Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1 | .\" |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 2 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 3 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
| 4 | .\" All rights reserved |
| 5 | .\" |
Damien Miller | e4340be | 2000-09-16 13:29:08 +1100 | [diff] [blame] | 6 | .\" As far as I am concerned, the code I have written for this software |
| 7 | .\" can be used freely for any purpose. Any derived versions of this |
| 8 | .\" software must be clearly marked as such, and if the derived work is |
| 9 | .\" incompatible with the protocol description in the RFC file, it must be |
| 10 | .\" called by a name other than "ssh" or "Secure Shell". |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 11 | .\" |
Ben Lindstrom | 92a2e38 | 2001-03-05 06:59:27 +0000 | [diff] [blame] | 12 | .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. |
| 13 | .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. |
| 14 | .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. |
Damien Miller | e4340be | 2000-09-16 13:29:08 +1100 | [diff] [blame] | 15 | .\" |
| 16 | .\" Redistribution and use in source and binary forms, with or without |
| 17 | .\" modification, are permitted provided that the following conditions |
| 18 | .\" are met: |
| 19 | .\" 1. Redistributions of source code must retain the above copyright |
| 20 | .\" notice, this list of conditions and the following disclaimer. |
| 21 | .\" 2. Redistributions in binary form must reproduce the above copyright |
| 22 | .\" notice, this list of conditions and the following disclaimer in the |
| 23 | .\" documentation and/or other materials provided with the distribution. |
| 24 | .\" |
| 25 | .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| 26 | .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| 27 | .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| 28 | .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| 29 | .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| 30 | .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 31 | .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 32 | .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 33 | .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| 34 | .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 35 | .\" |
Damien Miller | 20bd453 | 2011-08-06 06:17:30 +1000 | [diff] [blame^] | 36 | .\" $OpenBSD: ssh.1,v 1.320 2011/08/02 01:22:11 djm Exp $ |
| 37 | .Dd $Mdocdate: August 2 2011 $ |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 38 | .Dt SSH 1 |
| 39 | .Os |
| 40 | .Sh NAME |
| 41 | .Nm ssh |
Ben Lindstrom | d58eb5f | 2001-03-07 06:07:22 +0000 | [diff] [blame] | 42 | .Nd OpenSSH SSH client (remote login program) |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 43 | .Sh SYNOPSIS |
| 44 | .Nm ssh |
Damien Miller | bcfbc48 | 2010-07-16 13:59:11 +1000 | [diff] [blame] | 45 | .Bk -words |
Damien Miller | e272a5b | 2008-11-03 19:22:37 +1100 | [diff] [blame] | 46 | .Op Fl 1246AaCfgKkMNnqsTtVvXxYy |
Ben Lindstrom | e0f8804 | 2001-04-30 13:06:24 +0000 | [diff] [blame] | 47 | .Op Fl b Ar bind_address |
Damien Miller | 30c3d42 | 2000-05-09 11:02:59 +1000 | [diff] [blame] | 48 | .Op Fl c Ar cipher_spec |
Damien Miller | bcfbc48 | 2010-07-16 13:59:11 +1000 | [diff] [blame] | 49 | .Op Fl D Oo Ar bind_address : Oc Ns Ar port |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 50 | .Op Fl e Ar escape_char |
Ben Lindstrom | 14f31ab | 2001-09-12 17:48:04 +0000 | [diff] [blame] | 51 | .Op Fl F Ar configfile |
Damien Miller | 048dc93 | 2010-02-12 09:22:04 +1100 | [diff] [blame] | 52 | .Op Fl I Ar pkcs11 |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 53 | .Op Fl i Ar identity_file |
Damien Miller | bcfbc48 | 2010-07-16 13:59:11 +1000 | [diff] [blame] | 54 | .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] | 55 | .Op Fl l Ar login_name |
| 56 | .Op Fl m Ar mac_spec |
Darren Tucker | 7ebfc10 | 2004-11-07 20:06:19 +1100 | [diff] [blame] | 57 | .Op Fl O Ar ctl_cmd |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 58 | .Op Fl o Ar option |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 59 | .Op Fl p Ar port |
Damien Miller | bcfbc48 | 2010-07-16 13:59:11 +1000 | [diff] [blame] | 60 | .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] | 61 | .Op Fl S Ar ctl_path |
Darren Tucker | 7ad8dd2 | 2010-01-12 19:40:27 +1100 | [diff] [blame] | 62 | .Op Fl W Ar host : Ns Ar port |
Damien Miller | bcfbc48 | 2010-07-16 13:59:11 +1000 | [diff] [blame] | 63 | .Op Fl w Ar local_tun Ns Op : Ns Ar remote_tun |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 64 | .Oo Ar user Ns @ Oc Ns Ar hostname |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 65 | .Op Ar command |
Damien Miller | bcfbc48 | 2010-07-16 13:59:11 +1000 | [diff] [blame] | 66 | .Ek |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 67 | .Sh DESCRIPTION |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 68 | .Nm |
Ben Lindstrom | d58eb5f | 2001-03-07 06:07:22 +0000 | [diff] [blame] | 69 | (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] | 70 | executing commands on a remote machine. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 71 | It is intended to replace rlogin and rsh, |
| 72 | and provide secure encrypted communications between |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 73 | two untrusted hosts over an insecure network. |
Damien Miller | 8bfaf93 | 2006-01-14 10:09:30 +1100 | [diff] [blame] | 74 | X11 connections and arbitrary TCP ports |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 75 | can also be forwarded over the secure channel. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 76 | .Pp |
| 77 | .Nm |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 78 | connects and logs into the specified |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 79 | .Ar hostname |
| 80 | (with optional |
| 81 | .Ar user |
| 82 | name). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 83 | The user must prove |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 84 | his/her identity to the remote machine using one of several methods |
Darren Tucker | 5434cfe | 2005-12-20 16:11:35 +1100 | [diff] [blame] | 85 | depending on the protocol version used (see below). |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 86 | .Pp |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 87 | If |
| 88 | .Ar command |
| 89 | is specified, |
Darren Tucker | b18c867 | 2005-12-20 16:10:09 +1100 | [diff] [blame] | 90 | it is executed on the remote host instead of a login shell. |
Darren Tucker | 0b42e6d | 2004-08-13 21:22:40 +1000 | [diff] [blame] | 91 | .Pp |
Damien Miller | 0bc1bd8 | 2000-11-13 22:57:25 +1100 | [diff] [blame] | 92 | The options are as follows: |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 93 | .Bl -tag -width Ds |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 94 | .It Fl 1 |
| 95 | Forces |
| 96 | .Nm |
| 97 | to try protocol version 1 only. |
| 98 | .It Fl 2 |
| 99 | Forces |
| 100 | .Nm |
| 101 | to try protocol version 2 only. |
| 102 | .It Fl 4 |
| 103 | Forces |
| 104 | .Nm |
| 105 | to use IPv4 addresses only. |
| 106 | .It Fl 6 |
| 107 | Forces |
| 108 | .Nm |
| 109 | to use IPv6 addresses only. |
Damien Miller | b1715dc | 2000-05-30 13:44:51 +1000 | [diff] [blame] | 110 | .It Fl A |
| 111 | Enables forwarding of the authentication agent connection. |
| 112 | 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] | 113 | .Pp |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 114 | Agent forwarding should be enabled with caution. |
| 115 | Users with the ability to bypass file permissions on the remote host |
Darren Tucker | ae69e1d | 2009-10-24 11:41:34 +1100 | [diff] [blame] | 116 | (for the agent's |
Darren Tucker | 98c9aec | 2009-10-24 11:42:44 +1100 | [diff] [blame] | 117 | .Ux Ns -domain |
| 118 | socket) can access the local agent through the forwarded connection. |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 119 | An attacker cannot obtain key material from the agent, |
Damien Miller | b5fdfaa | 2002-09-12 09:52:03 +1000 | [diff] [blame] | 120 | however they can perform operations on the keys that enable them to |
| 121 | authenticate using the identities loaded into the agent. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 122 | .It Fl a |
| 123 | Disables forwarding of the authentication agent connection. |
Ben Lindstrom | e0f8804 | 2001-04-30 13:06:24 +0000 | [diff] [blame] | 124 | .It Fl b Ar bind_address |
Darren Tucker | a5cf855 | 2005-07-14 17:04:18 +1000 | [diff] [blame] | 125 | Use |
| 126 | .Ar bind_address |
| 127 | on the local machine as the source address |
| 128 | of the connection. |
| 129 | Only useful on systems with more than one address. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 130 | .It Fl C |
| 131 | Requests compression of all data (including stdin, stdout, stderr, and |
Damien Miller | 8bfaf93 | 2006-01-14 10:09:30 +1100 | [diff] [blame] | 132 | data for forwarded X11 and TCP connections). |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 133 | The compression algorithm is the same used by |
| 134 | .Xr gzip 1 , |
| 135 | and the |
| 136 | .Dq level |
| 137 | can be controlled by the |
| 138 | .Cm CompressionLevel |
| 139 | option for protocol version 1. |
| 140 | Compression is desirable on modem lines and other |
| 141 | slow connections, but will only slow down things on fast networks. |
| 142 | The default value can be set on a host-by-host basis in the |
| 143 | configuration files; see the |
| 144 | .Cm Compression |
| 145 | option. |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 146 | .It Fl c Ar cipher_spec |
| 147 | Selects the cipher specification for encrypting the session. |
| 148 | .Pp |
| 149 | Protocol version 1 allows specification of a single cipher. |
Darren Tucker | 1e4308e | 2005-10-03 18:18:40 +1000 | [diff] [blame] | 150 | The supported values are |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 151 | .Dq 3des , |
Darren Tucker | ff9f484 | 2005-12-20 16:10:45 +1100 | [diff] [blame] | 152 | .Dq blowfish , |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 153 | and |
| 154 | .Dq des . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 155 | .Ar 3des |
| 156 | (triple-des) is an encrypt-decrypt-encrypt triple with three different keys. |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 157 | It is believed to be secure. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 158 | .Ar blowfish |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 159 | 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] | 160 | .Ar 3des . |
Ben Lindstrom | ffa1dd6 | 2001-09-12 16:52:28 +0000 | [diff] [blame] | 161 | .Ar des |
| 162 | is only supported in the |
| 163 | .Nm |
| 164 | client for interoperability with legacy protocol 1 implementations |
| 165 | that do not support the |
| 166 | .Ar 3des |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 167 | cipher. |
| 168 | Its use is strongly discouraged due to cryptographic weaknesses. |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 169 | The default is |
| 170 | .Dq 3des . |
| 171 | .Pp |
Damien Miller | 3597821 | 2005-12-24 14:56:47 +1100 | [diff] [blame] | 172 | For protocol version 2, |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 173 | .Ar cipher_spec |
| 174 | is a comma-separated list of ciphers |
| 175 | listed in order of preference. |
Darren Tucker | 3a6a51f | 2009-06-21 17:48:52 +1000 | [diff] [blame] | 176 | See the |
| 177 | .Cm Ciphers |
Damien Miller | 081f3c7 | 2010-08-03 16:05:25 +1000 | [diff] [blame] | 178 | keyword in |
| 179 | .Xr ssh_config 5 |
| 180 | for more information. |
Darren Tucker | c8d6421 | 2005-10-03 18:13:42 +1000 | [diff] [blame] | 181 | .It Fl D Xo |
| 182 | .Sm off |
| 183 | .Oo Ar bind_address : Oc |
| 184 | .Ar port |
| 185 | .Sm on |
| 186 | .Xc |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 187 | Specifies a local |
| 188 | .Dq dynamic |
| 189 | application-level port forwarding. |
| 190 | This works by allocating a socket to listen to |
| 191 | .Ar port |
Darren Tucker | c8d6421 | 2005-10-03 18:13:42 +1000 | [diff] [blame] | 192 | on the local side, optionally bound to the specified |
| 193 | .Ar bind_address . |
| 194 | Whenever a connection is made to this port, the |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 195 | connection is forwarded over the secure channel, and the application |
| 196 | protocol is then used to determine where to connect to from the |
| 197 | remote machine. |
| 198 | Currently the SOCKS4 and SOCKS5 protocols are supported, and |
| 199 | .Nm |
| 200 | will act as a SOCKS server. |
| 201 | Only root can forward privileged ports. |
| 202 | Dynamic port forwardings can also be specified in the configuration file. |
Darren Tucker | c8d6421 | 2005-10-03 18:13:42 +1000 | [diff] [blame] | 203 | .Pp |
Damien Miller | 7fa9660 | 2010-08-05 13:03:13 +1000 | [diff] [blame] | 204 | IPv6 addresses can be specified by enclosing the address in square brackets. |
Darren Tucker | c8d6421 | 2005-10-03 18:13:42 +1000 | [diff] [blame] | 205 | Only the superuser can forward privileged ports. |
| 206 | By default, the local port is bound in accordance with the |
| 207 | .Cm GatewayPorts |
| 208 | setting. |
| 209 | However, an explicit |
| 210 | .Ar bind_address |
| 211 | may be used to bind the connection to a specific address. |
| 212 | The |
| 213 | .Ar bind_address |
| 214 | of |
| 215 | .Dq localhost |
| 216 | indicates that the listening port be bound for local use only, while an |
| 217 | empty address or |
| 218 | .Sq * |
| 219 | indicates that the port should be available from all interfaces. |
Damien Miller | 2142ba0 | 2005-12-24 14:56:29 +1100 | [diff] [blame] | 220 | .It Fl e Ar escape_char |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 221 | Sets the escape character for sessions with a pty (default: |
| 222 | .Ql ~ ) . |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 223 | The escape character is only recognized at the beginning of a line. |
| 224 | The escape character followed by a dot |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 225 | .Pq Ql \&. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 226 | closes the connection; |
| 227 | followed by control-Z suspends the connection; |
| 228 | and followed by itself sends the escape character once. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 229 | Setting the character to |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 230 | .Dq none |
| 231 | disables any escapes and makes the session fully transparent. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 232 | .It Fl F Ar configfile |
| 233 | Specifies an alternative per-user configuration file. |
| 234 | If a configuration file is given on the command line, |
| 235 | the system-wide configuration file |
| 236 | .Pq Pa /etc/ssh/ssh_config |
| 237 | will be ignored. |
| 238 | The default for the per-user configuration file is |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 239 | .Pa ~/.ssh/config . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 240 | .It Fl f |
| 241 | Requests |
| 242 | .Nm |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 243 | to go to background just before command execution. |
| 244 | This is useful if |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 245 | .Nm |
| 246 | is going to ask for passwords or passphrases, but the user |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 247 | wants it in the background. |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 248 | This implies |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 249 | .Fl n . |
| 250 | The recommended way to start X11 programs at a remote site is with |
| 251 | something like |
| 252 | .Ic ssh -f host xterm . |
Darren Tucker | 9a2a609 | 2008-07-04 12:53:50 +1000 | [diff] [blame] | 253 | .Pp |
| 254 | If the |
| 255 | .Cm ExitOnForwardFailure |
| 256 | configuration option is set to |
| 257 | .Dq yes , |
| 258 | then a client started with |
| 259 | .Fl f |
| 260 | will wait for all remote port forwards to be successfully established |
| 261 | before placing itself in the background. |
Damien Miller | 396691a | 2000-01-20 22:44:08 +1100 | [diff] [blame] | 262 | .It Fl g |
| 263 | Allows remote hosts to connect to local forwarded ports. |
Damien Miller | 7ea845e | 2010-02-12 09:21:02 +1100 | [diff] [blame] | 264 | .It Fl I Ar pkcs11 |
Damien Miller | d400da5 | 2010-02-12 09:26:23 +1100 | [diff] [blame] | 265 | Specify the PKCS#11 shared library |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 266 | .Nm |
Damien Miller | a761844 | 2010-02-12 09:26:02 +1100 | [diff] [blame] | 267 | 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] | 268 | private RSA key. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 269 | .It Fl i Ar identity_file |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 270 | Selects a file from which the identity (private key) for |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 271 | public key authentication is read. |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 272 | The default is |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 273 | .Pa ~/.ssh/identity |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 274 | for protocol version 1, and |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 275 | .Pa ~/.ssh/id_dsa , |
| 276 | .Pa ~/.ssh/id_ecdsa |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 277 | and |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 278 | .Pa ~/.ssh/id_rsa |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 279 | for protocol version 2. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 280 | Identity files may also be specified on |
| 281 | a per-host basis in the configuration file. |
| 282 | It is possible to have multiple |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 283 | .Fl i |
| 284 | options (and multiple identities specified in |
| 285 | configuration files). |
Damien Miller | 5059d8d | 2010-03-05 21:31:11 +1100 | [diff] [blame] | 286 | .Nm |
| 287 | will also try to load certificate information from the filename obtained |
| 288 | by appending |
| 289 | .Pa -cert.pub |
| 290 | to identity filenames. |
Darren Tucker | 415bddc | 2007-06-12 23:43:16 +1000 | [diff] [blame] | 291 | .It Fl K |
| 292 | Enables GSSAPI-based authentication and forwarding (delegation) of GSSAPI |
| 293 | credentials to the server. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 294 | .It Fl k |
Damien Miller | e0113cc | 2003-11-24 13:10:09 +1100 | [diff] [blame] | 295 | Disables forwarding (delegation) of GSSAPI credentials to the server. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 296 | .It Fl L Xo |
| 297 | .Sm off |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 298 | .Oo Ar bind_address : Oc |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 299 | .Ar port : host : hostport |
| 300 | .Sm on |
| 301 | .Xc |
| 302 | Specifies that the given port on the local (client) host is to be |
| 303 | forwarded to the given host and port on the remote side. |
| 304 | This works by allocating a socket to listen to |
| 305 | .Ar port |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 306 | on the local side, optionally bound to the specified |
| 307 | .Ar bind_address . |
| 308 | Whenever a connection is made to this port, the |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 309 | connection is forwarded over the secure channel, and a connection is |
| 310 | made to |
| 311 | .Ar host |
| 312 | port |
| 313 | .Ar hostport |
| 314 | from the remote machine. |
| 315 | Port forwardings can also be specified in the configuration file. |
Damien Miller | 7fa9660 | 2010-08-05 13:03:13 +1000 | [diff] [blame] | 316 | IPv6 addresses can be specified by enclosing the address in square brackets. |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 317 | Only the superuser can forward privileged ports. |
| 318 | By default, the local port is bound in accordance with the |
| 319 | .Cm GatewayPorts |
| 320 | setting. |
| 321 | However, an explicit |
| 322 | .Ar bind_address |
| 323 | may be used to bind the connection to a specific address. |
| 324 | The |
| 325 | .Ar bind_address |
| 326 | of |
| 327 | .Dq localhost |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 328 | indicates that the listening port be bound for local use only, while an |
| 329 | empty address or |
| 330 | .Sq * |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 331 | indicates that the port should be available from all interfaces. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 332 | .It Fl l Ar login_name |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 333 | Specifies the user to log in as on the remote machine. |
| 334 | 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] | 335 | .It Fl M |
| 336 | Places the |
| 337 | .Nm |
| 338 | client into |
| 339 | .Dq master |
| 340 | mode for connection sharing. |
Damien Miller | 88b2552 | 2005-12-31 16:23:15 +1100 | [diff] [blame] | 341 | Multiple |
| 342 | .Fl M |
| 343 | options places |
| 344 | .Nm |
| 345 | into |
| 346 | .Dq master |
| 347 | mode with confirmation required before slave connections are accepted. |
Damien Miller | 0e220db | 2004-06-15 10:34:08 +1000 | [diff] [blame] | 348 | Refer to the description of |
| 349 | .Cm ControlMaster |
| 350 | in |
| 351 | .Xr ssh_config 5 |
| 352 | for details. |
Damien Miller | 5d1eceb | 2004-06-30 22:37:57 +1000 | [diff] [blame] | 353 | .It Fl m Ar mac_spec |
| 354 | Additionally, for protocol version 2 a comma-separated list of MAC |
| 355 | (message authentication code) algorithms can |
| 356 | be specified in order of preference. |
| 357 | See the |
| 358 | .Cm MACs |
| 359 | keyword for more information. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 360 | .It Fl N |
| 361 | Do not execute a remote command. |
| 362 | This is useful for just forwarding ports |
| 363 | (protocol version 2 only). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 364 | .It Fl n |
| 365 | Redirects stdin from |
| 366 | .Pa /dev/null |
| 367 | (actually, prevents reading from stdin). |
| 368 | This must be used when |
| 369 | .Nm |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 370 | is run in the background. |
| 371 | A common trick is to use this to run X11 programs on a remote machine. |
| 372 | For example, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 373 | .Ic ssh -n shadows.cs.hut.fi emacs & |
| 374 | will start an emacs on shadows.cs.hut.fi, and the X11 |
| 375 | connection will be automatically forwarded over an encrypted channel. |
| 376 | The |
| 377 | .Nm |
| 378 | program will be put in the background. |
| 379 | (This does not work if |
| 380 | .Nm |
| 381 | needs to ask for a password or passphrase; see also the |
| 382 | .Fl f |
| 383 | option.) |
Darren Tucker | e04644c | 2004-12-03 14:08:45 +1100 | [diff] [blame] | 384 | .It Fl O Ar ctl_cmd |
| 385 | Control an active connection multiplexing master process. |
| 386 | When the |
| 387 | .Fl O |
| 388 | option is specified, the |
| 389 | .Ar ctl_cmd |
| 390 | argument is interpreted and passed to the master process. |
| 391 | Valid commands are: |
| 392 | .Dq check |
Damien Miller | 388f6fc | 2010-05-21 14:57:35 +1000 | [diff] [blame] | 393 | (check that the master process is running), |
| 394 | .Dq forward |
Damien Miller | 8cb1cda | 2011-05-05 14:16:56 +1000 | [diff] [blame] | 395 | (request forwardings without command execution), |
Darren Tucker | e04644c | 2004-12-03 14:08:45 +1100 | [diff] [blame] | 396 | .Dq exit |
Damien Miller | 8cb1cda | 2011-05-05 14:16:56 +1000 | [diff] [blame] | 397 | (request the master to exit), and |
Damien Miller | 6c3eec7 | 2011-05-05 14:16:22 +1000 | [diff] [blame] | 398 | .Dq stop |
| 399 | (request the master to stop accepting further multiplexing requests). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 400 | .It Fl o Ar option |
Ben Lindstrom | 14c62eb | 2001-08-15 23:25:46 +0000 | [diff] [blame] | 401 | 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] | 402 | This is useful for specifying options for which there is no separate |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 403 | command-line flag. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 404 | For full details of the options listed below, and their possible values, see |
| 405 | .Xr ssh_config 5 . |
| 406 | .Pp |
| 407 | .Bl -tag -width Ds -offset indent -compact |
| 408 | .It AddressFamily |
| 409 | .It BatchMode |
| 410 | .It BindAddress |
| 411 | .It ChallengeResponseAuthentication |
| 412 | .It CheckHostIP |
| 413 | .It Cipher |
| 414 | .It Ciphers |
| 415 | .It ClearAllForwardings |
| 416 | .It Compression |
| 417 | .It CompressionLevel |
| 418 | .It ConnectionAttempts |
Darren Tucker | edae0ec | 2004-05-02 22:15:52 +1000 | [diff] [blame] | 419 | .It ConnectTimeout |
Damien Miller | 0e220db | 2004-06-15 10:34:08 +1000 | [diff] [blame] | 420 | .It ControlMaster |
| 421 | .It ControlPath |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 422 | .It DynamicForward |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 423 | .It EscapeChar |
Darren Tucker | e7d4b19 | 2006-07-12 22:17:10 +1000 | [diff] [blame] | 424 | .It ExitOnForwardFailure |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 425 | .It ForwardAgent |
| 426 | .It ForwardX11 |
Darren Tucker | 0a118da | 2003-10-15 15:54:32 +1000 | [diff] [blame] | 427 | .It ForwardX11Trusted |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 428 | .It GatewayPorts |
| 429 | .It GlobalKnownHostsFile |
| 430 | .It GSSAPIAuthentication |
| 431 | .It GSSAPIDelegateCredentials |
Damien Miller | e177615 | 2005-03-01 21:47:37 +1100 | [diff] [blame] | 432 | .It HashKnownHosts |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 433 | .It Host |
| 434 | .It HostbasedAuthentication |
| 435 | .It HostKeyAlgorithms |
| 436 | .It HostKeyAlias |
| 437 | .It HostName |
| 438 | .It IdentityFile |
Damien Miller | bd394c3 | 2004-03-08 23:12:36 +1100 | [diff] [blame] | 439 | .It IdentitiesOnly |
Damien Miller | 0a18473 | 2010-11-20 15:21:03 +1100 | [diff] [blame] | 440 | .It IPQoS |
Darren Tucker | 636ca90 | 2004-11-05 20:22:00 +1100 | [diff] [blame] | 441 | .It KbdInteractiveDevices |
Damien Miller | 7fe2b1f | 2010-09-24 22:11:53 +1000 | [diff] [blame] | 442 | .It KexAlgorithms |
Damien Miller | d27b947 | 2005-12-13 19:29:02 +1100 | [diff] [blame] | 443 | .It LocalCommand |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 444 | .It LocalForward |
| 445 | .It LogLevel |
| 446 | .It MACs |
| 447 | .It NoHostAuthenticationForLocalhost |
| 448 | .It NumberOfPasswordPrompts |
| 449 | .It PasswordAuthentication |
Damien Miller | d27b947 | 2005-12-13 19:29:02 +1100 | [diff] [blame] | 450 | .It PermitLocalCommand |
Damien Miller | 7ea845e | 2010-02-12 09:21:02 +1100 | [diff] [blame] | 451 | .It PKCS11Provider |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 452 | .It Port |
| 453 | .It PreferredAuthentications |
| 454 | .It Protocol |
| 455 | .It ProxyCommand |
| 456 | .It PubkeyAuthentication |
Darren Tucker | 62388b2 | 2006-01-20 11:31:47 +1100 | [diff] [blame] | 457 | .It RekeyLimit |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 458 | .It RemoteForward |
Damien Miller | f4b32aa | 2011-05-15 08:47:43 +1000 | [diff] [blame] | 459 | .It RequestTTY |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 460 | .It RhostsRSAAuthentication |
| 461 | .It RSAAuthentication |
Darren Tucker | 7a6c066 | 2004-05-02 22:14:03 +1000 | [diff] [blame] | 462 | .It SendEnv |
Damien Miller | 509b010 | 2003-12-17 16:33:10 +1100 | [diff] [blame] | 463 | .It ServerAliveInterval |
| 464 | .It ServerAliveCountMax |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 465 | .It StrictHostKeyChecking |
Damien Miller | 12c150e | 2003-12-17 16:31:10 +1100 | [diff] [blame] | 466 | .It TCPKeepAlive |
Damien Miller | d27b947 | 2005-12-13 19:29:02 +1100 | [diff] [blame] | 467 | .It Tunnel |
| 468 | .It TunnelDevice |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 469 | .It UsePrivilegedPort |
| 470 | .It User |
| 471 | .It UserKnownHostsFile |
| 472 | .It VerifyHostKeyDNS |
Damien Miller | 8639920 | 2008-06-30 00:04:31 +1000 | [diff] [blame] | 473 | .It VisualHostKey |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 474 | .It XAuthLocation |
| 475 | .El |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 476 | .It Fl p Ar port |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 477 | Port to connect to on the remote host. |
| 478 | This can be specified on a |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 479 | per-host basis in the configuration file. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 480 | .It Fl q |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 481 | Quiet mode. |
Damien Miller | eb60247 | 2008-02-10 22:21:28 +1100 | [diff] [blame] | 482 | Causes most warning and diagnostic messages to be suppressed. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 483 | .It Fl R Xo |
| 484 | .Sm off |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 485 | .Oo Ar bind_address : Oc |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 486 | .Ar port : host : hostport |
| 487 | .Sm on |
| 488 | .Xc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 489 | 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] | 490 | forwarded to the given host and port on the local side. |
| 491 | This works by allocating a socket to listen to |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 492 | .Ar port |
| 493 | on the remote side, and whenever a connection is made to this port, the |
| 494 | connection is forwarded over the secure channel, and a connection is |
| 495 | made to |
Damien Miller | 34132e5 | 2000-01-14 15:45:46 +1100 | [diff] [blame] | 496 | .Ar host |
| 497 | port |
| 498 | .Ar hostport |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 499 | from the local machine. |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 500 | .Pp |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 501 | Port forwardings can also be specified in the configuration file. |
| 502 | Privileged ports can be forwarded only when |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 503 | logging in as root on the remote machine. |
Damien Miller | 7fa9660 | 2010-08-05 13:03:13 +1000 | [diff] [blame] | 504 | IPv6 addresses can be specified by enclosing the address in square braces. |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 505 | .Pp |
| 506 | By default, the listening socket on the server will be bound to the loopback |
| 507 | interface only. |
Darren Tucker | 63917bd | 2008-11-11 16:33:48 +1100 | [diff] [blame] | 508 | This may be overridden by specifying a |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 509 | .Ar bind_address . |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 510 | An empty |
| 511 | .Ar bind_address , |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 512 | or the address |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 513 | .Ql * , |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 514 | indicates that the remote socket should listen on all interfaces. |
| 515 | Specifying a remote |
| 516 | .Ar bind_address |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 517 | will only succeed if the server's |
| 518 | .Cm GatewayPorts |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 519 | option is enabled (see |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 520 | .Xr sshd_config 5 ) . |
Damien Miller | e2f4cc5 | 2009-02-14 16:33:49 +1100 | [diff] [blame] | 521 | .Pp |
| 522 | If the |
| 523 | .Ar port |
| 524 | argument is |
Damien Miller | 65fa4ca | 2009-02-14 16:34:05 +1100 | [diff] [blame] | 525 | .Ql 0 , |
Damien Miller | e2f4cc5 | 2009-02-14 16:33:49 +1100 | [diff] [blame] | 526 | the listen port will be dynamically allocated on the server and reported |
| 527 | to the client at run time. |
Damien Miller | 388f6fc | 2010-05-21 14:57:35 +1000 | [diff] [blame] | 528 | When used together with |
| 529 | .Ic -O forward |
| 530 | the allocated port will be printed to the standard output. |
Darren Tucker | 7ebfc10 | 2004-11-07 20:06:19 +1100 | [diff] [blame] | 531 | .It Fl S Ar ctl_path |
Damien Miller | 67f30d7 | 2010-04-16 15:52:03 +1000 | [diff] [blame] | 532 | Specifies the location of a control socket for connection sharing, |
Damien Miller | 9c60f24 | 2010-03-26 11:28:35 +1100 | [diff] [blame] | 533 | or the string |
| 534 | .Dq none |
| 535 | to disable connection sharing. |
Damien Miller | 0e220db | 2004-06-15 10:34:08 +1000 | [diff] [blame] | 536 | Refer to the description of |
Darren Tucker | ba5c592 | 2004-06-18 16:22:39 +1000 | [diff] [blame] | 537 | .Cm ControlPath |
| 538 | and |
Damien Miller | 0e220db | 2004-06-15 10:34:08 +1000 | [diff] [blame] | 539 | .Cm ControlMaster |
| 540 | in |
| 541 | .Xr ssh_config 5 |
| 542 | for details. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 543 | .It Fl s |
| 544 | May be used to request invocation of a subsystem on the remote system. |
| 545 | Subsystems are a feature of the SSH2 protocol which facilitate the use |
| 546 | of SSH as a secure transport for other applications (eg.\& |
| 547 | .Xr sftp 1 ) . |
| 548 | The subsystem is specified as the remote command. |
| 549 | .It Fl T |
| 550 | Disable pseudo-tty allocation. |
| 551 | .It Fl t |
| 552 | Force pseudo-tty allocation. |
| 553 | This can be used to execute arbitrary |
| 554 | screen-based programs on a remote machine, which can be very useful, |
Damien Miller | 208f1ed | 2006-03-15 11:56:03 +1100 | [diff] [blame] | 555 | e.g. when implementing menu services. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 556 | Multiple |
| 557 | .Fl t |
| 558 | options force tty allocation, even if |
Ben Lindstrom | 19ceb17 | 2001-09-12 17:54:24 +0000 | [diff] [blame] | 559 | .Nm |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 560 | has no local tty. |
| 561 | .It Fl V |
| 562 | Display the version number and exit. |
| 563 | .It Fl v |
| 564 | Verbose mode. |
| 565 | Causes |
Ben Lindstrom | 5ab6ae1 | 2001-02-10 22:08:03 +0000 | [diff] [blame] | 566 | .Nm |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 567 | to print debugging messages about its progress. |
| 568 | This is helpful in |
| 569 | debugging connection, authentication, and configuration problems. |
| 570 | Multiple |
| 571 | .Fl v |
| 572 | options increase the verbosity. |
| 573 | The maximum is 3. |
Darren Tucker | 7ad8dd2 | 2010-01-12 19:40:27 +1100 | [diff] [blame] | 574 | .It Fl W Ar host : Ns Ar port |
| 575 | Requests that standard input and output on the client be forwarded to |
| 576 | .Ar host |
| 577 | on |
| 578 | .Ar port |
| 579 | over the secure channel. |
| 580 | Implies |
| 581 | .Fl N , |
| 582 | .Fl T , |
| 583 | .Cm ExitOnForwardFailure |
| 584 | and |
| 585 | .Cm ClearAllForwardings |
| 586 | and works with Protocol version 2 only. |
Damien Miller | 991dba4 | 2006-07-10 20:16:27 +1000 | [diff] [blame] | 587 | .It Fl w Xo |
| 588 | .Ar local_tun Ns Op : Ns Ar remote_tun |
| 589 | .Xc |
| 590 | Requests |
| 591 | tunnel |
| 592 | device forwarding with the specified |
Damien Miller | d27b947 | 2005-12-13 19:29:02 +1100 | [diff] [blame] | 593 | .Xr tun 4 |
Damien Miller | 991dba4 | 2006-07-10 20:16:27 +1000 | [diff] [blame] | 594 | devices between the client |
| 595 | .Pq Ar local_tun |
| 596 | and the server |
| 597 | .Pq Ar remote_tun . |
| 598 | .Pp |
Damien Miller | cf1e342 | 2005-12-24 14:56:04 +1100 | [diff] [blame] | 599 | The devices may be specified by numerical ID or the keyword |
| 600 | .Dq any , |
| 601 | which uses the next available tunnel device. |
Damien Miller | 991dba4 | 2006-07-10 20:16:27 +1000 | [diff] [blame] | 602 | If |
| 603 | .Ar remote_tun |
| 604 | is not specified, it defaults to |
| 605 | .Dq any . |
Damien Miller | cf1e342 | 2005-12-24 14:56:04 +1100 | [diff] [blame] | 606 | See also the |
Damien Miller | d27b947 | 2005-12-13 19:29:02 +1100 | [diff] [blame] | 607 | .Cm Tunnel |
Damien Miller | 991dba4 | 2006-07-10 20:16:27 +1000 | [diff] [blame] | 608 | and |
| 609 | .Cm TunnelDevice |
| 610 | directives in |
Damien Miller | d27b947 | 2005-12-13 19:29:02 +1100 | [diff] [blame] | 611 | .Xr ssh_config 5 . |
Damien Miller | 991dba4 | 2006-07-10 20:16:27 +1000 | [diff] [blame] | 612 | If the |
| 613 | .Cm Tunnel |
| 614 | directive is unset, it is set to the default tunnel mode, which is |
| 615 | .Dq point-to-point . |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 616 | .It Fl X |
| 617 | Enables X11 forwarding. |
| 618 | This can also be specified on a per-host basis in a configuration file. |
| 619 | .Pp |
| 620 | X11 forwarding should be enabled with caution. |
| 621 | Users with the ability to bypass file permissions on the remote host |
| 622 | (for the user's X authorization database) |
| 623 | can access the local X11 display through the forwarded connection. |
| 624 | 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] | 625 | .Pp |
Damien Miller | b022b23 | 2005-03-05 11:22:36 +1100 | [diff] [blame] | 626 | For this reason, X11 forwarding is subjected to X11 SECURITY extension |
Damien Miller | 947219e | 2005-03-02 13:22:30 +1100 | [diff] [blame] | 627 | restrictions by default. |
| 628 | Please refer to the |
| 629 | .Nm |
| 630 | .Fl Y |
| 631 | option and the |
| 632 | .Cm ForwardX11Trusted |
| 633 | directive in |
| 634 | .Xr ssh_config 5 |
| 635 | for more information. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 636 | .It Fl x |
| 637 | Disables X11 forwarding. |
Darren Tucker | 0a118da | 2003-10-15 15:54:32 +1000 | [diff] [blame] | 638 | .It Fl Y |
| 639 | Enables trusted X11 forwarding. |
Damien Miller | 947219e | 2005-03-02 13:22:30 +1100 | [diff] [blame] | 640 | Trusted X11 forwardings are not subjected to the X11 SECURITY extension |
| 641 | controls. |
Damien Miller | e272a5b | 2008-11-03 19:22:37 +1100 | [diff] [blame] | 642 | .It Fl y |
| 643 | Send log information using the |
| 644 | .Xr syslog 3 |
| 645 | system module. |
| 646 | By default this information is sent to stderr. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 647 | .El |
Damien Miller | e9b333a | 2005-12-24 14:53:04 +1100 | [diff] [blame] | 648 | .Pp |
| 649 | .Nm |
| 650 | may additionally obtain configuration data from |
| 651 | a per-user configuration file and a system-wide configuration file. |
| 652 | The file format and configuration options are described in |
| 653 | .Xr ssh_config 5 . |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 654 | .Sh AUTHENTICATION |
Darren Tucker | 94299ec | 2006-01-20 11:30:14 +1100 | [diff] [blame] | 655 | The OpenSSH SSH client supports SSH protocols 1 and 2. |
Darren Tucker | 7a4a765 | 2009-10-11 21:51:40 +1100 | [diff] [blame] | 656 | The default is to use protocol 2 only, |
| 657 | though this can be changed via the |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 658 | .Cm Protocol |
| 659 | option in |
Darren Tucker | 7a4a765 | 2009-10-11 21:51:40 +1100 | [diff] [blame] | 660 | .Xr ssh_config 5 |
| 661 | or the |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 662 | .Fl 1 |
| 663 | and |
| 664 | .Fl 2 |
| 665 | options (see above). |
| 666 | Both protocols support similar authentication methods, |
Darren Tucker | 7a4a765 | 2009-10-11 21:51:40 +1100 | [diff] [blame] | 667 | but protocol 2 is the default since |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 668 | it provides additional mechanisms for confidentiality |
| 669 | (the traffic is encrypted using AES, 3DES, Blowfish, CAST128, or Arcfour) |
Damien Miller | 20bd453 | 2011-08-06 06:17:30 +1000 | [diff] [blame^] | 670 | and integrity (hmac-md5, hmac-sha1, |
| 671 | hmac-sha2-256, hmac-sha2-512, |
| 672 | umac-64, hmac-ripemd160). |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 673 | Protocol 1 lacks a strong mechanism for ensuring the |
| 674 | integrity of the connection. |
| 675 | .Pp |
| 676 | The methods available for authentication are: |
Damien Miller | fbc94c8 | 2006-06-13 13:03:16 +1000 | [diff] [blame] | 677 | GSSAPI-based authentication, |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 678 | host-based authentication, |
| 679 | public key authentication, |
| 680 | challenge-response authentication, |
| 681 | and password authentication. |
| 682 | Authentication methods are tried in the order specified above, |
| 683 | though protocol 2 has a configuration option to change the default order: |
| 684 | .Cm PreferredAuthentications . |
| 685 | .Pp |
| 686 | Host-based authentication works as follows: |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 687 | If the machine the user logs in from is listed in |
| 688 | .Pa /etc/hosts.equiv |
| 689 | or |
| 690 | .Pa /etc/shosts.equiv |
| 691 | on the remote machine, and the user names are |
| 692 | the same on both sides, or if the files |
| 693 | .Pa ~/.rhosts |
| 694 | or |
| 695 | .Pa ~/.shosts |
| 696 | exist in the user's home directory on the |
| 697 | remote machine and contain a line containing the name of the client |
| 698 | 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] | 699 | considered for login. |
| 700 | Additionally, the server |
| 701 | .Em must |
| 702 | be able to verify the client's |
| 703 | host key (see the description of |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 704 | .Pa /etc/ssh/ssh_known_hosts |
| 705 | and |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 706 | .Pa ~/.ssh/known_hosts , |
| 707 | below) |
| 708 | for login to be permitted. |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 709 | This authentication method closes security holes due to IP |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 710 | spoofing, DNS spoofing, and routing spoofing. |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 711 | [Note to the administrator: |
| 712 | .Pa /etc/hosts.equiv , |
| 713 | .Pa ~/.rhosts , |
| 714 | and the rlogin/rsh protocol in general, are inherently insecure and should be |
| 715 | disabled if security is desired.] |
| 716 | .Pp |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 717 | Public key authentication works as follows: |
| 718 | The scheme is based on public-key cryptography, |
| 719 | using cryptosystems |
| 720 | where encryption and decryption are done using separate keys, |
| 721 | 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] | 722 | The idea is that each user creates a public/private |
| 723 | key pair for authentication purposes. |
| 724 | 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] | 725 | .Nm |
| 726 | implements public key authentication protocol automatically, |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 727 | using one of the DSA, ECDSA or RSA algorithms. |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 728 | Protocol 1 is restricted to using only RSA keys, |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 729 | but protocol 2 may use any. |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 730 | The |
| 731 | .Sx HISTORY |
| 732 | section of |
| 733 | .Xr ssl 8 |
Damien Miller | d442790 | 2010-09-10 11:15:10 +1000 | [diff] [blame] | 734 | contains a brief discussion of the DSA and RSA algorithms. |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 735 | .Pp |
| 736 | The file |
| 737 | .Pa ~/.ssh/authorized_keys |
| 738 | lists the public keys that are permitted for logging in. |
| 739 | When the user logs in, the |
| 740 | .Nm |
| 741 | program tells the server which key pair it would like to use for |
| 742 | authentication. |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 743 | The client proves that it has access to the private key |
| 744 | and the server checks that the corresponding public key |
| 745 | is authorized to accept the account. |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 746 | .Pp |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 747 | The user creates his/her key pair by running |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 748 | .Xr ssh-keygen 1 . |
| 749 | This stores the private key in |
| 750 | .Pa ~/.ssh/identity |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 751 | (protocol 1), |
| 752 | .Pa ~/.ssh/id_dsa |
| 753 | (protocol 2 DSA), |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 754 | .Pa ~/.ssh/id_ecdsa |
| 755 | (protocol 2 ECDSA), |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 756 | or |
| 757 | .Pa ~/.ssh/id_rsa |
| 758 | (protocol 2 RSA) |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 759 | and stores the public key in |
| 760 | .Pa ~/.ssh/identity.pub |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 761 | (protocol 1), |
| 762 | .Pa ~/.ssh/id_dsa.pub |
| 763 | (protocol 2 DSA), |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 764 | .Pa ~/.ssh/id_ecdsa.pub |
| 765 | (protocol 2 ECDSA), |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 766 | or |
| 767 | .Pa ~/.ssh/id_rsa.pub |
| 768 | (protocol 2 RSA) |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 769 | in the user's home directory. |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 770 | The user should then copy the public key |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 771 | to |
| 772 | .Pa ~/.ssh/authorized_keys |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 773 | in his/her home directory on the remote machine. |
| 774 | The |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 775 | .Pa authorized_keys |
| 776 | file corresponds to the conventional |
| 777 | .Pa ~/.rhosts |
| 778 | file, and has one key |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 779 | per line, though the lines can be very long. |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 780 | After this, the user can log in without giving the password. |
| 781 | .Pp |
Damien Miller | 922b541 | 2010-03-05 21:30:54 +1100 | [diff] [blame] | 782 | A variation on public key authentication |
| 783 | is available in the form of certificate authentication: |
| 784 | instead of a set of public/private keys, |
| 785 | signed certificates are used. |
| 786 | This has the advantage that a single trusted certification authority |
| 787 | can be used in place of many public/private keys. |
| 788 | See the |
| 789 | .Sx CERTIFICATES |
| 790 | section of |
| 791 | .Xr ssh-keygen 1 |
| 792 | for more information. |
| 793 | .Pp |
| 794 | The most convenient way to use public key or certificate authentication |
| 795 | may be with an authentication agent. |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 796 | See |
| 797 | .Xr ssh-agent 1 |
| 798 | for more information. |
| 799 | .Pp |
Damien Miller | c93a813 | 2005-12-24 14:52:13 +1100 | [diff] [blame] | 800 | Challenge-response authentication works as follows: |
| 801 | The server sends an arbitrary |
| 802 | .Qq challenge |
| 803 | text, and prompts for a response. |
| 804 | Protocol 2 allows multiple challenges and responses; |
| 805 | protocol 1 is restricted to just one challenge/response. |
| 806 | Examples of challenge-response authentication include |
| 807 | BSD Authentication (see |
| 808 | .Xr login.conf 5 ) |
| 809 | and PAM (some non-OpenBSD systems). |
| 810 | .Pp |
| 811 | Finally, if other authentication methods fail, |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 812 | .Nm |
| 813 | prompts the user for a password. |
| 814 | The password is sent to the remote |
| 815 | host for checking; however, since all communications are encrypted, |
| 816 | the password cannot be seen by someone listening on the network. |
Damien Miller | 48c94ab | 2006-01-02 23:38:00 +1100 | [diff] [blame] | 817 | .Pp |
| 818 | .Nm |
| 819 | automatically maintains and checks a database containing |
| 820 | identification for all hosts it has ever been used with. |
| 821 | Host keys are stored in |
| 822 | .Pa ~/.ssh/known_hosts |
| 823 | in the user's home directory. |
| 824 | Additionally, the file |
| 825 | .Pa /etc/ssh/ssh_known_hosts |
| 826 | is automatically checked for known hosts. |
| 827 | Any new hosts are automatically added to the user's file. |
| 828 | If a host's identification ever changes, |
| 829 | .Nm |
| 830 | warns about this and disables password authentication to prevent |
| 831 | server spoofing or man-in-the-middle attacks, |
| 832 | which could otherwise be used to circumvent the encryption. |
| 833 | The |
| 834 | .Cm StrictHostKeyChecking |
| 835 | option can be used to control logins to machines whose |
| 836 | host key is not known or has changed. |
| 837 | .Pp |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 838 | When the user's identity has been accepted by the server, the server |
| 839 | either executes the given command, or logs into the machine and gives |
| 840 | the user a normal shell on the remote machine. |
| 841 | All communication with |
| 842 | the remote command or shell will be automatically encrypted. |
| 843 | .Pp |
| 844 | If a pseudo-terminal has been allocated (normal login session), the |
| 845 | user may use the escape characters noted below. |
| 846 | .Pp |
| 847 | If no pseudo-tty has been allocated, |
| 848 | the session is transparent and can be used to reliably transfer binary data. |
| 849 | On most systems, setting the escape character to |
| 850 | .Dq none |
| 851 | will also make the session transparent even if a tty is used. |
| 852 | .Pp |
| 853 | The session terminates when the command or shell on the remote |
Damien Miller | 8bfaf93 | 2006-01-14 10:09:30 +1100 | [diff] [blame] | 854 | machine exits and all X11 and TCP connections have been closed. |
Damien Miller | 52d2061 | 2005-12-24 14:52:36 +1100 | [diff] [blame] | 855 | .Sh ESCAPE CHARACTERS |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 856 | When a pseudo-terminal has been requested, |
| 857 | .Nm |
| 858 | supports a number of functions through the use of an escape character. |
| 859 | .Pp |
| 860 | A single tilde character can be sent as |
| 861 | .Ic ~~ |
| 862 | or by following the tilde by a character other than those described below. |
| 863 | The escape character must always follow a newline to be interpreted as |
| 864 | special. |
| 865 | The escape character can be changed in configuration files using the |
| 866 | .Cm EscapeChar |
| 867 | configuration directive or on the command line by the |
| 868 | .Fl e |
| 869 | option. |
| 870 | .Pp |
| 871 | The supported escapes (assuming the default |
| 872 | .Ql ~ ) |
| 873 | are: |
| 874 | .Bl -tag -width Ds |
| 875 | .It Cm ~. |
| 876 | Disconnect. |
| 877 | .It Cm ~^Z |
| 878 | Background |
Damien Miller | 1164c29 | 2006-01-02 23:38:37 +1100 | [diff] [blame] | 879 | .Nm . |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 880 | .It Cm ~# |
| 881 | List forwarded connections. |
| 882 | .It Cm ~& |
| 883 | Background |
| 884 | .Nm |
| 885 | at logout when waiting for forwarded connection / X11 sessions to terminate. |
| 886 | .It Cm ~? |
| 887 | Display a list of escape characters. |
| 888 | .It Cm ~B |
| 889 | Send a BREAK to the remote system |
| 890 | (only useful for SSH protocol version 2 and if the peer supports it). |
| 891 | .It Cm ~C |
| 892 | Open command line. |
| 893 | Currently this allows the addition of port forwardings using the |
Damien Miller | 0164cb8 | 2008-11-05 16:30:31 +1100 | [diff] [blame] | 894 | .Fl L , |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 895 | .Fl R |
Damien Miller | 0164cb8 | 2008-11-05 16:30:31 +1100 | [diff] [blame] | 896 | and |
| 897 | .Fl D |
Damien Miller | 329cb01 | 2005-12-24 14:53:23 +1100 | [diff] [blame] | 898 | options (see above). |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 899 | It also allows the cancellation of existing remote port-forwardings |
| 900 | using |
Damien Miller | 57e8ad3 | 2006-07-10 20:20:52 +1000 | [diff] [blame] | 901 | .Sm off |
| 902 | .Fl KR Oo Ar bind_address : Oc Ar port . |
| 903 | .Sm on |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 904 | .Ic !\& Ns Ar command |
| 905 | allows the user to execute a local command if the |
| 906 | .Ic PermitLocalCommand |
| 907 | option is enabled in |
| 908 | .Xr ssh_config 5 . |
| 909 | Basic help is available, using the |
| 910 | .Fl h |
| 911 | option. |
| 912 | .It Cm ~R |
| 913 | Request rekeying of the connection |
| 914 | (only useful for SSH protocol version 2 and if the peer supports it). |
| 915 | .El |
Damien Miller | f317718 | 2006-01-14 10:09:13 +1100 | [diff] [blame] | 916 | .Sh TCP FORWARDING |
| 917 | Forwarding of arbitrary TCP connections over the secure channel can |
| 918 | be specified either on the command line or in a configuration file. |
| 919 | One possible application of TCP forwarding is a secure connection to a |
| 920 | mail server; another is going through firewalls. |
| 921 | .Pp |
| 922 | In the example below, we look at encrypting communication between |
| 923 | an IRC client and server, even though the IRC server does not directly |
| 924 | support encrypted communications. |
| 925 | This works as follows: |
| 926 | the user connects to the remote host using |
| 927 | .Nm , |
| 928 | specifying a port to be used to forward connections |
| 929 | to the remote server. |
| 930 | After that it is possible to start the service which is to be encrypted |
| 931 | on the client machine, |
| 932 | connecting to the same local port, |
| 933 | and |
| 934 | .Nm |
| 935 | will encrypt and forward the connection. |
| 936 | .Pp |
| 937 | The following example tunnels an IRC session from client machine |
| 938 | .Dq 127.0.0.1 |
| 939 | (localhost) |
| 940 | to remote server |
| 941 | .Dq server.example.com : |
| 942 | .Bd -literal -offset 4n |
| 943 | $ ssh -f -L 1234:localhost:6667 server.example.com sleep 10 |
| 944 | $ irc -c '#users' -p 1234 pinky 127.0.0.1 |
| 945 | .Ed |
| 946 | .Pp |
| 947 | This tunnels a connection to IRC server |
| 948 | .Dq server.example.com , |
| 949 | joining channel |
| 950 | .Dq #users , |
| 951 | nickname |
| 952 | .Dq pinky , |
| 953 | using port 1234. |
| 954 | It doesn't matter which port is used, |
| 955 | as long as it's greater than 1023 |
| 956 | (remember, only root can open sockets on privileged ports) |
| 957 | and doesn't conflict with any ports already in use. |
| 958 | The connection is forwarded to port 6667 on the remote server, |
| 959 | since that's the standard port for IRC services. |
| 960 | .Pp |
| 961 | The |
| 962 | .Fl f |
| 963 | option backgrounds |
| 964 | .Nm |
| 965 | and the remote command |
| 966 | .Dq sleep 10 |
| 967 | is specified to allow an amount of time |
| 968 | (10 seconds, in the example) |
| 969 | to start the service which is to be tunnelled. |
| 970 | If no connections are made within the time specified, |
| 971 | .Nm |
| 972 | will exit. |
Damien Miller | f317718 | 2006-01-14 10:09:13 +1100 | [diff] [blame] | 973 | .Sh X11 FORWARDING |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 974 | If the |
| 975 | .Cm ForwardX11 |
| 976 | variable is set to |
| 977 | .Dq yes |
| 978 | (or see the description of the |
Damien Miller | d7f308f | 2005-12-24 14:55:16 +1100 | [diff] [blame] | 979 | .Fl X , |
| 980 | .Fl x , |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 981 | and |
Damien Miller | d7f308f | 2005-12-24 14:55:16 +1100 | [diff] [blame] | 982 | .Fl Y |
Damien Miller | 9a765b2 | 2005-12-24 14:53:44 +1100 | [diff] [blame] | 983 | options above) |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 984 | and the user is using X11 (the |
| 985 | .Ev DISPLAY |
| 986 | environment variable is set), the connection to the X11 display is |
| 987 | automatically forwarded to the remote side in such a way that any X11 |
| 988 | programs started from the shell (or command) will go through the |
| 989 | encrypted channel, and the connection to the real X server will be made |
| 990 | from the local machine. |
| 991 | The user should not manually set |
| 992 | .Ev DISPLAY . |
| 993 | Forwarding of X11 connections can be |
| 994 | configured on the command line or in configuration files. |
| 995 | .Pp |
| 996 | The |
| 997 | .Ev DISPLAY |
| 998 | value set by |
| 999 | .Nm |
| 1000 | will point to the server machine, but with a display number greater than zero. |
| 1001 | This is normal, and happens because |
| 1002 | .Nm |
| 1003 | creates a |
| 1004 | .Dq proxy |
| 1005 | X server on the server machine for forwarding the |
| 1006 | connections over the encrypted channel. |
| 1007 | .Pp |
| 1008 | .Nm |
| 1009 | will also automatically set up Xauthority data on the server machine. |
| 1010 | For this purpose, it will generate a random authorization cookie, |
| 1011 | store it in Xauthority on the server, and verify that any forwarded |
| 1012 | connections carry this cookie and replace it by the real cookie when |
| 1013 | the connection is opened. |
| 1014 | The real authentication cookie is never |
| 1015 | sent to the server machine (and no cookies are sent in the plain). |
| 1016 | .Pp |
| 1017 | If the |
| 1018 | .Cm ForwardAgent |
| 1019 | variable is set to |
| 1020 | .Dq yes |
| 1021 | (or see the description of the |
| 1022 | .Fl A |
| 1023 | and |
| 1024 | .Fl a |
Damien Miller | 9a765b2 | 2005-12-24 14:53:44 +1100 | [diff] [blame] | 1025 | options above) and |
Darren Tucker | d3877b9 | 2005-12-20 16:09:36 +1100 | [diff] [blame] | 1026 | the user is using an authentication agent, the connection to the agent |
| 1027 | is automatically forwarded to the remote side. |
Damien Miller | bbc5909 | 2006-01-31 21:46:51 +1100 | [diff] [blame] | 1028 | .Sh VERIFYING HOST KEYS |
| 1029 | When connecting to a server for the first time, |
| 1030 | a fingerprint of the server's public key is presented to the user |
| 1031 | (unless the option |
| 1032 | .Cm StrictHostKeyChecking |
| 1033 | has been disabled). |
| 1034 | Fingerprints can be determined using |
| 1035 | .Xr ssh-keygen 1 : |
| 1036 | .Pp |
| 1037 | .Dl $ ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key |
| 1038 | .Pp |
Darren Tucker | f6bffb1 | 2008-06-14 09:04:26 +1000 | [diff] [blame] | 1039 | If the fingerprint is already known, it can be matched |
| 1040 | and the key can be accepted or rejected. |
| 1041 | Because of the difficulty of comparing host keys |
| 1042 | just by looking at hex strings, |
| 1043 | there is also support to compare host keys visually, |
| 1044 | using |
| 1045 | .Em random art . |
| 1046 | By setting the |
Damien Miller | 1028824 | 2008-06-30 00:04:03 +1000 | [diff] [blame] | 1047 | .Cm VisualHostKey |
Darren Tucker | f6bffb1 | 2008-06-14 09:04:26 +1000 | [diff] [blame] | 1048 | option to |
Damien Miller | 1028824 | 2008-06-30 00:04:03 +1000 | [diff] [blame] | 1049 | .Dq yes , |
Darren Tucker | f6bffb1 | 2008-06-14 09:04:26 +1000 | [diff] [blame] | 1050 | a small ASCII graphic gets displayed on every login to a server, no matter |
| 1051 | if the session itself is interactive or not. |
| 1052 | By learning the pattern a known server produces, a user can easily |
| 1053 | find out that the host key has changed when a completely different pattern |
| 1054 | is displayed. |
| 1055 | Because these patterns are not unambiguous however, a pattern that looks |
| 1056 | similar to the pattern remembered only gives a good probability that the |
| 1057 | host key is the same, not guaranteed proof. |
| 1058 | .Pp |
| 1059 | To get a listing of the fingerprints along with their random art for |
| 1060 | all known hosts, the following command line can be used: |
| 1061 | .Pp |
| 1062 | .Dl $ ssh-keygen -lv -f ~/.ssh/known_hosts |
| 1063 | .Pp |
Damien Miller | bbc5909 | 2006-01-31 21:46:51 +1100 | [diff] [blame] | 1064 | If the fingerprint is unknown, |
| 1065 | an alternative method of verification is available: |
| 1066 | SSH fingerprints verified by DNS. |
| 1067 | An additional resource record (RR), |
| 1068 | SSHFP, |
| 1069 | is added to a zonefile |
| 1070 | and the connecting client is able to match the fingerprint |
| 1071 | with that of the key presented. |
| 1072 | .Pp |
| 1073 | In this example, we are connecting a client to a server, |
| 1074 | .Dq host.example.com . |
| 1075 | The SSHFP resource records should first be added to the zonefile for |
| 1076 | host.example.com: |
| 1077 | .Bd -literal -offset indent |
Damien Miller | a1b3d63 | 2006-03-26 00:07:02 +1100 | [diff] [blame] | 1078 | $ ssh-keygen -r host.example.com. |
Damien Miller | bbc5909 | 2006-01-31 21:46:51 +1100 | [diff] [blame] | 1079 | .Ed |
| 1080 | .Pp |
| 1081 | The output lines will have to be added to the zonefile. |
| 1082 | To check that the zone is answering fingerprint queries: |
| 1083 | .Pp |
| 1084 | .Dl $ dig -t SSHFP host.example.com |
| 1085 | .Pp |
| 1086 | Finally the client connects: |
| 1087 | .Bd -literal -offset indent |
| 1088 | $ ssh -o "VerifyHostKeyDNS ask" host.example.com |
| 1089 | [...] |
| 1090 | Matching host key fingerprint found in DNS. |
| 1091 | Are you sure you want to continue connecting (yes/no)? |
| 1092 | .Ed |
| 1093 | .Pp |
| 1094 | See the |
| 1095 | .Cm VerifyHostKeyDNS |
| 1096 | option in |
| 1097 | .Xr ssh_config 5 |
| 1098 | for more information. |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1099 | .Sh SSH-BASED VIRTUAL PRIVATE NETWORKS |
| 1100 | .Nm |
| 1101 | contains support for Virtual Private Network (VPN) tunnelling |
| 1102 | using the |
| 1103 | .Xr tun 4 |
| 1104 | network pseudo-device, |
| 1105 | allowing two networks to be joined securely. |
| 1106 | The |
| 1107 | .Xr sshd_config 5 |
| 1108 | configuration option |
| 1109 | .Cm PermitTunnel |
| 1110 | controls whether the server supports this, |
| 1111 | and at what level (layer 2 or 3 traffic). |
| 1112 | .Pp |
| 1113 | The following example would connect client network 10.0.50.0/24 |
Damien Miller | 3975ee2 | 2006-11-05 05:31:33 +1100 | [diff] [blame] | 1114 | with remote network 10.0.99.0/24 using a point-to-point connection |
| 1115 | from 10.1.1.1 to 10.1.1.2, |
| 1116 | provided that the SSH server running on the gateway to the remote network, |
| 1117 | at 192.168.1.15, allows it. |
| 1118 | .Pp |
| 1119 | On the client: |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1120 | .Bd -literal -offset indent |
| 1121 | # ssh -f -w 0:1 192.168.1.15 true |
Damien Miller | 3975ee2 | 2006-11-05 05:31:33 +1100 | [diff] [blame] | 1122 | # ifconfig tun0 10.1.1.1 10.1.1.2 netmask 255.255.255.252 |
| 1123 | # route add 10.0.99.0/24 10.1.1.2 |
| 1124 | .Ed |
| 1125 | .Pp |
| 1126 | On the server: |
| 1127 | .Bd -literal -offset indent |
| 1128 | # ifconfig tun1 10.1.1.2 10.1.1.1 netmask 255.255.255.252 |
| 1129 | # route add 10.0.50.0/24 10.1.1.1 |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1130 | .Ed |
| 1131 | .Pp |
| 1132 | Client access may be more finely tuned via the |
| 1133 | .Pa /root/.ssh/authorized_keys |
| 1134 | file (see below) and the |
| 1135 | .Cm PermitRootLogin |
| 1136 | server option. |
Damien Miller | e93eaaa | 2006-03-15 11:05:59 +1100 | [diff] [blame] | 1137 | The following entry would permit connections on |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1138 | .Xr tun 4 |
Damien Miller | e93eaaa | 2006-03-15 11:05:59 +1100 | [diff] [blame] | 1139 | device 1 from user |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1140 | .Dq jane |
Damien Miller | e93eaaa | 2006-03-15 11:05:59 +1100 | [diff] [blame] | 1141 | and on tun device 2 from user |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1142 | .Dq john , |
| 1143 | if |
| 1144 | .Cm PermitRootLogin |
| 1145 | is set to |
| 1146 | .Dq forced-commands-only : |
| 1147 | .Bd -literal -offset 2n |
| 1148 | tunnel="1",command="sh /etc/netstart tun1" ssh-rsa ... jane |
Damien Miller | 9f67a21 | 2006-03-15 11:05:35 +1100 | [diff] [blame] | 1149 | tunnel="2",command="sh /etc/netstart tun2" ssh-rsa ... john |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1150 | .Ed |
| 1151 | .Pp |
Darren Tucker | ffe88e1 | 2006-10-18 07:53:06 +1000 | [diff] [blame] | 1152 | Since an SSH-based setup entails a fair amount of overhead, |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1153 | it may be more suited to temporary setups, |
| 1154 | such as for wireless VPNs. |
| 1155 | More permanent VPNs are better provided by tools such as |
| 1156 | .Xr ipsecctl 8 |
| 1157 | and |
| 1158 | .Xr isakmpd 8 . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1159 | .Sh ENVIRONMENT |
| 1160 | .Nm |
| 1161 | will normally set the following environment variables: |
Damien Miller | 6aa2290 | 2006-01-06 14:48:34 +1100 | [diff] [blame] | 1162 | .Bl -tag -width "SSH_ORIGINAL_COMMAND" |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1163 | .It Ev DISPLAY |
| 1164 | The |
| 1165 | .Ev DISPLAY |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1166 | variable indicates the location of the X11 server. |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 1167 | It is automatically set by |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1168 | .Nm |
| 1169 | to point to a value of the form |
Damien Miller | 14af93e | 2006-01-02 23:38:21 +1100 | [diff] [blame] | 1170 | .Dq hostname:n , |
| 1171 | where |
| 1172 | .Dq hostname |
| 1173 | indicates the host where the shell runs, and |
| 1174 | .Sq n |
| 1175 | is an integer \*(Ge 1. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1176 | .Nm |
| 1177 | uses this special value to forward X11 connections over the secure |
| 1178 | channel. |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 1179 | The user should normally not set |
| 1180 | .Ev DISPLAY |
| 1181 | explicitly, as that |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1182 | will render the X11 connection insecure (and will require the user to |
| 1183 | manually copy any required authorization cookies). |
| 1184 | .It Ev HOME |
| 1185 | Set to the path of the user's home directory. |
| 1186 | .It Ev LOGNAME |
| 1187 | Synonym for |
| 1188 | .Ev USER ; |
| 1189 | set for compatibility with systems that use this variable. |
| 1190 | .It Ev MAIL |
Ben Lindstrom | e59433d | 2001-09-12 16:41:37 +0000 | [diff] [blame] | 1191 | Set to the path of the user's mailbox. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1192 | .It Ev PATH |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1193 | Set to the default |
| 1194 | .Ev PATH , |
| 1195 | as specified when compiling |
Damien Miller | 1164c29 | 2006-01-02 23:38:37 +1100 | [diff] [blame] | 1196 | .Nm . |
Ben Lindstrom | 5bf5d67 | 2001-07-04 04:31:38 +0000 | [diff] [blame] | 1197 | .It Ev SSH_ASKPASS |
| 1198 | If |
| 1199 | .Nm |
| 1200 | needs a passphrase, it will read the passphrase from the current |
| 1201 | terminal if it was run from a terminal. |
| 1202 | If |
| 1203 | .Nm |
| 1204 | does not have a terminal associated with it but |
| 1205 | .Ev DISPLAY |
| 1206 | and |
| 1207 | .Ev SSH_ASKPASS |
| 1208 | are set, it will execute the program specified by |
| 1209 | .Ev SSH_ASKPASS |
| 1210 | and open an X11 window to read the passphrase. |
| 1211 | This is particularly useful when calling |
| 1212 | .Nm |
| 1213 | from a |
Darren Tucker | 4e4fe00 | 2004-11-05 20:01:03 +1100 | [diff] [blame] | 1214 | .Pa .xsession |
Ben Lindstrom | 5bf5d67 | 2001-07-04 04:31:38 +0000 | [diff] [blame] | 1215 | or related script. |
| 1216 | (Note that on some machines it |
| 1217 | may be necessary to redirect the input from |
| 1218 | .Pa /dev/null |
| 1219 | to make this work.) |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1220 | .It Ev SSH_AUTH_SOCK |
Damien Miller | 14af93e | 2006-01-02 23:38:21 +1100 | [diff] [blame] | 1221 | Identifies the path of a |
| 1222 | .Ux Ns -domain |
| 1223 | socket used to communicate with the agent. |
Damien Miller | f37e246 | 2002-09-19 11:47:55 +1000 | [diff] [blame] | 1224 | .It Ev SSH_CONNECTION |
| 1225 | Identifies the client and server ends of the connection. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1226 | The variable contains |
Damien Miller | 14af93e | 2006-01-02 23:38:21 +1100 | [diff] [blame] | 1227 | four space-separated values: client IP address, client port number, |
| 1228 | server IP address, and server port number. |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 1229 | .It Ev SSH_ORIGINAL_COMMAND |
Damien Miller | 14af93e | 2006-01-02 23:38:21 +1100 | [diff] [blame] | 1230 | This variable contains the original command line if a forced command |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 1231 | is executed. |
| 1232 | It can be used to extract the original arguments. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1233 | .It Ev SSH_TTY |
| 1234 | 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] | 1235 | with the current shell or command. |
| 1236 | If the current session has no tty, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1237 | this variable is not set. |
| 1238 | .It Ev TZ |
Damien Miller | 6dbdb6a | 2005-12-13 19:25:43 +1100 | [diff] [blame] | 1239 | This variable is set to indicate the present time zone if it |
Damien Miller | 208f1ed | 2006-03-15 11:56:03 +1100 | [diff] [blame] | 1240 | 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] | 1241 | on to new connections). |
| 1242 | .It Ev USER |
| 1243 | Set to the name of the user logging in. |
| 1244 | .El |
| 1245 | .Pp |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 1246 | Additionally, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1247 | .Nm |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 1248 | reads |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1249 | .Pa ~/.ssh/environment , |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1250 | and adds lines of the format |
| 1251 | .Dq VARNAME=value |
Damien Miller | 14af93e | 2006-01-02 23:38:21 +1100 | [diff] [blame] | 1252 | to the environment if the file exists and users are allowed to |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 1253 | change their environment. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 1254 | For more information, see the |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 1255 | .Cm PermitUserEnvironment |
Ben Lindstrom | bd9bf38 | 2002-08-20 18:54:20 +0000 | [diff] [blame] | 1256 | option in |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 1257 | .Xr sshd_config 5 . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1258 | .Sh FILES |
Damien Miller | 7655f5c | 2006-01-06 14:48:18 +1100 | [diff] [blame] | 1259 | .Bl -tag -width Ds -compact |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1260 | .It Pa ~/.rhosts |
Damien Miller | 1bcdb50 | 2006-01-06 14:49:38 +1100 | [diff] [blame] | 1261 | This file is used for host-based authentication (see above). |
Ben Lindstrom | ebd888d | 2001-03-05 05:49:29 +0000 | [diff] [blame] | 1262 | On some machines this file may need to be |
Damien Miller | 1bcdb50 | 2006-01-06 14:49:38 +1100 | [diff] [blame] | 1263 | 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] | 1264 | because |
| 1265 | .Xr sshd 8 |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1266 | reads it as root. |
| 1267 | Additionally, this file must be owned by the user, |
| 1268 | and must not have write permissions for anyone else. |
| 1269 | The recommended |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1270 | permission for most machines is read/write for the user, and not |
| 1271 | accessible by others. |
| 1272 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1273 | .It Pa ~/.shosts |
Damien Miller | 1bcdb50 | 2006-01-06 14:49:38 +1100 | [diff] [blame] | 1274 | This file is used in exactly the same way as |
| 1275 | .Pa .rhosts , |
| 1276 | but allows host-based authentication without permitting login with |
| 1277 | rlogin/rsh. |
Damien Miller | 7655f5c | 2006-01-06 14:48:18 +1100 | [diff] [blame] | 1278 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1279 | .It Pa ~/.ssh/ |
Damien Miller | 520e615 | 2008-02-10 22:46:22 +1100 | [diff] [blame] | 1280 | This directory is the default location for all user-specific configuration |
| 1281 | and authentication information. |
| 1282 | There is no general requirement to keep the entire contents of this directory |
| 1283 | secret, but the recommended permissions are read/write/execute for the user, |
| 1284 | and not accessible by others. |
| 1285 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1286 | .It Pa ~/.ssh/authorized_keys |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 1287 | Lists the public keys (DSA/ECDSA/RSA) that can be used for logging in as |
| 1288 | this user. |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1289 | The format of this file is described in the |
| 1290 | .Xr sshd 8 |
| 1291 | manual page. |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1292 | This file is not highly sensitive, but the recommended |
| 1293 | permissions are read/write for the user, and not accessible by others. |
| 1294 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1295 | .It Pa ~/.ssh/config |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1296 | This is the per-user configuration file. |
| 1297 | The file format and configuration options are described in |
| 1298 | .Xr ssh_config 5 . |
| 1299 | Because of the potential for abuse, this file must have strict permissions: |
| 1300 | read/write for the user, and not accessible by others. |
| 1301 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1302 | .It Pa ~/.ssh/environment |
Damien Miller | 4c102ee | 2006-01-06 14:49:17 +1100 | [diff] [blame] | 1303 | Contains additional definitions for environment variables; see |
| 1304 | .Sx ENVIRONMENT , |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1305 | above. |
| 1306 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1307 | .It Pa ~/.ssh/identity |
| 1308 | .It Pa ~/.ssh/id_dsa |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 1309 | .It Pa ~/.ssh/id_ecdsa |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1310 | .It Pa ~/.ssh/id_rsa |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1311 | Contains the private key for authentication. |
| 1312 | These files |
| 1313 | contain sensitive data and should be readable by the user but not |
| 1314 | accessible by others (read/write/execute). |
| 1315 | .Nm |
| 1316 | will simply ignore a private key file if it is accessible by others. |
| 1317 | It is possible to specify a passphrase when |
| 1318 | generating the key which will be used to encrypt the |
| 1319 | sensitive part of this file using 3DES. |
| 1320 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1321 | .It Pa ~/.ssh/identity.pub |
| 1322 | .It Pa ~/.ssh/id_dsa.pub |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 1323 | .It Pa ~/.ssh/id_ecdsa.pub |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1324 | .It Pa ~/.ssh/id_rsa.pub |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1325 | Contains the public key for authentication. |
| 1326 | These files are not |
| 1327 | sensitive and can (but need not) be readable by anyone. |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1328 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1329 | .It Pa ~/.ssh/known_hosts |
Damien Miller | e87eb4c | 2006-01-14 10:08:36 +1100 | [diff] [blame] | 1330 | Contains a list of host keys for all hosts the user has logged into |
| 1331 | that are not already in the systemwide list of known host keys. |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1332 | See |
Damien Miller | e87eb4c | 2006-01-14 10:08:36 +1100 | [diff] [blame] | 1333 | .Xr sshd 8 |
| 1334 | for further details of the format of this file. |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1335 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1336 | .It Pa ~/.ssh/rc |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1337 | Commands in this file are executed by |
| 1338 | .Nm |
Damien Miller | 7e76e1f | 2006-01-14 10:08:57 +1100 | [diff] [blame] | 1339 | 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] | 1340 | started. |
| 1341 | See the |
| 1342 | .Xr sshd 8 |
| 1343 | manual page for more information. |
| 1344 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1345 | .It Pa /etc/hosts.equiv |
Damien Miller | 1bcdb50 | 2006-01-06 14:49:38 +1100 | [diff] [blame] | 1346 | This file is for host-based authentication (see above). |
| 1347 | It should only be writable by root. |
Damien Miller | 7655f5c | 2006-01-06 14:48:18 +1100 | [diff] [blame] | 1348 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1349 | .It Pa /etc/shosts.equiv |
Damien Miller | 1bcdb50 | 2006-01-06 14:49:38 +1100 | [diff] [blame] | 1350 | This file is used in exactly the same way as |
| 1351 | .Pa hosts.equiv , |
| 1352 | but allows host-based authentication without permitting login with |
| 1353 | rlogin/rsh. |
Damien Miller | 7655f5c | 2006-01-06 14:48:18 +1100 | [diff] [blame] | 1354 | .Pp |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1355 | .It Pa /etc/ssh/ssh_config |
| 1356 | Systemwide configuration file. |
| 1357 | The file format and configuration options are described in |
| 1358 | .Xr ssh_config 5 . |
| 1359 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1360 | .It Pa /etc/ssh/ssh_host_key |
| 1361 | .It Pa /etc/ssh/ssh_host_dsa_key |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 1362 | .It Pa /etc/ssh/ssh_host_ecdsa_key |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1363 | .It Pa /etc/ssh/ssh_host_rsa_key |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1364 | These three files contain the private parts of the host keys |
Damien Miller | 7e76e1f | 2006-01-14 10:08:57 +1100 | [diff] [blame] | 1365 | and are used for host-based authentication. |
| 1366 | If protocol version 1 is used, |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1367 | .Nm |
| 1368 | must be setuid root, since the host key is readable only by root. |
| 1369 | For protocol version 2, |
| 1370 | .Nm |
| 1371 | uses |
| 1372 | .Xr ssh-keysign 8 |
Damien Miller | 7e76e1f | 2006-01-14 10:08:57 +1100 | [diff] [blame] | 1373 | to access the host keys, |
| 1374 | eliminating the requirement that |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1375 | .Nm |
Damien Miller | 7e76e1f | 2006-01-14 10:08:57 +1100 | [diff] [blame] | 1376 | be setuid root when host-based authentication is used. |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1377 | By default |
| 1378 | .Nm |
| 1379 | is not setuid root. |
| 1380 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1381 | .It Pa /etc/ssh/ssh_known_hosts |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1382 | Systemwide list of known host keys. |
| 1383 | This file should be prepared by the |
| 1384 | system administrator to contain the public host keys of all machines in the |
| 1385 | organization. |
Damien Miller | e87eb4c | 2006-01-14 10:08:36 +1100 | [diff] [blame] | 1386 | It should be world-readable. |
| 1387 | See |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1388 | .Xr sshd 8 |
Damien Miller | e87eb4c | 2006-01-14 10:08:36 +1100 | [diff] [blame] | 1389 | for further details of the format of this file. |
Damien Miller | fb8ea74 | 2006-01-06 14:48:52 +1100 | [diff] [blame] | 1390 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 1391 | .It Pa /etc/ssh/sshrc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1392 | Commands in this file are executed by |
| 1393 | .Nm |
Damien Miller | 7e76e1f | 2006-01-14 10:08:57 +1100 | [diff] [blame] | 1394 | 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] | 1395 | See the |
| 1396 | .Xr sshd 8 |
| 1397 | manual page for more information. |
Damien Miller | 7b28dc5 | 2000-09-05 13:34:53 +1100 | [diff] [blame] | 1398 | .El |
Damien Miller | daa7b22 | 2010-09-10 11:19:33 +1000 | [diff] [blame] | 1399 | .Sh EXIT STATUS |
| 1400 | .Nm |
| 1401 | exits with the exit status of the remote command or with 255 |
| 1402 | if an error occurred. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1403 | .Sh SEE ALSO |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1404 | .Xr scp 1 , |
Damien Miller | 3380426 | 2001-02-04 23:20:18 +1100 | [diff] [blame] | 1405 | .Xr sftp 1 , |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1406 | .Xr ssh-add 1 , |
| 1407 | .Xr ssh-agent 1 , |
| 1408 | .Xr ssh-keygen 1 , |
Damien Miller | 128a0f1 | 2006-01-06 14:50:11 +1100 | [diff] [blame] | 1409 | .Xr ssh-keyscan 1 , |
Darren Tucker | 248dd13 | 2006-01-20 11:30:58 +1100 | [diff] [blame] | 1410 | .Xr tun 4 , |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 1411 | .Xr hosts.equiv 5 , |
Ben Lindstrom | bf69e3b | 2002-06-23 00:31:24 +0000 | [diff] [blame] | 1412 | .Xr ssh_config 5 , |
Ben Lindstrom | c001cd3 | 2002-06-23 00:32:11 +0000 | [diff] [blame] | 1413 | .Xr ssh-keysign 8 , |
Ben Lindstrom | 5ab6ae1 | 2001-02-10 22:08:03 +0000 | [diff] [blame] | 1414 | .Xr sshd 8 |
Ben Lindstrom | 160ec62 | 2001-04-22 17:17:46 +0000 | [diff] [blame] | 1415 | .Rs |
Damien Miller | 39a93a3 | 2006-03-15 11:34:45 +1100 | [diff] [blame] | 1416 | .%R RFC 4250 |
| 1417 | .%T "The Secure Shell (SSH) Protocol Assigned Numbers" |
| 1418 | .%D 2006 |
| 1419 | .Re |
| 1420 | .Rs |
| 1421 | .%R RFC 4251 |
| 1422 | .%T "The Secure Shell (SSH) Protocol Architecture" |
| 1423 | .%D 2006 |
| 1424 | .Re |
| 1425 | .Rs |
| 1426 | .%R RFC 4252 |
| 1427 | .%T "The Secure Shell (SSH) Authentication Protocol" |
| 1428 | .%D 2006 |
| 1429 | .Re |
| 1430 | .Rs |
| 1431 | .%R RFC 4253 |
| 1432 | .%T "The Secure Shell (SSH) Transport Layer Protocol" |
| 1433 | .%D 2006 |
| 1434 | .Re |
| 1435 | .Rs |
| 1436 | .%R RFC 4254 |
| 1437 | .%T "The Secure Shell (SSH) Connection Protocol" |
| 1438 | .%D 2006 |
| 1439 | .Re |
| 1440 | .Rs |
| 1441 | .%R RFC 4255 |
| 1442 | .%T "Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints" |
| 1443 | .%D 2006 |
| 1444 | .Re |
| 1445 | .Rs |
| 1446 | .%R RFC 4256 |
| 1447 | .%T "Generic Message Exchange Authentication for the Secure Shell Protocol (SSH)" |
| 1448 | .%D 2006 |
| 1449 | .Re |
| 1450 | .Rs |
| 1451 | .%R RFC 4335 |
| 1452 | .%T "The Secure Shell (SSH) Session Channel Break Extension" |
| 1453 | .%D 2006 |
| 1454 | .Re |
| 1455 | .Rs |
| 1456 | .%R RFC 4344 |
| 1457 | .%T "The Secure Shell (SSH) Transport Layer Encryption Modes" |
| 1458 | .%D 2006 |
| 1459 | .Re |
| 1460 | .Rs |
| 1461 | .%R RFC 4345 |
| 1462 | .%T "Improved Arcfour Modes for the Secure Shell (SSH) Transport Layer Protocol" |
| 1463 | .%D 2006 |
Ben Lindstrom | 160ec62 | 2001-04-22 17:17:46 +0000 | [diff] [blame] | 1464 | .Re |
Damien Miller | 3e96d74 | 2006-03-25 23:39:29 +1100 | [diff] [blame] | 1465 | .Rs |
| 1466 | .%R RFC 4419 |
| 1467 | .%T "Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol" |
| 1468 | .%D 2006 |
| 1469 | .Re |
Damien Miller | c0367fb | 2007-01-05 16:25:46 +1100 | [diff] [blame] | 1470 | .Rs |
| 1471 | .%R RFC 4716 |
| 1472 | .%T "The Secure Shell (SSH) Public Key File Format" |
| 1473 | .%D 2006 |
| 1474 | .Re |
Darren Tucker | f6bffb1 | 2008-06-14 09:04:26 +1000 | [diff] [blame] | 1475 | .Rs |
Damien Miller | 1ca9469 | 2010-09-24 22:01:22 +1000 | [diff] [blame] | 1476 | .%R RFC 5656 |
| 1477 | .%T "Elliptic Curve Algorithm Integration in the Secure Shell Transport Layer" |
| 1478 | .%D 2009 |
| 1479 | .Re |
| 1480 | .Rs |
Darren Tucker | f6bffb1 | 2008-06-14 09:04:26 +1000 | [diff] [blame] | 1481 | .%T "Hash Visualization: a New Technique to improve Real-World Security" |
| 1482 | .%A A. Perrig |
| 1483 | .%A D. Song |
| 1484 | .%D 1999 |
| 1485 | .%O "International Workshop on Cryptographic Techniques and E-Commerce (CrypTEC '99)" |
| 1486 | .Re |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 1487 | .Sh AUTHORS |
| 1488 | OpenSSH is a derivative of the original and free |
| 1489 | ssh 1.2.12 release by Tatu Ylonen. |
| 1490 | Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, |
| 1491 | Theo de Raadt and Dug Song |
| 1492 | removed many bugs, re-added newer features and |
| 1493 | created OpenSSH. |
| 1494 | Markus Friedl contributed the support for SSH |
| 1495 | protocol versions 1.5 and 2.0. |