1 /*
2 * .xz Stream decoder
3 *
4 * Author: Lasse Collin <lasse.collin@tukaani.org>
5 *
6 * This file has been put into the public domain.
7 * You can do whatever you want with this file.
8 */
9
10 #include "xz_private.h"
11 #include "xz_stream.h"
12
13 /* Hash used to validate the Index field */
14 struct xz_dec_hash {
15 vli_type unpadded;
16 vli_type uncompressed;
17 uint32_t crc32;
18 };
19
20 struct xz_dec {
21 /* Position in dec_main() */
22 enum {
23 SEQ_STREAM_HEADER,
24 SEQ_BLOCK_START,
25 SEQ_BLOCK_HEADER,
26 SEQ_BLOCK_UNCOMPRESS,
27 SEQ_BLOCK_PADDING,
28 SEQ_BLOCK_CHECK,
29 SEQ_INDEX,
30 SEQ_INDEX_PADDING,
31 SEQ_INDEX_CRC32,
32 SEQ_STREAM_FOOTER
33 } sequence;
34
35 /* Position in variable-length integers and Check fields */
36 uint32_t pos;
37
38 /* Variable-length integer decoded by dec_vli() */
39 vli_type vli;
40
41 /* Saved in_pos and out_pos */
42 size_t in_start;
43 size_t out_start;
44
45 /* CRC32 value in Block or Index */
46 uint32_t crc32;
47
48 /* Type of the integrity check calculated from uncompressed data */
49 enum xz_check check_type;
50
51 /* Operation mode */
52 enum xz_mode mode;
53
54 /*
55 * True if the next call to xz_dec_run() is allowed to return
56 * XZ_BUF_ERROR.
57 */
58 bool allow_buf_error;
59
60 /* Information stored in Block Header */
61 struct {
62 /*
63 * Value stored in the Compressed Size field, or
64 * VLI_UNKNOWN if Compressed Size is not present.
65 */
66 vli_type compressed;
67
68 /*
69 * Value stored in the Uncompressed Size field, or
70 * VLI_UNKNOWN if Uncompressed Size is not present.
71 */
72 vli_type uncompressed;
73
74 /* Size of the Block Header field */
75 uint32_t size;
76 } block_header;
77
78 /* Information collected when decoding Blocks */
79 struct {
80 /* Observed compressed size of the current Block */
81 vli_type compressed;
82
83 /* Observed uncompressed size of the current Block */
84 vli_type uncompressed;
85
86 /* Number of Blocks decoded so far */
87 vli_type count;
88
89 /*
90 * Hash calculated from the Block sizes. This is used to
91 * validate the Index field.
92 */
93 struct xz_dec_hash hash;
94 } block;
95
96 /* Variables needed when verifying the Index field */
97 struct {
98 /* Position in dec_index() */
99 enum {
100 SEQ_INDEX_COUNT,
101 SEQ_INDEX_UNPADDED,
102 SEQ_INDEX_UNCOMPRESSED
103 } sequence;
104
105 /* Size of the Index in bytes */
106 vli_type size;
107
108 /* Number of Records (matches block.count in valid files) */
109 vli_type count;
110
111 /*
112 * Hash calculated from the Records (matches block.hash in
113 * valid files).
114 */
115 struct xz_dec_hash hash;
116 } index;
117
118 /*
119 * Temporary buffer needed to hold Stream Header, Block Header,
120 * and Stream Footer. The Block Header is the biggest (1 KiB)
121 * so we reserve space according to that. buf[] has to be aligned
122 * to a multiple of four bytes; the size_t variables before it
123 * should guarantee this.
124 */
125 struct {
126 size_t pos;
127 size_t size;
128 uint8_t buf[1024];
129 } temp;
130
131 struct xz_dec_lzma2 *lzma2;
132
133 #ifdef XZ_DEC_BCJ
134 struct xz_dec_bcj *bcj;
135 bool bcj_active;
136 #endif
137 };
138
139 #ifdef XZ_DEC_ANY_CHECK
140 /* Sizes of the Check field with different Check IDs */
141 static const uint8_t check_sizes[16] = {
142 0,
143 4, 4, 4,
144 8, 8, 8,
145 16, 16, 16,
146 32, 32, 32,
147 64, 64, 64
148 };
149 #endif
150
151 /*
152 * Fill s->temp by copying data starting from b->in[b->in_pos]. Caller
153 * must have set s->temp.pos to indicate how much data we are supposed
154 * to copy into s->temp.buf. Return true once s->temp.pos has reached
155 * s->temp.size.
156 */
fill_temp(struct xz_dec * s,struct xz_buf * b)157 static bool fill_temp(struct xz_dec *s, struct xz_buf *b)
158 {
159 size_t copy_size = min_t(size_t,
160 b->in_size - b->in_pos, s->temp.size - s->temp.pos);
161
162 memcpy(s->temp.buf + s->temp.pos, b->in + b->in_pos, copy_size);
163 b->in_pos += copy_size;
164 s->temp.pos += copy_size;
165
166 if (s->temp.pos == s->temp.size) {
167 s->temp.pos = 0;
168 return true;
169 }
170
171 return false;
172 }
173
174 /* Decode a variable-length integer (little-endian base-128 encoding) */
dec_vli(struct xz_dec * s,const uint8_t * in,size_t * in_pos,size_t in_size)175 static enum xz_ret dec_vli(struct xz_dec *s, const uint8_t *in,
176 size_t *in_pos, size_t in_size)
177 {
178 uint8_t byte;
179
180 if (s->pos == 0)
181 s->vli = 0;
182
183 while (*in_pos < in_size) {
184 byte = in[*in_pos];
185 ++*in_pos;
186
187 s->vli |= (vli_type)(byte & 0x7F) << s->pos;
188
189 if ((byte & 0x80) == 0) {
190 /* Don't allow non-minimal encodings. */
191 if (byte == 0 && s->pos != 0)
192 return XZ_DATA_ERROR;
193
194 s->pos = 0;
195 return XZ_STREAM_END;
196 }
197
198 s->pos += 7;
199 if (s->pos == 7 * VLI_BYTES_MAX)
200 return XZ_DATA_ERROR;
201 }
202
203 return XZ_OK;
204 }
205
206 /*
207 * Decode the Compressed Data field from a Block. Update and validate
208 * the observed compressed and uncompressed sizes of the Block so that
209 * they don't exceed the values possibly stored in the Block Header
210 * (validation assumes that no integer overflow occurs, since vli_type
211 * is normally uint64_t). Update the CRC32 if presence of the CRC32
212 * field was indicated in Stream Header.
213 *
214 * Once the decoding is finished, validate that the observed sizes match
215 * the sizes possibly stored in the Block Header. Update the hash and
216 * Block count, which are later used to validate the Index field.
217 */
dec_block(struct xz_dec * s,struct xz_buf * b)218 static enum xz_ret dec_block(struct xz_dec *s, struct xz_buf *b)
219 {
220 enum xz_ret ret;
221
222 s->in_start = b->in_pos;
223 s->out_start = b->out_pos;
224
225 #ifdef XZ_DEC_BCJ
226 if (s->bcj_active)
227 ret = xz_dec_bcj_run(s->bcj, s->lzma2, b);
228 else
229 #endif
230 ret = xz_dec_lzma2_run(s->lzma2, b);
231
232 s->block.compressed += b->in_pos - s->in_start;
233 s->block.uncompressed += b->out_pos - s->out_start;
234
235 /*
236 * There is no need to separately check for VLI_UNKNOWN, since
237 * the observed sizes are always smaller than VLI_UNKNOWN.
238 */
239 if (s->block.compressed > s->block_header.compressed
240 || s->block.uncompressed
241 > s->block_header.uncompressed)
242 return XZ_DATA_ERROR;
243
244 if (s->check_type == XZ_CHECK_CRC32)
245 s->crc32 = xz_crc32(b->out + s->out_start,
246 b->out_pos - s->out_start, s->crc32);
247
248 if (ret == XZ_STREAM_END) {
249 if (s->block_header.compressed != VLI_UNKNOWN
250 && s->block_header.compressed
251 != s->block.compressed)
252 return XZ_DATA_ERROR;
253
254 if (s->block_header.uncompressed != VLI_UNKNOWN
255 && s->block_header.uncompressed
256 != s->block.uncompressed)
257 return XZ_DATA_ERROR;
258
259 s->block.hash.unpadded += s->block_header.size
260 + s->block.compressed;
261
262 #ifdef XZ_DEC_ANY_CHECK
263 s->block.hash.unpadded += check_sizes[s->check_type];
264 #else
265 if (s->check_type == XZ_CHECK_CRC32)
266 s->block.hash.unpadded += 4;
267 #endif
268
269 s->block.hash.uncompressed += s->block.uncompressed;
270 s->block.hash.crc32 = xz_crc32(
271 (const uint8_t *)&s->block.hash,
272 sizeof(s->block.hash), s->block.hash.crc32);
273
274 ++s->block.count;
275 }
276
277 return ret;
278 }
279
280 /* Update the Index size and the CRC32 value. */
index_update(struct xz_dec * s,const struct xz_buf * b)281 static void index_update(struct xz_dec *s, const struct xz_buf *b)
282 {
283 size_t in_used = b->in_pos - s->in_start;
284 s->index.size += in_used;
285 s->crc32 = xz_crc32(b->in + s->in_start, in_used, s->crc32);
286 }
287
288 /*
289 * Decode the Number of Records, Unpadded Size, and Uncompressed Size
290 * fields from the Index field. That is, Index Padding and CRC32 are not
291 * decoded by this function.
292 *
293 * This can return XZ_OK (more input needed), XZ_STREAM_END (everything
294 * successfully decoded), or XZ_DATA_ERROR (input is corrupt).
295 */
dec_index(struct xz_dec * s,struct xz_buf * b)296 static enum xz_ret dec_index(struct xz_dec *s, struct xz_buf *b)
297 {
298 enum xz_ret ret;
299
300 do {
301 ret = dec_vli(s, b->in, &b->in_pos, b->in_size);
302 if (ret != XZ_STREAM_END) {
303 index_update(s, b);
304 return ret;
305 }
306
307 switch (s->index.sequence) {
308 case SEQ_INDEX_COUNT:
309 s->index.count = s->vli;
310
311 /*
312 * Validate that the Number of Records field
313 * indicates the same number of Records as
314 * there were Blocks in the Stream.
315 */
316 if (s->index.count != s->block.count)
317 return XZ_DATA_ERROR;
318
319 s->index.sequence = SEQ_INDEX_UNPADDED;
320 break;
321
322 case SEQ_INDEX_UNPADDED:
323 s->index.hash.unpadded += s->vli;
324 s->index.sequence = SEQ_INDEX_UNCOMPRESSED;
325 break;
326
327 case SEQ_INDEX_UNCOMPRESSED:
328 s->index.hash.uncompressed += s->vli;
329 s->index.hash.crc32 = xz_crc32(
330 (const uint8_t *)&s->index.hash,
331 sizeof(s->index.hash),
332 s->index.hash.crc32);
333 --s->index.count;
334 s->index.sequence = SEQ_INDEX_UNPADDED;
335 break;
336 }
337 } while (s->index.count > 0);
338
339 return XZ_STREAM_END;
340 }
341
342 /*
343 * Validate that the next four input bytes match the value of s->crc32.
344 * s->pos must be zero when starting to validate the first byte.
345 */
crc32_validate(struct xz_dec * s,struct xz_buf * b)346 static enum xz_ret crc32_validate(struct xz_dec *s, struct xz_buf *b)
347 {
348 do {
349 if (b->in_pos == b->in_size)
350 return XZ_OK;
351
352 if (((s->crc32 >> s->pos) & 0xFF) != b->in[b->in_pos++])
353 return XZ_DATA_ERROR;
354
355 s->pos += 8;
356
357 } while (s->pos < 32);
358
359 s->crc32 = 0;
360 s->pos = 0;
361
362 return XZ_STREAM_END;
363 }
364
365 #ifdef XZ_DEC_ANY_CHECK
366 /*
367 * Skip over the Check field when the Check ID is not supported.
368 * Returns true once the whole Check field has been skipped over.
369 */
check_skip(struct xz_dec * s,struct xz_buf * b)370 static bool check_skip(struct xz_dec *s, struct xz_buf *b)
371 {
372 while (s->pos < check_sizes[s->check_type]) {
373 if (b->in_pos == b->in_size)
374 return false;
375
376 ++b->in_pos;
377 ++s->pos;
378 }
379
380 s->pos = 0;
381
382 return true;
383 }
384 #endif
385
386 /* Decode the Stream Header field (the first 12 bytes of the .xz Stream). */
dec_stream_header(struct xz_dec * s)387 static enum xz_ret dec_stream_header(struct xz_dec *s)
388 {
389 if (!memeq(s->temp.buf, HEADER_MAGIC, HEADER_MAGIC_SIZE))
390 return XZ_FORMAT_ERROR;
391
392 if (xz_crc32(s->temp.buf + HEADER_MAGIC_SIZE, 2, 0)
393 != get_le32(s->temp.buf + HEADER_MAGIC_SIZE + 2))
394 return XZ_DATA_ERROR;
395
396 if (s->temp.buf[HEADER_MAGIC_SIZE] != 0)
397 return XZ_OPTIONS_ERROR;
398
399 /*
400 * Of integrity checks, we support only none (Check ID = 0) and
401 * CRC32 (Check ID = 1). However, if XZ_DEC_ANY_CHECK is defined,
402 * we will accept other check types too, but then the check won't
403 * be verified and a warning (XZ_UNSUPPORTED_CHECK) will be given.
404 */
405 s->check_type = s->temp.buf[HEADER_MAGIC_SIZE + 1];
406
407 #ifdef XZ_DEC_ANY_CHECK
408 if (s->check_type > XZ_CHECK_MAX)
409 return XZ_OPTIONS_ERROR;
410
411 if (s->check_type > XZ_CHECK_CRC32)
412 return XZ_UNSUPPORTED_CHECK;
413 #else
414 if (s->check_type > XZ_CHECK_CRC32)
415 return XZ_OPTIONS_ERROR;
416 #endif
417
418 return XZ_OK;
419 }
420
421 /* Decode the Stream Footer field (the last 12 bytes of the .xz Stream) */
dec_stream_footer(struct xz_dec * s)422 static enum xz_ret dec_stream_footer(struct xz_dec *s)
423 {
424 if (!memeq(s->temp.buf + 10, FOOTER_MAGIC, FOOTER_MAGIC_SIZE))
425 return XZ_DATA_ERROR;
426
427 if (xz_crc32(s->temp.buf + 4, 6, 0) != get_le32(s->temp.buf))
428 return XZ_DATA_ERROR;
429
430 /*
431 * Validate Backward Size. Note that we never added the size of the
432 * Index CRC32 field to s->index.size, thus we use s->index.size / 4
433 * instead of s->index.size / 4 - 1.
434 */
435 if ((s->index.size >> 2) != get_le32(s->temp.buf + 4))
436 return XZ_DATA_ERROR;
437
438 if (s->temp.buf[8] != 0 || s->temp.buf[9] != s->check_type)
439 return XZ_DATA_ERROR;
440
441 /*
442 * Use XZ_STREAM_END instead of XZ_OK to be more convenient
443 * for the caller.
444 */
445 return XZ_STREAM_END;
446 }
447
448 /* Decode the Block Header and initialize the filter chain. */
dec_block_header(struct xz_dec * s)449 static enum xz_ret dec_block_header(struct xz_dec *s)
450 {
451 enum xz_ret ret;
452
453 /*
454 * Validate the CRC32. We know that the temp buffer is at least
455 * eight bytes so this is safe.
456 */
457 s->temp.size -= 4;
458 if (xz_crc32(s->temp.buf, s->temp.size, 0)
459 != get_le32(s->temp.buf + s->temp.size))
460 return XZ_DATA_ERROR;
461
462 s->temp.pos = 2;
463
464 /*
465 * Catch unsupported Block Flags. We support only one or two filters
466 * in the chain, so we catch that with the same test.
467 */
468 #ifdef XZ_DEC_BCJ
469 if (s->temp.buf[1] & 0x3E)
470 #else
471 if (s->temp.buf[1] & 0x3F)
472 #endif
473 return XZ_OPTIONS_ERROR;
474
475 /* Compressed Size */
476 if (s->temp.buf[1] & 0x40) {
477 if (dec_vli(s, s->temp.buf, &s->temp.pos, s->temp.size)
478 != XZ_STREAM_END)
479 return XZ_DATA_ERROR;
480
481 s->block_header.compressed = s->vli;
482 } else {
483 s->block_header.compressed = VLI_UNKNOWN;
484 }
485
486 /* Uncompressed Size */
487 if (s->temp.buf[1] & 0x80) {
488 if (dec_vli(s, s->temp.buf, &s->temp.pos, s->temp.size)
489 != XZ_STREAM_END)
490 return XZ_DATA_ERROR;
491
492 s->block_header.uncompressed = s->vli;
493 } else {
494 s->block_header.uncompressed = VLI_UNKNOWN;
495 }
496
497 #ifdef XZ_DEC_BCJ
498 /* If there are two filters, the first one must be a BCJ filter. */
499 s->bcj_active = s->temp.buf[1] & 0x01;
500 if (s->bcj_active) {
501 if (s->temp.size - s->temp.pos < 2)
502 return XZ_OPTIONS_ERROR;
503
504 ret = xz_dec_bcj_reset(s->bcj, s->temp.buf[s->temp.pos++]);
505 if (ret != XZ_OK)
506 return ret;
507
508 /*
509 * We don't support custom start offset,
510 * so Size of Properties must be zero.
511 */
512 if (s->temp.buf[s->temp.pos++] != 0x00)
513 return XZ_OPTIONS_ERROR;
514 }
515 #endif
516
517 /* Valid Filter Flags always take at least two bytes. */
518 if (s->temp.size - s->temp.pos < 2)
519 return XZ_DATA_ERROR;
520
521 /* Filter ID = LZMA2 */
522 if (s->temp.buf[s->temp.pos++] != 0x21)
523 return XZ_OPTIONS_ERROR;
524
525 /* Size of Properties = 1-byte Filter Properties */
526 if (s->temp.buf[s->temp.pos++] != 0x01)
527 return XZ_OPTIONS_ERROR;
528
529 /* Filter Properties contains LZMA2 dictionary size. */
530 if (s->temp.size - s->temp.pos < 1)
531 return XZ_DATA_ERROR;
532
533 ret = xz_dec_lzma2_reset(s->lzma2, s->temp.buf[s->temp.pos++]);
534 if (ret != XZ_OK)
535 return ret;
536
537 /* The rest must be Header Padding. */
538 while (s->temp.pos < s->temp.size)
539 if (s->temp.buf[s->temp.pos++] != 0x00)
540 return XZ_OPTIONS_ERROR;
541
542 s->temp.pos = 0;
543 s->block.compressed = 0;
544 s->block.uncompressed = 0;
545
546 return XZ_OK;
547 }
548
dec_main(struct xz_dec * s,struct xz_buf * b)549 static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
550 {
551 enum xz_ret ret;
552
553 /*
554 * Store the start position for the case when we are in the middle
555 * of the Index field.
556 */
557 s->in_start = b->in_pos;
558
559 while (true) {
560 switch (s->sequence) {
561 case SEQ_STREAM_HEADER:
562 /*
563 * Stream Header is copied to s->temp, and then
564 * decoded from there. This way if the caller
565 * gives us only little input at a time, we can
566 * still keep the Stream Header decoding code
567 * simple. Similar approach is used in many places
568 * in this file.
569 */
570 if (!fill_temp(s, b))
571 return XZ_OK;
572
573 /*
574 * If dec_stream_header() returns
575 * XZ_UNSUPPORTED_CHECK, it is still possible
576 * to continue decoding if working in multi-call
577 * mode. Thus, update s->sequence before calling
578 * dec_stream_header().
579 */
580 s->sequence = SEQ_BLOCK_START;
581
582 ret = dec_stream_header(s);
583 if (ret != XZ_OK)
584 return ret;
585
586 /* Fall through */
587
588 case SEQ_BLOCK_START:
589 /* We need one byte of input to continue. */
590 if (b->in_pos == b->in_size)
591 return XZ_OK;
592
593 /* See if this is the beginning of the Index field. */
594 if (b->in[b->in_pos] == 0) {
595 s->in_start = b->in_pos++;
596 s->sequence = SEQ_INDEX;
597 break;
598 }
599
600 /*
601 * Calculate the size of the Block Header and
602 * prepare to decode it.
603 */
604 s->block_header.size
605 = ((uint32_t)b->in[b->in_pos] + 1) * 4;
606
607 s->temp.size = s->block_header.size;
608 s->temp.pos = 0;
609 s->sequence = SEQ_BLOCK_HEADER;
610
611 /* Fall through */
612
613 case SEQ_BLOCK_HEADER:
614 if (!fill_temp(s, b))
615 return XZ_OK;
616
617 ret = dec_block_header(s);
618 if (ret != XZ_OK)
619 return ret;
620
621 s->sequence = SEQ_BLOCK_UNCOMPRESS;
622
623 /* Fall through */
624
625 case SEQ_BLOCK_UNCOMPRESS:
626 ret = dec_block(s, b);
627 if (ret != XZ_STREAM_END)
628 return ret;
629
630 s->sequence = SEQ_BLOCK_PADDING;
631
632 /* Fall through */
633
634 case SEQ_BLOCK_PADDING:
635 /*
636 * Size of Compressed Data + Block Padding
637 * must be a multiple of four. We don't need
638 * s->block.compressed for anything else
639 * anymore, so we use it here to test the size
640 * of the Block Padding field.
641 */
642 while (s->block.compressed & 3) {
643 if (b->in_pos == b->in_size)
644 return XZ_OK;
645
646 if (b->in[b->in_pos++] != 0)
647 return XZ_DATA_ERROR;
648
649 ++s->block.compressed;
650 }
651
652 s->sequence = SEQ_BLOCK_CHECK;
653
654 /* Fall through */
655
656 case SEQ_BLOCK_CHECK:
657 if (s->check_type == XZ_CHECK_CRC32) {
658 ret = crc32_validate(s, b);
659 if (ret != XZ_STREAM_END)
660 return ret;
661 }
662 #ifdef XZ_DEC_ANY_CHECK
663 else if (!check_skip(s, b)) {
664 return XZ_OK;
665 }
666 #endif
667
668 s->sequence = SEQ_BLOCK_START;
669 break;
670
671 case SEQ_INDEX:
672 ret = dec_index(s, b);
673 if (ret != XZ_STREAM_END)
674 return ret;
675
676 s->sequence = SEQ_INDEX_PADDING;
677
678 /* Fall through */
679
680 case SEQ_INDEX_PADDING:
681 while ((s->index.size + (b->in_pos - s->in_start))
682 & 3) {
683 if (b->in_pos == b->in_size) {
684 index_update(s, b);
685 return XZ_OK;
686 }
687
688 if (b->in[b->in_pos++] != 0)
689 return XZ_DATA_ERROR;
690 }
691
692 /* Finish the CRC32 value and Index size. */
693 index_update(s, b);
694
695 /* Compare the hashes to validate the Index field. */
696 if (!memeq(&s->block.hash, &s->index.hash,
697 sizeof(s->block.hash)))
698 return XZ_DATA_ERROR;
699
700 s->sequence = SEQ_INDEX_CRC32;
701
702 /* Fall through */
703
704 case SEQ_INDEX_CRC32:
705 ret = crc32_validate(s, b);
706 if (ret != XZ_STREAM_END)
707 return ret;
708
709 s->temp.size = STREAM_HEADER_SIZE;
710 s->sequence = SEQ_STREAM_FOOTER;
711
712 /* Fall through */
713
714 case SEQ_STREAM_FOOTER:
715 if (!fill_temp(s, b))
716 return XZ_OK;
717
718 return dec_stream_footer(s);
719 }
720 }
721
722 /* Never reached */
723 }
724
725 /*
726 * xz_dec_run() is a wrapper for dec_main() to handle some special cases in
727 * multi-call and single-call decoding.
728 *
729 * In multi-call mode, we must return XZ_BUF_ERROR when it seems clear that we
730 * are not going to make any progress anymore. This is to prevent the caller
731 * from calling us infinitely when the input file is truncated or otherwise
732 * corrupt. Since zlib-style API allows that the caller fills the input buffer
733 * only when the decoder doesn't produce any new output, we have to be careful
734 * to avoid returning XZ_BUF_ERROR too easily: XZ_BUF_ERROR is returned only
735 * after the second consecutive call to xz_dec_run() that makes no progress.
736 *
737 * In single-call mode, if we couldn't decode everything and no error
738 * occurred, either the input is truncated or the output buffer is too small.
739 * Since we know that the last input byte never produces any output, we know
740 * that if all the input was consumed and decoding wasn't finished, the file
741 * must be corrupt. Otherwise the output buffer has to be too small or the
742 * file is corrupt in a way that decoding it produces too big output.
743 *
744 * If single-call decoding fails, we reset b->in_pos and b->out_pos back to
745 * their original values. This is because with some filter chains there won't
746 * be any valid uncompressed data in the output buffer unless the decoding
747 * actually succeeds (that's the price to pay of using the output buffer as
748 * the workspace).
749 */
xz_dec_run(struct xz_dec * s,struct xz_buf * b)750 XZ_EXTERN enum xz_ret xz_dec_run(struct xz_dec *s, struct xz_buf *b)
751 {
752 size_t in_start;
753 size_t out_start;
754 enum xz_ret ret;
755
756 if (DEC_IS_SINGLE(s->mode))
757 xz_dec_reset(s);
758
759 in_start = b->in_pos;
760 out_start = b->out_pos;
761 ret = dec_main(s, b);
762
763 if (DEC_IS_SINGLE(s->mode)) {
764 if (ret == XZ_OK)
765 ret = b->in_pos == b->in_size
766 ? XZ_DATA_ERROR : XZ_BUF_ERROR;
767
768 if (ret != XZ_STREAM_END) {
769 b->in_pos = in_start;
770 b->out_pos = out_start;
771 }
772
773 } else if (ret == XZ_OK && in_start == b->in_pos
774 && out_start == b->out_pos) {
775 if (s->allow_buf_error)
776 ret = XZ_BUF_ERROR;
777
778 s->allow_buf_error = true;
779 } else {
780 s->allow_buf_error = false;
781 }
782
783 return ret;
784 }
785
xz_dec_init(enum xz_mode mode,uint32_t dict_max)786 XZ_EXTERN struct xz_dec *xz_dec_init(enum xz_mode mode, uint32_t dict_max)
787 {
788 struct xz_dec *s = kmalloc(sizeof(*s), GFP_KERNEL);
789 if (s == NULL)
790 return NULL;
791
792 s->mode = mode;
793
794 #ifdef XZ_DEC_BCJ
795 s->bcj = xz_dec_bcj_create(DEC_IS_SINGLE(mode));
796 if (s->bcj == NULL)
797 goto error_bcj;
798 #endif
799
800 s->lzma2 = xz_dec_lzma2_create(mode, dict_max);
801 if (s->lzma2 == NULL)
802 goto error_lzma2;
803
804 xz_dec_reset(s);
805 return s;
806
807 error_lzma2:
808 #ifdef XZ_DEC_BCJ
809 xz_dec_bcj_end(s->bcj);
810 error_bcj:
811 #endif
812 kfree(s);
813 return NULL;
814 }
815
xz_dec_reset(struct xz_dec * s)816 XZ_EXTERN void xz_dec_reset(struct xz_dec *s)
817 {
818 s->sequence = SEQ_STREAM_HEADER;
819 s->allow_buf_error = false;
820 s->pos = 0;
821 s->crc32 = 0;
822 memzero(&s->block, sizeof(s->block));
823 memzero(&s->index, sizeof(s->index));
824 s->temp.pos = 0;
825 s->temp.size = STREAM_HEADER_SIZE;
826 }
827
xz_dec_end(struct xz_dec * s)828 XZ_EXTERN void xz_dec_end(struct xz_dec *s)
829 {
830 if (s != NULL) {
831 xz_dec_lzma2_end(s->lzma2);
832 #ifdef XZ_DEC_BCJ
833 xz_dec_bcj_end(s->bcj);
834 #endif
835 kfree(s);
836 }
837 }
838
