Add libFuzzer harnesses, a cmake option to build them

snappy-uncompress-fuzzer.cc

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+// Copyright 2019 Google Inc. All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// libFuzzer harness for fuzzing snappy decompression routine.
+
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <string>
+
+#include "snappy.h"
+
+namespace snappy {
+
+// Supplies random data sourced from libFuzzer to the snappy uncompressor,
+// decompressing its output and running some checks in the process.
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
+{
+  string input(reinterpret_cast<const char*>(data), size);
+
+  size_t uncompressed_len = 0;
+  bool getcomp_len_success = snappy::GetUncompressedLength(
+      input.data(),
+      input.size(),
+      &uncompressed_len);
+  // Check that GetUncompressedLength() does not return a very large
+  // value (1 MB) on success.
+  assert(!getcomp_len_success || uncompressed_len < (1 << 20));
+
+  // Uncompress
+  string uncompressed_out;
+  bool uncompress_success = snappy::Uncompress(
+      input.data(),
+      input.size(),
+      &uncompressed_out);
+
+  assert(uncompress_success);
+  return 0;
+}
+
+} // namespace snappy