ddidderr/zstd-rs
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[legacy] Fix ZSTDv0*_decodeSequence()

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* Version <= 0.5 could read beyond the end of `dumps`, which points into
  the input buffer.
* Check the validity of `dumps` before using it, if it is out of bounds
  return garbage values. There is no return code for this function.
* Introduce `MEM_readLE24()` for simplicity, since I don't want to trust
  that there is an extra byte after `dumps`.
This commit is contained in:
Nick Terrell
2019-04-19 11:34:52 -07:00
parent 9ad7ea44ec
commit 0fd322f812
5 changed files with 50 additions and 43 deletions
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lib/legacy/zstd_v04.c
+11 -8
View File
@@ -189,6 +189,11 @@ MEM_STATIC void MEM_writeLE16(void* memPtr, U16 val)
}
}
MEM_STATIC U32 MEM_readLE24(const void* memPtr)
{
return MEM_readLE16(memPtr) + (((const BYTE*)memPtr)[2] << 16);
}
MEM_STATIC U32 MEM_readLE32(const void* memPtr)
{
if (MEM_isLittleEndian())
@@ -2808,13 +2813,12 @@ static void ZSTD_decodeSequence(seq_t* seq, seqState_t* seqState)
litLength = FSE_decodeSymbol(&(seqState->stateLL), &(seqState->DStream));
prevOffset = litLength ? seq->offset : seqState->prevOffset;
if (litLength == MaxLL) {
U32 add = *dumps++;
const U32 add = dumps<de ? *dumps++ : 0;
if (add < 255) litLength += add;
else {
litLength = dumps[0] + (dumps[1]<<8) + (dumps[2]<<16);
else if (dumps + 3 <= de) {
litLength = MEM_readLE24(dumps);
dumps += 3;
}
if (dumps > de) { litLength = MaxLL+255; } /* late correction, to avoid using uninitialized memory */
if (dumps >= de) { dumps = de-1; } /* late correction, to avoid read overflow (data is now corrupted anyway) */
}
@@ -2837,13 +2841,12 @@ static void ZSTD_decodeSequence(seq_t* seq, seqState_t* seqState)
/* MatchLength */
matchLength = FSE_decodeSymbol(&(seqState->stateML), &(seqState->DStream));
if (matchLength == MaxML) {
U32 add = *dumps++;
const U32 add = dumps<de ? *dumps++ : 0;
if (add < 255) matchLength += add;
else {
matchLength = dumps[0] + (dumps[1]<<8) + (dumps[2]<<16);
else if (dumps + 3 <= de){
matchLength = MEM_readLE24(dumps);
dumps += 3;
}
if (dumps > de) { matchLength = MaxML+255; } /* late correction, to avoid using uninitialized memory */
if (dumps >= de) { dumps = de-1; } /* late correction, to avoid read overflow (data is now corrupted anyway) */
}
matchLength += MINMATCH;