1 // SPDX-License-Identifier: 0BSD
2
3 /*
4 * LZMA2 decoder
5 *
6 * Authors: Lasse Collin <lasse.collin@tukaani.org>
7 * Igor Pavlov <https://7-zip.org/>
8 */
9
10 #include "xz_private.h"
11 #include "xz_lzma2.h"
12
13 /*
14 * Range decoder initialization eats the first five bytes of each LZMA chunk.
15 */
16 #define RC_INIT_BYTES 5
17
18 /*
19 * Minimum number of usable input buffer to safely decode one LZMA symbol.
20 * The worst case is that we decode 22 bits using probabilities and 26
21 * direct bits. This may decode at maximum of 20 bytes of input. However,
22 * lzma_main() does an extra normalization before returning, thus we
23 * need to put 21 here.
24 */
25 #define LZMA_IN_REQUIRED 21
26
27 /*
28 * Dictionary (history buffer)
29 *
30 * These are always true:
31 * start <= pos <= full <= end
32 * pos <= limit <= end
33 *
34 * In multi-call mode, also these are true:
35 * end == size
36 * size <= size_max
37 * allocated <= size
38 *
39 * Most of these variables are size_t to support single-call mode,
40 * in which the dictionary variables address the actual output
41 * buffer directly.
42 */
43 struct dictionary {
44 /* Beginning of the history buffer */
45 uint8_t *buf;
46
47 /* Old position in buf (before decoding more data) */
48 size_t start;
49
50 /* Position in buf */
51 size_t pos;
52
53 /*
54 * How full dictionary is. This is used to detect corrupt input that
55 * would read beyond the beginning of the uncompressed stream.
56 */
57 size_t full;
58
59 /* Write limit; we don't write to buf[limit] or later bytes. */
60 size_t limit;
61
62 /*
63 * End of the dictionary buffer. In multi-call mode, this is
64 * the same as the dictionary size. In single-call mode, this
65 * indicates the size of the output buffer.
66 */
67 size_t end;
68
69 /*
70 * Size of the dictionary as specified in Block Header. This is used
71 * together with "full" to detect corrupt input that would make us
72 * read beyond the beginning of the uncompressed stream.
73 */
74 uint32_t size;
75
76 /*
77 * Maximum allowed dictionary size in multi-call mode.
78 * This is ignored in single-call mode.
79 */
80 uint32_t size_max;
81
82 /*
83 * Amount of memory currently allocated for the dictionary.
84 * This is used only with XZ_DYNALLOC. (With XZ_PREALLOC,
85 * size_max is always the same as the allocated size.)
86 */
87 uint32_t allocated;
88
89 /* Operation mode */
90 enum xz_mode mode;
91 };
92
93 /* Range decoder */
94 struct rc_dec {
95 uint32_t range;
96 uint32_t code;
97
98 /*
99 * Number of initializing bytes remaining to be read
100 * by rc_read_init().
101 */
102 uint32_t init_bytes_left;
103
104 /*
105 * Buffer from which we read our input. It can be either
106 * temp.buf or the caller-provided input buffer.
107 */
108 const uint8_t *in;
109 size_t in_pos;
110 size_t in_limit;
111 };
112
113 /* Probabilities for a length decoder. */
114 struct lzma_len_dec {
115 /* Probability of match length being at least 10 */
116 uint16_t choice;
117
118 /* Probability of match length being at least 18 */
119 uint16_t choice2;
120
121 /* Probabilities for match lengths 2-9 */
122 uint16_t low[POS_STATES_MAX][LEN_LOW_SYMBOLS];
123
124 /* Probabilities for match lengths 10-17 */
125 uint16_t mid[POS_STATES_MAX][LEN_MID_SYMBOLS];
126
127 /* Probabilities for match lengths 18-273 */
128 uint16_t high[LEN_HIGH_SYMBOLS];
129 };
130
131 struct lzma_dec {
132 /* Distances of latest four matches */
133 uint32_t rep0;
134 uint32_t rep1;
135 uint32_t rep2;
136 uint32_t rep3;
137
138 /* Types of the most recently seen LZMA symbols */
139 enum lzma_state state;
140
141 /*
142 * Length of a match. This is updated so that dict_repeat can
143 * be called again to finish repeating the whole match.
144 */
145 uint32_t len;
146
147 /*
148 * LZMA properties or related bit masks (number of literal
149 * context bits, a mask derived from the number of literal
150 * position bits, and a mask derived from the number
151 * position bits)
152 */
153 uint32_t lc;
154 uint32_t literal_pos_mask; /* (1 << lp) - 1 */
155 uint32_t pos_mask; /* (1 << pb) - 1 */
156
157 /* If 1, it's a match. Otherwise it's a single 8-bit literal. */
158 uint16_t is_match[STATES][POS_STATES_MAX];
159
160 /* If 1, it's a repeated match. The distance is one of rep0 .. rep3. */
161 uint16_t is_rep[STATES];
162
163 /*
164 * If 0, distance of a repeated match is rep0.
165 * Otherwise check is_rep1.
166 */
167 uint16_t is_rep0[STATES];
168
169 /*
170 * If 0, distance of a repeated match is rep1.
171 * Otherwise check is_rep2.
172 */
173 uint16_t is_rep1[STATES];
174
175 /* If 0, distance of a repeated match is rep2. Otherwise it is rep3. */
176 uint16_t is_rep2[STATES];
177
178 /*
179 * If 1, the repeated match has length of one byte. Otherwise
180 * the length is decoded from rep_len_decoder.
181 */
182 uint16_t is_rep0_long[STATES][POS_STATES_MAX];
183
184 /*
185 * Probability tree for the highest two bits of the match
186 * distance. There is a separate probability tree for match
187 * lengths of 2 (i.e. MATCH_LEN_MIN), 3, 4, and [5, 273].
188 */
189 uint16_t dist_slot[DIST_STATES][DIST_SLOTS];
190
191 /*
192 * Probility trees for additional bits for match distance
193 * when the distance is in the range [4, 127].
194 */
195 uint16_t dist_special[FULL_DISTANCES - DIST_MODEL_END];
196
197 /*
198 * Probability tree for the lowest four bits of a match
199 * distance that is equal to or greater than 128.
200 */
201 uint16_t dist_align[ALIGN_SIZE];
202
203 /* Length of a normal match */
204 struct lzma_len_dec match_len_dec;
205
206 /* Length of a repeated match */
207 struct lzma_len_dec rep_len_dec;
208
209 /* Probabilities of literals */
210 uint16_t literal[LITERAL_CODERS_MAX][LITERAL_CODER_SIZE];
211 };
212
213 struct lzma2_dec {
214 /* Position in xz_dec_lzma2_run(). */
215 enum lzma2_seq {
216 SEQ_CONTROL,
217 SEQ_UNCOMPRESSED_1,
218 SEQ_UNCOMPRESSED_2,
219 SEQ_COMPRESSED_0,
220 SEQ_COMPRESSED_1,
221 SEQ_PROPERTIES,
222 SEQ_LZMA_PREPARE,
223 SEQ_LZMA_RUN,
224 SEQ_COPY
225 } sequence;
226
227 /* Next position after decoding the compressed size of the chunk. */
228 enum lzma2_seq next_sequence;
229
230 /* Uncompressed size of LZMA chunk (2 MiB at maximum) */
231 uint32_t uncompressed;
232
233 /*
234 * Compressed size of LZMA chunk or compressed/uncompressed
235 * size of uncompressed chunk (64 KiB at maximum)
236 */
237 uint32_t compressed;
238
239 /*
240 * True if dictionary reset is needed. This is false before
241 * the first chunk (LZMA or uncompressed).
242 */
243 bool need_dict_reset;
244
245 /*
246 * True if new LZMA properties are needed. This is false
247 * before the first LZMA chunk.
248 */
249 bool need_props;
250
251 #ifdef XZ_DEC_MICROLZMA
252 bool pedantic_microlzma;
253 #endif
254 };
255
256 struct xz_dec_lzma2 {
257 /*
258 * The order below is important on x86 to reduce code size and
259 * it shouldn't hurt on other platforms. Everything up to and
260 * including lzma.pos_mask are in the first 128 bytes on x86-32,
261 * which allows using smaller instructions to access those
262 * variables. On x86-64, fewer variables fit into the first 128
263 * bytes, but this is still the best order without sacrificing
264 * the readability by splitting the structures.
265 */
266 struct rc_dec rc;
267 struct dictionary dict;
268 struct lzma2_dec lzma2;
269 struct lzma_dec lzma;
270
271 /*
272 * Temporary buffer which holds small number of input bytes between
273 * decoder calls. See lzma2_lzma() for details.
274 */
275 struct {
276 uint32_t size;
277 uint8_t buf[3 * LZMA_IN_REQUIRED];
278 } temp;
279 };
280
281 /**************
282 * Dictionary *
283 **************/
284
285 /*
286 * Reset the dictionary state. When in single-call mode, set up the beginning
287 * of the dictionary to point to the actual output buffer.
288 */
dict_reset(struct dictionary * dict,struct xz_buf * b)289 static void dict_reset(struct dictionary *dict, struct xz_buf *b)
290 {
291 if (DEC_IS_SINGLE(dict->mode)) {
292 dict->buf = b->out + b->out_pos;
293 dict->end = b->out_size - b->out_pos;
294 }
295
296 dict->start = 0;
297 dict->pos = 0;
298 dict->limit = 0;
299 dict->full = 0;
300 }
301
302 /* Set dictionary write limit */
dict_limit(struct dictionary * dict,size_t out_max)303 static void dict_limit(struct dictionary *dict, size_t out_max)
304 {
305 if (dict->end - dict->pos <= out_max)
306 dict->limit = dict->end;
307 else
308 dict->limit = dict->pos + out_max;
309 }
310
311 /* Return true if at least one byte can be written into the dictionary. */
dict_has_space(const struct dictionary * dict)312 static inline bool dict_has_space(const struct dictionary *dict)
313 {
314 return dict->pos < dict->limit;
315 }
316
317 /*
318 * Get a byte from the dictionary at the given distance. The distance is
319 * assumed to valid, or as a special case, zero when the dictionary is
320 * still empty. This special case is needed for single-call decoding to
321 * avoid writing a '\0' to the end of the destination buffer.
322 */
dict_get(const struct dictionary * dict,uint32_t dist)323 static inline uint32_t dict_get(const struct dictionary *dict, uint32_t dist)
324 {
325 size_t offset = dict->pos - dist - 1;
326
327 if (dist >= dict->pos)
328 offset += dict->end;
329
330 return dict->full > 0 ? dict->buf[offset] : 0;
331 }
332
333 /*
334 * Put one byte into the dictionary. It is assumed that there is space for it.
335 */
dict_put(struct dictionary * dict,uint8_t byte)336 static inline void dict_put(struct dictionary *dict, uint8_t byte)
337 {
338 dict->buf[dict->pos++] = byte;
339
340 if (dict->full < dict->pos)
341 dict->full = dict->pos;
342 }
343
344 /*
345 * Repeat given number of bytes from the given distance. If the distance is
346 * invalid, false is returned. On success, true is returned and *len is
347 * updated to indicate how many bytes were left to be repeated.
348 */
dict_repeat(struct dictionary * dict,uint32_t * len,uint32_t dist)349 static bool dict_repeat(struct dictionary *dict, uint32_t *len, uint32_t dist)
350 {
351 size_t back;
352 uint32_t left;
353
354 if (dist >= dict->full || dist >= dict->size)
355 return false;
356
357 left = min_t(size_t, dict->limit - dict->pos, *len);
358 *len -= left;
359
360 back = dict->pos - dist - 1;
361 if (dist >= dict->pos)
362 back += dict->end;
363
364 do {
365 dict->buf[dict->pos++] = dict->buf[back++];
366 if (back == dict->end)
367 back = 0;
368 } while (--left > 0);
369
370 if (dict->full < dict->pos)
371 dict->full = dict->pos;
372
373 return true;
374 }
375
376 /* Copy uncompressed data as is from input to dictionary and output buffers. */
dict_uncompressed(struct dictionary * dict,struct xz_buf * b,uint32_t * left)377 static void dict_uncompressed(struct dictionary *dict, struct xz_buf *b,
378 uint32_t *left)
379 {
380 size_t copy_size;
381
382 while (*left > 0 && b->in_pos < b->in_size
383 && b->out_pos < b->out_size) {
384 copy_size = min(b->in_size - b->in_pos,
385 b->out_size - b->out_pos);
386 if (copy_size > dict->end - dict->pos)
387 copy_size = dict->end - dict->pos;
388 if (copy_size > *left)
389 copy_size = *left;
390
391 *left -= copy_size;
392
393 /*
394 * If doing in-place decompression in single-call mode and the
395 * uncompressed size of the file is larger than the caller
396 * thought (i.e. it is invalid input!), the buffers below may
397 * overlap and cause undefined behavior with memcpy().
398 * With valid inputs memcpy() would be fine here.
399 */
400 memmove(dict->buf + dict->pos, b->in + b->in_pos, copy_size);
401 dict->pos += copy_size;
402
403 if (dict->full < dict->pos)
404 dict->full = dict->pos;
405
406 if (DEC_IS_MULTI(dict->mode)) {
407 if (dict->pos == dict->end)
408 dict->pos = 0;
409
410 /*
411 * Like above but for multi-call mode: use memmove()
412 * to avoid undefined behavior with invalid input.
413 */
414 memmove(b->out + b->out_pos, b->in + b->in_pos,
415 copy_size);
416 }
417
418 dict->start = dict->pos;
419
420 b->out_pos += copy_size;
421 b->in_pos += copy_size;
422 }
423 }
424
425 #ifdef XZ_DEC_MICROLZMA
426 # define DICT_FLUSH_SUPPORTS_SKIPPING true
427 #else
428 # define DICT_FLUSH_SUPPORTS_SKIPPING false
429 #endif
430
431 /*
432 * Flush pending data from dictionary to b->out. It is assumed that there is
433 * enough space in b->out. This is guaranteed because caller uses dict_limit()
434 * before decoding data into the dictionary.
435 */
dict_flush(struct dictionary * dict,struct xz_buf * b)436 static uint32_t dict_flush(struct dictionary *dict, struct xz_buf *b)
437 {
438 size_t copy_size = dict->pos - dict->start;
439
440 if (DEC_IS_MULTI(dict->mode)) {
441 if (dict->pos == dict->end)
442 dict->pos = 0;
443
444 /*
445 * These buffers cannot overlap even if doing in-place
446 * decompression because in multi-call mode dict->buf
447 * has been allocated by us in this file; it's not
448 * provided by the caller like in single-call mode.
449 *
450 * With MicroLZMA, b->out can be NULL to skip bytes that
451 * the caller doesn't need. This cannot be done with XZ
452 * because it would break BCJ filters.
453 */
454 if (!DICT_FLUSH_SUPPORTS_SKIPPING || b->out != NULL)
455 memcpy(b->out + b->out_pos, dict->buf + dict->start,
456 copy_size);
457 }
458
459 dict->start = dict->pos;
460 b->out_pos += copy_size;
461 return copy_size;
462 }
463
464 /*****************
465 * Range decoder *
466 *****************/
467
468 /* Reset the range decoder. */
rc_reset(struct rc_dec * rc)469 static void rc_reset(struct rc_dec *rc)
470 {
471 rc->range = (uint32_t)-1;
472 rc->code = 0;
473 rc->init_bytes_left = RC_INIT_BYTES;
474 }
475
476 /*
477 * Read the first five initial bytes into rc->code if they haven't been
478 * read already. (Yes, the first byte gets completely ignored.)
479 */
rc_read_init(struct rc_dec * rc,struct xz_buf * b)480 static bool rc_read_init(struct rc_dec *rc, struct xz_buf *b)
481 {
482 while (rc->init_bytes_left > 0) {
483 if (b->in_pos == b->in_size)
484 return false;
485
486 rc->code = (rc->code << 8) + b->in[b->in_pos++];
487 --rc->init_bytes_left;
488 }
489
490 return true;
491 }
492
493 /* Return true if there may not be enough input for the next decoding loop. */
rc_limit_exceeded(const struct rc_dec * rc)494 static inline bool rc_limit_exceeded(const struct rc_dec *rc)
495 {
496 return rc->in_pos > rc->in_limit;
497 }
498
499 /*
500 * Return true if it is possible (from point of view of range decoder) that
501 * we have reached the end of the LZMA chunk.
502 */
rc_is_finished(const struct rc_dec * rc)503 static inline bool rc_is_finished(const struct rc_dec *rc)
504 {
505 return rc->code == 0;
506 }
507
508 /* Read the next input byte if needed. */
rc_normalize(struct rc_dec * rc)509 static __always_inline void rc_normalize(struct rc_dec *rc)
510 {
511 if (rc->range < RC_TOP_VALUE) {
512 rc->range <<= RC_SHIFT_BITS;
513 rc->code = (rc->code << RC_SHIFT_BITS) + rc->in[rc->in_pos++];
514 }
515 }
516
517 /*
518 * Decode one bit. In some versions, this function has been split in three
519 * functions so that the compiler is supposed to be able to more easily avoid
520 * an extra branch. In this particular version of the LZMA decoder, this
521 * doesn't seem to be a good idea (tested with GCC 3.3.6, 3.4.6, and 4.3.3
522 * on x86). Using a non-split version results in nicer looking code too.
523 *
524 * NOTE: This must return an int. Do not make it return a bool or the speed
525 * of the code generated by GCC 3.x decreases 10-15 %. (GCC 4.3 doesn't care,
526 * and it generates 10-20 % faster code than GCC 3.x from this file anyway.)
527 */
rc_bit(struct rc_dec * rc,uint16_t * prob)528 static __always_inline int rc_bit(struct rc_dec *rc, uint16_t *prob)
529 {
530 uint32_t bound;
531 int bit;
532
533 rc_normalize(rc);
534 bound = (rc->range >> RC_BIT_MODEL_TOTAL_BITS) * *prob;
535 if (rc->code < bound) {
536 rc->range = bound;
537 *prob += (RC_BIT_MODEL_TOTAL - *prob) >> RC_MOVE_BITS;
538 bit = 0;
539 } else {
540 rc->range -= bound;
541 rc->code -= bound;
542 *prob -= *prob >> RC_MOVE_BITS;
543 bit = 1;
544 }
545
546 return bit;
547 }
548
549 /* Decode a bittree starting from the most significant bit. */
rc_bittree(struct rc_dec * rc,uint16_t * probs,uint32_t limit)550 static __always_inline uint32_t rc_bittree(struct rc_dec *rc,
551 uint16_t *probs, uint32_t limit)
552 {
553 uint32_t symbol = 1;
554
555 do {
556 if (rc_bit(rc, &probs[symbol]))
557 symbol = (symbol << 1) + 1;
558 else
559 symbol <<= 1;
560 } while (symbol < limit);
561
562 return symbol;
563 }
564
565 /* Decode a bittree starting from the least significant bit. */
rc_bittree_reverse(struct rc_dec * rc,uint16_t * probs,uint32_t * dest,uint32_t limit)566 static __always_inline void rc_bittree_reverse(struct rc_dec *rc,
567 uint16_t *probs,
568 uint32_t *dest, uint32_t limit)
569 {
570 uint32_t symbol = 1;
571 uint32_t i = 0;
572
573 do {
574 if (rc_bit(rc, &probs[symbol])) {
575 symbol = (symbol << 1) + 1;
576 *dest += 1 << i;
577 } else {
578 symbol <<= 1;
579 }
580 } while (++i < limit);
581 }
582
583 /* Decode direct bits (fixed fifty-fifty probability) */
rc_direct(struct rc_dec * rc,uint32_t * dest,uint32_t limit)584 static inline void rc_direct(struct rc_dec *rc, uint32_t *dest, uint32_t limit)
585 {
586 uint32_t mask;
587
588 do {
589 rc_normalize(rc);
590 rc->range >>= 1;
591 rc->code -= rc->range;
592 mask = (uint32_t)0 - (rc->code >> 31);
593 rc->code += rc->range & mask;
594 *dest = (*dest << 1) + (mask + 1);
595 } while (--limit > 0);
596 }
597
598 /********
599 * LZMA *
600 ********/
601
602 /* Get pointer to literal coder probability array. */
lzma_literal_probs(struct xz_dec_lzma2 * s)603 static uint16_t *lzma_literal_probs(struct xz_dec_lzma2 *s)
604 {
605 uint32_t prev_byte = dict_get(&s->dict, 0);
606 uint32_t low = prev_byte >> (8 - s->lzma.lc);
607 uint32_t high = (s->dict.pos & s->lzma.literal_pos_mask) << s->lzma.lc;
608 return s->lzma.literal[low + high];
609 }
610
611 /* Decode a literal (one 8-bit byte) */
lzma_literal(struct xz_dec_lzma2 * s)612 static void lzma_literal(struct xz_dec_lzma2 *s)
613 {
614 uint16_t *probs;
615 uint32_t symbol;
616 uint32_t match_byte;
617 uint32_t match_bit;
618 uint32_t offset;
619 uint32_t i;
620
621 probs = lzma_literal_probs(s);
622
623 if (lzma_state_is_literal(s->lzma.state)) {
624 symbol = rc_bittree(&s->rc, probs, 0x100);
625 } else {
626 symbol = 1;
627 match_byte = dict_get(&s->dict, s->lzma.rep0) << 1;
628 offset = 0x100;
629
630 do {
631 match_bit = match_byte & offset;
632 match_byte <<= 1;
633 i = offset + match_bit + symbol;
634
635 if (rc_bit(&s->rc, &probs[i])) {
636 symbol = (symbol << 1) + 1;
637 offset &= match_bit;
638 } else {
639 symbol <<= 1;
640 offset &= ~match_bit;
641 }
642 } while (symbol < 0x100);
643 }
644
645 dict_put(&s->dict, (uint8_t)symbol);
646 lzma_state_literal(&s->lzma.state);
647 }
648
649 /* Decode the length of the match into s->lzma.len. */
lzma_len(struct xz_dec_lzma2 * s,struct lzma_len_dec * l,uint32_t pos_state)650 static void lzma_len(struct xz_dec_lzma2 *s, struct lzma_len_dec *l,
651 uint32_t pos_state)
652 {
653 uint16_t *probs;
654 uint32_t limit;
655
656 if (!rc_bit(&s->rc, &l->choice)) {
657 probs = l->low[pos_state];
658 limit = LEN_LOW_SYMBOLS;
659 s->lzma.len = MATCH_LEN_MIN;
660 } else {
661 if (!rc_bit(&s->rc, &l->choice2)) {
662 probs = l->mid[pos_state];
663 limit = LEN_MID_SYMBOLS;
664 s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS;
665 } else {
666 probs = l->high;
667 limit = LEN_HIGH_SYMBOLS;
668 s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS
669 + LEN_MID_SYMBOLS;
670 }
671 }
672
673 s->lzma.len += rc_bittree(&s->rc, probs, limit) - limit;
674 }
675
676 /* Decode a match. The distance will be stored in s->lzma.rep0. */
lzma_match(struct xz_dec_lzma2 * s,uint32_t pos_state)677 static void lzma_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
678 {
679 uint16_t *probs;
680 uint32_t dist_slot;
681 uint32_t limit;
682
683 lzma_state_match(&s->lzma.state);
684
685 s->lzma.rep3 = s->lzma.rep2;
686 s->lzma.rep2 = s->lzma.rep1;
687 s->lzma.rep1 = s->lzma.rep0;
688
689 lzma_len(s, &s->lzma.match_len_dec, pos_state);
690
691 probs = s->lzma.dist_slot[lzma_get_dist_state(s->lzma.len)];
692 dist_slot = rc_bittree(&s->rc, probs, DIST_SLOTS) - DIST_SLOTS;
693
694 if (dist_slot < DIST_MODEL_START) {
695 s->lzma.rep0 = dist_slot;
696 } else {
697 limit = (dist_slot >> 1) - 1;
698 s->lzma.rep0 = 2 + (dist_slot & 1);
699
700 if (dist_slot < DIST_MODEL_END) {
701 s->lzma.rep0 <<= limit;
702 probs = s->lzma.dist_special + s->lzma.rep0
703 - dist_slot - 1;
704 rc_bittree_reverse(&s->rc, probs,
705 &s->lzma.rep0, limit);
706 } else {
707 rc_direct(&s->rc, &s->lzma.rep0, limit - ALIGN_BITS);
708 s->lzma.rep0 <<= ALIGN_BITS;
709 rc_bittree_reverse(&s->rc, s->lzma.dist_align,
710 &s->lzma.rep0, ALIGN_BITS);
711 }
712 }
713 }
714
715 /*
716 * Decode a repeated match. The distance is one of the four most recently
717 * seen matches. The distance will be stored in s->lzma.rep0.
718 */
lzma_rep_match(struct xz_dec_lzma2 * s,uint32_t pos_state)719 static void lzma_rep_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
720 {
721 uint32_t tmp;
722
723 if (!rc_bit(&s->rc, &s->lzma.is_rep0[s->lzma.state])) {
724 if (!rc_bit(&s->rc, &s->lzma.is_rep0_long[
725 s->lzma.state][pos_state])) {
726 lzma_state_short_rep(&s->lzma.state);
727 s->lzma.len = 1;
728 return;
729 }
730 } else {
731 if (!rc_bit(&s->rc, &s->lzma.is_rep1[s->lzma.state])) {
732 tmp = s->lzma.rep1;
733 } else {
734 if (!rc_bit(&s->rc, &s->lzma.is_rep2[s->lzma.state])) {
735 tmp = s->lzma.rep2;
736 } else {
737 tmp = s->lzma.rep3;
738 s->lzma.rep3 = s->lzma.rep2;
739 }
740
741 s->lzma.rep2 = s->lzma.rep1;
742 }
743
744 s->lzma.rep1 = s->lzma.rep0;
745 s->lzma.rep0 = tmp;
746 }
747
748 lzma_state_long_rep(&s->lzma.state);
749 lzma_len(s, &s->lzma.rep_len_dec, pos_state);
750 }
751
752 /* LZMA decoder core */
lzma_main(struct xz_dec_lzma2 * s)753 static bool lzma_main(struct xz_dec_lzma2 *s)
754 {
755 uint32_t pos_state;
756
757 /*
758 * If the dictionary was reached during the previous call, try to
759 * finish the possibly pending repeat in the dictionary.
760 */
761 if (dict_has_space(&s->dict) && s->lzma.len > 0)
762 dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0);
763
764 /*
765 * Decode more LZMA symbols. One iteration may consume up to
766 * LZMA_IN_REQUIRED - 1 bytes.
767 */
768 while (dict_has_space(&s->dict) && !rc_limit_exceeded(&s->rc)) {
769 pos_state = s->dict.pos & s->lzma.pos_mask;
770
771 if (!rc_bit(&s->rc, &s->lzma.is_match[
772 s->lzma.state][pos_state])) {
773 lzma_literal(s);
774 } else {
775 if (rc_bit(&s->rc, &s->lzma.is_rep[s->lzma.state]))
776 lzma_rep_match(s, pos_state);
777 else
778 lzma_match(s, pos_state);
779
780 if (!dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0))
781 return false;
782 }
783 }
784
785 /*
786 * Having the range decoder always normalized when we are outside
787 * this function makes it easier to correctly handle end of the chunk.
788 */
789 rc_normalize(&s->rc);
790
791 return true;
792 }
793
794 /*
795 * Reset the LZMA decoder and range decoder state. Dictionary is not reset
796 * here, because LZMA state may be reset without resetting the dictionary.
797 */
lzma_reset(struct xz_dec_lzma2 * s)798 static void lzma_reset(struct xz_dec_lzma2 *s)
799 {
800 uint16_t *probs;
801 size_t i;
802
803 s->lzma.state = STATE_LIT_LIT;
804 s->lzma.rep0 = 0;
805 s->lzma.rep1 = 0;
806 s->lzma.rep2 = 0;
807 s->lzma.rep3 = 0;
808 s->lzma.len = 0;
809
810 /*
811 * All probabilities are initialized to the same value. This hack
812 * makes the code smaller by avoiding a separate loop for each
813 * probability array.
814 *
815 * This could be optimized so that only that part of literal
816 * probabilities that are actually required. In the common case
817 * we would write 12 KiB less.
818 */
819 probs = s->lzma.is_match[0];
820 for (i = 0; i < PROBS_TOTAL; ++i)
821 probs[i] = RC_BIT_MODEL_TOTAL / 2;
822
823 rc_reset(&s->rc);
824 }
825
826 /*
827 * Decode and validate LZMA properties (lc/lp/pb) and calculate the bit masks
828 * from the decoded lp and pb values. On success, the LZMA decoder state is
829 * reset and true is returned.
830 */
lzma_props(struct xz_dec_lzma2 * s,uint8_t props)831 static bool lzma_props(struct xz_dec_lzma2 *s, uint8_t props)
832 {
833 if (props > (4 * 5 + 4) * 9 + 8)
834 return false;
835
836 s->lzma.pos_mask = 0;
837 while (props >= 9 * 5) {
838 props -= 9 * 5;
839 ++s->lzma.pos_mask;
840 }
841
842 s->lzma.pos_mask = (1 << s->lzma.pos_mask) - 1;
843
844 s->lzma.literal_pos_mask = 0;
845 while (props >= 9) {
846 props -= 9;
847 ++s->lzma.literal_pos_mask;
848 }
849
850 s->lzma.lc = props;
851
852 if (s->lzma.lc + s->lzma.literal_pos_mask > 4)
853 return false;
854
855 s->lzma.literal_pos_mask = (1 << s->lzma.literal_pos_mask) - 1;
856
857 lzma_reset(s);
858
859 return true;
860 }
861
862 /*********
863 * LZMA2 *
864 *********/
865
866 /*
867 * The LZMA decoder assumes that if the input limit (s->rc.in_limit) hasn't
868 * been exceeded, it is safe to read up to LZMA_IN_REQUIRED bytes. This
869 * wrapper function takes care of making the LZMA decoder's assumption safe.
870 *
871 * As long as there is plenty of input left to be decoded in the current LZMA
872 * chunk, we decode directly from the caller-supplied input buffer until
873 * there's LZMA_IN_REQUIRED bytes left. Those remaining bytes are copied into
874 * s->temp.buf, which (hopefully) gets filled on the next call to this
875 * function. We decode a few bytes from the temporary buffer so that we can
876 * continue decoding from the caller-supplied input buffer again.
877 */
lzma2_lzma(struct xz_dec_lzma2 * s,struct xz_buf * b)878 static bool lzma2_lzma(struct xz_dec_lzma2 *s, struct xz_buf *b)
879 {
880 size_t in_avail;
881 uint32_t tmp;
882
883 in_avail = b->in_size - b->in_pos;
884 if (s->temp.size > 0 || s->lzma2.compressed == 0) {
885 tmp = 2 * LZMA_IN_REQUIRED - s->temp.size;
886 if (tmp > s->lzma2.compressed - s->temp.size)
887 tmp = s->lzma2.compressed - s->temp.size;
888 if (tmp > in_avail)
889 tmp = in_avail;
890
891 memcpy(s->temp.buf + s->temp.size, b->in + b->in_pos, tmp);
892
893 if (s->temp.size + tmp == s->lzma2.compressed) {
894 memzero(s->temp.buf + s->temp.size + tmp,
895 sizeof(s->temp.buf)
896 - s->temp.size - tmp);
897 s->rc.in_limit = s->temp.size + tmp;
898 } else if (s->temp.size + tmp < LZMA_IN_REQUIRED) {
899 s->temp.size += tmp;
900 b->in_pos += tmp;
901 return true;
902 } else {
903 s->rc.in_limit = s->temp.size + tmp - LZMA_IN_REQUIRED;
904 }
905
906 s->rc.in = s->temp.buf;
907 s->rc.in_pos = 0;
908
909 if (!lzma_main(s) || s->rc.in_pos > s->temp.size + tmp)
910 return false;
911
912 s->lzma2.compressed -= s->rc.in_pos;
913
914 if (s->rc.in_pos < s->temp.size) {
915 s->temp.size -= s->rc.in_pos;
916 memmove(s->temp.buf, s->temp.buf + s->rc.in_pos,
917 s->temp.size);
918 return true;
919 }
920
921 b->in_pos += s->rc.in_pos - s->temp.size;
922 s->temp.size = 0;
923 }
924
925 in_avail = b->in_size - b->in_pos;
926 if (in_avail >= LZMA_IN_REQUIRED) {
927 s->rc.in = b->in;
928 s->rc.in_pos = b->in_pos;
929
930 if (in_avail >= s->lzma2.compressed + LZMA_IN_REQUIRED)
931 s->rc.in_limit = b->in_pos + s->lzma2.compressed;
932 else
933 s->rc.in_limit = b->in_size - LZMA_IN_REQUIRED;
934
935 if (!lzma_main(s))
936 return false;
937
938 in_avail = s->rc.in_pos - b->in_pos;
939 if (in_avail > s->lzma2.compressed)
940 return false;
941
942 s->lzma2.compressed -= in_avail;
943 b->in_pos = s->rc.in_pos;
944 }
945
946 in_avail = b->in_size - b->in_pos;
947 if (in_avail < LZMA_IN_REQUIRED) {
948 if (in_avail > s->lzma2.compressed)
949 in_avail = s->lzma2.compressed;
950
951 memcpy(s->temp.buf, b->in + b->in_pos, in_avail);
952 s->temp.size = in_avail;
953 b->in_pos += in_avail;
954 }
955
956 return true;
957 }
958
959 /*
960 * Take care of the LZMA2 control layer, and forward the job of actual LZMA
961 * decoding or copying of uncompressed chunks to other functions.
962 */
xz_dec_lzma2_run(struct xz_dec_lzma2 * s,struct xz_buf * b)963 enum xz_ret xz_dec_lzma2_run(struct xz_dec_lzma2 *s, struct xz_buf *b)
964 {
965 uint32_t tmp;
966
967 while (b->in_pos < b->in_size || s->lzma2.sequence == SEQ_LZMA_RUN) {
968 switch (s->lzma2.sequence) {
969 case SEQ_CONTROL:
970 /*
971 * LZMA2 control byte
972 *
973 * Exact values:
974 * 0x00 End marker
975 * 0x01 Dictionary reset followed by
976 * an uncompressed chunk
977 * 0x02 Uncompressed chunk (no dictionary reset)
978 *
979 * Highest three bits (s->control & 0xE0):
980 * 0xE0 Dictionary reset, new properties and state
981 * reset, followed by LZMA compressed chunk
982 * 0xC0 New properties and state reset, followed
983 * by LZMA compressed chunk (no dictionary
984 * reset)
985 * 0xA0 State reset using old properties,
986 * followed by LZMA compressed chunk (no
987 * dictionary reset)
988 * 0x80 LZMA chunk (no dictionary or state reset)
989 *
990 * For LZMA compressed chunks, the lowest five bits
991 * (s->control & 1F) are the highest bits of the
992 * uncompressed size (bits 16-20).
993 *
994 * A new LZMA2 stream must begin with a dictionary
995 * reset. The first LZMA chunk must set new
996 * properties and reset the LZMA state.
997 *
998 * Values that don't match anything described above
999 * are invalid and we return XZ_DATA_ERROR.
1000 */
1001 tmp = b->in[b->in_pos++];
1002
1003 if (tmp == 0x00)
1004 return XZ_STREAM_END;
1005
1006 if (tmp >= 0xE0 || tmp == 0x01) {
1007 s->lzma2.need_props = true;
1008 s->lzma2.need_dict_reset = false;
1009 dict_reset(&s->dict, b);
1010 } else if (s->lzma2.need_dict_reset) {
1011 return XZ_DATA_ERROR;
1012 }
1013
1014 if (tmp >= 0x80) {
1015 s->lzma2.uncompressed = (tmp & 0x1F) << 16;
1016 s->lzma2.sequence = SEQ_UNCOMPRESSED_1;
1017
1018 if (tmp >= 0xC0) {
1019 /*
1020 * When there are new properties,
1021 * state reset is done at
1022 * SEQ_PROPERTIES.
1023 */
1024 s->lzma2.need_props = false;
1025 s->lzma2.next_sequence
1026 = SEQ_PROPERTIES;
1027
1028 } else if (s->lzma2.need_props) {
1029 return XZ_DATA_ERROR;
1030
1031 } else {
1032 s->lzma2.next_sequence
1033 = SEQ_LZMA_PREPARE;
1034 if (tmp >= 0xA0)
1035 lzma_reset(s);
1036 }
1037 } else {
1038 if (tmp > 0x02)
1039 return XZ_DATA_ERROR;
1040
1041 s->lzma2.sequence = SEQ_COMPRESSED_0;
1042 s->lzma2.next_sequence = SEQ_COPY;
1043 }
1044
1045 break;
1046
1047 case SEQ_UNCOMPRESSED_1:
1048 s->lzma2.uncompressed
1049 += (uint32_t)b->in[b->in_pos++] << 8;
1050 s->lzma2.sequence = SEQ_UNCOMPRESSED_2;
1051 break;
1052
1053 case SEQ_UNCOMPRESSED_2:
1054 s->lzma2.uncompressed
1055 += (uint32_t)b->in[b->in_pos++] + 1;
1056 s->lzma2.sequence = SEQ_COMPRESSED_0;
1057 break;
1058
1059 case SEQ_COMPRESSED_0:
1060 s->lzma2.compressed
1061 = (uint32_t)b->in[b->in_pos++] << 8;
1062 s->lzma2.sequence = SEQ_COMPRESSED_1;
1063 break;
1064
1065 case SEQ_COMPRESSED_1:
1066 s->lzma2.compressed
1067 += (uint32_t)b->in[b->in_pos++] + 1;
1068 s->lzma2.sequence = s->lzma2.next_sequence;
1069 break;
1070
1071 case SEQ_PROPERTIES:
1072 if (!lzma_props(s, b->in[b->in_pos++]))
1073 return XZ_DATA_ERROR;
1074
1075 s->lzma2.sequence = SEQ_LZMA_PREPARE;
1076
1077 fallthrough;
1078
1079 case SEQ_LZMA_PREPARE:
1080 if (s->lzma2.compressed < RC_INIT_BYTES)
1081 return XZ_DATA_ERROR;
1082
1083 if (!rc_read_init(&s->rc, b))
1084 return XZ_OK;
1085
1086 s->lzma2.compressed -= RC_INIT_BYTES;
1087 s->lzma2.sequence = SEQ_LZMA_RUN;
1088
1089 fallthrough;
1090
1091 case SEQ_LZMA_RUN:
1092 /*
1093 * Set dictionary limit to indicate how much we want
1094 * to be encoded at maximum. Decode new data into the
1095 * dictionary. Flush the new data from dictionary to
1096 * b->out. Check if we finished decoding this chunk.
1097 * In case the dictionary got full but we didn't fill
1098 * the output buffer yet, we may run this loop
1099 * multiple times without changing s->lzma2.sequence.
1100 */
1101 dict_limit(&s->dict, min_t(size_t,
1102 b->out_size - b->out_pos,
1103 s->lzma2.uncompressed));
1104 if (!lzma2_lzma(s, b))
1105 return XZ_DATA_ERROR;
1106
1107 s->lzma2.uncompressed -= dict_flush(&s->dict, b);
1108
1109 if (s->lzma2.uncompressed == 0) {
1110 if (s->lzma2.compressed > 0 || s->lzma.len > 0
1111 || !rc_is_finished(&s->rc))
1112 return XZ_DATA_ERROR;
1113
1114 rc_reset(&s->rc);
1115 s->lzma2.sequence = SEQ_CONTROL;
1116
1117 } else if (b->out_pos == b->out_size
1118 || (b->in_pos == b->in_size
1119 && s->temp.size
1120 < s->lzma2.compressed)) {
1121 return XZ_OK;
1122 }
1123
1124 break;
1125
1126 case SEQ_COPY:
1127 dict_uncompressed(&s->dict, b, &s->lzma2.compressed);
1128 if (s->lzma2.compressed > 0)
1129 return XZ_OK;
1130
1131 s->lzma2.sequence = SEQ_CONTROL;
1132 break;
1133 }
1134 }
1135
1136 return XZ_OK;
1137 }
1138
xz_dec_lzma2_create(enum xz_mode mode,uint32_t dict_max)1139 struct xz_dec_lzma2 *xz_dec_lzma2_create(enum xz_mode mode, uint32_t dict_max)
1140 {
1141 struct xz_dec_lzma2 *s = kmalloc(sizeof(*s), GFP_KERNEL);
1142 if (s == NULL)
1143 return NULL;
1144
1145 s->dict.mode = mode;
1146 s->dict.size_max = dict_max;
1147
1148 if (DEC_IS_PREALLOC(mode)) {
1149 s->dict.buf = vmalloc(dict_max);
1150 if (s->dict.buf == NULL) {
1151 kfree(s);
1152 return NULL;
1153 }
1154 } else if (DEC_IS_DYNALLOC(mode)) {
1155 s->dict.buf = NULL;
1156 s->dict.allocated = 0;
1157 }
1158
1159 return s;
1160 }
1161
xz_dec_lzma2_reset(struct xz_dec_lzma2 * s,uint8_t props)1162 enum xz_ret xz_dec_lzma2_reset(struct xz_dec_lzma2 *s, uint8_t props)
1163 {
1164 /* This limits dictionary size to 3 GiB to keep parsing simpler. */
1165 if (props > 39)
1166 return XZ_OPTIONS_ERROR;
1167
1168 s->dict.size = 2 + (props & 1);
1169 s->dict.size <<= (props >> 1) + 11;
1170
1171 if (DEC_IS_MULTI(s->dict.mode)) {
1172 if (s->dict.size > s->dict.size_max)
1173 return XZ_MEMLIMIT_ERROR;
1174
1175 s->dict.end = s->dict.size;
1176
1177 if (DEC_IS_DYNALLOC(s->dict.mode)) {
1178 if (s->dict.allocated < s->dict.size) {
1179 s->dict.allocated = s->dict.size;
1180 vfree(s->dict.buf);
1181 s->dict.buf = vmalloc(s->dict.size);
1182 if (s->dict.buf == NULL) {
1183 s->dict.allocated = 0;
1184 return XZ_MEM_ERROR;
1185 }
1186 }
1187 }
1188 }
1189
1190 s->lzma2.sequence = SEQ_CONTROL;
1191 s->lzma2.need_dict_reset = true;
1192
1193 s->temp.size = 0;
1194
1195 return XZ_OK;
1196 }
1197
xz_dec_lzma2_end(struct xz_dec_lzma2 * s)1198 void xz_dec_lzma2_end(struct xz_dec_lzma2 *s)
1199 {
1200 if (DEC_IS_MULTI(s->dict.mode))
1201 vfree(s->dict.buf);
1202
1203 kfree(s);
1204 }
1205
1206 #ifdef XZ_DEC_MICROLZMA
1207 /* This is a wrapper struct to have a nice struct name in the public API. */
1208 struct xz_dec_microlzma {
1209 struct xz_dec_lzma2 s;
1210 };
1211
xz_dec_microlzma_run(struct xz_dec_microlzma * s_ptr,struct xz_buf * b)1212 enum xz_ret xz_dec_microlzma_run(struct xz_dec_microlzma *s_ptr,
1213 struct xz_buf *b)
1214 {
1215 struct xz_dec_lzma2 *s = &s_ptr->s;
1216
1217 /*
1218 * sequence is SEQ_PROPERTIES before the first input byte,
1219 * SEQ_LZMA_PREPARE until a total of five bytes have been read,
1220 * and SEQ_LZMA_RUN for the rest of the input stream.
1221 */
1222 if (s->lzma2.sequence != SEQ_LZMA_RUN) {
1223 if (s->lzma2.sequence == SEQ_PROPERTIES) {
1224 /* One byte is needed for the props. */
1225 if (b->in_pos >= b->in_size)
1226 return XZ_OK;
1227
1228 /*
1229 * Don't increment b->in_pos here. The same byte is
1230 * also passed to rc_read_init() which will ignore it.
1231 */
1232 if (!lzma_props(s, ~b->in[b->in_pos]))
1233 return XZ_DATA_ERROR;
1234
1235 s->lzma2.sequence = SEQ_LZMA_PREPARE;
1236 }
1237
1238 /*
1239 * xz_dec_microlzma_reset() doesn't validate the compressed
1240 * size so we do it here. We have to limit the maximum size
1241 * to avoid integer overflows in lzma2_lzma(). 3 GiB is a nice
1242 * round number and much more than users of this code should
1243 * ever need.
1244 */
1245 if (s->lzma2.compressed < RC_INIT_BYTES
1246 || s->lzma2.compressed > (3U << 30))
1247 return XZ_DATA_ERROR;
1248
1249 if (!rc_read_init(&s->rc, b))
1250 return XZ_OK;
1251
1252 s->lzma2.compressed -= RC_INIT_BYTES;
1253 s->lzma2.sequence = SEQ_LZMA_RUN;
1254
1255 dict_reset(&s->dict, b);
1256 }
1257
1258 /* This is to allow increasing b->out_size between calls. */
1259 if (DEC_IS_SINGLE(s->dict.mode))
1260 s->dict.end = b->out_size - b->out_pos;
1261
1262 while (true) {
1263 dict_limit(&s->dict, min_t(size_t, b->out_size - b->out_pos,
1264 s->lzma2.uncompressed));
1265
1266 if (!lzma2_lzma(s, b))
1267 return XZ_DATA_ERROR;
1268
1269 s->lzma2.uncompressed -= dict_flush(&s->dict, b);
1270
1271 if (s->lzma2.uncompressed == 0) {
1272 if (s->lzma2.pedantic_microlzma) {
1273 if (s->lzma2.compressed > 0 || s->lzma.len > 0
1274 || !rc_is_finished(&s->rc))
1275 return XZ_DATA_ERROR;
1276 }
1277
1278 return XZ_STREAM_END;
1279 }
1280
1281 if (b->out_pos == b->out_size)
1282 return XZ_OK;
1283
1284 if (b->in_pos == b->in_size
1285 && s->temp.size < s->lzma2.compressed)
1286 return XZ_OK;
1287 }
1288 }
1289
xz_dec_microlzma_alloc(enum xz_mode mode,uint32_t dict_size)1290 struct xz_dec_microlzma *xz_dec_microlzma_alloc(enum xz_mode mode,
1291 uint32_t dict_size)
1292 {
1293 struct xz_dec_microlzma *s;
1294
1295 /* Restrict dict_size to the same range as in the LZMA2 code. */
1296 if (dict_size < 4096 || dict_size > (3U << 30))
1297 return NULL;
1298
1299 s = kmalloc(sizeof(*s), GFP_KERNEL);
1300 if (s == NULL)
1301 return NULL;
1302
1303 s->s.dict.mode = mode;
1304 s->s.dict.size = dict_size;
1305
1306 if (DEC_IS_MULTI(mode)) {
1307 s->s.dict.end = dict_size;
1308
1309 s->s.dict.buf = vmalloc(dict_size);
1310 if (s->s.dict.buf == NULL) {
1311 kfree(s);
1312 return NULL;
1313 }
1314 }
1315
1316 return s;
1317 }
1318
xz_dec_microlzma_reset(struct xz_dec_microlzma * s,uint32_t comp_size,uint32_t uncomp_size,int uncomp_size_is_exact)1319 void xz_dec_microlzma_reset(struct xz_dec_microlzma *s, uint32_t comp_size,
1320 uint32_t uncomp_size, int uncomp_size_is_exact)
1321 {
1322 /*
1323 * comp_size is validated in xz_dec_microlzma_run().
1324 * uncomp_size can safely be anything.
1325 */
1326 s->s.lzma2.compressed = comp_size;
1327 s->s.lzma2.uncompressed = uncomp_size;
1328 s->s.lzma2.pedantic_microlzma = uncomp_size_is_exact;
1329
1330 s->s.lzma2.sequence = SEQ_PROPERTIES;
1331 s->s.temp.size = 0;
1332 }
1333
xz_dec_microlzma_end(struct xz_dec_microlzma * s)1334 void xz_dec_microlzma_end(struct xz_dec_microlzma *s)
1335 {
1336 if (DEC_IS_MULTI(s->s.dict.mode))
1337 vfree(s->s.dict.buf);
1338
1339 kfree(s);
1340 }
1341 #endif
1342