feat: add ssh server (sshd)

2026-08-11 12:53:36 +02:00
parent 69725658cf
commit 0a91131cb0
15 changed files with 2365 additions and 4 deletions
@@ -0,0 +1,65 @@
+.TH SSHD 1
+.SH NAME
+sshd \- MontaukOS SSH-2 server
+.SH SYNOPSIS
+.B sshd
+.SH DESCRIPTION
+.B sshd
+accepts SSH-2 connections and gives each authenticated user a MontaukOS shell.
+
+It is normally launched automatically by
+.BR init (1)
+and does not require direct user interaction. Remote access is disabled by
+default; enable it from Settings > SSH Server, which sets
+.I services.ssh.enabled
+in
+.IR 0:/config/init.toml .
+The change takes effect on the next boot.
+.SH AUTHENTICATION
+Passwords are the only supported method, checked against the MontaukOS account
+database. A user must additionally be listed in the
+.I [allow]
+table of
+.I 0:/config/ssh.toml
+before a login is accepted; users absent from that table are refused. The
+Settings applet maintains this table.
+
+Failed passwords are delayed, and a connection is dropped after eight attempts.
+.SH CONFIGURATION
+.TP
+.I 0:/config/ssh.toml
+Listening port
+.RI ( server.port ,
+default 22) and the per-user
+.I [allow]
+table.
+.TP
+.I 0:/config/ssh_hostkey.toml
+The RSA host key, generated on first start. Note that the filesystem has no
+permission model, so this file is readable by any local process; keeping it
+separate from
+.I ssh.toml
+limits exposure but is not access control.
+.SH DIAGNOSTICS
+Messages go to the boot console only. They do not appear in
+.BR klog (1):
+.B SYS_PRINT
+writes the kernel terminal rather than the kernel log ring, and is discarded
+entirely once the desktop suppresses console output. There is currently nowhere
+to read them from on a running desktop.
+.SH PROTOCOL
+Key exchange is diffie-hellman-group14-sha256 with an rsa-sha2-256 host key;
+the transport uses aes128-ctr with hmac-sha2-256. Client-initiated rekeying is
+supported. Only one session channel per connection is served, and connections
+are handled one at a time.
+.SH LIMITATIONS
+Public key authentication, port forwarding, X11 forwarding, SFTP and SCP are not
+implemented.
+
+.I exec
+requests run the command by feeding it to an interactive shell, so the shell
+prompt and the echoed command line appear in the output. Scripts that parse
+remote command output should account for this.
+.SH SEE ALSO
+.BR shell (1),
+.BR init (1)