- dtucker@cvs.openbsd.org 2010/01/04 01:45:30

[openssh.git] / ssh-keyscan.1

diff --git a/ssh-keyscan.1 b/ssh-keyscan.1
index 4db8c5f15f9d4e07b771e2e7f92a0e43e25d3d71..d9f7bedc6609977e61ea745b95e978c0cee8c062 100644 (file)
--- a/ssh-keyscan.1
+++ b/ssh-keyscan.1
@@ -1,13 +1,12 @@
-.\"    $OpenBSD: ssh-keyscan.1,v 1.5 2001/04/18 16:21:05 ian 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>.
 .\"
 .\" Modification and redistribution in source and binary forms is
 .\" permitted provided that due credit is given to the author and the
 .\"
 .\" Copyright 1995, 1996 by David Mazieres <dm@lcs.mit.edu>.
 .\"
 .\" Modification and redistribution in source and binary forms is
 .\" permitted provided that due credit is given to the author and the

-.\" OpenBSD project (for instance by leaving this copyright notice
-.\" intact).
+.\" OpenBSD project by leaving this copyright notice intact.

 .\"
 .\"

-.Dd January 1, 1996
+.Dd $Mdocdate$

 .Dt SSH-KEYSCAN 1
 .Os
 .Sh NAME
 .Dt SSH-KEYSCAN 1
 .Os
 .Sh NAME


@@ -15,13 +14,21 @@
 .Nd gather ssh public keys
 .Sh SYNOPSIS
 .Nm ssh-keyscan
 .Nd gather ssh public keys
 .Sh SYNOPSIS
 .Nm ssh-keyscan

-.Op Fl t Ar timeout
-.Op Ar -- | host | addrlist namelist
-.Op Fl f Ar files ...
+.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 V Ar rdomain
+.Op Ar host | addrlist namelist
+.Ar ...
+.Ek

 .Sh DESCRIPTION
 .Nm
 is a utility for gathering the public ssh host keys of a number of
 .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
 .Pa ssh_known_hosts
 files.
 .Nm


@@ -30,48 +37,114 @@ scripts.
 .Pp
 .Nm
 uses non-blocking socket I/O to contact as many hosts as possible in
 .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 can be collected in tens of seconds, even when some of those

-hosts are down or do not run ssh.  You do not need login access to the
-machines you are scanning, nor does the scanning process involve
-any encryption.
-.Sh SECURITY
-If you make an ssh_known_hosts file using
+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
 .Nm

-without verifying the keys, you will be vulnerable to
-.I man in the middle
-attacks.
-On the other hand, if your security model allows such a risk,
+to use IPv4 addresses only.
+.It Fl 6
+Forces

 .Nm
 .Nm

-can help you detect tampered keyfiles or man in the middle attacks which
-have begun after you created your ssh_known_hosts file.
-.Sh OPTIONS
-.Bl -tag -width Ds
-.It Fl t
-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.
-.It Fl f
-Read hosts or 
+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
 .Pa addrlist namelist
 pairs from this file, one per line.
 If
 .Pa -
 is supplied instead of a filename,
 .Nm

-will read hosts or 
+will read hosts or

 .Pa addrlist namelist
 pairs from the standard input.
 .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
+.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.
+.It Fl t Ar type
+Specifies the type of the key to fetch from the scanned hosts.
+The possible values are
+.Dq rsa1
+for protocol version 1 and
+.Dq rsa
+or
+.Dq dsa
+for protocol version 2.
+Multiple values may be specified by separating them with commas.
+The default is
+.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.

 .El
 .El

-.Sh EXAMPLES
+.Sh SECURITY
+If an ssh_known_hosts file is constructed using
+.Nm
+without verifying the keys, users will be vulnerable to
+.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 FILES
+.Pa Input format:
+.Bd -literal
+1.2.3.4,1.2.4.4 name.my.domain,name,n.my.domain,n,1.2.3.4,1.2.4.4
+.Ed

 .Pp
 .Pp

-Print the host key for machine
+.Pa Output format for rsa1 keys:
+.Bd -literal
+host-or-namelist bits exponent modulus
+.Ed
+.Pp
+.Pa Output format for rsa and dsa keys:
+.Bd -literal
+host-or-namelist keytype base64-encoded-key
+.Ed
+.Pp
+Where
+.Pa keytype
+is either
+.Dq ssh-rsa
+or
+.Dq ssh-dss .
+.Pp
+.Pa /etc/ssh/ssh_known_hosts
+.Sh EXAMPLES
+Print the
+.Pa rsa
+host key for machine

 .Pa hostname :
 .Bd -literal
 .Pa hostname :
 .Bd -literal

-ssh-keyscan hostname
+$ ssh-keyscan hostname

 .Ed
 .Pp
 Find all hosts from the file
 .Ed
 .Pp
 Find all hosts from the file


@@ -79,26 +152,20 @@ Find all hosts from the file
 which have new or different keys from those in the sorted file
 .Pa ssh_known_hosts :
 .Bd -literal
 which have new or different keys from those in the sorted file
 .Pa ssh_known_hosts :
 .Bd -literal

-$ ssh-keyscan -f ssh_hosts | sort -u - ssh_known_hosts | \e\ 
-       diff ssh_known_hosts -
+$ ssh-keyscan -t rsa,dsa -f ssh_hosts | \e
+       sort -u - ssh_known_hosts | diff ssh_known_hosts -

 .Ed
 .Ed

-.Pp
-.Sh FILES
-.Pp
-.Pa Input format:
-1.2.3.4,1.2.4.4 name.my.domain,name,n.my.domain,n,1.2.3.4,1.2.4.4
-.Pp
-.Pa Output format:
-host-or-namelist bits exponent modulus
-.Pp
-.Pa /etc/ssh_known_hosts
+.Sh SEE ALSO
+.Xr ssh 1 ,
+.Xr sshd 8
+.Sh AUTHORS
+.An -nosplit
+.An David Mazieres Aq dm@lcs.mit.edu
+wrote the initial version, and
+.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
 .Sh BUGS
 It generates "Connection closed by remote host" messages on the consoles

-of all the machines it scans.
+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.
 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.

-.Sh SEE ALSO
-.Xr ssh 1 ,
-.Xr sshd 8
-.Sh AUTHOR
-David Mazieres <dm@lcs.mit.edu>