.\"	$NetBSD: ssh-keysign.8,v 1.12.14.1 2023/12/25 12:31:07 martin Exp $
.\" $OpenBSD: ssh-keysign.8,v 1.17 2022/03/31 17:27:27 naddy Exp $
.\"
.\" Copyright (c) 2002 Markus Friedl.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
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.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.Dd March 31 2022
.Dt SSH-KEYSIGN 8
.Os
.Sh NAME
.Nm ssh-keysign
.Nd OpenSSH helper for host-based authentication
.Sh SYNOPSIS
.Nm
.Sh DESCRIPTION
.Nm
is used by
.Xr ssh 1
to access the local host keys and generate the digital signature
required during host-based authentication.
.Pp
.Nm
is disabled by default and can only be enabled in the
global client configuration file
.Pa /etc/ssh/ssh_config
by setting
.Cm EnableSSHKeysign
to
.Dq yes .
.Pp
.Nm
is not intended to be invoked by the user, but from
.Xr ssh 1 .
See
.Xr ssh 1
and
.Xr sshd 8
for more information about host-based authentication.
.Sh FILES
.Bl -tag -width Ds -compact
.It Pa /etc/ssh/ssh_config
Controls whether
.Nm
is enabled.
.Pp
.It Pa /etc/ssh/ssh_host_dsa_key
.It Pa /etc/ssh/ssh_host_ecdsa_key
.It Pa /etc/ssh/ssh_host_ed25519_key
.It Pa /etc/ssh/ssh_host_rsa_key
These files contain the private parts of the host keys used to
generate the digital signature.
They should be owned by root, readable only by root, and not
accessible to others.
Since they are readable only by root,
.Nm
must be set-uid root if host-based authentication is used.
.Pp
.It Pa /etc/ssh/ssh_host_dsa_key-cert.pub
.It Pa /etc/ssh/ssh_host_ecdsa_key-cert.pub
.It Pa /etc/ssh/ssh_host_ed25519_key-cert.pub
.It Pa /etc/ssh/ssh_host_rsa_key-cert.pub
If these files exist, they are assumed to contain public certificate
information corresponding with the private keys above.
.El
.Sh SEE ALSO
.Xr ssh 1 ,
.Xr ssh-keygen 1 ,
.Xr ssh_config 5 ,
.Xr sshd 8
.Sh HISTORY
.Nm
first appeared in
.Ox 3.2 .
.Sh AUTHORS
.An Markus Friedl Aq Mt markus@openbsd.org