Jon Meow
309ec35f95
Change generated with: ``` #!/usr/bin/bash -eux # Helper script for renaming pending work. # Run from the repo root. # Rename executable_semantics in code. sed -i 's/executable_semantics/explorer/g' \ $(git grep -l 'executable_semantics' . | grep -v proposals) sed -i 's/executable semantics/explorer/g' \ $(git grep -l 'executable semantics' . | grep -v proposals) sed -i 's/Executable semantics/Explorer/g' \ $(git grep -l 'Executable semantics' . | grep -v proposals) sed -i 's/Executable Semantics/Explorer/g' \ $(git grep -l 'Executable Semantics' . | grep -v proposals) sed -i 's/EXECUTABLE_SEMANTICS/EXPLORER/g' \ $(git grep -l 'EXECUTABLE_SEMANTICS' . | grep -v proposals) sed -i 's/ExecutableSemantics/Explorer/g' \ $(git grep -l 'ExecutableSemantics' . | grep -v proposals) sed -i 's/executable-semantics/explorer/g' \ $(git grep -l 'executable-semantics' . | grep -v proposals) # This is only needed for the initial move. mv executable_semantics explorer mv explorer/fuzzing/executable_semantics_fuzzer.cpp explorer/fuzzing/explorer_fuzzer.cpp ``` Verified with `bazel test ...`
3.1 KiB
Explorer structured fuzzer
Overview
Fuzz testing is based on generating a large amount of random inputs for a software component in order to trigger bugs and unexpected behavior. Basic fuzzing uses randomly generated arrays of bytes as inputs, which works great for some applications but is problematic for testing the logic that operates on highly structured data, as most random inputs are immediately rejected as invalid before any interesting parts of the code get a chance to run.
Structured fuzzing addresses this issue by ensuring the randomly generated data is itself structured, and as such has a high chance of presenting a valid input.
explorer_fuzzer is a structured fuzzer based on
libprotobuf-mutator, which is a
library to randomly mutate
protobuffers.
The input to the fuzzer is an instance of Carbon::Fuzzing::Carbon proto
randomly generated by the libprotobuf-mutator framework. explorer_fuzzer
converts the proto to a Carbon source code string, and tries to parse and
execute the code using explorer implementation.
Fuzzer data format
libprotobuf-mutator supports fuzzer inputs in either text or binary protocol
buffer format. explorer_fuzzer uses text proto format with Carbon proto
message definition in common/fuzzing/carbon.proto.
Running the fuzzer
The fuzzer can be run in 'unit test' mode, where the fuzzer executes on each
input file from the fuzzer_corpus/ folder, or in 'fuzzing' mode, where the
fuzzer will keep generating random inputs and executing the logic on them until
a crash is triggered, or forever in a bug-free program ;).
To run in 'unit test' mode:
bazel test --config=proto-fuzzer --test_output=all //explorer/fuzzing:explorer_fuzzer
To run in 'fuzzing' mode:
bazel build --config=proto-fuzzer //explorer/fuzzing:explorer_fuzzer
bazel-bin/explorer/fuzzing/explorer_fuzzer
It's also possible to run the fuzzer on a single input:
bazel-bin/explorer/fuzzing/explorer_fuzzer /tmp/crash.textproto
Investigating a crash
To reproduce a crash, run the fuzzer on the crashing input as described above.
A separate tool called fuzzverter can be used for things like converting a
crashing input to Carbon source code for running explorer on the code
directly.
To convert a Fuzzing::Carbon text proto to Carbon source:
bazel-bin/explorer/fuzzing/fuzzverter --mode proto_to_carbon --input /tmp/crash.textproto
Generating new fuzzer corpus entries
The ability of the fuzzing framework to generate 'interesting' inputs can be
improved by providing 'seed' inputs known as the fuzzer corpus. The inputs need
to be a Fuzzing::Carbon text proto.
To generate a text proto from Carbon source:
bazel-bin/explorer/fuzzing/fuzzverter --mode carbon_to_proto --input /tmp/crash.carbon --output /tmp/crash.textproto