jmc@openbsd.org | 0bcd871 | 2018-03-05 07:03:18 +0000 | [diff] [blame] | 1 | .\" $OpenBSD: ssh-keyscan.1,v 1.44 2018/03/05 07:03:18 jmc 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 | .\" |
jmc@openbsd.org | 0bcd871 | 2018-03-05 07:03:18 +0000 | [diff] [blame] | 9 | .Dd $Mdocdate: March 5 2018 $ |
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 |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 14 | .Nd gather SSH public keys |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 15 | .Sh SYNOPSIS |
| 16 | .Nm ssh-keyscan |
djm@openbsd.org | 1a34835 | 2018-02-23 05:14:05 +0000 | [diff] [blame] | 17 | .Op Fl 46cDHv |
Damien Miller | 9a2fdbd | 2005-03-02 12:04:01 +1100 | [diff] [blame] | 18 | .Op Fl f Ar file |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 19 | .Op Fl p Ar port |
| 20 | .Op Fl T Ar timeout |
| 21 | .Op Fl t Ar type |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 22 | .Op Ar host | addrlist namelist |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 23 | .Sh DESCRIPTION |
| 24 | .Nm |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 25 | 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] | 26 | hosts. |
| 27 | It was designed to aid in building and verifying |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 28 | .Pa ssh_known_hosts |
jmc@openbsd.org | 0bcd871 | 2018-03-05 07:03:18 +0000 | [diff] [blame] | 29 | files, |
| 30 | the format of which is documented in |
| 31 | .Xr sshd 8 . |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 32 | .Nm |
| 33 | provides a minimal interface suitable for use by shell and perl |
| 34 | scripts. |
| 35 | .Pp |
| 36 | .Nm |
| 37 | 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] | 38 | parallel, so it is very efficient. |
| 39 | The keys from a domain of 1,000 |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 40 | hosts can be collected in tens of seconds, even when some of those |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 41 | hosts are down or do not run |
| 42 | .Xr sshd 8 . |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 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 |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 50 | Force |
Damien Miller | 9a2fdbd | 2005-03-02 12:04:01 +1100 | [diff] [blame] | 51 | .Nm |
| 52 | to use IPv4 addresses only. |
| 53 | .It Fl 6 |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 54 | Force |
Damien Miller | 9a2fdbd | 2005-03-02 12:04:01 +1100 | [diff] [blame] | 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. |
djm@openbsd.org | 1a34835 | 2018-02-23 05:14:05 +0000 | [diff] [blame] | 59 | .It Fl D |
| 60 | Print keys found as SSHFP DNS records. |
| 61 | The default is to print keys in a format usable as a |
| 62 | .Xr ssh 1 |
| 63 | .Pa known_hosts |
| 64 | file. |
Damien Miller | 9a2fdbd | 2005-03-02 12:04:01 +1100 | [diff] [blame] | 65 | .It Fl f Ar file |
| 66 | Read hosts or |
Damien Miller | f8f35bc | 2014-02-04 11:09:12 +1100 | [diff] [blame] | 67 | .Dq addrlist namelist |
| 68 | pairs from |
| 69 | .Ar file , |
| 70 | one per line. |
Damien Miller | 9a2fdbd | 2005-03-02 12:04:01 +1100 | [diff] [blame] | 71 | If |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 72 | .Sq - |
Damien Miller | 9a2fdbd | 2005-03-02 12:04:01 +1100 | [diff] [blame] | 73 | is supplied instead of a filename, |
| 74 | .Nm |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 75 | will read from the standard input. |
jmc@openbsd.org | 0bcd871 | 2018-03-05 07:03:18 +0000 | [diff] [blame] | 76 | Input is expected in the format: |
| 77 | .Bd -literal |
| 78 | 1.2.3.4,1.2.4.4 name.my.domain,name,n.my.domain,n,1.2.3.4,1.2.4.4 |
| 79 | .Ed |
Damien Miller | db7b817 | 2005-03-01 21:48:03 +1100 | [diff] [blame] | 80 | .It Fl H |
| 81 | Hash all hostnames and addresses in the output. |
| 82 | Hashed names may be used normally by |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 83 | .Xr ssh 1 |
Damien Miller | db7b817 | 2005-03-01 21:48:03 +1100 | [diff] [blame] | 84 | and |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 85 | .Xr sshd 8 , |
Damien Miller | db7b817 | 2005-03-01 21:48:03 +1100 | [diff] [blame] | 86 | but they do not reveal identifying information should the file's contents |
| 87 | be disclosed. |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 88 | .It Fl p Ar port |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 89 | Connect to |
| 90 | .Ar port |
| 91 | on the remote host. |
Ben Lindstrom | 8d066fb | 2001-09-12 17:06:13 +0000 | [diff] [blame] | 92 | .It Fl T Ar timeout |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 93 | Set the timeout for connection attempts. |
| 94 | If |
Damien Miller | f8f35bc | 2014-02-04 11:09:12 +1100 | [diff] [blame] | 95 | .Ar timeout |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 96 | seconds have elapsed since a connection was initiated to a host or since the |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 97 | last time anything was read from that host, the connection is |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 98 | closed and the host in question considered unavailable. |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 99 | The default is 5 seconds. |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 100 | .It Fl t Ar type |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 101 | Specify the type of the key to fetch from the scanned hosts. |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 102 | The possible values are |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 103 | .Dq dsa , |
Damien Miller | 8ba0ead | 2013-12-18 17:46:27 +1100 | [diff] [blame] | 104 | .Dq ecdsa , |
| 105 | .Dq ed25519 , |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 106 | or |
jmc@openbsd.org | f10c0d3 | 2017-05-02 17:04:09 +0000 | [diff] [blame] | 107 | .Dq rsa . |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 108 | Multiple values may be specified by separating them with commas. |
Damien Miller | 839f743 | 2012-04-22 11:24:21 +1000 | [diff] [blame] | 109 | The default is to fetch |
Damien Miller | 94bfe0f | 2014-04-20 13:00:51 +1000 | [diff] [blame] | 110 | .Dq rsa , |
| 111 | .Dq ecdsa , |
Damien Miller | 839f743 | 2012-04-22 11:24:21 +1000 | [diff] [blame] | 112 | and |
Damien Miller | 94bfe0f | 2014-04-20 13:00:51 +1000 | [diff] [blame] | 113 | .Dq ed25519 |
Damien Miller | 839f743 | 2012-04-22 11:24:21 +1000 | [diff] [blame] | 114 | keys. |
Ben Lindstrom | 325e70c | 2001-08-06 22:41:30 +0000 | [diff] [blame] | 115 | .It Fl v |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 116 | Verbose mode: |
| 117 | print debugging messages about progress. |
Ben Lindstrom | d26dcf3 | 2001-01-06 15:18:16 +0000 | [diff] [blame] | 118 | .El |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 119 | .Pp |
Darren Tucker | ffe88e1 | 2006-10-18 07:53:06 +1000 | [diff] [blame] | 120 | If an ssh_known_hosts file is constructed using |
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 | without verifying the keys, users will be vulnerable to |
Darren Tucker | 3ca4508 | 2004-07-17 16:13:15 +1000 | [diff] [blame] | 123 | .Em man in the middle |
Ben Lindstrom | 0b5afb9 | 2001-08-06 22:01:29 +0000 | [diff] [blame] | 124 | attacks. |
Ben Lindstrom | 594e203 | 2001-09-12 18:35:30 +0000 | [diff] [blame] | 125 | On the other hand, if the security model allows such a risk, |
Ben Lindstrom | 0b5afb9 | 2001-08-06 22:01:29 +0000 | [diff] [blame] | 126 | .Nm |
Ben Lindstrom | 594e203 | 2001-09-12 18:35:30 +0000 | [diff] [blame] | 127 | can help in the detection of tampered keyfiles or man in the middle |
| 128 | attacks which have begun after the ssh_known_hosts file was created. |
Ben Lindstrom | b6434ae | 2000-12-05 01:15:09 +0000 | [diff] [blame] | 129 | .Sh FILES |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 130 | .Pa /etc/ssh/ssh_known_hosts |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 131 | .Sh EXAMPLES |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 132 | Print the RSA host key for machine |
Damien Miller | f8f35bc | 2014-02-04 11:09:12 +1100 | [diff] [blame] | 133 | .Ar hostname : |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 134 | .Pp |
| 135 | .Dl $ ssh-keyscan -t rsa hostname |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 136 | .Pp |
| 137 | Find all hosts from the file |
| 138 | .Pa ssh_hosts |
| 139 | which have new or different keys from those in the sorted file |
| 140 | .Pa ssh_known_hosts : |
jmc@openbsd.org | f493d2b | 2018-03-02 21:40:15 +0000 | [diff] [blame] | 141 | .Bd -literal -offset indent |
Damien Miller | 94bfe0f | 2014-04-20 13:00:51 +1000 | [diff] [blame] | 142 | $ ssh-keyscan -t rsa,dsa,ecdsa,ed25519 -f ssh_hosts | \e |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 143 | sort -u - ssh_known_hosts | diff ssh_known_hosts - |
| 144 | .Ed |
| 145 | .Sh SEE ALSO |
| 146 | .Xr ssh 1 , |
| 147 | .Xr sshd 8 |
jmc@openbsd.org | 7d330a1 | 2018-02-23 07:38:09 +0000 | [diff] [blame] | 148 | .Rs |
djm@openbsd.org | 1a34835 | 2018-02-23 05:14:05 +0000 | [diff] [blame] | 149 | .%D 2006 |
jmc@openbsd.org | 7d330a1 | 2018-02-23 07:38:09 +0000 | [diff] [blame] | 150 | .%R RFC 4255 |
| 151 | .%T Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints |
djm@openbsd.org | 1a34835 | 2018-02-23 05:14:05 +0000 | [diff] [blame] | 152 | .Re |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 153 | .Sh AUTHORS |
Darren Tucker | 28e8e59 | 2005-10-03 18:20:28 +1000 | [diff] [blame] | 154 | .An -nosplit |
Damien Miller | bf836e5 | 2013-07-18 16:14:13 +1000 | [diff] [blame] | 155 | .An David Mazieres Aq Mt dm@lcs.mit.edu |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 156 | wrote the initial version, and |
Damien Miller | bf836e5 | 2013-07-18 16:14:13 +1000 | [diff] [blame] | 157 | .An Wayne Davison Aq Mt wayned@users.sourceforge.net |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 158 | added support for protocol version 2. |