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- // Copyright 2016 The Chromium 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 "net/base/mime_sniffer.h"
- #include <stddef.h>
- #include <string>
- #include <fuzzer/FuzzedDataProvider.h>
- #include "url/gurl.h"
- // Fuzzer for the two main mime sniffing functions:
- // SniffMimeType and SniffMimeTypeFromLocalData.
- extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
- // net::SniffMimeType DCHECKs if passed an input buffer that's too large,
- // since it's meant to be used only on the first chunk of a file that's being
- // fed into a stream. Set a max size of the input to avoid running into that
- // DCHECK. Use 64k because that's twice the size of a typical read attempt.
- constexpr size_t kMaxSniffLength = 64 * 1024;
- static_assert(kMaxSniffLength >= net::kMaxBytesToSniff,
- "kMaxSniffLength is too small.");
- FuzzedDataProvider data_provider(data, size);
- // Divide up the input. It's important not to pass |url_string| to the GURL
- // constructor until after the length check, to prevent the fuzzer from
- // exploring GURL space with invalid inputs.
- //
- // Max lengths of URL and type hint are arbitrary.
- std::string url_string = data_provider.ConsumeRandomLengthString(4 * 1024);
- std::string mime_type_hint = data_provider.ConsumeRandomLengthString(1024);
- net::ForceSniffFileUrlsForHtml force_sniff_file_urls_for_html =
- data_provider.ConsumeBool() ? net::ForceSniffFileUrlsForHtml::kDisabled
- : net::ForceSniffFileUrlsForHtml::kEnabled;
- // Do nothing if remaining input is too long. An early exit prevents the
- // fuzzer from exploring needlessly long inputs with interesting prefixes.
- if (data_provider.remaining_bytes() > kMaxSniffLength)
- return 0;
- std::string input = data_provider.ConsumeRemainingBytesAsString();
- std::string result;
- net::SniffMimeType(input, GURL(url_string), mime_type_hint,
- force_sniff_file_urls_for_html, &result);
- net::SniffMimeTypeFromLocalData(input, &result);
- return 0;
- }
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