summaryrefslogtreecommitdiffhomepage
path: root/archival/libunarchive/get_header_tar.c
blob: 1f799277b2a87f70b83e0f2fa14b9a44f81716c4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
/* vi: set sw=4 ts=4: */
/* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 *
 *  FIXME:
 *    In privileged mode if uname and gname map to a uid and gid then use the
 *    mapped value instead of the uid/gid values in tar header
 *
 *  References:
 *    GNU tar and star man pages,
 *    Opengroup's ustar interchange format,
 *	http://www.opengroup.org/onlinepubs/007904975/utilities/pax.html
 */

#include "libbb.h"
#include "unarchive.h"

/*
 * GNU tar uses "base-256 encoding" for very large numbers (>8 billion).
 * Encoding is binary, with highest bit always set as a marker
 * and sign in next-highest bit:
 * 80 00 .. 00 - zero
 * bf ff .. ff - largest positive number
 * ff ff .. ff - minus 1
 * c0 00 .. 00 - smallest negative number
 *
 * We expect it only in size field, where negative numbers don't make sense.
 */
static off_t getBase256_len12(const char *str)
{
	off_t value;
	int len;

	/* if (*str & 0x40) error; - caller prevents this */

	if (sizeof(off_t) >= 12) {
		/* Probably 128-bit (16 byte) off_t. Can be optimized. */
		len = 12;
		value = *str++ & 0x3f;
		while (--len)
			value = (value << 8) + (unsigned char) *str++;
		return value;
	}

#ifdef CHECK_FOR_OVERFLOW
	/* Can be optimized to eat 32-bit chunks */
	char c = *str++ & 0x3f;
	len = 12;
	while (1) {
		if (c)
			bb_error_msg_and_die("overflow in base-256 encoded file size");
		if (--len == sizeof(off_t))
			break;
		c = *str++;
	}
#else
	str += (12 - sizeof(off_t));
#endif

/* Now str points to sizeof(off_t) least significant bytes.
 *
 * Example of tar file with 8914993153 (0x213600001) byte file.
 * Field starts at offset 7c:
 * 00070  30 30 30 00 30 30 30 30  30 30 30 00 80 00 00 00  |000.0000000.....|
 * 00080  00 00 00 02 13 60 00 01  31 31 31 32 30 33 33 36  |.....`..11120336|
 *
 * str is at offset 80 or 84 now (64-bit or 32-bit off_t).
 * We (ab)use the fact that value happens to be aligned,
 * and fetch it in one go:
 */
	if (sizeof(off_t) == 8) {
		value = *(off_t*)str;
		value = SWAP_BE64(value);
	} else if (sizeof(off_t) == 4) {
		value = *(off_t*)str;
		value = SWAP_BE32(value);
	} else {
		value = 0;
		len = sizeof(off_t);
		while (--len)
			value = (value << 8) + (unsigned char) *str++;
	}
	return value;
}

/* NB: _DESTROYS_ str[len] character! */
static unsigned long long getOctal(char *str, int len)
{
	unsigned long long v;
	/* NB: leading spaces are allowed. Using strtoull to handle that.
	 * The downside is that we accept e.g. "-123" too :(
	 */
	str[len] = '\0';
	v = strtoull(str, &str, 8);
	/* std: "Each numeric field is terminated by one or more
	 * <space> or NUL characters". We must support ' '! */
	if (*str != '\0' && *str != ' ')
		bb_error_msg_and_die("corrupted octal value in tar header");
	return v;
}
#define GET_OCTAL(a) getOctal((a), sizeof(a))

void BUG_tar_header_size(void);
char FAST_FUNC get_header_tar(archive_handle_t *archive_handle)
{
	file_header_t *file_header = archive_handle->file_header;
	struct {
		/* ustar header, Posix 1003.1 */
		char name[100];     /*   0-99 */
		char mode[8];       /* 100-107 */
		char uid[8];        /* 108-115 */
		char gid[8];        /* 116-123 */
		char size[12];      /* 124-135 */
		char mtime[12];     /* 136-147 */
		char chksum[8];     /* 148-155 */
		char typeflag;      /* 156-156 */
		char linkname[100]; /* 157-256 */
		/* POSIX:   "ustar" NUL "00" */
		/* GNU tar: "ustar  " NUL */
		/* Normally it's defined as magic[6] followed by
		 * version[2], but we put them together to simplify code
		 */
		char magic[8];      /* 257-264 */
		char uname[32];     /* 265-296 */
		char gname[32];     /* 297-328 */
		char devmajor[8];   /* 329-336 */
		char devminor[8];   /* 337-344 */
		char prefix[155];   /* 345-499 */
		char padding[12];   /* 500-512 */
	} tar;
	char *cp;
	int i, sum_u, sum;
#if ENABLE_FEATURE_TAR_OLDSUN_COMPATIBILITY
	int sum_s;
#endif
	int parse_names;

	/* Our "private data" */
#define p_end (*(smallint *)(&archive_handle->ah_priv[0]))
#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
#define p_longname (*(char* *)(&archive_handle->ah_priv[1]))
#define p_linkname (*(char* *)(&archive_handle->ah_priv[2]))
#else
#define p_longname 0
#define p_linkname 0
#endif
//	if (!archive_handle->ah_priv_inited) {
//		archive_handle->ah_priv_inited = 1;
//		p_end = 0;
//		IF_FEATURE_TAR_GNU_EXTENSIONS(p_longname = NULL;)
//		IF_FEATURE_TAR_GNU_EXTENSIONS(p_linkname = NULL;)
//	}

	if (sizeof(tar) != 512)
		BUG_tar_header_size();

#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
 again:
#endif
	/* Align header */
	data_align(archive_handle, 512);

 again_after_align:

#if ENABLE_DESKTOP || ENABLE_FEATURE_TAR_AUTODETECT
	/* to prevent misdetection of bz2 sig */
	*(uint32_t*)(&tar) = 0;
	i = full_read(archive_handle->src_fd, &tar, 512);
	/* If GNU tar sees EOF in above read, it says:
	 * "tar: A lone zero block at N", where N = kilobyte
	 * where EOF was met (not EOF block, actual EOF!),
	 * and exits with EXIT_SUCCESS.
	 * We will mimic exit(EXIT_SUCCESS), although we will not mimic
	 * the message and we don't check whether we indeed
	 * saw zero block directly before this. */
	if (i == 0) {
		xfunc_error_retval = 0;
 short_read:
		bb_error_msg_and_die("short read");
	}
	if (i != 512) {
		IF_FEATURE_TAR_AUTODETECT(goto autodetect;)
		goto short_read;
	}

#else
	i = 512;
	xread(archive_handle->src_fd, &tar, i);
#endif
	archive_handle->offset += i;

	/* If there is no filename its an empty header */
	if (tar.name[0] == 0 && tar.prefix[0] == 0) {
		if (p_end) {
			/* Second consecutive empty header - end of archive.
			 * Read until the end to empty the pipe from gz or bz2
			 */
			while (full_read(archive_handle->src_fd, &tar, 512) == 512)
				continue;
			return EXIT_FAILURE;
		}
		p_end = 1;
		return EXIT_SUCCESS;
	}
	p_end = 0;

	/* Check header has valid magic, "ustar" is for the proper tar,
	 * five NULs are for the old tar format  */
	if (strncmp(tar.magic, "ustar", 5) != 0
	 && (!ENABLE_FEATURE_TAR_OLDGNU_COMPATIBILITY
	     || memcmp(tar.magic, "\0\0\0\0", 5) != 0)
	) {
#if ENABLE_FEATURE_TAR_AUTODETECT
		char FAST_FUNC (*get_header_ptr)(archive_handle_t *);

 autodetect:
		/* tar gz/bz autodetect: check for gz/bz2 magic.
		 * If we see the magic, and it is the very first block,
		 * we can switch to get_header_tar_gz/bz2/lzma().
		 * Needs seekable fd. I wish recv(MSG_PEEK) works
		 * on any fd... */
#if ENABLE_FEATURE_SEAMLESS_GZ
		if (tar.name[0] == 0x1f && tar.name[1] == (char)0x8b) { /* gzip */
			get_header_ptr = get_header_tar_gz;
		} else
#endif
#if ENABLE_FEATURE_SEAMLESS_BZ2
		if (tar.name[0] == 'B' && tar.name[1] == 'Z'
		 && tar.name[2] == 'h' && isdigit(tar.name[3])
		) { /* bzip2 */
			get_header_ptr = get_header_tar_bz2;
		} else
#endif
			goto err;
		/* Two different causes for lseek() != 0:
		 * unseekable fd (would like to support that too, but...),
		 * or not first block (false positive, it's not .gz/.bz2!) */
		if (lseek(archive_handle->src_fd, -i, SEEK_CUR) != 0)
			goto err;
		while (get_header_ptr(archive_handle) == EXIT_SUCCESS)
			continue;
		return EXIT_FAILURE;
 err:
#endif /* FEATURE_TAR_AUTODETECT */
		bb_error_msg_and_die("invalid tar magic");
	}

	/* Do checksum on headers.
	 * POSIX says that checksum is done on unsigned bytes, but
	 * Sun and HP-UX gets it wrong... more details in
	 * GNU tar source. */
#if ENABLE_FEATURE_TAR_OLDSUN_COMPATIBILITY
	sum_s = ' ' * sizeof(tar.chksum);
#endif
	sum_u = ' ' * sizeof(tar.chksum);
	for (i = 0; i < 148; i++) {
		sum_u += ((unsigned char*)&tar)[i];
#if ENABLE_FEATURE_TAR_OLDSUN_COMPATIBILITY
		sum_s += ((signed char*)&tar)[i];
#endif
	}
	for (i = 156; i < 512; i++) {
		sum_u += ((unsigned char*)&tar)[i];
#if ENABLE_FEATURE_TAR_OLDSUN_COMPATIBILITY
		sum_s += ((signed char*)&tar)[i];
#endif
	}
	/* This field does not need special treatment (getOctal) */
	{
		char *endp; /* gcc likes temp var for &endp */
		sum = strtoul(tar.chksum, &endp, 8);
		if ((*endp != '\0' && *endp != ' ')
		 || (sum_u != sum IF_FEATURE_TAR_OLDSUN_COMPATIBILITY(&& sum_s != sum))
		) {
			bb_error_msg_and_die("invalid tar header checksum");
		}
	}
	/* don't use xstrtoul, tar.chksum may have leading spaces */
	sum = strtoul(tar.chksum, NULL, 8);
	if (sum_u != sum IF_FEATURE_TAR_OLDSUN_COMPATIBILITY(&& sum_s != sum)) {
		bb_error_msg_and_die("invalid tar header checksum");
	}

	/* 0 is reserved for high perf file, treat as normal file */
	if (!tar.typeflag) tar.typeflag = '0';
	parse_names = (tar.typeflag >= '0' && tar.typeflag <= '7');

	/* getOctal trashes subsequent field, therefore we call it
	 * on fields in reverse order */
	if (tar.devmajor[0]) {
		char t = tar.prefix[0];
		/* we trash prefix[0] here, but we DO need it later! */
		unsigned minor = GET_OCTAL(tar.devminor);
		unsigned major = GET_OCTAL(tar.devmajor);
		file_header->device = makedev(major, minor);
		tar.prefix[0] = t;
	}
	file_header->link_target = NULL;
	if (!p_linkname && parse_names && tar.linkname[0]) {
		file_header->link_target = xstrndup(tar.linkname, sizeof(tar.linkname));
		/* FIXME: what if we have non-link object with link_target? */
		/* Will link_target be free()ed? */
	}
#if ENABLE_FEATURE_TAR_UNAME_GNAME
	file_header->uname = tar.uname[0] ? xstrndup(tar.uname, sizeof(tar.uname)) : NULL;
	file_header->gname = tar.gname[0] ? xstrndup(tar.gname, sizeof(tar.gname)) : NULL;
#endif
	/* mtime: rudimentally handle GNU tar's "base256 encoding"
	 * People report tarballs with NEGATIVE unix times encoded that way */
	file_header->mtime = (tar.mtime[0] & 0x80) /* base256? */
			? 0 /* bogus */
			: GET_OCTAL(tar.mtime);
	/* size: handle GNU tar's "base256 encoding" */
	file_header->size = (tar.size[0] & 0xc0) == 0x80 /* positive base256? */
			? getBase256_len12(tar.size)
			: GET_OCTAL(tar.size);
	file_header->gid = GET_OCTAL(tar.gid);
	file_header->uid = GET_OCTAL(tar.uid);
	/* Set bits 0-11 of the files mode */
	file_header->mode = 07777 & GET_OCTAL(tar.mode);

	file_header->name = NULL;
	if (!p_longname && parse_names) {
		/* we trash mode[0] here, it's ok */
		//tar.name[sizeof(tar.name)] = '\0'; - gcc 4.3.0 would complain
		tar.mode[0] = '\0';
		if (tar.prefix[0]) {
			/* and padding[0] */
			//tar.prefix[sizeof(tar.prefix)] = '\0'; - gcc 4.3.0 would complain
			tar.padding[0] = '\0';
			file_header->name = concat_path_file(tar.prefix, tar.name);
		} else
			file_header->name = xstrdup(tar.name);
	}

	/* Set bits 12-15 of the files mode */
	/* (typeflag was not trashed because chksum does not use getOctal) */
	switch (tar.typeflag) {
	/* busybox identifies hard links as being regular files with 0 size and a link name */
	case '1':
		file_header->mode |= S_IFREG;
		break;
	case '7':
	/* case 0: */
	case '0':
#if ENABLE_FEATURE_TAR_OLDGNU_COMPATIBILITY
		if (last_char_is(file_header->name, '/')) {
			goto set_dir;
		}
#endif
		file_header->mode |= S_IFREG;
		break;
	case '2':
		file_header->mode |= S_IFLNK;
		/* have seen tarballs with size field containing
		 * the size of the link target's name */
 size0:
		file_header->size = 0;
		break;
	case '3':
		file_header->mode |= S_IFCHR;
		goto size0; /* paranoia */
	case '4':
		file_header->mode |= S_IFBLK;
		goto size0;
	case '5':
 IF_FEATURE_TAR_OLDGNU_COMPATIBILITY(set_dir:)
		file_header->mode |= S_IFDIR;
		goto size0;
	case '6':
		file_header->mode |= S_IFIFO;
		goto size0;
#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
	case 'L':
		/* free: paranoia: tar with several consecutive longnames */
		free(p_longname);
		/* For paranoia reasons we allocate extra NUL char */
		p_longname = xzalloc(file_header->size + 1);
		/* We read ASCIZ string, including NUL */
		xread(archive_handle->src_fd, p_longname, file_header->size);
		archive_handle->offset += file_header->size;
		/* return get_header_tar(archive_handle); */
		/* gcc 4.1.1 didn't optimize it into jump */
		/* so we will do it ourself, this also saves stack */
		goto again;
	case 'K':
		free(p_linkname);
		p_linkname = xzalloc(file_header->size + 1);
		xread(archive_handle->src_fd, p_linkname, file_header->size);
		archive_handle->offset += file_header->size;
		/* return get_header_tar(archive_handle); */
		goto again;
	case 'D':	/* GNU dump dir */
	case 'M':	/* Continuation of multi volume archive */
	case 'N':	/* Old GNU for names > 100 characters */
	case 'S':	/* Sparse file */
	case 'V':	/* Volume header */
#endif
	case 'g':	/* pax global header */
	case 'x': {	/* pax extended header */
		off_t sz;
		bb_error_msg("warning: skipping header '%c'", tar.typeflag);
		sz = (file_header->size + 511) & ~(off_t)511;
		archive_handle->offset += sz;
		sz >>= 9; /* sz /= 512 but w/o contortions for signed div */
		while (sz--)
			xread(archive_handle->src_fd, &tar, 512);
		/* return get_header_tar(archive_handle); */
		goto again_after_align;
	}
	default:
		bb_error_msg_and_die("unknown typeflag: 0x%x", tar.typeflag);
	}

#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
	if (p_longname) {
		file_header->name = p_longname;
		p_longname = NULL;
	}
	if (p_linkname) {
		file_header->link_target = p_linkname;
		p_linkname = NULL;
	}
#endif
	if (strncmp(file_header->name, "/../"+1, 3) == 0
	 || strstr(file_header->name, "/../")
	) {
		bb_error_msg_and_die("name with '..' encountered: '%s'",
				file_header->name);
	}

	/* Strip trailing '/' in directories */
	/* Must be done after mode is set as '/' is used to check if it's a directory */
	cp = last_char_is(file_header->name, '/');

	if (archive_handle->filter(archive_handle) == EXIT_SUCCESS) {
		archive_handle->action_header(/*archive_handle->*/ file_header);
		/* Note that we kill the '/' only after action_header() */
		/* (like GNU tar 1.15.1: verbose mode outputs "dir/dir/") */
		if (cp) *cp = '\0';
		archive_handle->ah_flags |= ARCHIVE_EXTRACT_QUIET;
		archive_handle->action_data(archive_handle);
		llist_add_to(&(archive_handle->passed), file_header->name);
	} else {
		data_skip(archive_handle);
		free(file_header->name);
	}
	archive_handle->offset += file_header->size;

	free(file_header->link_target);
	/* Do not free(file_header->name)! (why?) */
#if ENABLE_FEATURE_TAR_UNAME_GNAME
	free(file_header->uname);
	free(file_header->gname);
#endif
	return EXIT_SUCCESS;
}