rust-for-the-haters/rust-teeny

Tiny stripped rust binary (8.0 KiB, x86_64, dynamic libc) that loads and executes a shellcode payload built into it.

Building

Just just build. Mostly uses CLI flags, but most could be moved into the Cargo.toml, needs a nightly compiler as of rust 1.96.0, the rust-toolchain.toml should take care of that though.

It assumes building for x86_64-unknown-linux-gnu as I cannot manage to get a musl build and I don't know other architectures which need manual shellcode addition. But this can be extended to other architectures.

Properties

The code is completely correct, checks mmap and mprotect succeeded, the code could theoretically be smaller but less correct by:

• Memory mapping a RWX page directly, some protected kernel builds require RW -> RX transition though.
• Assuming mmap and mprotect succeeded, no modern kernel should fail on mmap even if out of memory, the mapping is done regardless and memory actually reserved once used. mprotect shouldn't fail either if done correctly (man page mentions failures because no memory, which I said shouldn't happen, invalid permission combinations and invalid, which don't happen if you do correct permissions and valid pointers, or rare permission cases).
• no_std, this barely needs std, could just hardcode the 3-4 syscalls present and don't use std at all. This code also hardcoded libc values before so that's not needed either, but I think libc has no_std support either way.
• 0.1 KiB can be removed if you get rid of .gnu.hash and .gnu.version sections, but I think those can be required on other machines, not on mine though.