djm@openbsd.org | 873d3e7 | 2017-04-30 23:18:44 +0000 | [diff] [blame] | 1 | .\" $OpenBSD: ssh-keyscan.1,v 1.39 2017/04/30 23:18:44 djm Exp $ |
Ben Lindstrom | b22c2b8 | 2001-03-05 06:50:47 +0000 | [diff] [blame] | 2 | .\" |
| 3 | .\" Copyright 1995, 1996 by David Mazieres <dm@lcs.mit.edu>. |
| 4 | .\" |
| 5 | .\" Modification and redistribution in source and binary forms is |
| 6 | .\" permitted provided that due credit is given to the author and the |
Ben Lindstrom | a238f6e | 2001-06-09 01:30:39 +0000 | [diff] [blame] | 7 | .\" OpenBSD project by leaving this copyright notice intact. |
Ben Lindstrom | 36579d3 | 2001-01-29 07:39:26 +0000 | [diff] [blame] | 8 | .\" |
djm@openbsd.org | 873d3e7 | 2017-04-30 23:18:44 +0000 | [diff] [blame] | 9 | .Dd $Mdocdate: April 30 2017 $ |
Ben Lindstrom | b22c2b8 | 2001-03-05 06:50:47 +0000 | [diff] [blame] | 10 | .Dt SSH-KEYSCAN 1 |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 11 | .Os |
| 12 | .Sh NAME |
| 13 | .Nm ssh-keyscan |
| 14 | .Nd gather ssh public keys |
| 15 | .Sh SYNOPSIS |
| 16 | .Nm ssh-keyscan |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 17 | .Bk -words |
jmc@openbsd.org | e72a857 | 2015-11-08 23:24:03 +0000 | [diff] [blame] | 18 | .Op Fl 46cHv |
Damien Miller | 9a2fdbd | 2005-03-02 12:04:01 +1100 | [diff] [blame] | 19 | .Op Fl f Ar file |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 20 | .Op Fl p Ar port |
| 21 | .Op Fl T Ar timeout |
| 22 | .Op Fl t Ar type |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 23 | .Op Ar host | addrlist namelist |
Damien Miller | c1719f7 | 2008-11-03 19:27:07 +1100 | [diff] [blame] | 24 | .Ar ... |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 25 | .Ek |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 26 | .Sh DESCRIPTION |
| 27 | .Nm |
| 28 | is a utility for gathering the public ssh host keys of a number of |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 29 | hosts. |
| 30 | It was designed to aid in building and verifying |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 31 | .Pa ssh_known_hosts |
| 32 | files. |
| 33 | .Nm |
| 34 | provides a minimal interface suitable for use by shell and perl |
| 35 | scripts. |
| 36 | .Pp |
| 37 | .Nm |
| 38 | uses non-blocking socket I/O to contact as many hosts as possible in |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 39 | parallel, so it is very efficient. |
| 40 | The keys from a domain of 1,000 |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 41 | hosts can be collected in tens of seconds, even when some of those |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 42 | hosts are down or do not run ssh. |
| 43 | For scanning, one does not need |
Ben Lindstrom | 594e203 | 2001-09-12 18:35:30 +0000 | [diff] [blame] | 44 | login access to the machines that are being scanned, nor does the |
| 45 | scanning process involve any encryption. |
Ben Lindstrom | 0b5afb9 | 2001-08-06 22:01:29 +0000 | [diff] [blame] | 46 | .Pp |
| 47 | The options are as follows: |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 48 | .Bl -tag -width Ds |
Damien Miller | 9a2fdbd | 2005-03-02 12:04:01 +1100 | [diff] [blame] | 49 | .It Fl 4 |
| 50 | Forces |
| 51 | .Nm |
| 52 | to use IPv4 addresses only. |
| 53 | .It Fl 6 |
| 54 | Forces |
| 55 | .Nm |
| 56 | to use IPv6 addresses only. |
djm@openbsd.org | 3a424cd | 2015-11-08 22:30:20 +0000 | [diff] [blame] | 57 | .It Fl c |
| 58 | Request certificates from target hosts instead of plain keys. |
Damien Miller | 9a2fdbd | 2005-03-02 12:04:01 +1100 | [diff] [blame] | 59 | .It Fl f Ar file |
| 60 | Read hosts or |
Damien Miller | f8f35bc | 2014-02-04 11:09:12 +1100 | [diff] [blame] | 61 | .Dq addrlist namelist |
| 62 | pairs from |
| 63 | .Ar file , |
| 64 | one per line. |
Damien Miller | 9a2fdbd | 2005-03-02 12:04:01 +1100 | [diff] [blame] | 65 | If |
| 66 | .Pa - |
| 67 | is supplied instead of a filename, |
| 68 | .Nm |
| 69 | will read hosts or |
Damien Miller | f8f35bc | 2014-02-04 11:09:12 +1100 | [diff] [blame] | 70 | .Dq addrlist namelist |
Damien Miller | 9a2fdbd | 2005-03-02 12:04:01 +1100 | [diff] [blame] | 71 | pairs from the standard input. |
Damien Miller | db7b817 | 2005-03-01 21:48:03 +1100 | [diff] [blame] | 72 | .It Fl H |
| 73 | Hash all hostnames and addresses in the output. |
| 74 | Hashed names may be used normally by |
| 75 | .Nm ssh |
| 76 | and |
| 77 | .Nm sshd , |
| 78 | but they do not reveal identifying information should the file's contents |
| 79 | be disclosed. |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 80 | .It Fl p Ar port |
| 81 | Port to connect to on the remote host. |
Ben Lindstrom | 8d066fb | 2001-09-12 17:06:13 +0000 | [diff] [blame] | 82 | .It Fl T Ar timeout |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 83 | Set the timeout for connection attempts. |
| 84 | If |
Damien Miller | f8f35bc | 2014-02-04 11:09:12 +1100 | [diff] [blame] | 85 | .Ar timeout |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 86 | seconds have elapsed since a connection was initiated to a host or since the |
| 87 | last time anything was read from that host, then the connection is |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 88 | closed and the host in question considered unavailable. |
| 89 | Default is 5 seconds. |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 90 | .It Fl t Ar type |
Ben Lindstrom | 8d066fb | 2001-09-12 17:06:13 +0000 | [diff] [blame] | 91 | Specifies the type of the key to fetch from the scanned hosts. |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 92 | The possible values are |
| 93 | .Dq rsa1 |
| 94 | for protocol version 1 and |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 95 | .Dq dsa , |
Damien Miller | 8ba0ead | 2013-12-18 17:46:27 +1100 | [diff] [blame] | 96 | .Dq ecdsa , |
| 97 | .Dq ed25519 , |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 98 | or |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 99 | .Dq rsa |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 100 | for protocol version 2. |
| 101 | Multiple values may be specified by separating them with commas. |
Damien Miller | 839f743 | 2012-04-22 11:24:21 +1000 | [diff] [blame] | 102 | The default is to fetch |
Damien Miller | 94bfe0f | 2014-04-20 13:00:51 +1000 | [diff] [blame] | 103 | .Dq rsa , |
| 104 | .Dq ecdsa , |
Damien Miller | 839f743 | 2012-04-22 11:24:21 +1000 | [diff] [blame] | 105 | and |
Damien Miller | 94bfe0f | 2014-04-20 13:00:51 +1000 | [diff] [blame] | 106 | .Dq ed25519 |
Damien Miller | 839f743 | 2012-04-22 11:24:21 +1000 | [diff] [blame] | 107 | keys. |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 108 | .It Fl v |
| 109 | Verbose mode. |
| 110 | Causes |
| 111 | .Nm |
| 112 | to print debugging messages about its progress. |
Ben Lindstrom | d26dcf3 | 2001-01-06 15:18:16 +0000 | [diff] [blame] | 113 | .El |
Ben Lindstrom | 0b5afb9 | 2001-08-06 22:01:29 +0000 | [diff] [blame] | 114 | .Sh SECURITY |
Darren Tucker | ffe88e1 | 2006-10-18 07:53:06 +1000 | [diff] [blame] | 115 | If an ssh_known_hosts file is constructed using |
Ben Lindstrom | 0b5afb9 | 2001-08-06 22:01:29 +0000 | [diff] [blame] | 116 | .Nm |
Ben Lindstrom | 594e203 | 2001-09-12 18:35:30 +0000 | [diff] [blame] | 117 | without verifying the keys, users will be vulnerable to |
Darren Tucker | 3ca4508 | 2004-07-17 16:13:15 +1000 | [diff] [blame] | 118 | .Em man in the middle |
Ben Lindstrom | 0b5afb9 | 2001-08-06 22:01:29 +0000 | [diff] [blame] | 119 | attacks. |
Ben Lindstrom | 594e203 | 2001-09-12 18:35:30 +0000 | [diff] [blame] | 120 | On the other hand, if the security model allows such a risk, |
Ben Lindstrom | 0b5afb9 | 2001-08-06 22:01:29 +0000 | [diff] [blame] | 121 | .Nm |
Ben Lindstrom | 594e203 | 2001-09-12 18:35:30 +0000 | [diff] [blame] | 122 | can help in the detection of tampered keyfiles or man in the middle |
| 123 | attacks which have begun after the ssh_known_hosts file was created. |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 124 | .Sh FILES |
Damien Miller | f8f35bc | 2014-02-04 11:09:12 +1100 | [diff] [blame] | 125 | Input format: |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 126 | .Bd -literal |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 127 | 1.2.3.4,1.2.4.4 name.my.domain,name,n.my.domain,n,1.2.3.4,1.2.4.4 |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 128 | .Ed |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 129 | .Pp |
sobrado@openbsd.org | f70b22b | 2014-08-30 15:33:50 +0000 | [diff] [blame] | 130 | Output format for RSA, DSA, ECDSA, and Ed25519 keys: |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 131 | .Bd -literal |
| 132 | host-or-namelist keytype base64-encoded-key |
| 133 | .Ed |
| 134 | .Pp |
| 135 | Where |
Damien Miller | f8f35bc | 2014-02-04 11:09:12 +1100 | [diff] [blame] | 136 | .Ar keytype |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 137 | is either |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 138 | .Dq ecdsa-sha2-nistp256 , |
| 139 | .Dq ecdsa-sha2-nistp384 , |
| 140 | .Dq ecdsa-sha2-nistp521 , |
Damien Miller | 5be9d9e | 2013-12-07 11:24:01 +1100 | [diff] [blame] | 141 | .Dq ssh-ed25519 , |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 142 | .Dq ssh-dss |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 143 | or |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 144 | .Dq ssh-rsa . |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 145 | .Pp |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 146 | .Pa /etc/ssh/ssh_known_hosts |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 147 | .Sh EXAMPLES |
Damien Miller | f8f35bc | 2014-02-04 11:09:12 +1100 | [diff] [blame] | 148 | Print the rsa host key for machine |
| 149 | .Ar hostname : |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 150 | .Bd -literal |
| 151 | $ ssh-keyscan hostname |
| 152 | .Ed |
| 153 | .Pp |
| 154 | Find all hosts from the file |
| 155 | .Pa ssh_hosts |
| 156 | which have new or different keys from those in the sorted file |
| 157 | .Pa ssh_known_hosts : |
| 158 | .Bd -literal |
Damien Miller | 94bfe0f | 2014-04-20 13:00:51 +1000 | [diff] [blame] | 159 | $ ssh-keyscan -t rsa,dsa,ecdsa,ed25519 -f ssh_hosts | \e |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 160 | sort -u - ssh_known_hosts | diff ssh_known_hosts - |
| 161 | .Ed |
| 162 | .Sh SEE ALSO |
| 163 | .Xr ssh 1 , |
| 164 | .Xr sshd 8 |
| 165 | .Sh AUTHORS |
Darren Tucker | 28e8e59 | 2005-10-03 18:20:28 +1000 | [diff] [blame] | 166 | .An -nosplit |
Damien Miller | bf836e5 | 2013-07-18 16:14:13 +1000 | [diff] [blame] | 167 | .An David Mazieres Aq Mt dm@lcs.mit.edu |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 168 | wrote the initial version, and |
Damien Miller | bf836e5 | 2013-07-18 16:14:13 +1000 | [diff] [blame] | 169 | .An Wayne Davison Aq Mt wayned@users.sourceforge.net |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 170 | added support for protocol version 2. |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 171 | .Sh BUGS |
| 172 | It generates "Connection closed by remote host" messages on the consoles |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 173 | of all the machines it scans if the server is older than version 2.9. |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 174 | This is because it opens a connection to the ssh port, reads the public |
| 175 | key, and drops the connection as soon as it gets the key. |