Annotation of src/usr.bin/ssh/sshd.8, Revision 1.71
1.1 deraadt 1: .\" -*- nroff -*-
2: .\"
3: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: .\" All rights reserved
6: .\"
1.64 deraadt 7: .\" As far as I am concerned, the code I have written for this software
8: .\" can be used freely for any purpose. Any derived versions of this
9: .\" software must be clearly marked as such, and if the derived work is
10: .\" incompatible with the protocol description in the RFC file, it must be
11: .\" called by a name other than "ssh" or "Secure Shell".
12: .\"
13: .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
14: .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
15: .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
16: .\"
17: .\" Redistribution and use in source and binary forms, with or without
18: .\" modification, are permitted provided that the following conditions
19: .\" are met:
20: .\" 1. Redistributions of source code must retain the above copyright
21: .\" notice, this list of conditions and the following disclaimer.
22: .\" 2. Redistributions in binary form must reproduce the above copyright
23: .\" notice, this list of conditions and the following disclaimer in the
24: .\" documentation and/or other materials provided with the distribution.
1.1 deraadt 25: .\"
1.64 deraadt 26: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27: .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32: .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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34: .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.1 deraadt 36: .\"
1.71 ! aaron 37: .\" $OpenBSD: sshd.8,v 1.70 2000/10/16 09:38:44 djm Exp $
1.2 deraadt 38: .Dd September 25, 1999
39: .Dt SSHD 8
40: .Os
41: .Sh NAME
42: .Nm sshd
43: .Nd secure shell daemon
44: .Sh SYNOPSIS
45: .Nm sshd
1.29 markus 46: .Op Fl diqQ46
1.2 deraadt 47: .Op Fl b Ar bits
48: .Op Fl f Ar config_file
49: .Op Fl g Ar login_grace_time
50: .Op Fl h Ar host_key_file
51: .Op Fl k Ar key_gen_time
52: .Op Fl p Ar port
1.61 markus 53: .Op Fl u Ar len
1.26 markus 54: .Op Fl V Ar client_protocol_id
1.40 aaron 55: .Sh DESCRIPTION
1.2 deraadt 56: .Nm
1.40 aaron 57: (Secure Shell Daemon) is the daemon program for
1.2 deraadt 58: .Xr ssh 1 .
1.42 hugh 59: Together these programs replace rlogin and rsh, and
1.1 deraadt 60: provide secure encrypted communications between two untrusted hosts
1.36 aaron 61: over an insecure network.
62: The programs are intended to be as easy to
1.1 deraadt 63: install and use as possible.
1.2 deraadt 64: .Pp
65: .Nm
1.36 aaron 66: is the daemon that listens for connections from clients.
1.40 aaron 67: It is normally started at boot from
1.2 deraadt 68: .Pa /etc/rc .
69: It forks a new
1.36 aaron 70: daemon for each incoming connection.
71: The forked daemons handle
1.1 deraadt 72: key exchange, encryption, authentication, command execution,
73: and data exchange.
1.49 markus 74: This implementation of
75: .Nm
76: supports both SSH protocol version 1 and 2 simultaneously.
1.2 deraadt 77: .Nm
1.36 aaron 78: works as follows.
1.49 markus 79: .Pp
80: .Ss SSH protocol version 1
81: .Pp
1.36 aaron 82: Each host has a host-specific RSA key
83: (normally 1024 bits) used to identify the host.
84: Additionally, when
1.1 deraadt 85: the daemon starts, it generates a server RSA key (normally 768 bits).
86: This key is normally regenerated every hour if it has been used, and
87: is never stored on disk.
1.2 deraadt 88: .Pp
1.42 hugh 89: Whenever a client connects the daemon responds with its public
90: host and server keys.
1.36 aaron 91: The client compares the
1.49 markus 92: RSA host key against its own database to verify that it has not changed.
1.36 aaron 93: The client then generates a 256 bit random number.
94: It encrypts this
1.1 deraadt 95: random number using both the host key and the server key, and sends
1.36 aaron 96: the encrypted number to the server.
1.42 hugh 97: Both sides then use this
1.1 deraadt 98: random number as a session key which is used to encrypt all further
1.36 aaron 99: communications in the session.
100: The rest of the session is encrypted
1.42 hugh 101: using a conventional cipher, currently Blowfish or 3DES, with 3DES
1.39 deraadt 102: being used by default.
1.36 aaron 103: The client selects the encryption algorithm
1.5 deraadt 104: to use from those offered by the server.
1.2 deraadt 105: .Pp
1.36 aaron 106: Next, the server and the client enter an authentication dialog.
107: The client tries to authenticate itself using
1.2 deraadt 108: .Pa .rhosts
109: authentication,
110: .Pa .rhosts
111: authentication combined with RSA host
1.1 deraadt 112: authentication, RSA challenge-response authentication, or password
113: based authentication.
1.2 deraadt 114: .Pp
1.1 deraadt 115: Rhosts authentication is normally disabled
116: because it is fundamentally insecure, but can be enabled in the server
1.36 aaron 117: configuration file if desired.
118: System security is not improved unless
1.2 deraadt 119: .Xr rshd 8 ,
120: .Xr rlogind 8 ,
121: .Xr rexecd 8 ,
122: and
123: .Xr rexd 8
1.1 deraadt 124: are disabled (thus completely disabling
1.2 deraadt 125: .Xr rlogin 1
1.1 deraadt 126: and
1.2 deraadt 127: .Xr rsh 1
1.42 hugh 128: into the machine).
1.2 deraadt 129: .Pp
1.49 markus 130: .Ss SSH protocol version 2
131: .Pp
1.58 deraadt 132: Version 2 works similarly:
1.49 markus 133: Each host has a host-specific DSA key used to identify the host.
134: However, when the daemon starts, it does not generate a server key.
135: Forward security is provided through a Diffie-Hellman key agreement.
136: This key agreement results in a shared session key.
137: The rest of the session is encrypted
138: using a symmetric cipher, currently
139: Blowfish, 3DES or CAST128 in CBC mode or Arcfour.
140: The client selects the encryption algorithm
141: to use from those offered by the server.
142: Additionally, session integrity is provided
1.51 hugh 143: through a cryptographic message authentication code
1.49 markus 144: (hmac-sha1 or hmac-md5).
145: .Pp
146: Protocol version 2 provides a public key based
147: user authentication method (DSAAuthentication)
148: and conventional password authentication.
149: .Pp
150: .Ss Command execution and data forwarding
151: .Pp
1.1 deraadt 152: If the client successfully authenticates itself, a dialog for
1.36 aaron 153: preparing the session is entered.
154: At this time the client may request
1.1 deraadt 155: things like allocating a pseudo-tty, forwarding X11 connections,
156: forwarding TCP/IP connections, or forwarding the authentication agent
157: connection over the secure channel.
1.2 deraadt 158: .Pp
1.1 deraadt 159: Finally, the client either requests a shell or execution of a command.
1.36 aaron 160: The sides then enter session mode.
161: In this mode, either side may send
1.1 deraadt 162: data at any time, and such data is forwarded to/from the shell or
163: command on the server side, and the user terminal in the client side.
1.2 deraadt 164: .Pp
1.1 deraadt 165: When the user program terminates and all forwarded X11 and other
166: connections have been closed, the server sends command exit status to
167: the client, and both sides exit.
1.2 deraadt 168: .Pp
169: .Nm
1.1 deraadt 170: can be configured using command-line options or a configuration
1.36 aaron 171: file.
172: Command-line options override values specified in the
1.1 deraadt 173: configuration file.
1.25 markus 174: .Pp
175: .Nm
176: rereads its configuration file when it receives a hangup signal,
177: .Dv SIGHUP .
1.18 aaron 178: .Pp
179: The options are as follows:
1.2 deraadt 180: .Bl -tag -width Ds
181: .It Fl b Ar bits
1.1 deraadt 182: Specifies the number of bits in the server key (default 768).
1.2 deraadt 183: .Pp
184: .It Fl d
1.36 aaron 185: Debug mode.
186: The server sends verbose debug output to the system
187: log, and does not put itself in the background.
188: The server also will not fork and will only process one connection.
189: This option is only intended for debugging for the server.
1.67 aaron 190: Multiple -d options increases the debugging level.
191: Maximum is 3.
1.2 deraadt 192: .It Fl f Ar configuration_file
1.36 aaron 193: Specifies the name of the configuration file.
194: The default is
1.2 deraadt 195: .Pa /etc/sshd_config .
1.16 markus 196: .Nm
197: refuses to start if there is no configuration file.
1.2 deraadt 198: .It Fl g Ar login_grace_time
1.1 deraadt 199: Gives the grace time for clients to authenticate themselves (default
1.36 aaron 200: 300 seconds).
201: If the client fails to authenticate the user within
202: this many seconds, the server disconnects and exits.
203: A value of zero indicates no limit.
1.2 deraadt 204: .It Fl h Ar host_key_file
1.49 markus 205: Specifies the file from which the RSA host key is read (default
1.2 deraadt 206: .Pa /etc/ssh_host_key ) .
1.7 markus 207: This option must be given if
208: .Nm
209: is not run as root (as the normal
1.1 deraadt 210: host file is normally not readable by anyone but root).
1.2 deraadt 211: .It Fl i
1.7 markus 212: Specifies that
213: .Nm
1.40 aaron 214: is being run from inetd.
1.7 markus 215: .Nm
216: is normally not run
1.1 deraadt 217: from inetd because it needs to generate the server key before it can
1.36 aaron 218: respond to the client, and this may take tens of seconds.
219: Clients would have to wait too long if the key was regenerated every time.
1.35 aaron 220: However, with small key sizes (e.g., 512) using
1.7 markus 221: .Nm
222: from inetd may
1.1 deraadt 223: be feasible.
1.2 deraadt 224: .It Fl k Ar key_gen_time
1.1 deraadt 225: Specifies how often the server key is regenerated (default 3600
1.36 aaron 226: seconds, or one hour).
227: The motivation for regenerating the key fairly
1.1 deraadt 228: often is that the key is not stored anywhere, and after about an hour,
229: it becomes impossible to recover the key for decrypting intercepted
230: communications even if the machine is cracked into or physically
1.36 aaron 231: seized.
232: A value of zero indicates that the key will never be regenerated.
1.2 deraadt 233: .It Fl p Ar port
1.1 deraadt 234: Specifies the port on which the server listens for connections
235: (default 22).
1.2 deraadt 236: .It Fl q
1.36 aaron 237: Quiet mode.
238: Nothing is sent to the system log.
239: Normally the beginning,
1.1 deraadt 240: authentication, and termination of each connection is logged.
1.61 markus 241: .It Fl u Ar len
242: This option is used to specify the size of the field
243: in the
244: .Li utmp
245: structure that holds the remote host name.
246: If the resolved host name is longer than
247: .Ar len ,
248: the dotted decimal value will be used instead.
249: This allows hosts with very long host names that
250: overflow this field to still be uniquely identified.
251: Specifying
252: .Fl u0
253: indicates that only dotted decimal addresses
254: should be put into the
255: .Pa utmp
256: file.
1.18 aaron 257: .It Fl Q
258: Do not print an error message if RSA support is missing.
1.26 markus 259: .It Fl V Ar client_protocol_id
1.68 markus 260: SSH-2 compatibility mode.
1.42 hugh 261: When this option is specified
1.26 markus 262: .Nm
1.42 hugh 263: assumes the client has sent the supplied version string
1.26 markus 264: and skips the
265: Protocol Version Identification Exchange.
1.68 markus 266: This option is not intended to be called directly.
1.29 markus 267: .It Fl 4
268: Forces
269: .Nm
270: to use IPv4 addresses only.
271: .It Fl 6
272: Forces
273: .Nm
274: to use IPv6 addresses only.
1.2 deraadt 275: .El
276: .Sh CONFIGURATION FILE
277: .Nm
1.40 aaron 278: reads configuration data from
1.2 deraadt 279: .Pa /etc/sshd_config
280: (or the file specified with
281: .Fl f
1.36 aaron 282: on the command line).
283: The file contains keyword-value pairs, one per line.
284: Lines starting with
1.2 deraadt 285: .Ql #
1.1 deraadt 286: and empty lines are interpreted as comments.
1.2 deraadt 287: .Pp
1.1 deraadt 288: The following keywords are possible.
1.2 deraadt 289: .Bl -tag -width Ds
290: .It Cm AFSTokenPassing
1.36 aaron 291: Specifies whether an AFS token may be forwarded to the server.
292: Default is
1.2 deraadt 293: .Dq yes .
1.11 markus 294: .It Cm AllowGroups
295: This keyword can be followed by a number of group names, separated
1.36 aaron 296: by spaces.
297: If specified, login is allowed only for users whose primary
1.11 markus 298: group matches one of the patterns.
299: .Ql \&*
300: and
301: .Ql ?
302: can be used as
1.36 aaron 303: wildcards in the patterns.
1.58 deraadt 304: Only group names are valid; a numerical group ID isn't recognized.
1.36 aaron 305: By default login is allowed regardless of the primary group.
1.3 dugsong 306: .Pp
1.69 markus 307: .It Cm AllowTcpForwarding
308: Specifies whether TCP forwarding is permitted.
309: The default is
310: .Dq yes .
311: Note that disabling TCP forwarding does not improve security unless
312: users are also denied shell access, as they can always install their
313: own forwarders.
314: .Pp
1.11 markus 315: .It Cm AllowUsers
316: This keyword can be followed by a number of user names, separated
1.36 aaron 317: by spaces.
318: If specified, login is allowed only for users names that
1.11 markus 319: match one of the patterns.
320: .Ql \&*
321: and
322: .Ql ?
323: can be used as
1.36 aaron 324: wildcards in the patterns.
1.58 deraadt 325: Only user names are valid; a numerical user ID isn't recognized.
1.36 aaron 326: By default login is allowed regardless of the user name.
1.11 markus 327: .Pp
1.41 markus 328: .It Cm Ciphers
329: Specifies the ciphers allowed for protocol version 2.
330: Multiple ciphers must be comma-separated.
331: The default is
1.50 markus 332: .Dq 3des-cbc,blowfish-cbc,arcfour,cast128-cbc .
1.8 markus 333: .It Cm CheckMail
334: Specifies whether
335: .Nm
336: should check for new mail for interactive logins.
337: The default is
338: .Dq no .
1.11 markus 339: .It Cm DenyGroups
340: This keyword can be followed by a number of group names, separated
1.36 aaron 341: by spaces.
342: Users whose primary group matches one of the patterns
1.11 markus 343: aren't allowed to log in.
344: .Ql \&*
345: and
346: .Ql ?
347: can be used as
1.36 aaron 348: wildcards in the patterns.
1.58 deraadt 349: Only group names are valid; a numerical group ID isn't recognized.
1.36 aaron 350: By default login is allowed regardless of the primary group.
1.11 markus 351: .Pp
352: .It Cm DenyUsers
353: This keyword can be followed by a number of user names, separated
1.36 aaron 354: by spaces.
355: Login is disallowed for user names that match one of the patterns.
1.11 markus 356: .Ql \&*
357: and
358: .Ql ?
1.36 aaron 359: can be used as wildcards in the patterns.
1.58 deraadt 360: Only user names are valid; a numerical user ID isn't recognized.
1.36 aaron 361: By default login is allowed regardless of the user name.
1.49 markus 362: .It Cm DSAAuthentication
363: Specifies whether DSA authentication is allowed.
364: The default is
365: .Dq yes .
366: Note that this option applies to protocol version 2 only.
1.47 markus 367: .It Cm GatewayPorts
368: Specifies whether remote hosts are allowed to connect to ports
369: forwarded for the client.
370: The argument must be
371: .Dq yes
372: or
373: .Dq no .
374: The default is
375: .Dq no .
1.58 deraadt 376: .It Cm HostDSAKey
1.46 markus 377: Specifies the file containing the private DSA host key (default
378: .Pa /etc/ssh_host_dsa_key )
379: used by SSH protocol 2.0.
380: Note that
381: .Nm
1.51 hugh 382: disables protocol 2.0 if this file is group/world-accessible.
1.2 deraadt 383: .It Cm HostKey
1.46 markus 384: Specifies the file containing the private RSA host key (default
385: .Pa /etc/ssh_host_key )
386: used by SSH protocols 1.3 and 1.5.
1.9 markus 387: Note that
388: .Nm
1.51 hugh 389: disables protocols 1.3 and 1.5 if this file is group/world-accessible.
1.2 deraadt 390: .It Cm IgnoreRhosts
1.34 markus 391: Specifies that
392: .Pa .rhosts
1.40 aaron 393: and
1.34 markus 394: .Pa .shosts
395: files will not be used in authentication.
1.2 deraadt 396: .Pa /etc/hosts.equiv
1.1 deraadt 397: and
1.40 aaron 398: .Pa /etc/shosts.equiv
1.36 aaron 399: are still used.
1.40 aaron 400: The default is
1.34 markus 401: .Dq yes .
1.24 markus 402: .It Cm IgnoreUserKnownHosts
403: Specifies whether
404: .Nm
405: should ignore the user's
406: .Pa $HOME/.ssh/known_hosts
1.45 markus 407: during
1.24 markus 408: .Cm RhostsRSAAuthentication .
409: The default is
1.2 deraadt 410: .Dq no .
411: .It Cm KeepAlive
1.1 deraadt 412: Specifies whether the system should send keepalive messages to the
1.36 aaron 413: other side.
414: If they are sent, death of the connection or crash of one
415: of the machines will be properly noticed.
416: However, this means that
1.1 deraadt 417: connections will die if the route is down temporarily, and some people
1.36 aaron 418: find it annoying.
1.51 hugh 419: On the other hand, if keepalives are not sent,
1.2 deraadt 420: sessions may hang indefinitely on the server, leaving
421: .Dq ghost
422: users and consuming server resources.
423: .Pp
424: The default is
425: .Dq yes
426: (to send keepalives), and the server will notice
1.36 aaron 427: if the network goes down or the client host reboots.
428: This avoids infinitely hanging sessions.
1.2 deraadt 429: .Pp
430: To disable keepalives, the value should be set to
431: .Dq no
432: in both the server and the client configuration files.
433: .It Cm KerberosAuthentication
1.36 aaron 434: Specifies whether Kerberos authentication is allowed.
435: This can be in the form of a Kerberos ticket, or if
1.7 markus 436: .Cm PasswordAuthentication
1.1 deraadt 437: is yes, the password provided by the user will be validated through
1.67 aaron 438: the Kerberos KDC.
439: To use this option, the server needs a
1.59 provos 440: Kerberos servtab which allows the verification of the KDC's identity.
1.36 aaron 441: Default is
1.60 provos 442: .Dq yes .
1.2 deraadt 443: .It Cm KerberosOrLocalPasswd
1.1 deraadt 444: If set then if password authentication through Kerberos fails then
445: the password will be validated via any additional local mechanism
1.2 deraadt 446: such as
1.66 markus 447: .Pa /etc/passwd .
1.36 aaron 448: Default is
1.20 dugsong 449: .Dq yes .
1.2 deraadt 450: .It Cm KerberosTgtPassing
1.1 deraadt 451: Specifies whether a Kerberos TGT may be forwarded to the server.
1.40 aaron 452: Default is
1.3 dugsong 453: .Dq no ,
454: as this only works when the Kerberos KDC is actually an AFS kaserver.
1.2 deraadt 455: .It Cm KerberosTicketCleanup
1.7 markus 456: Specifies whether to automatically destroy the user's ticket cache
1.36 aaron 457: file on logout.
458: Default is
1.3 dugsong 459: .Dq yes .
1.2 deraadt 460: .It Cm KeyRegenerationInterval
1.1 deraadt 461: The server key is automatically regenerated after this many seconds
1.36 aaron 462: (if it has been used).
463: The purpose of regeneration is to prevent
1.1 deraadt 464: decrypting captured sessions by later breaking into the machine and
1.36 aaron 465: stealing the keys.
466: The key is never stored anywhere.
467: If the value is 0, the key is never regenerated.
468: The default is 3600 (seconds).
1.7 markus 469: .It Cm ListenAddress
470: Specifies what local address
471: .Nm
472: should listen on.
473: The default is to listen to all local addresses.
1.28 markus 474: Multiple options of this type are permitted.
475: Additionally, the
476: .Cm Ports
477: options must precede this option.
1.2 deraadt 478: .It Cm LoginGraceTime
1.1 deraadt 479: The server disconnects after this time if the user has not
1.36 aaron 480: successfully logged in.
481: If the value is 0, there is no time limit.
1.1 deraadt 482: The default is 600 (seconds).
1.23 markus 483: .It Cm LogLevel
484: Gives the verbosity level that is used when logging messages from
485: .Nm sshd .
486: The possible values are:
1.27 markus 487: QUIET, FATAL, ERROR, INFO, VERBOSE and DEBUG.
1.23 markus 488: The default is INFO.
489: Logging with level DEBUG violates the privacy of users
490: and is not recommended.
1.55 markus 491: .It Cm MaxStartups
492: Specifies the maximum number of concurrent unauthenticated connections to the
493: .Nm
494: daemon.
495: Additional connections will be dropped until authentication succeeds or the
496: .Cm LoginGraceTime
497: expires for a connection.
498: The default is 10.
1.57 markus 499: .Pp
500: Alternatively, random early drop can be enabled by specifying
501: the three colon separated values
502: .Dq start:rate:full
1.67 aaron 503: (e.g., "10:30:60").
1.57 markus 504: .Nm
505: will refuse connection attempts with a probabillity of
506: .Dq rate/100
507: (30%)
508: if there are currently
509: .Dq start
510: (10)
511: unauthenticated connections.
512: The probabillity increases linearly and all connection attempts
513: are refused if the number of unauthenticated connections reaches
514: .Dq full
515: (60).
1.2 deraadt 516: .It Cm PasswordAuthentication
1.1 deraadt 517: Specifies whether password authentication is allowed.
1.2 deraadt 518: The default is
519: .Dq yes .
1.58 deraadt 520: Note that this option applies to both protocol versions 1 and 2.
1.2 deraadt 521: .It Cm PermitEmptyPasswords
1.1 deraadt 522: When password authentication is allowed, it specifies whether the
1.36 aaron 523: server allows login to accounts with empty password strings.
524: The default is
1.34 markus 525: .Dq no .
1.2 deraadt 526: .It Cm PermitRootLogin
1.1 deraadt 527: Specifies whether the root can log in using
1.2 deraadt 528: .Xr ssh 1 .
1.15 markus 529: The argument must be
530: .Dq yes ,
531: .Dq without-password
532: or
533: .Dq no .
1.2 deraadt 534: The default is
535: .Dq yes .
1.15 markus 536: If this options is set to
537: .Dq without-password
538: only password authentication is disabled for root.
1.2 deraadt 539: .Pp
540: Root login with RSA authentication when the
541: .Ar command
542: option has been
1.1 deraadt 543: specified will be allowed regardless of the value of this setting
544: (which may be useful for taking remote backups even if root login is
545: normally not allowed).
1.43 markus 546: .It Cm PidFile
547: Specifies the file that contains the process identifier of the
548: .Nm
549: daemon.
550: The default is
551: .Pa /var/run/sshd.pid .
1.2 deraadt 552: .It Cm Port
1.1 deraadt 553: Specifies the port number that
1.2 deraadt 554: .Nm
1.36 aaron 555: listens on.
556: The default is 22.
1.28 markus 557: Multiple options of this type are permitted.
1.2 deraadt 558: .It Cm PrintMotd
1.1 deraadt 559: Specifies whether
1.2 deraadt 560: .Nm
1.40 aaron 561: should print
1.2 deraadt 562: .Pa /etc/motd
1.36 aaron 563: when a user logs in interactively.
564: (On some systems it is also printed by the shell,
1.2 deraadt 565: .Pa /etc/profile ,
1.36 aaron 566: or equivalent.)
567: The default is
1.2 deraadt 568: .Dq yes .
1.41 markus 569: .It Cm Protocol
570: Specifies the protocol versions
571: .Nm
572: should support.
573: The possible values are
574: .Dq 1
575: and
576: .Dq 2 .
577: Multiple versions must be comma-separated.
578: The default is
579: .Dq 1 .
1.2 deraadt 580: .It Cm RandomSeed
1.36 aaron 581: Obsolete.
582: Random number generation uses other techniques.
1.2 deraadt 583: .It Cm RhostsAuthentication
1.1 deraadt 584: Specifies whether authentication using rhosts or /etc/hosts.equiv
1.36 aaron 585: files is sufficient.
586: Normally, this method should not be permitted because it is insecure.
1.7 markus 587: .Cm RhostsRSAAuthentication
588: should be used
1.1 deraadt 589: instead, because it performs RSA-based host authentication in addition
590: to normal rhosts or /etc/hosts.equiv authentication.
1.2 deraadt 591: The default is
592: .Dq no .
593: .It Cm RhostsRSAAuthentication
1.1 deraadt 594: Specifies whether rhosts or /etc/hosts.equiv authentication together
1.36 aaron 595: with successful RSA host authentication is allowed.
596: The default is
1.34 markus 597: .Dq no .
1.2 deraadt 598: .It Cm RSAAuthentication
1.36 aaron 599: Specifies whether pure RSA authentication is allowed.
600: The default is
1.2 deraadt 601: .Dq yes .
1.49 markus 602: Note that this option applies to protocol version 1 only.
1.2 deraadt 603: .It Cm ServerKeyBits
1.36 aaron 604: Defines the number of bits in the server key.
605: The minimum value is 512, and the default is 768.
1.7 markus 606: .It Cm SkeyAuthentication
607: Specifies whether
1.40 aaron 608: .Xr skey 1
1.36 aaron 609: authentication is allowed.
610: The default is
1.7 markus 611: .Dq yes .
612: Note that s/key authentication is enabled only if
613: .Cm PasswordAuthentication
614: is allowed, too.
1.2 deraadt 615: .It Cm StrictModes
1.12 markus 616: Specifies whether
617: .Nm
618: should check file modes and ownership of the
1.36 aaron 619: user's files and home directory before accepting login.
620: This is normally desirable because novices sometimes accidentally leave their
621: directory or files world-writable.
622: The default is
1.7 markus 623: .Dq yes .
1.54 jakob 624: .It Cm Subsystem
1.67 aaron 625: Configures an external subsystem (e.g., file transfer daemon).
626: Arguments should be a subsystem name and a command to execute upon subsystem
627: request.
1.63 markus 628: The command
629: .Xr sftp-server 8
630: implements the
631: .Dq sftp
632: file transfer subsystem.
1.54 jakob 633: By default no subsystems are defined.
634: Note that this option applies to protocol version 2 only.
1.2 deraadt 635: .It Cm SyslogFacility
1.1 deraadt 636: Gives the facility code that is used when logging messages from
1.2 deraadt 637: .Nm sshd .
1.1 deraadt 638: The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1.36 aaron 639: LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
640: The default is AUTH.
1.10 markus 641: .It Cm UseLogin
642: Specifies whether
643: .Xr login 1
1.53 markus 644: is used for interactive login sessions.
645: Note that
646: .Xr login 1
1.58 deraadt 647: is never used for remote command execution.
1.36 aaron 648: The default is
1.10 markus 649: .Dq no .
1.6 aaron 650: .It Cm X11DisplayOffset
651: Specifies the first display number available for
652: .Nm sshd Ns 's
1.36 aaron 653: X11 forwarding.
654: This prevents
1.6 aaron 655: .Nm
656: from interfering with real X11 servers.
1.34 markus 657: The default is 10.
1.30 markus 658: .It Cm X11Forwarding
1.36 aaron 659: Specifies whether X11 forwarding is permitted.
660: The default is
1.34 markus 661: .Dq no .
1.30 markus 662: Note that disabling X11 forwarding does not improve security in any
663: way, as users can always install their own forwarders.
1.52 markus 664: .It Cm XAuthLocation
665: Specifies the location of the
666: .Xr xauth 1
667: program.
668: The default is
669: .Pa /usr/X11R6/bin/xauth .
1.2 deraadt 670: .El
671: .Sh LOGIN PROCESS
1.1 deraadt 672: When a user successfully logs in,
1.2 deraadt 673: .Nm
1.1 deraadt 674: does the following:
1.2 deraadt 675: .Bl -enum -offset indent
676: .It
1.1 deraadt 677: If the login is on a tty, and no command has been specified,
1.40 aaron 678: prints last login time and
1.2 deraadt 679: .Pa /etc/motd
1.1 deraadt 680: (unless prevented in the configuration file or by
1.2 deraadt 681: .Pa $HOME/.hushlogin ;
682: see the
1.40 aaron 683: .Sx FILES
1.2 deraadt 684: section).
685: .It
1.1 deraadt 686: If the login is on a tty, records login time.
1.2 deraadt 687: .It
688: Checks
689: .Pa /etc/nologin ;
690: if it exists, prints contents and quits
1.1 deraadt 691: (unless root).
1.2 deraadt 692: .It
1.1 deraadt 693: Changes to run with normal user privileges.
1.2 deraadt 694: .It
1.1 deraadt 695: Sets up basic environment.
1.2 deraadt 696: .It
697: Reads
698: .Pa $HOME/.ssh/environment
699: if it exists.
700: .It
1.1 deraadt 701: Changes to user's home directory.
1.2 deraadt 702: .It
703: If
704: .Pa $HOME/.ssh/rc
705: exists, runs it; else if
706: .Pa /etc/sshrc
707: exists, runs
1.36 aaron 708: it; otherwise runs xauth.
709: The
1.2 deraadt 710: .Dq rc
711: files are given the X11
1.1 deraadt 712: authentication protocol and cookie in standard input.
1.2 deraadt 713: .It
1.1 deraadt 714: Runs user's shell or command.
1.2 deraadt 715: .El
716: .Sh AUTHORIZED_KEYS FILE FORMAT
1.40 aaron 717: The
1.2 deraadt 718: .Pa $HOME/.ssh/authorized_keys
1.1 deraadt 719: file lists the RSA keys that are
1.44 deraadt 720: permitted for RSA authentication in SSH protocols 1.3 and 1.5
1.51 hugh 721: Similarly, the
1.44 deraadt 722: .Pa $HOME/.ssh/authorized_keys2
723: file lists the DSA keys that are
724: permitted for DSA authentication in SSH protocol 2.0.
1.36 aaron 725: Each line of the file contains one
1.2 deraadt 726: key (empty lines and lines starting with a
727: .Ql #
728: are ignored as
1.36 aaron 729: comments).
730: Each line consists of the following fields, separated by
731: spaces: options, bits, exponent, modulus, comment.
732: The options field
1.1 deraadt 733: is optional; its presence is determined by whether the line starts
734: with a number or not (the option field never starts with a number).
735: The bits, exponent, modulus and comment fields give the RSA key; the
736: comment field is not used for anything (but may be convenient for the
737: user to identify the key).
1.2 deraadt 738: .Pp
1.1 deraadt 739: Note that lines in this file are usually several hundred bytes long
1.36 aaron 740: (because of the size of the RSA key modulus).
741: You don't want to type them in; instead, copy the
1.2 deraadt 742: .Pa identity.pub
1.1 deraadt 743: file and edit it.
1.2 deraadt 744: .Pp
1.58 deraadt 745: The options (if present) consist of comma-separated option
1.36 aaron 746: specifications.
747: No spaces are permitted, except within double quotes.
1.1 deraadt 748: The following option specifications are supported:
1.2 deraadt 749: .Bl -tag -width Ds
750: .It Cm from="pattern-list"
1.1 deraadt 751: Specifies that in addition to RSA authentication, the canonical name
752: of the remote host must be present in the comma-separated list of
1.36 aaron 753: patterns
754: .Pf ( Ql *
755: and
756: .Ql ?
757: serve as wildcards).
758: The list may also contain
759: patterns negated by prefixing them with
760: .Ql ! ;
761: if the canonical host name matches a negated pattern, the key is not accepted.
762: The purpose
1.1 deraadt 763: of this option is to optionally increase security: RSA authentication
764: by itself does not trust the network or name servers or anything (but
765: the key); however, if somebody somehow steals the key, the key
1.36 aaron 766: permits an intruder to log in from anywhere in the world.
767: This additional option makes using a stolen key more difficult (name
1.1 deraadt 768: servers and/or routers would have to be compromised in addition to
769: just the key).
1.2 deraadt 770: .It Cm command="command"
1.1 deraadt 771: Specifies that the command is executed whenever this key is used for
1.36 aaron 772: authentication.
773: The command supplied by the user (if any) is ignored.
1.1 deraadt 774: The command is run on a pty if the connection requests a pty;
1.36 aaron 775: otherwise it is run without a tty.
776: A quote may be included in the command by quoting it with a backslash.
777: This option might be useful
778: to restrict certain RSA keys to perform just a specific operation.
779: An example might be a key that permits remote backups but nothing else.
1.51 hugh 780: Note that the client may specify TCP/IP and/or X11
781: forwarding unless they are explicitly prohibited.
1.2 deraadt 782: .It Cm environment="NAME=value"
1.1 deraadt 783: Specifies that the string is to be added to the environment when
1.36 aaron 784: logging in using this key.
785: Environment variables set this way
786: override other default environment values.
787: Multiple options of this type are permitted.
1.2 deraadt 788: .It Cm no-port-forwarding
1.1 deraadt 789: Forbids TCP/IP forwarding when this key is used for authentication.
1.36 aaron 790: Any port forward requests by the client will return an error.
791: This might be used, e.g., in connection with the
1.2 deraadt 792: .Cm command
1.1 deraadt 793: option.
1.2 deraadt 794: .It Cm no-X11-forwarding
1.1 deraadt 795: Forbids X11 forwarding when this key is used for authentication.
796: Any X11 forward requests by the client will return an error.
1.2 deraadt 797: .It Cm no-agent-forwarding
1.1 deraadt 798: Forbids authentication agent forwarding when this key is used for
799: authentication.
1.2 deraadt 800: .It Cm no-pty
1.1 deraadt 801: Prevents tty allocation (a request to allocate a pty will fail).
1.2 deraadt 802: .El
803: .Ss Examples
1.1 deraadt 804: 1024 33 12121.\|.\|.\|312314325 ylo@foo.bar
1.2 deraadt 805: .Pp
1.1 deraadt 806: from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23.\|.\|.\|2334 ylo@niksula
1.2 deraadt 807: .Pp
1.1 deraadt 808: command="dump /home",no-pty,no-port-forwarding 1024 33 23.\|.\|.\|2323 backup.hut.fi
1.2 deraadt 809: .Sh SSH_KNOWN_HOSTS FILE FORMAT
1.40 aaron 810: The
1.44 deraadt 811: .Pa /etc/ssh_known_hosts ,
812: .Pa /etc/ssh_known_hosts2 ,
813: .Pa $HOME/.ssh/known_hosts ,
1.40 aaron 814: and
1.44 deraadt 815: .Pa $HOME/.ssh/known_hosts2
1.36 aaron 816: files contain host public keys for all known hosts.
817: The global file should
1.37 brad 818: be prepared by the administrator (optional), and the per-user file is
1.58 deraadt 819: maintained automatically: whenever the user connects from an unknown host
1.36 aaron 820: its key is added to the per-user file.
1.2 deraadt 821: .Pp
1.1 deraadt 822: Each line in these files contains the following fields: hostnames,
1.36 aaron 823: bits, exponent, modulus, comment.
824: The fields are separated by spaces.
1.2 deraadt 825: .Pp
1.1 deraadt 826: Hostnames is a comma-separated list of patterns ('*' and '?' act as
827: wildcards); each pattern in turn is matched against the canonical host
828: name (when authenticating a client) or against the user-supplied
1.36 aaron 829: name (when authenticating a server).
830: A pattern may also be preceded by
1.2 deraadt 831: .Ql !
832: to indicate negation: if the host name matches a negated
1.1 deraadt 833: pattern, it is not accepted (by that line) even if it matched another
834: pattern on the line.
1.2 deraadt 835: .Pp
1.49 markus 836: Bits, exponent, and modulus are taken directly from the RSA host key; they
1.2 deraadt 837: can be obtained, e.g., from
838: .Pa /etc/ssh_host_key.pub .
1.1 deraadt 839: The optional comment field continues to the end of the line, and is not used.
1.2 deraadt 840: .Pp
841: Lines starting with
842: .Ql #
843: and empty lines are ignored as comments.
844: .Pp
1.1 deraadt 845: When performing host authentication, authentication is accepted if any
1.36 aaron 846: matching line has the proper key.
847: It is thus permissible (but not
1.1 deraadt 848: recommended) to have several lines or different host keys for the same
1.36 aaron 849: names.
850: This will inevitably happen when short forms of host names
851: from different domains are put in the file.
852: It is possible
1.1 deraadt 853: that the files contain conflicting information; authentication is
854: accepted if valid information can be found from either file.
1.2 deraadt 855: .Pp
1.1 deraadt 856: Note that the lines in these files are typically hundreds of characters
857: long, and you definitely don't want to type in the host keys by hand.
1.6 aaron 858: Rather, generate them by a script
1.40 aaron 859: or by taking
1.2 deraadt 860: .Pa /etc/ssh_host_key.pub
1.1 deraadt 861: and adding the host names at the front.
1.2 deraadt 862: .Ss Examples
1.1 deraadt 863: closenet,closenet.hut.fi,.\|.\|.\|,130.233.208.41 1024 37 159.\|.\|.93 closenet.hut.fi
1.2 deraadt 864: .Sh FILES
865: .Bl -tag -width Ds
866: .It Pa /etc/sshd_config
1.1 deraadt 867: Contains configuration data for
1.2 deraadt 868: .Nm sshd .
1.1 deraadt 869: This file should be writable by root only, but it is recommended
870: (though not necessary) that it be world-readable.
1.2 deraadt 871: .It Pa /etc/ssh_host_key
1.7 markus 872: Contains the private part of the host key.
1.1 deraadt 873: This file should only be owned by root, readable only by root, and not
874: accessible to others.
1.14 markus 875: Note that
876: .Nm
877: does not start if this file is group/world-accessible.
1.2 deraadt 878: .It Pa /etc/ssh_host_key.pub
1.7 markus 879: Contains the public part of the host key.
880: This file should be world-readable but writable only by
1.36 aaron 881: root.
882: Its contents should match the private part.
883: This file is not
1.1 deraadt 884: really used for anything; it is only provided for the convenience of
885: the user so its contents can be copied to known hosts files.
1.7 markus 886: These two files are created using
887: .Xr ssh-keygen 1 .
1.2 deraadt 888: .It Pa /var/run/sshd.pid
889: Contains the process ID of the
890: .Nm
1.1 deraadt 891: listening for connections (if there are several daemons running
892: concurrently for different ports, this contains the pid of the one
1.36 aaron 893: started last).
1.58 deraadt 894: The content of this file is not sensitive; it can be world-readable.
1.2 deraadt 895: .It Pa $HOME/.ssh/authorized_keys
1.1 deraadt 896: Lists the RSA keys that can be used to log into the user's account.
897: This file must be readable by root (which may on some machines imply
898: it being world-readable if the user's home directory resides on an NFS
1.36 aaron 899: volume).
900: It is recommended that it not be accessible by others.
901: The format of this file is described above.
1.44 deraadt 902: Users will place the contents of their
903: .Pa identity.pub
904: files into this file, as described in
905: .Xr ssh-keygen 1 .
906: .It Pa $HOME/.ssh/authorized_keys2
907: Lists the DSA keys that can be used to log into the user's account.
908: This file must be readable by root (which may on some machines imply
909: it being world-readable if the user's home directory resides on an NFS
910: volume).
911: It is recommended that it not be accessible by others.
912: The format of this file is described above.
913: Users will place the contents of their
914: .Pa id_dsa.pub
915: files into this file, as described in
916: .Xr ssh-keygen 1 .
1.22 markus 917: .It Pa "/etc/ssh_known_hosts" and "$HOME/.ssh/known_hosts"
918: These files are consulted when using rhosts with RSA host
1.36 aaron 919: authentication to check the public key of the host.
920: The key must be listed in one of these files to be accepted.
1.22 markus 921: The client uses the same files
1.58 deraadt 922: to verify that the remote host is the one it intended to connect.
1.36 aaron 923: These files should be writable only by root/the owner.
1.2 deraadt 924: .Pa /etc/ssh_known_hosts
925: should be world-readable, and
926: .Pa $HOME/.ssh/known_hosts
927: can but need not be world-readable.
1.6 aaron 928: .It Pa /etc/nologin
1.40 aaron 929: If this file exists,
1.2 deraadt 930: .Nm
1.36 aaron 931: refuses to let anyone except root log in.
932: The contents of the file
1.1 deraadt 933: are displayed to anyone trying to log in, and non-root connections are
1.36 aaron 934: refused.
935: The file should be world-readable.
1.19 dugsong 936: .It Pa /etc/hosts.allow, /etc/hosts.deny
937: If compiled with
938: .Sy LIBWRAP
939: support, tcp-wrappers access controls may be defined here as described in
940: .Xr hosts_access 5 .
1.6 aaron 941: .It Pa $HOME/.rhosts
1.1 deraadt 942: This file contains host-username pairs, separated by a space, one per
1.36 aaron 943: line.
944: The given user on the corresponding host is permitted to log in
945: without password.
946: The same file is used by rlogind and rshd.
1.6 aaron 947: The file must
1.1 deraadt 948: be writable only by the user; it is recommended that it not be
949: accessible by others.
1.2 deraadt 950: .Pp
1.36 aaron 951: If is also possible to use netgroups in the file.
952: Either host or user
1.1 deraadt 953: name may be of the form +@groupname to specify all hosts or all users
954: in the group.
1.2 deraadt 955: .It Pa $HOME/.shosts
956: For ssh,
957: this file is exactly the same as for
958: .Pa .rhosts .
959: However, this file is
960: not used by rlogin and rshd, so using this permits access using SSH only.
1.58 deraadt 961: .It Pa /etc/hosts.equiv
1.2 deraadt 962: This file is used during
963: .Pa .rhosts
1.36 aaron 964: authentication.
965: In the simplest form, this file contains host names, one per line.
966: Users on
1.1 deraadt 967: those hosts are permitted to log in without a password, provided they
1.36 aaron 968: have the same user name on both machines.
969: The host name may also be
1.1 deraadt 970: followed by a user name; such users are permitted to log in as
1.2 deraadt 971: .Em any
1.36 aaron 972: user on this machine (except root).
973: Additionally, the syntax
1.2 deraadt 974: .Dq +@group
1.36 aaron 975: can be used to specify netgroups.
976: Negated entries start with
1.2 deraadt 977: .Ql \&- .
978: .Pp
1.1 deraadt 979: If the client host/user is successfully matched in this file, login is
980: automatically permitted provided the client and server user names are the
1.36 aaron 981: same.
982: Additionally, successful RSA host authentication is normally required.
983: This file must be writable only by root; it is recommended
1.1 deraadt 984: that it be world-readable.
1.2 deraadt 985: .Pp
1.6 aaron 986: .Sy "Warning: It is almost never a good idea to use user names in"
1.2 deraadt 987: .Pa hosts.equiv .
1.1 deraadt 988: Beware that it really means that the named user(s) can log in as
1.2 deraadt 989: .Em anybody ,
1.1 deraadt 990: which includes bin, daemon, adm, and other accounts that own critical
1.36 aaron 991: binaries and directories.
992: Using a user name practically grants the user root access.
993: The only valid use for user names that I can think
1.1 deraadt 994: of is in negative entries.
1.2 deraadt 995: .Pp
996: Note that this warning also applies to rsh/rlogin.
997: .It Pa /etc/shosts.equiv
1.1 deraadt 998: This is processed exactly as
1.2 deraadt 999: .Pa /etc/hosts.equiv .
1.1 deraadt 1000: However, this file may be useful in environments that want to run both
1.2 deraadt 1001: rsh/rlogin and ssh.
1.6 aaron 1002: .It Pa $HOME/.ssh/environment
1.36 aaron 1003: This file is read into the environment at login (if it exists).
1004: It can only contain empty lines, comment lines (that start with
1.2 deraadt 1005: .Ql # ) ,
1.36 aaron 1006: and assignment lines of the form name=value.
1007: The file should be writable
1.6 aaron 1008: only by the user; it need not be readable by anyone else.
1.2 deraadt 1009: .It Pa $HOME/.ssh/rc
1.1 deraadt 1010: If this file exists, it is run with /bin/sh after reading the
1.36 aaron 1011: environment files but before starting the user's shell or command.
1012: If X11 spoofing is in use, this will receive the "proto cookie" pair in
1.2 deraadt 1013: standard input (and
1014: .Ev DISPLAY
1.36 aaron 1015: in environment).
1016: This must call
1.2 deraadt 1017: .Xr xauth 1
1018: in that case.
1019: .Pp
1.1 deraadt 1020: The primary purpose of this file is to run any initialization routines
1021: which may be needed before the user's home directory becomes
1022: accessible; AFS is a particular example of such an environment.
1.2 deraadt 1023: .Pp
1.1 deraadt 1024: This file will probably contain some initialization code followed by
1025: something similar to: "if read proto cookie; then echo add $DISPLAY
1026: $proto $cookie | xauth -q -; fi".
1.2 deraadt 1027: .Pp
1028: If this file does not exist,
1029: .Pa /etc/sshrc
1030: is run, and if that
1.1 deraadt 1031: does not exist either, xauth is used to store the cookie.
1.2 deraadt 1032: .Pp
1.1 deraadt 1033: This file should be writable only by the user, and need not be
1034: readable by anyone else.
1.2 deraadt 1035: .It Pa /etc/sshrc
1036: Like
1037: .Pa $HOME/.ssh/rc .
1038: This can be used to specify
1.36 aaron 1039: machine-specific login-time initializations globally.
1040: This file should be writable only by root, and should be world-readable.
1.56 aaron 1041: .El
1.71 ! aaron 1042: .Sh AUTHORS
1.17 deraadt 1043: OpenSSH
1.33 deraadt 1044: is a derivative of the original (free) ssh 1.2.12 release by Tatu Ylonen,
1.36 aaron 1045: but with bugs removed and newer features re-added.
1046: Rapidly after the
1.33 deraadt 1047: 1.2.12 release, newer versions of the original ssh bore successively
1048: more restrictive licenses, and thus demand for a free version was born.
1.48 markus 1049: .Pp
1.33 deraadt 1050: This version of OpenSSH
1.17 deraadt 1051: .Bl -bullet
1052: .It
1.32 aaron 1053: has all components of a restrictive nature (i.e., patents, see
1.17 deraadt 1054: .Xr ssl 8 )
1055: directly removed from the source code; any licensed or patented components
1056: are chosen from
1057: external libraries.
1058: .It
1.48 markus 1059: has been updated to support SSH protocol 1.5 and 2, making it compatible with
1060: all other SSH clients and servers.
1.17 deraadt 1061: .It
1.40 aaron 1062: contains added support for
1.17 deraadt 1063: .Xr kerberos 8
1064: authentication and ticket passing.
1065: .It
1066: supports one-time password authentication with
1067: .Xr skey 1 .
1068: .El
1.48 markus 1069: .Pp
1070: OpenSSH has been created by Aaron Campbell, Bob Beck, Markus Friedl,
1071: Niels Provos, Theo de Raadt, and Dug Song.
1072: .Pp
1073: The support for SSH protocol 2 was written by Markus Friedl.
1.2 deraadt 1074: .Sh SEE ALSO
1075: .Xr scp 1 ,
1.63 markus 1076: .Xr sftp-server 8 ,
1.2 deraadt 1077: .Xr ssh 1 ,
1.5 deraadt 1078: .Xr ssh-add 1 ,
1.2 deraadt 1079: .Xr ssh-agent 1 ,
1.5 deraadt 1080: .Xr ssh-keygen 1 ,
1.38 deraadt 1081: .Xr ssl 8 ,
1082: .Xr rlogin 1 ,
1083: .Xr rsh 1
![[BACK]](/icons/back.gif){kind=icon}
Return to sshd.8 CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh