diff options
author | Colin Watson <cjwatson@debian.org> | 2003-09-01 01:47:17 +0000 |
---|---|---|
committer | Colin Watson <cjwatson@debian.org> | 2003-09-01 01:47:17 +0000 |
commit | 58657d96514cd6f16d82add8d6f4adbb36765758 (patch) | |
tree | b618adf8cafe8afd07b90ea24120d986b1d67dee /sshd.0 | |
parent | 1c992c4c13ea6c8fcd80093b340bc49753e17a4f (diff) | |
parent | d984a3c6658e950881edcfb2aae464add93f68d4 (diff) |
Import OpenSSH 3.5p1.
Diffstat (limited to 'sshd.0')
-rw-r--r-- | sshd.0 | 547 |
1 files changed, 547 insertions, 0 deletions
@@ -0,0 +1,547 @@ | |||
1 | SSHD(8) System Manager's Manual SSHD(8) | ||
2 | |||
3 | NAME | ||
4 | sshd - OpenSSH SSH daemon | ||
5 | |||
6 | SYNOPSIS | ||
7 | sshd [-deiqtD46] [-b bits] [-f config_file] [-g login_grace_time] | ||
8 | [-h host_key_file] [-k key_gen_time] [-o option] [-p port] [-u len] | ||
9 | |||
10 | DESCRIPTION | ||
11 | sshd (SSH Daemon) is the daemon program for ssh(1). Together these proM-- | ||
12 | grams replace rlogin and rsh, and provide secure encrypted communications | ||
13 | between two untrusted hosts over an insecure network. The programs are | ||
14 | intended to be as easy to install and use as possible. | ||
15 | |||
16 | sshd is the daemon that listens for connections from clients. It is norM-- | ||
17 | mally started at boot from /etc/rc. It forks a new daemon for each | ||
18 | incoming connection. The forked daemons handle key exchange, encryption, | ||
19 | authentication, command execution, and data exchange. This implementaM-- | ||
20 | tion of sshd supports both SSH protocol version 1 and 2 simultaneously. | ||
21 | sshd works as follows. | ||
22 | |||
23 | SSH protocol version 1 | ||
24 | |||
25 | Each host has a host-specific RSA key (normally 1024 bits) used to idenM-- | ||
26 | tify the host. Additionally, when the daemon starts, it generates a | ||
27 | server RSA key (normally 768 bits). This key is normally regenerated | ||
28 | every hour if it has been used, and is never stored on disk. | ||
29 | |||
30 | Whenever a client connects the daemon responds with its public host and | ||
31 | server keys. The client compares the RSA host key against its own | ||
32 | database to verify that it has not changed. The client then generates a | ||
33 | 256 bit random number. It encrypts this random number using both the | ||
34 | host key and the server key, and sends the encrypted number to the | ||
35 | server. Both sides then use this random number as a session key which is | ||
36 | used to encrypt all further communications in the session. The rest of | ||
37 | the session is encrypted using a conventional cipher, currently Blowfish | ||
38 | or 3DES, with 3DES being used by default. The client selects the encrypM-- | ||
39 | tion algorithm to use from those offered by the server. | ||
40 | |||
41 | Next, the server and the client enter an authentication dialog. The | ||
42 | client tries to authenticate itself using .rhosts authentication, .rhosts | ||
43 | authentication combined with RSA host authentication, RSA challenge- | ||
44 | response authentication, or password based authentication. | ||
45 | |||
46 | Rhosts authentication is normally disabled because it is fundamentally | ||
47 | insecure, but can be enabled in the server configuration file if desired. | ||
48 | System security is not improved unless rshd, rlogind, and rexecd are disM-- | ||
49 | abled (thus completely disabling rlogin and rsh into the machine). | ||
50 | |||
51 | SSH protocol version 2 | ||
52 | |||
53 | Version 2 works similarly: Each host has a host-specific key (RSA or DSA) | ||
54 | used to identify the host. However, when the daemon starts, it does not | ||
55 | generate a server key. Forward security is provided through a Diffie- | ||
56 | Hellman key agreement. This key agreement results in a shared session | ||
57 | key. | ||
58 | |||
59 | The rest of the session is encrypted using a symmetric cipher, currently | ||
60 | 128 bit AES, Blowfish, 3DES, CAST128, Arcfour, 192 bit AES, or 256 bit | ||
61 | AES. The client selects the encryption algorithm to use from those | ||
62 | offered by the server. Additionally, session integrity is provided | ||
63 | through a cryptographic message authentication code (hmac-sha1 or hmac- | ||
64 | md5). | ||
65 | |||
66 | Protocol version 2 provides a public key based user (PubkeyAuthenticaM-- | ||
67 | tion) or client host (HostbasedAuthentication) authentication method, | ||
68 | conventional password authentication and challenge response based methM-- | ||
69 | ods. | ||
70 | |||
71 | Command execution and data forwarding | ||
72 | |||
73 | If the client successfully authenticates itself, a dialog for preparing | ||
74 | the session is entered. At this time the client may request things like | ||
75 | allocating a pseudo-tty, forwarding X11 connections, forwarding TCP/IP | ||
76 | connections, or forwarding the authentication agent connection over the | ||
77 | secure channel. | ||
78 | |||
79 | Finally, the client either requests a shell or execution of a command. | ||
80 | The sides then enter session mode. In this mode, either side may send | ||
81 | data at any time, and such data is forwarded to/from the shell or command | ||
82 | on the server side, and the user terminal in the client side. | ||
83 | |||
84 | When the user program terminates and all forwarded X11 and other connecM-- | ||
85 | tions have been closed, the server sends command exit status to the | ||
86 | client, and both sides exit. | ||
87 | |||
88 | sshd can be configured using command-line options or a configuration | ||
89 | file. Command-line options override values specified in the configuraM-- | ||
90 | tion file. | ||
91 | |||
92 | sshd rereads its configuration file when it receives a hangup signal, | ||
93 | SIGHUP, by executing itself with the name it was started as, i.e., | ||
94 | /usr/sbin/sshd. | ||
95 | |||
96 | The options are as follows: | ||
97 | |||
98 | -b bits | ||
99 | Specifies the number of bits in the ephemeral protocol version 1 | ||
100 | server key (default 768). | ||
101 | |||
102 | -d Debug mode. The server sends verbose debug output to the system | ||
103 | log, and does not put itself in the background. The server also | ||
104 | will not fork and will only process one connection. This option | ||
105 | is only intended for debugging for the server. Multiple -d | ||
106 | options increase the debugging level. Maximum is 3. | ||
107 | |||
108 | -e When this option is specified, sshd will send the output to the | ||
109 | standard error instead of the system log. | ||
110 | |||
111 | -f configuration_file | ||
112 | Specifies the name of the configuration file. The default is | ||
113 | /etc/ssh/sshd_config. sshd refuses to start if there is no conM-- | ||
114 | figuration file. | ||
115 | |||
116 | -g login_grace_time | ||
117 | Gives the grace time for clients to authenticate themselves | ||
118 | (default 120 seconds). If the client fails to authenticate the | ||
119 | user within this many seconds, the server disconnects and exits. | ||
120 | A value of zero indicates no limit. | ||
121 | |||
122 | -h host_key_file | ||
123 | Specifies a file from which a host key is read. This option must | ||
124 | be given if sshd is not run as root (as the normal host key files | ||
125 | are normally not readable by anyone but root). The default is | ||
126 | /etc/ssh/ssh_host_key for protocol version 1, and | ||
127 | /etc/ssh/ssh_host_rsa_key and /etc/ssh/ssh_host_dsa_key for proM-- | ||
128 | tocol version 2. It is possible to have multiple host key files | ||
129 | for the different protocol versions and host key algorithms. | ||
130 | |||
131 | -i Specifies that sshd is being run from inetd. sshd is normally | ||
132 | not run from inetd because it needs to generate the server key | ||
133 | before it can respond to the client, and this may take tens of | ||
134 | seconds. Clients would have to wait too long if the key was | ||
135 | regenerated every time. However, with small key sizes (e.g., | ||
136 | 512) using sshd from inetd may be feasible. | ||
137 | |||
138 | -k key_gen_time | ||
139 | Specifies how often the ephemeral protocol version 1 server key | ||
140 | is regenerated (default 3600 seconds, or one hour). The motivaM-- | ||
141 | tion for regenerating the key fairly often is that the key is not | ||
142 | stored anywhere, and after about an hour, it becomes impossible | ||
143 | to recover the key for decrypting intercepted communications even | ||
144 | if the machine is cracked into or physically seized. A value of | ||
145 | zero indicates that the key will never be regenerated. | ||
146 | |||
147 | -o option | ||
148 | Can be used to give options in the format used in the configuraM-- | ||
149 | tion file. This is useful for specifying options for which there | ||
150 | is no separate command-line flag. | ||
151 | |||
152 | -p port | ||
153 | Specifies the port on which the server listens for connections | ||
154 | (default 22). Multiple port options are permitted. Ports speciM-- | ||
155 | fied in the configuration file are ignored when a command-line | ||
156 | port is specified. | ||
157 | |||
158 | -q Quiet mode. Nothing is sent to the system log. Normally the | ||
159 | beginning, authentication, and termination of each connection is | ||
160 | logged. | ||
161 | |||
162 | -t Test mode. Only check the validity of the configuration file and | ||
163 | sanity of the keys. This is useful for updating sshd reliably as | ||
164 | configuration options may change. | ||
165 | |||
166 | -u len This option is used to specify the size of the field in the utmp | ||
167 | structure that holds the remote host name. If the resolved host | ||
168 | name is longer than len, the dotted decimal value will be used | ||
169 | instead. This allows hosts with very long host names that overM-- | ||
170 | flow this field to still be uniquely identified. Specifying -u0 | ||
171 | indicates that only dotted decimal addresses should be put into | ||
172 | the utmp file. -u0 is also be used to prevent sshd from making | ||
173 | DNS requests unless the authentication mechanism or configuration | ||
174 | requires it. Authentication mechanisms that may require DNS | ||
175 | include RhostsAuthentication, RhostsRSAAuthentication, | ||
176 | HostbasedAuthentication and using a from="pattern-list" option in | ||
177 | a key file. Configuration options that require DNS include using | ||
178 | a USER@HOST pattern in AllowUsers or DenyUsers. | ||
179 | |||
180 | -D When this option is specified sshd will not detach and does not | ||
181 | become a daemon. This allows easy monitoring of sshd. | ||
182 | |||
183 | -4 Forces sshd to use IPv4 addresses only. | ||
184 | |||
185 | -6 Forces sshd to use IPv6 addresses only. | ||
186 | |||
187 | CONFIGURATION FILE | ||
188 | sshd reads configuration data from /etc/ssh/sshd_config (or the file | ||
189 | specified with -f on the command line). The file format and configuraM-- | ||
190 | tion options are described in sshd_config(5). | ||
191 | |||
192 | LOGIN PROCESS | ||
193 | When a user successfully logs in, sshd does the following: | ||
194 | |||
195 | 1. If the login is on a tty, and no command has been specified, | ||
196 | prints last login time and /etc/motd (unless prevented in the | ||
197 | configuration file or by $HOME/.hushlogin; see the FILES secM-- | ||
198 | tion). | ||
199 | |||
200 | 2. If the login is on a tty, records login time. | ||
201 | |||
202 | 3. Checks /etc/nologin; if it exists, prints contents and quits | ||
203 | (unless root). | ||
204 | |||
205 | 4. Changes to run with normal user privileges. | ||
206 | |||
207 | 5. Sets up basic environment. | ||
208 | |||
209 | 6. Reads $HOME/.ssh/environment if it exists and users are | ||
210 | allowed to change their environment. See the | ||
211 | PermitUserEnvironment option in sshd_config(5). | ||
212 | |||
213 | 7. Changes to user's home directory. | ||
214 | |||
215 | 8. If $HOME/.ssh/rc exists, runs it; else if /etc/ssh/sshrc | ||
216 | exists, runs it; otherwise runs xauth. The ``rc'' files are | ||
217 | given the X11 authentication protocol and cookie in standard | ||
218 | input. | ||
219 | |||
220 | 9. Runs user's shell or command. | ||
221 | |||
222 | AUTHORIZED_KEYS FILE FORMAT | ||
223 | $HOME/.ssh/authorized_keys is the default file that lists the public keys | ||
224 | that are permitted for RSA authentication in protocol version 1 and for | ||
225 | public key authentication (PubkeyAuthentication) in protocol version 2. | ||
226 | AuthorizedKeysFile may be used to specify an alternative file. | ||
227 | |||
228 | Each line of the file contains one key (empty lines and lines starting | ||
229 | with a `#' are ignored as comments). Each RSA public key consists of the | ||
230 | following fields, separated by spaces: options, bits, exponent, modulus, | ||
231 | comment. Each protocol version 2 public key consists of: options, keyM-- | ||
232 | type, base64 encoded key, comment. The options field is optional; its | ||
233 | presence is determined by whether the line starts with a number or not | ||
234 | (the options field never starts with a number). The bits, exponent, modM-- | ||
235 | ulus and comment fields give the RSA key for protocol version 1; the comM-- | ||
236 | ment field is not used for anything (but may be convenient for the user | ||
237 | to identify the key). For protocol version 2 the keytype is ``ssh-dss'' | ||
238 | or ``ssh-rsa''. | ||
239 | |||
240 | Note that lines in this file are usually several hundred bytes long | ||
241 | (because of the size of the public key encoding). You don't want to type | ||
242 | them in; instead, copy the identity.pub, id_dsa.pub or the id_rsa.pub | ||
243 | file and edit it. | ||
244 | |||
245 | sshd enforces a minimum RSA key modulus size for protocol 1 and protocol | ||
246 | 2 keys of 768 bits. | ||
247 | |||
248 | The options (if present) consist of comma-separated option specificaM-- | ||
249 | tions. No spaces are permitted, except within double quotes. The folM-- | ||
250 | lowing option specifications are supported (note that option keywords are | ||
251 | case-insensitive): | ||
252 | |||
253 | from="pattern-list" | ||
254 | Specifies that in addition to public key authentication, the | ||
255 | canonical name of the remote host must be present in the comma- | ||
256 | separated list of patterns (`*' and `'? serve as wildcards). | ||
257 | The list may also contain patterns negated by prefixing them with | ||
258 | `'!; if the canonical host name matches a negated pattern, the | ||
259 | key is not accepted. The purpose of this option is to optionally | ||
260 | increase security: public key authentication by itself does not | ||
261 | trust the network or name servers or anything (but the key); howM-- | ||
262 | ever, if somebody somehow steals the key, the key permits an | ||
263 | intruder to log in from anywhere in the world. This additional | ||
264 | option makes using a stolen key more difficult (name servers | ||
265 | and/or routers would have to be compromised in addition to just | ||
266 | the key). | ||
267 | |||
268 | command="command" | ||
269 | Specifies that the command is executed whenever this key is used | ||
270 | for authentication. The command supplied by the user (if any) is | ||
271 | ignored. The command is run on a pty if the client requests a | ||
272 | pty; otherwise it is run without a tty. If a 8-bit clean channel | ||
273 | is required, one must not request a pty or should specify no-pty. | ||
274 | A quote may be included in the command by quoting it with a backM-- | ||
275 | slash. This option might be useful to restrict certain public | ||
276 | keys to perform just a specific operation. An example might be a | ||
277 | key that permits remote backups but nothing else. Note that the | ||
278 | client may specify TCP/IP and/or X11 forwarding unless they are | ||
279 | explicitly prohibited. Note that this option applies to shell, | ||
280 | command or subsystem execution. | ||
281 | |||
282 | environment="NAME=value" | ||
283 | Specifies that the string is to be added to the environment when | ||
284 | logging in using this key. Environment variables set this way | ||
285 | override other default environment values. Multiple options of | ||
286 | this type are permitted. Environment processing is disabled by | ||
287 | default and is controlled via the PermitUserEnvironment option. | ||
288 | This option is automatically disabled if UseLogin is enabled. | ||
289 | |||
290 | no-port-forwarding | ||
291 | Forbids TCP/IP forwarding when this key is used for authenticaM-- | ||
292 | tion. Any port forward requests by the client will return an | ||
293 | error. This might be used, e.g., in connection with the command | ||
294 | option. | ||
295 | |||
296 | no-X11-forwarding | ||
297 | Forbids X11 forwarding when this key is used for authentication. | ||
298 | Any X11 forward requests by the client will return an error. | ||
299 | |||
300 | no-agent-forwarding | ||
301 | Forbids authentication agent forwarding when this key is used for | ||
302 | authentication. | ||
303 | |||
304 | no-pty Prevents tty allocation (a request to allocate a pty will fail). | ||
305 | |||
306 | permitopen="host:port" | ||
307 | Limit local ``ssh -L'' port forwarding such that it may only conM-- | ||
308 | nect to the specified host and port. IPv6 addresses can be specM-- | ||
309 | ified with an alternative syntax: host/port. Multiple permitopen | ||
310 | options may be applied separated by commas. No pattern matching | ||
311 | is performed on the specified hostnames, they must be literal | ||
312 | domains or addresses. | ||
313 | |||
314 | Examples | ||
315 | 1024 33 12121...312314325 ylo@foo.bar | ||
316 | |||
317 | from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23...2334 ylo@niksula | ||
318 | |||
319 | command="dump /home",no-pty,no-port-forwarding 1024 33 23...2323 | ||
320 | backup.hut.fi | ||
321 | |||
322 | permitopen="10.2.1.55:80",permitopen="10.2.1.56:25" 1024 33 23...2323 | ||
323 | |||
324 | SSH_KNOWN_HOSTS FILE FORMAT | ||
325 | The /etc/ssh/ssh_known_hosts, and $HOME/.ssh/known_hosts files contain | ||
326 | host public keys for all known hosts. The global file should be prepared | ||
327 | by the administrator (optional), and the per-user file is maintained | ||
328 | automatically: whenever the user connects from an unknown host its key is | ||
329 | added to the per-user file. | ||
330 | |||
331 | Each line in these files contains the following fields: hostnames, bits, | ||
332 | exponent, modulus, comment. The fields are separated by spaces. | ||
333 | |||
334 | Hostnames is a comma-separated list of patterns ('*' and '?' act as wildM-- | ||
335 | cards); each pattern in turn is matched against the canonical host name | ||
336 | (when authenticating a client) or against the user-supplied name (when | ||
337 | authenticating a server). A pattern may also be preceded by `'! to | ||
338 | indicate negation: if the host name matches a negated pattern, it is not | ||
339 | accepted (by that line) even if it matched another pattern on the line. | ||
340 | |||
341 | Bits, exponent, and modulus are taken directly from the RSA host key; | ||
342 | they can be obtained, e.g., from /etc/ssh/ssh_host_key.pub. The optional | ||
343 | comment field continues to the end of the line, and is not used. | ||
344 | |||
345 | Lines starting with `#' and empty lines are ignored as comments. | ||
346 | |||
347 | When performing host authentication, authentication is accepted if any | ||
348 | matching line has the proper key. It is thus permissible (but not recomM-- | ||
349 | mended) to have several lines or different host keys for the same names. | ||
350 | This will inevitably happen when short forms of host names from different | ||
351 | domains are put in the file. It is possible that the files contain conM-- | ||
352 | flicting information; authentication is accepted if valid information can | ||
353 | be found from either file. | ||
354 | |||
355 | Note that the lines in these files are typically hundreds of characters | ||
356 | long, and you definitely don't want to type in the host keys by hand. | ||
357 | Rather, generate them by a script or by taking /etc/ssh/ssh_host_key.pub | ||
358 | and adding the host names at the front. | ||
359 | |||
360 | Examples | ||
361 | |||
362 | closenet,...,130.233.208.41 1024 37 159...93 closenet.hut.fi | ||
363 | cvs.openbsd.org,199.185.137.3 ssh-rsa AAAA1234.....= | ||
364 | |||
365 | FILES | ||
366 | /etc/ssh/sshd_config | ||
367 | Contains configuration data for sshd. The file format and conM-- | ||
368 | figuration options are described in sshd_config(5). | ||
369 | |||
370 | /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key, | ||
371 | /etc/ssh/ssh_host_rsa_key | ||
372 | These three files contain the private parts of the host keys. | ||
373 | These files should only be owned by root, readable only by root, | ||
374 | and not accessible to others. Note that sshd does not start if | ||
375 | this file is group/world-accessible. | ||
376 | |||
377 | /etc/ssh/ssh_host_key.pub, /etc/ssh/ssh_host_dsa_key.pub, | ||
378 | /etc/ssh/ssh_host_rsa_key.pub | ||
379 | These three files contain the public parts of the host keys. | ||
380 | These files should be world-readable but writable only by root. | ||
381 | Their contents should match the respective private parts. These | ||
382 | files are not really used for anything; they are provided for the | ||
383 | convenience of the user so their contents can be copied to known | ||
384 | hosts files. These files are created using ssh-keygen(1). | ||
385 | |||
386 | /etc/moduli | ||
387 | Contains Diffie-Hellman groups used for the "Diffie-Hellman Group | ||
388 | Exchange". The file format is described in moduli(5). | ||
389 | |||
390 | /var/empty | ||
391 | chroot(2) directory used by sshd during privilege separation in | ||
392 | the pre-authentication phase. The directory should not contain | ||
393 | any files and must be owned by root and not group or world- | ||
394 | writable. | ||
395 | |||
396 | /var/run/sshd.pid | ||
397 | Contains the process ID of the sshd listening for connections (if | ||
398 | there are several daemons running concurrently for different | ||
399 | ports, this contains the process ID of the one started last). | ||
400 | The content of this file is not sensitive; it can be world-readM-- | ||
401 | able. | ||
402 | |||
403 | $HOME/.ssh/authorized_keys | ||
404 | Lists the public keys (RSA or DSA) that can be used to log into | ||
405 | the user's account. This file must be readable by root (which | ||
406 | may on some machines imply it being world-readable if the user's | ||
407 | home directory resides on an NFS volume). It is recommended that | ||
408 | it not be accessible by others. The format of this file is | ||
409 | described above. Users will place the contents of their | ||
410 | identity.pub, id_dsa.pub and/or id_rsa.pub files into this file, | ||
411 | as described in ssh-keygen(1). | ||
412 | |||
413 | /etc/ssh/ssh_known_hosts and $HOME/.ssh/known_hosts | ||
414 | These files are consulted when using rhosts with RSA host authenM-- | ||
415 | tication or protocol version 2 hostbased authentication to check | ||
416 | the public key of the host. The key must be listed in one of | ||
417 | these files to be accepted. The client uses the same files to | ||
418 | verify that it is connecting to the correct remote host. These | ||
419 | files should be writable only by root/the owner. | ||
420 | /etc/ssh/ssh_known_hosts should be world-readable, and | ||
421 | $HOME/.ssh/known_hosts can but need not be world-readable. | ||
422 | |||
423 | /etc/nologin | ||
424 | If this file exists, sshd refuses to let anyone except root log | ||
425 | in. The contents of the file are displayed to anyone trying to | ||
426 | log in, and non-root connections are refused. The file should be | ||
427 | world-readable. | ||
428 | |||
429 | /etc/hosts.allow, /etc/hosts.deny | ||
430 | Access controls that should be enforced by tcp-wrappers are | ||
431 | defined here. Further details are described in hosts_access(5). | ||
432 | |||
433 | $HOME/.rhosts | ||
434 | This file contains host-username pairs, separated by a space, one | ||
435 | per line. The given user on the corresponding host is permitted | ||
436 | to log in without password. The same file is used by rlogind and | ||
437 | rshd. The file must be writable only by the user; it is recomM-- | ||
438 | mended that it not be accessible by others. | ||
439 | |||
440 | If is also possible to use netgroups in the file. Either host or | ||
441 | user name may be of the form +@groupname to specify all hosts or | ||
442 | all users in the group. | ||
443 | |||
444 | $HOME/.shosts | ||
445 | For ssh, this file is exactly the same as for .rhosts. However, | ||
446 | this file is not used by rlogin and rshd, so using this permits | ||
447 | access using SSH only. | ||
448 | |||
449 | /etc/hosts.equiv | ||
450 | This file is used during .rhosts authentication. In the simplest | ||
451 | form, this file contains host names, one per line. Users on | ||
452 | those hosts are permitted to log in without a password, provided | ||
453 | they have the same user name on both machines. The host name may | ||
454 | also be followed by a user name; such users are permitted to log | ||
455 | in as any user on this machine (except root). Additionally, the | ||
456 | syntax ``+@group'' can be used to specify netgroups. Negated | ||
457 | entries start with `-'. | ||
458 | |||
459 | If the client host/user is successfully matched in this file, | ||
460 | login is automatically permitted provided the client and server | ||
461 | user names are the same. Additionally, successful RSA host | ||
462 | authentication is normally required. This file must be writable | ||
463 | only by root; it is recommended that it be world-readable. | ||
464 | |||
465 | Warning: It is almost never a good idea to use user names in | ||
466 | hosts.equiv. Beware that it really means that the named user(s) | ||
467 | can log in as anybody, which includes bin, daemon, adm, and other | ||
468 | accounts that own critical binaries and directories. Using a | ||
469 | user name practically grants the user root access. The only | ||
470 | valid use for user names that I can think of is in negative | ||
471 | entries. | ||
472 | |||
473 | Note that this warning also applies to rsh/rlogin. | ||
474 | |||
475 | /etc/shosts.equiv | ||
476 | This is processed exactly as /etc/hosts.equiv. However, this | ||
477 | file may be useful in environments that want to run both | ||
478 | rsh/rlogin and ssh. | ||
479 | |||
480 | $HOME/.ssh/environment | ||
481 | This file is read into the environment at login (if it exists). | ||
482 | It can only contain empty lines, comment lines (that start with | ||
483 | `#'), and assignment lines of the form name=value. The file | ||
484 | should be writable only by the user; it need not be readable by | ||
485 | anyone else. Environment processing is disabled by default and | ||
486 | is controlled via the PermitUserEnvironment option. | ||
487 | |||
488 | $HOME/.ssh/rc | ||
489 | If this file exists, it is run with /bin/sh after reading the | ||
490 | environment files but before starting the user's shell or comM-- | ||
491 | mand. It must not produce any output on stdout; stderr must be | ||
492 | used instead. If X11 forwarding is in use, it will receive the | ||
493 | "proto cookie" pair in its standard input (and DISPLAY in its | ||
494 | environment). The script must call xauth(1) because sshd will | ||
495 | not run xauth automatically to add X11 cookies. | ||
496 | |||
497 | The primary purpose of this file is to run any initialization | ||
498 | routines which may be needed before the user's home directory | ||
499 | becomes accessible; AFS is a particular example of such an enviM-- | ||
500 | ronment. | ||
501 | |||
502 | This file will probably contain some initialization code followed | ||
503 | by something similar to: | ||
504 | |||
505 | if read proto cookie && [ -n "$DISPLAY" ]; then | ||
506 | if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then | ||
507 | # X11UseLocalhost=yes | ||
508 | echo add unix:`echo $DISPLAY | | ||
509 | cut -c11-` $proto $cookie | ||
510 | else | ||
511 | # X11UseLocalhost=no | ||
512 | echo add $DISPLAY $proto $cookie | ||
513 | fi | xauth -q - | ||
514 | fi | ||
515 | |||
516 | If this file does not exist, /etc/ssh/sshrc is run, and if that | ||
517 | does not exist either, xauth is used to add the cookie. | ||
518 | |||
519 | This file should be writable only by the user, and need not be | ||
520 | readable by anyone else. | ||
521 | |||
522 | /etc/ssh/sshrc | ||
523 | Like $HOME/.ssh/rc. This can be used to specify machine-specific | ||
524 | login-time initializations globally. This file should be | ||
525 | writable only by root, and should be world-readable. | ||
526 | |||
527 | AUTHORS | ||
528 | OpenSSH is a derivative of the original and free ssh 1.2.12 release by | ||
529 | Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo | ||
530 | de Raadt and Dug Song removed many bugs, re-added newer features and creM-- | ||
531 | ated OpenSSH. Markus Friedl contributed the support for SSH protocol | ||
532 | versions 1.5 and 2.0. Niels Provos and Markus Friedl contributed support | ||
533 | for privilege separation. | ||
534 | |||
535 | SEE ALSO | ||
536 | scp(1), sftp(1), ssh(1), ssh-add(1), ssh-agent(1), ssh-keygen(1), | ||
537 | login.conf(5), moduli(5), sshd_config(5), sftp-server(8) | ||
538 | |||
539 | T. Ylonen, T. Kivinen, M. Saarinen, T. Rinne, and S. Lehtinen, SSH | ||
540 | Protocol Architecture, draft-ietf-secsh-architecture-12.txt, January | ||
541 | 2002, work in progress material. | ||
542 | |||
543 | M. Friedl, N. Provos, and W. A. Simpson, Diffie-Hellman Group Exchange | ||
544 | for the SSH Transport Layer Protocol, draft-ietf-secsh-dh-group- | ||
545 | exchange-02.txt, January 2002, work in progress material. | ||
546 | |||
547 | BSD September 25, 1999 BSD | ||