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136 lines
4.1 KiB
C++
136 lines
4.1 KiB
C++
// __ _____ _____ _____
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// __| | __| | | | JSON for Modern C++ (supporting code)
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// | | |__ | | | | | | version 3.12.0
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// |_____|_____|_____|_|___| https://github.com/nlohmann/json
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//
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// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
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// SPDX-License-Identifier: MIT
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/*
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This file implements a parser test suitable for fuzz testing. Given a byte
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array data, it performs the following steps:
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- j0 = parse(data, allow_exceptions = false)
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- j1 = parse(data)
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- assert(j0 is discarded if parsing j1 fails, and j0 == j1 otherwise)
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- s1 = serialize(j1)
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- j2 = parse(s1)
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- s2 = serialize(j2)
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- assert(s1 == s2)
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- for ignore_comments = false and true: assert(parse(data) and accept(data)
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give the same result for a stream, a non-contiguous iterator range, and a
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FILE* as for the pointer range)
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The pointer range takes the bulk fast paths, the other input adapters read byte
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by byte; see check_input_adapters().
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Furthermore, it parses data with a SAX parser that recovers from every error
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and checks that the events are balanced, that parsing ends, and that valid
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input is parsed without errors (see #3989).
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The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
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drivers.
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*/
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#include "fuzzer_common.hpp"
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#include "fuzzer-recovering_checker.hpp"
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namespace
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{
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// json::parse and json::accept for check_input_adapters()
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struct parse_json
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{
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bool ignore_comments;
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template<typename... Args>
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json operator()(Args&& ... args) const
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{
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return json::parse(std::forward<Args>(args)..., nullptr, true, ignore_comments);
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}
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};
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struct accept_json
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{
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bool ignore_comments;
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template<typename... Args>
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bool operator()(Args&& ... args) const
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{
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return json::accept(std::forward<Args>(args)..., ignore_comments);
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}
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};
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} // namespace
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// see http://llvm.org/docs/LibFuzzer.html
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extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
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{
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// recover from all errors, reading from memory and from a stream
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{
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const auto checker = check_recovering_parse(data, size, json::input_format_t::json);
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assert(checker.events <= (4 * size) + 4);
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assert((checker.errors == 0) == json::accept(data, data + size));
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}
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// step 0: parse input without exceptions
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bool noexcept_threw = false;
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json const j_noexcept = parse_without_exceptions([&] { return json::parse(data, data + size, nullptr, false); }, noexcept_threw);
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// whether step 1 succeeded; if not, the catch blocks below check that
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// step 0 failed, too
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bool parsed = false;
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try
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{
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// step 1: parse input
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json const j1 = json::parse(data, data + size);
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parsed = true;
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// without exceptions, the same input must give the same value
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assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
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try
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{
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// step 2: round trip
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// first serialization
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std::string const s1 = j1.dump();
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// parse serialization
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json const j2 = json::parse(s1);
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// second serialization
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std::string const s2 = j2.dump();
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// serializations must match
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assert(s1 == s2);
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}
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catch (const json::parse_error&)
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{
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// parsing a JSON serialization must not fail
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assert(false);
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}
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}
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catch (const json::parse_error&)
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{
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// parse errors are ok, because input may be random bytes
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assert(parsed || noexcept_threw || j_noexcept.is_discarded());
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}
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catch (const json::out_of_range&)
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{
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// out of range errors may happen if provided sizes are excessive
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assert(parsed || noexcept_threw || j_noexcept.is_discarded());
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}
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// step 3: the other input adapters must read the data alike
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for (const bool ignore_comments :
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{
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false, true
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})
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{
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check_input_adapters(data, size, parse_json{ignore_comments});
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check_input_adapters(data, size, accept_json{ignore_comments});
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}
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// return 0 - non-zero return values are reserved for future use
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return 0;
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}
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