- djm@cvs.openbsd.org 2010/01/30 02:54:53

[openssh.git] / ssh-keyscan.1

diff --git a/ssh-keyscan.1 b/ssh-keyscan.1
index 328d95ab1eb780c3da2065d1ac99b1cbe471ccbd..01f3184621c235be08303a8701c014c95e0bd75f 100644 (file)
--- a/ssh-keyscan.1
+++ b/ssh-keyscan.1
@@ -1,4 +1,4 @@
-.\"    $OpenBSD: ssh-keyscan.1,v 1.8 2001/06/23 17:48:18 itojun Exp $
+.\"    $OpenBSD: ssh-keyscan.1,v 1.28 2010/01/09 23:04:13 dtucker Exp $

 .\"
 .\" Copyright 1995, 1996 by David Mazieres <dm@lcs.mit.edu>.
 .\"
 .\"
 .\" Copyright 1995, 1996 by David Mazieres <dm@lcs.mit.edu>.
 .\"


@@ -6,7 +6,7 @@
 .\" permitted provided that due credit is given to the author and the
 .\" OpenBSD project by leaving this copyright notice intact.
 .\"
 .\" 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
 .Dt SSH-KEYSCAN 1
 .Os
 .Sh NAME


@@ -14,13 +14,20 @@
 .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 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


@@ -29,31 +36,25 @@ 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
+to use IPv6 addresses only.
+.It Fl f Ar file

 Read hosts or
 .Pa addrlist namelist
 pairs from this file, one per line.
 Read hosts or
 .Pa addrlist namelist
 pairs from this file, one per line.


@@ -64,12 +65,83 @@ is supplied instead of a filename,
 will read hosts or
 .Pa addrlist namelist
 pairs from the standard input.
 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
+.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
+Verbose mode.
+Causes
+.Nm
+to print debugging messages about its progress.

 .El
 .El

+.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
+.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
 .Sh EXAMPLES

-Print the host key for machine
+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


@@ -77,24 +149,20 @@ 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

-.Sh FILES
-.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 BUGS
-It generates "Connection closed by remote host" messages on the consoles
-of all the machines it scans.
-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 AUTHORS
 .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
+.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.