Use fuzzing for testing

[djc]

Initially, can use this to test decoding routines. There's an example at https://github.com/djc/tokio-imap/tree/master/imap-proto/fuzz that might be useful in getting this off the ground.

[spacejam]

Happy to lend a hand on this. Which specific decoding methods are high priority for this?

[djc]

Great, your help is much appreciated! Packet decoding by way of Endpoint::handle() would be a good starting point.

[Ralith]

Naively we could just throw fuzzer data as UDP packets at the implementation, but that wouldn't get us very far because the fuzzer is spectacularly unlikely to make any progress through the cryptographic handshake, leaving the bulk of the implementation untested. A good solution for end-to-end testing might be to add a hook to inject arbitrary data into the plaintext of an arbitrary packet between arbitrary frames, then use that in a fuzzing target to perturb an otherwise valid scripted session like the lifecycle unit test.

[Ralith]

Now that we've gracefully encapsulated the stream logic into the Streams type, it would make an excellent candidate for targeted fuzzing without any elaborate measures needed. As illustrated in #774, there's definitely enough complexity there to merit it.

[stammw]

A fuzzing effort has been made for VarInt on h3. Would you be interested to import it ?

[Ralith]

Certainly! I'm going to go ahead and close this since we've got some fuzzing going now; we should open new issues for specific interfaces of interest.

[hmuint32]

@djc, i am having compilation issue with: cargo fuzz check in one of my local dev with stable rust.

92 |     use arbitrary::{Arbitrary, Result, Unstructured};
   |         ^^^^^^^^^ use of undeclared crate or module `arbitrary`

error[E0432]: unresolved import `arbitrary`
  --> /localpath/.cargo/registry/src/index.crates.io-6f17d22bba15001f/quinn-proto-0.10.6/src/lib.rs:92:9
   |
92 |     use arbitrary::{Arbitrary, Result, Unstructured};
   |         ^^^^^^^^^ use of undeclared crate or module `arbitrary`

    Checking zbus v3.10.0
For more information about this error, try `rustc --explain E0432`.
error: could not compile `quinn-proto` (lib) due to 1 previous error
warning: build failed, waiting for other jobs to finish...
Error: failed to build fuzz script: ASAN_OPTIONS="detect_odr_violation=0" RUSTFLAGS="-Cpasses=sancov-module -Cllvm-args=-sanitizer-coverage-level=4 -Cllvm-args=-sanitizer-coverage-inline-8bit-counters -Cllvm-args=-sanitizer-coverage-pc-table -Cllvm-args=-sanitizer-coverage-trace-compares --cfg fuzzing -Clink-dead-code -Zsanitizer=address -Cllvm-args=-sanitizer-coverage-stack-depth -Cdebug-assertions -C codegen-units=1" "cargo" "check" "--manifest-path"

For Posterity, i am including quinn-proto as part of my fuzz target's Cargo.toml as
quinn-proto = { version = "0.10.6", features = ["arbitrary"] } , to get my build to be successful. I guess it'd be nice to have that documented somewhere, not an issue..

[djc]

Happy to review a PR with documentation improvements!