expressed
95     * erroneously as '\0', instead of the empty string "".  This was
96     * apparently an error, introduced in libpng-1.2.20, and png_default_error
97     * will crash in this case.
98     */
99    if (png_ptr != NULL && png_ptr->error_fn != NULL)
100       (*(png_ptr->error_fn))(png_constcast(png_structrp,png_ptr), "");
101 
102    /* If the custom handler doesn't exist, or if it returns,
103       use the default handler, which will not return. */
104    png_default_error(png_ptr, "");
105 }
106 #endif /* ERROR_TEXT */
107 
108 /* Utility to safely appends strings to a buffer.  This never errors out so
109  * error checking is not required in the caller.
110  */
111 size_t
png_safecat(png_charp buffer,size_t bufsize,size_t pos,png_const_charp string)112 png_safecat(png_charp buffer, size_t bufsize, size_t pos,
113     png_const_charp string)
114 {
115    if (buffer != NULL && pos < bufsize)
116    {
117       if (string != NULL)
118          while (*string != '\0' && pos < bufsize-1)
119            buffer[pos++] = *string++;
120 
121       buffer[pos] = '\0';
122    }
123 
124    return pos;
125 }
126 
127 #if defined(PNG_WARNINGS_SUPPORTED) || defined(PNG_TIME_RFC1123_SUPPORTED)
128 /* Utility to dump an unsigned value into a buffer, given a start pointer and
129  * and end pointer (which should point just *beyond* the end of the buffer!)
130  * Returns the pointer to the start of the formatted string.
131  */
132 png_charp
png_format_number(png_const_charp start,png_charp end,int format,png_alloc_size_t number)133 png_format_number(png_const_charp start, png_charp end, int format,
134     png_alloc_size_t number)
135 {
136    int count = 0;    /* number of digits output */
137    int mincount = 1; /* minimum number required */
138    int output = 0;   /* digit output (for the fixed point format) */
139 
140    *--end = '\0';
141 
142    /* This is written so that the loop always runs at least once, even with
143     * number zero.
144     */
145    while (end > start && (number != 0 || count < mincount))
146    {
147 
148       static const char digits[] = "0123456789ABCDEF";
149 
150       switch (format)
151       {
152          case PNG_NUMBER_FORMAT_fixed:
153             /* Needs five digits (the fraction) */
154             mincount = 5;
155             if (output != 0 || number % 10 != 0)
156             {
157                *--end = digits[number % 10];
158                output = 1;
159             }
160             number /= 10;
161             break;
162 
163          case PNG_NUMBER_FORMAT_02u:
164             /* Expects at least 2 digits. */
165             mincount = 2;
166             /* FALLTHROUGH */
167 
168          case PNG_NUMBER_FORMAT_u:
169             *--end = digits[number % 10];
170             number /= 10;
171             break;
172 
173          case PNG_NUMBER_FORMAT_02x:
174             /* This format expects at least two digits */
175             mincount = 2;
176             /* FALLTHROUGH */
177 
178          case PNG_NUMBER_FORMAT_x:
179             *--end = digits[number & 0xf];
180             number >>= 4;
181             break;
182 
183          default: /* an error */
184             number = 0;
185             break;
186       }
187 
188       /* Keep track of the number of digits added */
189       ++count;
190 
191       /* Float a fixed number here: */
192       if ((format == PNG_NUMBER_FORMAT_fixed) && (count == 5) && (end > start))
193       {
194          /* End of the fraction, but maybe nothing was output?  In that case
195           * drop the decimal point.  If the number is a true zero handle that
196           * here.
197           */
198          if (output != 0)
199             *--end = '.';
200          else if (number == 0) /* and !output */
201             *--end = '0';
202       }
203    }
204 
205    return end;
206 }
207 #endif
208 
209 #ifdef PNG_WARNINGS_SUPPORTED
210 /* This function is called whenever there is a non-fatal error.  This function
211  * should not be changed.  If there is a need to handle warnings differently,
212  * you should supply a replacement warning function and use
213  * png_set_error_fn() to replace the warning function at run-time.
214  */
215 void PNGAPI
png_warning(png_const_structrp png_ptr,png_const_charp warning_message)216 png_warning(png_const_structrp png_ptr, png_const_charp warning_message)
217 {
218    int offset = 0;
219    if (png_ptr != NULL)
220    {
221 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
222    if ((png_ptr->flags &
223        (PNG_FLAG_STRIP_ERROR_NUMBERS|PNG_FLAG_STRIP_ERROR_TEXT)) != 0)
224 #endif
225       {
226          if (*warning_message == PNG_LITERAL_SHARP)
227          {
228             for (offset = 1; offset < 15; offset++)
229                if (warning_message[offset] == ' ')
230                   break;
231          }
232       }
233    }
234    if (png_ptr != NULL && png_ptr->warning_fn != NULL)
235       (*(png_ptr->warning_fn))(png_constcast(png_structrp,png_ptr),
236           warning_message + offset);
237    else
238       png_default_warning(png_ptr, warning_message + offset);
239 }
240 
241 /* These functions support 'formatted' warning messages with up to
242  * PNG_WARNING_PARAMETER_COUNT parameters.  In the format string the parameter
243  * is introduced by @<number>, where 'number' starts at 1.  This follows the
244  * standard established by X/Open for internationalizable error messages.
245  */
246 void
png_warning_parameter(png_warning_parameters p,int number,png_const_charp string)247 png_warning_parameter(png_warning_parameters p, int number,
248     png_const_charp string)
249 {
250    if (number > 0 && number <= PNG_WARNING_PARAMETER_COUNT)
251       (void)png_safecat(p[number-1], (sizeof p[number-1]), 0, string);
252 }
253 
254 void
png_warning_parameter_unsigned(png_warning_parameters p,int number,int format,png_alloc_size_t value)255 png_warning_parameter_unsigned(png_warning_parameters p, int number, int format,
256     png_alloc_size_t value)
257 {
258    char buffer[PNG_NUMBER_BUFFER_SIZE];
259    png_warning_parameter(p, number, PNG_FORMAT_NUMBER(buffer, format, value));
260 }
261 
262 void
png_warning_parameter_signed(png_warning_parameters p,int number,int format,png_int_32 value)263 png_warning_parameter_signed(png_warning_parameters p, int number, int format,
264     png_int_32 value)
265 {
266    png_alloc_size_t u;
267    png_charp str;
268    char buffer[PNG_NUMBER_BUFFER_SIZE];
269 
270    /* Avoid overflow by doing the negate in a png_alloc_size_t: */
271    u = (png_alloc_size_t)value;
272    if (value < 0)
273       u = ~u + 1;
274 
275    str = PNG_FORMAT_NUMBER(buffer, format, u);
276 
277    if (value < 0 && str > buffer)
278       *--str = '-';
279 
280    png_warning_parameter(p, number, str);
281 }
282 
283 void
png_formatted_warning(png_const_structrp png_ptr,png_warning_parameters p,png_const_charp message)284 png_formatted_warning(png_const_structrp png_ptr, png_warning_parameters p,
285     png_const_charp message)
286 {
287    /* The internal buffer is just 192 bytes - enough for all our messages,
288     * overflow doesn't happen because this code checks!  If someone figures
289     * out how to send us a message longer than 192 bytes, all that will
290     * happen is that the message will be truncated appropriately.
291     */
292    size_t i = 0; /* Index in the msg[] buffer: */
293    char msg[192];
294 
295    /* Each iteration through the following loop writes at most one character
296     * to msg[i++] then returns here to validate that there is still space for
297     * the trailing '\0'.  It may (in the case of a parameter) read more than
298     * one character from message[]; it must check for '\0' and continue to the
299     * test if it finds the end of string.
300     */
301    while (i<(sizeof msg)-1 && *message != '\0')
302    {
303       /* '@' at end of string is now just printed (previously it was skipped);
304        * it is an error in the calling code to terminate the string with @.
305        */
306       if (p != NULL && *message == '@' && message[1] != '\0')
307       {
308          int parameter_char = *++message; /* Consume the '@' */
309          static const char valid_parameters[] = "123456789";
310          int parameter = 0;
311 
312          /* Search for the parameter digit, the index in the string is the
313           * parameter to use.
314           */
315          while (valid_parameters[parameter] != parameter_char &&
316             valid_parameters[parameter] != '\0')
317             ++parameter;
318 
319          /* If the parameter digit is out of range it will just get printed. */
320          if (parameter < PNG_WARNING_PARAMETER_COUNT)
321          {
322             /* Append this parameter */
323             png_const_charp parm = p[parameter];
324             png_const_charp pend = p[parameter] + (sizeof p[parameter]);
325 
326             /* No need to copy the trailing '\0' here, but there is no guarantee
327              * that parm[] has been initialized, so there is no guarantee of a
328              * trailing '\0':
329              */
330             while (i<(sizeof msg)-1 && *parm != '\0' && parm < pend)
331                msg[i++] = *parm++;
332 
333             /* Consume the parameter digit too: */
334             ++message;
335             continue;
336          }
337 
338          /* else not a parameter and there is a character after the @ sign; just
339           * copy that.  This is known not to be '\0' because of the test above.
340           */
341       }
342 
343       /* At this point *message can't be '\0', even in the bad parameter case
344        * above where there is a lone '@' at the end of the message string.
345        */
346       msg[i++] = *message++;
347    }
348 
349    /* i is always less than (sizeof msg), so: */
350    msg[i] = '\0';
351 
352    /* And this is the formatted message. It may be larger than
353     * PNG_MAX_ERROR_TEXT, but that is only used for 'chunk' errors and these
354     * are not (currently) formatted.
355     */
356    png_warning(png_ptr, msg);
357 }
358 #endif /* WARNINGS */
359 
360 #ifdef PNG_BENIGN_ERRORS_SUPPORTED
361 void PNGAPI
png_benign_error(png_const_structrp png_ptr,png_const_charp error_message)362 png_benign_error(png_const_structrp png_ptr, png_const_charp error_message)
363 {
364    if ((png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN) != 0)
365    {
366 #     ifdef PNG_READ_SUPPORTED
367          if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
368             png_ptr->chunk_name != 0)
369             png_chunk_warning(png_ptr, error_message);
370          else
371 #     endif
372       png_warning(png_ptr, error_message);
373    }
374 
375    else
376    {
377 #     ifdef PNG_READ_SUPPORTED
378          if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
379             png_ptr->chunk_name != 0)
380             png_chunk_error(png_ptr, error_message);
381          else
382 #     endif
383       png_error(png_ptr, error_message);
384    }
385 
386 #  ifndef PNG_ERROR_TEXT_SUPPORTED
387       PNG_UNUSED(error_message)
388 #  endif
389 }
390 
391 void /* PRIVATE */
png_app_warning(png_const_structrp png_ptr,png_const_charp error_message)392 png_app_warning(png_const_structrp png_ptr, png_const_charp error_message)
393 {
394    if ((png_ptr->flags & PNG_FLAG_APP_WARNINGS_WARN) != 0)
395       png_warning(png_ptr, error_message);
396    else
397       png_error(png_ptr, error_message);
398 
399 #  ifndef PNG_ERROR_TEXT_SUPPORTED
400       PNG_UNUSED(error_message)
401 #  endif
402 }
403 
404 void /* PRIVATE */
png_app_error(png_const_structrp png_ptr,png_const_charp error_message)405 png_app_error(png_const_structrp png_ptr, png_const_charp error_message)
406 {
407    if ((png_ptr->flags & PNG_FLAG_APP_ERRORS_WARN) != 0)
408       png_warning(png_ptr, error_message);
409    else
410       png_error(png_ptr, error_message);
411 
412 #  ifndef PNG_ERROR_TEXT_SUPPORTED
413       PNG_UNUSED(error_message)
414 #  endif
415 }
416 #endif /* BENIGN_ERRORS */
417 
418 #define PNG_MAX_ERROR_TEXT 196 /* Currently limited by profile_error in png.c */
419 #if defined(PNG_WARNINGS_SUPPORTED) || \
420    (defined(PNG_READ_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED))
421 /* These utilities are used internally to build an error message that relates
422  * to the current chunk.  The chunk name comes from png_ptr->chunk_name,
423  * which is used to prefix the message.  The message is limited in length
424  * to 63 bytes. The name characters are output as hex digits wrapped in []
425  * if the character is invalid.
426  */
427 #define isnonalpha(c) ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97))
428 static const char png_digit[16] = {
429    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
430    'A', 'B', 'C', 'D', 'E', 'F'
431 };
432 
433 static void /* PRIVATE */
png_format_buffer(png_const_structrp png_ptr,png_charp buffer,png_const_charp error_message)434 png_format_buffer(png_const_structrp png_ptr, png_charp buffer, png_const_charp
435     error_message)
436 {
437    png_uint_32 chunk_name = png_ptr->chunk_name;
438    int iout = 0, ishift = 24;
439 
440    while (ishift >= 0)
441    {
442       int c = (int)(chunk_name >> ishift) & 0xff;
443 
444       ishift -= 8;
445       if (isnonalpha(c) != 0)
446       {
447          buffer[iout++] = PNG_LITERAL_LEFT_SQUARE_BRACKET;
448          buffer[iout++] = png_digit[(c & 0xf0) >> 4];
449          buffer[iout++] = png_digit[c & 0x0f];
450          buffer[iout++] = PNG_LITERAL_RIGHT_SQUARE_BRACKET;
451       }
452 
453       else
454       {
455          buffer[iout++] = (char)c;
456       }
457    }
458 
459    if (error_message == NULL)
460       buffer[iout] = '\0';
461 
462    else
463    {
464       int iin = 0;
465 
466       buffer[iout++] = ':';
467       buffer[iout++] = ' ';
468 
469       while (iin < PNG_MAX_ERROR_TEXT-1 && error_message[iin] != '\0')
470          buffer[iout++] = error_message[iin++];
471 
472       /* iin < PNG_MAX_ERROR_TEXT, so the following is safe: */
473       buffer[iout] = '\0';
474    }
475 }
476 #endif /* WARNINGS || ERROR_TEXT */
477 
478 #if defined(PNG_READ_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED)
479 PNG_FUNCTION(void,PNGAPI
480 png_chunk_error,(png_const_structrp png_ptr, png_const_charp error_message),
481     PNG_NORETURN)
482 {
483    char msg[18+PNG_MAX_ERROR_TEXT];
484    if (png_ptr == NULL)
485       png_error(png_ptr, error_message);
486 
487    else
488    {
489       png_format_buffer(png_ptr, msg, error_message);
490       png_error(png_ptr, msg);
491    }
492 }
493 #endif /* READ && ERROR_TEXT */
494 
495 #ifdef PNG_WARNINGS_SUPPORTED
496 void PNGAPI
png_chunk_warning(png_const_structrp png_ptr,png_const_charp warning_message)497 png_chunk_warning(png_const_structrp png_ptr, png_const_charp warning_message)
498 {
499    char msg[18+PNG_MAX_ERROR_TEXT];
500    if (png_ptr == NULL)
501       png_warning(png_ptr, warning_message);
502 
503    else
504    {
505       png_format_buffer(png_ptr, msg, warning_message);
506       png_warning(png_ptr, msg);
507    }
508 }
509 #endif /* WARNINGS */
510 
511 #ifdef PNG_READ_SUPPORTED
512 #ifdef PNG_BENIGN_ERRORS_SUPPORTED
513 void PNGAPI
png_chunk_benign_error(png_const_structrp png_ptr,png_const_charp error_message)514 png_chunk_benign_error(png_const_structrp png_ptr, png_const_charp
515     error_message)
516 {
517    if ((png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN) != 0)
518       png_chunk_warning(png_ptr, error_message);
519 
520    else
521       png_chunk_error(png_ptr, error_message);
522 
523 #  ifndef PNG_ERROR_TEXT_SUPPORTED
524       PNG_UNUSED(error_message)
525 #  endif
526 }
527 #endif
528 #endif /* READ */
529 
530 void /* PRIVATE */
png_chunk_report(png_const_structrp png_ptr,png_const_charp message,int error)531 png_chunk_report(png_const_structrp png_ptr, png_const_charp message, int error)
532 {
533 #  ifndef PNG_WARNINGS_SUPPORTED
534       PNG_UNUSED(message)
535 #  endif
536 
537    /* This is always supported, but for just read or just write it
538     * unconditionally does the right thing.
539     */
540 #  if defined(PNG_READ_SUPPORTED) && defined(PNG_WRITE_SUPPORTED)
541       if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0)
542 #  endif
543 
544 #  ifdef PNG_READ_SUPPORTED
545       {
546          if (error < PNG_CHUNK_ERROR)
547             png_chunk_warning(png_ptr, message);
548 
549          else
550             png_chunk_benign_error(png_ptr, message);
551       }
552 #  endif
553 
554 #  if defined(PNG_READ_SUPPORTED) && defined(PNG_WRITE_SUPPORTED)
555       else if ((png_ptr->mode & PNG_IS_READ_STRUCT) == 0)
556 #  endif
557 
558 #  ifdef PNG_WRITE_SUPPORTED
559       {
560          if (error < PNG_CHUNK_WRITE_ERROR)
561             png_app_warning(png_ptr, message);
562 
563          else
564             png_app_error(png_ptr, message);
565       }
566 #  endif
567 }
568 
569 #ifdef PNG_ERROR_TEXT_SUPPORTED
570 #ifdef PNG_FLOATING_POINT_SUPPORTED
571 PNG_FUNCTION(void,
572 png_fixed_error,(png_const_structrp png_ptr, png_const_charp name),PNG_NORETURN)
573 {
574 #  define fixed_message "fixed point overflow in "
575 #  define fixed_message_ln ((sizeof fixed_message)-1)
576    unsigned int  iin;
577    char msg[fixed_message_ln+PNG_MAX_ERROR_TEXT];
578    memcpy(msg, fixed_message, fixed_message_ln);
579    iin = 0;
580    if (name != NULL)
581       while (iin < (PNG_MAX_ERROR_TEXT-1) && name[iin] != 0)
582       {
583          msg[fixed_message_ln + iin] = name[iin];
584          ++iin;
585       }
586    msg[fixed_message_ln + iin] = 0;
587    png_error(png_ptr, msg);
588 }
589 #endif
590 #endif
591 
592 #ifdef PNG_SETJMP_SUPPORTED
593 /* This API only exists if ANSI-C style error handling is used,
594  * otherwise it is necessary for png_default_error to be overridden.
595  */
596 jmp_buf* PNGAPI
png_set_longjmp_fn(png_structrp png_ptr,png_longjmp_ptr longjmp_fn,size_t jmp_buf_size)597 png_set_longjmp_fn(png_structrp png_ptr, png_longjmp_ptr longjmp_fn,
598     size_t jmp_buf_size)
599 {
600    /* From libpng 1.6.0 the app gets one chance to set a 'jmpbuf_size' value
601     * and it must not change after that.  Libpng doesn't care how big the
602     * buffer is, just that it doesn't change.
603     *
604     * If the buffer size is no *larger* than the size of jmp_buf when libpng is
605     * compiled a built in jmp_buf is returned; this preserves the pre-1.6.0
606     * semantics that this call will not fail.  If the size is larger, however,
607     * the buffer is allocated and this may fail, causing the function to return
608     * NULL.
609     */
610    if (png_ptr == NULL)
611       return NULL;
612 
613    if (png_ptr->jmp_buf_ptr == NULL)
614    {
615       png_ptr->jmp_buf_size = 0; /* not allocated */
616 
617       if (jmp_buf_size <= (sizeof png_ptr->jmp_buf_local))
618          png_ptr->jmp_buf_ptr = &png_ptr->jmp_buf_local;
619 
620       else
621       {
622          png_ptr->jmp_buf_ptr = png_voidcast(jmp_buf *,
623              png_malloc_warn(png_ptr, jmp_buf_size));
624 
625          if (png_ptr->jmp_buf_ptr == NULL)
626             return NULL; /* new NULL return on OOM */
627 
628          png_ptr->jmp_buf_size = jmp_buf_size;
629       }
630    }
631 
632    else /* Already allocated: check the size */
633    {
634       size_t size = png_ptr->jmp_buf_size;
635 
636       if (size == 0)
637       {
638          size = (sizeof png_ptr->jmp_buf_local);
639          if (png_ptr->jmp_buf_ptr != &png_ptr->jmp_buf_local)
640          {
641             /* This is an internal error in libpng: somehow we have been left
642              * with a stack allocated jmp_buf when the application regained
643              * control.  It's always possible to fix this up, but for the moment
644              * this is a png_error because that makes it easy to detect.
645              */
646             png_error(png_ptr, "Libpng jmp_buf still allocated");
647             /* png_ptr->jmp_buf_ptr = &png_ptr->jmp_buf_local; */
648          }
649       }
650 
651       if (size != jmp_buf_size)
652       {
653          png_warning(png_ptr, "Application jmp_buf size changed");
654          return NULL; /* caller will probably crash: no choice here */
655       }
656    }
657 
658    /* Finally fill in the function, now we have a satisfactory buffer. It is
659     * valid to change the function on every call.
660     */
661    png_ptr->longjmp_fn = longjmp_fn;
662    return png_ptr->jmp_buf_ptr;
663 }
664 
665 void /* PRIVATE */
png_free_jmpbuf(png_structrp png_ptr)666 png_free_jmpbuf(png_structrp png_ptr)
667 {
668    if (png_ptr != NULL)
669    {
670       jmp_buf *jb = png_ptr->jmp_buf_ptr;
671 
672       /* A size of 0 is used to indicate a local, stack, allocation of the
673        * pointer; used here and in png.c
674        */
675       if (jb != NULL && png_ptr->jmp_buf_size > 0)
676       {
677 
678          /* This stuff is so that a failure to free the error control structure
679           * does not leave libpng in a state with no valid error handling: the
680           * free always succeeds, if there is an error it gets ignored.
681           */
682          if (jb != &png_ptr->jmp_buf_local)
683          {
684             /* Make an internal, libpng, jmp_buf to return here */
685             jmp_buf free_jmp_buf;
686 
687             if (!setjmp(free_jmp_buf))
688             {
689                png_ptr->jmp_buf_ptr = &free_jmp_buf; /* come back here */
690                png_ptr->jmp_buf_size = 0; /* stack allocation */
691                png_ptr->longjmp_fn = longjmp;
692                png_free(png_ptr, jb); /* Return to setjmp on error */
693             }
694          }
695       }
696 
697       /* *Always* cancel everything out: */
698       png_ptr->jmp_buf_size = 0;
699       png_ptr->jmp_buf_ptr = NULL;
700       png_ptr->longjmp_fn = 0;
701    }
702 }
703 #endif
704 
705 /* This is the default error handling function.  Note that replacements for
706  * this function MUST NOT RETURN, or the program will likely crash.  This
707  * function is used by default, or if the program supplies NULL for the
708  * error function pointer in png_set_error_fn().
709  */
710 static PNG_FUNCTION(void /* PRIVATE */,
711 png_default_error,(png_const_structrp png_ptr, png_const_charp error_message),
712     PNG_NORETURN)
713 {
714 #ifdef PNG_CONSOLE_IO_SUPPORTED
715 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
716    /* Check on NULL only added in 1.5.4 */
717    if (error_message != NULL && *error_message == PNG_LITERAL_SHARP)
718    {
719       /* Strip "#nnnn " from beginning of error message. */
720       int offset;
721       char error_number[16];
722       for (offset = 0; offset<15; offset++)
723       {
724          error_number[offset] = error_message[offset + 1];
725          if (error_message[offset] == ' ')
726             break;
727       }
728 
729       if ((offset > 1) && (offset < 15))
730       {
731          error_number[offset - 1] = '\0';
732          fprintf(stderr, "libpng error no. %s: %s",
733              error_number, error_message + offset + 1);
734          fprintf(stderr, PNG_STRING_NEWLINE);
735       }
736 
737       else
738       {
739          fprintf(stderr, "libpng error: %s, offset=%d",
740              error_message, offset);
741          fprintf(stderr, PNG_STRING_NEWLINE);
742       }
743    }
744    else
745 #endif
746    {
747       fprintf(stderr, "libpng error: %s", error_message ? error_message :
748          "undefined");
749       fprintf(stderr, PNG_STRING_NEWLINE);
750    }
751 #else
752    PNG_UNUSED(error_message) /* Make compiler happy */
753 #endif
754    png_longjmp(png_ptr, 1);
755 }
756 
757 PNG_FUNCTION(void,PNGAPI
758 png_longjmp,(png_const_structrp png_ptr, int val),PNG_NORETURN)
759 {
760 #ifdef PNG_SETJMP_SUPPORTED
761    if (png_ptr != NULL && png_ptr->longjmp_fn != NULL &&
762        png_ptr->jmp_buf_ptr != NULL)
763       png_ptr->longjmp_fn(*png_ptr->jmp_buf_ptr, val);
764 #else
765    PNG_UNUSED(png_ptr)
766    PNG_UNUSED(val)
767 #endif
768 
769    /* If control reaches this point, png_longjmp() must not return. The only
770     * choice is to terminate the whole process (or maybe the thread); to do
771     * this the ANSI-C abort() function is used unless a different method is
772     * implemented by overriding the default configuration setting for
773     * PNG_ABORT().
774     */
775    PNG_ABORT();
776 }
777 
778 #ifdef PNG_WARNINGS_SUPPORTED
779 /* This function is called when there is a warning, but the library thinks
780  * it can continue anyway.  Replacement functions don't have to do anything
781  * here if you don't want them to.  In the default configuration, png_ptr is
782  * not used, but it is passed in case it may be useful.
783  */
784 static void /* PRIVATE */
png_default_warning(png_const_structrp png_ptr,png_const_charp warning_message)785 png_default_warning(png_const_structrp png_ptr, png_const_charp warning_message)
786 {
787 #ifdef PNG_CONSOLE_IO_SUPPORTED
788 #  ifdef PNG_ERROR_NUMBERS_SUPPORTED
789    if (*warning_message == PNG_LITERAL_SHARP)
790    {
791       int offset;
792       char warning_number[16];
793       for (offset = 0; offset < 15; offset++)
794       {
795          warning_number[offset] = warning_message[offset + 1];
796          if (warning_message[offset] == ' ')
797             break;
798       }
799 
800       if ((offset > 1) && (offset < 15))
801       {
802          warning_number[offset + 1] = '\0';
803          fprintf(stderr, "libpng warning no. %s: %s",
804              warning_number, warning_message + offset);
805          fprintf(stderr, PNG_STRING_NEWLINE);
806       }
807 
808       else
809       {
810          fprintf(stderr, "libpng warning: %s",
811              warning_message);
812          fprintf(stderr, PNG_STRING_NEWLINE);
813       }
814    }
815    else
816 #  endif
817 
818    {
819       fprintf(stderr, "libpng warning: %s", warning_message);
820       fprintf(stderr, PNG_STRING_NEWLINE);
821    }
822 #else
823    PNG_UNUSED(warning_message) /* Make compiler happy */
824 #endif
825    PNG_UNUSED(png_ptr) /* Make compiler happy */
826 }
827 #endif /* WARNINGS */
828 
829 /* This function is called when the application wants to use another method
830  * of handling errors and warnings.  Note that the error function MUST NOT
831  * return to the calling routine or serious problems will occur.  The return
832  * method used in the default routine calls longjmp(png_ptr->jmp_buf_ptr, 1)
833  */
834 void PNGAPI
png_set_error_fn(png_structrp png_ptr,png_voidp error_ptr,png_error_ptr error_fn,png_error_ptr warning_fn)835 png_set_error_fn(png_structrp png_ptr, png_voidp error_ptr,
836     png_error_ptr error_fn, png_error_ptr warning_fn)
837 {
838    if (png_ptr == NULL)
839       return;
840 
841    png_ptr->error_ptr = error_ptr;
842    png_ptr->error_fn = error_fn;
843 #ifdef PNG_WARNINGS_SUPPORTED
844    png_ptr->warning_fn = warning_fn;
845 #else
846    PNG_UNUSED(warning_fn)
847 #endif
848 }
849 
850 
851 /* This function returns a pointer to the error_ptr associated with the user
852  * functions.  The application should free any memory associated with this
853  * pointer before png_write_destroy and png_read_destroy are called.
854  */
855 png_voidp PNGAPI
png_get_error_ptr(png_const_structrp png_ptr)856 png_get_error_ptr(png_const_structrp png_ptr)
857 {
858    if (png_ptr == NULL)
859       return NULL;
860 
861    return ((png_voidp)png_ptr->error_ptr);
862 }
863 
864 
865 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
866 void PNGAPI
png_set_strip_error_numbers(png_structrp png_ptr,png_uint_32 strip_mode)867 png_set_strip_error_numbers(png_structrp png_ptr, png_uint_32 strip_mode)
868 {
869    if (png_ptr != NULL)
870    {
871       png_ptr->flags &=
872          ((~(PNG_FLAG_STRIP_ERROR_NUMBERS |
873          PNG_FLAG_STRIP_ERROR_TEXT))&strip_mode);
874    }
875 }
876 #endif
877 
878 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
879    defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
880    /* Currently the above both depend on SETJMP_SUPPORTED, however it would be
881     * possible to implement without setjmp support just so long as there is some
882     * way to handle the error return here:
883     */
884 PNG_FUNCTION(void /* PRIVATE */, (PNGCBAPI
885 png_safe_error),(png_structp png_nonconst_ptr, png_const_charp error_message),
886     PNG_NORETURN)
887 {
888    png_const_structrp png_ptr = png_nonconst_ptr;
889    png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);
890 
891    /* An error is always logged here, overwriting anything (typically a warning)
892     * that is already there:
893     */
894    if (image != NULL)
895    {
896       png_safecat(image->message, (sizeof image->message), 0, error_message);
897       image->warning_or_error |= PNG_IMAGE_ERROR;
898 
899       /* Retrieve the jmp_buf from within the png_control, making this work for
900        * C++ compilation too is pretty tricky: C++ wants a pointer to the first
901        * element of a jmp_buf, but C doesn't tell us the type of that.
902        */
903       if (image->opaque != NULL && image->opaque->error_buf != NULL)
904          longjmp(png_control_jmp_buf(image->opaque), 1);
905 
906       /* Missing longjmp buffer, the following is to help debugging: */
907       {
908          size_t pos = png_safecat(image->message, (sizeof image->message), 0,
909              "bad longjmp: ");
910          png_safecat(image->message, (sizeof image->message), pos,
911              error_message);
912       }
913    }
914 
915    /* Here on an internal programming error. */
916    abort();
917 }
918 
919 #ifdef PNG_WARNINGS_SUPPORTED
920 void /* PRIVATE */ PNGCBAPI
png_safe_warning(png_structp png_nonconst_ptr,png_const_charp warning_message)921 png_safe_warning(png_structp png_nonconst_ptr, png_const_charp warning_message)
922 {
923    png_const_structrp png_ptr = png_nonconst_ptr;
924    png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);
925 
926    /* A warning is only logged if there is no prior warning or error. */
927    if (image->warning_or_error == 0)
928    {
929       png_safecat(image->message, (sizeof image->message), 0, warning_message);
930       image->warning_or_error |= PNG_IMAGE_WARNING;
931    }
932 }
933 #endif
934 
935 int /* PRIVATE */
png_safe_execute(png_imagep image_in,int (* function)(png_voidp),png_voidp arg)936 png_safe_execute(png_imagep image_in, int (*function)(png_voidp), png_voidp arg)
937 {
938    volatile png_imagep image = image_in;
939    volatile int result;
940    volatile png_voidp saved_error_buf;
941    jmp_buf safe_jmpbuf;
942 
943    /* Safely execute function(arg) with png_error returning to this function. */
944    saved_error_buf = image->opaque->error_buf;
945    result = setjmp(safe_jmpbuf) == 0;
946 
947    if (result != 0)
948    {
949 
950       image->opaque->error_buf = safe_jmpbuf;
951       result = function(arg);
952    }
953 
954    image->opaque->error_buf = saved_error_buf;
955 
956    /* And do the cleanup prior to any failure return. */
957    if (result == 0)
958       png_image_free(image);
959 
960    return result;
961 }
962 #endif /* SIMPLIFIED READ || SIMPLIFIED_WRITE */
963 #endif /* READ || WRITE */
964