Manual: systemd-ssh-generator

SYSTEMD-SSH-GENERATOR(8)		    systemd-ssh-generator		    SYSTEMD-SSH-GENERATOR(8)

NAME
       systemd-ssh-generator - Generator for binding a socket-activated SSH server to local AF_VSOCK and
       AF_UNIX sockets

SYNOPSIS
       /usr/lib/systemd/system-generators/systemd-ssh-generator

DESCRIPTION
       systemd-ssh-generator binds a socket-activated SSH server to local AF_VSOCK and AF_UNIX sockets under
       certain conditions. It only has an effect if the sshd(8) binary is installed. Specifically, it does
       the following:

       •   If invoked in a VM with AF_VSOCK support, a socket-activated SSH per-connection service is bound
	   to AF_VSOCK port 22.

       •   If invoked in a container environment with a writable directory /run/host/unix-export/
	   pre-mounted it binds SSH to an AF_UNIX socket /run/host/unix-export/ssh. The assumption is that
	   this directory is bind mounted to the host side as well, and can be used to connect to the
	   container from there. See Container Interface[1] for more information about this interface.

       •   A local AF_UNIX socket /run/ssh-unix-local/socket is also bound, unconditionally. This may be
	   used for SSH communication from the host to itself, without involving networking, for example to
	   traverse security boundaries safely and with secure authentication.

       •   Additional AF_UNIX and AF_VSOCK sockets are optionally bound, based on the systemd.ssh_listen=
	   kernel command line option or the ssh.listen system credential (see below).

       See systemd-ssh-proxy(1) for details on how to connect to these sockets via the ssh client.

       The ssh.authorized_keys.root credential can be used to allow specific public keys to log in over SSH.
       See systemd.system-credentials(7) for more information.

       The generator will use a packaged sshd@.service service template file if one exists, and otherwise
       generate a suitable service template file.

       systemd-ssh-generator implements systemd.generator(7).

KERNEL COMMAND LINE
       systemd-ssh-generator understands the following kernel-command-line(7) parameters:

       systemd.ssh_auto=
	   This option takes an optional boolean argument, and defaults to yes. If enabled, the automatic
	   binding to the AF_VSOCK and AF_UNIX sockets listed above is done. If disable, this is not done,
	   except for those explicitly requested via systemd.ssh_listen= on the kernel command line or via
	   the ssh.listen system credential.

	   Added in version 256.

       systemd.ssh_listen=
	   This option configures an additional socket to bind SSH to. It may be used multiple times to bind
	   multiple sockets. The syntax should follow the one of ListenStream=, see systemd.socket(5) for
	   details. This functionality supports all socket families systemd(1) supports, including AF_INET
	   and AF_INET6.

	   Added in version 256.

CREDENTIALS
       systemd-ssh-generator supports the system credentials logic. The following credentials are used when
       passed in:

       ssh.listen
	   This credential should be a text file, with each line referencing one additional socket to bind
	   SSH to. The syntax should follow the one of ListenStream=, see systemd.socket(5) for details.
	   This functionality supports all socket families systemd supports, including AF_INET and AF_INET6.

	   Added in version 256.

       ssh.ephemeral-authorized_keys-all
	   Provides additional public keys, given in the customary authorized_keys format, for all users,
	   for incoming connections via the generated AF_VSOCK and AF_UNIX socket units.

	   The intended use of this is for a host system (in either VM or container configurations) to
	   generate a keypair and inject the public key into the guest, using the private key to connect to
	   any user account on the guest via ssh, without further authentication.

	   Added in version 256.

SEE ALSO
       systemd(1), kernel-command-line(7), systemd.system-credentials(7), vsock(7), unix(7), ssh(1), sshd(8)

NOTES
	1. Container Interface
	   https://systemd.io/CONTAINER_INTERFACE

systemd 259.5									    SYSTEMD-SSH-GENERATOR(8)