SSH Stamp

Sponsored by:

⚠️ WARNING: Pre-alpha PoC quality, DO NOT use in production. Currently contains highly unsafe business logic auth issues (both password and key management handlers need to be fixed).

⚠️ WARNING: Do not file CVEs reports since deficiencies are very much known at this point in time and they'll be worked on soon as part of this NLNet SSH-Stamp research and development grant ;)

Expect panics, lost bytes on the UART and other tricky UX issues, we are working on it, pull-requests are accepted too!

Description

Your everyday SSH secured serial access.

The SSH Stamp is a secure wireless to UART bridge implemented in Rust (no_std, no_alloc and no_unsafe whenever possible) with simplicity and robustness as its main design tenets.

The firmware runs on a microcontroller running Secure SHell Protocol (RFC 4253 and related IETF standards series). This firmware can be used for multiple purposes, conveniently avoiding physical tethering and securely tunneling traffic via SSH by default: easily add telemetry to a (moving) robot, monitor and operate any (domestic) appliance remotely, conduct remote cybersecurity audits on network gear of a company, reverse engineer hardware and software for right to repair purposes, just to name a few examples.

A "low level to SSH Swiss army knife".

Building

Rust versions are controlled via rust-toolchain.toml and the equivalent defined on the CI workflow.

Required for all targets:

rustup toolchain install stable --component rust-src
cargo install espflash

On a fresh system the following should be enough to build and run on an ESP32-C6 dev board.

rustup target add riscv32imac-unknown-none-elf
cargo build-esp32c6
cargo run-esp32c6

Build and run for ESP32-C2 / ESP32-C3:

rustup target add riscv32imc-unknown-none-elf
cargo build-esp32c2
cargo build-esp32c3
cargo run-esp32c2
cargo run-esp32c3

Build for ESP32 / ESP32-S2 / ESP32-S3 (Xtensa Cores) - Install esp toolchain first: https://github.com/esp-rs/espup

cargo install espup
espup install
$HOME/export-esp.sh
rustup override set esp
cargo build-esp32
cargo build-esp32s2
cargo build-esp32s3

Running on the target:

cargo run-esp32
cargo run-esp32s2
cargo run-esp32s3

Alternatively to not use rustup override:

cargo +esp build-esp32
cargo +esp build-esp32s2
cargo +esp build-esp32s3

Running on the target:

cargo +esp run-esp32
cargo +esp run-esp32s2
cargo +esp run-esp32s3

Example usecases

The following depicts a typical OpenWrt router with a (prototype) SSH Stamp connected to its UART. After ssh-ing into the SSH Stamp, one can interact with the router's UART "off band", to i.e:

1. Recover from OpenWrt not booting without needing to open up the case and connect a wired TTL2USB converter. A simple SSH-based BMC.
2. Capture kernel panics during your router's (ab)normal operation. I.e: to debug a buggy wireless driver.
3. Re-provision the whole OpenWrt installation without having to physically unmount the device from its place, all from your wireless SSH shell comfort.

Here are some PoC shots:

Generate SBOM

cargo install cargo-cyclonedx
cargo cyclonedx -f json --manifest-path ./docs/