summaryrefslogtreecommitdiff
path: root/data/libmad/length-check.diff
blob: 80e48469e6523d21035e24804ac8411a3062c40e (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
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
From: Kurt Roeckx <kurt@roeckx.be>
Date: Sun, 28 Jan 2018 19:26:36 +0100
Subject: Check the size before reading with mad_bit_read

There are various cases where it attemps to read past the end of the buffer
using mad_bit_read(). Most functions didn't even know the size of the buffer
they were reading from.

Index: libmad-0.15.1b/bit.c
===================================================================
--- libmad-0.15.1b.orig/bit.c
+++ libmad-0.15.1b/bit.c
@@ -138,6 +138,9 @@ unsigned long mad_bit_read(struct mad_bi
 {
   register unsigned long value;
 
+  if (len == 0)
+    return 0;
+
   if (bitptr->left == CHAR_BIT)
     bitptr->cache = *bitptr->byte;
 
Index: libmad-0.15.1b/frame.c
===================================================================
--- libmad-0.15.1b.orig/frame.c
+++ libmad-0.15.1b/frame.c
@@ -120,11 +120,18 @@ static
 int decode_header(struct mad_header *header, struct mad_stream *stream)
 {
   unsigned int index;
+  struct mad_bitptr bufend_ptr;
 
   header->flags        = 0;
   header->private_bits = 0;
 
+  mad_bit_init(&bufend_ptr, stream->bufend);
+
   /* header() */
+  if (mad_bit_length(&stream->ptr, &bufend_ptr) < 32) {
+    stream->error = MAD_ERROR_BUFLEN;
+    return -1;
+  }
 
   /* syncword */
   mad_bit_skip(&stream->ptr, 11);
@@ -225,8 +232,13 @@ int decode_header(struct mad_header *hea
   /* error_check() */
 
   /* crc_check */
-  if (header->flags & MAD_FLAG_PROTECTION)
+  if (header->flags & MAD_FLAG_PROTECTION) {
+    if (mad_bit_length(&stream->ptr, &bufend_ptr) < 16) {
+      stream->error = MAD_ERROR_BUFLEN;
+      return -1;
+    }
     header->crc_target = mad_bit_read(&stream->ptr, 16);
+  }
 
   return 0;
 }
@@ -338,7 +350,7 @@ int mad_header_decode(struct mad_header
       stream->error = MAD_ERROR_BUFLEN;
       goto fail;
     }
-    else if (!(ptr[0] == 0xff && (ptr[1] & 0xe0) == 0xe0)) {
+    else if ((end - ptr >= 2) && !(ptr[0] == 0xff && (ptr[1] & 0xe0) == 0xe0)) {
       /* mark point where frame sync word was expected */
       stream->this_frame = ptr;
       stream->next_frame = ptr + 1;
@@ -361,6 +373,8 @@ int mad_header_decode(struct mad_header
     ptr = mad_bit_nextbyte(&stream->ptr);
   }
 
+  stream->error = MAD_ERROR_NONE;
+
   /* begin processing */
   stream->this_frame = ptr;
   stream->next_frame = ptr + 1;  /* possibly bogus sync word */
@@ -413,7 +427,7 @@ int mad_header_decode(struct mad_header
     /* check that a valid frame header follows this frame */
 
     ptr = stream->next_frame;
-    if (!(ptr[0] == 0xff && (ptr[1] & 0xe0) == 0xe0)) {
+    if ((end - ptr >= 2) && !(ptr[0] == 0xff && (ptr[1] & 0xe0) == 0xe0)) {
       ptr = stream->next_frame = stream->this_frame + 1;
       goto sync;
     }
Index: libmad-0.15.1b/layer12.c
===================================================================
--- libmad-0.15.1b.orig/layer12.c
+++ libmad-0.15.1b/layer12.c
@@ -72,10 +72,18 @@ mad_fixed_t const linear_table[14] = {
  * DESCRIPTION:	decode one requantized Layer I sample from a bitstream
  */
 static
-mad_fixed_t I_sample(struct mad_bitptr *ptr, unsigned int nb)
+mad_fixed_t I_sample(struct mad_bitptr *ptr, unsigned int nb, struct mad_stream *stream)
 {
   mad_fixed_t sample;
+  struct mad_bitptr frameend_ptr;
 
+  mad_bit_init(&frameend_ptr, stream->next_frame);
+
+  if (mad_bit_length(ptr, &frameend_ptr) < nb) {
+    stream->error = MAD_ERROR_LOSTSYNC;
+    stream->sync = 0;
+    return 0;
+  }
   sample = mad_bit_read(ptr, nb);
 
   /* invert most significant bit, extend sign, then scale to fixed format */
@@ -106,6 +114,10 @@ int mad_layer_I(struct mad_stream *strea
   struct mad_header *header = &frame->header;
   unsigned int nch, bound, ch, s, sb, nb;
   unsigned char allocation[2][32], scalefactor[2][32];
+  struct mad_bitptr bufend_ptr, frameend_ptr;
+
+  mad_bit_init(&bufend_ptr, stream->bufend);
+  mad_bit_init(&frameend_ptr, stream->next_frame);
 
   nch = MAD_NCHANNELS(header);
 
@@ -118,6 +130,11 @@ int mad_layer_I(struct mad_stream *strea
   /* check CRC word */
 
   if (header->flags & MAD_FLAG_PROTECTION) {
+    if (mad_bit_length(&stream->ptr, &bufend_ptr)
+		< 4 * (bound * nch + (32 - bound))) {
+      stream->error = MAD_ERROR_BADCRC;
+      return -1;
+    }
     header->crc_check =
       mad_bit_crc(stream->ptr, 4 * (bound * nch + (32 - bound)),
 		  header->crc_check);
@@ -133,6 +150,11 @@ int mad_layer_I(struct mad_stream *strea
 
   for (sb = 0; sb < bound; ++sb) {
     for (ch = 0; ch < nch; ++ch) {
+      if (mad_bit_length(&stream->ptr, &frameend_ptr) < 4) {
+	stream->error = MAD_ERROR_LOSTSYNC;
+	stream->sync = 0;
+	return -1;
+      }
       nb = mad_bit_read(&stream->ptr, 4);
 
       if (nb == 15) {
@@ -145,6 +167,11 @@ int mad_layer_I(struct mad_stream *strea
   }
 
   for (sb = bound; sb < 32; ++sb) {
+    if (mad_bit_length(&stream->ptr, &frameend_ptr) < 4) {
+      stream->error = MAD_ERROR_LOSTSYNC;
+      stream->sync = 0;
+      return -1;
+    }
     nb = mad_bit_read(&stream->ptr, 4);
 
     if (nb == 15) {
@@ -161,6 +188,11 @@ int mad_layer_I(struct mad_stream *strea
   for (sb = 0; sb < 32; ++sb) {
     for (ch = 0; ch < nch; ++ch) {
       if (allocation[ch][sb]) {
+        if (mad_bit_length(&stream->ptr, &frameend_ptr) < 6) {
+	  stream->error = MAD_ERROR_LOSTSYNC;
+	  stream->sync = 0;
+	  return -1;
+	}
 	scalefactor[ch][sb] = mad_bit_read(&stream->ptr, 6);
 
 # if defined(OPT_STRICT)
@@ -185,8 +217,10 @@ int mad_layer_I(struct mad_stream *strea
       for (ch = 0; ch < nch; ++ch) {
 	nb = allocation[ch][sb];
 	frame->sbsample[ch][s][sb] = nb ?
-	  mad_f_mul(I_sample(&stream->ptr, nb),
+	  mad_f_mul(I_sample(&stream->ptr, nb, stream),
 		    sf_table[scalefactor[ch][sb]]) : 0;
+	if (stream->error != 0)
+	  return -1;
       }
     }
 
@@ -194,7 +228,14 @@ int mad_layer_I(struct mad_stream *strea
       if ((nb = allocation[0][sb])) {
 	mad_fixed_t sample;
 
-	sample = I_sample(&stream->ptr, nb);
+	if (mad_bit_length(&stream->ptr, &frameend_ptr) < nb) {
+	  stream->error = MAD_ERROR_LOSTSYNC;
+	  stream->sync = 0;
+          return -1;
+	}
+	sample = I_sample(&stream->ptr, nb, stream);
+        if (stream->error != 0)
+	  return -1;
 
 	for (ch = 0; ch < nch; ++ch) {
 	  frame->sbsample[ch][s][sb] =
@@ -280,13 +321,21 @@ struct quantclass {
 static
 void II_samples(struct mad_bitptr *ptr,
 		struct quantclass const *quantclass,
-		mad_fixed_t output[3])
+		mad_fixed_t output[3], struct mad_stream *stream)
 {
   unsigned int nb, s, sample[3];
+  struct mad_bitptr frameend_ptr;
+
+  mad_bit_init(&frameend_ptr, stream->next_frame);
 
   if ((nb = quantclass->group)) {
     unsigned int c, nlevels;
 
+    if (mad_bit_length(ptr, &frameend_ptr) < quantclass->bits) {
+      stream->error = MAD_ERROR_LOSTSYNC;
+      stream->sync = 0;
+      return;
+    }
     /* degrouping */
     c = mad_bit_read(ptr, quantclass->bits);
     nlevels = quantclass->nlevels;
@@ -299,8 +348,14 @@ void II_samples(struct mad_bitptr *ptr,
   else {
     nb = quantclass->bits;
 
-    for (s = 0; s < 3; ++s)
+    for (s = 0; s < 3; ++s) {
+      if (mad_bit_length(ptr, &frameend_ptr) < nb) {
+	stream->error = MAD_ERROR_LOSTSYNC;
+	stream->sync = 0;
+	return;
+      }
       sample[s] = mad_bit_read(ptr, nb);
+    }
   }
 
   for (s = 0; s < 3; ++s) {
@@ -336,6 +391,9 @@ int mad_layer_II(struct mad_stream *stre
   unsigned char const *offsets;
   unsigned char allocation[2][32], scfsi[2][32], scalefactor[2][32][3];
   mad_fixed_t samples[3];
+  struct mad_bitptr frameend_ptr;
+
+  mad_bit_init(&frameend_ptr, stream->next_frame);
 
   nch = MAD_NCHANNELS(header);
 
@@ -402,13 +460,24 @@ int mad_layer_II(struct mad_stream *stre
   for (sb = 0; sb < bound; ++sb) {
     nbal = bitalloc_table[offsets[sb]].nbal;
 
-    for (ch = 0; ch < nch; ++ch)
+    for (ch = 0; ch < nch; ++ch) {
+      if (mad_bit_length(&stream->ptr, &frameend_ptr) < nbal) {
+	stream->error = MAD_ERROR_LOSTSYNC;
+	stream->sync = 0;
+	return -1;
+      }
       allocation[ch][sb] = mad_bit_read(&stream->ptr, nbal);
+    }
   }
 
   for (sb = bound; sb < sblimit; ++sb) {
     nbal = bitalloc_table[offsets[sb]].nbal;
 
+    if (mad_bit_length(&stream->ptr, &frameend_ptr) < nbal) {
+      stream->error = MAD_ERROR_LOSTSYNC;
+      stream->sync = 0;
+      return -1;
+    }
     allocation[0][sb] =
     allocation[1][sb] = mad_bit_read(&stream->ptr, nbal);
   }
@@ -417,8 +486,14 @@ int mad_layer_II(struct mad_stream *stre
 
   for (sb = 0; sb < sblimit; ++sb) {
     for (ch = 0; ch < nch; ++ch) {
-      if (allocation[ch][sb])
+      if (allocation[ch][sb]) {
+	if (mad_bit_length(&stream->ptr, &frameend_ptr) < 2) {
+	  stream->error = MAD_ERROR_LOSTSYNC;
+	  stream->sync = 0;
+	  return -1;
+	}
 	scfsi[ch][sb] = mad_bit_read(&stream->ptr, 2);
+      }
     }
   }
 
@@ -441,6 +516,11 @@ int mad_layer_II(struct mad_stream *stre
   for (sb = 0; sb < sblimit; ++sb) {
     for (ch = 0; ch < nch; ++ch) {
       if (allocation[ch][sb]) {
+	if (mad_bit_length(&stream->ptr, &frameend_ptr) < 6) {
+	  stream->error = MAD_ERROR_LOSTSYNC;
+	  stream->sync = 0;
+	  return -1;
+	}
 	scalefactor[ch][sb][0] = mad_bit_read(&stream->ptr, 6);
 
 	switch (scfsi[ch][sb]) {
@@ -451,11 +531,21 @@ int mad_layer_II(struct mad_stream *stre
 	  break;
 
 	case 0:
+	  if (mad_bit_length(&stream->ptr, &frameend_ptr) < 6) {
+	    stream->error = MAD_ERROR_LOSTSYNC;
+	    stream->sync = 0;
+	    return -1;
+	  }
 	  scalefactor[ch][sb][1] = mad_bit_read(&stream->ptr, 6);
 	  /* fall through */
 
 	case 1:
 	case 3:
+	  if (mad_bit_length(&stream->ptr, &frameend_ptr) < 6) {
+	    stream->error = MAD_ERROR_LOSTSYNC;
+	    stream->sync = 0;
+	    return -1;
+	  }
 	  scalefactor[ch][sb][2] = mad_bit_read(&stream->ptr, 6);
 	}
 
@@ -487,7 +577,9 @@ int mad_layer_II(struct mad_stream *stre
 	if ((index = allocation[ch][sb])) {
 	  index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
 
-	  II_samples(&stream->ptr, &qc_table[index], samples);
+	  II_samples(&stream->ptr, &qc_table[index], samples, stream);
+	  if (stream->error != 0)
+            return -1;
 
 	  for (s = 0; s < 3; ++s) {
 	    frame->sbsample[ch][3 * gr + s][sb] =
@@ -505,7 +597,9 @@ int mad_layer_II(struct mad_stream *stre
       if ((index = allocation[0][sb])) {
 	index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
 
-	II_samples(&stream->ptr, &qc_table[index], samples);
+	II_samples(&stream->ptr, &qc_table[index], samples, stream);
+	if (stream->error != 0)
+          return -1;
 
 	for (ch = 0; ch < nch; ++ch) {
 	  for (s = 0; s < 3; ++s) {
Index: libmad-0.15.1b/layer3.c
===================================================================
--- libmad-0.15.1b.orig/layer3.c
+++ libmad-0.15.1b/layer3.c
@@ -598,7 +598,8 @@ enum mad_error III_sideinfo(struct mad_b
 static
 unsigned int III_scalefactors_lsf(struct mad_bitptr *ptr,
 				  struct channel *channel,
-				  struct channel *gr1ch, int mode_extension)
+				  struct channel *gr1ch, int mode_extension,
+				  unsigned int bits_left, unsigned int *part2_length)
 {
   struct mad_bitptr start;
   unsigned int scalefac_compress, index, slen[4], part, n, i;
@@ -644,8 +645,12 @@ unsigned int III_scalefactors_lsf(struct
 
     n = 0;
     for (part = 0; part < 4; ++part) {
-      for (i = 0; i < nsfb[part]; ++i)
+      for (i = 0; i < nsfb[part]; ++i) {
+	if (bits_left < slen[part])
+	  return MAD_ERROR_BADSCFSI;
 	channel->scalefac[n++] = mad_bit_read(ptr, slen[part]);
+	bits_left -= slen[part];
+      }
     }
 
     while (n < 39)
@@ -690,7 +695,10 @@ unsigned int III_scalefactors_lsf(struct
       max = (1 << slen[part]) - 1;
 
       for (i = 0; i < nsfb[part]; ++i) {
+	if (bits_left < slen[part])
+	  return MAD_ERROR_BADSCFSI;
 	is_pos = mad_bit_read(ptr, slen[part]);
+	bits_left -= slen[part];
 
 	channel->scalefac[n] = is_pos;
 	gr1ch->scalefac[n++] = (is_pos == max);
@@ -703,7 +711,8 @@ unsigned int III_scalefactors_lsf(struct
     }
   }
 
-  return mad_bit_length(&start, ptr);
+  *part2_length = mad_bit_length(&start, ptr);
+  return MAD_ERROR_NONE;
 }
 
 /*
@@ -712,7 +721,8 @@ unsigned int III_scalefactors_lsf(struct
  */
 static
 unsigned int III_scalefactors(struct mad_bitptr *ptr, struct channel *channel,
-			      struct channel const *gr0ch, unsigned int scfsi)
+			      struct channel const *gr0ch, unsigned int scfsi,
+			      unsigned int bits_left, unsigned int *part2_length)
 {
   struct mad_bitptr start;
   unsigned int slen1, slen2, sfbi;
@@ -728,12 +738,20 @@ unsigned int III_scalefactors(struct mad
     sfbi = 0;
 
     nsfb = (channel->flags & mixed_block_flag) ? 8 + 3 * 3 : 6 * 3;
-    while (nsfb--)
+    while (nsfb--) {
+      if (bits_left < slen1)
+	return MAD_ERROR_BADSCFSI;
       channel->scalefac[sfbi++] = mad_bit_read(ptr, slen1);
+      bits_left -= slen1;
+    }
 
     nsfb = 6 * 3;
-    while (nsfb--)
+    while (nsfb--) {
+      if (bits_left < slen2)
+	return MAD_ERROR_BADSCFSI;
       channel->scalefac[sfbi++] = mad_bit_read(ptr, slen2);
+      bits_left -= slen2;
+    }
 
     nsfb = 1 * 3;
     while (nsfb--)
@@ -745,8 +763,12 @@ unsigned int III_scalefactors(struct mad
 	channel->scalefac[sfbi] = gr0ch->scalefac[sfbi];
     }
     else {
-      for (sfbi = 0; sfbi < 6; ++sfbi)
+      for (sfbi = 0; sfbi < 6; ++sfbi) {
+	if (bits_left < slen1)
+	  return MAD_ERROR_BADSCFSI;
 	channel->scalefac[sfbi] = mad_bit_read(ptr, slen1);
+	bits_left -= slen1;
+      }
     }
 
     if (scfsi & 0x4) {
@@ -754,8 +776,12 @@ unsigned int III_scalefactors(struct mad
 	channel->scalefac[sfbi] = gr0ch->scalefac[sfbi];
     }
     else {
-      for (sfbi = 6; sfbi < 11; ++sfbi)
+      for (sfbi = 6; sfbi < 11; ++sfbi) {
+	if (bits_left < slen1)
+	  return MAD_ERROR_BADSCFSI;
 	channel->scalefac[sfbi] = mad_bit_read(ptr, slen1);
+	bits_left -= slen1;
+      }
     }
 
     if (scfsi & 0x2) {
@@ -763,8 +789,12 @@ unsigned int III_scalefactors(struct mad
 	channel->scalefac[sfbi] = gr0ch->scalefac[sfbi];
     }
     else {
-      for (sfbi = 11; sfbi < 16; ++sfbi)
+      for (sfbi = 11; sfbi < 16; ++sfbi) {
+	if (bits_left < slen2)
+	  return MAD_ERROR_BADSCFSI;
 	channel->scalefac[sfbi] = mad_bit_read(ptr, slen2);
+	bits_left -= slen2;
+      }
     }
 
     if (scfsi & 0x1) {
@@ -772,14 +802,19 @@ unsigned int III_scalefactors(struct mad
 	channel->scalefac[sfbi] = gr0ch->scalefac[sfbi];
     }
     else {
-      for (sfbi = 16; sfbi < 21; ++sfbi)
+      for (sfbi = 16; sfbi < 21; ++sfbi) {
+	if (bits_left < slen2)
+	  return MAD_ERROR_BADSCFSI;
 	channel->scalefac[sfbi] = mad_bit_read(ptr, slen2);
+	bits_left -= slen2;
+      }
     }
 
     channel->scalefac[21] = 0;
   }
 
-  return mad_bit_length(&start, ptr);
+  *part2_length = mad_bit_length(&start, ptr);
+  return MAD_ERROR_NONE;
 }
 
 /*
@@ -933,19 +968,17 @@ static
 enum mad_error III_huffdecode(struct mad_bitptr *ptr, mad_fixed_t xr[576],
 			      struct channel *channel,
 			      unsigned char const *sfbwidth,
-			      unsigned int part2_length)
+			      signed int part3_length)
 {
   signed int exponents[39], exp;
   signed int const *expptr;
   struct mad_bitptr peek;
-  signed int bits_left, cachesz;
+  signed int bits_left, cachesz, fakebits;
   register mad_fixed_t *xrptr;
   mad_fixed_t const *sfbound;
   register unsigned long bitcache;
 
-  bits_left = (signed) channel->part2_3_length - (signed) part2_length;
-  if (bits_left < 0)
-    return MAD_ERROR_BADPART3LEN;
+  bits_left = part3_length;
 
   III_exponents(channel, sfbwidth, exponents);
 
@@ -956,8 +989,12 @@ enum mad_error III_huffdecode(struct mad
   cachesz  = mad_bit_bitsleft(&peek);
   cachesz += ((32 - 1 - 24) + (24 - cachesz)) & ~7;
 
+  if (bits_left < cachesz) {
+    cachesz = bits_left;
+  }
   bitcache   = mad_bit_read(&peek, cachesz);
   bits_left -= cachesz;
+  fakebits = 0;
 
   xrptr = &xr[0];
 
@@ -986,7 +1023,7 @@ enum mad_error III_huffdecode(struct mad
 
     big_values = channel->big_values;
 
-    while (big_values-- && cachesz + bits_left > 0) {
+    while (big_values-- && cachesz + bits_left - fakebits > 0) {
       union huffpair const *pair;
       unsigned int clumpsz, value;
       register mad_fixed_t requantized;
@@ -1023,10 +1060,19 @@ enum mad_error III_huffdecode(struct mad
 	unsigned int bits;
 
 	bits       = ((32 - 1 - 21) + (21 - cachesz)) & ~7;
+	if (bits_left < bits) {
+	  bits = bits_left;
+	}
 	bitcache   = (bitcache << bits) | mad_bit_read(&peek, bits);
 	cachesz   += bits;
 	bits_left -= bits;
       }
+      if (cachesz < 21) {
+	unsigned int bits = 21 - cachesz;
+	bitcache <<= bits;
+	cachesz += bits;
+	fakebits += bits;
+      }
 
       /* hcod (0..19) */
 
@@ -1041,6 +1087,8 @@ enum mad_error III_huffdecode(struct mad
       }
 
       cachesz -= pair->value.hlen;
+      if (cachesz < fakebits)
+	return MAD_ERROR_BADHUFFDATA;
 
       if (linbits) {
 	/* x (0..14) */
@@ -1054,10 +1102,15 @@ enum mad_error III_huffdecode(struct mad
 
 	case 15:
 	  if (cachesz < linbits + 2) {
-	    bitcache   = (bitcache << 16) | mad_bit_read(&peek, 16);
-	    cachesz   += 16;
-	    bits_left -= 16;
+	    unsigned int bits = 16;
+	    if (bits_left < 16)
+	      bits = bits_left;
+	    bitcache   = (bitcache << bits) | mad_bit_read(&peek, bits);
+	    cachesz   += bits;
+	    bits_left -= bits;
 	  }
+	  if (cachesz - fakebits < linbits)
+	    return MAD_ERROR_BADHUFFDATA;
 
 	  value += MASK(bitcache, cachesz, linbits);
 	  cachesz -= linbits;
@@ -1074,6 +1127,8 @@ enum mad_error III_huffdecode(struct mad
 	  }
 
 	x_final:
+	  if (cachesz - fakebits < 1)
+	    return MAD_ERROR_BADHUFFDATA;
 	  xrptr[0] = MASK1BIT(bitcache, cachesz--) ?
 	    -requantized : requantized;
 	}
@@ -1089,10 +1144,15 @@ enum mad_error III_huffdecode(struct mad
 
 	case 15:
 	  if (cachesz < linbits + 1) {
-	    bitcache   = (bitcache << 16) | mad_bit_read(&peek, 16);
-	    cachesz   += 16;
-	    bits_left -= 16;
+	    unsigned int bits = 16;
+	    if (bits_left < 16)
+	      bits = bits_left;
+	    bitcache   = (bitcache << bits) | mad_bit_read(&peek, bits);
+	    cachesz   += bits;
+	    bits_left -= bits;
 	  }
+	  if (cachesz - fakebits < linbits)
+	    return MAD_ERROR_BADHUFFDATA;
 
 	  value += MASK(bitcache, cachesz, linbits);
 	  cachesz -= linbits;
@@ -1109,6 +1169,8 @@ enum mad_error III_huffdecode(struct mad
 	  }
 
 	y_final:
+	  if (cachesz - fakebits < 1)
+	    return MAD_ERROR_BADHUFFDATA;
 	  xrptr[1] = MASK1BIT(bitcache, cachesz--) ?
 	    -requantized : requantized;
 	}
@@ -1128,6 +1190,8 @@ enum mad_error III_huffdecode(struct mad
 	    requantized = reqcache[value] = III_requantize(value, exp);
 	  }
 
+	  if (cachesz - fakebits < 1)
+	    return MAD_ERROR_BADHUFFDATA;
 	  xrptr[0] = MASK1BIT(bitcache, cachesz--) ?
 	    -requantized : requantized;
 	}
@@ -1146,6 +1210,8 @@ enum mad_error III_huffdecode(struct mad
 	    requantized = reqcache[value] = III_requantize(value, exp);
 	  }
 
+	  if (cachesz - fakebits < 1)
+	    return MAD_ERROR_BADHUFFDATA;
 	  xrptr[1] = MASK1BIT(bitcache, cachesz--) ?
 	    -requantized : requantized;
 	}
@@ -1155,9 +1221,6 @@ enum mad_error III_huffdecode(struct mad
     }
   }
 
-  if (cachesz + bits_left < 0)
-    return MAD_ERROR_BADHUFFDATA;  /* big_values overrun */
-
   /* count1 */
   {
     union huffquad const *table;
@@ -1167,15 +1230,24 @@ enum mad_error III_huffdecode(struct mad
 
     requantized = III_requantize(1, exp);
 
-    while (cachesz + bits_left > 0 && xrptr <= &xr[572]) {
+    while (cachesz + bits_left - fakebits > 0 && xrptr <= &xr[572]) {
       union huffquad const *quad;
 
       /* hcod (1..6) */
 
       if (cachesz < 10) {
-	bitcache   = (bitcache << 16) | mad_bit_read(&peek, 16);
-	cachesz   += 16;
-	bits_left -= 16;
+	unsigned int bits = 16;
+	if (bits_left < 16)
+	  bits = bits_left;
+	bitcache   = (bitcache << bits) | mad_bit_read(&peek, bits);
+	cachesz   += bits;
+	bits_left -= bits;
+      }
+      if (cachesz < 10) {
+	unsigned int bits = 10 - cachesz;
+	bitcache <<= bits;
+	cachesz += bits;
+	fakebits += bits;
       }
 
       quad = &table[MASK(bitcache, cachesz, 4)];
@@ -1188,6 +1260,11 @@ enum mad_error III_huffdecode(struct mad
 		      MASK(bitcache, cachesz, quad->ptr.bits)];
       }
 
+      if (cachesz - fakebits < quad->value.hlen + quad->value.v
+        + quad->value.w + quad->value.x + quad->value.y)
+	/* We don't have enough bits to read one more entry, consider them
+	 * stuffing bits. */
+	break;
       cachesz -= quad->value.hlen;
 
       if (xrptr == sfbound) {
@@ -1236,22 +1313,8 @@ enum mad_error III_huffdecode(struct mad
 
       xrptr += 2;
     }
-
-    if (cachesz + bits_left < 0) {
-# if 0 && defined(DEBUG)
-      fprintf(stderr, "huffman count1 overrun (%d bits)\n",
-	      -(cachesz + bits_left));
-# endif
-
-      /* technically the bitstream is misformatted, but apparently
-	 some encoders are just a bit sloppy with stuffing bits */
-
-      xrptr -= 4;
-    }
   }
 
-  assert(-bits_left <= MAD_BUFFER_GUARD * CHAR_BIT);
-
 # if 0 && defined(DEBUG)
   if (bits_left < 0)
     fprintf(stderr, "read %d bits too many\n", -bits_left);
@@ -2348,10 +2411,11 @@ void III_freqinver(mad_fixed_t sample[18
  */
 static
 enum mad_error III_decode(struct mad_bitptr *ptr, struct mad_frame *frame,
-			  struct sideinfo *si, unsigned int nch)
+			  struct sideinfo *si, unsigned int nch, unsigned int md_len)
 {
   struct mad_header *header = &frame->header;
   unsigned int sfreqi, ngr, gr;
+  int bits_left = md_len * CHAR_BIT;
 
   {
     unsigned int sfreq;
@@ -2383,6 +2447,7 @@ enum mad_error III_decode(struct mad_bit
     for (ch = 0; ch < nch; ++ch) {
       struct channel *channel = &granule->ch[ch];
       unsigned int part2_length;
+      unsigned int part3_length;
 
       sfbwidth[ch] = sfbwidth_table[sfreqi].l;
       if (channel->block_type == 2) {
@@ -2391,18 +2456,30 @@ enum mad_error III_decode(struct mad_bit
       }
 
       if (header->flags & MAD_FLAG_LSF_EXT) {
-	part2_length = III_scalefactors_lsf(ptr, channel,
+	error = III_scalefactors_lsf(ptr, channel,
 					    ch == 0 ? 0 : &si->gr[1].ch[1],
-					    header->mode_extension);
+					    header->mode_extension, bits_left, &part2_length);
       }
       else {
-	part2_length = III_scalefactors(ptr, channel, &si->gr[0].ch[ch],
-					gr == 0 ? 0 : si->scfsi[ch]);
+	error = III_scalefactors(ptr, channel, &si->gr[0].ch[ch],
+					gr == 0 ? 0 : si->scfsi[ch], bits_left, &part2_length);
       }
+      if (error)
+        return error;
+
+      bits_left -= part2_length;
 
-      error = III_huffdecode(ptr, xr[ch], channel, sfbwidth[ch], part2_length);
+      if (part2_length > channel->part2_3_length)
+        return MAD_ERROR_BADPART3LEN;
+
+      part3_length = channel->part2_3_length - part2_length;
+      if (part3_length > bits_left)
+        return MAD_ERROR_BADPART3LEN;
+
+      error = III_huffdecode(ptr, xr[ch], channel, sfbwidth[ch], part3_length);
       if (error)
 	return error;
+      bits_left -= part3_length;
     }
 
     /* joint stereo processing */
@@ -2519,11 +2596,13 @@ int mad_layer_III(struct mad_stream *str
   unsigned int nch, priv_bitlen, next_md_begin = 0;
   unsigned int si_len, data_bitlen, md_len;
   unsigned int frame_space, frame_used, frame_free;
-  struct mad_bitptr ptr;
+  struct mad_bitptr ptr, bufend_ptr;
   struct sideinfo si;
   enum mad_error error;
   int result = 0;
 
+  mad_bit_init(&bufend_ptr, stream->bufend);
+
   /* allocate Layer III dynamic structures */
 
   if (stream->main_data == 0) {
@@ -2587,14 +2666,15 @@ int mad_layer_III(struct mad_stream *str
     unsigned long header;
 
     mad_bit_init(&peek, stream->next_frame);
+    if (mad_bit_length(&peek, &bufend_ptr) >= 57) {
+      header = mad_bit_read(&peek, 32);
+      if ((header & 0xffe60000L) /* syncword | layer */ == 0xffe20000L) {
+        if (!(header & 0x00010000L))  /* protection_bit */
+	  mad_bit_skip(&peek, 16);  /* crc_check */
 
-    header = mad_bit_read(&peek, 32);
-    if ((header & 0xffe60000L) /* syncword | layer */ == 0xffe20000L) {
-      if (!(header & 0x00010000L))  /* protection_bit */
-	mad_bit_skip(&peek, 16);  /* crc_check */
-
-      next_md_begin =
-	mad_bit_read(&peek, (header & 0x00080000L) /* ID */ ? 9 : 8);
+        next_md_begin =
+	  mad_bit_read(&peek, (header & 0x00080000L) /* ID */ ? 9 : 8);
+      }
     }
 
     mad_bit_finish(&peek);
@@ -2653,7 +2733,7 @@ int mad_layer_III(struct mad_stream *str
   /* decode main_data */
 
   if (result == 0) {
-    error = III_decode(&ptr, frame, &si, nch);
+    error = III_decode(&ptr, frame, &si, nch, md_len);
     if (error) {
       stream->error = error;
       result = -1;