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1// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
2/*
3 * Routines for dealing with .zip archives.
4 *
5 * Copyright (c) Meta Platforms, Inc. and affiliates.
6 */
7
8#include <errno.h>
9#include <fcntl.h>
10#include <stdint.h>
11#include <stdlib.h>
12#include <string.h>
13#include <sys/mman.h>
14#include <unistd.h>
15
16#include "libbpf_internal.h"
17#include "zip.h"
18
19#pragma GCC diagnostic push
20#pragma GCC diagnostic ignored "-Wpacked"
21#pragma GCC diagnostic ignored "-Wattributes"
22
23/* Specification of ZIP file format can be found here:
24 * https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT
25 * For a high level overview of the structure of a ZIP file see
26 * sections 4.3.1 - 4.3.6.
27 *
28 * Data structures appearing in ZIP files do not contain any
29 * padding and they might be misaligned. To allow us to safely
30 * operate on pointers to such structures and their members, we
31 * declare the types as packed.
32 */
33
34#define END_OF_CD_RECORD_MAGIC 0x06054b50
35
36/* See section 4.3.16 of the spec. */
37struct end_of_cd_record {
38 /* Magic value equal to END_OF_CD_RECORD_MAGIC */
39 __u32 magic;
40
41 /* Number of the file containing this structure or 0xFFFF if ZIP64 archive.
42 * Zip archive might span multiple files (disks).
43 */
44 __u16 this_disk;
45
46 /* Number of the file containing the beginning of the central directory or
47 * 0xFFFF if ZIP64 archive.
48 */
49 __u16 cd_disk;
50
51 /* Number of central directory records on this disk or 0xFFFF if ZIP64
52 * archive.
53 */
54 __u16 cd_records;
55
56 /* Number of central directory records on all disks or 0xFFFF if ZIP64
57 * archive.
58 */
59 __u16 cd_records_total;
60
61 /* Size of the central directory record or 0xFFFFFFFF if ZIP64 archive. */
62 __u32 cd_size;
63
64 /* Offset of the central directory from the beginning of the archive or
65 * 0xFFFFFFFF if ZIP64 archive.
66 */
67 __u32 cd_offset;
68
69 /* Length of comment data following end of central directory record. */
70 __u16 comment_length;
71
72 /* Up to 64k of arbitrary bytes. */
73 /* uint8_t comment[comment_length] */
74} __attribute__((packed));
75
76#define CD_FILE_HEADER_MAGIC 0x02014b50
77#define FLAG_ENCRYPTED (1 << 0)
78#define FLAG_HAS_DATA_DESCRIPTOR (1 << 3)
79
80/* See section 4.3.12 of the spec. */
81struct cd_file_header {
82 /* Magic value equal to CD_FILE_HEADER_MAGIC. */
83 __u32 magic;
84 __u16 version;
85 /* Minimum zip version needed to extract the file. */
86 __u16 min_version;
87 __u16 flags;
88 __u16 compression;
89 __u16 last_modified_time;
90 __u16 last_modified_date;
91 __u32 crc;
92 __u32 compressed_size;
93 __u32 uncompressed_size;
94 __u16 file_name_length;
95 __u16 extra_field_length;
96 __u16 file_comment_length;
97 /* Number of the disk where the file starts or 0xFFFF if ZIP64 archive. */
98 __u16 disk;
99 __u16 internal_attributes;
100 __u32 external_attributes;
101 /* Offset from the start of the disk containing the local file header to the
102 * start of the local file header.
103 */
104 __u32 offset;
105} __attribute__((packed));
106
107#define LOCAL_FILE_HEADER_MAGIC 0x04034b50
108
109/* See section 4.3.7 of the spec. */
110struct local_file_header {
111 /* Magic value equal to LOCAL_FILE_HEADER_MAGIC. */
112 __u32 magic;
113 /* Minimum zip version needed to extract the file. */
114 __u16 min_version;
115 __u16 flags;
116 __u16 compression;
117 __u16 last_modified_time;
118 __u16 last_modified_date;
119 __u32 crc;
120 __u32 compressed_size;
121 __u32 uncompressed_size;
122 __u16 file_name_length;
123 __u16 extra_field_length;
124} __attribute__((packed));
125
126#pragma GCC diagnostic pop
127
128struct zip_archive {
129 void *data;
130 __u32 size;
131 __u32 cd_offset;
132 __u32 cd_records;
133};
134
135static void *check_access(struct zip_archive *archive, __u32 offset, __u32 size)
136{
137 if (offset + size > archive->size || offset > offset + size)
138 return NULL;
139
140 return archive->data + offset;
141}
142
143/* Returns 0 on success, -EINVAL on error and -ENOTSUP if the eocd indicates the
144 * archive uses features which are not supported.
145 */
146static int try_parse_end_of_cd(struct zip_archive *archive, __u32 offset)
147{
148 __u16 comment_length, cd_records;
149 struct end_of_cd_record *eocd;
150 __u32 cd_offset, cd_size;
151
152 eocd = check_access(archive, offset, sizeof(*eocd));
153 if (!eocd || eocd->magic != END_OF_CD_RECORD_MAGIC)
154 return -EINVAL;
155
156 comment_length = eocd->comment_length;
157 if (offset + sizeof(*eocd) + comment_length != archive->size)
158 return -EINVAL;
159
160 cd_records = eocd->cd_records;
161 if (eocd->this_disk != 0 || eocd->cd_disk != 0 || eocd->cd_records_total != cd_records)
162 /* This is a valid eocd, but we only support single-file non-ZIP64 archives. */
163 return -ENOTSUP;
164
165 cd_offset = eocd->cd_offset;
166 cd_size = eocd->cd_size;
167 if (!check_access(archive, cd_offset, cd_size))
168 return -EINVAL;
169
170 archive->cd_offset = cd_offset;
171 archive->cd_records = cd_records;
172 return 0;
173}
174
175static int find_cd(struct zip_archive *archive)
176{
177 int64_t limit, offset;
178 int rc = -EINVAL;
179
180 if (archive->size <= sizeof(struct end_of_cd_record))
181 return -EINVAL;
182
183 /* Because the end of central directory ends with a variable length array of
184 * up to 0xFFFF bytes we can't know exactly where it starts and need to
185 * search for it at the end of the file, scanning the (limit, offset] range.
186 */
187 offset = archive->size - sizeof(struct end_of_cd_record);
188 limit = (int64_t)offset - (1 << 16);
189
190 for (; offset >= 0 && offset > limit && rc != 0; offset--) {
191 rc = try_parse_end_of_cd(archive, offset);
192 if (rc == -ENOTSUP)
193 break;
194 }
195 return rc;
196}
197
198struct zip_archive *zip_archive_open(const char *path)
199{
200 struct zip_archive *archive;
201 int err, fd;
202 off_t size;
203 void *data;
204
205 fd = open(path, O_RDONLY | O_CLOEXEC);
206 if (fd < 0)
207 return ERR_PTR(-errno);
208
209 size = lseek(fd, 0, SEEK_END);
210 if (size == (off_t)-1 || size > UINT32_MAX) {
211 close(fd);
212 return ERR_PTR(-EINVAL);
213 }
214
215 data = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
216 err = -errno;
217 close(fd);
218
219 if (data == MAP_FAILED)
220 return ERR_PTR(err);
221
222 archive = malloc(sizeof(*archive));
223 if (!archive) {
224 munmap(data, size);
225 return ERR_PTR(-ENOMEM);
226 }
227
228 archive->data = data;
229 archive->size = size;
230
231 err = find_cd(archive);
232 if (err) {
233 munmap(data, size);
234 free(archive);
235 return ERR_PTR(err);
236 }
237
238 return archive;
239}
240
241void zip_archive_close(struct zip_archive *archive)
242{
243 munmap(archive->data, archive->size);
244 free(archive);
245}
246
247static struct local_file_header *local_file_header_at_offset(struct zip_archive *archive,
248 __u32 offset)
249{
250 struct local_file_header *lfh;
251
252 lfh = check_access(archive, offset, sizeof(*lfh));
253 if (!lfh || lfh->magic != LOCAL_FILE_HEADER_MAGIC)
254 return NULL;
255
256 return lfh;
257}
258
259static int get_entry_at_offset(struct zip_archive *archive, __u32 offset, struct zip_entry *out)
260{
261 struct local_file_header *lfh;
262 __u32 compressed_size;
263 const char *name;
264 void *data;
265
266 lfh = local_file_header_at_offset(archive, offset);
267 if (!lfh)
268 return -EINVAL;
269
270 offset += sizeof(*lfh);
271 if ((lfh->flags & FLAG_ENCRYPTED) || (lfh->flags & FLAG_HAS_DATA_DESCRIPTOR))
272 return -EINVAL;
273
274 name = check_access(archive, offset, lfh->file_name_length);
275 if (!name)
276 return -EINVAL;
277
278 offset += lfh->file_name_length;
279 if (!check_access(archive, offset, lfh->extra_field_length))
280 return -EINVAL;
281
282 offset += lfh->extra_field_length;
283 compressed_size = lfh->compressed_size;
284 data = check_access(archive, offset, compressed_size);
285 if (!data)
286 return -EINVAL;
287
288 out->compression = lfh->compression;
289 out->name_length = lfh->file_name_length;
290 out->name = name;
291 out->data = data;
292 out->data_length = compressed_size;
293 out->data_offset = offset;
294
295 return 0;
296}
297
298int zip_archive_find_entry(struct zip_archive *archive, const char *file_name,
299 struct zip_entry *out)
300{
301 size_t file_name_length = strlen(file_name);
302 __u32 i, offset = archive->cd_offset;
303
304 for (i = 0; i < archive->cd_records; ++i) {
305 __u16 cdfh_name_length, cdfh_flags;
306 struct cd_file_header *cdfh;
307 const char *cdfh_name;
308
309 cdfh = check_access(archive, offset, sizeof(*cdfh));
310 if (!cdfh || cdfh->magic != CD_FILE_HEADER_MAGIC)
311 return -EINVAL;
312
313 offset += sizeof(*cdfh);
314 cdfh_name_length = cdfh->file_name_length;
315 cdfh_name = check_access(archive, offset, cdfh_name_length);
316 if (!cdfh_name)
317 return -EINVAL;
318
319 cdfh_flags = cdfh->flags;
320 if ((cdfh_flags & FLAG_ENCRYPTED) == 0 &&
321 (cdfh_flags & FLAG_HAS_DATA_DESCRIPTOR) == 0 &&
322 file_name_length == cdfh_name_length &&
323 memcmp(file_name, archive->data + offset, file_name_length) == 0) {
324 return get_entry_at_offset(archive, cdfh->offset, out);
325 }
326
327 offset += cdfh_name_length;
328 offset += cdfh->extra_field_length;
329 offset += cdfh->file_comment_length;
330 }
331
332 return -ENOENT;
333}