Reusing libafl_targets with native Rust programs in concolic execution

[tuong]

Hi,

I am writing this message as part of the Reliable Systems Lab group at SFU.

We are experimenting LibAFL to do concolic execution on Rust programs, and are currently trying to implement something similar as this fuzzing example:
https://github.com/AFLplusplus/LibAFL/tree/1682ce686298ae1304cae5720cfe6f26a920332d/fuzzers/libfuzzer_stb_image_concolic
but using a Rust program instead of C.

For example, to show the state of what we respectively have as harness functions:

• C code:
  https://github.com/AFLplusplus/LibAFL/blob/1682ce686298ae1304cae5720cfe6f26a920332d/fuzzers/libfuzzer_stb_image_concolic/fuzzer/harness.c

• Rust code:
  https://github.com/sfu-rsl/LibAFL/blob/83606b37b37618155a41a945eec797d7b4586ec2/fuzzers/libfuzzer_rust_concolic/fuzzer/src/main.rs#L196

• C code to be concolic-instrumented:
  https://github.com/AFLplusplus/LibAFL/blob/1682ce686298ae1304cae5720cfe6f26a920332d/fuzzers/libfuzzer_stb_image_concolic/fuzzer/harness_symcc.c

• Rust code to be concolic-instrumented:
  https://github.com/sfu-rsl/symrustc/blob/d136a68f609a3139ee7f94cf9b30b55ab31f2de2/examples/source_0_original_1c_rs/src/main.rs

Although our Rust example concolic executes well as a first try, this solution unfortunately requires us to manually add by hand multiple signals_set near multiple if then else of interests:
https://github.com/sfu-rsl/LibAFL/blob/83606b37b37618155a41a945eec797d7b4586ec2/fuzzers/libfuzzer_rust_concolic/fuzzer/src/main.rs#L218

By looking into more details at LibAFL, we would be interested to use libafl_targets, possibly this:
https://github.com/AFLplusplus/LibAFL/blob/1682ce686298ae1304cae5720cfe6f26a920332d/libafl_targets/src/sancov_pcguard.rs
but we were wondering if there would be a more simpler approach, as we might not be very familiar with low-level Rust, C and LLVM programming. What do you think?

Best,
Frédéric