the gramatron baby fuzzer panicks on an OOB slice acces

[lenawanel]

tested on 7dd7c1a48527342b528cd8565246cb9214b15184

Describe the bug the gramatron babyfuzzer panicks with

thread 'main' panicked at /home/lena/GitClone/LibAFL/libafl/src/generators/gramatron.rs:84:47:
index out of bounds: the len is 0 but the index is 0
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

full backtrace

thread 'main' panicked at /home/lena/GitClone/LibAFL/libafl/src/generators/gramatron.rs:84:47:
index out of bounds: the len is 0 but the index is 0
stack backtrace:
   0:     0x56054aec521c - std::backtrace_rs::backtrace::libunwind::trace::h7ead10aab469b9aa
                               at /rustc/69e97df5ce571a777acd654ec3697ae8d25962ea/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x56054aec521c - std::backtrace_rs::backtrace::trace_unsynchronized::hf548e9e8c1fe3e8d
                               at /rustc/69e97df5ce571a777acd654ec3697ae8d25962ea/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x56054aec521c - std::sys_common::backtrace::_print_fmt::h4f790d56eeca616b
                               at /rustc/69e97df5ce571a777acd654ec3697ae8d25962ea/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x56054aec521c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h30e5bb3d4404f378
                               at /rustc/69e97df5ce571a777acd654ec3697ae8d25962ea/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x56054aeeb25c - core::fmt::rt::Argument::fmt::h35f06f2256f98b43
                               at /rustc/69e97df5ce571a777acd654ec3697ae8d25962ea/library/core/src/fmt/rt.rs:138:9
   5:     0x56054aeeb25c - core::fmt::write::h5005ce68dd6774c4
                               at /rustc/69e97df5ce571a777acd654ec3697ae8d25962ea/library/core/src/fmt/mod.rs:1094:21
   6:     0x56054aec226e - std::io::Write::write_fmt::h8a7c95ddeefaf4be
                               at /rustc/69e97df5ce571a777acd654ec3697ae8d25962ea/library/std/src/io/mod.rs:1714:15
   7:     0x56054aec5004 - std::sys_common::backtrace::_print::hedccafa15bd98864
                               at /rustc/69e97df5ce571a777acd654ec3697ae8d25962ea/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x56054aec5004 - std::sys_common::backtrace::print::h911d101d11c4e8b0
                               at /rustc/69e97df5ce571a777acd654ec3697ae8d25962ea/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x56054aec698a - std::panicking::panic_hook_with_disk_dump::{{closure}}::he8cf7cbd1dd11756
                               at /rustc/69e97df5ce571a777acd654ec3697ae8d25962ea/library/std/src/panicking.rs:278:22
  10:     0x56054aec6678 - std::panicking::panic_hook_with_disk_dump::h3baf172fecd393f6
                               at /rustc/69e97df5ce571a777acd654ec3697ae8d25962ea/library/std/src/panicking.rs:312:9
  11:     0x56054acbc923 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h19e2fec009a93599
                               at /rustc/69e97df5ce571a777acd654ec3697ae8d25962ea/library/alloc/src/boxed.rs:2021:9
[1]    1117745 IOT instruction (core dumped)  RUST_BACKTRACE=full cargo run

To Reproduce Steps to reproduce the behavior:

1. run cargo run in fuzzers/baby_fuzzer_gramatron/

Screen output/Screenshots

thread 'main' panicked at /home/lena/GitClone/LibAFL/libafl/src/generators/gramatron.rs:84:47:
index out of bounds: the len is 0 but the index is 0
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[mkravchik]

Still happens with the latest code

[michael-yxchen]

An upgrade (0.7.3 -> 1.0.0-alpha.1 CHANGELOG) in postcard changes the wire format. The auto.postcard file was generated with the old wire format, and the dependency version was bumped to 1.0 without regenerating the automaton file.

I was able to get baby_fuzzer_gramatron to run by changing postcard dependency to postcard = { version = "0.7" }. That's a temporary fix just to pin the issue. I can regenerate the automaton postcard file with the latest postcard wire format.

auto.json is also out-dated because of changes to Trigger. The file should also be regenerated.