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harden seek table parsing against overflow and oversized frame metadata #4638

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harden seek table parsing against overflow and oversized frame metadata #4638

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27 changes: 23 additions & 4 deletions contrib/seekable_format/zstdseek_decompress.c
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Original file line number Diff line number Diff line change
Expand Up @@ -264,6 +264,10 @@ ZSTD_seekTable* ZSTD_seekTable_create_fromSeekable(const ZSTD_seekable* zs)
st->tableLen = zs->seekTable.tableLen;

/* Allocate an extra entry at the end to match logic of initial allocation */
if (zs->seekTable.tableLen > (((size_t)-1) / sizeof(seekEntry_t)) - 1) {
free(st);
return NULL;
}
size_t const entriesSize = sizeof(seekEntry_t) * (zs->seekTable.tableLen + 1);
seekEntry_t* const entries = (seekEntry_t*)malloc(entriesSize);
if (entries==NULL) {
Expand Down Expand Up @@ -392,9 +396,21 @@ static size_t ZSTD_seekable_loadSeekTable(ZSTD_seekable* zs)
} }

{ U32 const numFrames = MEM_readLE32(zs->inBuff);
U32 const sizePerEntry = 8 + (checksumFlag?4:0);
U32 const tableSize = sizePerEntry * numFrames;
U32 const frameSize = tableSize + ZSTD_seekTableFooterSize + ZSTD_SKIPPABLEHEADERSIZE;
U32 const sizePerEntry = 8 + (checksumFlag ? 4 : 0);
U32 tableSize;
U32 frameSize;

if (numFrames > ZSTD_SEEKABLE_MAXFRAMES) {
return ERROR(frameIndex_tooLarge);
}
if (numFrames > UINT_MAX / sizePerEntry) {
return ERROR(corruption_detected);
}
tableSize = sizePerEntry * numFrames;
if (tableSize > UINT_MAX - ZSTD_seekTableFooterSize - ZSTD_SKIPPABLEHEADERSIZE) {
return ERROR(corruption_detected);
}
frameSize = tableSize + ZSTD_seekTableFooterSize + ZSTD_SKIPPABLEHEADERSIZE;

U32 remaining = frameSize - ZSTD_seekTableFooterSize; /* don't need to re-read footer */
{ U32 const toRead = MIN(remaining, SEEKABLE_BUFF_SIZE);
Expand All @@ -412,7 +428,10 @@ static size_t ZSTD_seekable_loadSeekTable(ZSTD_seekable* zs)

{ /* Allocate an extra entry at the end so that we can do size
* computations on the last element without special case */
seekEntry_t* const entries = (seekEntry_t*)malloc(sizeof(seekEntry_t) * (numFrames + 1));
if ((size_t)numFrames > (((size_t)-1) / sizeof(seekEntry_t)) - 1) {
return ERROR(memory_allocation);
}
seekEntry_t* const entries = (seekEntry_t*)malloc(sizeof(seekEntry_t) * ((size_t)numFrames + 1));

U32 idx = 0;
U32 pos = 8;
Expand Down