166 lines
6.8 KiB
Markdown
166 lines
6.8 KiB
Markdown
|
# libprotobuf-mutator
|
||
|
|
|
||
|
|
[](https://travis-ci.org/google/libprotobuf-mutator)
|
||
|
|
[](https://oss-fuzz-build-logs.storage.googleapis.com/index.html#libprotobuf-mutator)
|
||
|
|
|
||
|
|
## Overview
|
||
|
|
libprotobuf-mutator is a library to randomly mutate
|
||
|
|
[protobuffers](https://github.com/google/protobuf). <BR>
|
||
|
|
It could be used together with guided fuzzing engines, such as [libFuzzer](http://libfuzzer.info).
|
||
|
|
|
||
|
|
## Quick start on Debian/Ubuntu
|
||
|
|
|
||
|
|
Install prerequisites:
|
||
|
|
|
||
|
|
```
|
||
|
|
sudo apt-get update
|
||
|
|
sudo apt-get install protobuf-compiler libprotobuf-dev binutils cmake \
|
||
|
|
ninja-build liblzma-dev libz-dev pkg-config autoconf libtool
|
||
|
|
```
|
||
|
|
|
||
|
|
Compile and test everything:
|
||
|
|
|
||
|
|
```
|
||
|
|
mkdir build
|
||
|
|
cd build
|
||
|
|
cmake .. -GNinja -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_BUILD_TYPE=Debug
|
||
|
|
ninja check
|
||
|
|
```
|
||
|
|
|
||
|
|
Clang is only needed for libFuzzer integration. <BR>
|
||
|
|
By default, the system-installed version of
|
||
|
|
[protobuf](https://github.com/google/protobuf) is used. However, on some
|
||
|
|
systems, the system version is too old. You can pass
|
||
|
|
`LIB_PROTO_MUTATOR_DOWNLOAD_PROTOBUF=ON` to cmake to automatically download and
|
||
|
|
build a working version of protobuf.
|
||
|
|
|
||
|
|
Installation:
|
||
|
|
|
||
|
|
```
|
||
|
|
ninja
|
||
|
|
sudo ninja install
|
||
|
|
```
|
||
|
|
|
||
|
|
This installs the headers, pkg-config, and static library.
|
||
|
|
By default the headers are put in `/usr/local/include/libprotobuf-mutator`.
|
||
|
|
|
||
|
|
## Usage
|
||
|
|
|
||
|
|
To use libprotobuf-mutator simply include
|
||
|
|
[mutator.h](/src/mutator.h) and
|
||
|
|
[mutator.cc](/src/mutator.cc) into your build files.
|
||
|
|
|
||
|
|
The `ProtobufMutator` class implements mutations of the protobuf
|
||
|
|
tree structure and mutations of individual fields.
|
||
|
|
The field mutation logic is very basic --
|
||
|
|
for better results you should override the `ProtobufMutator::Mutate*`
|
||
|
|
methods with more sophisticated logic, e.g.
|
||
|
|
using [libFuzzer](http://libfuzzer.info)'s mutators.
|
||
|
|
|
||
|
|
To apply one mutation to a protobuf object do the following:
|
||
|
|
|
||
|
|
```
|
||
|
|
class MyProtobufMutator : public protobuf_mutator::Mutator {
|
||
|
|
public:
|
||
|
|
// Optionally redefine the Mutate* methods to perform more sophisticated mutations.
|
||
|
|
}
|
||
|
|
void Mutate(MyMessage* message) {
|
||
|
|
MyProtobufMutator mutator;
|
||
|
|
mutator.Seed(my_random_seed);
|
||
|
|
mutator.Mutate(message, 200);
|
||
|
|
}
|
||
|
|
```
|
||
|
|
|
||
|
|
See also the `ProtobufMutatorMessagesTest.UsageExample` test from
|
||
|
|
[mutator_test.cc](/src/mutator_test.cc).
|
||
|
|
|
||
|
|
## Integrating with libFuzzer
|
||
|
|
LibFuzzerProtobufMutator can help to integrate with libFuzzer. For example
|
||
|
|
|
||
|
|
```
|
||
|
|
#include "src/libfuzzer/libfuzzer_macro.h"
|
||
|
|
|
||
|
|
DEFINE_PROTO_FUZZER(const MyMessageType& input) {
|
||
|
|
// Code which needs to be fuzzed.
|
||
|
|
ConsumeMyMessageType(input);
|
||
|
|
}
|
||
|
|
```
|
||
|
|
|
||
|
|
Please see [libfuzzer_example.cc](/examples/libfuzzer/libfuzzer_example.cc) as an example.
|
||
|
|
|
||
|
|
### Mutation post-processing (experimental)
|
||
|
|
Sometimes it's necessary to keep particular values in some fields without which the proto
|
||
|
|
is going to be rejected by fuzzed code. E.g. code may expect consistency between some fields
|
||
|
|
or it may use some fields as checksums. Such constraints are going to be significant bottleneck
|
||
|
|
for fuzzer even if it's capable of inserting acceptable values with time.
|
||
|
|
|
||
|
|
PostProcessorRegistration can be used to avoid such issue and guide your fuzzer towards interesting
|
||
|
|
code. It registers callback which will be called for each message of particular type after each mutation.
|
||
|
|
|
||
|
|
```
|
||
|
|
static protobuf_mutator::libfuzzer::PostProcessorRegistration<MyMessageType> reg = {
|
||
|
|
[](MyMessageType* message, unsigned int seed) {
|
||
|
|
TweakMyMessage(message, seed);
|
||
|
|
}};
|
||
|
|
|
||
|
|
DEFINE_PROTO_FUZZER(const MyMessageType& input) {
|
||
|
|
// Code which needs to be fuzzed.
|
||
|
|
ConsumeMyMessageType(input);
|
||
|
|
}
|
||
|
|
```
|
||
|
|
Optional: Use seed if callback uses random numbers. It may help later with debugging.
|
||
|
|
|
||
|
|
Important: Callbacks should be deterministic and avoid modifying good messages.
|
||
|
|
Callbacks are called for both: mutator generated and user provided inputs, like
|
||
|
|
corpus or bug reproducer. So if callback performs unnecessary transformation it
|
||
|
|
may corrupt the reproducer so it stops triggering the bug.
|
||
|
|
|
||
|
|
Note: You can add callback for any nested message and you can add multiple callbacks for
|
||
|
|
the same message type.
|
||
|
|
```
|
||
|
|
DEFINE_PROTO_FUZZER(const MyMessageType& input) {
|
||
|
|
static PostProcessorRegistration reg1 = {
|
||
|
|
[](MyMessageType* message, unsigned int seed) {
|
||
|
|
TweakMyMessage(message, seed);
|
||
|
|
}};
|
||
|
|
static PostProcessorRegistration reg2 = {
|
||
|
|
[](MyMessageType* message, unsigned int seed) {
|
||
|
|
DifferentTweakMyMessage(message, seed);
|
||
|
|
}};
|
||
|
|
static PostProcessorRegistration reg_nested = {
|
||
|
|
[](MyMessageType::Nested* message, unsigned int seed) {
|
||
|
|
TweakMyNestedMessage(message, seed);
|
||
|
|
}};
|
||
|
|
|
||
|
|
// Code which needs to be fuzzed.
|
||
|
|
ConsumeMyMessageType(input);
|
||
|
|
}
|
||
|
|
```
|
||
|
|
## UTF-8 strings
|
||
|
|
"proto2" and "proto3" handle invalid UTF-8 strings differently. In both cases
|
||
|
|
string should be UTF-8, however only "proto3" enforces that. So if fuzzer is
|
||
|
|
applied to "proto2" type libprotobuf-mutator will generate any strings including
|
||
|
|
invalid UTF-8. If it's a "proto3" message type, only valid UTF-8 will be used.
|
||
|
|
|
||
|
|
## Users of the library
|
||
|
|
* [Chromium](https://cs.chromium.org/search/?q=DEFINE_.*._PROTO_FUZZER%5C\()
|
||
|
|
* [Envoy](https://github.com/envoyproxy/envoy/search?q=DEFINE_TEXT_PROTO_FUZZER+OR+DEFINE_PROTO_FUZZER+OR+DEFINE_BINARY_PROTO_FUZZER&unscoped_q=DEFINE_TEXT_PROTO_FUZZER+OR+DEFINE_PROTO_FUZZER+OR+DEFINE_BINARY_PROTO_FUZZER&type=Code)
|
||
|
|
* [LLVM](https://github.com/llvm-mirror/clang/search?q=DEFINE_TEXT_PROTO_FUZZER+OR+DEFINE_PROTO_FUZZER+OR+DEFINE_BINARY_PROTO_FUZZER&unscoped_q=DEFINE_TEXT_PROTO_FUZZER+OR+DEFINE_PROTO_FUZZER+OR+DEFINE_BINARY_PROTO_FUZZER&type=Code)
|
||
|
|
|
||
|
|
## Bugs found with help of the library
|
||
|
|
|
||
|
|
### Chromium
|
||
|
|
* [AppCache exploit](http://www.powerofcommunity.net/poc2018/ned.pdf) ([Actual still restricted bug](https://bugs.chromium.org/p/chromium/issues/detail?id=888926))
|
||
|
|
* [Stack Buffer Overflow in QuicClientPromisedInfo](https://bugs.chromium.org/p/chromium/issues/detail?id=777728)
|
||
|
|
* [null dereference in sqlite3ExprCompare](https://bugs.chromium.org/p/chromium/issues/detail?id=911251)
|
||
|
|
### Envoy
|
||
|
|
* [strftime overflow](https://github.com/envoyproxy/envoy/pull/4321)
|
||
|
|
* [Heap-use-after-free in Envoy::Upstream::SubsetLoadBalancer::updateFallbackSubset](https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=8028)
|
||
|
|
* [Heap-use-after-free in Envoy::Secret::SecretManagerImpl](https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=11231)
|
||
|
|
* [Heap-buffer-overflow in Envoy::Http::HeaderString](https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=10038)
|
||
|
|
|
||
|
|
## Related materials
|
||
|
|
* [Attacking Chrome IPC: Reliably finding bugs to escape the Chrome sandbox](https://media.ccc.de/v/35c3-9579-attacking_chrome_ipc)
|
||
|
|
* [Structure-aware fuzzing for Clang and LLVM with libprotobuf-mutator](https://www.youtube.com/watch?v=U60hC16HEDY)
|
||
|
|
* [Structure-Aware Fuzzing with libFuzzer](https://github.com/google/fuzzer-test-suite/blob/master/tutorial/structure-aware-fuzzing.md)
|