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-rw-r--r--testing/libfuzzer/pdf_lzw_fuzzer.cc58
1 files changed, 58 insertions, 0 deletions
diff --git a/testing/libfuzzer/pdf_lzw_fuzzer.cc b/testing/libfuzzer/pdf_lzw_fuzzer.cc
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index 0000000000..71c258969d
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+++ b/testing/libfuzzer/pdf_lzw_fuzzer.cc
@@ -0,0 +1,58 @@
+// Copyright 2017 The PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <vector>
+
+#include "core/fxcodec/gif/cfx_lzwdecompressor.h"
+#include "third_party/base/numerics/safe_conversions.h"
+
+// Between 2x and 5x is a standard range for LZW according to a quick
+// search of papers. Running up to 10x to catch any niche cases.
+constexpr uint32_t kMinCompressionRatio = 2;
+constexpr uint32_t kMaxCompressionRatio = 10;
+
+void LZWFuzz(const uint8_t* src_buf,
+ size_t src_size,
+ uint8_t color_exp,
+ uint8_t code_exp) {
+ std::unique_ptr<CFX_LZWDecompressor> decompressor =
+ CFX_LZWDecompressor::Create(color_exp, code_exp);
+ if (!decompressor)
+ return;
+
+ for (uint32_t compressions_ratio = kMinCompressionRatio;
+ compressions_ratio <= kMaxCompressionRatio; compressions_ratio++) {
+ std::vector<uint8_t> des_buf(compressions_ratio * src_size);
+ // This cast should be safe since the caller is checking for overflow on
+ // the initial data.
+ uint32_t des_size = static_cast<uint32_t>(des_buf.size());
+ if (CFX_GifDecodeStatus::InsufficientDestSize !=
+ decompressor->Decode(const_cast<uint8_t*>(src_buf), src_size,
+ des_buf.data(), &des_size))
+ return;
+ }
+}
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+ // Need at least 3 bytes to do anything.
+ if (size < 3)
+ return 0;
+
+ // Normally the GIF would provide the code and color sizes, instead, going
+ // to assume they are the first two bytes of data provided.
+ uint8_t color_exp = data[0];
+ uint8_t code_exp = data[1];
+ const uint8_t* lzw_data = data + 2;
+ uint32_t lzw_data_size = static_cast<uint32_t>(size - 2);
+ // Check that there isn't going to be an overflow in the destination buffer
+ // size.
+ if (lzw_data_size >
+ std::numeric_limits<uint32_t>::max() / kMaxCompressionRatio) {
+ return 0;
+ }
+
+ LZWFuzz(lzw_data, lzw_data_size, color_exp, code_exp);
+
+ return 0;
+}