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Fix & refactor Huffman repeat tables for dictionaries

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The Huffman repeat mode checker assumed that the CTable was zeroed in the region `[maxSymbolValue + 1, 256)`.
This assumption didn't hold for tables built in the dictionaries, because it didn't go through the same codepath.

Since this code was originally written, we added a header to the CTable that specifies the `tableLog`.
Add `maxSymbolValue` to that header, and check that the table's `maxSymbolValue` is at least the block's `maxSymbolValue`.

This solution is cleaner because we write this header for every CTable we build, so it can't be missed in any code path.

Credit to OSS-Fuzz
This commit is contained in:
Nick Terrell 2023-08-24 14:41:21 -07:00 committed by Nick Terrell
parent c27fa39904
commit 396ef5b434
2 changed files with 58 additions and 18 deletions
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15
lib/common/huf.h
View File

@ -197,9 +197,22 @@ size_t HUF_readCTable (HUF_CElt* CTable, unsigned* maxSymbolValuePtr, const void
/** HUF_getNbBitsFromCTable() :
* Read nbBits from CTable symbolTable, for symbol `symbolValue` presumed <= HUF_SYMBOLVALUE_MAX
* Note 1 : is not inlined, as HUF_CElt definition is private */
* Note 1 : If symbolValue > HUF_readCTableHeader(symbolTable).maxSymbolValue, returns 0
* Note 2 : is not inlined, as HUF_CElt definition is private
*/
U32 HUF_getNbBitsFromCTable(const HUF_CElt* symbolTable, U32 symbolValue);
typedef struct {
BYTE tableLog;
BYTE maxSymbolValue;
BYTE unused[sizeof(size_t) - 2];
} HUF_CTableHeader;
/** HUF_readCTableHeader() :
* @returns The header from the CTable specifying the tableLog and the maxSymbolValue.
*/
HUF_CTableHeader HUF_readCTableHeader(HUF_CElt const* ctable);
/*
* HUF_decompress() does the following:
* 1. select the decompression algorithm (X1, X2) based on pre-computed heuristics

61
lib/compress/huf_compress.c
View File

@ -220,6 +220,25 @@ static void HUF_setValue(HUF_CElt* elt, size_t value)
}
}
HUF_CTableHeader HUF_readCTableHeader(HUF_CElt const* ctable)
{
HUF_CTableHeader header;
ZSTD_memcpy(&header, ctable, sizeof(header));
return header;
}
static void HUF_writeCTableHeader(HUF_CElt* ctable, U32 tableLog, U32 maxSymbolValue)
{
HUF_CTableHeader header;
HUF_STATIC_ASSERT(sizeof(ctable[0]) == sizeof(header));
ZSTD_memset(&header, 0, sizeof(header));
assert(tableLog < 256);
header.tableLog = (BYTE)tableLog;
assert(maxSymbolValue < 256);
header.maxSymbolValue = (BYTE)maxSymbolValue;
ZSTD_memcpy(ctable, &header, sizeof(header));
}
typedef struct {
HUF_CompressWeightsWksp wksp;
BYTE bitsToWeight[HUF_TABLELOG_MAX + 1]; /* precomputed conversion table */
@ -237,6 +256,9 @@ size_t HUF_writeCTable_wksp(void* dst, size_t maxDstSize,
HUF_STATIC_ASSERT(HUF_CTABLE_WORKSPACE_SIZE >= sizeof(HUF_WriteCTableWksp));
assert(HUF_readCTableHeader(CTable).maxSymbolValue == maxSymbolValue);
assert(HUF_readCTableHeader(CTable).tableLog == huffLog);
/* check conditions */
if (workspaceSize < sizeof(HUF_WriteCTableWksp)) return ERROR(GENERIC);
if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(maxSymbolValue_tooLarge);
@ -283,7 +305,9 @@ size_t HUF_readCTable (HUF_CElt* CTable, unsigned* maxSymbolValuePtr, const void
if (tableLog > HUF_TABLELOG_MAX) return ERROR(tableLog_tooLarge);
if (nbSymbols > *maxSymbolValuePtr+1) return ERROR(maxSymbolValue_tooSmall);
CTable[0] = tableLog;
*maxSymbolValuePtr = nbSymbols - 1;
HUF_writeCTableHeader(CTable, tableLog, *maxSymbolValuePtr);
/* Prepare base value per rank */
{ U32 n, nextRankStart = 0;
@ -315,7 +339,6 @@ size_t HUF_readCTable (HUF_CElt* CTable, unsigned* maxSymbolValuePtr, const void
{ U32 n; for (n=0; n<nbSymbols; n++) HUF_setValue(ct + n, valPerRank[HUF_getNbBits(ct[n])]++); }
}
*maxSymbolValuePtr = nbSymbols - 1;
return readSize;
}
@ -323,6 +346,8 @@ U32 HUF_getNbBitsFromCTable(HUF_CElt const* CTable, U32 symbolValue)
{
const HUF_CElt* const ct = CTable + 1;
assert(symbolValue <= HUF_SYMBOLVALUE_MAX);
if (symbolValue > HUF_readCTableHeader(CTable).maxSymbolValue)
return 0;
return (U32)HUF_getNbBits(ct[symbolValue]);
}
@ -723,7 +748,8 @@ static void HUF_buildCTableFromTree(HUF_CElt* CTable, nodeElt const* huffNode, i
HUF_setNbBits(ct + huffNode[n].byte, huffNode[n].nbBits); /* push nbBits per symbol, symbol order */
for (n=0; n<alphabetSize; n++)
HUF_setValue(ct + n, valPerRank[HUF_getNbBits(ct[n])]++); /* assign value within rank, symbol order */
CTable[0] = maxNbBits;
HUF_writeCTableHeader(CTable, maxNbBits, maxSymbolValue);
}
size_t
@ -776,13 +802,20 @@ size_t HUF_estimateCompressedSize(const HUF_CElt* CTable, const unsigned* count,
}
int HUF_validateCTable(const HUF_CElt* CTable, const unsigned* count, unsigned maxSymbolValue) {
HUF_CElt const* ct = CTable + 1;
int bad = 0;
int s;
for (s = 0; s <= (int)maxSymbolValue; ++s) {
bad |= (count[s] != 0) & (HUF_getNbBits(ct[s]) == 0);
}
return !bad;
HUF_CTableHeader header = HUF_readCTableHeader(CTable);
HUF_CElt const* ct = CTable + 1;
int bad = 0;
int s;
assert(header.tableLog <= HUF_TABLELOG_ABSOLUTEMAX);
if (header.maxSymbolValue < maxSymbolValue)
return 0;
for (s = 0; s <= (int)maxSymbolValue; ++s) {
bad |= (count[s] != 0) & (HUF_getNbBits(ct[s]) == 0);
}
return !bad;
}
size_t HUF_compressBound(size_t size) { return HUF_COMPRESSBOUND(size); }
@ -1024,7 +1057,7 @@ HUF_compress1X_usingCTable_internal_body(void* dst, size_t dstSize,
const void* src, size_t srcSize,
const HUF_CElt* CTable)
{
U32 const tableLog = (U32)CTable[0];
U32 const tableLog = HUF_readCTableHeader(CTable).tableLog;
HUF_CElt const* ct = CTable + 1;
const BYTE* ip = (const BYTE*) src;
BYTE* const ostart = (BYTE*)dst;
@ -1372,12 +1405,6 @@ HUF_compress_internal (void* dst, size_t dstSize,
huffLog = (U32)maxBits;
DEBUGLOG(6, "bit distribution completed (%zu symbols)", showCTableBits(table->CTable + 1, maxSymbolValue+1));
}
/* Zero unused symbols in CTable, so we can check it for validity */
{
size_t const ctableSize = HUF_CTABLE_SIZE_ST(maxSymbolValue);
size_t const unusedSize = sizeof(table->CTable) - ctableSize * sizeof(HUF_CElt);
ZSTD_memset(table->CTable + ctableSize, 0, unusedSize);
}
/* Write table description header */
{ CHECK_V_F(hSize, HUF_writeCTable_wksp(op, dstSize, table->CTable, maxSymbolValue, huffLog,