1 // Copyright 2017 The PDFium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include <vector>
6
7 #include "core/fxcodec/gif/cfx_lzwdecompressor.h"
8 #include "third_party/base/numerics/safe_conversions.h"
9
10 // Between 2x and 5x is a standard range for LZW according to a quick
11 // search of papers. Running up to 10x to catch any niche cases.
12 constexpr uint32_t kMinCompressionRatio = 2;
13 constexpr uint32_t kMaxCompressionRatio = 10;
14
LZWFuzz(const uint8_t * src_buf,size_t src_size,uint8_t color_exp,uint8_t code_exp)15 void LZWFuzz(const uint8_t* src_buf,
16 size_t src_size,
17 uint8_t color_exp,
18 uint8_t code_exp) {
19 std::unique_ptr<CFX_LZWDecompressor> decompressor =
20 CFX_LZWDecompressor::Create(color_exp, code_exp);
21 if (!decompressor)
22 return;
23
24 for (uint32_t compressions_ratio = kMinCompressionRatio;
25 compressions_ratio <= kMaxCompressionRatio; compressions_ratio++) {
26 std::vector<uint8_t> dest_buf(compressions_ratio * src_size);
27 // This cast should be safe since the caller is checking for overflow on
28 // the initial data.
29 uint32_t dest_size = static_cast<uint32_t>(dest_buf.size());
30 if (CFX_GifDecodeStatus::InsufficientDestSize !=
31 decompressor->Decode(src_buf, src_size, dest_buf.data(), &dest_size)) {
32 return;
33 }
34 }
35 }
36
LLVMFuzzerTestOneInput(const uint8_t * data,size_t size)37 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
38 // Need at least 3 bytes to do anything.
39 if (size < 3)
40 return 0;
41
42 // Normally the GIF would provide the code and color sizes, instead, going
43 // to assume they are the first two bytes of data provided.
44 uint8_t color_exp = data[0];
45 uint8_t code_exp = data[1];
46 const uint8_t* lzw_data = data + 2;
47 uint32_t lzw_data_size = static_cast<uint32_t>(size - 2);
48 // Check that there isn't going to be an overflow in the destination buffer
49 // size.
50 if (lzw_data_size >
51 std::numeric_limits<uint32_t>::max() / kMaxCompressionRatio) {
52 return 0;
53 }
54
55 LZWFuzz(lzw_data, lzw_data_size, color_exp, code_exp);
56
57 return 0;
58 }
59