[fuzz] Add a streaming round trip fuzzer

diff --git a/ossfuzz/round_trip_stream_fuzzer.c b/ossfuzz/round_trip_stream_fuzzer.c
new file mode 100644 (file)
index 0000000..4facfc9
--- /dev/null
+++ b/ossfuzz/round_trip_stream_fuzzer.c
@@ -0,0 +1,217 @@
+/**
+ * This fuzz target performs a lz4 streaming round-trip test
+ * (compress & decompress), compares the result with the original, and calls
+ * abort() on corruption.
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "fuzz_helpers.h"
+#define LZ4_STATIC_LINKING_ONLY
+#include "lz4.h"
+
+typedef struct {
+  char const* buf;
+  size_t size;
+  size_t pos;
+} const_cursor_t;
+
+typedef struct {
+  char* buf;
+  size_t size;
+  size_t pos;
+} cursor_t;
+
+typedef struct {
+  LZ4_stream_t* cstream;
+  LZ4_streamDecode_t* dstream;
+  const_cursor_t data;
+  cursor_t compressed;
+  cursor_t roundTrip;
+  uint32_t seed;
+} state_t;
+
+cursor_t cursor_create(size_t size)
+{
+  cursor_t cursor;
+  cursor.buf = (char*)malloc(size);
+  cursor.size = size;
+  cursor.pos = 0;
+  FUZZ_ASSERT(cursor.buf);
+  return cursor;
+}
+
+void cursor_free(cursor_t cursor)
+{
+    free(cursor.buf);
+}
+
+state_t state_create(char const* data, size_t size, uint32_t seed)
+{
+    state_t state;
+
+    state.seed = seed;
+
+    state.data.buf = (char const*)data;
+    state.data.size = size;
+    state.data.pos = 0;
+
+    /* Extra margin because we are streaming. */
+    state.compressed = cursor_create(1024 + 2 * LZ4_compressBound(size));
+    state.roundTrip = cursor_create(size);
+
+    state.cstream = LZ4_createStream();
+    FUZZ_ASSERT(state.cstream);
+    state.dstream = LZ4_createStreamDecode();
+    FUZZ_ASSERT(state.dstream);
+
+    return state;
+}
+
+void state_free(state_t state)
+{
+    cursor_free(state.compressed);
+    cursor_free(state.roundTrip);
+    LZ4_freeStream(state.cstream);
+    LZ4_freeStreamDecode(state.dstream);
+}
+
+static void state_reset(state_t* state, uint32_t seed)
+{
+    LZ4_resetStream_fast(state->cstream);
+    LZ4_setStreamDecode(state->dstream, NULL, 0);
+    state->data.pos = 0;
+    state->compressed.pos = 0;
+    state->roundTrip.pos = 0;
+    state->seed = seed;
+}
+
+static void state_decompress(state_t* state, char const* src, int srcSize)
+{
+    char* dst = state->roundTrip.buf + state->roundTrip.pos;
+    int const dstCapacity = state->roundTrip.size - state->roundTrip.pos;
+    int const dSize = LZ4_decompress_safe_continue(state->dstream, src, dst,
+                                                   srcSize, dstCapacity);
+    FUZZ_ASSERT(dSize >= 0);
+    state->roundTrip.pos += dSize;
+}
+
+static void state_checkRoundTrip(state_t const* state)
+{
+    char const* data = state->data.buf;
+    size_t const size = state->data.size;
+    FUZZ_ASSERT_MSG(size == state->roundTrip.pos, "Incorrect size!");
+    FUZZ_ASSERT_MSG(!memcmp(data, state->roundTrip.buf, size), "Corruption!");
+}
+
+/**
+ * Picks a dictionary size and trims the dictionary off of the data.
+ */
+static size_t state_trimDict(state_t* state)
+{
+    /* 64 KB is the max dict size, allow slightly beyond that to test trim. */
+    uint32_t maxDictSize = MIN(70 * 1024, state->data.size);
+    size_t const dictSize = FUZZ_rand32(&state->seed, 0, maxDictSize);
+    FUZZ_ASSERT(state->compressed.pos == 0);
+    state->compressed.pos += dictSize;
+    return dictSize;
+}
+
+static void state_prefixRoundTrip(state_t* state)
+{
+    while (state->data.pos != state->data.size) {
+        char const* src = state->data.buf + state->data.pos;
+        char* dst = state->compressed.buf + state->compressed.pos;
+        int const srcRemaining = state->data.size - state->data.pos;
+        int const srcSize = FUZZ_rand32(&state->seed, 0, srcRemaining);
+        int const dstCapacity = state->compressed.size - state->compressed.pos;
+        int const cSize = LZ4_compress_fast_continue(state->cstream, src, dst,
+                                                     srcSize, dstCapacity, 0);
+        FUZZ_ASSERT(cSize > 0);
+        state->data.pos += srcSize;
+        state->compressed.pos += cSize;
+        state_decompress(state, dst, cSize);
+    }
+}
+
+static void state_extDictRoundTrip(state_t* state)
+{
+    int i = 0;
+    cursor_t data2 = cursor_create(state->data.size);
+    memcpy(data2.buf, state->data.buf, state->data.size);
+    while (state->data.pos != state->data.size) {
+        char const* data = (i++ & 1) ? state->data.buf : data2.buf;
+        char const* src = data + state->data.pos;
+        char* dst = state->compressed.buf + state->compressed.pos;
+        int const srcRemaining = state->data.size - state->data.pos;
+        int const srcSize = FUZZ_rand32(&state->seed, 0, srcRemaining);
+        int const dstCapacity = state->compressed.size - state->compressed.pos;
+        int const cSize = LZ4_compress_fast_continue(state->cstream, src, dst,
+                                                     srcSize, dstCapacity, 0);
+        FUZZ_ASSERT(cSize > 0);
+        state->data.pos += srcSize;
+        state->compressed.pos += cSize;
+        state_decompress(state, dst, cSize);
+    }
+    cursor_free(data2);
+}
+
+static void state_randomRoundTrip(state_t* state)
+{
+    if (FUZZ_rand32(&state->seed, 0, 1)) {
+      state_prefixRoundTrip(state);
+    } else {
+      state_extDictRoundTrip(state);
+    }
+}
+
+static void state_loadDictRoundTrip(state_t* state)
+{
+    char const* dict = state->compressed.buf;
+    size_t const dictSize = state_trimDict(state);
+    LZ4_loadDict(state->cstream, dict, dictSize);
+    LZ4_setStreamDecode(state->dstream, dict, dictSize);
+    state_randomRoundTrip(state);
+}
+
+static void state_attachDictRoundTrip(state_t* state)
+{
+    char const* dict = state->compressed.buf;
+    size_t const dictSize = state_trimDict(state);
+    LZ4_stream_t* dictStream = LZ4_createStream();
+    LZ4_loadDict(dictStream, dict, dictSize);
+    LZ4_attach_dictionary(state->cstream, dictStream);
+    LZ4_setStreamDecode(state->dstream, dict, dictSize);
+    state_randomRoundTrip(state);
+    LZ4_freeStream(dictStream);
+}
+
+typedef void (*round_trip_t)(state_t* state);
+
+round_trip_t roundTrips[] = {
+  &state_prefixRoundTrip,
+  &state_extDictRoundTrip,
+  &state_loadDictRoundTrip,
+  &state_attachDictRoundTrip,
+};
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
+{
+    uint32_t seed = FUZZ_seed(&data, &size);
+    state_t state = state_create((char const*)data, size, seed);
+    const int n = sizeof(roundTrips) / sizeof(round_trip_t);
+    int i;
+
+    for (i = 0; i < n; ++i) {
+        roundTrips[i](&state);
+        state_checkRoundTrip(&state);
+        state_reset(&state, seed);
+    }
+
+    state_free(state);
+
+    return 0;
+}