{"id":27185272,"url":"https://github.com/function61/function22","last_synced_at":"2026-02-24T09:05:18.991Z","repository":{"id":144235313,"uuid":"439847116","full_name":"function61/function22","owner":"function61","description":"A memory-safe SSH server, focused on listening only on VPN networks such as 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unexpected eof while reading","robots_txt_status":"success","robots_txt_updated_at":"2025-07-24T06:49:26.215Z","robots_txt_url":"https://github.com/robots.txt","online":false,"can_crawl_api":true,"host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":["ssh","ssh-server","tailscale"],"created_at":"2025-04-09T17:14:51.824Z","updated_at":"2026-02-24T09:05:18.589Z","avatar_url":"https://github.com/function61.png","language":"Go","funding_links":[],"categories":[],"sub_categories":[],"readme":"![Build status](https://github.com/function61/function22/workflows/Build/badge.svg)\n[![Download](https://img.shields.io/github/downloads/function61/function22/total.svg?style=for-the-badge)](https://github.com/function61/function22/releases)\n\nA memory-safe SSH server, focused on listening only on VPN networks such as Tailscale.\n\n\nFeatures\n--------\n\n- Is tested to work with SCP\n- Integrates well with systemd\n\n\nQuickstart\n----------\n\n[Download binary](https://github.com/function61/function22/releases) for your architecture.\nWe only support Linux.\n\n- If you don't have `/etc/ssh/ssh_host_ed25519_key` (from previous OpenSSH installation perhaps),\n  run `$ ./function22 host-key-generate` to generate it.\n- Run `$ ./function22 install` to start on system startup.\n\n\nSecurity\n--------\n\nThese things improve security when compared to default OpenSSH installation:\n\n- Restricts SSH listening to a VPN interface (like [Tailscale](https://tailscale.com/)), so your SSH\n  server is not reachable directly from public internet.\n- Fully memory safe implementation (Go has native support for SSH protocol).\n- Less features =\u003e less attack surface.\n\t* Only support ed25519 host key\n\nOf course there are security points that OpenSSH is better at, like having had magnitudes of more\nsecurity-conscious people looking at its source code.\nIt is you who ultimately are responsible for your own security, so please consider all implications. :)\n\n\nWhy authenticate at all?\n------------------------\n\nIn theory since Tailscale already has \"IP is identity\" and network-level access controls are by user / device combos,\nyou wouldn't need to authenticate the user at all.\n\nI.e. IP packets arriving at the SSH server (from VPN IP range) is already a sign that user's end\ndevice passes firewall ACLs.\n\nCurrently we still do additional auth for layered security.\nOnce we gain more confidence on the code and understand\n[additional attack vectors](https://github.com/simonw/til/issues/7) better, source-IP-restricted\naccess will be considered.\n\n\nTODO\n----\n\n- Log all failed connection attempts (even though we have network-level security)\n- Perhaps disable password authentication entirely\n- Perhaps use systemd socket activation? Or is that possible when bound to a specific network interface's IP?\n  [Seems possible.](https://www.freedesktop.org/software/systemd/man/systemd.socket.html#BindToDevice=)\n- Make this a library, so it can be embedded in other projects\n- Investigate OpenSSH security facilities to learn if we can add any security-increasing tricks\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Ffunction61%2Ffunction22","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Ffunction61%2Ffunction22","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Ffunction61%2Ffunction22/lists"}