Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1 | .\" -*- nroff -*- |
| 2 | .\" |
| 3 | .\" sshd.8.in |
| 4 | .\" |
| 5 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> |
| 6 | .\" |
| 7 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
| 8 | .\" All rights reserved |
| 9 | .\" |
| 10 | .\" Created: Sat Apr 22 21:55:14 1995 ylo |
| 11 | .\" |
Damien Miller | 7b28dc5 | 2000-09-05 13:34:53 +1100 | [diff] [blame] | 12 | .\" $Id: sshd.8,v 1.28 2000/09/05 02:34:54 djm Exp $ |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 13 | .\" |
| 14 | .Dd September 25, 1999 |
| 15 | .Dt SSHD 8 |
| 16 | .Os |
| 17 | .Sh NAME |
| 18 | .Nm sshd |
| 19 | .Nd secure shell daemon |
| 20 | .Sh SYNOPSIS |
| 21 | .Nm sshd |
Damien Miller | 34132e5 | 2000-01-14 15:45:46 +1100 | [diff] [blame] | 22 | .Op Fl diqQ46 |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 23 | .Op Fl b Ar bits |
| 24 | .Op Fl f Ar config_file |
| 25 | .Op Fl g Ar login_grace_time |
| 26 | .Op Fl h Ar host_key_file |
| 27 | .Op Fl k Ar key_gen_time |
| 28 | .Op Fl p Ar port |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 29 | .Op Fl u Ar len |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 30 | .Op Fl V Ar client_protocol_id |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 31 | .Sh DESCRIPTION |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 32 | .Nm |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 33 | (Secure Shell Daemon) is the daemon program for |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 34 | .Xr ssh 1 . |
Damien Miller | 35dabd0 | 2000-05-01 21:10:33 +1000 | [diff] [blame] | 35 | Together these programs replace rlogin and rsh, and |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 36 | provide secure encrypted communications between two untrusted hosts |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 37 | over an insecure network. |
| 38 | The programs are intended to be as easy to |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 39 | install and use as possible. |
| 40 | .Pp |
| 41 | .Nm |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 42 | is the daemon that listens for connections from clients. |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 43 | It is normally started at boot from |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 44 | .Pa /etc/rc . |
| 45 | It forks a new |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 46 | daemon for each incoming connection. |
| 47 | The forked daemons handle |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 48 | key exchange, encryption, authentication, command execution, |
| 49 | and data exchange. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 50 | This implementation of |
| 51 | .Nm |
| 52 | supports both SSH protocol version 1 and 2 simultaneously. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 53 | .Nm |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 54 | works as follows. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 55 | .Pp |
| 56 | .Ss SSH protocol version 1 |
| 57 | .Pp |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 58 | Each host has a host-specific RSA key |
| 59 | (normally 1024 bits) used to identify the host. |
| 60 | Additionally, when |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 61 | the daemon starts, it generates a server RSA key (normally 768 bits). |
| 62 | This key is normally regenerated every hour if it has been used, and |
| 63 | is never stored on disk. |
| 64 | .Pp |
Damien Miller | 35dabd0 | 2000-05-01 21:10:33 +1000 | [diff] [blame] | 65 | Whenever a client connects the daemon responds with its public |
| 66 | host and server keys. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 67 | The client compares the |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 68 | 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] | 69 | The client then generates a 256 bit random number. |
| 70 | It encrypts this |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 71 | 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] | 72 | the encrypted number to the server. |
Damien Miller | 35dabd0 | 2000-05-01 21:10:33 +1000 | [diff] [blame] | 73 | Both sides then use this |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 74 | 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] | 75 | communications in the session. |
| 76 | The rest of the session is encrypted |
Damien Miller | 35dabd0 | 2000-05-01 21:10:33 +1000 | [diff] [blame] | 77 | using a conventional cipher, currently Blowfish or 3DES, with 3DES |
Damien Miller | b38eff8 | 2000-04-01 11:09:21 +1000 | [diff] [blame] | 78 | being used by default. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 79 | The client selects the encryption algorithm |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 80 | to use from those offered by the server. |
| 81 | .Pp |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 82 | Next, the server and the client enter an authentication dialog. |
| 83 | The client tries to authenticate itself using |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 84 | .Pa .rhosts |
| 85 | authentication, |
| 86 | .Pa .rhosts |
| 87 | authentication combined with RSA host |
| 88 | authentication, RSA challenge-response authentication, or password |
| 89 | based authentication. |
| 90 | .Pp |
| 91 | Rhosts authentication is normally disabled |
| 92 | because it is fundamentally insecure, but can be enabled in the server |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 93 | configuration file if desired. |
| 94 | System security is not improved unless |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 95 | .Xr rshd 8 , |
| 96 | .Xr rlogind 8 , |
| 97 | .Xr rexecd 8 , |
| 98 | and |
| 99 | .Xr rexd 8 |
| 100 | are disabled (thus completely disabling |
| 101 | .Xr rlogin 1 |
| 102 | and |
| 103 | .Xr rsh 1 |
Damien Miller | 35dabd0 | 2000-05-01 21:10:33 +1000 | [diff] [blame] | 104 | into the machine). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 105 | .Pp |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 106 | .Ss SSH protocol version 2 |
| 107 | .Pp |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 108 | Version 2 works similarly: |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 109 | Each host has a host-specific DSA key used to identify the host. |
| 110 | However, when the daemon starts, it does not generate a server key. |
| 111 | Forward security is provided through a Diffie-Hellman key agreement. |
| 112 | This key agreement results in a shared session key. |
| 113 | The rest of the session is encrypted |
| 114 | using a symmetric cipher, currently |
| 115 | Blowfish, 3DES or CAST128 in CBC mode or Arcfour. |
| 116 | The client selects the encryption algorithm |
| 117 | to use from those offered by the server. |
| 118 | Additionally, session integrity is provided |
Damien Miller | 30c3d42 | 2000-05-09 11:02:59 +1000 | [diff] [blame] | 119 | through a cryptographic message authentication code |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 120 | (hmac-sha1 or hmac-md5). |
| 121 | .Pp |
| 122 | Protocol version 2 provides a public key based |
| 123 | user authentication method (DSAAuthentication) |
| 124 | and conventional password authentication. |
| 125 | .Pp |
| 126 | .Ss Command execution and data forwarding |
| 127 | .Pp |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 128 | If the client successfully authenticates itself, a dialog for |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 129 | preparing the session is entered. |
| 130 | At this time the client may request |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 131 | things like allocating a pseudo-tty, forwarding X11 connections, |
| 132 | forwarding TCP/IP connections, or forwarding the authentication agent |
| 133 | connection over the secure channel. |
| 134 | .Pp |
| 135 | Finally, the client either requests a shell or execution of a command. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 136 | The sides then enter session mode. |
| 137 | In this mode, either side may send |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 138 | data at any time, and such data is forwarded to/from the shell or |
| 139 | command on the server side, and the user terminal in the client side. |
| 140 | .Pp |
| 141 | When the user program terminates and all forwarded X11 and other |
| 142 | connections have been closed, the server sends command exit status to |
| 143 | the client, and both sides exit. |
| 144 | .Pp |
| 145 | .Nm |
| 146 | can be configured using command-line options or a configuration |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 147 | file. |
| 148 | Command-line options override values specified in the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 149 | configuration file. |
| 150 | .Pp |
Damien Miller | 6162d12 | 1999-11-21 13:23:52 +1100 | [diff] [blame] | 151 | .Nm |
| 152 | rereads its configuration file when it receives a hangup signal, |
| 153 | .Dv SIGHUP . |
| 154 | .Pp |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 155 | The options are as follows: |
| 156 | .Bl -tag -width Ds |
| 157 | .It Fl b Ar bits |
| 158 | Specifies the number of bits in the server key (default 768). |
| 159 | .Pp |
| 160 | .It Fl d |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 161 | Debug mode. |
| 162 | The server sends verbose debug output to the system |
| 163 | log, and does not put itself in the background. |
| 164 | The server also will not fork and will only process one connection. |
| 165 | This option is only intended for debugging for the server. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 166 | .It Fl f Ar configuration_file |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 167 | Specifies the name of the configuration file. |
| 168 | The default is |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 169 | .Pa /etc/sshd_config . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 170 | .Nm |
| 171 | refuses to start if there is no configuration file. |
| 172 | .It Fl g Ar login_grace_time |
| 173 | Gives the grace time for clients to authenticate themselves (default |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 174 | 300 seconds). |
| 175 | If the client fails to authenticate the user within |
| 176 | this many seconds, the server disconnects and exits. |
| 177 | A value of zero indicates no limit. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 178 | .It Fl h Ar host_key_file |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 179 | Specifies the file from which the RSA host key is read (default |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 180 | .Pa /etc/ssh_host_key ) . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 181 | This option must be given if |
| 182 | .Nm |
| 183 | is not run as root (as the normal |
| 184 | host file is normally not readable by anyone but root). |
| 185 | .It Fl i |
| 186 | Specifies that |
| 187 | .Nm |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 188 | is being run from inetd. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 189 | .Nm |
| 190 | is normally not run |
| 191 | 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] | 192 | respond to the client, and this may take tens of seconds. |
| 193 | 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] | 194 | However, with small key sizes (e.g., 512) using |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 195 | .Nm |
| 196 | from inetd may |
| 197 | be feasible. |
| 198 | .It Fl k Ar key_gen_time |
| 199 | Specifies how often the server key is regenerated (default 3600 |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 200 | seconds, or one hour). |
| 201 | The motivation for regenerating the key fairly |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 202 | often is that the key is not stored anywhere, and after about an hour, |
| 203 | it becomes impossible to recover the key for decrypting intercepted |
| 204 | communications even if the machine is cracked into or physically |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 205 | seized. |
| 206 | A value of zero indicates that the key will never be regenerated. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 207 | .It Fl p Ar port |
| 208 | Specifies the port on which the server listens for connections |
| 209 | (default 22). |
| 210 | .It Fl q |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 211 | Quiet mode. |
| 212 | Nothing is sent to the system log. |
| 213 | Normally the beginning, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 214 | authentication, and termination of each connection is logged. |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 215 | .It Fl u Ar len |
| 216 | This option is used to specify the size of the field |
| 217 | in the |
| 218 | .Li utmp |
| 219 | structure that holds the remote host name. |
| 220 | If the resolved host name is longer than |
| 221 | .Ar len , |
| 222 | the dotted decimal value will be used instead. |
| 223 | This allows hosts with very long host names that |
| 224 | overflow this field to still be uniquely identified. |
| 225 | Specifying |
| 226 | .Fl u0 |
| 227 | indicates that only dotted decimal addresses |
| 228 | should be put into the |
| 229 | .Pa utmp |
| 230 | file. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 231 | .It Fl Q |
| 232 | Do not print an error message if RSA support is missing. |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 233 | .It Fl V Ar client_protocol_id |
| 234 | SSH2 compatibility mode. |
Damien Miller | 35dabd0 | 2000-05-01 21:10:33 +1000 | [diff] [blame] | 235 | When this option is specified |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 236 | .Nm |
Damien Miller | 35dabd0 | 2000-05-01 21:10:33 +1000 | [diff] [blame] | 237 | assumes the client has sent the supplied version string |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 238 | and skips the |
| 239 | Protocol Version Identification Exchange. |
Damien Miller | 34132e5 | 2000-01-14 15:45:46 +1100 | [diff] [blame] | 240 | .It Fl 4 |
| 241 | Forces |
| 242 | .Nm |
| 243 | to use IPv4 addresses only. |
| 244 | .It Fl 6 |
| 245 | Forces |
| 246 | .Nm |
| 247 | to use IPv6 addresses only. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 248 | .El |
| 249 | .Sh CONFIGURATION FILE |
| 250 | .Nm |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 251 | reads configuration data from |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 252 | .Pa /etc/sshd_config |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 253 | (or the file specified with |
| 254 | .Fl f |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 255 | on the command line). |
| 256 | The file contains keyword-value pairs, one per line. |
| 257 | Lines starting with |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 258 | .Ql # |
| 259 | and empty lines are interpreted as comments. |
| 260 | .Pp |
| 261 | The following keywords are possible. |
| 262 | .Bl -tag -width Ds |
| 263 | .It Cm AFSTokenPassing |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 264 | Specifies whether an AFS token may be forwarded to the server. |
| 265 | Default is |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 266 | .Dq yes . |
| 267 | .It Cm AllowGroups |
| 268 | This keyword can be followed by a number of group names, separated |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 269 | by spaces. |
| 270 | If specified, login is allowed only for users whose primary |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 271 | group matches one of the patterns. |
| 272 | .Ql \&* |
| 273 | and |
| 274 | .Ql ? |
| 275 | can be used as |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 276 | wildcards in the patterns. |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 277 | Only group names are valid; a numerical group ID isn't recognized. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 278 | By default login is allowed regardless of the primary group. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 279 | .Pp |
| 280 | .It Cm AllowUsers |
| 281 | This keyword can be followed by a number of user names, separated |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 282 | by spaces. |
| 283 | If specified, login is allowed only for users names that |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 284 | match one of the patterns. |
| 285 | .Ql \&* |
| 286 | and |
| 287 | .Ql ? |
| 288 | can be used as |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 289 | wildcards in the patterns. |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 290 | Only user names are valid; a numerical user ID isn't recognized. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 291 | By default login is allowed regardless of the user name. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 292 | .Pp |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 293 | .It Cm Ciphers |
| 294 | Specifies the ciphers allowed for protocol version 2. |
| 295 | Multiple ciphers must be comma-separated. |
| 296 | The default is |
Damien Miller | 30c3d42 | 2000-05-09 11:02:59 +1000 | [diff] [blame] | 297 | .Dq 3des-cbc,blowfish-cbc,arcfour,cast128-cbc . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 298 | .It Cm CheckMail |
| 299 | Specifies whether |
| 300 | .Nm |
| 301 | should check for new mail for interactive logins. |
| 302 | The default is |
| 303 | .Dq no . |
| 304 | .It Cm DenyGroups |
| 305 | This keyword can be followed by a number of group names, separated |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 306 | by spaces. |
| 307 | Users whose primary group matches one of the patterns |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 308 | aren't allowed to log in. |
| 309 | .Ql \&* |
| 310 | and |
| 311 | .Ql ? |
| 312 | can be used as |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 313 | wildcards in the patterns. |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 314 | Only group names are valid; a numerical group ID isn't recognized. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 315 | By default login is allowed regardless of the primary group. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 316 | .Pp |
| 317 | .It Cm DenyUsers |
| 318 | This keyword can be followed by a number of user names, separated |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 319 | by spaces. |
| 320 | Login is disallowed for user names that match one of the patterns. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 321 | .Ql \&* |
| 322 | and |
| 323 | .Ql ? |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 324 | can be used as wildcards in the patterns. |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 325 | Only user names are valid; a numerical user ID isn't recognized. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 326 | By default login is allowed regardless of the user name. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 327 | .It Cm DSAAuthentication |
| 328 | Specifies whether DSA authentication is allowed. |
| 329 | The default is |
| 330 | .Dq yes . |
| 331 | Note that this option applies to protocol version 2 only. |
| 332 | .It Cm GatewayPorts |
| 333 | Specifies whether remote hosts are allowed to connect to ports |
| 334 | forwarded for the client. |
| 335 | The argument must be |
| 336 | .Dq yes |
| 337 | or |
| 338 | .Dq no . |
| 339 | The default is |
| 340 | .Dq no . |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 341 | .It Cm HostDSAKey |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 342 | Specifies the file containing the private DSA host key (default |
| 343 | .Pa /etc/ssh_host_dsa_key ) |
| 344 | used by SSH protocol 2.0. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 345 | Note that |
| 346 | .Nm |
Damien Miller | 30c3d42 | 2000-05-09 11:02:59 +1000 | [diff] [blame] | 347 | disables protocol 2.0 if this file is group/world-accessible. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 348 | .It Cm HostKey |
| 349 | Specifies the file containing the private RSA host key (default |
| 350 | .Pa /etc/ssh_host_key ) |
| 351 | used by SSH protocols 1.3 and 1.5. |
| 352 | Note that |
| 353 | .Nm |
Damien Miller | 30c3d42 | 2000-05-09 11:02:59 +1000 | [diff] [blame] | 354 | disables protocols 1.3 and 1.5 if this file is group/world-accessible. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 355 | .It Cm IgnoreRhosts |
Damien Miller | 98c7ad6 | 2000-03-09 21:27:49 +1100 | [diff] [blame] | 356 | Specifies that |
| 357 | .Pa .rhosts |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 358 | and |
Damien Miller | 98c7ad6 | 2000-03-09 21:27:49 +1100 | [diff] [blame] | 359 | .Pa .shosts |
| 360 | files will not be used in authentication. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 361 | .Pa /etc/hosts.equiv |
| 362 | and |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 363 | .Pa /etc/shosts.equiv |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 364 | are still used. |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 365 | The default is |
Damien Miller | 98c7ad6 | 2000-03-09 21:27:49 +1100 | [diff] [blame] | 366 | .Dq yes . |
Damien Miller | 3226509 | 1999-11-12 11:33:04 +1100 | [diff] [blame] | 367 | .It Cm IgnoreUserKnownHosts |
| 368 | Specifies whether |
| 369 | .Nm |
| 370 | should ignore the user's |
| 371 | .Pa $HOME/.ssh/known_hosts |
| 372 | during |
| 373 | .Cm RhostsRSAAuthentication . |
| 374 | The default is |
| 375 | .Dq no . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 376 | .It Cm KeepAlive |
| 377 | Specifies whether the system should send keepalive messages to the |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 378 | other side. |
| 379 | If they are sent, death of the connection or crash of one |
| 380 | of the machines will be properly noticed. |
| 381 | However, this means that |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 382 | connections will die if the route is down temporarily, and some people |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 383 | find it annoying. |
Damien Miller | 30c3d42 | 2000-05-09 11:02:59 +1000 | [diff] [blame] | 384 | On the other hand, if keepalives are not sent, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 385 | sessions may hang indefinitely on the server, leaving |
| 386 | .Dq ghost |
| 387 | users and consuming server resources. |
| 388 | .Pp |
| 389 | The default is |
| 390 | .Dq yes |
| 391 | (to send keepalives), and the server will notice |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 392 | if the network goes down or the client host reboots. |
| 393 | This avoids infinitely hanging sessions. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 394 | .Pp |
| 395 | To disable keepalives, the value should be set to |
| 396 | .Dq no |
| 397 | in both the server and the client configuration files. |
| 398 | .It Cm KerberosAuthentication |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 399 | Specifies whether Kerberos authentication is allowed. |
| 400 | This can be in the form of a Kerberos ticket, or if |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 401 | .Cm PasswordAuthentication |
| 402 | is yes, the password provided by the user will be validated through |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 403 | the Kerberos KDC. To use this option, the server needs a |
| 404 | Kerberos servtab which allows the verification of the KDC's identity. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 405 | Default is |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 406 | .Dq yes . |
| 407 | .It Cm KerberosOrLocalPasswd |
| 408 | If set then if password authentication through Kerberos fails then |
| 409 | the password will be validated via any additional local mechanism |
| 410 | such as |
| 411 | .Pa /etc/passwd |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 412 | or SecurID. |
| 413 | Default is |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 414 | .Dq yes . |
| 415 | .It Cm KerberosTgtPassing |
| 416 | Specifies whether a Kerberos TGT may be forwarded to the server. |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 417 | Default is |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 418 | .Dq no , |
| 419 | as this only works when the Kerberos KDC is actually an AFS kaserver. |
| 420 | .It Cm KerberosTicketCleanup |
| 421 | Specifies whether to automatically destroy the user's ticket cache |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 422 | file on logout. |
| 423 | Default is |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 424 | .Dq yes . |
| 425 | .It Cm KeyRegenerationInterval |
| 426 | The server key is automatically regenerated after this many seconds |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 427 | (if it has been used). |
| 428 | The purpose of regeneration is to prevent |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 429 | decrypting captured sessions by later breaking into the machine and |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 430 | stealing the keys. |
| 431 | The key is never stored anywhere. |
| 432 | If the value is 0, the key is never regenerated. |
| 433 | The default is 3600 (seconds). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 434 | .It Cm ListenAddress |
| 435 | Specifies what local address |
| 436 | .Nm |
| 437 | should listen on. |
| 438 | The default is to listen to all local addresses. |
Damien Miller | 34132e5 | 2000-01-14 15:45:46 +1100 | [diff] [blame] | 439 | Multiple options of this type are permitted. |
| 440 | Additionally, the |
| 441 | .Cm Ports |
| 442 | options must precede this option. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 443 | .It Cm LoginGraceTime |
| 444 | The server disconnects after this time if the user has not |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 445 | successfully logged in. |
| 446 | If the value is 0, there is no time limit. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 447 | The default is 600 (seconds). |
Damien Miller | 5ce662a | 1999-11-11 17:57:39 +1100 | [diff] [blame] | 448 | .It Cm LogLevel |
| 449 | Gives the verbosity level that is used when logging messages from |
| 450 | .Nm sshd . |
| 451 | The possible values are: |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 452 | QUIET, FATAL, ERROR, INFO, VERBOSE and DEBUG. |
Damien Miller | 5ce662a | 1999-11-11 17:57:39 +1100 | [diff] [blame] | 453 | The default is INFO. |
| 454 | Logging with level DEBUG violates the privacy of users |
| 455 | and is not recommended. |
Damien Miller | 3702396 | 2000-07-11 17:31:38 +1000 | [diff] [blame] | 456 | .It Cm MaxStartups |
| 457 | Specifies the maximum number of concurrent unauthenticated connections to the |
| 458 | .Nm |
| 459 | daemon. |
| 460 | Additional connections will be dropped until authentication succeeds or the |
| 461 | .Cm LoginGraceTime |
| 462 | expires for a connection. |
| 463 | The default is 10. |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 464 | .Pp |
| 465 | Alternatively, random early drop can be enabled by specifying |
| 466 | the three colon separated values |
| 467 | .Dq start:rate:full |
| 468 | (e.g. "10:30:60"). |
| 469 | .Nm |
| 470 | will refuse connection attempts with a probabillity of |
| 471 | .Dq rate/100 |
| 472 | (30%) |
| 473 | if there are currently |
| 474 | .Dq start |
| 475 | (10) |
| 476 | unauthenticated connections. |
| 477 | The probabillity increases linearly and all connection attempts |
| 478 | are refused if the number of unauthenticated connections reaches |
| 479 | .Dq full |
| 480 | (60). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 481 | .It Cm PasswordAuthentication |
| 482 | Specifies whether password authentication is allowed. |
| 483 | The default is |
| 484 | .Dq yes . |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 485 | Note that this option applies to both protocol versions 1 and 2. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 486 | .It Cm PermitEmptyPasswords |
| 487 | When password authentication is allowed, it specifies whether the |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 488 | server allows login to accounts with empty password strings. |
| 489 | The default is |
Damien Miller | 98c7ad6 | 2000-03-09 21:27:49 +1100 | [diff] [blame] | 490 | .Dq no . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 491 | .It Cm PermitRootLogin |
| 492 | Specifies whether the root can log in using |
| 493 | .Xr ssh 1 . |
| 494 | The argument must be |
| 495 | .Dq yes , |
| 496 | .Dq without-password |
| 497 | or |
| 498 | .Dq no . |
| 499 | The default is |
| 500 | .Dq yes . |
| 501 | If this options is set to |
| 502 | .Dq without-password |
| 503 | only password authentication is disabled for root. |
| 504 | .Pp |
| 505 | Root login with RSA authentication when the |
| 506 | .Ar command |
| 507 | option has been |
| 508 | specified will be allowed regardless of the value of this setting |
| 509 | (which may be useful for taking remote backups even if root login is |
| 510 | normally not allowed). |
Damien Miller | 6f83b8e | 2000-05-02 09:23:45 +1000 | [diff] [blame] | 511 | .It Cm PidFile |
| 512 | Specifies the file that contains the process identifier of the |
| 513 | .Nm |
| 514 | daemon. |
| 515 | The default is |
| 516 | .Pa /var/run/sshd.pid . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 517 | .It Cm Port |
| 518 | Specifies the port number that |
| 519 | .Nm |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 520 | listens on. |
| 521 | The default is 22. |
Damien Miller | 34132e5 | 2000-01-14 15:45:46 +1100 | [diff] [blame] | 522 | Multiple options of this type are permitted. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 523 | .It Cm PrintMotd |
| 524 | Specifies whether |
| 525 | .Nm |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 526 | should print |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 527 | .Pa /etc/motd |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 528 | when a user logs in interactively. |
| 529 | (On some systems it is also printed by the shell, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 530 | .Pa /etc/profile , |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 531 | or equivalent.) |
| 532 | The default is |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 533 | .Dq yes . |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 534 | .It Cm Protocol |
| 535 | Specifies the protocol versions |
| 536 | .Nm |
| 537 | should support. |
| 538 | The possible values are |
| 539 | .Dq 1 |
| 540 | and |
| 541 | .Dq 2 . |
| 542 | Multiple versions must be comma-separated. |
| 543 | The default is |
| 544 | .Dq 1 . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 545 | .It Cm RandomSeed |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 546 | Obsolete. |
| 547 | Random number generation uses other techniques. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 548 | .It Cm RhostsAuthentication |
| 549 | Specifies whether authentication using rhosts or /etc/hosts.equiv |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 550 | files is sufficient. |
| 551 | Normally, this method should not be permitted because it is insecure. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 552 | .Cm RhostsRSAAuthentication |
| 553 | should be used |
| 554 | instead, because it performs RSA-based host authentication in addition |
| 555 | to normal rhosts or /etc/hosts.equiv authentication. |
| 556 | The default is |
| 557 | .Dq no . |
| 558 | .It Cm RhostsRSAAuthentication |
| 559 | Specifies whether rhosts or /etc/hosts.equiv authentication together |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 560 | with successful RSA host authentication is allowed. |
| 561 | The default is |
Damien Miller | 98c7ad6 | 2000-03-09 21:27:49 +1100 | [diff] [blame] | 562 | .Dq no . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 563 | .It Cm RSAAuthentication |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 564 | Specifies whether pure RSA authentication is allowed. |
| 565 | The default is |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 566 | .Dq yes . |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 567 | Note that this option applies to protocol version 1 only. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 568 | .It Cm ServerKeyBits |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 569 | Defines the number of bits in the server key. |
| 570 | The minimum value is 512, and the default is 768. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 571 | .It Cm SkeyAuthentication |
| 572 | Specifies whether |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 573 | .Xr skey 1 |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 574 | authentication is allowed. |
| 575 | The default is |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 576 | .Dq yes . |
| 577 | Note that s/key authentication is enabled only if |
| 578 | .Cm PasswordAuthentication |
| 579 | is allowed, too. |
| 580 | .It Cm StrictModes |
| 581 | Specifies whether |
| 582 | .Nm |
| 583 | should check file modes and ownership of the |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 584 | user's files and home directory before accepting login. |
| 585 | This is normally desirable because novices sometimes accidentally leave their |
| 586 | directory or files world-writable. |
| 587 | The default is |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 588 | .Dq yes . |
Damien Miller | f6d9e22 | 2000-06-18 14:50:44 +1000 | [diff] [blame] | 589 | .It Cm Subsystem |
| 590 | Configures an external subsystem (e.g. file transfer daemon). |
| 591 | Arguments should be a subsystem name and a command to execute upon subsystem request. |
Damien Miller | 7b28dc5 | 2000-09-05 13:34:53 +1100 | [diff] [blame] | 592 | The command |
| 593 | .Xr sftp-server 8 |
| 594 | implements the |
| 595 | .Dq sftp |
| 596 | file transfer subsystem. |
Damien Miller | f6d9e22 | 2000-06-18 14:50:44 +1000 | [diff] [blame] | 597 | By default no subsystems are defined. |
| 598 | Note that this option applies to protocol version 2 only. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 599 | .It Cm SyslogFacility |
| 600 | Gives the facility code that is used when logging messages from |
| 601 | .Nm sshd . |
| 602 | The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2, |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 603 | LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. |
| 604 | The default is AUTH. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 605 | .It Cm UseLogin |
| 606 | Specifies whether |
| 607 | .Xr login 1 |
Damien Miller | d3a1857 | 2000-06-07 19:55:44 +1000 | [diff] [blame] | 608 | is used for interactive login sessions. |
| 609 | Note that |
| 610 | .Xr login 1 |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 611 | is never used for remote command execution. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 612 | The default is |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 613 | .Dq no . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 614 | .It Cm X11DisplayOffset |
| 615 | Specifies the first display number available for |
| 616 | .Nm sshd Ns 's |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 617 | X11 forwarding. |
| 618 | This prevents |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 619 | .Nm |
| 620 | from interfering with real X11 servers. |
Damien Miller | 98c7ad6 | 2000-03-09 21:27:49 +1100 | [diff] [blame] | 621 | The default is 10. |
Damien Miller | 396691a | 2000-01-20 22:44:08 +1100 | [diff] [blame] | 622 | .It Cm X11Forwarding |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 623 | Specifies whether X11 forwarding is permitted. |
| 624 | The default is |
Damien Miller | 98c7ad6 | 2000-03-09 21:27:49 +1100 | [diff] [blame] | 625 | .Dq no . |
Damien Miller | 396691a | 2000-01-20 22:44:08 +1100 | [diff] [blame] | 626 | Note that disabling X11 forwarding does not improve security in any |
| 627 | way, as users can always install their own forwarders. |
Damien Miller | d3a1857 | 2000-06-07 19:55:44 +1000 | [diff] [blame] | 628 | .It Cm XAuthLocation |
| 629 | Specifies the location of the |
| 630 | .Xr xauth 1 |
| 631 | program. |
| 632 | The default is |
| 633 | .Pa /usr/X11R6/bin/xauth . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 634 | .El |
| 635 | .Sh LOGIN PROCESS |
| 636 | When a user successfully logs in, |
| 637 | .Nm |
| 638 | does the following: |
| 639 | .Bl -enum -offset indent |
| 640 | .It |
| 641 | 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] | 642 | prints last login time and |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 643 | .Pa /etc/motd |
| 644 | (unless prevented in the configuration file or by |
| 645 | .Pa $HOME/.hushlogin ; |
| 646 | see the |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 647 | .Sx FILES |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 648 | section). |
| 649 | .It |
| 650 | If the login is on a tty, records login time. |
| 651 | .It |
| 652 | Checks |
| 653 | .Pa /etc/nologin ; |
| 654 | if it exists, prints contents and quits |
| 655 | (unless root). |
| 656 | .It |
| 657 | Changes to run with normal user privileges. |
| 658 | .It |
| 659 | Sets up basic environment. |
| 660 | .It |
| 661 | Reads |
| 662 | .Pa $HOME/.ssh/environment |
| 663 | if it exists. |
| 664 | .It |
| 665 | Changes to user's home directory. |
| 666 | .It |
| 667 | If |
| 668 | .Pa $HOME/.ssh/rc |
| 669 | exists, runs it; else if |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 670 | .Pa /etc/sshrc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 671 | exists, runs |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 672 | it; otherwise runs xauth. |
| 673 | The |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 674 | .Dq rc |
| 675 | files are given the X11 |
| 676 | authentication protocol and cookie in standard input. |
| 677 | .It |
| 678 | Runs user's shell or command. |
| 679 | .El |
| 680 | .Sh AUTHORIZED_KEYS FILE FORMAT |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 681 | The |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 682 | .Pa $HOME/.ssh/authorized_keys |
| 683 | file lists the RSA keys that are |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 684 | permitted for RSA authentication in SSH protocols 1.3 and 1.5 |
Damien Miller | 30c3d42 | 2000-05-09 11:02:59 +1000 | [diff] [blame] | 685 | Similarly, the |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 686 | .Pa $HOME/.ssh/authorized_keys2 |
| 687 | file lists the DSA keys that are |
| 688 | permitted for DSA authentication in SSH protocol 2.0. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 689 | Each line of the file contains one |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 690 | key (empty lines and lines starting with a |
| 691 | .Ql # |
| 692 | are ignored as |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 693 | comments). |
| 694 | Each line consists of the following fields, separated by |
| 695 | spaces: options, bits, exponent, modulus, comment. |
| 696 | The options field |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 697 | is optional; its presence is determined by whether the line starts |
| 698 | with a number or not (the option field never starts with a number). |
| 699 | The bits, exponent, modulus and comment fields give the RSA key; the |
| 700 | comment field is not used for anything (but may be convenient for the |
| 701 | user to identify the key). |
| 702 | .Pp |
| 703 | Note that lines in this file are usually several hundred bytes long |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 704 | (because of the size of the RSA key modulus). |
| 705 | You don't want to type them in; instead, copy the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 706 | .Pa identity.pub |
| 707 | file and edit it. |
| 708 | .Pp |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 709 | The options (if present) consist of comma-separated option |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 710 | specifications. |
| 711 | No spaces are permitted, except within double quotes. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 712 | The following option specifications are supported: |
| 713 | .Bl -tag -width Ds |
| 714 | .It Cm from="pattern-list" |
| 715 | Specifies that in addition to RSA authentication, the canonical name |
| 716 | 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] | 717 | patterns |
| 718 | .Pf ( Ql * |
| 719 | and |
| 720 | .Ql ? |
| 721 | serve as wildcards). |
| 722 | The list may also contain |
| 723 | patterns negated by prefixing them with |
| 724 | .Ql ! ; |
| 725 | if the canonical host name matches a negated pattern, the key is not accepted. |
| 726 | The purpose |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 727 | of this option is to optionally increase security: RSA authentication |
| 728 | by itself does not trust the network or name servers or anything (but |
| 729 | the key); however, if somebody somehow steals the key, the key |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 730 | permits an intruder to log in from anywhere in the world. |
| 731 | This additional option makes using a stolen key more difficult (name |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 732 | servers and/or routers would have to be compromised in addition to |
| 733 | just the key). |
| 734 | .It Cm command="command" |
| 735 | Specifies that the command is executed whenever this key is used for |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 736 | authentication. |
| 737 | The command supplied by the user (if any) is ignored. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 738 | The command is run on a pty if the connection requests a pty; |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 739 | otherwise it is run without a tty. |
| 740 | A quote may be included in the command by quoting it with a backslash. |
| 741 | This option might be useful |
| 742 | to restrict certain RSA keys to perform just a specific operation. |
| 743 | 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] | 744 | Note that the client may specify TCP/IP and/or X11 |
| 745 | forwarding unless they are explicitly prohibited. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 746 | .It Cm environment="NAME=value" |
| 747 | Specifies that the string is to be added to the environment when |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 748 | logging in using this key. |
| 749 | Environment variables set this way |
| 750 | override other default environment values. |
| 751 | Multiple options of this type are permitted. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 752 | .It Cm no-port-forwarding |
| 753 | Forbids TCP/IP forwarding when this key is used for authentication. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 754 | Any port forward requests by the client will return an error. |
| 755 | This might be used, e.g., in connection with the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 756 | .Cm command |
| 757 | option. |
| 758 | .It Cm no-X11-forwarding |
| 759 | Forbids X11 forwarding when this key is used for authentication. |
| 760 | Any X11 forward requests by the client will return an error. |
| 761 | .It Cm no-agent-forwarding |
| 762 | Forbids authentication agent forwarding when this key is used for |
| 763 | authentication. |
| 764 | .It Cm no-pty |
| 765 | Prevents tty allocation (a request to allocate a pty will fail). |
| 766 | .El |
| 767 | .Ss Examples |
| 768 | 1024 33 12121.\|.\|.\|312314325 ylo@foo.bar |
| 769 | .Pp |
| 770 | from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23.\|.\|.\|2334 ylo@niksula |
| 771 | .Pp |
| 772 | command="dump /home",no-pty,no-port-forwarding 1024 33 23.\|.\|.\|2323 backup.hut.fi |
| 773 | .Sh SSH_KNOWN_HOSTS FILE FORMAT |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 774 | The |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 775 | .Pa /etc/ssh_known_hosts , |
| 776 | .Pa /etc/ssh_known_hosts2 , |
| 777 | .Pa $HOME/.ssh/known_hosts , |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 778 | and |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 779 | .Pa $HOME/.ssh/known_hosts2 |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 780 | files contain host public keys for all known hosts. |
| 781 | The global file should |
| 782 | be prepared by the administrator (optional), and the per-user file is |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 783 | maintained automatically: whenever the user connects from an unknown host |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 784 | its key is added to the per-user file. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 785 | .Pp |
| 786 | Each line in these files contains the following fields: hostnames, |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 787 | bits, exponent, modulus, comment. |
| 788 | The fields are separated by spaces. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 789 | .Pp |
| 790 | Hostnames is a comma-separated list of patterns ('*' and '?' act as |
| 791 | wildcards); each pattern in turn is matched against the canonical host |
| 792 | name (when authenticating a client) or against the user-supplied |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 793 | name (when authenticating a server). |
| 794 | A pattern may also be preceded by |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 795 | .Ql ! |
| 796 | to indicate negation: if the host name matches a negated |
| 797 | pattern, it is not accepted (by that line) even if it matched another |
| 798 | pattern on the line. |
| 799 | .Pp |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 800 | 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] | 801 | can be obtained, e.g., from |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 802 | .Pa /etc/ssh_host_key.pub . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 803 | The optional comment field continues to the end of the line, and is not used. |
| 804 | .Pp |
| 805 | Lines starting with |
| 806 | .Ql # |
| 807 | and empty lines are ignored as comments. |
| 808 | .Pp |
| 809 | When performing host authentication, authentication is accepted if any |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 810 | matching line has the proper key. |
| 811 | It is thus permissible (but not |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 812 | recommended) to have several lines or different host keys for the same |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 813 | names. |
| 814 | This will inevitably happen when short forms of host names |
| 815 | from different domains are put in the file. |
| 816 | It is possible |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 817 | that the files contain conflicting information; authentication is |
| 818 | accepted if valid information can be found from either file. |
| 819 | .Pp |
| 820 | Note that the lines in these files are typically hundreds of characters |
| 821 | long, and you definitely don't want to type in the host keys by hand. |
| 822 | Rather, generate them by a script |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 823 | or by taking |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 824 | .Pa /etc/ssh_host_key.pub |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 825 | and adding the host names at the front. |
| 826 | .Ss Examples |
| 827 | closenet,closenet.hut.fi,.\|.\|.\|,130.233.208.41 1024 37 159.\|.\|.93 closenet.hut.fi |
| 828 | .Sh FILES |
| 829 | .Bl -tag -width Ds |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 830 | .It Pa /etc/sshd_config |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 831 | Contains configuration data for |
| 832 | .Nm sshd . |
| 833 | This file should be writable by root only, but it is recommended |
| 834 | (though not necessary) that it be world-readable. |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 835 | .It Pa /etc/ssh_host_key |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 836 | Contains the private part of the host key. |
| 837 | This file should only be owned by root, readable only by root, and not |
| 838 | accessible to others. |
| 839 | Note that |
| 840 | .Nm |
| 841 | does not start if this file is group/world-accessible. |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 842 | .It Pa /etc/ssh_host_key.pub |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 843 | Contains the public part of the host key. |
| 844 | This file should be world-readable but writable only by |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 845 | root. |
| 846 | Its contents should match the private part. |
| 847 | This file is not |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 848 | really used for anything; it is only provided for the convenience of |
| 849 | the user so its contents can be copied to known hosts files. |
| 850 | These two files are created using |
| 851 | .Xr ssh-keygen 1 . |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 852 | .It Pa /var/run/sshd.pid |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 853 | Contains the process ID of the |
| 854 | .Nm |
| 855 | listening for connections (if there are several daemons running |
| 856 | concurrently for different ports, this contains the pid of the one |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 857 | started last). |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 858 | 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] | 859 | .It Pa $HOME/.ssh/authorized_keys |
| 860 | Lists the RSA keys that can be used to log into the user's account. |
| 861 | This file must be readable by root (which may on some machines imply |
| 862 | it being world-readable if the user's home directory resides on an NFS |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 863 | volume). |
| 864 | It is recommended that it not be accessible by others. |
| 865 | The format of this file is described above. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 866 | Users will place the contents of their |
| 867 | .Pa identity.pub |
| 868 | files into this file, as described in |
| 869 | .Xr ssh-keygen 1 . |
| 870 | .It Pa $HOME/.ssh/authorized_keys2 |
| 871 | Lists the DSA keys that can be used to log into the user's account. |
| 872 | This file must be readable by root (which may on some machines imply |
| 873 | it being world-readable if the user's home directory resides on an NFS |
| 874 | volume). |
| 875 | It is recommended that it not be accessible by others. |
| 876 | The format of this file is described above. |
| 877 | Users will place the contents of their |
| 878 | .Pa id_dsa.pub |
| 879 | files into this file, as described in |
| 880 | .Xr ssh-keygen 1 . |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 881 | .It Pa "/etc/ssh_known_hosts" and "$HOME/.ssh/known_hosts" |
Damien Miller | 5ce662a | 1999-11-11 17:57:39 +1100 | [diff] [blame] | 882 | These files are consulted when using rhosts with RSA host |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 883 | authentication to check the public key of the host. |
| 884 | 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] | 885 | The client uses the same files |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 886 | to verify that the remote host is the one it intended to connect. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 887 | These files should be writable only by root/the owner. |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 888 | .Pa /etc/ssh_known_hosts |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 889 | should be world-readable, and |
| 890 | .Pa $HOME/.ssh/known_hosts |
| 891 | can but need not be world-readable. |
| 892 | .It Pa /etc/nologin |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 893 | If this file exists, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 894 | .Nm |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 895 | refuses to let anyone except root log in. |
| 896 | The contents of the file |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 897 | 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] | 898 | refused. |
| 899 | The file should be world-readable. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 900 | .It Pa /etc/hosts.allow, /etc/hosts.deny |
| 901 | If compiled with |
| 902 | .Sy LIBWRAP |
| 903 | support, tcp-wrappers access controls may be defined here as described in |
| 904 | .Xr hosts_access 5 . |
| 905 | .It Pa $HOME/.rhosts |
| 906 | This file contains host-username pairs, separated by a space, one per |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 907 | line. |
| 908 | The given user on the corresponding host is permitted to log in |
| 909 | without password. |
| 910 | The same file is used by rlogind and rshd. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 911 | The file must |
| 912 | be writable only by the user; it is recommended that it not be |
| 913 | accessible by others. |
| 914 | .Pp |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 915 | If is also possible to use netgroups in the file. |
| 916 | Either host or user |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 917 | name may be of the form +@groupname to specify all hosts or all users |
| 918 | in the group. |
| 919 | .It Pa $HOME/.shosts |
| 920 | For ssh, |
| 921 | this file is exactly the same as for |
| 922 | .Pa .rhosts . |
| 923 | However, this file is |
| 924 | 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] | 925 | .It Pa /etc/hosts.equiv |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 926 | This file is used during |
| 927 | .Pa .rhosts |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 928 | authentication. |
| 929 | In the simplest form, this file contains host names, one per line. |
| 930 | Users on |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 931 | those hosts are permitted to log in without a password, provided they |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 932 | have the same user name on both machines. |
| 933 | The host name may also be |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 934 | followed by a user name; such users are permitted to log in as |
| 935 | .Em any |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 936 | user on this machine (except root). |
| 937 | Additionally, the syntax |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 938 | .Dq +@group |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 939 | can be used to specify netgroups. |
| 940 | Negated entries start with |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 941 | .Ql \&- . |
| 942 | .Pp |
| 943 | If the client host/user is successfully matched in this file, login is |
| 944 | automatically permitted provided the client and server user names are the |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 945 | same. |
| 946 | Additionally, successful RSA host authentication is normally required. |
| 947 | This file must be writable only by root; it is recommended |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 948 | that it be world-readable. |
| 949 | .Pp |
| 950 | .Sy "Warning: It is almost never a good idea to use user names in" |
| 951 | .Pa hosts.equiv . |
| 952 | Beware that it really means that the named user(s) can log in as |
| 953 | .Em anybody , |
| 954 | which includes bin, daemon, adm, and other accounts that own critical |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 955 | binaries and directories. |
| 956 | Using a user name practically grants the user root access. |
| 957 | The only valid use for user names that I can think |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 958 | of is in negative entries. |
| 959 | .Pp |
| 960 | Note that this warning also applies to rsh/rlogin. |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 961 | .It Pa /etc/shosts.equiv |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 962 | This is processed exactly as |
| 963 | .Pa /etc/hosts.equiv . |
| 964 | However, this file may be useful in environments that want to run both |
| 965 | rsh/rlogin and ssh. |
| 966 | .It Pa $HOME/.ssh/environment |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 967 | This file is read into the environment at login (if it exists). |
| 968 | It can only contain empty lines, comment lines (that start with |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 969 | .Ql # ) , |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 970 | and assignment lines of the form name=value. |
| 971 | The file should be writable |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 972 | only by the user; it need not be readable by anyone else. |
| 973 | .It Pa $HOME/.ssh/rc |
| 974 | If this file exists, it is run with /bin/sh after reading the |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 975 | environment files but before starting the user's shell or command. |
| 976 | If X11 spoofing is in use, this will receive the "proto cookie" pair in |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 977 | standard input (and |
| 978 | .Ev DISPLAY |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 979 | in environment). |
| 980 | This must call |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 981 | .Xr xauth 1 |
| 982 | in that case. |
| 983 | .Pp |
| 984 | The primary purpose of this file is to run any initialization routines |
| 985 | which may be needed before the user's home directory becomes |
| 986 | accessible; AFS is a particular example of such an environment. |
| 987 | .Pp |
| 988 | This file will probably contain some initialization code followed by |
| 989 | something similar to: "if read proto cookie; then echo add $DISPLAY |
| 990 | $proto $cookie | xauth -q -; fi". |
| 991 | .Pp |
| 992 | If this file does not exist, |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 993 | .Pa /etc/sshrc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 994 | is run, and if that |
| 995 | does not exist either, xauth is used to store the cookie. |
| 996 | .Pp |
| 997 | This file should be writable only by the user, and need not be |
| 998 | readable by anyone else. |
Damien Miller | 886c63a | 2000-01-20 23:13:36 +1100 | [diff] [blame] | 999 | .It Pa /etc/sshrc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1000 | Like |
| 1001 | .Pa $HOME/.ssh/rc . |
| 1002 | This can be used to specify |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 1003 | machine-specific login-time initializations globally. |
| 1004 | 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] | 1005 | .El |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1006 | .Sh AUTHOR |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1007 | OpenSSH |
Damien Miller | 98c7ad6 | 2000-03-09 21:27:49 +1100 | [diff] [blame] | 1008 | is a derivative of the original (free) ssh 1.2.12 release by Tatu Ylonen, |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 1009 | but with bugs removed and newer features re-added. |
| 1010 | Rapidly after the |
Damien Miller | 98c7ad6 | 2000-03-09 21:27:49 +1100 | [diff] [blame] | 1011 | 1.2.12 release, newer versions of the original ssh bore successively |
| 1012 | more restrictive licenses, and thus demand for a free version was born. |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 1013 | .Pp |
Damien Miller | 98c7ad6 | 2000-03-09 21:27:49 +1100 | [diff] [blame] | 1014 | This version of OpenSSH |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1015 | .Bl -bullet |
| 1016 | .It |
Damien Miller | cfabe86 | 2000-04-20 23:27:27 +1000 | [diff] [blame] | 1017 | has all components of a restrictive nature (i.e., patents) |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1018 | directly removed from the source code; any licensed or patented components |
| 1019 | are chosen from |
| 1020 | external libraries. |
| 1021 | .It |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 1022 | has been updated to support SSH protocol 1.5 and 2, making it compatible with |
| 1023 | all other SSH clients and servers. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1024 | .It |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 1025 | contains added support for |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1026 | .Xr kerberos 8 |
| 1027 | authentication and ticket passing. |
| 1028 | .It |
| 1029 | supports one-time password authentication with |
| 1030 | .Xr skey 1 . |
| 1031 | .El |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 1032 | .Pp |
| 1033 | OpenSSH has been created by Aaron Campbell, Bob Beck, Markus Friedl, |
| 1034 | Niels Provos, Theo de Raadt, and Dug Song. |
| 1035 | .Pp |
| 1036 | The support for SSH protocol 2 was written by Markus Friedl. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1037 | .Sh SEE ALSO |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1038 | .Xr scp 1 , |
Damien Miller | 7b28dc5 | 2000-09-05 13:34:53 +1100 | [diff] [blame] | 1039 | .Xr sftp-server 8 , |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1040 | .Xr ssh 1 , |
| 1041 | .Xr ssh-add 1 , |
| 1042 | .Xr ssh-agent 1 , |
| 1043 | .Xr ssh-keygen 1 , |
Damien Miller | b38eff8 | 2000-04-01 11:09:21 +1000 | [diff] [blame] | 1044 | .Xr rlogin 1 , |
| 1045 | .Xr rsh 1 |