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 | ec960f2 | 2003-08-13 20:37:05 +1000 | [diff] [blame] | 37 | .\" $OpenBSD: sshd.8,v 1.199 2003/08/13 08:46:31 markus Exp $ |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 38 | .Dd September 25, 1999 |
| 39 | .Dt SSHD 8 |
| 40 | .Os |
| 41 | .Sh NAME |
| 42 | .Nm sshd |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 43 | .Nd OpenSSH SSH daemon |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 44 | .Sh SYNOPSIS |
| 45 | .Nm sshd |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 46 | .Bk -words |
Ben Lindstrom | dfd1850 | 2001-09-20 01:06:08 +0000 | [diff] [blame] | 47 | .Op Fl deiqtD46 |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 48 | .Op Fl b Ar bits |
| 49 | .Op Fl f Ar config_file |
| 50 | .Op Fl g Ar login_grace_time |
| 51 | .Op Fl h Ar host_key_file |
| 52 | .Op Fl k Ar key_gen_time |
Ben Lindstrom | ade03f6 | 2001-12-06 18:22:17 +0000 | [diff] [blame] | 53 | .Op Fl o Ar option |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 54 | .Op Fl p Ar port |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 55 | .Op Fl u Ar len |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 56 | .Ek |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 57 | .Sh DESCRIPTION |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 58 | .Nm |
Ben Lindstrom | d58eb5f | 2001-03-07 06:07:22 +0000 | [diff] [blame] | 59 | (SSH Daemon) is the daemon program for |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 60 | .Xr ssh 1 . |
Damien Miller | 35dabd0 | 2000-05-01 21:10:33 +1000 | [diff] [blame] | 61 | Together these programs replace rlogin and rsh, and |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 62 | provide secure encrypted communications between two untrusted hosts |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 63 | over an insecure network. |
| 64 | The programs are intended to be as easy to |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 65 | install and use as possible. |
| 66 | .Pp |
| 67 | .Nm |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 68 | is the daemon that listens for connections from clients. |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 69 | It is normally started at boot from |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 70 | .Pa /etc/rc . |
| 71 | It forks a new |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 72 | daemon for each incoming connection. |
| 73 | The forked daemons handle |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 74 | key exchange, encryption, authentication, command execution, |
| 75 | and data exchange. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 76 | This implementation of |
| 77 | .Nm |
| 78 | supports both SSH protocol version 1 and 2 simultaneously. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 79 | .Nm |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 80 | works as follows: |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 81 | .Pp |
| 82 | .Ss SSH protocol version 1 |
| 83 | .Pp |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 84 | Each host has a host-specific RSA key |
| 85 | (normally 1024 bits) used to identify the host. |
| 86 | Additionally, when |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 87 | the daemon starts, it generates a server RSA key (normally 768 bits). |
| 88 | This key is normally regenerated every hour if it has been used, and |
| 89 | is never stored on disk. |
| 90 | .Pp |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 91 | Whenever a client connects, the daemon responds with its public |
Damien Miller | 35dabd0 | 2000-05-01 21:10:33 +1000 | [diff] [blame] | 92 | host and server keys. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 93 | The client compares the |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 94 | RSA host key against its own database to verify that it has not changed. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 95 | The client then generates a 256 bit random number. |
| 96 | It encrypts this |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 97 | random number using both the host key and the server key, and sends |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 98 | the encrypted number to the server. |
Damien Miller | 35dabd0 | 2000-05-01 21:10:33 +1000 | [diff] [blame] | 99 | Both sides then use this |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 100 | random number as a session key which is used to encrypt all further |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 101 | communications in the session. |
| 102 | The rest of the session is encrypted |
Damien Miller | 35dabd0 | 2000-05-01 21:10:33 +1000 | [diff] [blame] | 103 | using a conventional cipher, currently Blowfish or 3DES, with 3DES |
Damien Miller | b38eff8 | 2000-04-01 11:09:21 +1000 | [diff] [blame] | 104 | being used by default. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 105 | The client selects the encryption algorithm |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 106 | to use from those offered by the server. |
| 107 | .Pp |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 108 | Next, the server and the client enter an authentication dialog. |
| 109 | The client tries to authenticate itself using |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 110 | .Pa .rhosts |
| 111 | authentication, |
| 112 | .Pa .rhosts |
| 113 | authentication combined with RSA host |
| 114 | authentication, RSA challenge-response authentication, or password |
| 115 | based authentication. |
| 116 | .Pp |
| 117 | Rhosts authentication is normally disabled |
| 118 | because it is fundamentally insecure, but can be enabled in the server |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 119 | configuration file if desired. |
| 120 | System security is not improved unless |
Ben Lindstrom | c57bbf1 | 2002-05-15 21:36:45 +0000 | [diff] [blame] | 121 | .Nm rshd , |
| 122 | .Nm rlogind , |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 123 | and |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 124 | .Nm rexecd |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 125 | are disabled (thus completely disabling |
Ben Lindstrom | c57bbf1 | 2002-05-15 21:36:45 +0000 | [diff] [blame] | 126 | .Xr rlogin |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 127 | and |
Ben Lindstrom | c57bbf1 | 2002-05-15 21:36:45 +0000 | [diff] [blame] | 128 | .Xr rsh |
Damien Miller | 35dabd0 | 2000-05-01 21:10:33 +1000 | [diff] [blame] | 129 | into the machine). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 130 | .Pp |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 131 | .Ss SSH protocol version 2 |
| 132 | .Pp |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 133 | Version 2 works similarly: |
Ben Lindstrom | 07d24dc | 2001-08-06 21:18:57 +0000 | [diff] [blame] | 134 | Each host has a host-specific key (RSA or DSA) used to identify the host. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 135 | However, when the daemon starts, it does not generate a server key. |
| 136 | Forward security is provided through a Diffie-Hellman key agreement. |
| 137 | This key agreement results in a shared session key. |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 138 | .Pp |
Ben Lindstrom | fd2e05b | 2001-03-05 07:48:45 +0000 | [diff] [blame] | 139 | The rest of the session is encrypted using a symmetric cipher, currently |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 140 | 128 bit AES, Blowfish, 3DES, CAST128, Arcfour, 192 bit AES, or 256 bit AES. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 141 | The client selects the encryption algorithm |
| 142 | to use from those offered by the server. |
| 143 | Additionally, session integrity is provided |
Damien Miller | 30c3d42 | 2000-05-09 11:02:59 +1000 | [diff] [blame] | 144 | through a cryptographic message authentication code |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 145 | (hmac-sha1 or hmac-md5). |
| 146 | .Pp |
| 147 | Protocol version 2 provides a public key based |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 148 | user (PubkeyAuthentication) or |
| 149 | client host (HostbasedAuthentication) authentication method, |
| 150 | conventional password authentication and challenge response based methods. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 151 | .Pp |
| 152 | .Ss Command execution and data forwarding |
| 153 | .Pp |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 154 | If the client successfully authenticates itself, a dialog for |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 155 | preparing the session is entered. |
| 156 | At this time the client may request |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 157 | things like allocating a pseudo-tty, forwarding X11 connections, |
| 158 | forwarding TCP/IP connections, or forwarding the authentication agent |
| 159 | connection over the secure channel. |
| 160 | .Pp |
| 161 | Finally, the client either requests a shell or execution of a command. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 162 | The sides then enter session mode. |
| 163 | In this mode, either side may send |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 164 | data at any time, and such data is forwarded to/from the shell or |
| 165 | command on the server side, and the user terminal in the client side. |
| 166 | .Pp |
| 167 | When the user program terminates and all forwarded X11 and other |
| 168 | connections have been closed, the server sends command exit status to |
| 169 | the client, and both sides exit. |
| 170 | .Pp |
| 171 | .Nm |
| 172 | can be configured using command-line options or a configuration |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 173 | file. |
| 174 | Command-line options override values specified in the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 175 | configuration file. |
| 176 | .Pp |
Damien Miller | 6162d12 | 1999-11-21 13:23:52 +1100 | [diff] [blame] | 177 | .Nm |
| 178 | rereads its configuration file when it receives a hangup signal, |
Ben Lindstrom | 49a098d | 2001-03-05 06:55:18 +0000 | [diff] [blame] | 179 | .Dv SIGHUP , |
Ben Lindstrom | d2bf0d6 | 2001-06-25 04:10:54 +0000 | [diff] [blame] | 180 | by executing itself with the name it was started as, i.e., |
Ben Lindstrom | 49a098d | 2001-03-05 06:55:18 +0000 | [diff] [blame] | 181 | .Pa /usr/sbin/sshd . |
Damien Miller | 6162d12 | 1999-11-21 13:23:52 +1100 | [diff] [blame] | 182 | .Pp |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 183 | The options are as follows: |
| 184 | .Bl -tag -width Ds |
| 185 | .It Fl b Ar bits |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 186 | Specifies the number of bits in the ephemeral protocol version 1 |
| 187 | server key (default 768). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 188 | .It Fl d |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 189 | Debug mode. |
| 190 | The server sends verbose debug output to the system |
| 191 | log, and does not put itself in the background. |
| 192 | The server also will not fork and will only process one connection. |
| 193 | This option is only intended for debugging for the server. |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 194 | Multiple |
| 195 | .Fl d |
| 196 | options increase the debugging level. |
Damien Miller | 874d77b | 2000-10-14 16:23:11 +1100 | [diff] [blame] | 197 | Maximum is 3. |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 198 | .It Fl e |
| 199 | When this option is specified, |
| 200 | .Nm |
| 201 | will send the output to the standard error instead of the system log. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 202 | .It Fl f Ar configuration_file |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 203 | Specifies the name of the configuration file. |
| 204 | The default is |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 205 | .Pa /etc/ssh/sshd_config . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 206 | .Nm |
| 207 | refuses to start if there is no configuration file. |
| 208 | .It Fl g Ar login_grace_time |
| 209 | Gives the grace time for clients to authenticate themselves (default |
Damien Miller | c134863 | 2002-09-05 14:35:14 +1000 | [diff] [blame] | 210 | 120 seconds). |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 211 | If the client fails to authenticate the user within |
| 212 | this many seconds, the server disconnects and exits. |
| 213 | A value of zero indicates no limit. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 214 | .It Fl h Ar host_key_file |
Damien Miller | 7fc2373 | 2002-01-22 23:19:11 +1100 | [diff] [blame] | 215 | Specifies a file from which a host key is read. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 216 | This option must be given if |
| 217 | .Nm |
| 218 | is not run as root (as the normal |
Damien Miller | 7fc2373 | 2002-01-22 23:19:11 +1100 | [diff] [blame] | 219 | host key files are normally not readable by anyone but root). |
| 220 | The default is |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 221 | .Pa /etc/ssh/ssh_host_key |
Damien Miller | 7fc2373 | 2002-01-22 23:19:11 +1100 | [diff] [blame] | 222 | for protocol version 1, and |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 223 | .Pa /etc/ssh/ssh_host_rsa_key |
Damien Miller | 7fc2373 | 2002-01-22 23:19:11 +1100 | [diff] [blame] | 224 | and |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 225 | .Pa /etc/ssh/ssh_host_dsa_key |
Damien Miller | 7fc2373 | 2002-01-22 23:19:11 +1100 | [diff] [blame] | 226 | for protocol version 2. |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 227 | It is possible to have multiple host key files for |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 228 | the different protocol versions and host key algorithms. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 229 | .It Fl i |
| 230 | Specifies that |
| 231 | .Nm |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 232 | is being run from |
| 233 | .Xr inetd 8 . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 234 | .Nm |
| 235 | is normally not run |
| 236 | from inetd because it needs to generate the server key before it can |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 237 | respond to the client, and this may take tens of seconds. |
| 238 | Clients would have to wait too long if the key was regenerated every time. |
Damien Miller | 7684ee1 | 2000-03-17 23:40:15 +1100 | [diff] [blame] | 239 | However, with small key sizes (e.g., 512) using |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 240 | .Nm |
| 241 | from inetd may |
| 242 | be feasible. |
| 243 | .It Fl k Ar key_gen_time |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 244 | Specifies how often the ephemeral protocol version 1 server key is |
| 245 | regenerated (default 3600 seconds, or one hour). |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 246 | The motivation for regenerating the key fairly |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 247 | often is that the key is not stored anywhere, and after about an hour, |
| 248 | it becomes impossible to recover the key for decrypting intercepted |
| 249 | communications even if the machine is cracked into or physically |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 250 | seized. |
| 251 | A value of zero indicates that the key will never be regenerated. |
Ben Lindstrom | ade03f6 | 2001-12-06 18:22:17 +0000 | [diff] [blame] | 252 | .It Fl o Ar option |
| 253 | Can be used to give options in the format used in the configuration file. |
| 254 | This is useful for specifying options for which there is no separate |
| 255 | command-line flag. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 256 | .It Fl p Ar port |
| 257 | Specifies the port on which the server listens for connections |
| 258 | (default 22). |
Damien Miller | 7d1ded4 | 2002-01-22 23:09:41 +1100 | [diff] [blame] | 259 | Multiple port options are permitted. |
| 260 | Ports specified in the configuration file are ignored when a |
| 261 | command-line port is specified. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 262 | .It Fl q |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 263 | Quiet mode. |
| 264 | Nothing is sent to the system log. |
| 265 | Normally the beginning, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 266 | authentication, and termination of each connection is logged. |
Ben Lindstrom | 794325a | 2001-08-06 21:09:07 +0000 | [diff] [blame] | 267 | .It Fl t |
| 268 | Test mode. |
| 269 | Only check the validity of the configuration file and sanity of the keys. |
Damien Miller | 9f0f5c6 | 2001-12-21 14:45:46 +1100 | [diff] [blame] | 270 | This is useful for updating |
Ben Lindstrom | 794325a | 2001-08-06 21:09:07 +0000 | [diff] [blame] | 271 | .Nm |
| 272 | reliably as configuration options may change. |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 273 | .It Fl u Ar len |
| 274 | This option is used to specify the size of the field |
| 275 | in the |
| 276 | .Li utmp |
| 277 | structure that holds the remote host name. |
| 278 | If the resolved host name is longer than |
| 279 | .Ar len , |
| 280 | the dotted decimal value will be used instead. |
| 281 | This allows hosts with very long host names that |
| 282 | overflow this field to still be uniquely identified. |
| 283 | Specifying |
| 284 | .Fl u0 |
| 285 | indicates that only dotted decimal addresses |
| 286 | should be put into the |
| 287 | .Pa utmp |
| 288 | file. |
Ben Lindstrom | 6f672c0 | 2001-09-12 17:51:55 +0000 | [diff] [blame] | 289 | .Fl u0 |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 290 | may also be used to prevent |
Ben Lindstrom | 6f672c0 | 2001-09-12 17:51:55 +0000 | [diff] [blame] | 291 | .Nm |
| 292 | from making DNS requests unless the authentication |
| 293 | mechanism or configuration requires it. |
| 294 | Authentication mechanisms that may require DNS include |
Ben Lindstrom | 6f672c0 | 2001-09-12 17:51:55 +0000 | [diff] [blame] | 295 | .Cm RhostsRSAAuthentication , |
| 296 | .Cm HostbasedAuthentication |
| 297 | and using a |
| 298 | .Cm from="pattern-list" |
| 299 | option in a key file. |
Ben Lindstrom | ea03db9 | 2002-03-05 01:38:57 +0000 | [diff] [blame] | 300 | Configuration options that require DNS include using a |
| 301 | USER@HOST pattern in |
| 302 | .Cm AllowUsers |
| 303 | or |
| 304 | .Cm DenyUsers . |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 305 | .It Fl D |
| 306 | When this option is specified |
| 307 | .Nm |
| 308 | will not detach and does not become a daemon. |
| 309 | This allows easy monitoring of |
| 310 | .Nm sshd . |
Damien Miller | 34132e5 | 2000-01-14 15:45:46 +1100 | [diff] [blame] | 311 | .It Fl 4 |
| 312 | Forces |
| 313 | .Nm |
| 314 | to use IPv4 addresses only. |
| 315 | .It Fl 6 |
| 316 | Forces |
| 317 | .Nm |
| 318 | to use IPv6 addresses only. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 319 | .El |
| 320 | .Sh CONFIGURATION FILE |
| 321 | .Nm |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 322 | reads configuration data from |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 323 | .Pa /etc/ssh/sshd_config |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 324 | (or the file specified with |
| 325 | .Fl f |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 326 | on the command line). |
Ben Lindstrom | 9f04903 | 2002-06-21 00:59:05 +0000 | [diff] [blame] | 327 | The file format and configuration options are described in |
| 328 | .Xr sshd_config 5 . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 329 | .Sh LOGIN PROCESS |
| 330 | When a user successfully logs in, |
| 331 | .Nm |
| 332 | does the following: |
| 333 | .Bl -enum -offset indent |
| 334 | .It |
| 335 | If the login is on a tty, and no command has been specified, |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 336 | prints last login time and |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 337 | .Pa /etc/motd |
| 338 | (unless prevented in the configuration file or by |
| 339 | .Pa $HOME/.hushlogin ; |
| 340 | see the |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 341 | .Sx FILES |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 342 | section). |
| 343 | .It |
| 344 | If the login is on a tty, records login time. |
| 345 | .It |
| 346 | Checks |
| 347 | .Pa /etc/nologin ; |
| 348 | if it exists, prints contents and quits |
| 349 | (unless root). |
| 350 | .It |
| 351 | Changes to run with normal user privileges. |
| 352 | .It |
| 353 | Sets up basic environment. |
| 354 | .It |
| 355 | Reads |
| 356 | .Pa $HOME/.ssh/environment |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 357 | if it exists and users are allowed to change their environment. |
Ben Lindstrom | bd9bf38 | 2002-08-20 18:54:20 +0000 | [diff] [blame] | 358 | See the |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 359 | .Cm PermitUserEnvironment |
Ben Lindstrom | bd9bf38 | 2002-08-20 18:54:20 +0000 | [diff] [blame] | 360 | option in |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 361 | .Xr sshd_config 5 . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 362 | .It |
| 363 | Changes to user's home directory. |
| 364 | .It |
| 365 | If |
| 366 | .Pa $HOME/.ssh/rc |
| 367 | exists, runs it; else if |
Damien Miller | afcc225 | 2002-02-10 18:32:55 +1100 | [diff] [blame] | 368 | .Pa /etc/ssh/sshrc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 369 | exists, runs |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 370 | it; otherwise runs xauth. |
| 371 | The |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 372 | .Dq rc |
| 373 | files are given the X11 |
| 374 | authentication protocol and cookie in standard input. |
| 375 | .It |
| 376 | Runs user's shell or command. |
| 377 | .El |
| 378 | .Sh AUTHORIZED_KEYS FILE FORMAT |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 379 | .Pa $HOME/.ssh/authorized_keys |
Ben Lindstrom | f96704d | 2001-06-25 04:17:12 +0000 | [diff] [blame] | 380 | is the default file that lists the public keys that are |
| 381 | permitted for RSA authentication in protocol version 1 |
| 382 | and for public key authentication (PubkeyAuthentication) |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 383 | in protocol version 2. |
Ben Lindstrom | f96704d | 2001-06-25 04:17:12 +0000 | [diff] [blame] | 384 | .Cm AuthorizedKeysFile |
Ben Lindstrom | bfb3a0e | 2001-06-05 20:25:05 +0000 | [diff] [blame] | 385 | may be used to specify an alternative file. |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 386 | .Pp |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 387 | Each line of the file contains one |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 388 | key (empty lines and lines starting with a |
| 389 | .Ql # |
| 390 | are ignored as |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 391 | comments). |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 392 | Each RSA public key consists of the following fields, separated by |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 393 | spaces: options, bits, exponent, modulus, comment. |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 394 | Each protocol version 2 public key consists of: |
| 395 | options, keytype, base64 encoded key, comment. |
Damien Miller | b83df8d | 2002-09-04 16:24:55 +1000 | [diff] [blame] | 396 | The options field |
| 397 | is optional; its presence is determined by whether the line starts |
| 398 | with a number or not (the options field never starts with a number). |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 399 | The bits, exponent, modulus and comment fields give the RSA key for |
| 400 | protocol version 1; the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 401 | comment field is not used for anything (but may be convenient for the |
| 402 | user to identify the key). |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 403 | For protocol version 2 the keytype is |
| 404 | .Dq ssh-dss |
| 405 | or |
| 406 | .Dq ssh-rsa . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 407 | .Pp |
| 408 | Note that lines in this file are usually several hundred bytes long |
Damien Miller | b83df8d | 2002-09-04 16:24:55 +1000 | [diff] [blame] | 409 | (because of the size of the public key encoding). |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 410 | You don't want to type them in; instead, copy the |
Ben Lindstrom | 18a82ac | 2001-04-11 15:59:35 +0000 | [diff] [blame] | 411 | .Pa identity.pub , |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 412 | .Pa id_dsa.pub |
Ben Lindstrom | 18a82ac | 2001-04-11 15:59:35 +0000 | [diff] [blame] | 413 | or the |
| 414 | .Pa id_rsa.pub |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 415 | file and edit it. |
| 416 | .Pp |
Ben Lindstrom | 0d0be02 | 2002-04-02 20:39:29 +0000 | [diff] [blame] | 417 | .Nm |
| 418 | enforces a minimum RSA key modulus size for protocol 1 |
| 419 | and protocol 2 keys of 768 bits. |
| 420 | .Pp |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 421 | The options (if present) consist of comma-separated option |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 422 | specifications. |
| 423 | No spaces are permitted, except within double quotes. |
Ben Lindstrom | 1c0fd09 | 2001-09-12 16:36:17 +0000 | [diff] [blame] | 424 | The following option specifications are supported (note |
| 425 | that option keywords are case-insensitive): |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 426 | .Bl -tag -width Ds |
| 427 | .It Cm from="pattern-list" |
Damien Miller | b83df8d | 2002-09-04 16:24:55 +1000 | [diff] [blame] | 428 | Specifies that in addition to public key authentication, the canonical name |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 429 | of the remote host must be present in the comma-separated list of |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 430 | patterns |
Damien Miller | 3155432 | 2003-05-14 13:44:58 +1000 | [diff] [blame] | 431 | .Pf ( Ql \&* |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 432 | and |
Damien Miller | 049245d | 2003-05-14 13:44:42 +1000 | [diff] [blame] | 433 | .Ql \&? |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 434 | serve as wildcards). |
| 435 | The list may also contain |
| 436 | patterns negated by prefixing them with |
Damien Miller | 049245d | 2003-05-14 13:44:42 +1000 | [diff] [blame] | 437 | .Ql \&! ; |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 438 | if the canonical host name matches a negated pattern, the key is not accepted. |
| 439 | The purpose |
Damien Miller | b83df8d | 2002-09-04 16:24:55 +1000 | [diff] [blame] | 440 | of this option is to optionally increase security: public key authentication |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 441 | by itself does not trust the network or name servers or anything (but |
| 442 | the key); however, if somebody somehow steals the key, the key |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 443 | permits an intruder to log in from anywhere in the world. |
| 444 | This additional option makes using a stolen key more difficult (name |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 445 | servers and/or routers would have to be compromised in addition to |
| 446 | just the key). |
| 447 | .It Cm command="command" |
| 448 | Specifies that the command is executed whenever this key is used for |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 449 | authentication. |
| 450 | The command supplied by the user (if any) is ignored. |
Ben Lindstrom | 23124ea | 2001-09-14 23:14:25 +0000 | [diff] [blame] | 451 | The command is run on a pty if the client requests a pty; |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 452 | otherwise it is run without a tty. |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 453 | If an 8-bit clean channel is required, |
Ben Lindstrom | 594e203 | 2001-09-12 18:35:30 +0000 | [diff] [blame] | 454 | one must not request a pty or should specify |
Damien Miller | 3380426 | 2001-02-04 23:20:18 +1100 | [diff] [blame] | 455 | .Cm no-pty . |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 456 | A quote may be included in the command by quoting it with a backslash. |
| 457 | This option might be useful |
Damien Miller | b83df8d | 2002-09-04 16:24:55 +1000 | [diff] [blame] | 458 | to restrict certain public keys to perform just a specific operation. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 459 | An example might be a key that permits remote backups but nothing else. |
Damien Miller | 30c3d42 | 2000-05-09 11:02:59 +1000 | [diff] [blame] | 460 | Note that the client may specify TCP/IP and/or X11 |
| 461 | forwarding unless they are explicitly prohibited. |
Ben Lindstrom | 20daef7 | 2001-09-20 00:54:01 +0000 | [diff] [blame] | 462 | Note that this option applies to shell, command or subsystem execution. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 463 | .It Cm environment="NAME=value" |
| 464 | Specifies that the string is to be added to the environment when |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 465 | logging in using this key. |
| 466 | Environment variables set this way |
| 467 | override other default environment values. |
| 468 | Multiple options of this type are permitted. |
Ben Lindstrom | bd9bf38 | 2002-08-20 18:54:20 +0000 | [diff] [blame] | 469 | Environment processing is disabled by default and is |
| 470 | controlled via the |
| 471 | .Cm PermitUserEnvironment |
| 472 | option. |
Ben Lindstrom | 38b951c | 2001-12-06 17:47:47 +0000 | [diff] [blame] | 473 | This option is automatically disabled if |
| 474 | .Cm UseLogin |
| 475 | is enabled. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 476 | .It Cm no-port-forwarding |
| 477 | Forbids TCP/IP forwarding when this key is used for authentication. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 478 | Any port forward requests by the client will return an error. |
| 479 | This might be used, e.g., in connection with the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 480 | .Cm command |
| 481 | option. |
| 482 | .It Cm no-X11-forwarding |
| 483 | Forbids X11 forwarding when this key is used for authentication. |
| 484 | Any X11 forward requests by the client will return an error. |
| 485 | .It Cm no-agent-forwarding |
| 486 | Forbids authentication agent forwarding when this key is used for |
| 487 | authentication. |
| 488 | .It Cm no-pty |
| 489 | Prevents tty allocation (a request to allocate a pty will fail). |
Damien Miller | a243fde | 2001-03-19 23:16:08 +1100 | [diff] [blame] | 490 | .It Cm permitopen="host:port" |
Ben Lindstrom | 2464322 | 2001-06-25 05:08:11 +0000 | [diff] [blame] | 491 | Limit local |
Damien Miller | a243fde | 2001-03-19 23:16:08 +1100 | [diff] [blame] | 492 | .Li ``ssh -L'' |
Ben Lindstrom | 4b3564e | 2001-04-10 02:41:56 +0000 | [diff] [blame] | 493 | port forwarding such that it may only connect to the specified host and |
Ben Lindstrom | d71ba57 | 2001-09-12 18:03:31 +0000 | [diff] [blame] | 494 | port. |
| 495 | IPv6 addresses can be specified with an alternative syntax: |
| 496 | .Ar host/port . |
| 497 | Multiple |
Damien Miller | a243fde | 2001-03-19 23:16:08 +1100 | [diff] [blame] | 498 | .Cm permitopen |
Damien Miller | fbf486b | 2003-05-23 18:44:23 +1000 | [diff] [blame] | 499 | options may be applied separated by commas. |
| 500 | No pattern matching is performed on the specified hostnames, |
| 501 | they must be literal domains or addresses. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 502 | .El |
| 503 | .Ss Examples |
| 504 | 1024 33 12121.\|.\|.\|312314325 ylo@foo.bar |
| 505 | .Pp |
| 506 | from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23.\|.\|.\|2334 ylo@niksula |
| 507 | .Pp |
| 508 | command="dump /home",no-pty,no-port-forwarding 1024 33 23.\|.\|.\|2323 backup.hut.fi |
Damien Miller | a243fde | 2001-03-19 23:16:08 +1100 | [diff] [blame] | 509 | .Pp |
| 510 | permitopen="10.2.1.55:80",permitopen="10.2.1.56:25" 1024 33 23.\|.\|.\|2323 |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 511 | .Sh SSH_KNOWN_HOSTS FILE FORMAT |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 512 | The |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 513 | .Pa /etc/ssh/ssh_known_hosts |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 514 | and |
Ben Lindstrom | d6481ea | 2001-06-25 04:37:41 +0000 | [diff] [blame] | 515 | .Pa $HOME/.ssh/known_hosts |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 516 | files contain host public keys for all known hosts. |
| 517 | The global file should |
| 518 | be prepared by the administrator (optional), and the per-user file is |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 519 | maintained automatically: whenever the user connects from an unknown host |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 520 | its key is added to the per-user file. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 521 | .Pp |
| 522 | Each line in these files contains the following fields: hostnames, |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 523 | bits, exponent, modulus, comment. |
| 524 | The fields are separated by spaces. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 525 | .Pp |
Damien Miller | 3155432 | 2003-05-14 13:44:58 +1000 | [diff] [blame] | 526 | Hostnames is a comma-separated list of patterns |
Damien Miller | fbf486b | 2003-05-23 18:44:23 +1000 | [diff] [blame] | 527 | .Pf ( Ql \&* |
| 528 | and |
| 529 | .Ql \&? |
Damien Miller | 049245d | 2003-05-14 13:44:42 +1000 | [diff] [blame] | 530 | act as |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 531 | wildcards); each pattern in turn is matched against the canonical host |
| 532 | name (when authenticating a client) or against the user-supplied |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 533 | name (when authenticating a server). |
| 534 | A pattern may also be preceded by |
Damien Miller | 049245d | 2003-05-14 13:44:42 +1000 | [diff] [blame] | 535 | .Ql \&! |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 536 | to indicate negation: if the host name matches a negated |
| 537 | pattern, it is not accepted (by that line) even if it matched another |
| 538 | pattern on the line. |
| 539 | .Pp |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 540 | Bits, exponent, and modulus are taken directly from the RSA host key; they |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 541 | can be obtained, e.g., from |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 542 | .Pa /etc/ssh/ssh_host_key.pub . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 543 | The optional comment field continues to the end of the line, and is not used. |
| 544 | .Pp |
| 545 | Lines starting with |
| 546 | .Ql # |
| 547 | and empty lines are ignored as comments. |
| 548 | .Pp |
| 549 | When performing host authentication, authentication is accepted if any |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 550 | matching line has the proper key. |
| 551 | It is thus permissible (but not |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 552 | recommended) to have several lines or different host keys for the same |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 553 | names. |
| 554 | This will inevitably happen when short forms of host names |
| 555 | from different domains are put in the file. |
| 556 | It is possible |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 557 | that the files contain conflicting information; authentication is |
| 558 | accepted if valid information can be found from either file. |
| 559 | .Pp |
| 560 | Note that the lines in these files are typically hundreds of characters |
| 561 | long, and you definitely don't want to type in the host keys by hand. |
| 562 | Rather, generate them by a script |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 563 | or by taking |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 564 | .Pa /etc/ssh/ssh_host_key.pub |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 565 | and adding the host names at the front. |
| 566 | .Ss Examples |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 567 | .Bd -literal |
| 568 | closenet,.\|.\|.\|,130.233.208.41 1024 37 159.\|.\|.93 closenet.hut.fi |
| 569 | cvs.openbsd.org,199.185.137.3 ssh-rsa AAAA1234.....= |
| 570 | .Ed |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 571 | .Sh FILES |
| 572 | .Bl -tag -width Ds |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 573 | .It Pa /etc/ssh/sshd_config |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 574 | Contains configuration data for |
| 575 | .Nm sshd . |
Ben Lindstrom | 9f04903 | 2002-06-21 00:59:05 +0000 | [diff] [blame] | 576 | The file format and configuration options are described in |
| 577 | .Xr sshd_config 5 . |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 578 | .It Pa /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_rsa_key |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 579 | These three files contain the private parts of the host keys. |
Ben Lindstrom | d7f5b51 | 2001-03-05 06:57:23 +0000 | [diff] [blame] | 580 | These files should only be owned by root, readable only by root, and not |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 581 | accessible to others. |
| 582 | Note that |
| 583 | .Nm |
| 584 | does not start if this file is group/world-accessible. |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 585 | .It Pa /etc/ssh/ssh_host_key.pub, /etc/ssh/ssh_host_dsa_key.pub, /etc/ssh/ssh_host_rsa_key.pub |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 586 | These three files contain the public parts of the host keys. |
Ben Lindstrom | d7f5b51 | 2001-03-05 06:57:23 +0000 | [diff] [blame] | 587 | These files should be world-readable but writable only by |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 588 | root. |
Ben Lindstrom | d7f5b51 | 2001-03-05 06:57:23 +0000 | [diff] [blame] | 589 | Their contents should match the respective private parts. |
| 590 | These files are not |
| 591 | really used for anything; they are provided for the convenience of |
| 592 | the user so their contents can be copied to known hosts files. |
| 593 | These files are created using |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 594 | .Xr ssh-keygen 1 . |
Ben Lindstrom | ae1c51c | 2001-06-25 04:14:59 +0000 | [diff] [blame] | 595 | .It Pa /etc/moduli |
Damien Miller | e39cacc | 2000-11-29 12:18:44 +1100 | [diff] [blame] | 596 | Contains Diffie-Hellman groups used for the "Diffie-Hellman Group Exchange". |
Damien Miller | 86247e2 | 2002-09-19 11:51:53 +1000 | [diff] [blame] | 597 | The file format is described in |
| 598 | .Xr moduli 5 . |
Ben Lindstrom | 624e3f2 | 2002-06-23 00:32:57 +0000 | [diff] [blame] | 599 | .It Pa /var/empty |
| 600 | .Xr chroot 2 |
| 601 | directory used by |
| 602 | .Nm |
| 603 | during privilege separation in the pre-authentication phase. |
| 604 | The directory should not contain any files and must be owned by root |
| 605 | and not group or world-writable. |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 606 | .It Pa /var/run/sshd.pid |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 607 | Contains the process ID of the |
| 608 | .Nm |
| 609 | listening for connections (if there are several daemons running |
Ben Lindstrom | 959de99 | 2002-06-23 00:35:25 +0000 | [diff] [blame] | 610 | concurrently for different ports, this contains the process ID of the one |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 611 | started last). |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 612 | The content of this file is not sensitive; it can be world-readable. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 613 | .It Pa $HOME/.ssh/authorized_keys |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 614 | Lists the public keys (RSA or DSA) that can be used to log into the user's account. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 615 | This file must be readable by root (which may on some machines imply |
| 616 | it being world-readable if the user's home directory resides on an NFS |
| 617 | volume). |
| 618 | It is recommended that it not be accessible by others. |
| 619 | The format of this file is described above. |
| 620 | Users will place the contents of their |
Ben Lindstrom | f96704d | 2001-06-25 04:17:12 +0000 | [diff] [blame] | 621 | .Pa identity.pub , |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 622 | .Pa id_dsa.pub |
Ben Lindstrom | 18a82ac | 2001-04-11 15:59:35 +0000 | [diff] [blame] | 623 | and/or |
| 624 | .Pa id_rsa.pub |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 625 | files into this file, as described in |
| 626 | .Xr ssh-keygen 1 . |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 627 | .It Pa "/etc/ssh/ssh_known_hosts" and "$HOME/.ssh/known_hosts" |
Damien Miller | 5ce662a | 1999-11-11 17:57:39 +1100 | [diff] [blame] | 628 | These files are consulted when using rhosts with RSA host |
Ben Lindstrom | d6481ea | 2001-06-25 04:37:41 +0000 | [diff] [blame] | 629 | authentication or protocol version 2 hostbased authentication |
| 630 | to check the public key of the host. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 631 | The key must be listed in one of these files to be accepted. |
Damien Miller | 33e511e | 1999-11-11 11:43:13 +1100 | [diff] [blame] | 632 | The client uses the same files |
Ben Lindstrom | ebd888d | 2001-03-05 05:49:29 +0000 | [diff] [blame] | 633 | to verify that it is connecting to the correct remote host. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 634 | These files should be writable only by root/the owner. |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 635 | .Pa /etc/ssh/ssh_known_hosts |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 636 | should be world-readable, and |
| 637 | .Pa $HOME/.ssh/known_hosts |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 638 | can, but need not be, world-readable. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 639 | .It Pa /etc/nologin |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 640 | If this file exists, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 641 | .Nm |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 642 | refuses to let anyone except root log in. |
| 643 | The contents of the file |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 644 | are displayed to anyone trying to log in, and non-root connections are |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 645 | refused. |
| 646 | The file should be world-readable. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 647 | .It Pa /etc/hosts.allow, /etc/hosts.deny |
Ben Lindstrom | 6149a6c | 2001-10-03 17:15:32 +0000 | [diff] [blame] | 648 | Access controls that should be enforced by tcp-wrappers are defined here. |
| 649 | Further details are described in |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 650 | .Xr hosts_access 5 . |
| 651 | .It Pa $HOME/.rhosts |
| 652 | This file contains host-username pairs, separated by a space, one per |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 653 | line. |
| 654 | The given user on the corresponding host is permitted to log in |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 655 | without a password. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 656 | The same file is used by rlogind and rshd. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 657 | The file must |
| 658 | be writable only by the user; it is recommended that it not be |
| 659 | accessible by others. |
| 660 | .Pp |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 661 | If is also possible to use netgroups in the file. |
| 662 | Either host or user |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 663 | name may be of the form +@groupname to specify all hosts or all users |
| 664 | in the group. |
| 665 | .It Pa $HOME/.shosts |
| 666 | For ssh, |
| 667 | this file is exactly the same as for |
| 668 | .Pa .rhosts . |
| 669 | However, this file is |
| 670 | not used by rlogin and rshd, so using this permits access using SSH only. |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 671 | .It Pa /etc/hosts.equiv |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 672 | This file is used during |
| 673 | .Pa .rhosts |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 674 | authentication. |
| 675 | In the simplest form, this file contains host names, one per line. |
| 676 | Users on |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 677 | those hosts are permitted to log in without a password, provided they |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 678 | have the same user name on both machines. |
| 679 | The host name may also be |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 680 | followed by a user name; such users are permitted to log in as |
| 681 | .Em any |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 682 | user on this machine (except root). |
| 683 | Additionally, the syntax |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 684 | .Dq +@group |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 685 | can be used to specify netgroups. |
| 686 | Negated entries start with |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 687 | .Ql \&- . |
| 688 | .Pp |
| 689 | If the client host/user is successfully matched in this file, login is |
| 690 | automatically permitted provided the client and server user names are the |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 691 | same. |
| 692 | Additionally, successful RSA host authentication is normally required. |
| 693 | This file must be writable only by root; it is recommended |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 694 | that it be world-readable. |
| 695 | .Pp |
| 696 | .Sy "Warning: It is almost never a good idea to use user names in" |
| 697 | .Pa hosts.equiv . |
| 698 | Beware that it really means that the named user(s) can log in as |
| 699 | .Em anybody , |
| 700 | which includes bin, daemon, adm, and other accounts that own critical |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 701 | binaries and directories. |
| 702 | Using a user name practically grants the user root access. |
| 703 | The only valid use for user names that I can think |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 704 | of is in negative entries. |
| 705 | .Pp |
| 706 | Note that this warning also applies to rsh/rlogin. |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 707 | .It Pa /etc/shosts.equiv |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 708 | This is processed exactly as |
| 709 | .Pa /etc/hosts.equiv . |
| 710 | However, this file may be useful in environments that want to run both |
| 711 | rsh/rlogin and ssh. |
| 712 | .It Pa $HOME/.ssh/environment |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 713 | This file is read into the environment at login (if it exists). |
| 714 | It can only contain empty lines, comment lines (that start with |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 715 | .Ql # ) , |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 716 | and assignment lines of the form name=value. |
| 717 | The file should be writable |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 718 | only by the user; it need not be readable by anyone else. |
Ben Lindstrom | bd9bf38 | 2002-08-20 18:54:20 +0000 | [diff] [blame] | 719 | Environment processing is disabled by default and is |
| 720 | controlled via the |
| 721 | .Cm PermitUserEnvironment |
| 722 | option. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 723 | .It Pa $HOME/.ssh/rc |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 724 | If this file exists, it is run with |
| 725 | .Pa /bin/sh |
| 726 | after reading the |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 727 | environment files but before starting the user's shell or command. |
Ben Lindstrom | a11e270 | 2002-04-05 22:18:48 +0000 | [diff] [blame] | 728 | It must not produce any output on stdout; stderr must be used |
| 729 | instead. |
| 730 | If X11 forwarding is in use, it will receive the "proto cookie" pair in |
| 731 | its standard input (and |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 732 | .Ev DISPLAY |
Ben Lindstrom | a11e270 | 2002-04-05 22:18:48 +0000 | [diff] [blame] | 733 | in its environment). |
| 734 | The script must call |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 735 | .Xr xauth 1 |
Ben Lindstrom | a11e270 | 2002-04-05 22:18:48 +0000 | [diff] [blame] | 736 | because |
| 737 | .Nm |
| 738 | will not run xauth automatically to add X11 cookies. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 739 | .Pp |
| 740 | The primary purpose of this file is to run any initialization routines |
| 741 | which may be needed before the user's home directory becomes |
| 742 | accessible; AFS is a particular example of such an environment. |
| 743 | .Pp |
| 744 | This file will probably contain some initialization code followed by |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 745 | something similar to: |
| 746 | .Bd -literal |
Ben Lindstrom | a11e270 | 2002-04-05 22:18:48 +0000 | [diff] [blame] | 747 | if read proto cookie && [ -n "$DISPLAY" ]; then |
| 748 | if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then |
| 749 | # X11UseLocalhost=yes |
Damien Miller | dcbb6c2 | 2002-09-25 12:20:52 +1000 | [diff] [blame] | 750 | echo add unix:`echo $DISPLAY | |
Ben Lindstrom | a11e270 | 2002-04-05 22:18:48 +0000 | [diff] [blame] | 751 | cut -c11-` $proto $cookie |
| 752 | else |
| 753 | # X11UseLocalhost=no |
Damien Miller | dcbb6c2 | 2002-09-25 12:20:52 +1000 | [diff] [blame] | 754 | echo add $DISPLAY $proto $cookie |
| 755 | fi | xauth -q - |
Ben Lindstrom | a11e270 | 2002-04-05 22:18:48 +0000 | [diff] [blame] | 756 | fi |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 757 | .Ed |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 758 | .Pp |
| 759 | If this file does not exist, |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 760 | .Pa /etc/ssh/sshrc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 761 | is run, and if that |
Ben Lindstrom | a11e270 | 2002-04-05 22:18:48 +0000 | [diff] [blame] | 762 | does not exist either, xauth is used to add the cookie. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 763 | .Pp |
| 764 | This file should be writable only by the user, and need not be |
| 765 | readable by anyone else. |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 766 | .It Pa /etc/ssh/sshrc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 767 | Like |
| 768 | .Pa $HOME/.ssh/rc . |
| 769 | This can be used to specify |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 770 | machine-specific login-time initializations globally. |
| 771 | This file should be writable only by root, and should be world-readable. |
Damien Miller | 3702396 | 2000-07-11 17:31:38 +1000 | [diff] [blame] | 772 | .El |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 773 | .Sh SEE ALSO |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 774 | .Xr scp 1 , |
Damien Miller | 3380426 | 2001-02-04 23:20:18 +1100 | [diff] [blame] | 775 | .Xr sftp 1 , |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 776 | .Xr ssh 1 , |
| 777 | .Xr ssh-add 1 , |
| 778 | .Xr ssh-agent 1 , |
| 779 | .Xr ssh-keygen 1 , |
Ben Lindstrom | c8e29ce | 2001-08-06 20:55:28 +0000 | [diff] [blame] | 780 | .Xr login.conf 5 , |
| 781 | .Xr moduli 5 , |
Ben Lindstrom | 9f04903 | 2002-06-21 00:59:05 +0000 | [diff] [blame] | 782 | .Xr sshd_config 5 , |
Ben Lindstrom | d2bf0d6 | 2001-06-25 04:10:54 +0000 | [diff] [blame] | 783 | .Xr sftp-server 8 |
Ben Lindstrom | 160ec62 | 2001-04-22 17:17:46 +0000 | [diff] [blame] | 784 | .Rs |
| 785 | .%A T. Ylonen |
| 786 | .%A T. Kivinen |
| 787 | .%A M. Saarinen |
| 788 | .%A T. Rinne |
| 789 | .%A S. Lehtinen |
| 790 | .%T "SSH Protocol Architecture" |
Ben Lindstrom | f181384 | 2002-03-27 17:18:31 +0000 | [diff] [blame] | 791 | .%N draft-ietf-secsh-architecture-12.txt |
| 792 | .%D January 2002 |
Ben Lindstrom | 160ec62 | 2001-04-22 17:17:46 +0000 | [diff] [blame] | 793 | .%O work in progress material |
| 794 | .Re |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 795 | .Rs |
| 796 | .%A M. Friedl |
| 797 | .%A N. Provos |
| 798 | .%A W. A. Simpson |
| 799 | .%T "Diffie-Hellman Group Exchange for the SSH Transport Layer Protocol" |
Ben Lindstrom | f181384 | 2002-03-27 17:18:31 +0000 | [diff] [blame] | 800 | .%N draft-ietf-secsh-dh-group-exchange-02.txt |
| 801 | .%D January 2002 |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 802 | .%O work in progress material |
| 803 | .Re |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 804 | .Sh AUTHORS |
| 805 | OpenSSH is a derivative of the original and free |
| 806 | ssh 1.2.12 release by Tatu Ylonen. |
| 807 | Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, |
| 808 | Theo de Raadt and Dug Song |
| 809 | removed many bugs, re-added newer features and |
| 810 | created OpenSSH. |
| 811 | Markus Friedl contributed the support for SSH |
| 812 | protocol versions 1.5 and 2.0. |
| 813 | Niels Provos and Markus Friedl contributed support |
| 814 | for privilege separation. |