sshd_backdoor

This Project is based on BlackHat USA 2021 and Defcon 29.

About Using ebpf technique, hijacking the process during sshd service getting the ~/.ssh/authorized_keys to authorize user logging and injecting our public key make our login successful.

Demo

Main Process in ebpf program

1. Hook OpenAt syscall enter: check if the sshd process call this, log the pid of sshd.

2. Hook OpenAt Syscall exit: check the pid logged. logging the fd of pid, map pid->fd.

3. Hook Read Syscall enter: check the pid logged. logging the user_space_char_buffer of pid.

4. Hook Read Syscall exit: check the pid logged. find the buffer and change the buffer into our Key. Then delete pid in map to avoid blocking administrators' keys be read.

Usage

$ make help

|=======================================================================================================
|usage:
|       build:  build full sshd_backdoor cli tool. But full sshd_backdoor is just supoorted the demo only
|       generate: Generate the ebpf prog in kernel with clang.
|                         if you need you can set the CFLAGS to append
|       test_ebpf: if you editing the ebpf-c c files and header files
|                          to test the ebpf can be compiled and pass ebpf verifier when load
|       tool_unload: bpftool unload progs.
|       tool_load: bpftool load  progs.
|       bpftrace_keylogging: logging sshd keys.Also it can catch the passwords when logging
|

By the way

sshd keylogging

make bpftrace_keylogging

which logging all message in sshd process. Of Course the key log.

troubleshooting

Common Issue: #6

reference

https://github.com/pathtofile/bad-bpf/blob/main/src/sudoadd.bpf.c

https://www.youtube.com/watch?v=5zixNDolLrg

etc.