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authorColin Watson <cjwatson@debian.org>2003-09-17 00:32:19 +0000
committerColin Watson <cjwatson@debian.org>2003-09-17 00:32:19 +0000
commit22f9b945efa61bba12a4778b889df07cf851838a (patch)
tree77a3f749ea589c590db930cff12d804a4d7893b5 /sshd.0
parent9d1471514608023cda6456f5a2e875cc5e4b9e77 (diff)
parent854156dd39acbde9b4a47ec0fc54a042ea7358e0 (diff)
Import OpenSSH 3.7p1.
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1SSHD(8) BSD System ManagerM-bM-^@M-^Ys Manual SSHD(8)
2
3NAME
4 sshd - OpenSSH SSH daemon
5
6SYNOPSIS
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
10DESCRIPTION
11 sshd (SSH Daemon) is the daemon program for ssh(1). Together these pro-
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 nor-
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 implementa-
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 Each host has a host-specific RSA key (normally 1024 bits) used to iden-
25 tify the host. Additionally, when the daemon starts, it generates a
26 server RSA key (normally 768 bits). This key is normally regenerated
27 every hour if it has been used, and is never stored on disk.
28
29 Whenever a client connects, the daemon responds with its public host and
30 server keys. The client compares the RSA host key against its own
31 database to verify that it has not changed. The client then generates a
32 256 bit random number. It encrypts this random number using both the
33 host key and the server key, and sends the encrypted number to the
34 server. Both sides then use this random number as a session key which is
35 used to encrypt all further communications in the session. The rest of
36 the session is encrypted using a conventional cipher, currently Blowfish
37 or 3DES, with 3DES being used by default. The client selects the encryp-
38 tion algorithm to use from those offered by the server.
39
40 Next, the server and the client enter an authentication dialog. The
41 client tries to authenticate itself using .rhosts authentication, .rhosts
42 authentication combined with RSA host authentication, RSA challenge-
43 response authentication, or password based authentication.
44
45 Regardless of the authentication type, the account is checked to ensure
46 that it is accessible. An account is not accessible if it is locked,
47 listed in DenyUsers or its group is listed in DenyGroups . The defini-
48 tion of a locked account is system dependant. Some platforms have their
49 own account database (eg AIX) and some modify the passwd field ( M-bM-^@M-^X*LK*M-bM-^@M-^Y
50 on Solaris, M-bM-^@M-^X*M-bM-^@M-^Y on HP-UX, containing M-bM-^@M-^XNologinM-bM-^@M-^Y on Tru64 and a leading
51 M-bM-^@M-^X!!M-bM-^@M-^Y on Linux). If there is a requirement to disable password authenti-
52 cation for the account while allowing still public-key, then the passwd
53 field should be set to something other than these values (eg M-bM-^@M-^XNPM-bM-^@M-^Y or
54 M-bM-^@M-^X*NP*M-bM-^@M-^Y ).
55
56 Rhosts authentication is normally disabled because it is fundamentally
57 insecure, but can be enabled in the server configuration file if desired.
58 System security is not improved unless rshd, rlogind, and rexecd are dis-
59 abled (thus completely disabling rlogin and rsh into the machine).
60
61 SSH protocol version 2
62 Version 2 works similarly: Each host has a host-specific key (RSA or DSA)
63 used to identify the host. However, when the daemon starts, it does not
64 generate a server key. Forward security is provided through a Diffie-
65 Hellman key agreement. This key agreement results in a shared session
66 key.
67
68 The rest of the session is encrypted using a symmetric cipher, currently
69 128 bit AES, Blowfish, 3DES, CAST128, Arcfour, 192 bit AES, or 256 bit
70 AES. The client selects the encryption algorithm to use from those
71 offered by the server. Additionally, session integrity is provided
72 through a cryptographic message authentication code (hmac-sha1 or hmac-
73 md5).
74
75 Protocol version 2 provides a public key based user (PubkeyAuthentica-
76 tion) or client host (HostbasedAuthentication) authentication method,
77 conventional password authentication and challenge response based meth-
78 ods.
79
80 Command execution and data forwarding
81 If the client successfully authenticates itself, a dialog for preparing
82 the session is entered. At this time the client may request things like
83 allocating a pseudo-tty, forwarding X11 connections, forwarding TCP/IP
84 connections, or forwarding the authentication agent connection over the
85 secure channel.
86
87 Finally, the client either requests a shell or execution of a command.
88 The sides then enter session mode. In this mode, either side may send
89 data at any time, and such data is forwarded to/from the shell or command
90 on the server side, and the user terminal in the client side.
91
92 When the user program terminates and all forwarded X11 and other connec-
93 tions have been closed, the server sends command exit status to the
94 client, and both sides exit.
95
96 sshd can be configured using command-line options or a configuration
97 file. Command-line options override values specified in the configura-
98 tion file.
99
100 sshd rereads its configuration file when it receives a hangup signal,
101 SIGHUP, by executing itself with the name it was started as, i.e.,
102 /usr/sbin/sshd.
103
104 The options are as follows:
105
106 -b bits
107 Specifies the number of bits in the ephemeral protocol version 1
108 server key (default 768).
109
110 -d Debug mode. The server sends verbose debug output to the system
111 log, and does not put itself in the background. The server also
112 will not fork and will only process one connection. This option
113 is only intended for debugging for the server. Multiple -d
114 options increase the debugging level. Maximum is 3.
115
116 -e When this option is specified, sshd will send the output to the
117 standard error instead of the system log.
118
119 -f configuration_file
120 Specifies the name of the configuration file. The default is
121 /etc/ssh/sshd_config. sshd refuses to start if there is no con-
122 figuration file.
123
124 -g login_grace_time
125 Gives the grace time for clients to authenticate themselves
126 (default 120 seconds). If the client fails to authenticate the
127 user within this many seconds, the server disconnects and exits.
128 A value of zero indicates no limit.
129
130 -h host_key_file
131 Specifies a file from which a host key is read. This option must
132 be given if sshd is not run as root (as the normal host key files
133 are normally not readable by anyone but root). The default is
134 /etc/ssh/ssh_host_key for protocol version 1, and
135 /etc/ssh/ssh_host_rsa_key and /etc/ssh/ssh_host_dsa_key for pro-
136 tocol version 2. It is possible to have multiple host key files
137 for the different protocol versions and host key algorithms.
138
139 -i Specifies that sshd is being run from inetd(8). sshd is normally
140 not run from inetd because it needs to generate the server key
141 before it can respond to the client, and this may take tens of
142 seconds. Clients would have to wait too long if the key was
143 regenerated every time. However, with small key sizes (e.g.,
144 512) using sshd from inetd may be feasible.
145
146 -k key_gen_time
147 Specifies how often the ephemeral protocol version 1 server key
148 is regenerated (default 3600 seconds, or one hour). The motiva-
149 tion for regenerating the key fairly often is that the key is not
150 stored anywhere, and after about an hour, it becomes impossible
151 to recover the key for decrypting intercepted communications even
152 if the machine is cracked into or physically seized. A value of
153 zero indicates that the key will never be regenerated.
154
155 -o option
156 Can be used to give options in the format used in the configura-
157 tion file. This is useful for specifying options for which there
158 is no separate command-line flag.
159
160 -p port
161 Specifies the port on which the server listens for connections
162 (default 22). Multiple port options are permitted. Ports speci-
163 fied in the configuration file are ignored when a command-line
164 port is specified.
165
166 -q Quiet mode. Nothing is sent to the system log. Normally the
167 beginning, authentication, and termination of each connection is
168 logged.
169
170 -t Test mode. Only check the validity of the configuration file and
171 sanity of the keys. This is useful for updating sshd reliably as
172 configuration options may change.
173
174 -u len This option is used to specify the size of the field in the utmp
175 structure that holds the remote host name. If the resolved host
176 name is longer than len, the dotted decimal value will be used
177 instead. This allows hosts with very long host names that over-
178 flow this field to still be uniquely identified. Specifying -u0
179 indicates that only dotted decimal addresses should be put into
180 the utmp file. -u0 may also be used to prevent sshd from making
181 DNS requests unless the authentication mechanism or configuration
182 requires it. Authentication mechanisms that may require DNS
183 include RhostsRSAAuthentication, HostbasedAuthentication and
184 using a from="pattern-list" option in a key file. Configuration
185 options that require DNS include using a USER@HOST pattern in
186 AllowUsers or DenyUsers.
187
188 -D When this option is specified sshd will not detach and does not
189 become a daemon. This allows easy monitoring of sshd.
190
191 -4 Forces sshd to use IPv4 addresses only.
192
193 -6 Forces sshd to use IPv6 addresses only.
194
195CONFIGURATION FILE
196 sshd reads configuration data from /etc/ssh/sshd_config (or the file
197 specified with -f on the command line). The file format and configura-
198 tion options are described in sshd_config(5).
199
200LOGIN PROCESS
201 When a user successfully logs in, sshd does the following:
202
203 1. If the login is on a tty, and no command has been specified,
204 prints last login time and /etc/motd (unless prevented in the
205 configuration file or by $HOME/.hushlogin; see the FILES sec-
206 tion).
207
208 2. If the login is on a tty, records login time.
209
210 3. Checks /etc/nologin; if it exists, prints contents and quits
211 (unless root).
212
213 4. Changes to run with normal user privileges.
214
215 5. Sets up basic environment.
216
217 6. Reads $HOME/.ssh/environment if it exists and users are
218 allowed to change their environment. See the
219 PermitUserEnvironment option in sshd_config(5).
220
221 7. Changes to userM-bM-^@M-^Ys home directory.
222
223 8. If $HOME/.ssh/rc exists, runs it; else if /etc/ssh/sshrc
224 exists, runs it; otherwise runs xauth. The M-bM-^@M-^\rcM-bM-^@M-^] files are
225 given the X11 authentication protocol and cookie in standard
226 input.
227
228 9. Runs userM-bM-^@M-^Ys shell or command.
229
230AUTHORIZED_KEYS FILE FORMAT
231 $HOME/.ssh/authorized_keys is the default file that lists the public keys
232 that are permitted for RSA authentication in protocol version 1 and for
233 public key authentication (PubkeyAuthentication) in protocol version 2.
234 AuthorizedKeysFile may be used to specify an alternative file.
235
236 Each line of the file contains one key (empty lines and lines starting
237 with a M-bM-^@M-^X#M-bM-^@M-^Y are ignored as comments). Each RSA public key consists of the
238 following fields, separated by spaces: options, bits, exponent, modulus,
239 comment. Each protocol version 2 public key consists of: options, key-
240 type, base64 encoded key, comment. The options field is optional; its
241 presence is determined by whether the line starts with a number or not
242 (the options field never starts with a number). The bits, exponent, mod-
243 ulus and comment fields give the RSA key for protocol version 1; the com-
244 ment field is not used for anything (but may be convenient for the user
245 to identify the key). For protocol version 2 the keytype is M-bM-^@M-^\ssh-dssM-bM-^@M-^] or
246 M-bM-^@M-^\ssh-rsaM-bM-^@M-^].
247
248 Note that lines in this file are usually several hundred bytes long
249 (because of the size of the public key encoding). You donM-bM-^@M-^Yt want to type
250 them in; instead, copy the identity.pub, id_dsa.pub or the id_rsa.pub
251 file and edit it.
252
253 sshd enforces a minimum RSA key modulus size for protocol 1 and protocol
254 2 keys of 768 bits.
255
256 The options (if present) consist of comma-separated option specifica-
257 tions. No spaces are permitted, except within double quotes. The fol-
258 lowing option specifications are supported (note that option keywords are
259 case-insensitive):
260
261 from="pattern-list"
262 Specifies that in addition to public key authentication, the
263 canonical name of the remote host must be present in the comma-
264 separated list of patterns (M-bM-^@M-^X*M-bM-^@M-^Y and M-bM-^@M-^X?M-bM-^@M-^Y serve as wildcards). The
265 list may also contain patterns negated by prefixing them with
266 M-bM-^@M-^X!M-bM-^@M-^Y; if the canonical host name matches a negated pattern, the
267 key is not accepted. The purpose of this option is to optionally
268 increase security: public key authentication by itself does not
269 trust the network or name servers or anything (but the key); how-
270 ever, if somebody somehow steals the key, the key permits an
271 intruder to log in from anywhere in the world. This additional
272 option makes using a stolen key more difficult (name servers
273 and/or routers would have to be compromised in addition to just
274 the key).
275
276 command="command"
277 Specifies that the command is executed whenever this key is used
278 for authentication. The command supplied by the user (if any) is
279 ignored. The command is run on a pty if the client requests a
280 pty; otherwise it is run without a tty. If an 8-bit clean chan-
281 nel is required, one must not request a pty or should specify
282 no-pty. A quote may be included in the command by quoting it
283 with a backslash. This option might be useful to restrict cer-
284 tain public keys to perform just a specific operation. An exam-
285 ple might be a key that permits remote backups but nothing else.
286 Note that the client may specify TCP/IP and/or X11 forwarding
287 unless they are explicitly prohibited. Note that this option
288 applies to shell, command or subsystem execution.
289
290 environment="NAME=value"
291 Specifies that the string is to be added to the environment when
292 logging in using this key. Environment variables set this way
293 override other default environment values. Multiple options of
294 this type are permitted. Environment processing is disabled by
295 default and is controlled via the PermitUserEnvironment option.
296 This option is automatically disabled if UseLogin is enabled.
297
298 no-port-forwarding
299 Forbids TCP/IP forwarding when this key is used for authentica-
300 tion. Any port forward requests by the client will return an
301 error. This might be used, e.g., in connection with the command
302 option.
303
304 no-X11-forwarding
305 Forbids X11 forwarding when this key is used for authentication.
306 Any X11 forward requests by the client will return an error.
307
308 no-agent-forwarding
309 Forbids authentication agent forwarding when this key is used for
310 authentication.
311
312 no-pty Prevents tty allocation (a request to allocate a pty will fail).
313
314 permitopen="host:port"
315 Limit local M-bM-^@M-^XM-bM-^@M-^Xssh -LM-bM-^@M-^YM-bM-^@M-^Y port forwarding such that it may only con-
316 nect to the specified host and port. IPv6 addresses can be spec-
317 ified with an alternative syntax: host/port. Multiple permitopen
318 options may be applied separated by commas. No pattern matching
319 is performed on the specified hostnames, they must be literal
320 domains or addresses.
321
322 Examples
323 1024 33 12121...312314325 ylo@foo.bar
324
325 from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23...2334 ylo@niksula
326
327 command="dump /home",no-pty,no-port-forwarding 1024 33 23...2323
328 backup.hut.fi
329
330 permitopen="10.2.1.55:80",permitopen="10.2.1.56:25" 1024 33 23...2323
331
332SSH_KNOWN_HOSTS FILE FORMAT
333 The /etc/ssh/ssh_known_hosts and $HOME/.ssh/known_hosts files contain
334 host public keys for all known hosts. The global file should be prepared
335 by the administrator (optional), and the per-user file is maintained
336 automatically: whenever the user connects from an unknown host its key is
337 added to the per-user file.
338
339 Each line in these files contains the following fields: hostnames, bits,
340 exponent, modulus, comment. The fields are separated by spaces.
341
342 Hostnames is a comma-separated list of patterns (M-bM-^@M-^X*M-bM-^@M-^Y and M-bM-^@M-^X?M-bM-^@M-^Y act as wild-
343 cards); each pattern in turn is matched against the canonical host name
344 (when authenticating a client) or against the user-supplied name (when
345 authenticating a server). A pattern may also be preceded by M-bM-^@M-^X!M-bM-^@M-^Y to indi-
346 cate negation: if the host name matches a negated pattern, it is not
347 accepted (by that line) even if it matched another pattern on the line.
348
349 Bits, exponent, and modulus are taken directly from the RSA host key;
350 they can be obtained, e.g., from /etc/ssh/ssh_host_key.pub. The optional
351 comment field continues to the end of the line, and is not used.
352
353 Lines starting with M-bM-^@M-^X#M-bM-^@M-^Y and empty lines are ignored as comments.
354
355 When performing host authentication, authentication is accepted if any
356 matching line has the proper key. It is thus permissible (but not recom-
357 mended) to have several lines or different host keys for the same names.
358 This will inevitably happen when short forms of host names from different
359 domains are put in the file. It is possible that the files contain con-
360 flicting information; authentication is accepted if valid information can
361 be found from either file.
362
363 Note that the lines in these files are typically hundreds of characters
364 long, and you definitely donM-bM-^@M-^Yt want to type in the host keys by hand.
365 Rather, generate them by a script or by taking /etc/ssh/ssh_host_key.pub
366 and adding the host names at the front.
367
368 Examples
369 closenet,...,130.233.208.41 1024 37 159...93 closenet.hut.fi
370 cvs.openbsd.org,199.185.137.3 ssh-rsa AAAA1234.....=
371
372FILES
373 /etc/ssh/sshd_config
374 Contains configuration data for sshd. The file format and con-
375 figuration options are described in sshd_config(5).
376
377 /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key,
378 /etc/ssh/ssh_host_rsa_key
379 These three files contain the private parts of the host keys.
380 These files should only be owned by root, readable only by root,
381 and not accessible to others. Note that sshd does not start if
382 this file is group/world-accessible.
383
384 /etc/ssh/ssh_host_key.pub, /etc/ssh/ssh_host_dsa_key.pub,
385 /etc/ssh/ssh_host_rsa_key.pub
386 These three files contain the public parts of the host keys.
387 These files should be world-readable but writable only by root.
388 Their contents should match the respective private parts. These
389 files are not really used for anything; they are provided for the
390 convenience of the user so their contents can be copied to known
391 hosts files. These files are created using ssh-keygen(1).
392
393 /etc/moduli
394 Contains Diffie-Hellman groups used for the "Diffie-Hellman Group
395 Exchange". The file format is described in moduli(5).
396
397 /var/empty
398 chroot(2) directory used by sshd during privilege separation in
399 the pre-authentication phase. The directory should not contain
400 any files and must be owned by root and not group or world-
401 writable.
402
403 /var/run/sshd.pid
404 Contains the process ID of the sshd listening for connections (if
405 there are several daemons running concurrently for different
406 ports, this contains the process ID of the one started last).
407 The content of this file is not sensitive; it can be world-read-
408 able.
409
410 $HOME/.ssh/authorized_keys
411 Lists the public keys (RSA or DSA) that can be used to log into
412 the userM-bM-^@M-^Ys account. This file must be readable by root (which
413 may on some machines imply it being world-readable if the userM-bM-^@M-^Ys
414 home directory resides on an NFS volume). It is recommended that
415 it not be accessible by others. The format of this file is
416 described above. Users will place the contents of their
417 identity.pub, id_dsa.pub and/or id_rsa.pub files into this file,
418 as described in ssh-keygen(1).
419
420 /etc/ssh/ssh_known_hosts and $HOME/.ssh/known_hosts
421 These files are consulted when using rhosts with RSA host authen-
422 tication or protocol version 2 hostbased authentication to check
423 the public key of the host. The key must be listed in one of
424 these files to be accepted. The client uses the same files to
425 verify that it is connecting to the correct remote host. These
426 files should be writable only by root/the owner.
427 /etc/ssh/ssh_known_hosts should be world-readable, and
428 $HOME/.ssh/known_hosts can, but need not be, world-readable.
429
430 /etc/nologin
431 If this file exists, sshd refuses to let anyone except root log
432 in. The contents of the file are displayed to anyone trying to
433 log in, and non-root connections are refused. The file should be
434 world-readable.
435
436 /etc/hosts.allow, /etc/hosts.deny
437 Access controls that should be enforced by tcp-wrappers are
438 defined here. Further details are described in hosts_access(5).
439
440 $HOME/.rhosts
441 This file contains host-username pairs, separated by a space, one
442 per line. The given user on the corresponding host is permitted
443 to log in without a password. The same file is used by rlogind
444 and rshd. The file must be writable only by the user; it is rec-
445 ommended that it not be accessible by others.
446
447 If is also possible to use netgroups in the file. Either host or
448 user name may be of the form +@groupname to specify all hosts or
449 all users in the group.
450
451 $HOME/.shosts
452 For ssh, this file is exactly the same as for .rhosts. However,
453 this file is not used by rlogin and rshd, so using this permits
454 access using SSH only.
455
456 /etc/hosts.equiv
457 This file is used during .rhosts authentication. In the simplest
458 form, this file contains host names, one per line. Users on
459 those hosts are permitted to log in without a password, provided
460 they have the same user name on both machines. The host name may
461 also be followed by a user name; such users are permitted to log
462 in as any user on this machine (except root). Additionally, the
463 syntax M-bM-^@M-^\+@groupM-bM-^@M-^] can be used to specify netgroups. Negated
464 entries start with M-bM-^@M-^X-M-bM-^@M-^Y.
465
466 If the client host/user is successfully matched in this file,
467 login is automatically permitted provided the client and server
468 user names are the same. Additionally, successful RSA host
469 authentication is normally required. This file must be writable
470 only by root; it is recommended that it be world-readable.
471
472 Warning: It is almost never a good idea to use user names in
473 hosts.equiv. Beware that it really means that the named user(s)
474 can log in as anybody, which includes bin, daemon, adm, and other
475 accounts that own critical binaries and directories. Using a
476 user name practically grants the user root access. The only
477 valid use for user names that I can think of is in negative
478 entries.
479
480 Note that this warning also applies to rsh/rlogin.
481
482 /etc/shosts.equiv
483 This is processed exactly as /etc/hosts.equiv. However, this
484 file may be useful in environments that want to run both
485 rsh/rlogin and ssh.
486
487 $HOME/.ssh/environment
488 This file is read into the environment at login (if it exists).
489 It can only contain empty lines, comment lines (that start with
490 M-bM-^@M-^X#M-bM-^@M-^Y), and assignment lines of the form name=value. The file
491 should be writable only by the user; it need not be readable by
492 anyone else. Environment processing is disabled by default and
493 is controlled via the PermitUserEnvironment option.
494
495 $HOME/.ssh/rc
496 If this file exists, it is run with /bin/sh after reading the
497 environment files but before starting the userM-bM-^@M-^Ys shell or com-
498 mand. It must not produce any output on stdout; stderr must be
499 used instead. If X11 forwarding is in use, it will receive the
500 "proto cookie" pair in its standard input (and DISPLAY in its
501 environment). The script must call xauth(1) because sshd will
502 not run xauth automatically to add X11 cookies.
503
504 The primary purpose of this file is to run any initialization
505 routines which may be needed before the userM-bM-^@M-^Ys home directory
506 becomes accessible; AFS is a particular example of such an envi-
507 ronment.
508
509 This file will probably contain some initialization code followed
510 by something similar to:
511
512 if read proto cookie && [ -n "$DISPLAY" ]; then
513 if [ M-bM-^@M-^Xecho $DISPLAY | cut -c1-10M-bM-^@M-^X = M-bM-^@M-^Ylocalhost:M-bM-^@M-^Y ]; then
514 # X11UseLocalhost=yes
515 echo add unix:M-bM-^@M-^Xecho $DISPLAY |
516 cut -c11-M-bM-^@M-^X $proto $cookie
517 else
518 # X11UseLocalhost=no
519 echo add $DISPLAY $proto $cookie
520 fi | xauth -q -
521 fi
522
523 If this file does not exist, /etc/ssh/sshrc is run, and if that
524 does not exist either, xauth is used to add the cookie.
525
526 This file should be writable only by the user, and need not be
527 readable by anyone else.
528
529 /etc/ssh/sshrc
530 Like $HOME/.ssh/rc. This can be used to specify machine-specific
531 login-time initializations globally. This file should be
532 writable only by root, and should be world-readable.
533
534SEE ALSO
535 scp(1), sftp(1), ssh(1), ssh-add(1), ssh-agent(1), ssh-keygen(1),
536 login.conf(5), moduli(5), sshd_config(5), sftp-server(8)
537
538 T. Ylonen, T. Kivinen, M. Saarinen, T. Rinne, and S. Lehtinen, SSH
539 Protocol Architecture, draft-ietf-secsh-architecture-12.txt, January
540 2002, work in progress material.
541
542 M. Friedl, N. Provos, and W. A. Simpson, Diffie-Hellman Group Exchange
543 for the SSH Transport Layer Protocol, draft-ietf-secsh-dh-group-
544 exchange-02.txt, January 2002, work in progress material.
545
546AUTHORS
547 OpenSSH is a derivative of the original and free ssh 1.2.12 release by
548 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
549 de Raadt and Dug Song removed many bugs, re-added newer features and cre-
550 ated OpenSSH. Markus Friedl contributed the support for SSH protocol
551 versions 1.5 and 2.0. Niels Provos and Markus Friedl contributed support
552 for privilege separation.
553
554BSD September 25, 1999 BSD