-.\" $OpenBSD: ssh-keyscan.1,v 1.12 2001/09/05 06:23:07 deraadt Exp $
+.\" $OpenBSD: ssh-keyscan.1,v 1.27 2009/10/28 16:38:18 reyk Exp $
.\"
.\" Copyright 1995, 1996 by David Mazieres <dm@lcs.mit.edu>.
.\"
.\" permitted provided that due credit is given to the author and the
.\" OpenBSD project by leaving this copyright notice intact.
.\"
-.Dd January 1, 1996
+.Dd $Mdocdate$
.Dt SSH-KEYSCAN 1
.Os
.Sh NAME
.Nd gather ssh public keys
.Sh SYNOPSIS
.Nm ssh-keyscan
-.Op Fl v46
+.Bk -words
+.Op Fl 46Hv
+.Op Fl f Ar file
.Op Fl p Ar port
.Op Fl T Ar timeout
.Op Fl t Ar type
-.Op Fl f Ar file
+.Op Fl V Ar rdomain
.Op Ar host | addrlist namelist
-.Op Ar ...
+.Ar ...
+.Ek
.Sh DESCRIPTION
.Nm
is a utility for gathering the public ssh host keys of a number of
-hosts. It was designed to aid in building and verifying
+hosts.
+It was designed to aid in building and verifying
.Pa ssh_known_hosts
files.
.Nm
.Pp
.Nm
uses non-blocking socket I/O to contact as many hosts as possible in
-parallel, so it is very efficient. The keys from a domain of 1,000
+parallel, so it is very efficient.
+The keys from a domain of 1,000
hosts can be collected in tens of seconds, even when some of those
-hosts are down or do not run ssh. For scanning, one does not need
+hosts are down or do not run ssh.
+For scanning, one does not need
login access to the machines that are being scanned, nor does the
scanning process involve any encryption.
.Pp
The options are as follows:
.Bl -tag -width Ds
+.It Fl 4
+Forces
+.Nm
+to use IPv4 addresses only.
+.It Fl 6
+Forces
+.Nm
+to use IPv6 addresses only.
+.It Fl f Ar file
+Read hosts or
+.Pa addrlist namelist
+pairs from this file, one per line.
+If
+.Pa -
+is supplied instead of a filename,
+.Nm
+will read hosts or
+.Pa addrlist namelist
+pairs from the standard input.
+.It Fl H
+Hash all hostnames and addresses in the output.
+Hashed names may be used normally by
+.Nm ssh
+and
+.Nm sshd ,
+but they do not reveal identifying information should the file's contents
+be disclosed.
.It Fl p Ar port
Port to connect to on the remote host.
.It Fl T Ar timeout
-Set the timeout for connection attempts. If
+Set the timeout for connection attempts.
+If
.Pa timeout
seconds have elapsed since a connection was initiated to a host or since the
last time anything was read from that host, then the connection is
-closed and the host in question considered unavailable. Default is 5
-seconds.
+closed and the host in question considered unavailable.
+Default is 5 seconds.
.It Fl t Ar type
Specifies the type of the key to fetch from the scanned hosts.
The possible values are
for protocol version 2.
Multiple values may be specified by separating them with commas.
The default is
-.Dq rsa1 .
-.It Fl f Ar filename
-Read hosts or
-.Pa addrlist namelist
-pairs from this file, one per line.
-If
-.Pa -
-is supplied instead of a filename,
-.Nm
-will read hosts or
-.Pa addrlist namelist
-pairs from the standard input.
+.Dq rsa .
+.It Fl V Ar rdomain
+Set the routing domain.
.It Fl v
Verbose mode.
Causes
.Nm
to print debugging messages about its progress.
-.It Fl 4
-Forces
-.Nm
-to use IPv4 addresses only.
-.It Fl 6
-Forces
-.Nm
-to use IPv6 addresses only.
.El
.Sh SECURITY
-If a ssh_known_hosts file is constructed using
+If an ssh_known_hosts file is constructed using
.Nm
without verifying the keys, users will be vulnerable to
-.I man in the middle
+.Em man in the middle
attacks.
On the other hand, if the security model allows such a risk,
.Nm
can help in the detection of tampered keyfiles or man in the middle
attacks which have begun after the ssh_known_hosts file was created.
-.Sh EXAMPLES
-.Pp
-Print the
-.Pa rsa1
-host key for machine
-.Pa hostname :
-.Bd -literal
-ssh-keyscan hostname
-.Ed
-.Pp
-Find all hosts from the file
-.Pa ssh_hosts
-which have new or different keys from those in the sorted file
-.Pa ssh_known_hosts :
-.Bd -literal
-ssh-keyscan -t rsa,dsa -f ssh_hosts | \e\
- sort -u - ssh_known_hosts | diff ssh_known_hosts -
-.Ed
.Sh FILES
.Pa Input format:
.Bd -literal
is either
.Dq ssh-rsa
or
-.Dq ssh-dsa .
+.Dq ssh-dss .
.Pp
-.Pa /etc/ssh_known_hosts
-.Sh BUGS
-It generates "Connection closed by remote host" messages on the consoles
-of all the machines it scans if the server is older than version 2.9.
-This is because it opens a connection to the ssh port, reads the public
-key, and drops the connection as soon as it gets the key.
+.Pa /etc/ssh/ssh_known_hosts
+.Sh EXAMPLES
+Print the
+.Pa rsa
+host key for machine
+.Pa hostname :
+.Bd -literal
+$ ssh-keyscan hostname
+.Ed
+.Pp
+Find all hosts from the file
+.Pa ssh_hosts
+which have new or different keys from those in the sorted file
+.Pa ssh_known_hosts :
+.Bd -literal
+$ ssh-keyscan -t rsa,dsa -f ssh_hosts | \e
+ sort -u - ssh_known_hosts | diff ssh_known_hosts -
+.Ed
.Sh SEE ALSO
.Xr ssh 1 ,
.Xr sshd 8
.Sh AUTHORS
-David Mazieres <dm@lcs.mit.edu>
+.An -nosplit
+.An David Mazieres Aq dm@lcs.mit.edu
wrote the initial version, and
-Wayne Davison <wayned@users.sourceforge.net>
+.An Wayne Davison Aq wayned@users.sourceforge.net
added support for protocol version 2.
+.Sh BUGS
+It generates "Connection closed by remote host" messages on the consoles
+of all the machines it scans if the server is older than version 2.9.
+This is because it opens a connection to the ssh port, reads the public
+key, and drops the connection as soon as it gets the key.
andersk / openssh.git / blobdiff