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update to use FMT_FUZZ

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Signed-off-by: Asra Ali <asraa@google.com>
This commit is contained in:
Asra Ali 2020-04-28 15:30:49 -04:00
parent 9aa1517525
commit ca0fb3040c
4 changed files with 20 additions and 15 deletions
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6
include/fmt/format-inl.h
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@ -1151,10 +1151,10 @@ int snprintf_float(T value, int precision, float_specs specs,
for (;;) {
auto begin = buf.data() + offset;
auto capacity = buf.capacity() - offset;
#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
#ifdef FUZZ_MODE
if (precision > 100000)
FMT_THROW(std::runtime_error(
"fuzz mode - avoid large allocation inside snprintf"));
throw std::runtime_error(
"fuzz mode - avoid large allocation inside snprintf");
#endif
// Suppress the warning about a nonliteral format string.
// Cannot use auto becase of a bug in MinGW (#1532).

8
include/fmt/format.h
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@ -699,8 +699,8 @@ class basic_memory_buffer : public internal::buffer<T> {
template <typename T, std::size_t SIZE, typename Allocator>
void basic_memory_buffer<T, SIZE, Allocator>::grow(std::size_t size) {
#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
if (size > 1000) FMT_THROW(std::runtime_error("fuzz mode - won't grow that much"));
#ifdef FUZZ_MODE
if (size > 1000) throw std::runtime_error("fuzz mode - won't grow that much");
#endif
std::size_t old_capacity = this->capacity();
std::size_t new_capacity = old_capacity + old_capacity / 2;
@ -1136,9 +1136,9 @@ template <typename Char> class float_writer {
*it++ = static_cast<Char>('0');
return it;
}
#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
#ifdef FUZZ_MODE
if (num_zeros > 1000)
FMT_THROW(std::runtime_error("fuzz mode - avoiding excessive cpu use"));
throw std::runtime_error("fuzz mode - avoiding excessive cpu use");
#endif
it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
}

6
src/format.cc
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@ -13,10 +13,10 @@ namespace internal {
template <typename T>
int format_float(char* buf, std::size_t size, const char* format, int precision,
T value) {
#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
#ifdef FUZZ_MODE
if (precision > 100000)
FMT_THROW(std::runtime_error(
"fuzz mode - avoid large allocation inside snprintf"));
throw std::runtime_error(
"fuzz mode - avoid large allocation inside snprintf");
#endif
// Suppress the warning about nonliteral format string.
int (*snprintf_ptr)(char*, size_t, const char*, ...) = FMT_SNPRINTF;

15
test/fuzzing/README.md
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@ -7,14 +7,19 @@ in fmt. It is a part of the continous fuzzing at
The source code is modified to make the fuzzing possible without locking up on
resource exhaustion:
```cpp
#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
#ifdef FUZZ_MODE
if(spec.precision>100000) {
FMT_THROW(std::runtime_error("fuzz mode - avoiding large precision"));
throw std::runtime_error("fuzz mode - avoiding large precision");
}
#endif
```
This macro is the defacto standard for making fuzzing practically possible, see
[the libFuzzer documentation](https://llvm.org/docs/LibFuzzer.html#fuzzer-friendly-build-mode).
```
This macro `FUZZ_MODE` is enabled on OSS-Fuzz builds and makes fuzzing
practically possible. It is used in fmt code to prevent resource exhaustion in
fuzzing mode.
The macro `FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION` is the
defacto standard for making fuzzing practically possible to disable certain
fuzzing-unfriendly features (for example, randomness), see [the libFuzzer
documentation](https://llvm.org/docs/LibFuzzer.html#fuzzer-friendly-build-mode).
## Running the fuzzers locally