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124 lines
3.8 KiB
C++
124 lines
3.8 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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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 <cassert>
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#include <nlohmann/json.hpp>
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// the round-trip checks below are assertions; NDEBUG would compile them away
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#ifdef NDEBUG
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#error "the fuzzer drivers must be built without NDEBUG"
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#endif
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#include "fuzzer-recovering_checker.hpp"
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using json = nlohmann::json;
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// compares dumps rather than values, because NaN != NaN; keep writes strings
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// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
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static bool same_value(const json& lhs, const json& rhs)
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{
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return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
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}
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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; a parse error must then be
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// reported as a discarded value, never thrown
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json j_noexcept;
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bool noexcept_threw = false;
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try
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{
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j_noexcept = json::parse(data, data + size, nullptr, false);
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}
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catch (const json::parse_error&)
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{
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assert(false);
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}
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catch (const json::exception&)
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{
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// type and out-of-range errors are not parse errors and still throw
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noexcept_threw = true;
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}
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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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// 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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