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 | .\" |
Darren Tucker | 1e4308e | 2005-10-03 18:18:40 +1000 | [diff] [blame] | 37 | .\" $OpenBSD: ssh.1,v 1.212 2005/09/19 23:31:31 djm Exp $ |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 38 | .Dd September 25, 1999 |
| 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 |
Darren Tucker | ba5c592 | 2004-06-18 16:22:39 +1000 | [diff] [blame] | 46 | .Op Fl 1246AaCfgkMNnqsTtVvXxY |
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 |
Darren Tucker | c8d6421 | 2005-10-03 18:13:42 +1000 | [diff] [blame] | 49 | .Oo Fl D\ \& |
| 50 | .Sm off |
| 51 | .Oo Ar bind_address : Oc |
| 52 | .Ar port |
| 53 | .Sm on |
| 54 | .Oc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 55 | .Op Fl e Ar escape_char |
Ben Lindstrom | 14f31ab | 2001-09-12 17:48:04 +0000 | [diff] [blame] | 56 | .Op Fl F Ar configfile |
Darren Tucker | 05d4dfe | 2005-10-03 18:17:38 +1000 | [diff] [blame] | 57 | .Bk -words |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 58 | .Op Fl i Ar identity_file |
Darren Tucker | 05d4dfe | 2005-10-03 18:17:38 +1000 | [diff] [blame] | 59 | .Ek |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 60 | .Oo Fl L\ \& |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 61 | .Sm off |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 62 | .Oo Ar bind_address : Oc |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 63 | .Ar port : host : hostport |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 64 | .Sm on |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 65 | .Oc |
Darren Tucker | 05d4dfe | 2005-10-03 18:17:38 +1000 | [diff] [blame] | 66 | .Bk -words |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 67 | .Op Fl l Ar login_name |
Darren Tucker | 05d4dfe | 2005-10-03 18:17:38 +1000 | [diff] [blame] | 68 | .Ek |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 69 | .Op Fl m Ar mac_spec |
Darren Tucker | 7ebfc10 | 2004-11-07 20:06:19 +1100 | [diff] [blame] | 70 | .Op Fl O Ar ctl_cmd |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 71 | .Op Fl o Ar option |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 72 | .Op Fl p Ar port |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 73 | .Oo Fl R\ \& |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 74 | .Sm off |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 75 | .Oo Ar bind_address : Oc |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 76 | .Ar port : host : hostport |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 77 | .Sm on |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 78 | .Oc |
Darren Tucker | 7ebfc10 | 2004-11-07 20:06:19 +1100 | [diff] [blame] | 79 | .Op Fl S Ar ctl_path |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 80 | .Oo Ar user Ns @ Oc Ns Ar hostname |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 81 | .Op Ar command |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 82 | .Sh DESCRIPTION |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 83 | .Nm |
Ben Lindstrom | d58eb5f | 2001-03-07 06:07:22 +0000 | [diff] [blame] | 84 | (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] | 85 | executing commands on a remote machine. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 86 | It is intended to replace rlogin and rsh, |
| 87 | and provide secure encrypted communications between |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 88 | two untrusted hosts over an insecure network. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 89 | X11 connections and arbitrary TCP/IP ports |
| 90 | can also be forwarded over the secure channel. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 91 | .Pp |
| 92 | .Nm |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 93 | connects and logs into the specified |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 94 | .Ar hostname |
| 95 | (with optional |
| 96 | .Ar user |
| 97 | name). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 98 | The user must prove |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 99 | his/her identity to the remote machine using one of several methods |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 100 | depending on the protocol version used. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 101 | .Pp |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 102 | If |
| 103 | .Ar command |
| 104 | is specified, |
| 105 | .Ar command |
| 106 | is executed on the remote host instead of a login shell. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 107 | .Ss SSH protocol version 1 |
Darren Tucker | db69390 | 2004-08-29 16:37:24 +1000 | [diff] [blame] | 108 | The first authentication method is the |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 109 | .Em rhosts |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 110 | or |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 111 | .Em hosts.equiv |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 112 | method combined with RSA-based host authentication. |
Darren Tucker | db69390 | 2004-08-29 16:37:24 +1000 | [diff] [blame] | 113 | If the machine the user logs in from is listed in |
| 114 | .Pa /etc/hosts.equiv |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 115 | or |
Darren Tucker | db69390 | 2004-08-29 16:37:24 +1000 | [diff] [blame] | 116 | .Pa /etc/shosts.equiv |
| 117 | on the remote machine, and the user names are |
| 118 | the same on both sides, or if the files |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 119 | .Pa ~/.rhosts |
Darren Tucker | db69390 | 2004-08-29 16:37:24 +1000 | [diff] [blame] | 120 | or |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 121 | .Pa ~/.shosts |
Darren Tucker | db69390 | 2004-08-29 16:37:24 +1000 | [diff] [blame] | 122 | exist in the user's home directory on the |
| 123 | remote machine and contain a line containing the name of the client |
| 124 | machine and the name of the user on that machine, the user is |
| 125 | considered for log in. |
| 126 | Additionally, if the server can verify the client's |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 127 | host key (see |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 128 | .Pa /etc/ssh/ssh_known_hosts |
Damien Miller | 33e511e | 1999-11-11 11:43:13 +1100 | [diff] [blame] | 129 | and |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 130 | .Pa ~/.ssh/known_hosts |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 131 | in the |
| 132 | .Sx FILES |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 133 | section), only then is login permitted. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 134 | This authentication method closes security holes due to IP |
| 135 | spoofing, DNS spoofing and routing spoofing. |
| 136 | [Note to the administrator: |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 137 | .Pa /etc/hosts.equiv , |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 138 | .Pa ~/.rhosts , |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 139 | and the rlogin/rsh protocol in general, are inherently insecure and should be |
| 140 | disabled if security is desired.] |
| 141 | .Pp |
Darren Tucker | db69390 | 2004-08-29 16:37:24 +1000 | [diff] [blame] | 142 | As a second authentication method, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 143 | .Nm |
| 144 | supports RSA based authentication. |
| 145 | The scheme is based on public-key cryptography: there are cryptosystems |
| 146 | where encryption and decryption are done using separate keys, and it |
| 147 | is not possible to derive the decryption key from the encryption key. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 148 | RSA is one such system. |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 149 | The idea is that each user creates a public/private |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 150 | key pair for authentication purposes. |
| 151 | The server knows the public key, and only the user knows the private key. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 152 | .Pp |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 153 | The file |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 154 | .Pa ~/.ssh/authorized_keys |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 155 | lists the public keys that are permitted for logging in. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 156 | When the user logs in, the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 157 | .Nm |
| 158 | program tells the server which key pair it would like to use for |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 159 | authentication. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 160 | The server checks if this key is permitted, and if so, |
| 161 | sends the user (actually the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 162 | .Nm |
| 163 | program running on behalf of the user) a challenge, a random number, |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 164 | encrypted by the user's public key. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 165 | The challenge can only be decrypted using the proper private key. |
| 166 | The user's client then decrypts the challenge using the private key, |
| 167 | proving that he/she knows the private key |
| 168 | but without disclosing it to the server. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 169 | .Pp |
| 170 | .Nm |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 171 | implements the RSA authentication protocol automatically. |
| 172 | The user creates his/her RSA key pair by running |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 173 | .Xr ssh-keygen 1 . |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 174 | This stores the private key in |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 175 | .Pa ~/.ssh/identity |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 176 | and stores the public key in |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 177 | .Pa ~/.ssh/identity.pub |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 178 | in the user's home directory. |
| 179 | The user should then copy the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 180 | .Pa identity.pub |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 181 | to |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 182 | .Pa ~/.ssh/authorized_keys |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 183 | in his/her home directory on the remote machine (the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 184 | .Pa authorized_keys |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 185 | file corresponds to the conventional |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 186 | .Pa ~/.rhosts |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 187 | file, and has one key |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 188 | per line, though the lines can be very long). |
| 189 | After this, the user can log in without giving the password. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 190 | .Pp |
| 191 | The most convenient way to use RSA authentication may be with an |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 192 | authentication agent. |
| 193 | See |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 194 | .Xr ssh-agent 1 |
| 195 | for more information. |
| 196 | .Pp |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 197 | If other authentication methods fail, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 198 | .Nm |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 199 | prompts the user for a password. |
| 200 | The password is sent to the remote |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 201 | host for checking; however, since all communications are encrypted, |
| 202 | the password cannot be seen by someone listening on the network. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 203 | .Ss SSH protocol version 2 |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 204 | When a user connects using protocol version 2, |
Damien Miller | 07a2d42 | 2002-02-05 12:16:15 +1100 | [diff] [blame] | 205 | similar authentication methods are available. |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 206 | Using the default values for |
| 207 | .Cm PreferredAuthentications , |
Ben Lindstrom | a9086a1 | 2001-08-06 20:58:51 +0000 | [diff] [blame] | 208 | the client will try to authenticate first using the hostbased method; |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 209 | if this method fails, public key authentication is attempted, |
| 210 | and finally if this method fails, keyboard-interactive and |
Ben Lindstrom | a9086a1 | 2001-08-06 20:58:51 +0000 | [diff] [blame] | 211 | password authentication are tried. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 212 | .Pp |
| 213 | The public key method is similar to RSA authentication described |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 214 | in the previous section and allows the RSA or DSA algorithm to be used: |
Ben Lindstrom | 18a82ac | 2001-04-11 15:59:35 +0000 | [diff] [blame] | 215 | The client uses his private key, |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 216 | .Pa ~/.ssh/id_dsa |
Ben Lindstrom | 18a82ac | 2001-04-11 15:59:35 +0000 | [diff] [blame] | 217 | or |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 218 | .Pa ~/.ssh/id_rsa , |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 219 | to sign the session identifier and sends the result to the server. |
| 220 | The server checks whether the matching public key is listed in |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 221 | .Pa ~/.ssh/authorized_keys |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 222 | and grants access if both the key is found and the signature is correct. |
| 223 | The session identifier is derived from a shared Diffie-Hellman value |
| 224 | and is only known to the client and the server. |
| 225 | .Pp |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 226 | If public key authentication fails or is not available, a password |
| 227 | can be sent encrypted to the remote host to prove the user's identity. |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 228 | .Pp |
| 229 | Additionally, |
| 230 | .Nm |
| 231 | supports hostbased or challenge response authentication. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 232 | .Pp |
| 233 | Protocol 2 provides additional mechanisms for confidentiality |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 234 | (the traffic is encrypted using AES, 3DES, Blowfish, CAST128 or Arcfour) |
| 235 | and integrity (hmac-md5, hmac-sha1, hmac-ripemd160). |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 236 | Note that protocol 1 lacks a strong mechanism for ensuring the |
| 237 | integrity of the connection. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 238 | .Ss Login session and remote execution |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 239 | When the user's identity has been accepted by the server, the server |
| 240 | either executes the given command, or logs into the machine and gives |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 241 | the user a normal shell on the remote machine. |
| 242 | All communication with |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 243 | the remote command or shell will be automatically encrypted. |
| 244 | .Pp |
| 245 | If a pseudo-terminal has been allocated (normal login session), the |
Ben Lindstrom | 9ffdcb5 | 2001-04-20 12:50:51 +0000 | [diff] [blame] | 246 | user may use the escape characters noted below. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 247 | .Pp |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 248 | If no pseudo-tty has been allocated, |
| 249 | the session is transparent and can be used to reliably transfer binary data. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 250 | On most systems, setting the escape character to |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 251 | .Dq none |
| 252 | will also make the session transparent even if a tty is used. |
| 253 | .Pp |
Ben Lindstrom | a688561 | 2000-12-09 03:45:32 +0000 | [diff] [blame] | 254 | The session terminates when the command or shell on the remote |
Ben Lindstrom | ebd888d | 2001-03-05 05:49:29 +0000 | [diff] [blame] | 255 | machine exits and all X11 and TCP/IP connections have been closed. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 256 | The exit status of the remote program is returned as the exit status of |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 257 | .Nm ssh . |
Ben Lindstrom | 9ffdcb5 | 2001-04-20 12:50:51 +0000 | [diff] [blame] | 258 | .Ss Escape Characters |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 259 | When a pseudo-terminal has been requested, |
| 260 | .Nm |
| 261 | supports a number of functions through the use of an escape character. |
Ben Lindstrom | 9ffdcb5 | 2001-04-20 12:50:51 +0000 | [diff] [blame] | 262 | .Pp |
| 263 | A single tilde character can be sent as |
| 264 | .Ic ~~ |
Ben Lindstrom | 6600769 | 2001-07-22 20:41:59 +0000 | [diff] [blame] | 265 | or by following the tilde by a character other than those described below. |
Ben Lindstrom | 9ffdcb5 | 2001-04-20 12:50:51 +0000 | [diff] [blame] | 266 | The escape character must always follow a newline to be interpreted as |
| 267 | special. |
| 268 | The escape character can be changed in configuration files using the |
| 269 | .Cm EscapeChar |
Ben Lindstrom | 2464322 | 2001-06-25 05:08:11 +0000 | [diff] [blame] | 270 | configuration directive or on the command line by the |
Ben Lindstrom | 9ffdcb5 | 2001-04-20 12:50:51 +0000 | [diff] [blame] | 271 | .Fl e |
| 272 | option. |
| 273 | .Pp |
| 274 | The supported escapes (assuming the default |
| 275 | .Ql ~ ) |
| 276 | are: |
| 277 | .Bl -tag -width Ds |
| 278 | .It Cm ~. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 279 | Disconnect. |
Ben Lindstrom | 9ffdcb5 | 2001-04-20 12:50:51 +0000 | [diff] [blame] | 280 | .It Cm ~^Z |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 281 | Background |
| 282 | .Nm ssh . |
Ben Lindstrom | 9ffdcb5 | 2001-04-20 12:50:51 +0000 | [diff] [blame] | 283 | .It Cm ~# |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 284 | List forwarded connections. |
Ben Lindstrom | 9ffdcb5 | 2001-04-20 12:50:51 +0000 | [diff] [blame] | 285 | .It Cm ~& |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 286 | Background |
| 287 | .Nm |
| 288 | at logout when waiting for forwarded connection / X11 sessions to terminate. |
Ben Lindstrom | 9ffdcb5 | 2001-04-20 12:50:51 +0000 | [diff] [blame] | 289 | .It Cm ~? |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 290 | Display a list of escape characters. |
Damien Miller | 54c4598 | 2003-05-15 10:20:13 +1000 | [diff] [blame] | 291 | .It Cm ~B |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 292 | Send a BREAK to the remote system |
| 293 | (only useful for SSH protocol version 2 and if the peer supports it). |
Ben Lindstrom | 5589f4b | 2002-03-22 03:24:32 +0000 | [diff] [blame] | 294 | .It Cm ~C |
Darren Tucker | e7066df | 2004-05-24 10:18:05 +1000 | [diff] [blame] | 295 | Open command line. |
| 296 | Currently this allows the addition of port forwardings using the |
Ben Lindstrom | 5589f4b | 2002-03-22 03:24:32 +0000 | [diff] [blame] | 297 | .Fl L |
| 298 | and |
| 299 | .Fl R |
Darren Tucker | e7066df | 2004-05-24 10:18:05 +1000 | [diff] [blame] | 300 | options (see below). |
Darren Tucker | e534e12 | 2004-05-24 10:35:14 +1000 | [diff] [blame] | 301 | It also allows the cancellation of existing remote port-forwardings |
Darren Tucker | e7066df | 2004-05-24 10:18:05 +1000 | [diff] [blame] | 302 | using |
| 303 | .Fl KR Ar hostport . |
Darren Tucker | 1973c88 | 2004-05-24 10:34:36 +1000 | [diff] [blame] | 304 | Basic help is available, using the |
| 305 | .Fl h |
Darren Tucker | e7066df | 2004-05-24 10:18:05 +1000 | [diff] [blame] | 306 | option. |
Ben Lindstrom | 9ffdcb5 | 2001-04-20 12:50:51 +0000 | [diff] [blame] | 307 | .It Cm ~R |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 308 | Request rekeying of the connection |
| 309 | (only useful for SSH protocol version 2 and if the peer supports it). |
Ben Lindstrom | 9ffdcb5 | 2001-04-20 12:50:51 +0000 | [diff] [blame] | 310 | .El |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 311 | .Ss X11 and TCP forwarding |
Ben Lindstrom | 7121507 | 2001-05-17 03:16:18 +0000 | [diff] [blame] | 312 | If the |
| 313 | .Cm ForwardX11 |
| 314 | variable is set to |
| 315 | .Dq yes |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 316 | (or see the description of the |
Ben Lindstrom | 7121507 | 2001-05-17 03:16:18 +0000 | [diff] [blame] | 317 | .Fl X |
| 318 | and |
| 319 | .Fl x |
| 320 | options described later) |
| 321 | and the user is using X11 (the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 322 | .Ev DISPLAY |
| 323 | environment variable is set), the connection to the X11 display is |
| 324 | automatically forwarded to the remote side in such a way that any X11 |
| 325 | programs started from the shell (or command) will go through the |
| 326 | encrypted channel, and the connection to the real X server will be made |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 327 | from the local machine. |
| 328 | The user should not manually set |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 329 | .Ev DISPLAY . |
| 330 | Forwarding of X11 connections can be |
| 331 | configured on the command line or in configuration files. |
| 332 | .Pp |
| 333 | The |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 334 | .Ev DISPLAY |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 335 | value set by |
| 336 | .Nm |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 337 | will point to the server machine, but with a display number greater than zero. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 338 | This is normal, and happens because |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 339 | .Nm |
| 340 | creates a |
| 341 | .Dq proxy |
| 342 | X server on the server machine for forwarding the |
| 343 | connections over the encrypted channel. |
| 344 | .Pp |
| 345 | .Nm |
| 346 | will also automatically set up Xauthority data on the server machine. |
| 347 | For this purpose, it will generate a random authorization cookie, |
| 348 | store it in Xauthority on the server, and verify that any forwarded |
| 349 | connections carry this cookie and replace it by the real cookie when |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 350 | the connection is opened. |
| 351 | The real authentication cookie is never |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 352 | sent to the server machine (and no cookies are sent in the plain). |
| 353 | .Pp |
Ben Lindstrom | 3541f18 | 2002-08-20 19:03:20 +0000 | [diff] [blame] | 354 | If the |
| 355 | .Cm ForwardAgent |
| 356 | variable is set to |
| 357 | .Dq yes |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 358 | (or see the description of the |
Ben Lindstrom | 3541f18 | 2002-08-20 19:03:20 +0000 | [diff] [blame] | 359 | .Fl A |
| 360 | and |
| 361 | .Fl a |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 362 | options described later) and |
Ben Lindstrom | 3541f18 | 2002-08-20 19:03:20 +0000 | [diff] [blame] | 363 | the user is using an authentication agent, the connection to the agent |
| 364 | is automatically forwarded to the remote side. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 365 | .Pp |
| 366 | Forwarding of arbitrary TCP/IP connections over the secure channel can |
Ben Lindstrom | 979c981 | 2001-07-22 20:45:39 +0000 | [diff] [blame] | 367 | be specified either on the command line or in a configuration file. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 368 | One possible application of TCP/IP forwarding is a secure connection to an |
Ben Lindstrom | ebd888d | 2001-03-05 05:49:29 +0000 | [diff] [blame] | 369 | electronic purse; another is going through firewalls. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 370 | .Ss Server authentication |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 371 | .Nm |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 372 | automatically maintains and checks a database containing |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 373 | identifications for all hosts it has ever been used with. |
Ben Lindstrom | d6481ea | 2001-06-25 04:37:41 +0000 | [diff] [blame] | 374 | Host keys are stored in |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 375 | .Pa ~/.ssh/known_hosts |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 376 | in the user's home directory. |
Ben Lindstrom | d6481ea | 2001-06-25 04:37:41 +0000 | [diff] [blame] | 377 | Additionally, the file |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 378 | .Pa /etc/ssh/ssh_known_hosts |
Ben Lindstrom | d6481ea | 2001-06-25 04:37:41 +0000 | [diff] [blame] | 379 | is automatically checked for known hosts. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 380 | Any new hosts are automatically added to the user's file. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 381 | If a host's identification ever changes, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 382 | .Nm |
| 383 | warns about this and disables password authentication to prevent a |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 384 | trojan horse from getting the user's password. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 385 | Another purpose of this mechanism is to prevent man-in-the-middle attacks |
| 386 | which could otherwise be used to circumvent the encryption. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 387 | The |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 388 | .Cm StrictHostKeyChecking |
Ben Lindstrom | 9f04903 | 2002-06-21 00:59:05 +0000 | [diff] [blame] | 389 | option can be used to prevent logins to machines whose |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 390 | host key is not known or has changed. |
Damien Miller | 0bc1bd8 | 2000-11-13 22:57:25 +1100 | [diff] [blame] | 391 | .Pp |
Darren Tucker | 0b42e6d | 2004-08-13 21:22:40 +1000 | [diff] [blame] | 392 | .Nm |
| 393 | can be configured to verify host identification using fingerprint resource |
| 394 | records (SSHFP) published in DNS. |
| 395 | The |
| 396 | .Cm VerifyHostKeyDNS |
| 397 | option can be used to control how DNS lookups are performed. |
| 398 | SSHFP resource records can be generated using |
| 399 | .Xr ssh-keygen 1 . |
| 400 | .Pp |
Damien Miller | 0bc1bd8 | 2000-11-13 22:57:25 +1100 | [diff] [blame] | 401 | The options are as follows: |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 402 | .Bl -tag -width Ds |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 403 | .It Fl 1 |
| 404 | Forces |
| 405 | .Nm |
| 406 | to try protocol version 1 only. |
| 407 | .It Fl 2 |
| 408 | Forces |
| 409 | .Nm |
| 410 | to try protocol version 2 only. |
| 411 | .It Fl 4 |
| 412 | Forces |
| 413 | .Nm |
| 414 | to use IPv4 addresses only. |
| 415 | .It Fl 6 |
| 416 | Forces |
| 417 | .Nm |
| 418 | to use IPv6 addresses only. |
Damien Miller | b1715dc | 2000-05-30 13:44:51 +1000 | [diff] [blame] | 419 | .It Fl A |
| 420 | Enables forwarding of the authentication agent connection. |
| 421 | 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] | 422 | .Pp |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 423 | Agent forwarding should be enabled with caution. |
| 424 | Users with the ability to bypass file permissions on the remote host |
| 425 | (for the agent's Unix-domain socket) |
| 426 | can access the local agent through the forwarded connection. |
| 427 | An attacker cannot obtain key material from the agent, |
Damien Miller | b5fdfaa | 2002-09-12 09:52:03 +1000 | [diff] [blame] | 428 | however they can perform operations on the keys that enable them to |
| 429 | authenticate using the identities loaded into the agent. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 430 | .It Fl a |
| 431 | Disables forwarding of the authentication agent connection. |
Ben Lindstrom | e0f8804 | 2001-04-30 13:06:24 +0000 | [diff] [blame] | 432 | .It Fl b Ar bind_address |
Darren Tucker | a5cf855 | 2005-07-14 17:04:18 +1000 | [diff] [blame] | 433 | Use |
| 434 | .Ar bind_address |
| 435 | on the local machine as the source address |
| 436 | of the connection. |
| 437 | Only useful on systems with more than one address. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 438 | .It Fl C |
| 439 | Requests compression of all data (including stdin, stdout, stderr, and |
| 440 | data for forwarded X11 and TCP/IP connections). |
| 441 | The compression algorithm is the same used by |
| 442 | .Xr gzip 1 , |
| 443 | and the |
| 444 | .Dq level |
| 445 | can be controlled by the |
| 446 | .Cm CompressionLevel |
| 447 | option for protocol version 1. |
| 448 | Compression is desirable on modem lines and other |
| 449 | slow connections, but will only slow down things on fast networks. |
| 450 | The default value can be set on a host-by-host basis in the |
| 451 | configuration files; see the |
| 452 | .Cm Compression |
| 453 | option. |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 454 | .It Fl c Ar cipher_spec |
| 455 | Selects the cipher specification for encrypting the session. |
| 456 | .Pp |
| 457 | Protocol version 1 allows specification of a single cipher. |
Darren Tucker | 1e4308e | 2005-10-03 18:18:40 +1000 | [diff] [blame] | 458 | The supported values are |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 459 | .Dq 3des , |
| 460 | .Dq blowfish |
| 461 | and |
| 462 | .Dq des . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 463 | .Ar 3des |
| 464 | (triple-des) is an encrypt-decrypt-encrypt triple with three different keys. |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 465 | It is believed to be secure. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 466 | .Ar blowfish |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 467 | 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] | 468 | .Ar 3des . |
Ben Lindstrom | ffa1dd6 | 2001-09-12 16:52:28 +0000 | [diff] [blame] | 469 | .Ar des |
| 470 | is only supported in the |
| 471 | .Nm |
| 472 | client for interoperability with legacy protocol 1 implementations |
| 473 | that do not support the |
| 474 | .Ar 3des |
Damien Miller | 495dca3 | 2003-04-01 21:42:14 +1000 | [diff] [blame] | 475 | cipher. |
| 476 | Its use is strongly discouraged due to cryptographic weaknesses. |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 477 | The default is |
| 478 | .Dq 3des . |
| 479 | .Pp |
| 480 | For protocol version 2 |
| 481 | .Ar cipher_spec |
| 482 | is a comma-separated list of ciphers |
| 483 | listed in order of preference. |
| 484 | The supported ciphers are |
| 485 | .Dq 3des-cbc , |
| 486 | .Dq aes128-cbc , |
| 487 | .Dq aes192-cbc , |
| 488 | .Dq aes256-cbc , |
| 489 | .Dq aes128-ctr , |
| 490 | .Dq aes192-ctr , |
| 491 | .Dq aes256-ctr , |
Damien Miller | 3710f27 | 2005-05-26 12:19:17 +1000 | [diff] [blame] | 492 | .Dq arcfour128 , |
| 493 | .Dq arcfour256 , |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 494 | .Dq arcfour , |
| 495 | .Dq blowfish-cbc , |
| 496 | and |
| 497 | .Dq cast128-cbc . |
| 498 | The default is |
| 499 | .Bd -literal |
Damien Miller | 3710f27 | 2005-05-26 12:19:17 +1000 | [diff] [blame] | 500 | ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128, |
| 501 | arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr, |
| 502 | aes192-ctr,aes256-ctr'' |
Damien Miller | 05202ff | 2004-06-15 10:30:39 +1000 | [diff] [blame] | 503 | .Ed |
Darren Tucker | c8d6421 | 2005-10-03 18:13:42 +1000 | [diff] [blame] | 504 | .It Fl D Xo |
| 505 | .Sm off |
| 506 | .Oo Ar bind_address : Oc |
| 507 | .Ar port |
| 508 | .Sm on |
| 509 | .Xc |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 510 | Specifies a local |
| 511 | .Dq dynamic |
| 512 | application-level port forwarding. |
| 513 | This works by allocating a socket to listen to |
| 514 | .Ar port |
Darren Tucker | c8d6421 | 2005-10-03 18:13:42 +1000 | [diff] [blame] | 515 | on the local side, optionally bound to the specified |
| 516 | .Ar bind_address . |
| 517 | Whenever a connection is made to this port, the |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 518 | connection is forwarded over the secure channel, and the application |
| 519 | protocol is then used to determine where to connect to from the |
| 520 | remote machine. |
| 521 | Currently the SOCKS4 and SOCKS5 protocols are supported, and |
| 522 | .Nm |
| 523 | will act as a SOCKS server. |
| 524 | Only root can forward privileged ports. |
| 525 | Dynamic port forwardings can also be specified in the configuration file. |
Darren Tucker | c8d6421 | 2005-10-03 18:13:42 +1000 | [diff] [blame] | 526 | .Pp |
| 527 | IPv6 addresses can be specified with an alternative syntax: |
| 528 | .Sm off |
| 529 | .Xo |
| 530 | .Op Ar bind_address No / |
| 531 | .Ar port |
| 532 | .Xc |
| 533 | .Sm on |
| 534 | or by enclosing the address in square brackets. |
| 535 | Only the superuser can forward privileged ports. |
| 536 | By default, the local port is bound in accordance with the |
| 537 | .Cm GatewayPorts |
| 538 | setting. |
| 539 | However, an explicit |
| 540 | .Ar bind_address |
| 541 | may be used to bind the connection to a specific address. |
| 542 | The |
| 543 | .Ar bind_address |
| 544 | of |
| 545 | .Dq localhost |
| 546 | indicates that the listening port be bound for local use only, while an |
| 547 | empty address or |
| 548 | .Sq * |
| 549 | indicates that the port should be available from all interfaces. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 550 | .It Fl e Ar ch | ^ch | none |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 551 | Sets the escape character for sessions with a pty (default: |
| 552 | .Ql ~ ) . |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 553 | The escape character is only recognized at the beginning of a line. |
| 554 | The escape character followed by a dot |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 555 | .Pq Ql \&. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 556 | closes the connection; |
| 557 | followed by control-Z suspends the connection; |
| 558 | and followed by itself sends the escape character once. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 559 | Setting the character to |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 560 | .Dq none |
| 561 | disables any escapes and makes the session fully transparent. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 562 | .It Fl F Ar configfile |
| 563 | Specifies an alternative per-user configuration file. |
| 564 | If a configuration file is given on the command line, |
| 565 | the system-wide configuration file |
| 566 | .Pq Pa /etc/ssh/ssh_config |
| 567 | will be ignored. |
| 568 | The default for the per-user configuration file is |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 569 | .Pa ~/.ssh/config . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 570 | .It Fl f |
| 571 | Requests |
| 572 | .Nm |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 573 | to go to background just before command execution. |
| 574 | This is useful if |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 575 | .Nm |
| 576 | is going to ask for passwords or passphrases, but the user |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 577 | wants it in the background. |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 578 | This implies |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 579 | .Fl n . |
| 580 | The recommended way to start X11 programs at a remote site is with |
| 581 | something like |
| 582 | .Ic ssh -f host xterm . |
Damien Miller | 396691a | 2000-01-20 22:44:08 +1100 | [diff] [blame] | 583 | .It Fl g |
| 584 | Allows remote hosts to connect to local forwarded ports. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 585 | .It Fl I Ar smartcard_device |
| 586 | Specifies which smartcard device to use. |
| 587 | The argument is the device |
| 588 | .Nm |
| 589 | should use to communicate with a smartcard used for storing the user's |
| 590 | private RSA key. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 591 | .It Fl i Ar identity_file |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 592 | Selects a file from which the identity (private key) for |
Damien Miller | 0bc1bd8 | 2000-11-13 22:57:25 +1100 | [diff] [blame] | 593 | RSA or DSA authentication is read. |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 594 | The default is |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 595 | .Pa ~/.ssh/identity |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 596 | for protocol version 1, and |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 597 | .Pa ~/.ssh/id_rsa |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 598 | and |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 599 | .Pa ~/.ssh/id_dsa |
Damien Miller | fae2386 | 2002-01-22 23:32:26 +1100 | [diff] [blame] | 600 | for protocol version 2. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 601 | Identity files may also be specified on |
| 602 | a per-host basis in the configuration file. |
| 603 | It is possible to have multiple |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 604 | .Fl i |
| 605 | options (and multiple identities specified in |
| 606 | configuration files). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 607 | .It Fl k |
Damien Miller | e0113cc | 2003-11-24 13:10:09 +1100 | [diff] [blame] | 608 | Disables forwarding (delegation) of GSSAPI credentials to the server. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 609 | .It Fl L Xo |
| 610 | .Sm off |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 611 | .Oo Ar bind_address : Oc |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 612 | .Ar port : host : hostport |
| 613 | .Sm on |
| 614 | .Xc |
| 615 | Specifies that the given port on the local (client) host is to be |
| 616 | forwarded to the given host and port on the remote side. |
| 617 | This works by allocating a socket to listen to |
| 618 | .Ar port |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 619 | on the local side, optionally bound to the specified |
| 620 | .Ar bind_address . |
| 621 | Whenever a connection is made to this port, the |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 622 | connection is forwarded over the secure channel, and a connection is |
| 623 | made to |
| 624 | .Ar host |
| 625 | port |
| 626 | .Ar hostport |
| 627 | from the remote machine. |
| 628 | Port forwardings can also be specified in the configuration file. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 629 | IPv6 addresses can be specified with an alternative syntax: |
| 630 | .Sm off |
| 631 | .Xo |
Damien Miller | b096ac4 | 2005-03-09 11:00:05 +1100 | [diff] [blame] | 632 | .Op Ar bind_address No / |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 633 | .Ar port No / Ar host No / |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 634 | .Ar hostport |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 635 | .Xc |
| 636 | .Sm on |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 637 | or by enclosing the address in square brackets. |
| 638 | Only the superuser can forward privileged ports. |
| 639 | By default, the local port is bound in accordance with the |
| 640 | .Cm GatewayPorts |
| 641 | setting. |
| 642 | However, an explicit |
| 643 | .Ar bind_address |
| 644 | may be used to bind the connection to a specific address. |
| 645 | The |
| 646 | .Ar bind_address |
| 647 | of |
| 648 | .Dq localhost |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 649 | indicates that the listening port be bound for local use only, while an |
| 650 | empty address or |
| 651 | .Sq * |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 652 | indicates that the port should be available from all interfaces. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 653 | .It Fl l Ar login_name |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 654 | Specifies the user to log in as on the remote machine. |
| 655 | 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] | 656 | .It Fl M |
| 657 | Places the |
| 658 | .Nm |
| 659 | client into |
| 660 | .Dq master |
| 661 | mode for connection sharing. |
| 662 | Refer to the description of |
| 663 | .Cm ControlMaster |
| 664 | in |
| 665 | .Xr ssh_config 5 |
| 666 | for details. |
Damien Miller | 5d1eceb | 2004-06-30 22:37:57 +1000 | [diff] [blame] | 667 | .It Fl m Ar mac_spec |
| 668 | Additionally, for protocol version 2 a comma-separated list of MAC |
| 669 | (message authentication code) algorithms can |
| 670 | be specified in order of preference. |
| 671 | See the |
| 672 | .Cm MACs |
| 673 | keyword for more information. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 674 | .It Fl N |
| 675 | Do not execute a remote command. |
| 676 | This is useful for just forwarding ports |
| 677 | (protocol version 2 only). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 678 | .It Fl n |
| 679 | Redirects stdin from |
| 680 | .Pa /dev/null |
| 681 | (actually, prevents reading from stdin). |
| 682 | This must be used when |
| 683 | .Nm |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 684 | is run in the background. |
| 685 | A common trick is to use this to run X11 programs on a remote machine. |
| 686 | For example, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 687 | .Ic ssh -n shadows.cs.hut.fi emacs & |
| 688 | will start an emacs on shadows.cs.hut.fi, and the X11 |
| 689 | connection will be automatically forwarded over an encrypted channel. |
| 690 | The |
| 691 | .Nm |
| 692 | program will be put in the background. |
| 693 | (This does not work if |
| 694 | .Nm |
| 695 | needs to ask for a password or passphrase; see also the |
| 696 | .Fl f |
| 697 | option.) |
Darren Tucker | e04644c | 2004-12-03 14:08:45 +1100 | [diff] [blame] | 698 | .It Fl O Ar ctl_cmd |
| 699 | Control an active connection multiplexing master process. |
| 700 | When the |
| 701 | .Fl O |
| 702 | option is specified, the |
| 703 | .Ar ctl_cmd |
| 704 | argument is interpreted and passed to the master process. |
| 705 | Valid commands are: |
| 706 | .Dq check |
| 707 | (check that the master process is running) and |
| 708 | .Dq exit |
| 709 | (request the master to exit). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 710 | .It Fl o Ar option |
Ben Lindstrom | 14c62eb | 2001-08-15 23:25:46 +0000 | [diff] [blame] | 711 | 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] | 712 | This is useful for specifying options for which there is no separate |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 713 | command-line flag. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 714 | For full details of the options listed below, and their possible values, see |
| 715 | .Xr ssh_config 5 . |
| 716 | .Pp |
| 717 | .Bl -tag -width Ds -offset indent -compact |
| 718 | .It AddressFamily |
| 719 | .It BatchMode |
| 720 | .It BindAddress |
| 721 | .It ChallengeResponseAuthentication |
| 722 | .It CheckHostIP |
| 723 | .It Cipher |
| 724 | .It Ciphers |
| 725 | .It ClearAllForwardings |
| 726 | .It Compression |
| 727 | .It CompressionLevel |
| 728 | .It ConnectionAttempts |
Darren Tucker | edae0ec | 2004-05-02 22:15:52 +1000 | [diff] [blame] | 729 | .It ConnectTimeout |
Damien Miller | 0e220db | 2004-06-15 10:34:08 +1000 | [diff] [blame] | 730 | .It ControlMaster |
| 731 | .It ControlPath |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 732 | .It DynamicForward |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 733 | .It EscapeChar |
| 734 | .It ForwardAgent |
| 735 | .It ForwardX11 |
Darren Tucker | 0a118da | 2003-10-15 15:54:32 +1000 | [diff] [blame] | 736 | .It ForwardX11Trusted |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 737 | .It GatewayPorts |
| 738 | .It GlobalKnownHostsFile |
| 739 | .It GSSAPIAuthentication |
| 740 | .It GSSAPIDelegateCredentials |
Damien Miller | e177615 | 2005-03-01 21:47:37 +1100 | [diff] [blame] | 741 | .It HashKnownHosts |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 742 | .It Host |
| 743 | .It HostbasedAuthentication |
| 744 | .It HostKeyAlgorithms |
| 745 | .It HostKeyAlias |
| 746 | .It HostName |
| 747 | .It IdentityFile |
Damien Miller | bd394c3 | 2004-03-08 23:12:36 +1100 | [diff] [blame] | 748 | .It IdentitiesOnly |
Darren Tucker | 636ca90 | 2004-11-05 20:22:00 +1100 | [diff] [blame] | 749 | .It KbdInteractiveDevices |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 750 | .It LocalForward |
| 751 | .It LogLevel |
| 752 | .It MACs |
| 753 | .It NoHostAuthenticationForLocalhost |
| 754 | .It NumberOfPasswordPrompts |
| 755 | .It PasswordAuthentication |
| 756 | .It Port |
| 757 | .It PreferredAuthentications |
| 758 | .It Protocol |
| 759 | .It ProxyCommand |
| 760 | .It PubkeyAuthentication |
| 761 | .It RemoteForward |
| 762 | .It RhostsRSAAuthentication |
| 763 | .It RSAAuthentication |
Darren Tucker | 7a6c066 | 2004-05-02 22:14:03 +1000 | [diff] [blame] | 764 | .It SendEnv |
Damien Miller | 509b010 | 2003-12-17 16:33:10 +1100 | [diff] [blame] | 765 | .It ServerAliveInterval |
| 766 | .It ServerAliveCountMax |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 767 | .It SmartcardDevice |
| 768 | .It StrictHostKeyChecking |
Damien Miller | 12c150e | 2003-12-17 16:31:10 +1100 | [diff] [blame] | 769 | .It TCPKeepAlive |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 770 | .It UsePrivilegedPort |
| 771 | .It User |
| 772 | .It UserKnownHostsFile |
| 773 | .It VerifyHostKeyDNS |
| 774 | .It XAuthLocation |
| 775 | .El |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 776 | .It Fl p Ar port |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 777 | Port to connect to on the remote host. |
| 778 | This can be specified on a |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 779 | per-host basis in the configuration file. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 780 | .It Fl q |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 781 | Quiet mode. |
| 782 | Causes all warning and diagnostic messages to be suppressed. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 783 | .It Fl R Xo |
| 784 | .Sm off |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 785 | .Oo Ar bind_address : Oc |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 786 | .Ar port : host : hostport |
| 787 | .Sm on |
| 788 | .Xc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 789 | 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] | 790 | forwarded to the given host and port on the local side. |
| 791 | This works by allocating a socket to listen to |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 792 | .Ar port |
| 793 | on the remote side, and whenever a connection is made to this port, the |
| 794 | connection is forwarded over the secure channel, and a connection is |
| 795 | made to |
Damien Miller | 34132e5 | 2000-01-14 15:45:46 +1100 | [diff] [blame] | 796 | .Ar host |
| 797 | port |
| 798 | .Ar hostport |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 799 | from the local machine. |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 800 | .Pp |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 801 | Port forwardings can also be specified in the configuration file. |
| 802 | Privileged ports can be forwarded only when |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 803 | logging in as root on the remote machine. |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 804 | IPv6 addresses can be specified by enclosing the address in square braces or |
| 805 | using an alternative syntax: |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 806 | .Sm off |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 807 | .Xo |
Damien Miller | b096ac4 | 2005-03-09 11:00:05 +1100 | [diff] [blame] | 808 | .Op Ar bind_address No / |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 809 | .Ar host No / Ar port No / |
| 810 | .Ar hostport |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 811 | .Xc . |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 812 | .Sm on |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 813 | .Pp |
| 814 | By default, the listening socket on the server will be bound to the loopback |
| 815 | interface only. |
| 816 | This may be overriden by specifying a |
| 817 | .Ar bind_address . |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 818 | An empty |
| 819 | .Ar bind_address , |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 820 | or the address |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 821 | .Ql * , |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 822 | indicates that the remote socket should listen on all interfaces. |
| 823 | Specifying a remote |
| 824 | .Ar bind_address |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 825 | will only succeed if the server's |
| 826 | .Cm GatewayPorts |
Damien Miller | f91ee4c | 2005-03-01 21:24:33 +1100 | [diff] [blame] | 827 | option is enabled (see |
Damien Miller | 36bf7dd | 2005-03-02 12:02:47 +1100 | [diff] [blame] | 828 | .Xr sshd_config 5 ) . |
Darren Tucker | 7ebfc10 | 2004-11-07 20:06:19 +1100 | [diff] [blame] | 829 | .It Fl S Ar ctl_path |
Damien Miller | 5d1eceb | 2004-06-30 22:37:57 +1000 | [diff] [blame] | 830 | Specifies the location of a control socket for connection sharing. |
Damien Miller | 0e220db | 2004-06-15 10:34:08 +1000 | [diff] [blame] | 831 | Refer to the description of |
Darren Tucker | ba5c592 | 2004-06-18 16:22:39 +1000 | [diff] [blame] | 832 | .Cm ControlPath |
| 833 | and |
Damien Miller | 0e220db | 2004-06-15 10:34:08 +1000 | [diff] [blame] | 834 | .Cm ControlMaster |
| 835 | in |
| 836 | .Xr ssh_config 5 |
| 837 | for details. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 838 | .It Fl s |
| 839 | May be used to request invocation of a subsystem on the remote system. |
| 840 | Subsystems are a feature of the SSH2 protocol which facilitate the use |
| 841 | of SSH as a secure transport for other applications (eg.\& |
| 842 | .Xr sftp 1 ) . |
| 843 | The subsystem is specified as the remote command. |
| 844 | .It Fl T |
| 845 | Disable pseudo-tty allocation. |
| 846 | .It Fl t |
| 847 | Force pseudo-tty allocation. |
| 848 | This can be used to execute arbitrary |
| 849 | screen-based programs on a remote machine, which can be very useful, |
| 850 | e.g., when implementing menu services. |
| 851 | Multiple |
| 852 | .Fl t |
| 853 | options force tty allocation, even if |
Ben Lindstrom | 19ceb17 | 2001-09-12 17:54:24 +0000 | [diff] [blame] | 854 | .Nm |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 855 | has no local tty. |
| 856 | .It Fl V |
| 857 | Display the version number and exit. |
| 858 | .It Fl v |
| 859 | Verbose mode. |
| 860 | Causes |
Ben Lindstrom | 5ab6ae1 | 2001-02-10 22:08:03 +0000 | [diff] [blame] | 861 | .Nm |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 862 | to print debugging messages about its progress. |
| 863 | This is helpful in |
| 864 | debugging connection, authentication, and configuration problems. |
| 865 | Multiple |
| 866 | .Fl v |
| 867 | options increase the verbosity. |
| 868 | The maximum is 3. |
| 869 | .It Fl X |
| 870 | Enables X11 forwarding. |
| 871 | This can also be specified on a per-host basis in a configuration file. |
| 872 | .Pp |
| 873 | X11 forwarding should be enabled with caution. |
| 874 | Users with the ability to bypass file permissions on the remote host |
| 875 | (for the user's X authorization database) |
| 876 | can access the local X11 display through the forwarded connection. |
| 877 | 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] | 878 | .Pp |
Damien Miller | b022b23 | 2005-03-05 11:22:36 +1100 | [diff] [blame] | 879 | For this reason, X11 forwarding is subjected to X11 SECURITY extension |
Damien Miller | 947219e | 2005-03-02 13:22:30 +1100 | [diff] [blame] | 880 | restrictions by default. |
| 881 | Please refer to the |
| 882 | .Nm |
| 883 | .Fl Y |
| 884 | option and the |
| 885 | .Cm ForwardX11Trusted |
| 886 | directive in |
| 887 | .Xr ssh_config 5 |
| 888 | for more information. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 889 | .It Fl x |
| 890 | Disables X11 forwarding. |
Darren Tucker | 0a118da | 2003-10-15 15:54:32 +1000 | [diff] [blame] | 891 | .It Fl Y |
| 892 | Enables trusted X11 forwarding. |
Damien Miller | 947219e | 2005-03-02 13:22:30 +1100 | [diff] [blame] | 893 | Trusted X11 forwardings are not subjected to the X11 SECURITY extension |
| 894 | controls. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 895 | .El |
| 896 | .Sh CONFIGURATION FILES |
| 897 | .Nm |
Ben Lindstrom | 9f04903 | 2002-06-21 00:59:05 +0000 | [diff] [blame] | 898 | may additionally obtain configuration data from |
| 899 | a per-user configuration file and a system-wide configuration file. |
| 900 | The file format and configuration options are described in |
| 901 | .Xr ssh_config 5 . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 902 | .Sh ENVIRONMENT |
| 903 | .Nm |
| 904 | will normally set the following environment variables: |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 905 | .Bl -tag -width LOGNAME |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 906 | .It Ev DISPLAY |
| 907 | The |
| 908 | .Ev DISPLAY |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 909 | variable indicates the location of the X11 server. |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 910 | It is automatically set by |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 911 | .Nm |
| 912 | to point to a value of the form |
| 913 | .Dq hostname:n |
| 914 | where hostname indicates |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 915 | the host where the shell runs, and n is an integer \*(Ge 1. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 916 | .Nm |
| 917 | uses this special value to forward X11 connections over the secure |
| 918 | channel. |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 919 | The user should normally not set |
| 920 | .Ev DISPLAY |
| 921 | explicitly, as that |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 922 | will render the X11 connection insecure (and will require the user to |
| 923 | manually copy any required authorization cookies). |
| 924 | .It Ev HOME |
| 925 | Set to the path of the user's home directory. |
| 926 | .It Ev LOGNAME |
| 927 | Synonym for |
| 928 | .Ev USER ; |
| 929 | set for compatibility with systems that use this variable. |
| 930 | .It Ev MAIL |
Ben Lindstrom | e59433d | 2001-09-12 16:41:37 +0000 | [diff] [blame] | 931 | Set to the path of the user's mailbox. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 932 | .It Ev PATH |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 933 | Set to the default |
| 934 | .Ev PATH , |
| 935 | as specified when compiling |
| 936 | .Nm ssh . |
Ben Lindstrom | 5bf5d67 | 2001-07-04 04:31:38 +0000 | [diff] [blame] | 937 | .It Ev SSH_ASKPASS |
| 938 | If |
| 939 | .Nm |
| 940 | needs a passphrase, it will read the passphrase from the current |
| 941 | terminal if it was run from a terminal. |
| 942 | If |
| 943 | .Nm |
| 944 | does not have a terminal associated with it but |
| 945 | .Ev DISPLAY |
| 946 | and |
| 947 | .Ev SSH_ASKPASS |
| 948 | are set, it will execute the program specified by |
| 949 | .Ev SSH_ASKPASS |
| 950 | and open an X11 window to read the passphrase. |
| 951 | This is particularly useful when calling |
| 952 | .Nm |
| 953 | from a |
Darren Tucker | 4e4fe00 | 2004-11-05 20:01:03 +1100 | [diff] [blame] | 954 | .Pa .xsession |
Ben Lindstrom | 5bf5d67 | 2001-07-04 04:31:38 +0000 | [diff] [blame] | 955 | or related script. |
| 956 | (Note that on some machines it |
| 957 | may be necessary to redirect the input from |
| 958 | .Pa /dev/null |
| 959 | to make this work.) |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 960 | .It Ev SSH_AUTH_SOCK |
Ben Lindstrom | e59433d | 2001-09-12 16:41:37 +0000 | [diff] [blame] | 961 | Identifies the path of a unix-domain socket used to communicate with the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 962 | agent. |
Damien Miller | f37e246 | 2002-09-19 11:47:55 +1000 | [diff] [blame] | 963 | .It Ev SSH_CONNECTION |
| 964 | Identifies the client and server ends of the connection. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 965 | The variable contains |
Damien Miller | f37e246 | 2002-09-19 11:47:55 +1000 | [diff] [blame] | 966 | four space-separated values: client ip-address, client port number, |
| 967 | server ip-address and server port number. |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 968 | .It Ev SSH_ORIGINAL_COMMAND |
| 969 | The variable contains the original command line if a forced command |
| 970 | is executed. |
| 971 | It can be used to extract the original arguments. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 972 | .It Ev SSH_TTY |
| 973 | 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] | 974 | with the current shell or command. |
| 975 | If the current session has no tty, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 976 | this variable is not set. |
| 977 | .It Ev TZ |
| 978 | The timezone variable is set to indicate the present timezone if it |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 979 | 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] | 980 | on to new connections). |
| 981 | .It Ev USER |
| 982 | Set to the name of the user logging in. |
| 983 | .El |
| 984 | .Pp |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 985 | Additionally, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 986 | .Nm |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 987 | reads |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 988 | .Pa ~/.ssh/environment , |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 989 | and adds lines of the format |
| 990 | .Dq VARNAME=value |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 991 | to the environment if the file exists and if users are allowed to |
| 992 | change their environment. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 993 | For more information, see the |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 994 | .Cm PermitUserEnvironment |
Ben Lindstrom | bd9bf38 | 2002-08-20 18:54:20 +0000 | [diff] [blame] | 995 | option in |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 996 | .Xr sshd_config 5 . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 997 | .Sh FILES |
Damien Miller | 98c7ad6 | 2000-03-09 21:27:49 +1100 | [diff] [blame] | 998 | .Bl -tag -width Ds |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 999 | .It Pa ~/.ssh/known_hosts |
Ben Lindstrom | e59433d | 2001-09-12 16:41:37 +0000 | [diff] [blame] | 1000 | Records host keys for all hosts the user has logged into that are not |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1001 | in |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 1002 | .Pa /etc/ssh/ssh_known_hosts . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1003 | See |
| 1004 | .Xr sshd 8 . |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1005 | .It Pa ~/.ssh/identity, ~/.ssh/id_dsa, ~/.ssh/id_rsa |
Ben Lindstrom | 18a82ac | 2001-04-11 15:59:35 +0000 | [diff] [blame] | 1006 | Contains the authentication identity of the user. |
| 1007 | They are for protocol 1 RSA, protocol 2 DSA, and protocol 2 RSA, respectively. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 1008 | These files |
| 1009 | contain sensitive data and should be readable by the user but not |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1010 | accessible by others (read/write/execute). |
| 1011 | Note that |
| 1012 | .Nm |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 1013 | ignores a private key file if it is accessible by others. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1014 | It is possible to specify a passphrase when |
| 1015 | generating the key; the passphrase will be used to encrypt the |
| 1016 | sensitive part of this file using 3DES. |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1017 | .It Pa ~/.ssh/identity.pub, ~/.ssh/id_dsa.pub, ~/.ssh/id_rsa.pub |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1018 | Contains the public key for authentication (public part of the |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1019 | identity file in human-readable form). |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 1020 | The contents of the |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1021 | .Pa ~/.ssh/identity.pub |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 1022 | file should be added to the file |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1023 | .Pa ~/.ssh/authorized_keys |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1024 | on all machines |
Ben Lindstrom | 594e203 | 2001-09-12 18:35:30 +0000 | [diff] [blame] | 1025 | where the user wishes to log in using protocol version 1 RSA authentication. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 1026 | The contents of the |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1027 | .Pa ~/.ssh/id_dsa.pub |
Ben Lindstrom | 18a82ac | 2001-04-11 15:59:35 +0000 | [diff] [blame] | 1028 | and |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1029 | .Pa ~/.ssh/id_rsa.pub |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 1030 | file should be added to |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1031 | .Pa ~/.ssh/authorized_keys |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 1032 | on all machines |
Ben Lindstrom | 594e203 | 2001-09-12 18:35:30 +0000 | [diff] [blame] | 1033 | where the user wishes to log in using protocol version 2 DSA/RSA authentication. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 1034 | These files are not |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1035 | sensitive and can (but need not) be readable by anyone. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 1036 | These files are |
Kevin Steves | 3c034ae | 2001-02-05 13:47:11 +0000 | [diff] [blame] | 1037 | never used automatically and are not necessary; they are only provided for |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1038 | the convenience of the user. |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1039 | .It Pa ~/.ssh/config |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1040 | This is the per-user configuration file. |
Ben Lindstrom | 9f04903 | 2002-06-21 00:59:05 +0000 | [diff] [blame] | 1041 | The file format and configuration options are described in |
| 1042 | .Xr ssh_config 5 . |
Damien Miller | c970cb9 | 2004-04-20 20:12:53 +1000 | [diff] [blame] | 1043 | Because of the potential for abuse, this file must have strict permissions: |
| 1044 | read/write for the user, and not accessible by others. |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1045 | .It Pa ~/.ssh/authorized_keys |
Ben Lindstrom | f96704d | 2001-06-25 04:17:12 +0000 | [diff] [blame] | 1046 | Lists the public keys (RSA/DSA) that can be used for logging in as this user. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1047 | The format of this file is described in the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1048 | .Xr sshd 8 |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1049 | manual page. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 1050 | In the simplest form the format is the same as the |
| 1051 | .Pa .pub |
Ben Lindstrom | d6481ea | 2001-06-25 04:37:41 +0000 | [diff] [blame] | 1052 | identity files. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 1053 | This file is not highly sensitive, but the recommended |
| 1054 | permissions are read/write for the user, and not accessible by others. |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 1055 | .It Pa /etc/ssh/ssh_known_hosts |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1056 | Systemwide list of known host keys. |
Ben Lindstrom | d6481ea | 2001-06-25 04:37:41 +0000 | [diff] [blame] | 1057 | This file should be prepared by the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1058 | system administrator to contain the public host keys of all machines in the |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1059 | organization. |
| 1060 | This file should be world-readable. |
| 1061 | This file contains |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1062 | public keys, one per line, in the following format (fields separated |
Ben Lindstrom | d6481ea | 2001-06-25 04:37:41 +0000 | [diff] [blame] | 1063 | by spaces): system name, public key and optional comment field. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1064 | When different names are used |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1065 | for the same machine, all such names should be listed, separated by |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1066 | commas. |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 1067 | The format is described in the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1068 | .Xr sshd 8 |
| 1069 | manual page. |
| 1070 | .Pp |
| 1071 | The canonical system name (as returned by name servers) is used by |
| 1072 | .Xr sshd 8 |
| 1073 | to verify the client host when logging in; other names are needed because |
| 1074 | .Nm |
| 1075 | does not convert the user-supplied name to a canonical name before |
| 1076 | checking the key, because someone with access to the name servers |
| 1077 | would then be able to fool host authentication. |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 1078 | .It Pa /etc/ssh/ssh_config |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1079 | Systemwide configuration file. |
Ben Lindstrom | 9f04903 | 2002-06-21 00:59:05 +0000 | [diff] [blame] | 1080 | The file format and configuration options are described in |
| 1081 | .Xr ssh_config 5 . |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 1082 | .It Pa /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_rsa_key |
Damien Miller | 705499b | 2001-11-12 11:05:38 +1100 | [diff] [blame] | 1083 | These three files contain the private parts of the host keys |
| 1084 | and are used for |
| 1085 | .Cm RhostsRSAAuthentication |
| 1086 | and |
| 1087 | .Cm HostbasedAuthentication . |
Ben Lindstrom | 5cac423 | 2002-06-11 15:45:02 +0000 | [diff] [blame] | 1088 | If the protocol version 1 |
| 1089 | .Cm RhostsRSAAuthentication |
Ben Lindstrom | cb72e4f | 2002-06-21 00:41:51 +0000 | [diff] [blame] | 1090 | method is used, |
Damien Miller | 705499b | 2001-11-12 11:05:38 +1100 | [diff] [blame] | 1091 | .Nm |
Ben Lindstrom | 5cac423 | 2002-06-11 15:45:02 +0000 | [diff] [blame] | 1092 | must be setuid root, since the host key is readable only by root. |
| 1093 | For protocol version 2, |
| 1094 | .Nm |
| 1095 | uses |
| 1096 | .Xr ssh-keysign 8 |
| 1097 | to access the host keys for |
| 1098 | .Cm HostbasedAuthentication . |
| 1099 | This eliminates the requirement that |
| 1100 | .Nm |
| 1101 | be setuid root when that authentication method is used. |
| 1102 | By default |
| 1103 | .Nm |
| 1104 | is not setuid root. |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1105 | .It Pa ~/.rhosts |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1106 | This file is used in |
Darren Tucker | db69390 | 2004-08-29 16:37:24 +1000 | [diff] [blame] | 1107 | .Cm RhostsRSAAuthentication |
| 1108 | and |
| 1109 | .Cm HostbasedAuthentication |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1110 | authentication to list the |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1111 | host/user pairs that are permitted to log in. |
| 1112 | (Note that this file is |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1113 | also used by rlogin and rsh, which makes using this file insecure.) |
| 1114 | Each line of the file contains a host name (in the canonical form |
| 1115 | returned by name servers), and then a user name on that host, |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1116 | separated by a space. |
Ben Lindstrom | ebd888d | 2001-03-05 05:49:29 +0000 | [diff] [blame] | 1117 | On some machines this file may need to be |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1118 | world-readable if the user's home directory is on a NFS partition, |
| 1119 | because |
| 1120 | .Xr sshd 8 |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1121 | reads it as root. |
| 1122 | Additionally, this file must be owned by the user, |
| 1123 | and must not have write permissions for anyone else. |
| 1124 | The recommended |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1125 | permission for most machines is read/write for the user, and not |
| 1126 | accessible by others. |
| 1127 | .Pp |
Darren Tucker | db69390 | 2004-08-29 16:37:24 +1000 | [diff] [blame] | 1128 | Note that |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1129 | .Xr sshd 8 |
Darren Tucker | db69390 | 2004-08-29 16:37:24 +1000 | [diff] [blame] | 1130 | allows authentication only in combination with client host key |
| 1131 | authentication before permitting log in. |
Ben Lindstrom | 594e203 | 2001-09-12 18:35:30 +0000 | [diff] [blame] | 1132 | If the server machine does not have the client's host key in |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 1133 | .Pa /etc/ssh/ssh_known_hosts , |
Ben Lindstrom | 594e203 | 2001-09-12 18:35:30 +0000 | [diff] [blame] | 1134 | it can be stored in |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1135 | .Pa ~/.ssh/known_hosts . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1136 | The easiest way to do this is to |
| 1137 | connect back to the client from the server machine using ssh; this |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 1138 | will automatically add the host key to |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1139 | .Pa ~/.ssh/known_hosts . |
| 1140 | .It Pa ~/.shosts |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1141 | This file is used exactly the same way as |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 1142 | .Pa .rhosts . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1143 | The purpose for |
Darren Tucker | db69390 | 2004-08-29 16:37:24 +1000 | [diff] [blame] | 1144 | having this file is to be able to use |
| 1145 | .Cm RhostsRSAAuthentication |
| 1146 | and |
| 1147 | .Cm HostbasedAuthentication |
| 1148 | authentication without permitting login with |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 1149 | .Xr rlogin |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1150 | or |
| 1151 | .Xr rsh 1 . |
| 1152 | .It Pa /etc/hosts.equiv |
| 1153 | This file is used during |
Darren Tucker | db69390 | 2004-08-29 16:37:24 +1000 | [diff] [blame] | 1154 | .Cm RhostsRSAAuthentication |
| 1155 | and |
| 1156 | .Cm HostbasedAuthentication |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 1157 | authentication. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1158 | It contains |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 1159 | canonical hosts names, one per line (the full format is described in the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1160 | .Xr sshd 8 |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1161 | manual page). |
| 1162 | If the client host is found in this file, login is |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1163 | automatically permitted provided client and server user names are the |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1164 | same. |
Darren Tucker | db69390 | 2004-08-29 16:37:24 +1000 | [diff] [blame] | 1165 | Additionally, successful client host key authentication is required. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 1166 | This file should only be writable by root. |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 1167 | .It Pa /etc/shosts.equiv |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 1168 | This file is processed exactly as |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1169 | .Pa /etc/hosts.equiv . |
| 1170 | This file may be useful to permit logins using |
| 1171 | .Nm |
| 1172 | but not using rsh/rlogin. |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 1173 | .It Pa /etc/ssh/sshrc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1174 | Commands in this file are executed by |
| 1175 | .Nm |
| 1176 | when the user logs in just before the user's shell (or command) is started. |
| 1177 | See the |
| 1178 | .Xr sshd 8 |
| 1179 | manual page for more information. |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1180 | .It Pa ~/.ssh/rc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1181 | Commands in this file are executed by |
| 1182 | .Nm |
| 1183 | when the user logs in just before the user's shell (or command) is |
| 1184 | started. |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 1185 | See the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1186 | .Xr sshd 8 |
| 1187 | manual page for more information. |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 1188 | .It Pa ~/.ssh/environment |
Damien Miller | 4f0fa56 | 1999-12-26 14:24:41 +1100 | [diff] [blame] | 1189 | Contains additional definitions for environment variables, see section |
| 1190 | .Sx ENVIRONMENT |
| 1191 | above. |
Damien Miller | 7b28dc5 | 2000-09-05 13:34:53 +1100 | [diff] [blame] | 1192 | .El |
Damien Miller | 07a2d42 | 2002-02-05 12:16:15 +1100 | [diff] [blame] | 1193 | .Sh DIAGNOSTICS |
| 1194 | .Nm |
| 1195 | exits with the exit status of the remote command or with 255 |
| 1196 | if an error occurred. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1197 | .Sh SEE ALSO |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 1198 | .Xr gzip 1 , |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1199 | .Xr rsh 1 , |
| 1200 | .Xr scp 1 , |
Damien Miller | 3380426 | 2001-02-04 23:20:18 +1100 | [diff] [blame] | 1201 | .Xr sftp 1 , |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1202 | .Xr ssh-add 1 , |
| 1203 | .Xr ssh-agent 1 , |
| 1204 | .Xr ssh-keygen 1 , |
| 1205 | .Xr telnet 1 , |
Darren Tucker | 6177695 | 2003-10-02 16:19:47 +1000 | [diff] [blame] | 1206 | .Xr hosts.equiv 5 , |
Ben Lindstrom | bf69e3b | 2002-06-23 00:31:24 +0000 | [diff] [blame] | 1207 | .Xr ssh_config 5 , |
Ben Lindstrom | c001cd3 | 2002-06-23 00:32:11 +0000 | [diff] [blame] | 1208 | .Xr ssh-keysign 8 , |
Ben Lindstrom | 5ab6ae1 | 2001-02-10 22:08:03 +0000 | [diff] [blame] | 1209 | .Xr sshd 8 |
Ben Lindstrom | 160ec62 | 2001-04-22 17:17:46 +0000 | [diff] [blame] | 1210 | .Rs |
| 1211 | .%A T. Ylonen |
| 1212 | .%A T. Kivinen |
| 1213 | .%A M. Saarinen |
| 1214 | .%A T. Rinne |
| 1215 | .%A S. Lehtinen |
| 1216 | .%T "SSH Protocol Architecture" |
Ben Lindstrom | f181384 | 2002-03-27 17:18:31 +0000 | [diff] [blame] | 1217 | .%N draft-ietf-secsh-architecture-12.txt |
| 1218 | .%D January 2002 |
Ben Lindstrom | 160ec62 | 2001-04-22 17:17:46 +0000 | [diff] [blame] | 1219 | .%O work in progress material |
| 1220 | .Re |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 1221 | .Sh AUTHORS |
| 1222 | OpenSSH is a derivative of the original and free |
| 1223 | ssh 1.2.12 release by Tatu Ylonen. |
| 1224 | Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, |
| 1225 | Theo de Raadt and Dug Song |
| 1226 | removed many bugs, re-added newer features and |
| 1227 | created OpenSSH. |
| 1228 | Markus Friedl contributed the support for SSH |
| 1229 | protocol versions 1.5 and 2.0. |