Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1 | .\" -*- nroff -*- |
| 2 | .\" |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 3 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 4 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
| 5 | .\" All rights reserved |
| 6 | .\" |
Damien Miller | e4340be | 2000-09-16 13:29:08 +1100 | [diff] [blame] | 7 | .\" As far as I am concerned, the code I have written for this software |
| 8 | .\" can be used freely for any purpose. Any derived versions of this |
| 9 | .\" software must be clearly marked as such, and if the derived work is |
| 10 | .\" incompatible with the protocol description in the RFC file, it must be |
| 11 | .\" called by a name other than "ssh" or "Secure Shell". |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 12 | .\" |
Ben Lindstrom | 92a2e38 | 2001-03-05 06:59:27 +0000 | [diff] [blame] | 13 | .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. |
| 14 | .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. |
| 15 | .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. |
Damien Miller | e4340be | 2000-09-16 13:29:08 +1100 | [diff] [blame] | 16 | .\" |
| 17 | .\" Redistribution and use in source and binary forms, with or without |
| 18 | .\" modification, are permitted provided that the following conditions |
| 19 | .\" are met: |
| 20 | .\" 1. Redistributions of source code must retain the above copyright |
| 21 | .\" notice, this list of conditions and the following disclaimer. |
| 22 | .\" 2. Redistributions in binary form must reproduce the above copyright |
| 23 | .\" notice, this list of conditions and the following disclaimer in the |
| 24 | .\" documentation and/or other materials provided with the distribution. |
| 25 | .\" |
| 26 | .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| 27 | .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| 28 | .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| 29 | .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| 30 | .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| 31 | .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 32 | .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 33 | .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 34 | .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| 35 | .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 36 | .\" |
Damien Miller | bcfbc48 | 2010-07-16 13:59:11 +1000 | [diff] [blame] | 37 | .\" $OpenBSD: ssh.1,v 1.306 2010/07/14 17:06:58 jmc Exp $ |
| 38 | .Dd $Mdocdate: July 14 2010 $ |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 39 | .Dt SSH 1 |
| 40 | .Os |
| 41 | .Sh NAME |
| 42 | .Nm ssh |
Ben Lindstrom | d58eb5f | 2001-03-07 06:07:22 +0000 | [diff] [blame] | 43 | .Nd OpenSSH SSH client (remote login program) |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 44 | .Sh SYNOPSIS |
| 45 | .Nm ssh |
Damien Miller | bcfbc48 | 2010-07-16 13:59:11 +1000 | [diff] [blame] | 46 | .Bk -words |
Damien Miller | e272a5b | 2008-11-03 19:22:37 +1100 | [diff] [blame] | 47 | .Op Fl 1246AaCfgKkMNnqsTtVvXxYy |
Ben Lindstrom | e0f8804 | 2001-04-30 13:06:24 +0000 | [diff] [blame] | 48 | .Op Fl b Ar bind_address |
Damien Miller | 30c3d42 | 2000-05-09 11:02:59 +1000 | [diff] [blame] | 49 | .Op Fl c Ar cipher_spec |
Damien Miller | bcfbc48 | 2010-07-16 13:59:11 +1000 | [diff] [blame] | 50 | .Op Fl D Oo Ar bind_address : Oc Ns Ar port |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 51 | .Op Fl e Ar escape_char |
Ben Lindstrom | 14f31ab | 2001-09-12 17:48:04 +0000 | [diff] [blame] | 52 | .Op Fl F Ar configfile |
Damien Miller | 048dc93 | 2010-02-12 09:22:04 +1100 | [diff] [blame] | 53 | .Op Fl I Ar pkcs11 |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 54 | .Op Fl i Ar identity_file |
Damien Miller | bcfbc48 | 2010-07-16 13:59:11 +1000 | [diff] [blame] | 55 | .Op Fl L Oo Ar bind_address : Oc Ns Ar port : Ns Ar host : Ns Ar hostport |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 56 | .Op Fl l Ar login_name |
| 57 | .Op Fl m Ar mac_spec |
Darren Tucker | 7ebfc10 | 2004-11-07 20:06:19 +1100 | [diff] [blame] | 58 | .Op Fl O Ar ctl_cmd |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 59 | .Op Fl o Ar option |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 60 | .Op Fl p Ar port |
Damien Miller | bcfbc48 | 2010-07-16 13:59:11 +1000 | [diff] [blame] | 61 | .Op Fl R Oo Ar bind_address : Oc Ns Ar port : Ns Ar host : Ns Ar hostport |
Darren Tucker | 7ebfc10 | 2004-11-07 20:06:19 +1100 | [diff] [blame] | 62 | .Op Fl S Ar ctl_path |
Darren Tucker | 7ad8dd2 | 2010-01-12 19:40:27 +1100 | [diff] [blame] | 63 | .Op Fl W Ar host : Ns Ar port |
Damien Miller | bcfbc48 | 2010-07-16 13:59:11 +1000 | [diff] [blame] | 64 | .Op Fl w Ar local_tun Ns Op : Ns Ar remote_tun |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 65 | .Oo Ar user Ns @ Oc Ns Ar hostname |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 66 | .Op Ar command |
Damien Miller | bcfbc48 | 2010-07-16 13:59:11 +1000 | [diff] [blame] | 67 | .Ek |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 68 | .Sh DESCRIPTION |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 69 | .Nm |
Ben Lindstrom | d58eb5f | 2001-03-07 06:07:22 +0000 | [diff] [blame] | 70 | (SSH client) is a program for logging into a remote machine and for |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 71 | executing commands on a remote machine. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 72 | It is intended to replace rlogin and rsh, |
| 73 | and provide secure encrypted communications between |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 74 | two untrusted hosts over an insecure network. |
Damien Miller | 8bfaf93 | 2006-01-14 10:09:30 +1100 | [diff] [blame] | 75 | X11 connections and arbitrary TCP ports |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 76 | can also be forwarded over the secure channel. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 77 | .Pp |
| 78 | .Nm |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 79 | connects and logs into the specified |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 80 | .Ar hostname |
| 81 | (with optional |
| 82 | .Ar user |
| 83 | name). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 84 | The user must prove |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 85 | his/her identity to the remote machine using one of several methods |
Darren Tucker | 5434cfe | 2005-12-20 16:11:35 +1100 | [diff] [blame] | 86 | depending on the protocol version used (see below). |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 87 | .Pp |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 88 | If |
| 89 | .Ar command |
| 90 | is specified, |
Darren Tucker | b18c867 | 2005-12-20 16:10:09 +1100 | [diff] [blame] | 91 | it is executed on the remote host instead of a login shell. |
Darren Tucker | 0b42e6d | 2004-08-13 21:22:40 +1000 | [diff] [blame] | 92 | .Pp |
Damien Miller | 0bc1bd8 | 2000-11-13 22:57:25 +1100 | [diff] [blame] | 93 | The options are as follows: |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 94 | .Bl -tag -width Ds |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 95 | .It Fl 1 |
| 96 | Forces |
| 97 | .Nm |
| 98 | to try protocol version 1 only. |
| 99 | .It Fl 2 |
| 100 | Forces |
| 101 | .Nm |
| 102 | to try protocol version 2 only. |
| 103 | .It Fl 4 |
| 104 | Forces |
| 105 | .Nm |
| 106 | to use IPv4 addresses only. |
| 107 | .It Fl 6 |
| 108 | Forces |
| 109 | .Nm |
| 110 | to use IPv6 addresses only. |
Damien Miller | b1715dc | 2000-05-30 13:44:51 +1000 | [diff] [blame] | 111 | .It Fl A |
| 112 | Enables forwarding of the authentication agent connection. |
| 113 | This can also be specified on a per-host basis in a configuration file. |
Damien Miller | b5fdfaa | 2002-09-12 09:52:03 +1000 | [diff] [blame] | 114 | .Pp |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 115 | Agent forwarding should be enabled with caution. |
| 116 | Users with the ability to bypass file permissions on the remote host |
Darren Tucker | ae69e1d | 2009-10-24 11:41:34 +1100 | [diff] [blame] | 117 | (for the agent's |
Darren Tucker | 98c9aec | 2009-10-24 11:42:44 +1100 | [diff] [blame] | 118 | .Ux Ns -domain |
| 119 | socket) can access the local agent through the forwarded connection. |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 120 | An attacker cannot obtain key material from the agent, |
Damien Miller | b5fdfaa | 2002-09-12 09:52:03 +1000 | [diff] [blame] | 121 | however they can perform operations on the keys that enable them to |
| 122 | authenticate using the identities loaded into the agent. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 123 | .It Fl a |
| 124 | Disables forwarding of the authentication agent connection. |
Ben Lindstrom | e0f8804 | 2001-04-30 13:06:24 +0000 | [diff] [blame] | 125 | .It Fl b Ar bind_address |
Darren Tucker | a5cf855 | 2005-07-14 17:04:18 +1000 | [diff] [blame] | 126 | Use |
| 127 | .Ar bind_address |
| 128 | on the local machine as the source address |
| 129 | of the connection. |
| 130 | Only useful on systems with more than one address. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 131 | .It Fl C |
| 132 | Requests compression of all data (including stdin, stdout, stderr, and |
Damien Miller | 8bfaf93 | 2006-01-14 10:09:30 +1100 | [diff] [blame] | 133 | data for forwarded X11 and TCP connections). |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 134 | The compression algorithm is the same used by |
| 135 | .Xr gzip 1 , |
| 136 | and the |
| 137 | .Dq level |
| 138 | can be controlled by the |
| 139 | .Cm CompressionLevel |
| 140 | option for protocol version 1. |
| 141 | Compression is desirable on modem lines and other |
| 142 | slow connections, but will only slow down things on fast networks. |
| 143 | The default value can be set on a host-by-host basis in the |
| 144 | configuration files; see the |
| 145 | .Cm Compression |
| 146 | option. |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 147 | .It Fl c Ar cipher_spec |
| 148 | Selects the cipher specification for encrypting the session. |
| 149 | .Pp |
| 150 | Protocol version 1 allows specification of a single cipher. |
Darren Tucker | 1e4308e | 2005-10-03 18:18:40 +1000 | [diff] [blame] | 151 | The supported values are |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 152 | .Dq 3des , |
Darren Tucker | ff9f484 | 2005-12-20 16:10:45 +1100 | [diff] [blame] | 153 | .Dq blowfish , |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 154 | and |
| 155 | .Dq des . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 156 | .Ar 3des |
| 157 | (triple-des) is an encrypt-decrypt-encrypt triple with three different keys. |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 158 | It is believed to be secure. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 159 | .Ar blowfish |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 160 | is a fast block cipher; it appears very secure and is much faster than |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 161 | .Ar 3des . |
Ben Lindstrom | ffa1dd6 | 2001-09-12 16:52:28 +0000 | [diff] [blame] | 162 | .Ar des |
| 163 | is only supported in the |
| 164 | .Nm |
| 165 | client for interoperability with legacy protocol 1 implementations |
| 166 | that do not support the |
| 167 | .Ar 3des |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 168 | cipher. |
| 169 | Its use is strongly discouraged due to cryptographic weaknesses. |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 170 | The default is |
| 171 | .Dq 3des . |
| 172 | .Pp |
Damien Miller | 3597821 | 2005-12-24 14:56:47 +1100 | [diff] [blame] | 173 | For protocol version 2, |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 174 | .Ar cipher_spec |
| 175 | is a comma-separated list of ciphers |
| 176 | listed in order of preference. |
Darren Tucker | 3a6a51f | 2009-06-21 17:48:52 +1000 | [diff] [blame] | 177 | See the |
| 178 | .Cm Ciphers |
| 179 | keyword for more information. |
Darren Tucker | c8d6421 | 2005-10-03 18:13:42 +1000 | [diff] [blame] | 180 | .It Fl D Xo |
| 181 | .Sm off |
| 182 | .Oo Ar bind_address : Oc |
| 183 | .Ar port |
| 184 | .Sm on |
| 185 | .Xc |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 186 | Specifies a local |
| 187 | .Dq dynamic |
| 188 | application-level port forwarding. |
| 189 | This works by allocating a socket to listen to |
| 190 | .Ar port |
Darren Tucker | c8d6421 | 2005-10-03 18:13:42 +1000 | [diff] [blame] | 191 | on the local side, optionally bound to the specified |
| 192 | .Ar bind_address . |
| 193 | Whenever a connection is made to this port, the |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 194 | connection is forwarded over the secure channel, and the application |
| 195 | protocol is then used to determine where to connect to from the |
| 196 | remote machine. |
| 197 | Currently the SOCKS4 and SOCKS5 protocols are supported, and |
| 198 | .Nm |
| 199 | will act as a SOCKS server. |
| 200 | Only root can forward privileged ports. |
| 201 | Dynamic port forwardings can also be specified in the configuration file. |
Darren Tucker | c8d6421 | 2005-10-03 18:13:42 +1000 | [diff] [blame] | 202 | .Pp |
| 203 | IPv6 addresses can be specified with an alternative syntax: |
| 204 | .Sm off |
| 205 | .Xo |
| 206 | .Op Ar bind_address No / |
| 207 | .Ar port |
| 208 | .Xc |
| 209 | .Sm on |
| 210 | or by enclosing the address in square brackets. |
| 211 | Only the superuser can forward privileged ports. |
| 212 | By default, the local port is bound in accordance with the |
| 213 | .Cm GatewayPorts |
| 214 | setting. |
| 215 | However, an explicit |
| 216 | .Ar bind_address |
| 217 | may be used to bind the connection to a specific address. |
| 218 | The |
| 219 | .Ar bind_address |
| 220 | of |
| 221 | .Dq localhost |
| 222 | indicates that the listening port be bound for local use only, while an |
| 223 | empty address or |
| 224 | .Sq * |
| 225 | indicates that the port should be available from all interfaces. |
Damien Miller | 2142ba0 | 2005-12-24 14:56:29 +1100 | [diff] [blame] | 226 | .It Fl e Ar escape_char |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 227 | Sets the escape character for sessions with a pty (default: |
| 228 | .Ql ~ ) . |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 229 | The escape character is only recognized at the beginning of a line. |
| 230 | The escape character followed by a dot |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 231 | .Pq Ql \&. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 232 | closes the connection; |
| 233 | followed by control-Z suspends the connection; |
| 234 | and followed by itself sends the escape character once. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 235 | Setting the character to |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 236 | .Dq none |
| 237 | disables any escapes and makes the session fully transparent. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 238 | .It Fl F Ar configfile |
| 239 | Specifies an alternative per-user configuration file. |
| 240 | If a configuration file is given on the command line, |
| 241 | the system-wide configuration file |
| 242 | .Pq Pa /etc/ssh/ssh_config |
| 243 | will be ignored. |
| 244 | The default for the per-user configuration file is |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 245 | .Pa ~/.ssh/config . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 246 | .It Fl f |
| 247 | Requests |
| 248 | .Nm |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 249 | to go to background just before command execution. |
| 250 | This is useful if |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 251 | .Nm |
| 252 | is going to ask for passwords or passphrases, but the user |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 253 | wants it in the background. |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 254 | This implies |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 255 | .Fl n . |
| 256 | The recommended way to start X11 programs at a remote site is with |
| 257 | something like |
| 258 | .Ic ssh -f host xterm . |
Darren Tucker | 9a2a609 | 2008-07-04 12:53:50 +1000 | [diff] [blame] | 259 | .Pp |
| 260 | If the |
| 261 | .Cm ExitOnForwardFailure |
| 262 | configuration option is set to |
| 263 | .Dq yes , |
| 264 | then a client started with |
| 265 | .Fl f |
| 266 | will wait for all remote port forwards to be successfully established |
| 267 | before placing itself in the background. |
Damien Miller | 396691a | 2000-01-20 22:44:08 +1100 | [diff] [blame] | 268 | .It Fl g |
| 269 | Allows remote hosts to connect to local forwarded ports. |
Damien Miller | 7ea845e | 2010-02-12 09:21:02 +1100 | [diff] [blame] | 270 | .It Fl I Ar pkcs11 |
Damien Miller | d400da5 | 2010-02-12 09:26:23 +1100 | [diff] [blame] | 271 | Specify the PKCS#11 shared library |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 272 | .Nm |
Damien Miller | a761844 | 2010-02-12 09:26:02 +1100 | [diff] [blame] | 273 | should use to communicate with a PKCS#11 token providing the user's |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 274 | private RSA key. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 275 | .It Fl i Ar identity_file |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 276 | Selects a file from which the identity (private key) for |
Damien Miller | 0bc1bd8 | 2000-11-13 22:57:25 +1100 | [diff] [blame] | 277 | RSA or DSA authentication is read. |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 278 | The default is |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 279 | .Pa ~/.ssh/identity |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 280 | for protocol version 1, and |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 281 | .Pa ~/.ssh/id_rsa |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 282 | and |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 283 | .Pa ~/.ssh/id_dsa |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 284 | for protocol version 2. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 285 | Identity files may also be specified on |
| 286 | a per-host basis in the configuration file. |
| 287 | It is possible to have multiple |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 288 | .Fl i |
| 289 | options (and multiple identities specified in |
| 290 | configuration files). |
Damien Miller | 5059d8d | 2010-03-05 21:31:11 +1100 | [diff] [blame] | 291 | .Nm |
| 292 | will also try to load certificate information from the filename obtained |
| 293 | by appending |
| 294 | .Pa -cert.pub |
| 295 | to identity filenames. |
Darren Tucker | 415bddc | 2007-06-12 23:43:16 +1000 | [diff] [blame] | 296 | .It Fl K |
| 297 | Enables GSSAPI-based authentication and forwarding (delegation) of GSSAPI |
| 298 | credentials to the server. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 299 | .It Fl k |
Damien Miller | e0113cc | 2003-11-24 13:10:09 +1100 | [diff] [blame] | 300 | Disables forwarding (delegation) of GSSAPI credentials to the server. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 301 | .It Fl L Xo |
| 302 | .Sm off |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 303 | .Oo Ar bind_address : Oc |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 304 | .Ar port : host : hostport |
| 305 | .Sm on |
| 306 | .Xc |
| 307 | Specifies that the given port on the local (client) host is to be |
| 308 | forwarded to the given host and port on the remote side. |
| 309 | This works by allocating a socket to listen to |
| 310 | .Ar port |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 311 | on the local side, optionally bound to the specified |
| 312 | .Ar bind_address . |
| 313 | Whenever a connection is made to this port, the |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 314 | connection is forwarded over the secure channel, and a connection is |
| 315 | made to |
| 316 | .Ar host |
| 317 | port |
| 318 | .Ar hostport |
| 319 | from the remote machine. |
| 320 | Port forwardings can also be specified in the configuration file. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 321 | IPv6 addresses can be specified with an alternative syntax: |
| 322 | .Sm off |
| 323 | .Xo |
Damien Miller | b096ac4 | 2005-03-09 11:00:05 +1100 | [diff] [blame] | 324 | .Op Ar bind_address No / |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 325 | .Ar port No / Ar host No / |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 326 | .Ar hostport |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 327 | .Xc |
| 328 | .Sm on |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 329 | or by enclosing the address in square brackets. |
| 330 | Only the superuser can forward privileged ports. |
| 331 | By default, the local port is bound in accordance with the |
| 332 | .Cm GatewayPorts |
| 333 | setting. |
| 334 | However, an explicit |
| 335 | .Ar bind_address |
| 336 | may be used to bind the connection to a specific address. |
| 337 | The |
| 338 | .Ar bind_address |
| 339 | of |
| 340 | .Dq localhost |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 341 | indicates that the listening port be bound for local use only, while an |
| 342 | empty address or |
| 343 | .Sq * |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 344 | indicates that the port should be available from all interfaces. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 345 | .It Fl l Ar login_name |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 346 | Specifies the user to log in as on the remote machine. |
| 347 | This also may be specified on a per-host basis in the configuration file. |
Damien Miller | 0e220db | 2004-06-15 10:34:08 +1000 | [diff] [blame] | 348 | .It Fl M |
| 349 | Places the |
| 350 | .Nm |
| 351 | client into |
| 352 | .Dq master |
| 353 | mode for connection sharing. |
Damien Miller | 88b2552 | 2005-12-31 16:23:15 +1100 | [diff] [blame] | 354 | Multiple |
| 355 | .Fl M |
| 356 | options places |
| 357 | .Nm |
| 358 | into |
| 359 | .Dq master |
| 360 | mode with confirmation required before slave connections are accepted. |
Damien Miller | 0e220db | 2004-06-15 10:34:08 +1000 | [diff] [blame] | 361 | Refer to the description of |
| 362 | .Cm ControlMaster |
| 363 | in |
| 364 | .Xr ssh_config 5 |
| 365 | for details. |
Damien Miller | 5d1eceb | 2004-06-30 22:37:57 +1000 | [diff] [blame] | 366 | .It Fl m Ar mac_spec |
| 367 | Additionally, for protocol version 2 a comma-separated list of MAC |
| 368 | (message authentication code) algorithms can |
| 369 | be specified in order of preference. |
| 370 | See the |
| 371 | .Cm MACs |
| 372 | keyword for more information. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 373 | .It Fl N |
| 374 | Do not execute a remote command. |
| 375 | This is useful for just forwarding ports |
| 376 | (protocol version 2 only). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 377 | .It Fl n |
| 378 | Redirects stdin from |
| 379 | .Pa /dev/null |
| 380 | (actually, prevents reading from stdin). |
| 381 | This must be used when |
| 382 | .Nm |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 383 | is run in the background. |
| 384 | A common trick is to use this to run X11 programs on a remote machine. |
| 385 | For example, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 386 | .Ic ssh -n shadows.cs.hut.fi emacs & |
| 387 | will start an emacs on shadows.cs.hut.fi, and the X11 |
| 388 | connection will be automatically forwarded over an encrypted channel. |
| 389 | The |
| 390 | .Nm |
| 391 | program will be put in the background. |
| 392 | (This does not work if |
| 393 | .Nm |
| 394 | needs to ask for a password or passphrase; see also the |
| 395 | .Fl f |
| 396 | option.) |
Darren Tucker | e04644c | 2004-12-03 14:08:45 +1100 | [diff] [blame] | 397 | .It Fl O Ar ctl_cmd |
| 398 | Control an active connection multiplexing master process. |
| 399 | When the |
| 400 | .Fl O |
| 401 | option is specified, the |
| 402 | .Ar ctl_cmd |
| 403 | argument is interpreted and passed to the master process. |
| 404 | Valid commands are: |
| 405 | .Dq check |
Damien Miller | 388f6fc | 2010-05-21 14:57:35 +1000 | [diff] [blame] | 406 | (check that the master process is running), |
| 407 | .Dq forward |
| 408 | (request forwardings without command execution) and |
Darren Tucker | e04644c | 2004-12-03 14:08:45 +1100 | [diff] [blame] | 409 | .Dq exit |
| 410 | (request the master to exit). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 411 | .It Fl o Ar option |
Ben Lindstrom | 14c62eb | 2001-08-15 23:25:46 +0000 | [diff] [blame] | 412 | Can be used to give options in the format used in the configuration file. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 413 | This is useful for specifying options for which there is no separate |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 414 | command-line flag. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 415 | For full details of the options listed below, and their possible values, see |
| 416 | .Xr ssh_config 5 . |
| 417 | .Pp |
| 418 | .Bl -tag -width Ds -offset indent -compact |
| 419 | .It AddressFamily |
| 420 | .It BatchMode |
| 421 | .It BindAddress |
| 422 | .It ChallengeResponseAuthentication |
| 423 | .It CheckHostIP |
| 424 | .It Cipher |
| 425 | .It Ciphers |
| 426 | .It ClearAllForwardings |
| 427 | .It Compression |
| 428 | .It CompressionLevel |
| 429 | .It ConnectionAttempts |
Darren Tucker | edae0ec | 2004-05-02 22:15:52 +1000 | [diff] [blame] | 430 | .It ConnectTimeout |
Damien Miller | 0e220db | 2004-06-15 10:34:08 +1000 | [diff] [blame] | 431 | .It ControlMaster |
| 432 | .It ControlPath |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 433 | .It DynamicForward |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 434 | .It EscapeChar |
Darren Tucker | e7d4b19 | 2006-07-12 22:17:10 +1000 | [diff] [blame] | 435 | .It ExitOnForwardFailure |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 436 | .It ForwardAgent |
| 437 | .It ForwardX11 |
Darren Tucker | 0a118da | 2003-10-15 15:54:32 +1000 | [diff] [blame] | 438 | .It ForwardX11Trusted |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 439 | .It GatewayPorts |
| 440 | .It GlobalKnownHostsFile |
| 441 | .It GSSAPIAuthentication |
| 442 | .It GSSAPIDelegateCredentials |
Damien Miller | e177615 | 2005-03-01 21:47:37 +1100 | [diff] [blame] | 443 | .It HashKnownHosts |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 444 | .It Host |
| 445 | .It HostbasedAuthentication |
| 446 | .It HostKeyAlgorithms |
| 447 | .It HostKeyAlias |
| 448 | .It HostName |
| 449 | .It IdentityFile |
Damien Miller | bd394c3 | 2004-03-08 23:12:36 +1100 | [diff] [blame] | 450 | .It IdentitiesOnly |
Darren Tucker | 636ca90 | 2004-11-05 20:22:00 +1100 | [diff] [blame] | 451 | .It KbdInteractiveDevices |
Damien Miller | d27b947 | 2005-12-13 19:29:02 +1100 | [diff] [blame] | 452 | .It LocalCommand |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 453 | .It LocalForward |
| 454 | .It LogLevel |
| 455 | .It MACs |
| 456 | .It NoHostAuthenticationForLocalhost |
| 457 | .It NumberOfPasswordPrompts |
| 458 | .It PasswordAuthentication |
Damien Miller | d27b947 | 2005-12-13 19:29:02 +1100 | [diff] [blame] | 459 | .It PermitLocalCommand |
Damien Miller | 7ea845e | 2010-02-12 09:21:02 +1100 | [diff] [blame] | 460 | .It PKCS11Provider |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 461 | .It Port |
| 462 | .It PreferredAuthentications |
| 463 | .It Protocol |
| 464 | .It ProxyCommand |
| 465 | .It PubkeyAuthentication |
Darren Tucker | 62388b2 | 2006-01-20 11:31:47 +1100 | [diff] [blame] | 466 | .It RekeyLimit |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 467 | .It RemoteForward |
| 468 | .It RhostsRSAAuthentication |
| 469 | .It RSAAuthentication |
Darren Tucker | 7a6c066 | 2004-05-02 22:14:03 +1000 | [diff] [blame] | 470 | .It SendEnv |
Damien Miller | 509b010 | 2003-12-17 16:33:10 +1100 | [diff] [blame] | 471 | .It ServerAliveInterval |
| 472 | .It ServerAliveCountMax |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 473 | .It StrictHostKeyChecking |
Damien Miller | 12c150e | 2003-12-17 16:31:10 +1100 | [diff] [blame] | 474 | .It TCPKeepAlive |
Damien Miller | d27b947 | 2005-12-13 19:29:02 +1100 | [diff] [blame] | 475 | .It Tunnel |
| 476 | .It TunnelDevice |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 477 | .It UsePrivilegedPort |
| 478 | .It User |
| 479 | .It UserKnownHostsFile |
| 480 | .It VerifyHostKeyDNS |
Damien Miller | 8639920 | 2008-06-30 00:04:31 +1000 | [diff] [blame] | 481 | .It VisualHostKey |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 482 | .It XAuthLocation |
| 483 | .El |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 484 | .It Fl p Ar port |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 485 | Port to connect to on the remote host. |
| 486 | This can be specified on a |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 487 | per-host basis in the configuration file. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 488 | .It Fl q |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 489 | Quiet mode. |
Damien Miller | eb60247 | 2008-02-10 22:21:28 +1100 | [diff] [blame] | 490 | Causes most warning and diagnostic messages to be suppressed. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 491 | .It Fl R Xo |
| 492 | .Sm off |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 493 | .Oo Ar bind_address : Oc |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 494 | .Ar port : host : hostport |
| 495 | .Sm on |
| 496 | .Xc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 497 | Specifies that the given port on the remote (server) host is to be |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 498 | forwarded to the given host and port on the local side. |
| 499 | This works by allocating a socket to listen to |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 500 | .Ar port |
| 501 | on the remote side, and whenever a connection is made to this port, the |
| 502 | connection is forwarded over the secure channel, and a connection is |
| 503 | made to |
Damien Miller | 34132e5 | 2000-01-14 15:45:46 +1100 | [diff] [blame] | 504 | .Ar host |
| 505 | port |
| 506 | .Ar hostport |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 507 | from the local machine. |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 508 | .Pp |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 509 | Port forwardings can also be specified in the configuration file. |
| 510 | Privileged ports can be forwarded only when |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 511 | logging in as root on the remote machine. |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 512 | IPv6 addresses can be specified by enclosing the address in square braces or |
| 513 | using an alternative syntax: |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 514 | .Sm off |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 515 | .Xo |
Damien Miller | b096ac4 | 2005-03-09 11:00:05 +1100 | [diff] [blame] | 516 | .Op Ar bind_address No / |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 517 | .Ar host No / Ar port No / |
| 518 | .Ar hostport |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 519 | .Xc . |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 520 | .Sm on |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 521 | .Pp |
| 522 | By default, the listening socket on the server will be bound to the loopback |
| 523 | interface only. |
Darren Tucker | 63917bd | 2008-11-11 16:33:48 +1100 | [diff] [blame] | 524 | This may be overridden by specifying a |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 525 | .Ar bind_address . |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 526 | An empty |
| 527 | .Ar bind_address , |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 528 | or the address |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 529 | .Ql * , |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 530 | indicates that the remote socket should listen on all interfaces. |
| 531 | Specifying a remote |
| 532 | .Ar bind_address |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 533 | will only succeed if the server's |
| 534 | .Cm GatewayPorts |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 535 | option is enabled (see |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 536 | .Xr sshd_config 5 ) . |
Damien Miller | e2f4cc5 | 2009-02-14 16:33:49 +1100 | [diff] [blame] | 537 | .Pp |
| 538 | If the |
| 539 | .Ar port |
| 540 | argument is |
Damien Miller | 65fa4ca | 2009-02-14 16:34:05 +1100 | [diff] [blame] | 541 | .Ql 0 , |
Damien Miller | e2f4cc5 | 2009-02-14 16:33:49 +1100 | [diff] [blame] | 542 | the listen port will be dynamically allocated on the server and reported |
| 543 | to the client at run time. |
Damien Miller | 388f6fc | 2010-05-21 14:57:35 +1000 | [diff] [blame] | 544 | When used together with |
| 545 | .Ic -O forward |
| 546 | the allocated port will be printed to the standard output. |
Darren Tucker | 7ebfc10 | 2004-11-07 20:06:19 +1100 | [diff] [blame] | 547 | .It Fl S Ar ctl_path |
Damien Miller | 67f30d7 | 2010-04-16 15:52:03 +1000 | [diff] [blame] | 548 | Specifies the location of a control socket for connection sharing, |
Damien Miller | 9c60f24 | 2010-03-26 11:28:35 +1100 | [diff] [blame] | 549 | or the string |
| 550 | .Dq none |
| 551 | to disable connection sharing. |
Damien Miller | 0e220db | 2004-06-15 10:34:08 +1000 | [diff] [blame] | 552 | Refer to the description of |
Darren Tucker | ba5c592 | 2004-06-18 16:22:39 +1000 | [diff] [blame] | 553 | .Cm ControlPath |
| 554 | and |
Damien Miller | 0e220db | 2004-06-15 10:34:08 +1000 | [diff] [blame] | 555 | .Cm ControlMaster |
| 556 | in |
| 557 | .Xr ssh_config 5 |
| 558 | for details. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 559 | .It Fl s |
| 560 | May be used to request invocation of a subsystem on the remote system. |
| 561 | Subsystems are a feature of the SSH2 protocol which facilitate the use |
| 562 | of SSH as a secure transport for other applications (eg.\& |
| 563 | .Xr sftp 1 ) . |
| 564 | The subsystem is specified as the remote command. |
| 565 | .It Fl T |
| 566 | Disable pseudo-tty allocation. |
| 567 | .It Fl t |
| 568 | Force pseudo-tty allocation. |
| 569 | This can be used to execute arbitrary |
| 570 | screen-based programs on a remote machine, which can be very useful, |
Damien Miller | 208f1ed | 2006-03-15 11:56:03 +1100 | [diff] [blame] | 571 | e.g. when implementing menu services. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 572 | Multiple |
| 573 | .Fl t |
| 574 | options force tty allocation, even if |
Ben Lindstrom | 19ceb17 | 2001-09-12 17:54:24 +0000 | [diff] [blame] | 575 | .Nm |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 576 | has no local tty. |
| 577 | .It Fl V |
| 578 | Display the version number and exit. |
| 579 | .It Fl v |
| 580 | Verbose mode. |
| 581 | Causes |
Ben Lindstrom | 5ab6ae1 | 2001-02-10 22:08:03 +0000 | [diff] [blame] | 582 | .Nm |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 583 | to print debugging messages about its progress. |
| 584 | This is helpful in |
| 585 | debugging connection, authentication, and configuration problems. |
| 586 | Multiple |
| 587 | .Fl v |
| 588 | options increase the verbosity. |
| 589 | The maximum is 3. |
Darren Tucker | 7ad8dd2 | 2010-01-12 19:40:27 +1100 | [diff] [blame] | 590 | .It Fl W Ar host : Ns Ar port |
| 591 | Requests that standard input and output on the client be forwarded to |
| 592 | .Ar host |
| 593 | on |
| 594 | .Ar port |
| 595 | over the secure channel. |
| 596 | Implies |
| 597 | .Fl N , |
| 598 | .Fl T , |
| 599 | .Cm ExitOnForwardFailure |
| 600 | and |
| 601 | .Cm ClearAllForwardings |
| 602 | and works with Protocol version 2 only. |
Damien Miller | 991dba4 | 2006-07-10 20:16:27 +1000 | [diff] [blame] | 603 | .It Fl w Xo |
| 604 | .Ar local_tun Ns Op : Ns Ar remote_tun |
| 605 | .Xc |
| 606 | Requests |
| 607 | tunnel |
| 608 | device forwarding with the specified |
Damien Miller | d27b947 | 2005-12-13 19:29:02 +1100 | [diff] [blame] | 609 | .Xr tun 4 |
Damien Miller | 991dba4 | 2006-07-10 20:16:27 +1000 | [diff] [blame] | 610 | devices between the client |
| 611 | .Pq Ar local_tun |
| 612 | and the server |
| 613 | .Pq Ar remote_tun . |
| 614 | .Pp |
Damien Miller | cf1e342 | 2005-12-24 14:56:04 +1100 | [diff] [blame] | 615 | The devices may be specified by numerical ID or the keyword |
| 616 | .Dq any , |
| 617 | which uses the next available tunnel device. |
Damien Miller | 991dba4 | 2006-07-10 20:16:27 +1000 | [diff] [blame] | 618 | If |
| 619 | .Ar remote_tun |
| 620 | is not specified, it defaults to |
| 621 | .Dq any . |
Damien Miller | cf1e342 | 2005-12-24 14:56:04 +1100 | [diff] [blame] | 622 | See also the |
Damien Miller | d27b947 | 2005-12-13 19:29:02 +1100 | [diff] [blame] | 623 | .Cm Tunnel |
Damien Miller | 991dba4 | 2006-07-10 20:16:27 +1000 | [diff] [blame] | 624 | and |
| 625 | .Cm TunnelDevice |
| 626 | directives in |
Damien Miller | d27b947 | 2005-12-13 19:29:02 +1100 | [diff] [blame] | 627 | .Xr ssh_config 5 . |
Damien Miller | 991dba4 | 2006-07-10 20:16:27 +1000 | [diff] [blame] | 628 | If the |
| 629 | .Cm Tunnel |
| 630 | directive is unset, it is set to the default tunnel mode, which is |
| 631 | .Dq point-to-point . |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 632 | .It Fl X |
| 633 | Enables X11 forwarding. |
| 634 | This can also be specified on a per-host basis in a configuration file. |
| 635 | .Pp |
| 636 | X11 forwarding should be enabled with caution. |
| 637 | Users with the ability to bypass file permissions on the remote host |
| 638 | (for the user's X authorization database) |
| 639 | can access the local X11 display through the forwarded connection. |
| 640 | An attacker may then be able to perform activities such as keystroke monitoring. |
Damien Miller | 947219e | 2005-03-02 13:22:30 +1100 | [diff] [blame] | 641 | .Pp |
Damien Miller | b022b23 | 2005-03-05 11:22:36 +1100 | [diff] [blame] | 642 | For this reason, X11 forwarding is subjected to X11 SECURITY extension |
Damien Miller | 947219e | 2005-03-02 13:22:30 +1100 | [diff] [blame] | 643 | restrictions by default. |
| 644 | Please refer to the |
| 645 | .Nm |
| 646 | .Fl Y |
| 647 | option and the |
| 648 | .Cm ForwardX11Trusted |
| 649 | directive in |
| 650 | .Xr ssh_config 5 |
| 651 | for more information. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 652 | .It Fl x |
| 653 | Disables X11 forwarding. |
Darren Tucker | 0a118da | 2003-10-15 15:54:32 +1000 | [diff] [blame] | 654 | .It Fl Y |
| 655 | Enables trusted X11 forwarding. |
Damien Miller | 947219e | 2005-03-02 13:22:30 +1100 | [diff] [blame] | 656 | Trusted X11 forwardings are not subjected to the X11 SECURITY extension |
| 657 | controls. |
Damien Miller | e272a5b | 2008-11-03 19:22:37 +1100 | [diff] [blame] | 658 | .It Fl y |
| 659 | Send log information using the |
| 660 | .Xr syslog 3 |
| 661 | system module. |
| 662 | By default this information is sent to stderr. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 663 | .El |
Damien Miller | e9b333a | 2005-12-24 14:53:04 +1100 | [diff] [blame] | 664 | .Pp |
| 665 | .Nm |
| 666 | may additionally obtain configuration data from |
| 667 | a per-user configuration file and a system-wide configuration file. |
| 668 | The file format and configuration options are described in |
| 669 | .Xr ssh_config 5 . |
| 670 | .Pp |
| 671 | .Nm |
| 672 | exits with the exit status of the remote command or with 255 |
| 673 | if an error occurred. |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 674 | .Sh AUTHENTICATION |
Darren Tucker | 94299ec | 2006-01-20 11:30:14 +1100 | [diff] [blame] | 675 | The OpenSSH SSH client supports SSH protocols 1 and 2. |
Darren Tucker | 7a4a765 | 2009-10-11 21:51:40 +1100 | [diff] [blame] | 676 | The default is to use protocol 2 only, |
| 677 | though this can be changed via the |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 678 | .Cm Protocol |
| 679 | option in |
Darren Tucker | 7a4a765 | 2009-10-11 21:51:40 +1100 | [diff] [blame] | 680 | .Xr ssh_config 5 |
| 681 | or the |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 682 | .Fl 1 |
| 683 | and |
| 684 | .Fl 2 |
| 685 | options (see above). |
| 686 | Both protocols support similar authentication methods, |
Darren Tucker | 7a4a765 | 2009-10-11 21:51:40 +1100 | [diff] [blame] | 687 | but protocol 2 is the default since |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 688 | it provides additional mechanisms for confidentiality |
| 689 | (the traffic is encrypted using AES, 3DES, Blowfish, CAST128, or Arcfour) |
Damien Miller | e45796f | 2007-06-11 14:01:42 +1000 | [diff] [blame] | 690 | and integrity (hmac-md5, hmac-sha1, umac-64, hmac-ripemd160). |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 691 | Protocol 1 lacks a strong mechanism for ensuring the |
| 692 | integrity of the connection. |
| 693 | .Pp |
| 694 | The methods available for authentication are: |
Damien Miller | fbc94c8 | 2006-06-13 13:03:16 +1000 | [diff] [blame] | 695 | GSSAPI-based authentication, |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 696 | host-based authentication, |
| 697 | public key authentication, |
| 698 | challenge-response authentication, |
| 699 | and password authentication. |
| 700 | Authentication methods are tried in the order specified above, |
| 701 | though protocol 2 has a configuration option to change the default order: |
| 702 | .Cm PreferredAuthentications . |
| 703 | .Pp |
| 704 | Host-based authentication works as follows: |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 705 | If the machine the user logs in from is listed in |
| 706 | .Pa /etc/hosts.equiv |
| 707 | or |
| 708 | .Pa /etc/shosts.equiv |
| 709 | on the remote machine, and the user names are |
| 710 | the same on both sides, or if the files |
| 711 | .Pa ~/.rhosts |
| 712 | or |
| 713 | .Pa ~/.shosts |
| 714 | exist in the user's home directory on the |
| 715 | remote machine and contain a line containing the name of the client |
| 716 | machine and the name of the user on that machine, the user is |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 717 | considered for login. |
| 718 | Additionally, the server |
| 719 | .Em must |
| 720 | be able to verify the client's |
| 721 | host key (see the description of |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 722 | .Pa /etc/ssh/ssh_known_hosts |
| 723 | and |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 724 | .Pa ~/.ssh/known_hosts , |
| 725 | below) |
| 726 | for login to be permitted. |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 727 | This authentication method closes security holes due to IP |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 728 | spoofing, DNS spoofing, and routing spoofing. |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 729 | [Note to the administrator: |
| 730 | .Pa /etc/hosts.equiv , |
| 731 | .Pa ~/.rhosts , |
| 732 | and the rlogin/rsh protocol in general, are inherently insecure and should be |
| 733 | disabled if security is desired.] |
| 734 | .Pp |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 735 | Public key authentication works as follows: |
| 736 | The scheme is based on public-key cryptography, |
| 737 | using cryptosystems |
| 738 | where encryption and decryption are done using separate keys, |
| 739 | and it is unfeasible to derive the decryption key from the encryption key. |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 740 | The idea is that each user creates a public/private |
| 741 | key pair for authentication purposes. |
| 742 | The server knows the public key, and only the user knows the private key. |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 743 | .Nm |
| 744 | implements public key authentication protocol automatically, |
| 745 | using either the RSA or DSA algorithms. |
| 746 | Protocol 1 is restricted to using only RSA keys, |
| 747 | but protocol 2 may use either. |
| 748 | The |
| 749 | .Sx HISTORY |
| 750 | section of |
| 751 | .Xr ssl 8 |
| 752 | contains a brief discussion of the two algorithms. |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 753 | .Pp |
| 754 | The file |
| 755 | .Pa ~/.ssh/authorized_keys |
| 756 | lists the public keys that are permitted for logging in. |
| 757 | When the user logs in, the |
| 758 | .Nm |
| 759 | program tells the server which key pair it would like to use for |
| 760 | authentication. |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 761 | The client proves that it has access to the private key |
| 762 | and the server checks that the corresponding public key |
| 763 | is authorized to accept the account. |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 764 | .Pp |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 765 | The user creates his/her key pair by running |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 766 | .Xr ssh-keygen 1 . |
| 767 | This stores the private key in |
| 768 | .Pa ~/.ssh/identity |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 769 | (protocol 1), |
| 770 | .Pa ~/.ssh/id_dsa |
| 771 | (protocol 2 DSA), |
| 772 | or |
| 773 | .Pa ~/.ssh/id_rsa |
| 774 | (protocol 2 RSA) |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 775 | and stores the public key in |
| 776 | .Pa ~/.ssh/identity.pub |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 777 | (protocol 1), |
| 778 | .Pa ~/.ssh/id_dsa.pub |
| 779 | (protocol 2 DSA), |
| 780 | or |
| 781 | .Pa ~/.ssh/id_rsa.pub |
| 782 | (protocol 2 RSA) |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 783 | in the user's home directory. |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 784 | The user should then copy the public key |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 785 | to |
| 786 | .Pa ~/.ssh/authorized_keys |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 787 | in his/her home directory on the remote machine. |
| 788 | The |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 789 | .Pa authorized_keys |
| 790 | file corresponds to the conventional |
| 791 | .Pa ~/.rhosts |
| 792 | file, and has one key |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 793 | per line, though the lines can be very long. |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 794 | After this, the user can log in without giving the password. |
| 795 | .Pp |
Damien Miller | 922b541 | 2010-03-05 21:30:54 +1100 | [diff] [blame] | 796 | A variation on public key authentication |
| 797 | is available in the form of certificate authentication: |
| 798 | instead of a set of public/private keys, |
| 799 | signed certificates are used. |
| 800 | This has the advantage that a single trusted certification authority |
| 801 | can be used in place of many public/private keys. |
| 802 | See the |
| 803 | .Sx CERTIFICATES |
| 804 | section of |
| 805 | .Xr ssh-keygen 1 |
| 806 | for more information. |
| 807 | .Pp |
| 808 | The most convenient way to use public key or certificate authentication |
| 809 | may be with an authentication agent. |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 810 | See |
| 811 | .Xr ssh-agent 1 |
| 812 | for more information. |
| 813 | .Pp |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 814 | Challenge-response authentication works as follows: |
| 815 | The server sends an arbitrary |
| 816 | .Qq challenge |
| 817 | text, and prompts for a response. |
| 818 | Protocol 2 allows multiple challenges and responses; |
| 819 | protocol 1 is restricted to just one challenge/response. |
| 820 | Examples of challenge-response authentication include |
| 821 | BSD Authentication (see |
| 822 | .Xr login.conf 5 ) |
| 823 | and PAM (some non-OpenBSD systems). |
| 824 | .Pp |
| 825 | Finally, if other authentication methods fail, |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 826 | .Nm |
| 827 | prompts the user for a password. |
| 828 | The password is sent to the remote |
| 829 | host for checking; however, since all communications are encrypted, |
| 830 | the password cannot be seen by someone listening on the network. |
Damien Miller | 48c94ab | 2006-01-02 23:38:00 +1100 | [diff] [blame] | 831 | .Pp |
| 832 | .Nm |
| 833 | automatically maintains and checks a database containing |
| 834 | identification for all hosts it has ever been used with. |
| 835 | Host keys are stored in |
| 836 | .Pa ~/.ssh/known_hosts |
| 837 | in the user's home directory. |
| 838 | Additionally, the file |
| 839 | .Pa /etc/ssh/ssh_known_hosts |
| 840 | is automatically checked for known hosts. |
| 841 | Any new hosts are automatically added to the user's file. |
| 842 | If a host's identification ever changes, |
| 843 | .Nm |
| 844 | warns about this and disables password authentication to prevent |
| 845 | server spoofing or man-in-the-middle attacks, |
| 846 | which could otherwise be used to circumvent the encryption. |
| 847 | The |
| 848 | .Cm StrictHostKeyChecking |
| 849 | option can be used to control logins to machines whose |
| 850 | host key is not known or has changed. |
| 851 | .Pp |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 852 | When the user's identity has been accepted by the server, the server |
| 853 | either executes the given command, or logs into the machine and gives |
| 854 | the user a normal shell on the remote machine. |
| 855 | All communication with |
| 856 | the remote command or shell will be automatically encrypted. |
| 857 | .Pp |
| 858 | If a pseudo-terminal has been allocated (normal login session), the |
| 859 | user may use the escape characters noted below. |
| 860 | .Pp |
| 861 | If no pseudo-tty has been allocated, |
| 862 | the session is transparent and can be used to reliably transfer binary data. |
| 863 | On most systems, setting the escape character to |
| 864 | .Dq none |
| 865 | will also make the session transparent even if a tty is used. |
| 866 | .Pp |
| 867 | The session terminates when the command or shell on the remote |
Damien Miller | 8bfaf93 | 2006-01-14 10:09:30 +1100 | [diff] [blame] | 868 | machine exits and all X11 and TCP connections have been closed. |
Damien Miller | 52d2061 | 2005-12-24 14:52:36 +1100 | [diff] [blame] | 869 | .Sh ESCAPE CHARACTERS |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 870 | When a pseudo-terminal has been requested, |
| 871 | .Nm |
| 872 | supports a number of functions through the use of an escape character. |
| 873 | .Pp |
| 874 | A single tilde character can be sent as |
| 875 | .Ic ~~ |
| 876 | or by following the tilde by a character other than those described below. |
| 877 | The escape character must always follow a newline to be interpreted as |
| 878 | special. |
| 879 | The escape character can be changed in configuration files using the |
| 880 | .Cm EscapeChar |
| 881 | configuration directive or on the command line by the |
| 882 | .Fl e |
| 883 | option. |
| 884 | .Pp |
| 885 | The supported escapes (assuming the default |
| 886 | .Ql ~ ) |
| 887 | are: |
| 888 | .Bl -tag -width Ds |
| 889 | .It Cm ~. |
| 890 | Disconnect. |
| 891 | .It Cm ~^Z |
| 892 | Background |
Damien Miller | 1164c29 | 2006-01-02 23:38:37 +1100 | [diff] [blame] | 893 | .Nm . |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 894 | .It Cm ~# |
| 895 | List forwarded connections. |
| 896 | .It Cm ~& |
| 897 | Background |
| 898 | .Nm |
| 899 | at logout when waiting for forwarded connection / X11 sessions to terminate. |
| 900 | .It Cm ~? |
| 901 | Display a list of escape characters. |
| 902 | .It Cm ~B |
| 903 | Send a BREAK to the remote system |
| 904 | (only useful for SSH protocol version 2 and if the peer supports it). |
| 905 | .It Cm ~C |
| 906 | Open command line. |
| 907 | Currently this allows the addition of port forwardings using the |
Damien Miller | 0164cb8 | 2008-11-05 16:30:31 +1100 | [diff] [blame] | 908 | .Fl L , |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 909 | .Fl R |
Damien Miller | 0164cb8 | 2008-11-05 16:30:31 +1100 | [diff] [blame] | 910 | and |
| 911 | .Fl D |
Damien Miller | 329cb01 | 2005-12-24 14:53:23 +1100 | [diff] [blame] | 912 | options (see above). |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 913 | It also allows the cancellation of existing remote port-forwardings |
| 914 | using |
Damien Miller | 57e8ad3 | 2006-07-10 20:20:52 +1000 | [diff] [blame] | 915 | .Sm off |
| 916 | .Fl KR Oo Ar bind_address : Oc Ar port . |
| 917 | .Sm on |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 918 | .Ic !\& Ns Ar command |
| 919 | allows the user to execute a local command if the |
| 920 | .Ic PermitLocalCommand |
| 921 | option is enabled in |
| 922 | .Xr ssh_config 5 . |
| 923 | Basic help is available, using the |
| 924 | .Fl h |
| 925 | option. |
| 926 | .It Cm ~R |
| 927 | Request rekeying of the connection |
| 928 | (only useful for SSH protocol version 2 and if the peer supports it). |
| 929 | .El |
Damien Miller | f317718 | 2006-01-14 10:09:13 +1100 | [diff] [blame] | 930 | .Sh TCP FORWARDING |
| 931 | Forwarding of arbitrary TCP connections over the secure channel can |
| 932 | be specified either on the command line or in a configuration file. |
| 933 | One possible application of TCP forwarding is a secure connection to a |
| 934 | mail server; another is going through firewalls. |
| 935 | .Pp |
| 936 | In the example below, we look at encrypting communication between |
| 937 | an IRC client and server, even though the IRC server does not directly |
| 938 | support encrypted communications. |
| 939 | This works as follows: |
| 940 | the user connects to the remote host using |
| 941 | .Nm , |
| 942 | specifying a port to be used to forward connections |
| 943 | to the remote server. |
| 944 | After that it is possible to start the service which is to be encrypted |
| 945 | on the client machine, |
| 946 | connecting to the same local port, |
| 947 | and |
| 948 | .Nm |
| 949 | will encrypt and forward the connection. |
| 950 | .Pp |
| 951 | The following example tunnels an IRC session from client machine |
| 952 | .Dq 127.0.0.1 |
| 953 | (localhost) |
| 954 | to remote server |
| 955 | .Dq server.example.com : |
| 956 | .Bd -literal -offset 4n |
| 957 | $ ssh -f -L 1234:localhost:6667 server.example.com sleep 10 |
| 958 | $ irc -c '#users' -p 1234 pinky 127.0.0.1 |
| 959 | .Ed |
| 960 | .Pp |
| 961 | This tunnels a connection to IRC server |
| 962 | .Dq server.example.com , |
| 963 | joining channel |
| 964 | .Dq #users , |
| 965 | nickname |
| 966 | .Dq pinky , |
| 967 | using port 1234. |
| 968 | It doesn't matter which port is used, |
| 969 | as long as it's greater than 1023 |
| 970 | (remember, only root can open sockets on privileged ports) |
| 971 | and doesn't conflict with any ports already in use. |
| 972 | The connection is forwarded to port 6667 on the remote server, |
| 973 | since that's the standard port for IRC services. |
| 974 | .Pp |
| 975 | The |
| 976 | .Fl f |
| 977 | option backgrounds |
| 978 | .Nm |
| 979 | and the remote command |
| 980 | .Dq sleep 10 |
| 981 | is specified to allow an amount of time |
| 982 | (10 seconds, in the example) |
| 983 | to start the service which is to be tunnelled. |
| 984 | If no connections are made within the time specified, |
| 985 | .Nm |
| 986 | will exit. |
Damien Miller | f317718 | 2006-01-14 10:09:13 +1100 | [diff] [blame] | 987 | .Sh X11 FORWARDING |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 988 | If the |
| 989 | .Cm ForwardX11 |
| 990 | variable is set to |
| 991 | .Dq yes |
| 992 | (or see the description of the |
Damien Miller | d7f308f | 2005-12-24 14:55:16 +1100 | [diff] [blame] | 993 | .Fl X , |
| 994 | .Fl x , |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 995 | and |
Damien Miller | d7f308f | 2005-12-24 14:55:16 +1100 | [diff] [blame] | 996 | .Fl Y |
Damien Miller | 9a765b2 | 2005-12-24 14:53:44 +1100 | [diff] [blame] | 997 | options above) |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 998 | and the user is using X11 (the |
| 999 | .Ev DISPLAY |
| 1000 | environment variable is set), the connection to the X11 display is |
| 1001 | automatically forwarded to the remote side in such a way that any X11 |
| 1002 | programs started from the shell (or command) will go through the |
| 1003 | encrypted channel, and the connection to the real X server will be made |
| 1004 | from the local machine. |
| 1005 | The user should not manually set |
| 1006 | .Ev DISPLAY . |
| 1007 | Forwarding of X11 connections can be |
| 1008 | configured on the command line or in configuration files. |
| 1009 | .Pp |
| 1010 | The |
| 1011 | .Ev DISPLAY |
| 1012 | value set by |
| 1013 | .Nm |
| 1014 | will point to the server machine, but with a display number greater than zero. |
| 1015 | This is normal, and happens because |
| 1016 | .Nm |
| 1017 | creates a |
| 1018 | .Dq proxy |
| 1019 | X server on the server machine for forwarding the |
| 1020 | connections over the encrypted channel. |
| 1021 | .Pp |
| 1022 | .Nm |
| 1023 | will also automatically set up Xauthority data on the server machine. |
| 1024 | For this purpose, it will generate a random authorization cookie, |
| 1025 | store it in Xauthority on the server, and verify that any forwarded |
| 1026 | connections carry this cookie and replace it by the real cookie when |
| 1027 | the connection is opened. |
| 1028 | The real authentication cookie is never |
| 1029 | sent to the server machine (and no cookies are sent in the plain). |
| 1030 | .Pp |
| 1031 | If the |
| 1032 | .Cm ForwardAgent |
| 1033 | variable is set to |
| 1034 | .Dq yes |
| 1035 | (or see the description of the |
| 1036 | .Fl A |
| 1037 | and |
| 1038 | .Fl a |
Damien Miller | 9a765b2 | 2005-12-24 14:53:44 +1100 | [diff] [blame] | 1039 | options above) and |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 1040 | the user is using an authentication agent, the connection to the agent |
| 1041 | is automatically forwarded to the remote side. |
Damien Miller | bbc5909 | 2006-01-31 21:46:51 +1100 | [diff] [blame] | 1042 | .Sh VERIFYING HOST KEYS |
| 1043 | When connecting to a server for the first time, |
| 1044 | a fingerprint of the server's public key is presented to the user |
| 1045 | (unless the option |
| 1046 | .Cm StrictHostKeyChecking |
| 1047 | has been disabled). |
| 1048 | Fingerprints can be determined using |
| 1049 | .Xr ssh-keygen 1 : |
| 1050 | .Pp |
| 1051 | .Dl $ ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key |
| 1052 | .Pp |
Darren Tucker | f6bffb1 | 2008-06-14 09:04:26 +1000 | [diff] [blame] | 1053 | If the fingerprint is already known, it can be matched |
| 1054 | and the key can be accepted or rejected. |
| 1055 | Because of the difficulty of comparing host keys |
| 1056 | just by looking at hex strings, |
| 1057 | there is also support to compare host keys visually, |
| 1058 | using |
| 1059 | .Em random art . |
| 1060 | By setting the |
Damien Miller | 1028824 | 2008-06-30 00:04:03 +1000 | [diff] [blame] | 1061 | .Cm VisualHostKey |
Darren Tucker | f6bffb1 | 2008-06-14 09:04:26 +1000 | [diff] [blame] | 1062 | option to |
Damien Miller | 1028824 | 2008-06-30 00:04:03 +1000 | [diff] [blame] | 1063 | .Dq yes , |
Darren Tucker | f6bffb1 | 2008-06-14 09:04:26 +1000 | [diff] [blame] | 1064 | a small ASCII graphic gets displayed on every login to a server, no matter |
| 1065 | if the session itself is interactive or not. |
| 1066 | By learning the pattern a known server produces, a user can easily |
| 1067 | find out that the host key has changed when a completely different pattern |
| 1068 | is displayed. |
| 1069 | Because these patterns are not unambiguous however, a pattern that looks |
| 1070 | similar to the pattern remembered only gives a good probability that the |
| 1071 | host key is the same, not guaranteed proof. |
| 1072 | .Pp |
| 1073 | To get a listing of the fingerprints along with their random art for |
| 1074 | all known hosts, the following command line can be used: |
| 1075 | .Pp |
| 1076 | .Dl $ ssh-keygen -lv -f ~/.ssh/known_hosts |
| 1077 | .Pp |
Damien Miller | bbc5909 | 2006-01-31 21:46:51 +1100 | [diff] [blame] | 1078 | If the fingerprint is unknown, |
| 1079 | an alternative method of verification is available: |
| 1080 | SSH fingerprints verified by DNS. |
| 1081 | An additional resource record (RR), |
| 1082 | SSHFP, |
| 1083 | is added to a zonefile |
| 1084 | and the connecting client is able to match the fingerprint |
| 1085 | with that of the key presented. |
| 1086 | .Pp |
| 1087 | In this example, we are connecting a client to a server, |
| 1088 | .Dq host.example.com . |
| 1089 | The SSHFP resource records should first be added to the zonefile for |
| 1090 | host.example.com: |
| 1091 | .Bd -literal -offset indent |
Damien Miller | a1b3d63 | 2006-03-26 00:07:02 +1100 | [diff] [blame] | 1092 | $ ssh-keygen -r host.example.com. |
Damien Miller | bbc5909 | 2006-01-31 21:46:51 +1100 | [diff] [blame] | 1093 | .Ed |
| 1094 | .Pp |
| 1095 | The output lines will have to be added to the zonefile. |
| 1096 | To check that the zone is answering fingerprint queries: |
| 1097 | .Pp |
| 1098 | .Dl $ dig -t SSHFP host.example.com |
| 1099 | .Pp |
| 1100 | Finally the client connects: |
| 1101 | .Bd -literal -offset indent |
| 1102 | $ ssh -o "VerifyHostKeyDNS ask" host.example.com |
| 1103 | [...] |
| 1104 | Matching host key fingerprint found in DNS. |
| 1105 | Are you sure you want to continue connecting (yes/no)? |
| 1106 | .Ed |
| 1107 | .Pp |
| 1108 | See the |
| 1109 | .Cm VerifyHostKeyDNS |
| 1110 | option in |
| 1111 | .Xr ssh_config 5 |
| 1112 | for more information. |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1113 | .Sh SSH-BASED VIRTUAL PRIVATE NETWORKS |
| 1114 | .Nm |
| 1115 | contains support for Virtual Private Network (VPN) tunnelling |
| 1116 | using the |
| 1117 | .Xr tun 4 |
| 1118 | network pseudo-device, |
| 1119 | allowing two networks to be joined securely. |
| 1120 | The |
| 1121 | .Xr sshd_config 5 |
| 1122 | configuration option |
| 1123 | .Cm PermitTunnel |
| 1124 | controls whether the server supports this, |
| 1125 | and at what level (layer 2 or 3 traffic). |
| 1126 | .Pp |
| 1127 | The following example would connect client network 10.0.50.0/24 |
Damien Miller | 3975ee2 | 2006-11-05 05:31:33 +1100 | [diff] [blame] | 1128 | with remote network 10.0.99.0/24 using a point-to-point connection |
| 1129 | from 10.1.1.1 to 10.1.1.2, |
| 1130 | provided that the SSH server running on the gateway to the remote network, |
| 1131 | at 192.168.1.15, allows it. |
| 1132 | .Pp |
| 1133 | On the client: |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1134 | .Bd -literal -offset indent |
| 1135 | # ssh -f -w 0:1 192.168.1.15 true |
Damien Miller | 3975ee2 | 2006-11-05 05:31:33 +1100 | [diff] [blame] | 1136 | # ifconfig tun0 10.1.1.1 10.1.1.2 netmask 255.255.255.252 |
| 1137 | # route add 10.0.99.0/24 10.1.1.2 |
| 1138 | .Ed |
| 1139 | .Pp |
| 1140 | On the server: |
| 1141 | .Bd -literal -offset indent |
| 1142 | # ifconfig tun1 10.1.1.2 10.1.1.1 netmask 255.255.255.252 |
| 1143 | # route add 10.0.50.0/24 10.1.1.1 |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1144 | .Ed |
| 1145 | .Pp |
| 1146 | Client access may be more finely tuned via the |
| 1147 | .Pa /root/.ssh/authorized_keys |
| 1148 | file (see below) and the |
| 1149 | .Cm PermitRootLogin |
| 1150 | server option. |
Damien Miller | e93eaaa | 2006-03-15 11:05:59 +1100 | [diff] [blame] | 1151 | The following entry would permit connections on |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1152 | .Xr tun 4 |
Damien Miller | e93eaaa | 2006-03-15 11:05:59 +1100 | [diff] [blame] | 1153 | device 1 from user |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1154 | .Dq jane |
Damien Miller | e93eaaa | 2006-03-15 11:05:59 +1100 | [diff] [blame] | 1155 | and on tun device 2 from user |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1156 | .Dq john , |
| 1157 | if |
| 1158 | .Cm PermitRootLogin |
| 1159 | is set to |
| 1160 | .Dq forced-commands-only : |
| 1161 | .Bd -literal -offset 2n |
| 1162 | tunnel="1",command="sh /etc/netstart tun1" ssh-rsa ... jane |
Damien Miller | 9f67a21 | 2006-03-15 11:05:35 +1100 | [diff] [blame] | 1163 | tunnel="2",command="sh /etc/netstart tun2" ssh-rsa ... john |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1164 | .Ed |
| 1165 | .Pp |
Darren Tucker | ffe88e1 | 2006-10-18 07:53:06 +1000 | [diff] [blame] | 1166 | Since an SSH-based setup entails a fair amount of overhead, |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1167 | it may be more suited to temporary setups, |
| 1168 | such as for wireless VPNs. |
| 1169 | More permanent VPNs are better provided by tools such as |
| 1170 | .Xr ipsecctl 8 |
| 1171 | and |
| 1172 | .Xr isakmpd 8 . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1173 | .Sh ENVIRONMENT |
| 1174 | .Nm |
| 1175 | will normally set the following environment variables: |
Damien Miller | 6aa2290 | 2006-01-06 14:48:34 +1100 | [diff] [blame] | 1176 | .Bl -tag -width "SSH_ORIGINAL_COMMAND" |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1177 | .It Ev DISPLAY |
| 1178 | The |
| 1179 | .Ev DISPLAY |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1180 | variable indicates the location of the X11 server. |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 1181 | It is automatically set by |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1182 | .Nm |
| 1183 | to point to a value of the form |
Damien Miller | 14af93e | 2006-01-02 23:38:21 +1100 | [diff] [blame] | 1184 | .Dq hostname:n , |
| 1185 | where |
| 1186 | .Dq hostname |
| 1187 | indicates the host where the shell runs, and |
| 1188 | .Sq n |
| 1189 | is an integer \*(Ge 1. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1190 | .Nm |
| 1191 | uses this special value to forward X11 connections over the secure |
| 1192 | channel. |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 1193 | The user should normally not set |
| 1194 | .Ev DISPLAY |
| 1195 | explicitly, as that |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1196 | will render the X11 connection insecure (and will require the user to |
| 1197 | manually copy any required authorization cookies). |
| 1198 | .It Ev HOME |
| 1199 | Set to the path of the user's home directory. |
| 1200 | .It Ev LOGNAME |
| 1201 | Synonym for |
| 1202 | .Ev USER ; |
| 1203 | set for compatibility with systems that use this variable. |
| 1204 | .It Ev MAIL |
Ben Lindstrom | e59433d | 2001-09-12 16:41:37 +0000 | [diff] [blame] | 1205 | Set to the path of the user's mailbox. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1206 | .It Ev PATH |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1207 | Set to the default |
| 1208 | .Ev PATH , |
| 1209 | as specified when compiling |
Damien Miller | 1164c29 | 2006-01-02 23:38:37 +1100 | [diff] [blame] | 1210 | .Nm . |
Ben Lindstrom | 5bf5d67 | 2001-07-04 04:31:38 +0000 | [diff] [blame] | 1211 | .It Ev SSH_ASKPASS |
| 1212 | If |
| 1213 | .Nm |
| 1214 | needs a passphrase, it will read the passphrase from the current |
| 1215 | terminal if it was run from a terminal. |
| 1216 | If |
| 1217 | .Nm |
| 1218 | does not have a terminal associated with it but |
| 1219 | .Ev DISPLAY |
| 1220 | and |
| 1221 | .Ev SSH_ASKPASS |
| 1222 | are set, it will execute the program specified by |
| 1223 | .Ev SSH_ASKPASS |
| 1224 | and open an X11 window to read the passphrase. |
| 1225 | This is particularly useful when calling |
| 1226 | .Nm |
| 1227 | from a |
Darren Tucker | 4e4fe00 | 2004-11-05 20:01:03 +1100 | [diff] [blame] | 1228 | .Pa .xsession |
Ben Lindstrom | 5bf5d67 | 2001-07-04 04:31:38 +0000 | [diff] [blame] | 1229 | or related script. |
| 1230 | (Note that on some machines it |
| 1231 | may be necessary to redirect the input from |
| 1232 | .Pa /dev/null |
| 1233 | to make this work.) |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1234 | .It Ev SSH_AUTH_SOCK |
Damien Miller | 14af93e | 2006-01-02 23:38:21 +1100 | [diff] [blame] | 1235 | Identifies the path of a |
| 1236 | .Ux Ns -domain |
| 1237 | socket used to communicate with the agent. |
Damien Miller | f37e246 | 2002-09-19 11:47:55 +1000 | [diff] [blame] | 1238 | .It Ev SSH_CONNECTION |
| 1239 | Identifies the client and server ends of the connection. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1240 | The variable contains |
Damien Miller | 14af93e | 2006-01-02 23:38:21 +1100 | [diff] [blame] | 1241 | four space-separated values: client IP address, client port number, |
| 1242 | server IP address, and server port number. |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 1243 | .It Ev SSH_ORIGINAL_COMMAND |
Damien Miller | 14af93e | 2006-01-02 23:38:21 +1100 | [diff] [blame] | 1244 | This variable contains the original command line if a forced command |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 1245 | is executed. |
| 1246 | It can be used to extract the original arguments. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1247 | .It Ev SSH_TTY |
| 1248 | This is set to the name of the tty (path to the device) associated |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1249 | with the current shell or command. |
| 1250 | If the current session has no tty, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1251 | this variable is not set. |
| 1252 | .It Ev TZ |
Damien Miller | 6dbdb6a | 2005-12-13 19:25:43 +1100 | [diff] [blame] | 1253 | This variable is set to indicate the present time zone if it |
Damien Miller | 208f1ed | 2006-03-15 11:56:03 +1100 | [diff] [blame] | 1254 | was set when the daemon was started (i.e. the daemon passes the value |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1255 | on to new connections). |
| 1256 | .It Ev USER |
| 1257 | Set to the name of the user logging in. |
| 1258 | .El |
| 1259 | .Pp |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 1260 | Additionally, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1261 | .Nm |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 1262 | reads |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1263 | .Pa ~/.ssh/environment , |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1264 | and adds lines of the format |
| 1265 | .Dq VARNAME=value |
Damien Miller | 14af93e | 2006-01-02 23:38:21 +1100 | [diff] [blame] | 1266 | to the environment if the file exists and users are allowed to |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 1267 | change their environment. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 1268 | For more information, see the |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 1269 | .Cm PermitUserEnvironment |
Ben Lindstrom | bd9bf38 | 2002-08-20 18:54:20 +0000 | [diff] [blame] | 1270 | option in |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 1271 | .Xr sshd_config 5 . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1272 | .Sh FILES |
Damien Miller | 7655f5c | 2006-01-06 14:48:18 +1100 | [diff] [blame] | 1273 | .Bl -tag -width Ds -compact |
Damien Miller | 7655f5c | 2006-01-06 14:48:18 +1100 | [diff] [blame] | 1274 | .It ~/.rhosts |
Damien Miller | 1bcdb50 | 2006-01-06 14:49:38 +1100 | [diff] [blame] | 1275 | This file is used for host-based authentication (see above). |
Ben Lindstrom | ebd888d | 2001-03-05 05:49:29 +0000 | [diff] [blame] | 1276 | On some machines this file may need to be |
Damien Miller | 1bcdb50 | 2006-01-06 14:49:38 +1100 | [diff] [blame] | 1277 | world-readable if the user's home directory is on an NFS partition, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1278 | because |
| 1279 | .Xr sshd 8 |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1280 | reads it as root. |
| 1281 | Additionally, this file must be owned by the user, |
| 1282 | and must not have write permissions for anyone else. |
| 1283 | The recommended |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1284 | permission for most machines is read/write for the user, and not |
| 1285 | accessible by others. |
| 1286 | .Pp |
Damien Miller | 7655f5c | 2006-01-06 14:48:18 +1100 | [diff] [blame] | 1287 | .It ~/.shosts |
Damien Miller | 1bcdb50 | 2006-01-06 14:49:38 +1100 | [diff] [blame] | 1288 | This file is used in exactly the same way as |
| 1289 | .Pa .rhosts , |
| 1290 | but allows host-based authentication without permitting login with |
| 1291 | rlogin/rsh. |
Damien Miller | 7655f5c | 2006-01-06 14:48:18 +1100 | [diff] [blame] | 1292 | .Pp |
Damien Miller | 520e615 | 2008-02-10 22:46:22 +1100 | [diff] [blame] | 1293 | .It ~/.ssh/ |
| 1294 | This directory is the default location for all user-specific configuration |
| 1295 | and authentication information. |
| 1296 | There is no general requirement to keep the entire contents of this directory |
| 1297 | secret, but the recommended permissions are read/write/execute for the user, |
| 1298 | and not accessible by others. |
| 1299 | .Pp |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1300 | .It ~/.ssh/authorized_keys |
| 1301 | Lists the public keys (RSA/DSA) that can be used for logging in as this user. |
| 1302 | The format of this file is described in the |
| 1303 | .Xr sshd 8 |
| 1304 | manual page. |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1305 | This file is not highly sensitive, but the recommended |
| 1306 | permissions are read/write for the user, and not accessible by others. |
| 1307 | .Pp |
| 1308 | .It ~/.ssh/config |
| 1309 | This is the per-user configuration file. |
| 1310 | The file format and configuration options are described in |
| 1311 | .Xr ssh_config 5 . |
| 1312 | Because of the potential for abuse, this file must have strict permissions: |
| 1313 | read/write for the user, and not accessible by others. |
| 1314 | .Pp |
| 1315 | .It ~/.ssh/environment |
Damien Miller | 4c102ee | 2006-01-06 14:49:17 +1100 | [diff] [blame] | 1316 | Contains additional definitions for environment variables; see |
| 1317 | .Sx ENVIRONMENT , |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1318 | above. |
| 1319 | .Pp |
| 1320 | .It ~/.ssh/identity |
| 1321 | .It ~/.ssh/id_dsa |
| 1322 | .It ~/.ssh/id_rsa |
| 1323 | Contains the private key for authentication. |
| 1324 | These files |
| 1325 | contain sensitive data and should be readable by the user but not |
| 1326 | accessible by others (read/write/execute). |
| 1327 | .Nm |
| 1328 | will simply ignore a private key file if it is accessible by others. |
| 1329 | It is possible to specify a passphrase when |
| 1330 | generating the key which will be used to encrypt the |
| 1331 | sensitive part of this file using 3DES. |
| 1332 | .Pp |
| 1333 | .It ~/.ssh/identity.pub |
| 1334 | .It ~/.ssh/id_dsa.pub |
| 1335 | .It ~/.ssh/id_rsa.pub |
| 1336 | Contains the public key for authentication. |
| 1337 | These files are not |
| 1338 | sensitive and can (but need not) be readable by anyone. |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1339 | .Pp |
| 1340 | .It ~/.ssh/known_hosts |
Damien Miller | e87eb4c | 2006-01-14 10:08:36 +1100 | [diff] [blame] | 1341 | Contains a list of host keys for all hosts the user has logged into |
| 1342 | that are not already in the systemwide list of known host keys. |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1343 | See |
Damien Miller | e87eb4c | 2006-01-14 10:08:36 +1100 | [diff] [blame] | 1344 | .Xr sshd 8 |
| 1345 | for further details of the format of this file. |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1346 | .Pp |
| 1347 | .It ~/.ssh/rc |
| 1348 | Commands in this file are executed by |
| 1349 | .Nm |
Damien Miller | 7e76e1f | 2006-01-14 10:08:57 +1100 | [diff] [blame] | 1350 | when the user logs in, just before the user's shell (or command) is |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1351 | started. |
| 1352 | See the |
| 1353 | .Xr sshd 8 |
| 1354 | manual page for more information. |
| 1355 | .Pp |
Damien Miller | 7655f5c | 2006-01-06 14:48:18 +1100 | [diff] [blame] | 1356 | .It /etc/hosts.equiv |
Damien Miller | 1bcdb50 | 2006-01-06 14:49:38 +1100 | [diff] [blame] | 1357 | This file is for host-based authentication (see above). |
| 1358 | It should only be writable by root. |
Damien Miller | 7655f5c | 2006-01-06 14:48:18 +1100 | [diff] [blame] | 1359 | .Pp |
| 1360 | .It /etc/shosts.equiv |
Damien Miller | 1bcdb50 | 2006-01-06 14:49:38 +1100 | [diff] [blame] | 1361 | This file is used in exactly the same way as |
| 1362 | .Pa hosts.equiv , |
| 1363 | but allows host-based authentication without permitting login with |
| 1364 | rlogin/rsh. |
Damien Miller | 7655f5c | 2006-01-06 14:48:18 +1100 | [diff] [blame] | 1365 | .Pp |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1366 | .It Pa /etc/ssh/ssh_config |
| 1367 | Systemwide configuration file. |
| 1368 | The file format and configuration options are described in |
| 1369 | .Xr ssh_config 5 . |
| 1370 | .Pp |
| 1371 | .It /etc/ssh/ssh_host_key |
| 1372 | .It /etc/ssh/ssh_host_dsa_key |
| 1373 | .It /etc/ssh/ssh_host_rsa_key |
| 1374 | These three files contain the private parts of the host keys |
Damien Miller | 7e76e1f | 2006-01-14 10:08:57 +1100 | [diff] [blame] | 1375 | and are used for host-based authentication. |
| 1376 | If protocol version 1 is used, |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1377 | .Nm |
| 1378 | must be setuid root, since the host key is readable only by root. |
| 1379 | For protocol version 2, |
| 1380 | .Nm |
| 1381 | uses |
| 1382 | .Xr ssh-keysign 8 |
Damien Miller | 7e76e1f | 2006-01-14 10:08:57 +1100 | [diff] [blame] | 1383 | to access the host keys, |
| 1384 | eliminating the requirement that |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1385 | .Nm |
Damien Miller | 7e76e1f | 2006-01-14 10:08:57 +1100 | [diff] [blame] | 1386 | be setuid root when host-based authentication is used. |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1387 | By default |
| 1388 | .Nm |
| 1389 | is not setuid root. |
| 1390 | .Pp |
| 1391 | .It /etc/ssh/ssh_known_hosts |
| 1392 | Systemwide list of known host keys. |
| 1393 | This file should be prepared by the |
| 1394 | system administrator to contain the public host keys of all machines in the |
| 1395 | organization. |
Damien Miller | e87eb4c | 2006-01-14 10:08:36 +1100 | [diff] [blame] | 1396 | It should be world-readable. |
| 1397 | See |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1398 | .Xr sshd 8 |
Damien Miller | e87eb4c | 2006-01-14 10:08:36 +1100 | [diff] [blame] | 1399 | for further details of the format of this file. |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1400 | .Pp |
Damien Miller | 7655f5c | 2006-01-06 14:48:18 +1100 | [diff] [blame] | 1401 | .It /etc/ssh/sshrc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1402 | Commands in this file are executed by |
| 1403 | .Nm |
Damien Miller | 7e76e1f | 2006-01-14 10:08:57 +1100 | [diff] [blame] | 1404 | when the user logs in, just before the user's shell (or command) is started. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1405 | See the |
| 1406 | .Xr sshd 8 |
| 1407 | manual page for more information. |
Damien Miller | 7b28dc5 | 2000-09-05 13:34:53 +1100 | [diff] [blame] | 1408 | .El |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1409 | .Sh SEE ALSO |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1410 | .Xr scp 1 , |
Damien Miller | 3380426 | 2001-02-04 23:20:18 +1100 | [diff] [blame] | 1411 | .Xr sftp 1 , |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1412 | .Xr ssh-add 1 , |
| 1413 | .Xr ssh-agent 1 , |
| 1414 | .Xr ssh-keygen 1 , |
Damien Miller | 128a0f1 | 2006-01-06 14:50:11 +1100 | [diff] [blame] | 1415 | .Xr ssh-keyscan 1 , |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1416 | .Xr tun 4 , |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 1417 | .Xr hosts.equiv 5 , |
Ben Lindstrom | bf69e3b | 2002-06-23 00:31:24 +0000 | [diff] [blame] | 1418 | .Xr ssh_config 5 , |
Ben Lindstrom | c001cd3 | 2002-06-23 00:32:11 +0000 | [diff] [blame] | 1419 | .Xr ssh-keysign 8 , |
Ben Lindstrom | 5ab6ae1 | 2001-02-10 22:08:03 +0000 | [diff] [blame] | 1420 | .Xr sshd 8 |
Ben Lindstrom | 160ec62 | 2001-04-22 17:17:46 +0000 | [diff] [blame] | 1421 | .Rs |
Damien Miller | 39a93a3 | 2006-03-15 11:34:45 +1100 | [diff] [blame] | 1422 | .%R RFC 4250 |
| 1423 | .%T "The Secure Shell (SSH) Protocol Assigned Numbers" |
| 1424 | .%D 2006 |
| 1425 | .Re |
| 1426 | .Rs |
| 1427 | .%R RFC 4251 |
| 1428 | .%T "The Secure Shell (SSH) Protocol Architecture" |
| 1429 | .%D 2006 |
| 1430 | .Re |
| 1431 | .Rs |
| 1432 | .%R RFC 4252 |
| 1433 | .%T "The Secure Shell (SSH) Authentication Protocol" |
| 1434 | .%D 2006 |
| 1435 | .Re |
| 1436 | .Rs |
| 1437 | .%R RFC 4253 |
| 1438 | .%T "The Secure Shell (SSH) Transport Layer Protocol" |
| 1439 | .%D 2006 |
| 1440 | .Re |
| 1441 | .Rs |
| 1442 | .%R RFC 4254 |
| 1443 | .%T "The Secure Shell (SSH) Connection Protocol" |
| 1444 | .%D 2006 |
| 1445 | .Re |
| 1446 | .Rs |
| 1447 | .%R RFC 4255 |
| 1448 | .%T "Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints" |
| 1449 | .%D 2006 |
| 1450 | .Re |
| 1451 | .Rs |
| 1452 | .%R RFC 4256 |
| 1453 | .%T "Generic Message Exchange Authentication for the Secure Shell Protocol (SSH)" |
| 1454 | .%D 2006 |
| 1455 | .Re |
| 1456 | .Rs |
| 1457 | .%R RFC 4335 |
| 1458 | .%T "The Secure Shell (SSH) Session Channel Break Extension" |
| 1459 | .%D 2006 |
| 1460 | .Re |
| 1461 | .Rs |
| 1462 | .%R RFC 4344 |
| 1463 | .%T "The Secure Shell (SSH) Transport Layer Encryption Modes" |
| 1464 | .%D 2006 |
| 1465 | .Re |
| 1466 | .Rs |
| 1467 | .%R RFC 4345 |
| 1468 | .%T "Improved Arcfour Modes for the Secure Shell (SSH) Transport Layer Protocol" |
| 1469 | .%D 2006 |
Ben Lindstrom | 160ec62 | 2001-04-22 17:17:46 +0000 | [diff] [blame] | 1470 | .Re |
Damien Miller | 3e96d74 | 2006-03-25 23:39:29 +1100 | [diff] [blame] | 1471 | .Rs |
| 1472 | .%R RFC 4419 |
| 1473 | .%T "Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol" |
| 1474 | .%D 2006 |
| 1475 | .Re |
Damien Miller | c0367fb | 2007-01-05 16:25:46 +1100 | [diff] [blame] | 1476 | .Rs |
| 1477 | .%R RFC 4716 |
| 1478 | .%T "The Secure Shell (SSH) Public Key File Format" |
| 1479 | .%D 2006 |
| 1480 | .Re |
Darren Tucker | f6bffb1 | 2008-06-14 09:04:26 +1000 | [diff] [blame] | 1481 | .Rs |
| 1482 | .%T "Hash Visualization: a New Technique to improve Real-World Security" |
| 1483 | .%A A. Perrig |
| 1484 | .%A D. Song |
| 1485 | .%D 1999 |
| 1486 | .%O "International Workshop on Cryptographic Techniques and E-Commerce (CrypTEC '99)" |
| 1487 | .Re |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 1488 | .Sh AUTHORS |
| 1489 | OpenSSH is a derivative of the original and free |
| 1490 | ssh 1.2.12 release by Tatu Ylonen. |
| 1491 | Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, |
| 1492 | Theo de Raadt and Dug Song |
| 1493 | removed many bugs, re-added newer features and |
| 1494 | created OpenSSH. |
| 1495 | Markus Friedl contributed the support for SSH |
| 1496 | protocol versions 1.5 and 2.0. |