Reject a too large block in ZSTD_compressSequencesAndLiterals()

lib/compress/zstd_compress.c

@@ -8051,6 +8051,7 @@ ZSTD_compressSequencesAndLiterals_internal(ZSTD_CCtx* cctx,
         FORWARD_IF_ERROR(block.nbSequences, "Error while trying to determine nb of sequences for a block");
         assert(block.nbSequences <= nbSequences);
         RETURN_ERROR_IF(block.litSize > litSize, externalSequences_invalid, "discrepancy: Sequences require more literals than present in buffer");
+        RETURN_ERROR_IF(block.blockSize > cctx->blockSizeMax, externalSequences_invalid, "sequences incorrectly define a too large block");
         ZSTD_resetSeqStore(&cctx->seqStore);
 
         conversionStatus = ZSTD_convertBlockSequences(cctx,

lib/zstd.h

@@ -1701,6 +1701,8 @@ ZSTD_compressSequences(ZSTD_CCtx* cctx,
  * - @litBufCapacity is the size of the underlying buffer into which literals are written, starting at address @literals.
  *   @litBufCapacity must be at least 8 bytes larger than @litSize.
  * - @decompressedSize must be correct, and correspond to the sum of all Sequences. Any discrepancy will generate an error.
+ * - Each block must regenerate at most ZSTD_BLOCKSIZE_MAX bytes, or less with a smaller window or ZSTD_c_maxBlockSize.
+ *   A larger block will generate an error.
  * @return : final compressed size, or a ZSTD error code.
  */
 ZSTDLIB_STATIC_API size_t

tests/fuzzer.c

@@ -4832,6 +4832,18 @@ static int basicUnitTests(U32 const seed, double compressibility)
     }
     DISPLAYLEVEL(3, "OK \n");
 
+    DISPLAYLEVEL(3, "test%3i : ZSTD_compressSequencesAndLiterals : reject a too large block : ", testNb++);
+    {   /* one block of ZSTD_BLOCKSIZE_MAX + 1 bytes : 16 literals and a match, then the block delimiter */
+        ZSTD_Sequence const seqs[2] = { { 1, 16, ZSTD_BLOCKSIZE_MAX + 1 - 16, 0 }, { 0, 0, 0, 0 } };
+        ZSTD_CCtx* const cctx = ZSTD_createCCtx();
+        CHECK(cctx != NULL);
+        CHECK_Z( ZSTD_CCtx_setParameter(cctx, ZSTD_c_blockDelimiters, ZSTD_sf_explicitBlockDelimiters) );
+        CHECK( ZSTD_isError(ZSTD_compressSequencesAndLiterals(cctx, compressedBuffer, compressedBufferSize,
+                                seqs, 2, CNBuffer, 16, CNBuffSize, ZSTD_BLOCKSIZE_MAX + 1)) );
+        ZSTD_freeCCtx(cctx);
+    }
+    DISPLAYLEVEL(3, "OK \n");
+
     /* Multiple blocks of zeros test */
     #define LONGZEROSLENGTH 1000000 /* 1MB of zeros */
     DISPLAYLEVEL(3, "test%3i : compress %u zeroes : ", testNb++, LONGZEROSLENGTH);