1 /*
2 * gzip_decompress.c - decompress with a gzip wrapper
3 *
4 * Originally public domain; changes after 2016-09-07 are copyrighted.
5 *
6 * Copyright 2016 Eric Biggers
7 *
8 * Permission is hereby granted, free of charge, to any person
9 * obtaining a copy of this software and associated documentation
10 * files (the "Software"), to deal in the Software without
11 * restriction, including without limitation the rights to use,
12 * copy, modify, merge, publish, distribute, sublicense, and/or sell
13 * copies of the Software, and to permit persons to whom the
14 * Software is furnished to do so, subject to the following
15 * conditions:
16 *
17 * The above copyright notice and this permission notice shall be
18 * included in all copies or substantial portions of the Software.
19 *
20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
22 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
23 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
24 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
25 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
26 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
27 * OTHER DEALINGS IN THE SOFTWARE.
28 */
29
30 #include "gzip_constants.h"
31 #include "unaligned.h"
32
33 #include "libdeflate.h"
34
35 LIBDEFLATEAPI enum libdeflate_result
libdeflate_gzip_decompress(struct libdeflate_decompressor * d,const void * in,size_t in_nbytes,void * out,size_t out_nbytes_avail,size_t * actual_out_nbytes_ret)36 libdeflate_gzip_decompress(struct libdeflate_decompressor *d,
37 const void *in, size_t in_nbytes,
38 void *out, size_t out_nbytes_avail,
39 size_t *actual_out_nbytes_ret)
40 {
41 const u8 *in_next = in;
42 const u8 * const in_end = in_next + in_nbytes;
43 u8 flg;
44 size_t actual_out_nbytes;
45 enum libdeflate_result result;
46
47 if (in_nbytes < GZIP_MIN_OVERHEAD)
48 return LIBDEFLATE_BAD_DATA;
49
50 /* ID1 */
51 if (*in_next++ != GZIP_ID1)
52 return LIBDEFLATE_BAD_DATA;
53 /* ID2 */
54 if (*in_next++ != GZIP_ID2)
55 return LIBDEFLATE_BAD_DATA;
56 /* CM */
57 if (*in_next++ != GZIP_CM_DEFLATE)
58 return LIBDEFLATE_BAD_DATA;
59 flg = *in_next++;
60 /* MTIME */
61 in_next += 4;
62 /* XFL */
63 in_next += 1;
64 /* OS */
65 in_next += 1;
66
67 if (flg & GZIP_FRESERVED)
68 return LIBDEFLATE_BAD_DATA;
69
70 /* Extra field */
71 if (flg & GZIP_FEXTRA) {
72 u16 xlen = get_unaligned_le16(in_next);
73 in_next += 2;
74
75 if (in_end - in_next < (u32)xlen + GZIP_FOOTER_SIZE)
76 return LIBDEFLATE_BAD_DATA;
77
78 in_next += xlen;
79 }
80
81 /* Original file name (zero terminated) */
82 if (flg & GZIP_FNAME) {
83 while (*in_next++ != 0 && in_next != in_end)
84 ;
85 if (in_end - in_next < GZIP_FOOTER_SIZE)
86 return LIBDEFLATE_BAD_DATA;
87 }
88
89 /* File comment (zero terminated) */
90 if (flg & GZIP_FCOMMENT) {
91 while (*in_next++ != 0 && in_next != in_end)
92 ;
93 if (in_end - in_next < GZIP_FOOTER_SIZE)
94 return LIBDEFLATE_BAD_DATA;
95 }
96
97 /* CRC16 for gzip header */
98 if (flg & GZIP_FHCRC) {
99 in_next += 2;
100 if (in_end - in_next < GZIP_FOOTER_SIZE)
101 return LIBDEFLATE_BAD_DATA;
102 }
103
104 /* Compressed data */
105 result = libdeflate_deflate_decompress(d, in_next,
106 in_end - GZIP_FOOTER_SIZE - in_next,
107 out, out_nbytes_avail,
108 actual_out_nbytes_ret);
109 if (result != LIBDEFLATE_SUCCESS)
110 return result;
111
112 if (actual_out_nbytes_ret)
113 actual_out_nbytes = *actual_out_nbytes_ret;
114 else
115 actual_out_nbytes = out_nbytes_avail;
116
117 in_next = in_end - GZIP_FOOTER_SIZE;
118
119 /* CRC32 */
120 if (libdeflate_crc32(0, out, actual_out_nbytes) !=
121 get_unaligned_le32(in_next))
122 return LIBDEFLATE_BAD_DATA;
123 in_next += 4;
124
125 /* ISIZE */
126 if ((u32)actual_out_nbytes != get_unaligned_le32(in_next))
127 return LIBDEFLATE_BAD_DATA;
128
129 return LIBDEFLATE_SUCCESS;
130 }
131