Rayhaan JaufeerallyandClaude Fable 5.1
39632e3c38
Property tests (run by `cargo test`): - crates/packet/tests/properties.rs: every kind of message, generated, must be written, be as long as wire_len says, and read back equal; and noise, noise behind a valid header, and valid messages with bytes damaged must never do more than return an error. Anything the decoder accepts must be showable and survive being written and read again. - IpPrefix: text round trip, noise as text, `contains` against a bitwise model. - The session's framing: a stream of messages yields the same messages however it is cut into reads. Fuzz targets (fuzz/, cargo-fuzz on nightly, a minute each in CI): raw messages, message bodies behind a valid header, prefix text, the configuration file. Bugs found, each with a named regression test: - A prefix longer than its address family (e.g. an IPv4 NLRI of length 99) was accepted, and showing it panicked. The session logs every route, so one UPDATE from a peer ended the session task. Such a prefix is now malformed, and showing a prefix cannot fail. - Bits past a prefix's length were kept, so the same prefix sent with stray bits was a different key in the RIB. Prefixes now have one form. - An opaque extended community was read as seven octets instead of eight, putting every community after it out of step. - AGGREGATOR could be neither read from nor written to a peer with two-octet AS numbers. - The Outbound Route Filter and Long-Lived Graceful Restart capabilities were written differently from how they are read. - A capability value or unknown attribute too long for its length field was written with the length wrapped around; it is now an error, or for the attribute the two-octet length. Also: ROUTE-REFRESH carries its AFI and SAFI instead of being modelled as an empty message, and one with a body of the wrong length is refused. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Fuzz targets
Coverage-guided fuzzing of everything that reads input we do not control.
The property tests (cargo test, e.g. crates/packet/tests/properties.rs)
check the same things on generated input and run on every build; these
targets go further by letting libFuzzer follow code coverage for as long as
you leave them running.
| Target | Input |
|---|---|
message |
Raw bytes as they come off a TCP connection |
message_body |
A message body behind a correct header (reaches the body parsers) |
prefix_text |
A prefix as text |
config |
The configuration file |
For the two message targets a finding is either a panic, or a message the decoder accepted that cannot be written and read back as itself.
Running
libFuzzer needs a nightly toolchain and cargo-fuzz:
rustup toolchain install nightly
cargo install cargo-fuzz
Then, from this directory:
cargo +nightly fuzz run message_body corpus/message_body seeds/message_body -- -max_total_time=300
The first directory is the working corpus, which the fuzzer adds to and
which is not checked in. seeds/ holds a few valid inputs to start from.
Leave out -max_total_time to run until interrupted.
When it finds something
The input is saved under artifacts/<target>/. Reproduce it with
cargo +nightly fuzz run message_body artifacts/message_body/crash-...
Fix the bug, and add a unit test with the input next to the code it broke,
so that cargo test keeps it fixed without anyone having to run the fuzzer.