Fuzzing libchewing

Fuzzing is a technique to find edge cases that could crash or hang the library. We use the AFL++ fuzzing framework. See https://aflplus.plus/ for information.

Dependencies

We need AFL++ itself and cargo-afl to compile instrumented binaries.

Install AFL++

sudo apt install afl++

or

sudo dnf install american-fuzzy-lop

Install cargo-afl

cargo install cargo-afl

Build the Fuzzers

It's recommended to build the fuzzers with instrumentation using cargo-afl. AFL++ can use the instrumentation to find interesting inputs much faster.

cargo afl build --release

Fuzzing the Fuzzers

First prepare the required input/output directory, populate the input with initial seeds.

mkdir in out
dd if=/dev/urandom of=in/seed.bin bs=256 count=1

Then pick the fuzzer you want to run, invoke AFL. Each fuzzer might require different input. Check --help.

afl-fuzz -i in -o out -- ../target/release/fuzzer ../out/build/rust/data/

Fuzzers

fuzzer

This fuzzer is similar to the testchewing command. It interprets binary input as chewing commands then call corresponding methods to simulate user inputs.

ARGS:
    <syspath>
      system dictionary path

OPTIONS:
    -h, --help
      Prints help information.

trieloader

This fuzzer tries to load input as a trie dictionary, then query metadata and look up phrases.

ARGS:
    <dict_path>
      Trie dictionary path

OPTIONS:
    -h, --help
      Prints help information.

cdbloader

This fuzzer tries to load input as a CDB dictionary, then query metadata and look up phrases.

ARGS:
    <dict_path>
      Trie dictionary path

OPTIONS:
    -h, --help
      Prints help information.