SSH Client — ssh / sc

A real interactive SSH client running on the T-Deck, built on the LibSSH-ESP32 port of libssh (libssh 0.11.x). Full modern crypto — curve25519/ECDH key exchange, AES/ChaCha20 ciphers, ed25519/RSA host keys — using the ESP32-S3’s hardware AES/SHA acceleration. Works on both T-Deck and T-Deck Plus.

CMD> cw 3                 # connect to WiFi first
CMD> ssh 192.168.1.10 pi  # then SSH in

Usage 

ssh <ip|name> [user]                  # connect (name = a saved profile)
ssh save <name> <ip> [user] [port]    # save/update a host profile
ssh list                              # list saved profiles
ssh rm <name>                         # delete a profile
  • Connecting requires an active WiFi STA connection — run cw <index> first (the client reuses that connection; it doesn’t touch WiFi mode). The save/list/rm subcommands work without WiFi.
  • If user is omitted you’re prompted for it; the password is always prompted (masked).
  • Connect + key exchange takes ~1–3 s.

Saved host profiles

Instead of retyping the IP and user every time, save a named profile:

CMD> ssh save nas 192.168.1.50 admin
CMD> ssh nas                          # connects to admin@192.168.1.50, asks password
  • Stored in /apps/ssh/hosts.csv as name,ip,port,user — passwords are never saved (a plaintext file on a removable card); you’re always prompted.
  • A bare name (ssh nas) is resolved against the profile list first; anything not found is used directly as an IP/hostname, so ssh 192.168.1.10 and ssh example.com still work.
  • User precedence: an explicit arg overrides the profile’s user, which overrides the prompt. Custom ports are kept per profile (ssh save vps 203.0.113.9 root 2222).
  • Autocomplete completes saved names: ssh ' lists save list rm + your host names, and ssh n' → ssh nas.

Terminal

A colour terminal with scrollback, drawn to the 320×240 screen (≈52×13 chars):

Input Action
Typing Sent straight to the remote shell
Trackpad up / down Scroll through 120 lines of history
Trackpad click Disconnect
  • 16-colour ANSI support — coloured ls, prompts, grep --color render in their real colours; default text is light grey. 256-colour/truecolor codes are mapped down or skipped.
  • Scrollbar on the right edge (cyan; yellow + a [SCROLL -N] header tag while you’re scrolled back). Typing snaps back to live.
  • A minimal VT100 engine handles newlines, CR, backspace, tabs, cursor moves and erase-line/screen. Good for shells, ls, cat, pwd, git, package managers. Full-screen TUIs (vim, htop) render roughly for now.

How it runs

libssh needs a large stack, so the whole session runs in a dedicated FreeRTOS task (~50 KB) while the CLI waits for it to finish. The ESP32-S3’s PSRAM covers the libssh heap comfortably.

Security notes

  • Password is wiped from RAM when the session ends.
  • Host-key verification is currently skipped (trust-on-first-use, no pinning). known_hosts pinning and public-key auth are planned (under /apps/ssh/: known_hosts, keys/).
  • There’s no Ctrl-C yet (the I2C keyboard can’t easily emit control chars) — trackpad-click to disconnect is the way out of a long-running remote command.

Stability

The library docs recommend disabling CONFIG_MBEDTLS_HARDWARE_SHA for stability under concurrency, which isn’t possible with the precompiled Arduino core. SSH crypto and WiFi share the single hardware SHA engine, so if a crash happens during the connect/key-exchange phase, that shared engine is the prime suspect.

SD layout

/apps/ssh/ is created on first boot/format.

  • hosts.csv — saved host profiles (implemented; name,ip,port,user).
  • known_hosts, keys/ — host-key pinning and key auth (planned).

Profile reads/writes happen at command time (WiFi idle), not during a live session, so they’re within the safe SD-access window.