Add a fuzzer for ReadHuffmanCodes

Change-Id: If8c30aaa87c34007ae455a03daa7b3c0f22fc8c3

tests/fuzzer/huffman_fuzzer.c

@@ -0,0 +1,65 @@
+// Copyright 2023 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+////////////////////////////////////////////////////////////////////////////////
+
+#include <stdint.h>
+#include <string.h>
+
+#include "src/dec/vp8li_dec.h"
+#include "src/utils/bit_reader_utils.h"
+#include "src/utils/huffman_utils.h"
+#include "src/utils/utils.h"
+#include "src/webp/format_constants.h"
+
+int LLVMFuzzerTestOneInput(const uint8_t* const data, size_t size) {
+  // Number of bits to initialize data.
+  static const int kColorCacheBitsBits = 4;
+  // 'num_htree_groups' is contained in the RG channel, hence 16 bits.
+  static const int kNumHtreeGroupsBits = 16;
+  if (size * sizeof(*data) < kColorCacheBitsBits + kNumHtreeGroupsBits) {
+    return 0;
+  }
+
+  // A non-NULL mapping brings minor changes that are tested by the normal
+  // fuzzer.
+  int* const mapping = NULL;
+  HuffmanTables huffman_tables;
+  memset(&huffman_tables, 0, sizeof(huffman_tables));
+  HTreeGroup* htree_groups = NULL;
+
+  VP8LDecoder* dec = VP8LNew();
+  if (dec == NULL) goto Error;
+  VP8LBitReader* const br = &dec->br_;
+  VP8LInitBitReader(br, data, size);
+
+  const int color_cache_bits = VP8LReadBits(br, kColorCacheBitsBits);
+  if (color_cache_bits < 1 || color_cache_bits > MAX_CACHE_BITS) goto Error;
+
+  const int num_htree_groups = VP8LReadBits(br, kNumHtreeGroupsBits);
+  // 'num_htree_groups' cannot be 0 as it is built from a non-empty image.
+  if (num_htree_groups == 0) goto Error;
+  // This variable is only useful when mapping is not NULL.
+  const int num_htree_groups_max = num_htree_groups;
+  ReadHuffmanCodesHelper(color_cache_bits, num_htree_groups,
+                         num_htree_groups_max, mapping, dec, &huffman_tables,
+                         &htree_groups);
+
+ Error:
+  WebPSafeFree(mapping);
+  VP8LHtreeGroupsFree(htree_groups);
+  VP8LHuffmanTablesDeallocate(&huffman_tables);
+  VP8LDelete(dec);
+  return 0;
+}

tests/fuzzer/makefile.unix

@@ -11,9 +11,9 @@ LDLIBS = ../../src/mux/libwebpmux.a ../../src/demux/libwebpdemux.a
 LDLIBS += ../../src/libwebp.a ../../imageio/libimageio_util.a
 LDLIBS += ../../sharpyuv/libsharpyuv.a
 
-FUZZERS = advanced_api_fuzzer animation_api_fuzzer animencoder_fuzzer
-FUZZERS += animdecoder_fuzzer mux_demux_api_fuzzer enc_dec_fuzzer
-FUZZERS += simple_api_fuzzer
+FUZZERS = advanced_api_fuzzer animation_api_fuzzer animdecoder_fuzzer
+FUZZERS += animencoder_fuzzer enc_dec_fuzzer huffman_fuzzer
+FUZZERS += mux_demux_api_fuzzer simple_api_fuzzer
 
 %.o: fuzz_utils.h img_alpha.h img_grid.h img_peak.h
 all: $(FUZZERS)