1 // Copyright 2017 The PDFium Authors
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 <stddef.h>
6 #include <stdint.h>
7
8 #include <vector>
9
10 #include "core/fxcodec/gif/lzw_decompressor.h"
11 #include "third_party/base/numerics/safe_conversions.h"
12
13 // Between 2x and 5x is a standard range for LZW according to a quick
14 // search of papers. Running up to 10x to catch any niche cases.
15 constexpr uint32_t kMinCompressionRatio = 2;
16 constexpr uint32_t kMaxCompressionRatio = 10;
17
18 static constexpr size_t kMaxFuzzBytes = 1024 * 1024 * 1024; // 1 GB.
19
LZWFuzz(const uint8_t * src_buf,uint32_t src_size,uint8_t color_exp,uint8_t code_exp)20 void LZWFuzz(const uint8_t* src_buf,
21 uint32_t src_size,
22 uint8_t color_exp,
23 uint8_t code_exp) {
24 std::unique_ptr<LZWDecompressor> decompressor =
25 LZWDecompressor::Create(color_exp, code_exp);
26 if (!decompressor)
27 return;
28
29 for (uint32_t compressions_ratio = kMinCompressionRatio;
30 compressions_ratio <= kMaxCompressionRatio; compressions_ratio++) {
31 std::vector<uint8_t> dest_buf(compressions_ratio * src_size);
32 // This cast should be safe since the caller is checking for overflow on
33 // the initial data.
34 uint32_t dest_size = static_cast<uint32_t>(dest_buf.size());
35 decompressor->SetSource(src_buf, src_size);
36 if (LZWDecompressor::Status::kInsufficientDestSize !=
37 decompressor->Decode(dest_buf.data(), &dest_size)) {
38 return;
39 }
40 }
41 }
42
LLVMFuzzerTestOneInput(const uint8_t * data,size_t size)43 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
44 // Need at least 3 bytes to do anything.
45 if (size < 3 || size > kMaxFuzzBytes)
46 return 0;
47
48 // Normally the GIF would provide the code and color sizes, instead, going
49 // to assume they are the first two bytes of data provided.
50 uint8_t color_exp = data[0];
51 uint8_t code_exp = data[1];
52 const uint8_t* lzw_data = data + 2;
53 uint32_t lzw_data_size = static_cast<uint32_t>(size - 2);
54 // Check that there isn't going to be an overflow in the destination buffer
55 // size.
56 if (lzw_data_size >
57 std::numeric_limits<uint32_t>::max() / kMaxCompressionRatio) {
58 return 0;
59 }
60
61 LZWFuzz(lzw_data, lzw_data_size, color_exp, code_exp);
62
63 return 0;
64 }
65