Signals

An eBPF based engine to capture and forward POSIX signals being sent. This project hooks an eBPF program to Kernel and make the signals available through a Unix socket on the filesystem.

Prerequisites

Before getting started you will need the Rust stable and nightly toolchains installed on your system. This is easily achieved with rustup:

$ rustup install stable
$ rustup toolchain install nightly --component rust-src

Once you have the Rust toolchains installed, you must also install bpf-linker. The linker depends on LLVM, and it can be built against the version shipped with the rust toolchain if you are running on a linux x86_64 system with:

$ cargo install bpf-linker

NOTE If you are using Debian you will also need to have the package build-essential installed on the system.

Building

To build the debug version (version with debug symbols and all):

$ make

To build the release (the stripped down version):

$ make release

Run

To run the debug version:

$ sudo RUST_LOG=debug ./target/debug/signals

To run the "released" version:

$ sudo ./target/release/signals

Examples

In one terminal, run the signals binary as root:

$ sudo ./target/debug/signals
[2022-11-30T19:54:02Z INFO  signals]        / /\        /\ \       /\ \        
[2022-11-30T19:54:02Z INFO  signals]       / /  \       \ \ \     /  \ \       
[2022-11-30T19:54:02Z INFO  signals]      / / /\ \__    /\ \_\   / /\ \_\      
[2022-11-30T19:54:02Z INFO  signals]     / / /\ \___\  / /\/_/  / / /\/_/      
[2022-11-30T19:54:02Z INFO  signals]     \ \ \ \/___/ / / /    / / / _____     
[2022-11-30T19:54:02Z INFO  signals]      \ \ \      / / /    / / / /\_____\   
[2022-11-30T19:54:02Z INFO  signals]  _    \ \ \    / / /    / / /  \/____ /   
[2022-11-30T19:54:02Z INFO  signals] /_/\__/ / /___/ / /__  / / /_____/ / /    
[2022-11-30T19:54:02Z INFO  signals] \ \/___/ //\__\/_/___\/ / /______\/ /     
[2022-11-30T19:54:02Z INFO  signals]  \_____\/ \/_________/\/___________/      
[2022-11-30T19:54:02Z INFO  signals] signal emitter development version 
[2022-11-30T19:54:02Z INFO  signals] unix socket listening on /var/run/signals
[2022-11-30T19:54:02Z INFO  signals] loading and attaching to the ebpf program
[2022-11-30T19:54:02Z INFO  signals] awaiting for new connections

Signals are now available under /var/run/signals socket, you can receive them by listening on that socket, as an example let's use nc (note that not all nc versions have support for Unix Sockets). In a new terminal run:

$ # sudo socat - UNIX-CONNECT:/var/run/signals # Alternative command
$ sudo nc.openbsd -U /var/run/signals
{"pid":671,"signr":9}
{"signr":17,"pid":668}
{"signr":17,"pid":679}
{"signr":1,"pid":679}
{"pid":678,"signr":17}
{"signr":17,"pid":672}
{"signr":17,"pid":1}
{"pid":341,"signr":17}
{"pid":668,"signr":28}
{"pid":668,"signr":17}
{"pid":668,"signr":1}
{"pid":667,"signr":17}
{"signr":17,"pid":661}
{"signr":17,"pid":1}
{"signr":17,"pid":341}
{"pid":405,"signr":28}
...