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+.\" $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
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" 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
+.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+.\"
+.Dd $Mdocdate: 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