Update fuzzer sources

tests/fuzz/fuzz.h

@@ -12,15 +12,17 @@
  * Fuzz targets have some common parameters passed as macros during compilation.
  * Check the documentation for each individual fuzzer for more parameters.
  *
- * @param STATEFULL_FUZZING:
+ * @param STATEFUL_FUZZING:
  *        Define this to reuse state between fuzzer runs. This can be useful to
  *        test code paths which are only executed when contexts are reused.
  *        WARNING: Makes reproducing crashes much harder.
  *        Default: Not defined.
  * @param FUZZ_RNG_SEED_SIZE:
  *        The number of bytes of the source to look at when constructing a seed
- *        for the deterministic RNG.
- *        Default: 128.
+ *        for the deterministic RNG. These bytes are discarded before passing
+ *        the data to zstd functions. Every fuzzer initializes the RNG exactly
+ *        once before doing anything else, even if it is unused.
+ *        Default: 4.
  * @param ZSTD_DEBUG:
  *        This is a parameter for the zstd library. Defining `ZSTD_DEBUG=1`
  *        enables assert() statements in the zstd library. Higher levels enable
@@ -41,12 +43,20 @@
 #define FUZZ_H
 
 #ifndef FUZZ_RNG_SEED_SIZE
-#  define FUZZ_RNG_SEED_SIZE 128
+#  define FUZZ_RNG_SEED_SIZE 4
 #endif
 
 #include <stddef.h>
 #include <stdint.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif

tests/fuzz/fuzz_helpers.h

@@ -19,6 +19,10 @@
 #include <stdint.h>
 #include <stdio.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define MIN(a, b) ((a) < (b) ? (a) : (b))
 #define MAX(a, b) ((a) > (b) ? (a) : (b))
 
@@ -48,11 +52,13 @@
 
 /**
  * Determininistically constructs a seed based on the fuzz input.
- * Only looks at the first FUZZ_RNG_SEED_SIZE bytes of the input.
+ * Consumes up to the first FUZZ_RNG_SEED_SIZE bytes of the input.
  */
-FUZZ_STATIC uint32_t FUZZ_seed(const uint8_t *src, size_t size) {
-  size_t const toHash = MIN(FUZZ_RNG_SEED_SIZE, size);
-  return XXH32(src, toHash, 0);
+FUZZ_STATIC uint32_t FUZZ_seed(uint8_t const **src, size_t* size) {
+  size_t const toHash = MIN(FUZZ_RNG_SEED_SIZE, *size);
+  return XXH32(*src, toHash, 0);
+  *size -= toHash;
+  *src += toHash;
 }
 
 #define FUZZ_rotl32(x, r) (((x) << (r)) | ((x) >> (32 - (r))))
@@ -67,4 +73,8 @@ FUZZ_STATIC uint32_t FUZZ_rand(uint32_t *state) {
   return rand32 >> 5;
 }
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif

tests/fuzz/simple_decompress.c

@@ -24,7 +24,10 @@ static size_t bufSize = 0;
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
-    size_t const neededBufSize = MAX(20 * size, (size_t)256 << 10);
+    size_t neededBufSize;
+
+    FUZZ_seed(&src, &size);
+    neededBufSize = MAX(20 * size, (size_t)256 << 10);
 
     /* Allocate all buffers and contexts if not already allocated */
     if (neededBufSize > bufSize) {
@@ -39,7 +42,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
     }
     ZSTD_decompressDCtx(dctx, rBuf, neededBufSize, src, size);
 
-#ifndef STATEFULL_FUZZING
+#ifndef STATEFUL_FUZZING
     ZSTD_freeDCtx(dctx); dctx = NULL;
 #endif
     return 0;

tests/fuzz/simple_round_trip.c

@@ -44,9 +44,10 @@ static size_t roundTripTest(void *result, size_t resultCapacity,
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
-    size_t const neededBufSize = ZSTD_compressBound(size);
+    size_t neededBufSize;
 
-    seed = FUZZ_seed(src, size);
+    seed = FUZZ_seed(&src, &size);
+    neededBufSize = ZSTD_compressBound(size);
 
     /* Allocate all buffers and contexts if not already allocated */
     if (neededBufSize > bufSize) {
@@ -73,7 +74,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
         FUZZ_ASSERT_MSG(result == size, "Incorrect regenerated size");
         FUZZ_ASSERT_MSG(!memcmp(src, rBuf, size), "Corruption!");
     }
-#ifndef STATEFULL_FUZZING
+#ifndef STATEFUL_FUZZING
     ZSTD_freeCCtx(cctx); cctx = NULL;
     ZSTD_freeDCtx(dctx); dctx = NULL;
 #endif

tests/fuzz/stream_decompress.c

@@ -51,7 +51,7 @@ static ZSTD_inBuffer makeInBuffer(const uint8_t **src, size_t *size)
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
-    seed = FUZZ_seed(src, size);
+    seed = FUZZ_seed(&src, &size);
 
     /* Allocate all buffers and contexts if not already allocated */
     if (!buf) {
@@ -78,7 +78,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
     }
 
 error:
-#ifndef STATEFULL_FUZZING
+#ifndef STATEFUL_FUZZING
     ZSTD_freeDStream(dstream); dstream = NULL;
 #endif
     return 0;

tests/fuzz/stream_round_trip.c

@@ -114,9 +114,10 @@ static size_t compress(uint8_t *dst, size_t capacity,
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
-    size_t const neededBufSize = ZSTD_compressBound(size) * 2;
+    size_t neededBufSize;
 
-    seed = FUZZ_seed(src, size);
+    seed = FUZZ_seed(&src, &size);
+    neededBufSize = ZSTD_compressBound(size) * 2;
 
     /* Allocate all buffers and contexts if not already allocated */
     if (neededBufSize > bufSize) {
@@ -145,7 +146,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
         FUZZ_ASSERT_MSG(!memcmp(src, rBuf, size), "Corruption!");
     }
 
-#ifndef STATEFULL_FUZZING
+#ifndef STATEFUL_FUZZING
     ZSTD_freeCStream(cstream); cstream = NULL;
     ZSTD_freeDCtx(dctx); dctx = NULL;
 #endif