Annotation of src/usr.bin/ssh/ssh.1, Revision 1.439
1.1 deraadt 1: .\"
2: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
3: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4: .\" All rights reserved
5: .\"
1.59 deraadt 6: .\" As far as I am concerned, the code I have written for this software
7: .\" can be used freely for any purpose. Any derived versions of this
8: .\" software must be clearly marked as such, and if the derived work is
9: .\" incompatible with the protocol description in the RFC file, it must be
10: .\" called by a name other than "ssh" or "Secure Shell".
11: .\"
1.93 deraadt 12: .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
13: .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
14: .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
1.59 deraadt 15: .\"
16: .\" Redistribution and use in source and binary forms, with or without
17: .\" modification, are permitted provided that the following conditions
18: .\" are met:
19: .\" 1. Redistributions of source code must retain the above copyright
20: .\" notice, this list of conditions and the following disclaimer.
21: .\" 2. Redistributions in binary form must reproduce the above copyright
22: .\" notice, this list of conditions and the following disclaimer in the
23: .\" documentation and/or other materials provided with the distribution.
1.1 deraadt 24: .\"
1.59 deraadt 25: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
26: .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
27: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
28: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
29: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
30: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
31: .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
32: .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
33: .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
34: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.1 deraadt 35: .\"
1.439 ! job 36: .\" $OpenBSD: ssh.1,v 1.438 2023/10/11 23:14:33 djm Exp $
! 37: .Dd $Mdocdate: October 11 2023 $
1.2 deraadt 38: .Dt SSH 1
39: .Os
40: .Sh NAME
41: .Nm ssh
1.408 jmc 42: .Nd OpenSSH remote login client
1.2 deraadt 43: .Sh SYNOPSIS
44: .Nm ssh
1.377 djm 45: .Op Fl 46AaCfGgKkMNnqsTtVvXxYy
1.390 djm 46: .Op Fl B Ar bind_interface
1.108 markus 47: .Op Fl b Ar bind_address
1.51 markus 48: .Op Fl c Ar cipher_spec
1.306 jmc 49: .Op Fl D Oo Ar bind_address : Oc Ns Ar port
1.331 dtucker 50: .Op Fl E Ar log_file
1.2 deraadt 51: .Op Fl e Ar escape_char
1.176 jmc 52: .Op Fl F Ar configfile
1.292 jmc 53: .Op Fl I Ar pkcs11
1.2 deraadt 54: .Op Fl i Ar identity_file
1.386 millert 55: .Op Fl J Ar destination
1.360 millert 56: .Op Fl L Ar address
1.176 jmc 57: .Op Fl l Ar login_name
58: .Op Fl m Ar mac_spec
1.198 djm 59: .Op Fl O Ar ctl_cmd
1.176 jmc 60: .Op Fl o Ar option
1.436 jmc 61: .Op Fl P Ar tag
1.176 jmc 62: .Op Fl p Ar port
1.360 millert 63: .Op Fl R Ar address
1.198 djm 64: .Op Fl S Ar ctl_path
1.290 dtucker 65: .Op Fl W Ar host : Ns Ar port
1.306 jmc 66: .Op Fl w Ar local_tun Ns Op : Ns Ar remote_tun
1.386 millert 67: .Ar destination
1.427 dtucker 68: .Op Ar command Op Ar argument ...
1.438 djm 69: .Nm
70: .Op Fl Q Ar query_option
1.44 aaron 71: .Sh DESCRIPTION
1.2 deraadt 72: .Nm
1.96 deraadt 73: (SSH client) is a program for logging into a remote machine and for
1.40 aaron 74: executing commands on a remote machine.
1.365 mmcc 75: It is intended to provide secure encrypted communications between
1.40 aaron 76: two untrusted hosts over an insecure network.
1.348 millert 77: X11 connections, arbitrary TCP ports and
78: .Ux Ns -domain
79: sockets can also be forwarded over the secure channel.
1.2 deraadt 80: .Pp
81: .Nm
1.44 aaron 82: connects and logs into the specified
1.388 jmc 83: .Ar destination ,
1.386 millert 84: which may be specified as either
1.388 jmc 85: .Sm off
86: .Oo user @ Oc hostname
87: .Sm on
88: or a URI of the form
89: .Sm off
90: .No ssh:// Oo user @ Oc hostname Op : port .
91: .Sm on
1.1 deraadt 92: The user must prove
1.420 dtucker 93: their identity to the remote machine using one of several methods
1.365 mmcc 94: (see below).
1.49 markus 95: .Pp
1.386 millert 96: If a
1.176 jmc 97: .Ar command
98: is specified,
1.427 dtucker 99: it will be executed on the remote host instead of a login shell.
100: A complete command line may be specified as
101: .Ar command ,
102: or it may have additional arguments.
103: If supplied, the arguments will be appended to the command, separated by
104: spaces, before it is sent to the server to be executed.
1.2 deraadt 105: .Pp
1.218 jmc 106: The options are as follows:
1.361 millert 107: .Pp
1.360 millert 108: .Bl -tag -width Ds -compact
1.218 jmc 109: .It Fl 4
110: Forces
1.2 deraadt 111: .Nm
1.218 jmc 112: to use IPv4 addresses only.
1.360 millert 113: .Pp
1.218 jmc 114: .It Fl 6
115: Forces
1.2 deraadt 116: .Nm
1.218 jmc 117: to use IPv6 addresses only.
1.360 millert 118: .Pp
1.218 jmc 119: .It Fl A
1.407 jmc 120: Enables forwarding of connections from an authentication agent such as
121: .Xr ssh-agent 1 .
1.218 jmc 122: This can also be specified on a per-host basis in a configuration file.
1.2 deraadt 123: .Pp
1.218 jmc 124: Agent forwarding should be enabled with caution.
125: Users with the ability to bypass file permissions on the remote host
1.285 sobrado 126: (for the agent's
1.286 sobrado 127: .Ux Ns -domain
128: socket) can access the local agent through the forwarded connection.
1.218 jmc 129: An attacker cannot obtain key material from the agent,
130: however they can perform operations on the keys that enable them to
131: authenticate using the identities loaded into the agent.
1.407 jmc 132: A safer alternative may be to use a jump host
133: (see
134: .Fl J ) .
1.360 millert 135: .Pp
1.218 jmc 136: .It Fl a
137: Disables forwarding of the authentication agent connection.
1.390 djm 138: .Pp
1.391 jmc 139: .It Fl B Ar bind_interface
1.390 djm 140: Bind to the address of
1.391 jmc 141: .Ar bind_interface
1.390 djm 142: before attempting to connect to the destination host.
143: This is only useful on systems with more than one address.
1.360 millert 144: .Pp
1.218 jmc 145: .It Fl b Ar bind_address
146: Use
147: .Ar bind_address
148: on the local machine as the source address
149: of the connection.
150: Only useful on systems with more than one address.
1.360 millert 151: .Pp
1.218 jmc 152: .It Fl C
153: Requests compression of all data (including stdin, stdout, stderr, and
1.348 millert 154: data for forwarded X11, TCP and
155: .Ux Ns -domain
156: connections).
1.218 jmc 157: The compression algorithm is the same used by
1.377 djm 158: .Xr gzip 1 .
1.218 jmc 159: Compression is desirable on modem lines and other
160: slow connections, but will only slow down things on fast networks.
161: The default value can be set on a host-by-host basis in the
162: configuration files; see the
163: .Cm Compression
1.431 jmc 164: option in
165: .Xr ssh_config 5 .
1.360 millert 166: .Pp
1.218 jmc 167: .It Fl c Ar cipher_spec
168: Selects the cipher specification for encrypting the session.
169: .Ar cipher_spec
170: is a comma-separated list of ciphers
171: listed in order of preference.
1.283 jmc 172: See the
173: .Cm Ciphers
1.307 dtucker 174: keyword in
175: .Xr ssh_config 5
176: for more information.
1.360 millert 177: .Pp
1.218 jmc 178: .It Fl D Xo
179: .Sm off
180: .Oo Ar bind_address : Oc
181: .Ar port
182: .Sm on
183: .Xc
184: Specifies a local
185: .Dq dynamic
186: application-level port forwarding.
187: This works by allocating a socket to listen to
188: .Ar port
189: on the local side, optionally bound to the specified
190: .Ar bind_address .
191: Whenever a connection is made to this port, the
192: connection is forwarded over the secure channel, and the application
193: protocol is then used to determine where to connect to from the
194: remote machine.
195: Currently the SOCKS4 and SOCKS5 protocols are supported, and
1.107 markus 196: .Nm
1.218 jmc 197: will act as a SOCKS server.
198: Only root can forward privileged ports.
199: Dynamic port forwardings can also be specified in the configuration file.
1.49 markus 200: .Pp
1.308 djm 201: IPv6 addresses can be specified by enclosing the address in square brackets.
1.218 jmc 202: Only the superuser can forward privileged ports.
203: By default, the local port is bound in accordance with the
204: .Cm GatewayPorts
205: setting.
206: However, an explicit
207: .Ar bind_address
208: may be used to bind the connection to a specific address.
209: The
210: .Ar bind_address
211: of
212: .Dq localhost
213: indicates that the listening port be bound for local use only, while an
214: empty address or
215: .Sq *
216: indicates that the port should be available from all interfaces.
1.360 millert 217: .Pp
1.331 dtucker 218: .It Fl E Ar log_file
219: Append debug logs to
220: .Ar log_file
221: instead of standard error.
1.360 millert 222: .Pp
1.229 jmc 223: .It Fl e Ar escape_char
1.218 jmc 224: Sets the escape character for sessions with a pty (default:
225: .Ql ~ ) .
226: The escape character is only recognized at the beginning of a line.
227: The escape character followed by a dot
228: .Pq Ql \&.
229: closes the connection;
230: followed by control-Z suspends the connection;
231: and followed by itself sends the escape character once.
232: Setting the character to
1.2 deraadt 233: .Dq none
1.218 jmc 234: disables any escapes and makes the session fully transparent.
1.360 millert 235: .Pp
1.218 jmc 236: .It Fl F Ar configfile
237: Specifies an alternative per-user configuration file.
238: If a configuration file is given on the command line,
239: the system-wide configuration file
240: .Pq Pa /etc/ssh/ssh_config
241: will be ignored.
242: The default for the per-user configuration file is
243: .Pa ~/.ssh/config .
1.411 naddy 244: If set to
245: .Dq none ,
246: no configuration files will be read.
1.360 millert 247: .Pp
1.218 jmc 248: .It Fl f
249: Requests
250: .Nm
251: to go to background just before command execution.
252: This is useful if
1.176 jmc 253: .Nm
1.218 jmc 254: is going to ask for passwords or passphrases, but the user
255: wants it in the background.
256: This implies
257: .Fl n .
258: The recommended way to start X11 programs at a remote site is with
259: something like
260: .Ic ssh -f host xterm .
1.277 djm 261: .Pp
262: If the
263: .Cm ExitOnForwardFailure
264: configuration option is set to
265: .Dq yes ,
266: then a client started with
267: .Fl f
268: will wait for all remote port forwards to be successfully established
269: before placing itself in the background.
1.424 djm 270: Refer to the description of
271: .Cm ForkAfterAuthentication
272: in
273: .Xr ssh_config 5
274: for details.
1.360 millert 275: .Pp
1.350 djm 276: .It Fl G
277: Causes
278: .Nm
279: to print its configuration after evaluating
280: .Cm Host
281: and
282: .Cm Match
283: blocks and exit.
1.360 millert 284: .Pp
1.218 jmc 285: .It Fl g
286: Allows remote hosts to connect to local forwarded ports.
1.346 djm 287: If used on a multiplexed connection, then this option must be specified
288: on the master process.
1.360 millert 289: .Pp
1.291 markus 290: .It Fl I Ar pkcs11
1.294 jmc 291: Specify the PKCS#11 shared library
1.176 jmc 292: .Nm
1.401 naddy 293: should use to communicate with a PKCS#11 token providing keys for user
294: authentication.
1.360 millert 295: .Pp
1.218 jmc 296: .It Fl i Ar identity_file
297: Selects a file from which the identity (private key) for
1.310 djm 298: public key authentication is read.
1.426 dtucker 299: You can also specify a public key file to use the corresponding
300: private key that is loaded in
301: .Xr ssh-agent 1
302: when the private key file is not present locally.
1.218 jmc 303: The default is
1.428 dtucker 304: .Pa ~/.ssh/id_rsa ,
1.343 naddy 305: .Pa ~/.ssh/id_ecdsa ,
1.404 naddy 306: .Pa ~/.ssh/id_ecdsa_sk ,
1.406 naddy 307: .Pa ~/.ssh/id_ed25519 ,
308: .Pa ~/.ssh/id_ed25519_sk
1.310 djm 309: and
1.428 dtucker 310: .Pa ~/.ssh/id_dsa .
1.218 jmc 311: Identity files may also be specified on
312: a per-host basis in the configuration file.
313: It is possible to have multiple
314: .Fl i
315: options (and multiple identities specified in
316: configuration files).
1.364 jmc 317: If no certificates have been explicitly specified by the
1.363 djm 318: .Cm CertificateFile
319: directive,
1.302 djm 320: .Nm
321: will also try to load certificate information from the filename obtained
322: by appending
323: .Pa -cert.pub
324: to identity filenames.
1.360 millert 325: .Pp
1.386 millert 326: .It Fl J Ar destination
1.437 naddy 327: Connect to the target host by first making an
1.375 djm 328: .Nm
1.386 millert 329: connection to the jump host described by
330: .Ar destination
1.376 jmc 331: and then establishing a TCP forwarding to the ultimate destination from
1.375 djm 332: there.
333: Multiple jump hops may be specified separated by comma characters.
1.439 ! job 334: IPv6 addresses can be specified by enclosing the address in square brackets.
1.375 djm 335: This is a shortcut to specify a
336: .Cm ProxyJump
337: configuration directive.
1.400 djm 338: Note that configuration directives supplied on the command-line generally
339: apply to the destination host and not any specified jump hosts.
340: Use
341: .Pa ~/.ssh/config
342: to specify configuration for jump hosts.
1.375 djm 343: .Pp
1.269 djm 344: .It Fl K
345: Enables GSSAPI-based authentication and forwarding (delegation) of GSSAPI
346: credentials to the server.
1.360 millert 347: .Pp
1.218 jmc 348: .It Fl k
349: Disables forwarding (delegation) of GSSAPI credentials to the server.
1.360 millert 350: .Pp
1.218 jmc 351: .It Fl L Xo
352: .Sm off
353: .Oo Ar bind_address : Oc
354: .Ar port : host : hostport
355: .Sm on
356: .Xc
1.360 millert 357: .It Fl L Xo
358: .Sm off
359: .Oo Ar bind_address : Oc
360: .Ar port : remote_socket
361: .Sm on
362: .Xc
363: .It Fl L Xo
364: .Sm off
365: .Ar local_socket : host : hostport
366: .Sm on
367: .Xc
368: .It Fl L Xo
369: .Sm off
370: .Ar local_socket : remote_socket
371: .Sm on
372: .Xc
373: Specifies that connections to the given TCP port or Unix socket on the local
374: (client) host are to be forwarded to the given host and port, or Unix socket,
375: on the remote side.
376: This works by allocating a socket to listen to either a TCP
1.218 jmc 377: .Ar port
378: on the local side, optionally bound to the specified
1.360 millert 379: .Ar bind_address ,
380: or to a Unix socket.
381: Whenever a connection is made to the local port or socket, the
1.218 jmc 382: connection is forwarded over the secure channel, and a connection is
1.360 millert 383: made to either
1.218 jmc 384: .Ar host
385: port
1.360 millert 386: .Ar hostport ,
387: or the Unix socket
388: .Ar remote_socket ,
1.218 jmc 389: from the remote machine.
1.360 millert 390: .Pp
1.218 jmc 391: Port forwardings can also be specified in the configuration file.
1.360 millert 392: Only the superuser can forward privileged ports.
1.308 djm 393: IPv6 addresses can be specified by enclosing the address in square brackets.
1.360 millert 394: .Pp
1.218 jmc 395: By default, the local port is bound in accordance with the
396: .Cm GatewayPorts
397: setting.
398: However, an explicit
399: .Ar bind_address
400: may be used to bind the connection to a specific address.
1.2 deraadt 401: The
1.218 jmc 402: .Ar bind_address
403: of
404: .Dq localhost
405: indicates that the listening port be bound for local use only, while an
406: empty address or
407: .Sq *
408: indicates that the port should be available from all interfaces.
1.360 millert 409: .Pp
1.218 jmc 410: .It Fl l Ar login_name
411: Specifies the user to log in as on the remote machine.
412: This also may be specified on a per-host basis in the configuration file.
1.360 millert 413: .Pp
1.218 jmc 414: .It Fl M
415: Places the
416: .Nm
417: client into
418: .Dq master
419: mode for connection sharing.
1.231 stevesk 420: Multiple
421: .Fl M
422: options places
423: .Nm
424: into
425: .Dq master
1.397 djm 426: mode but with confirmation required using
427: .Xr ssh-askpass 1
428: before each operation that changes the multiplexing state
429: (e.g. opening a new session).
1.218 jmc 430: Refer to the description of
431: .Cm ControlMaster
432: in
433: .Xr ssh_config 5
434: for details.
1.360 millert 435: .Pp
1.218 jmc 436: .It Fl m Ar mac_spec
1.369 jmc 437: A comma-separated list of MAC (message authentication code) algorithms,
438: specified in order of preference.
1.218 jmc 439: See the
440: .Cm MACs
1.431 jmc 441: keyword in
442: .Xr ssh_config 5
443: for more information.
1.360 millert 444: .Pp
1.218 jmc 445: .It Fl N
446: Do not execute a remote command.
1.369 jmc 447: This is useful for just forwarding ports.
1.422 djm 448: Refer to the description of
449: .Cm SessionType
450: in
451: .Xr ssh_config 5
452: for details.
1.360 millert 453: .Pp
1.218 jmc 454: .It Fl n
455: Redirects stdin from
456: .Pa /dev/null
457: (actually, prevents reading from stdin).
458: This must be used when
1.2 deraadt 459: .Nm
1.218 jmc 460: is run in the background.
461: A common trick is to use this to run X11 programs on a remote machine.
462: For example,
463: .Ic ssh -n shadows.cs.hut.fi emacs &
464: will start an emacs on shadows.cs.hut.fi, and the X11
465: connection will be automatically forwarded over an encrypted channel.
466: The
1.2 deraadt 467: .Nm
1.218 jmc 468: program will be put in the background.
469: (This does not work if
1.2 deraadt 470: .Nm
1.218 jmc 471: needs to ask for a password or passphrase; see also the
472: .Fl f
473: option.)
1.423 djm 474: Refer to the description of
475: .Cm StdinNull
476: in
477: .Xr ssh_config 5
478: for details.
1.360 millert 479: .Pp
1.218 jmc 480: .It Fl O Ar ctl_cmd
481: Control an active connection multiplexing master process.
482: When the
483: .Fl O
484: option is specified, the
485: .Ar ctl_cmd
486: argument is interpreted and passed to the master process.
487: Valid commands are:
488: .Dq check
1.305 markus 489: (check that the master process is running),
490: .Dq forward
1.318 jmc 491: (request forwardings without command execution),
1.323 okan 492: .Dq cancel
493: (cancel forwardings),
1.218 jmc 494: .Dq exit
1.318 jmc 495: (request the master to exit), and
1.317 djm 496: .Dq stop
497: (request the master to stop accepting further multiplexing requests).
1.360 millert 498: .Pp
1.218 jmc 499: .It Fl o Ar option
500: Can be used to give options in the format used in the configuration file.
501: This is useful for specifying options for which there is no separate
502: command-line flag.
503: For full details of the options listed below, and their possible values, see
504: .Xr ssh_config 5 .
1.2 deraadt 505: .Pp
1.218 jmc 506: .Bl -tag -width Ds -offset indent -compact
1.366 jcs 507: .It AddKeysToAgent
1.218 jmc 508: .It AddressFamily
509: .It BatchMode
510: .It BindAddress
1.338 djm 511: .It CanonicalDomains
1.339 djm 512: .It CanonicalizeFallbackLocal
513: .It CanonicalizeHostname
514: .It CanonicalizeMaxDots
515: .It CanonicalizePermittedCNAMEs
1.399 jmc 516: .It CASignatureAlgorithms
1.363 djm 517: .It CertificateFile
1.218 jmc 518: .It CheckHostIP
519: .It Ciphers
520: .It ClearAllForwardings
521: .It Compression
1.380 naddy 522: .It ConnectionAttempts
1.218 jmc 523: .It ConnectTimeout
524: .It ControlMaster
525: .It ControlPath
1.321 djm 526: .It ControlPersist
1.218 jmc 527: .It DynamicForward
1.433 djm 528: .It EnableEscapeCommandline
1.218 jmc 529: .It EscapeChar
1.263 markus 530: .It ExitOnForwardFailure
1.353 jmc 531: .It FingerprintHash
1.424 djm 532: .It ForkAfterAuthentication
1.218 jmc 533: .It ForwardAgent
534: .It ForwardX11
1.321 djm 535: .It ForwardX11Timeout
1.218 jmc 536: .It ForwardX11Trusted
537: .It GatewayPorts
538: .It GlobalKnownHostsFile
539: .It GSSAPIAuthentication
540: .It GSSAPIDelegateCredentials
541: .It HashKnownHosts
542: .It Host
1.418 naddy 543: .It HostbasedAcceptedAlgorithms
1.218 jmc 544: .It HostbasedAuthentication
545: .It HostKeyAlgorithms
546: .It HostKeyAlias
1.403 jmc 547: .It Hostname
1.374 jmc 548: .It IdentitiesOnly
1.371 markus 549: .It IdentityAgent
1.218 jmc 550: .It IdentityFile
1.316 jmc 551: .It IPQoS
1.321 djm 552: .It KbdInteractiveAuthentication
1.218 jmc 553: .It KbdInteractiveDevices
1.314 jmc 554: .It KexAlgorithms
1.415 djm 555: .It KnownHostsCommand
1.218 jmc 556: .It LocalCommand
557: .It LocalForward
558: .It LogLevel
559: .It MACs
1.337 jmc 560: .It Match
1.218 jmc 561: .It NoHostAuthenticationForLocalhost
562: .It NumberOfPasswordPrompts
563: .It PasswordAuthentication
564: .It PermitLocalCommand
1.419 markus 565: .It PermitRemoteOpen
1.291 markus 566: .It PKCS11Provider
1.218 jmc 567: .It Port
568: .It PreferredAuthentications
569: .It ProxyCommand
1.375 djm 570: .It ProxyJump
1.336 jmc 571: .It ProxyUseFdpass
1.416 dtucker 572: .It PubkeyAcceptedAlgorithms
1.218 jmc 573: .It PubkeyAuthentication
1.251 dtucker 574: .It RekeyLimit
1.382 bluhm 575: .It RemoteCommand
1.218 jmc 576: .It RemoteForward
1.319 jmc 577: .It RequestTTY
1.432 djm 578: .It RequiredRSASize
1.218 jmc 579: .It SendEnv
580: .It ServerAliveInterval
581: .It ServerAliveCountMax
1.422 djm 582: .It SessionType
1.395 jmc 583: .It SetEnv
1.423 djm 584: .It StdinNull
1.347 jmc 585: .It StreamLocalBindMask
586: .It StreamLocalBindUnlink
1.218 jmc 587: .It StrictHostKeyChecking
588: .It TCPKeepAlive
589: .It Tunnel
590: .It TunnelDevice
1.354 djm 591: .It UpdateHostKeys
1.218 jmc 592: .It User
593: .It UserKnownHostsFile
594: .It VerifyHostKeyDNS
1.276 jmc 595: .It VisualHostKey
1.218 jmc 596: .It XAuthLocation
597: .El
1.360 millert 598: .Pp
1.435 djm 599: .It Fl P Ar tag
600: Specify a tag name that may be used to select configuration in
601: .Xr ssh_config 5 .
602: Refer to the
603: .Cm Tag
604: and
605: .Cm Match
606: keywords in
607: .Xr ssh_config 5
608: for more information.
1.218 jmc 609: .It Fl p Ar port
610: Port to connect to on the remote host.
611: This can be specified on a
612: per-host basis in the configuration file.
1.360 millert 613: .Pp
1.362 djm 614: .It Fl Q Ar query_option
1.425 jmc 615: Queries for the algorithms supported by one of the following features:
1.341 deraadt 616: .Ar cipher
1.332 djm 617: (supported symmetric ciphers),
1.341 deraadt 618: .Ar cipher-auth
1.340 djm 619: (supported symmetric ciphers that support authenticated encryption),
1.398 djm 620: .Ar help
621: (supported query terms for use with the
622: .Fl Q
623: flag),
1.341 deraadt 624: .Ar mac
1.332 djm 625: (supported message integrity codes),
1.341 deraadt 626: .Ar kex
1.332 djm 627: (key exchange algorithms),
1.341 deraadt 628: .Ar key
1.362 djm 629: (key types),
1.434 djm 630: .Ar key-ca-sign
631: (valid CA signature algorithms for certificates),
1.362 djm 632: .Ar key-cert
633: (certificate key types),
634: .Ar key-plain
1.398 djm 635: (non-certificate key types),
1.410 dtucker 636: .Ar key-sig
637: (all key types and signature algorithms),
1.356 djm 638: .Ar protocol-version
1.398 djm 639: (supported SSH protocol versions), and
640: .Ar sig
641: (supported signature algorithms).
1.410 dtucker 642: Alternatively, any keyword from
643: .Xr ssh_config 5
644: or
645: .Xr sshd_config 5
646: that takes an algorithm list may be used as an alias for the corresponding
647: query_option.
1.360 millert 648: .Pp
1.218 jmc 649: .It Fl q
650: Quiet mode.
1.271 djm 651: Causes most warning and diagnostic messages to be suppressed.
1.360 millert 652: .Pp
1.218 jmc 653: .It Fl R Xo
654: .Sm off
655: .Oo Ar bind_address : Oc
656: .Ar port : host : hostport
657: .Sm on
658: .Xc
1.360 millert 659: .It Fl R Xo
660: .Sm off
661: .Oo Ar bind_address : Oc
662: .Ar port : local_socket
663: .Sm on
664: .Xc
665: .It Fl R Xo
666: .Sm off
667: .Ar remote_socket : host : hostport
668: .Sm on
669: .Xc
670: .It Fl R Xo
671: .Sm off
672: .Ar remote_socket : local_socket
673: .Sm on
674: .Xc
1.384 markus 675: .It Fl R Xo
676: .Sm off
677: .Oo Ar bind_address : Oc
678: .Ar port
679: .Sm on
680: .Xc
1.360 millert 681: Specifies that connections to the given TCP port or Unix socket on the remote
1.384 markus 682: (server) host are to be forwarded to the local side.
683: .Pp
1.360 millert 684: This works by allocating a socket to listen to either a TCP
1.218 jmc 685: .Ar port
1.360 millert 686: or to a Unix socket on the remote side.
687: Whenever a connection is made to this port or Unix socket, the
688: connection is forwarded over the secure channel, and a connection
1.384 markus 689: is made from the local machine to either an explicit destination specified by
1.218 jmc 690: .Ar host
691: port
1.360 millert 692: .Ar hostport ,
693: or
694: .Ar local_socket ,
1.384 markus 695: or, if no explicit destination was specified,
696: .Nm
697: will act as a SOCKS 4/5 proxy and forward connections to the destinations
698: requested by the remote SOCKS client.
1.2 deraadt 699: .Pp
1.218 jmc 700: Port forwardings can also be specified in the configuration file.
701: Privileged ports can be forwarded only when
702: logging in as root on the remote machine.
1.324 jmc 703: IPv6 addresses can be specified by enclosing the address in square brackets.
1.194 jakob 704: .Pp
1.360 millert 705: By default, TCP listening sockets on the server will be bound to the loopback
1.218 jmc 706: interface only.
1.280 tobias 707: This may be overridden by specifying a
1.218 jmc 708: .Ar bind_address .
709: An empty
710: .Ar bind_address ,
711: or the address
712: .Ql * ,
713: indicates that the remote socket should listen on all interfaces.
714: Specifying a remote
715: .Ar bind_address
716: will only succeed if the server's
717: .Cm GatewayPorts
718: option is enabled (see
719: .Xr sshd_config 5 ) .
1.281 djm 720: .Pp
721: If the
722: .Ar port
723: argument is
1.282 djm 724: .Ql 0 ,
1.281 djm 725: the listen port will be dynamically allocated on the server and reported
726: to the client at run time.
1.305 markus 727: When used together with
1.430 naddy 728: .Ic -O forward ,
1.305 markus 729: the allocated port will be printed to the standard output.
1.360 millert 730: .Pp
1.218 jmc 731: .It Fl S Ar ctl_path
1.304 jmc 732: Specifies the location of a control socket for connection sharing,
1.303 djm 733: or the string
734: .Dq none
735: to disable connection sharing.
1.218 jmc 736: Refer to the description of
737: .Cm ControlPath
738: and
739: .Cm ControlMaster
740: in
741: .Xr ssh_config 5
742: for details.
1.360 millert 743: .Pp
1.218 jmc 744: .It Fl s
745: May be used to request invocation of a subsystem on the remote system.
1.369 jmc 746: Subsystems facilitate the use of SSH
747: as a secure transport for other applications (e.g.\&
1.218 jmc 748: .Xr sftp 1 ) .
749: The subsystem is specified as the remote command.
1.422 djm 750: Refer to the description of
751: .Cm SessionType
752: in
753: .Xr ssh_config 5
754: for details.
1.360 millert 755: .Pp
1.218 jmc 756: .It Fl T
1.357 dtucker 757: Disable pseudo-terminal allocation.
1.360 millert 758: .Pp
1.218 jmc 759: .It Fl t
1.357 dtucker 760: Force pseudo-terminal allocation.
1.218 jmc 761: This can be used to execute arbitrary
762: screen-based programs on a remote machine, which can be very useful,
1.257 jmc 763: e.g. when implementing menu services.
1.218 jmc 764: Multiple
765: .Fl t
766: options force tty allocation, even if
1.194 jakob 767: .Nm
1.218 jmc 768: has no local tty.
1.360 millert 769: .Pp
1.218 jmc 770: .It Fl V
771: Display the version number and exit.
1.360 millert 772: .Pp
1.218 jmc 773: .It Fl v
774: Verbose mode.
775: Causes
1.176 jmc 776: .Nm
1.218 jmc 777: to print debugging messages about its progress.
778: This is helpful in
779: debugging connection, authentication, and configuration problems.
780: Multiple
781: .Fl v
782: options increase the verbosity.
783: The maximum is 3.
1.360 millert 784: .Pp
1.290 dtucker 785: .It Fl W Ar host : Ns Ar port
786: Requests that standard input and output on the client be forwarded to
787: .Ar host
788: on
789: .Ar port
790: over the secure channel.
791: Implies
792: .Fl N ,
793: .Fl T ,
794: .Cm ExitOnForwardFailure
795: and
1.373 jmc 796: .Cm ClearAllForwardings ,
797: though these can be overridden in the configuration file or using
1.372 dtucker 798: .Fl o
799: command line options.
1.360 millert 800: .Pp
1.261 stevesk 801: .It Fl w Xo
802: .Ar local_tun Ns Op : Ns Ar remote_tun
803: .Xc
804: Requests
805: tunnel
806: device forwarding with the specified
1.218 jmc 807: .Xr tun 4
1.261 stevesk 808: devices between the client
809: .Pq Ar local_tun
810: and the server
811: .Pq Ar remote_tun .
812: .Pp
1.228 jmc 813: The devices may be specified by numerical ID or the keyword
814: .Dq any ,
815: which uses the next available tunnel device.
1.261 stevesk 816: If
817: .Ar remote_tun
818: is not specified, it defaults to
819: .Dq any .
1.228 jmc 820: See also the
1.218 jmc 821: .Cm Tunnel
1.261 stevesk 822: and
823: .Cm TunnelDevice
824: directives in
1.218 jmc 825: .Xr ssh_config 5 .
1.393 djm 826: .Pp
1.261 stevesk 827: If the
828: .Cm Tunnel
1.393 djm 829: directive is unset, it will be set to the default tunnel mode, which is
1.261 stevesk 830: .Dq point-to-point .
1.393 djm 831: If a different
832: .Cm Tunnel
833: forwarding mode it desired, then it should be specified before
834: .Fl w .
1.360 millert 835: .Pp
1.218 jmc 836: .It Fl X
837: Enables X11 forwarding.
1.54 markus 838: This can also be specified on a per-host basis in a configuration file.
1.165 stevesk 839: .Pp
1.218 jmc 840: X11 forwarding should be enabled with caution.
1.168 jmc 841: Users with the ability to bypass file permissions on the remote host
1.218 jmc 842: (for the user's X authorization database)
843: can access the local X11 display through the forwarded connection.
844: An attacker may then be able to perform activities such as keystroke monitoring.
845: .Pp
846: For this reason, X11 forwarding is subjected to X11 SECURITY extension
847: restrictions by default.
1.429 jsg 848: Refer to the
1.218 jmc 849: .Nm
850: .Fl Y
851: option and the
852: .Cm ForwardX11Trusted
853: directive in
854: .Xr ssh_config 5
855: for more information.
1.360 millert 856: .Pp
1.218 jmc 857: .It Fl x
858: Disables X11 forwarding.
1.360 millert 859: .Pp
1.218 jmc 860: .It Fl Y
861: Enables trusted X11 forwarding.
862: Trusted X11 forwardings are not subjected to the X11 SECURITY extension
863: controls.
1.360 millert 864: .Pp
1.278 djm 865: .It Fl y
866: Send log information using the
867: .Xr syslog 3
868: system module.
869: By default this information is sent to stderr.
1.218 jmc 870: .El
1.224 jmc 871: .Pp
872: .Nm
873: may additionally obtain configuration data from
874: a per-user configuration file and a system-wide configuration file.
875: The file format and configuration options are described in
876: .Xr ssh_config 5 .
1.222 jmc 877: .Sh AUTHENTICATION
1.377 djm 878: The OpenSSH SSH client supports SSH protocol 2.
1.222 jmc 879: .Pp
880: The methods available for authentication are:
1.260 jmc 881: GSSAPI-based authentication,
1.222 jmc 882: host-based authentication,
883: public key authentication,
1.421 dtucker 884: keyboard-interactive authentication,
1.222 jmc 885: and password authentication.
886: Authentication methods are tried in the order specified above,
1.369 jmc 887: though
888: .Cm PreferredAuthentications
889: can be used to change the default order.
1.222 jmc 890: .Pp
891: Host-based authentication works as follows:
1.218 jmc 892: If the machine the user logs in from is listed in
893: .Pa /etc/hosts.equiv
894: or
895: .Pa /etc/shosts.equiv
1.412 djm 896: on the remote machine, the user is non-root and the user names are
1.218 jmc 897: the same on both sides, or if the files
898: .Pa ~/.rhosts
899: or
900: .Pa ~/.shosts
901: exist in the user's home directory on the
902: remote machine and contain a line containing the name of the client
903: machine and the name of the user on that machine, the user is
1.222 jmc 904: considered for login.
905: Additionally, the server
906: .Em must
907: be able to verify the client's
908: host key (see the description of
1.218 jmc 909: .Pa /etc/ssh/ssh_known_hosts
1.189 dtucker 910: and
1.222 jmc 911: .Pa ~/.ssh/known_hosts ,
912: below)
913: for login to be permitted.
1.218 jmc 914: This authentication method closes security holes due to IP
1.222 jmc 915: spoofing, DNS spoofing, and routing spoofing.
1.218 jmc 916: [Note to the administrator:
917: .Pa /etc/hosts.equiv ,
918: .Pa ~/.rhosts ,
919: and the rlogin/rsh protocol in general, are inherently insecure and should be
920: disabled if security is desired.]
1.189 dtucker 921: .Pp
1.222 jmc 922: Public key authentication works as follows:
923: The scheme is based on public-key cryptography,
924: using cryptosystems
925: where encryption and decryption are done using separate keys,
926: and it is unfeasible to derive the decryption key from the encryption key.
1.218 jmc 927: The idea is that each user creates a public/private
928: key pair for authentication purposes.
929: The server knows the public key, and only the user knows the private key.
1.222 jmc 930: .Nm
931: implements public key authentication protocol automatically,
1.349 sobrado 932: using one of the DSA, ECDSA, Ed25519 or RSA algorithms.
1.333 jmc 933: The HISTORY section of
1.222 jmc 934: .Xr ssl 8
1.311 jmc 935: contains a brief discussion of the DSA and RSA algorithms.
1.210 djm 936: .Pp
1.218 jmc 937: The file
938: .Pa ~/.ssh/authorized_keys
939: lists the public keys that are permitted for logging in.
940: When the user logs in, the
1.2 deraadt 941: .Nm
1.218 jmc 942: program tells the server which key pair it would like to use for
943: authentication.
1.222 jmc 944: The client proves that it has access to the private key
945: and the server checks that the corresponding public key
946: is authorized to accept the account.
1.383 djm 947: .Pp
948: The server may inform the client of errors that prevented public key
949: authentication from succeeding after authentication completes using a
950: different method.
951: These may be viewed by increasing the
952: .Cm LogLevel
953: to
954: .Cm DEBUG
955: or higher (e.g. by using the
956: .Fl v
957: flag).
1.218 jmc 958: .Pp
1.420 dtucker 959: The user creates their key pair by running
1.218 jmc 960: .Xr ssh-keygen 1 .
961: This stores the private key in
1.222 jmc 962: .Pa ~/.ssh/id_dsa
1.369 jmc 963: (DSA),
1.310 djm 964: .Pa ~/.ssh/id_ecdsa
1.369 jmc 965: (ECDSA),
1.404 naddy 966: .Pa ~/.ssh/id_ecdsa_sk
1.409 naddy 967: (authenticator-hosted ECDSA),
1.343 naddy 968: .Pa ~/.ssh/id_ed25519
1.369 jmc 969: (Ed25519),
1.406 naddy 970: .Pa ~/.ssh/id_ed25519_sk
1.409 naddy 971: (authenticator-hosted Ed25519),
1.222 jmc 972: or
973: .Pa ~/.ssh/id_rsa
1.369 jmc 974: (RSA)
1.218 jmc 975: and stores the public key in
1.222 jmc 976: .Pa ~/.ssh/id_dsa.pub
1.369 jmc 977: (DSA),
1.310 djm 978: .Pa ~/.ssh/id_ecdsa.pub
1.369 jmc 979: (ECDSA),
1.404 naddy 980: .Pa ~/.ssh/id_ecdsa_sk.pub
1.409 naddy 981: (authenticator-hosted ECDSA),
1.343 naddy 982: .Pa ~/.ssh/id_ed25519.pub
1.369 jmc 983: (Ed25519),
1.406 naddy 984: .Pa ~/.ssh/id_ed25519_sk.pub
1.409 naddy 985: (authenticator-hosted Ed25519),
1.222 jmc 986: or
987: .Pa ~/.ssh/id_rsa.pub
1.369 jmc 988: (RSA)
1.218 jmc 989: in the user's home directory.
1.222 jmc 990: The user should then copy the public key
1.218 jmc 991: to
992: .Pa ~/.ssh/authorized_keys
1.420 dtucker 993: in their home directory on the remote machine.
1.222 jmc 994: The
1.218 jmc 995: .Pa authorized_keys
996: file corresponds to the conventional
997: .Pa ~/.rhosts
998: file, and has one key
1.222 jmc 999: per line, though the lines can be very long.
1.218 jmc 1000: After this, the user can log in without giving the password.
1001: .Pp
1.301 jmc 1002: A variation on public key authentication
1003: is available in the form of certificate authentication:
1004: instead of a set of public/private keys,
1005: signed certificates are used.
1006: This has the advantage that a single trusted certification authority
1007: can be used in place of many public/private keys.
1.333 jmc 1008: See the CERTIFICATES section of
1.301 jmc 1009: .Xr ssh-keygen 1
1010: for more information.
1011: .Pp
1012: The most convenient way to use public key or certificate authentication
1013: may be with an authentication agent.
1.218 jmc 1014: See
1015: .Xr ssh-agent 1
1.366 jcs 1016: and (optionally) the
1017: .Cm AddKeysToAgent
1018: directive in
1019: .Xr ssh_config 5
1.218 jmc 1020: for more information.
1021: .Pp
1.421 dtucker 1022: Keyboard-interactive authentication works as follows:
1.222 jmc 1023: The server sends an arbitrary
1024: .Qq challenge
1.421 dtucker 1025: text and prompts for a response, possibly multiple times.
1026: Examples of keyboard-interactive authentication include
1.335 jmc 1027: .Bx
1028: Authentication (see
1.222 jmc 1029: .Xr login.conf 5 )
1.335 jmc 1030: and PAM (some
1031: .Pf non- Ox
1032: systems).
1.222 jmc 1033: .Pp
1034: Finally, if other authentication methods fail,
1.218 jmc 1035: .Nm
1036: prompts the user for a password.
1037: The password is sent to the remote
1038: host for checking; however, since all communications are encrypted,
1039: the password cannot be seen by someone listening on the network.
1.232 jmc 1040: .Pp
1041: .Nm
1042: automatically maintains and checks a database containing
1043: identification for all hosts it has ever been used with.
1044: Host keys are stored in
1045: .Pa ~/.ssh/known_hosts
1046: in the user's home directory.
1047: Additionally, the file
1048: .Pa /etc/ssh/ssh_known_hosts
1049: is automatically checked for known hosts.
1050: Any new hosts are automatically added to the user's file.
1051: If a host's identification ever changes,
1052: .Nm
1053: warns about this and disables password authentication to prevent
1054: server spoofing or man-in-the-middle attacks,
1055: which could otherwise be used to circumvent the encryption.
1056: The
1057: .Cm StrictHostKeyChecking
1058: option can be used to control logins to machines whose
1059: host key is not known or has changed.
1060: .Pp
1.218 jmc 1061: When the user's identity has been accepted by the server, the server
1.357 dtucker 1062: either executes the given command in a non-interactive session or,
1063: if no command has been specified, logs into the machine and gives
1064: the user a normal shell as an interactive session.
1.218 jmc 1065: All communication with
1066: the remote command or shell will be automatically encrypted.
1067: .Pp
1.430 naddy 1068: If an interactive session is requested,
1.357 dtucker 1069: .Nm
1070: by default will only request a pseudo-terminal (pty) for interactive
1071: sessions when the client has one.
1072: The flags
1073: .Fl T
1074: and
1075: .Fl t
1076: can be used to override this behaviour.
1077: .Pp
1.430 naddy 1078: If a pseudo-terminal has been allocated, the
1.218 jmc 1079: user may use the escape characters noted below.
1080: .Pp
1.357 dtucker 1081: If no pseudo-terminal has been allocated,
1.218 jmc 1082: the session is transparent and can be used to reliably transfer binary data.
1083: On most systems, setting the escape character to
1084: .Dq none
1085: will also make the session transparent even if a tty is used.
1086: .Pp
1087: The session terminates when the command or shell on the remote
1.247 jmc 1088: machine exits and all X11 and TCP connections have been closed.
1.223 jmc 1089: .Sh ESCAPE CHARACTERS
1.218 jmc 1090: When a pseudo-terminal has been requested,
1.2 deraadt 1091: .Nm
1.218 jmc 1092: supports a number of functions through the use of an escape character.
1093: .Pp
1094: A single tilde character can be sent as
1095: .Ic ~~
1096: or by following the tilde by a character other than those described below.
1097: The escape character must always follow a newline to be interpreted as
1098: special.
1099: The escape character can be changed in configuration files using the
1100: .Cm EscapeChar
1101: configuration directive or on the command line by the
1102: .Fl e
1103: option.
1104: .Pp
1105: The supported escapes (assuming the default
1106: .Ql ~ )
1107: are:
1108: .Bl -tag -width Ds
1109: .It Cm ~.
1110: Disconnect.
1111: .It Cm ~^Z
1112: Background
1.234 jmc 1113: .Nm .
1.218 jmc 1114: .It Cm ~#
1115: List forwarded connections.
1116: .It Cm ~&
1117: Background
1.2 deraadt 1118: .Nm
1.218 jmc 1119: at logout when waiting for forwarded connection / X11 sessions to terminate.
1120: .It Cm ~?
1121: Display a list of escape characters.
1122: .It Cm ~B
1123: Send a BREAK to the remote system
1.369 jmc 1124: (only useful if the peer supports it).
1.218 jmc 1125: .It Cm ~C
1126: Open command line.
1127: Currently this allows the addition of port forwardings using the
1.279 stevesk 1128: .Fl L ,
1129: .Fl R
1.218 jmc 1130: and
1.279 stevesk 1131: .Fl D
1.225 jmc 1132: options (see above).
1.322 markus 1133: It also allows the cancellation of existing port-forwardings
1134: with
1.262 stevesk 1135: .Sm off
1.322 markus 1136: .Fl KL Oo Ar bind_address : Oc Ar port
1.262 stevesk 1137: .Sm on
1.322 markus 1138: for local,
1139: .Sm off
1140: .Fl KR Oo Ar bind_address : Oc Ar port
1141: .Sm on
1142: for remote and
1143: .Sm off
1144: .Fl KD Oo Ar bind_address : Oc Ar port
1145: .Sm on
1146: for dynamic port-forwardings.
1.218 jmc 1147: .Ic !\& Ns Ar command
1148: allows the user to execute a local command if the
1149: .Ic PermitLocalCommand
1150: option is enabled in
1.176 jmc 1151: .Xr ssh_config 5 .
1.218 jmc 1152: Basic help is available, using the
1153: .Fl h
1154: option.
1155: .It Cm ~R
1156: Request rekeying of the connection
1.369 jmc 1157: (only useful if the peer supports it).
1.327 dtucker 1158: .It Cm ~V
1159: Decrease the verbosity
1160: .Pq Ic LogLevel
1161: when errors are being written to stderr.
1162: .It Cm ~v
1.328 jmc 1163: Increase the verbosity
1.327 dtucker 1164: .Pq Ic LogLevel
1165: when errors are being written to stderr.
1.176 jmc 1166: .El
1.246 jmc 1167: .Sh TCP FORWARDING
1.402 jmc 1168: Forwarding of arbitrary TCP connections over a secure channel
1169: can be specified either on the command line or in a configuration file.
1.246 jmc 1170: One possible application of TCP forwarding is a secure connection to a
1171: mail server; another is going through firewalls.
1172: .Pp
1.402 jmc 1173: In the example below, we look at encrypting communication for an IRC client,
1174: even though the IRC server it connects to does not directly
1175: support encrypted communication.
1.246 jmc 1176: This works as follows:
1177: the user connects to the remote host using
1178: .Nm ,
1.402 jmc 1179: specifying the ports to be used to forward the connection.
1180: After that it is possible to start the program locally,
1.246 jmc 1181: and
1182: .Nm
1.402 jmc 1183: will encrypt and forward the connection to the remote server.
1.246 jmc 1184: .Pp
1.402 jmc 1185: The following example tunnels an IRC session from the client
1186: to an IRC server at
1.246 jmc 1187: .Dq server.example.com ,
1188: joining channel
1189: .Dq #users ,
1190: nickname
1191: .Dq pinky ,
1.402 jmc 1192: using the standard IRC port, 6667:
1193: .Bd -literal -offset 4n
1194: $ ssh -f -L 6667:localhost:6667 server.example.com sleep 10
1195: $ irc -c '#users' pinky IRC/127.0.0.1
1196: .Ed
1.246 jmc 1197: .Pp
1198: The
1199: .Fl f
1200: option backgrounds
1201: .Nm
1202: and the remote command
1203: .Dq sleep 10
1204: is specified to allow an amount of time
1205: (10 seconds, in the example)
1.402 jmc 1206: to start the program which is going to use the tunnel.
1.246 jmc 1207: If no connections are made within the time specified,
1208: .Nm
1209: will exit.
1210: .Sh X11 FORWARDING
1.218 jmc 1211: If the
1212: .Cm ForwardX11
1213: variable is set to
1214: .Dq yes
1215: (or see the description of the
1.227 jmc 1216: .Fl X ,
1217: .Fl x ,
1.218 jmc 1218: and
1.227 jmc 1219: .Fl Y
1.226 jmc 1220: options above)
1.218 jmc 1221: and the user is using X11 (the
1222: .Ev DISPLAY
1223: environment variable is set), the connection to the X11 display is
1224: automatically forwarded to the remote side in such a way that any X11
1225: programs started from the shell (or command) will go through the
1226: encrypted channel, and the connection to the real X server will be made
1.176 jmc 1227: from the local machine.
1.218 jmc 1228: The user should not manually set
1229: .Ev DISPLAY .
1230: Forwarding of X11 connections can be
1231: configured on the command line or in configuration files.
1232: .Pp
1233: The
1234: .Ev DISPLAY
1235: value set by
1236: .Nm
1237: will point to the server machine, but with a display number greater than zero.
1238: This is normal, and happens because
1239: .Nm
1240: creates a
1241: .Dq proxy
1242: X server on the server machine for forwarding the
1243: connections over the encrypted channel.
1.200 djm 1244: .Pp
1.218 jmc 1245: .Nm
1246: will also automatically set up Xauthority data on the server machine.
1247: For this purpose, it will generate a random authorization cookie,
1248: store it in Xauthority on the server, and verify that any forwarded
1249: connections carry this cookie and replace it by the real cookie when
1250: the connection is opened.
1251: The real authentication cookie is never
1252: sent to the server machine (and no cookies are sent in the plain).
1.200 djm 1253: .Pp
1.218 jmc 1254: If the
1255: .Cm ForwardAgent
1256: variable is set to
1257: .Dq yes
1258: (or see the description of the
1259: .Fl A
1.191 djm 1260: and
1.218 jmc 1261: .Fl a
1.226 jmc 1262: options above) and
1.218 jmc 1263: the user is using an authentication agent, the connection to the agent
1264: is automatically forwarded to the remote side.
1.252 jmc 1265: .Sh VERIFYING HOST KEYS
1266: When connecting to a server for the first time,
1267: a fingerprint of the server's public key is presented to the user
1268: (unless the option
1269: .Cm StrictHostKeyChecking
1270: has been disabled).
1271: Fingerprints can be determined using
1272: .Xr ssh-keygen 1 :
1273: .Pp
1274: .Dl $ ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key
1275: .Pp
1.274 grunk 1276: If the fingerprint is already known, it can be matched
1277: and the key can be accepted or rejected.
1.358 djm 1278: If only legacy (MD5) fingerprints for the server are available, the
1279: .Xr ssh-keygen 1
1280: .Fl E
1281: option may be used to downgrade the fingerprint algorithm to match.
1282: .Pp
1.274 grunk 1283: Because of the difficulty of comparing host keys
1.352 djm 1284: just by looking at fingerprint strings,
1.274 grunk 1285: there is also support to compare host keys visually,
1286: using
1287: .Em random art .
1288: By setting the
1.275 grunk 1289: .Cm VisualHostKey
1.274 grunk 1290: option to
1.275 grunk 1291: .Dq yes ,
1.274 grunk 1292: a small ASCII graphic gets displayed on every login to a server, no matter
1293: if the session itself is interactive or not.
1294: By learning the pattern a known server produces, a user can easily
1295: find out that the host key has changed when a completely different pattern
1296: is displayed.
1297: Because these patterns are not unambiguous however, a pattern that looks
1298: similar to the pattern remembered only gives a good probability that the
1299: host key is the same, not guaranteed proof.
1300: .Pp
1301: To get a listing of the fingerprints along with their random art for
1302: all known hosts, the following command line can be used:
1303: .Pp
1304: .Dl $ ssh-keygen -lv -f ~/.ssh/known_hosts
1305: .Pp
1.252 jmc 1306: If the fingerprint is unknown,
1307: an alternative method of verification is available:
1308: SSH fingerprints verified by DNS.
1309: An additional resource record (RR),
1310: SSHFP,
1311: is added to a zonefile
1312: and the connecting client is able to match the fingerprint
1313: with that of the key presented.
1314: .Pp
1315: In this example, we are connecting a client to a server,
1316: .Dq host.example.com .
1317: The SSHFP resource records should first be added to the zonefile for
1318: host.example.com:
1319: .Bd -literal -offset indent
1.259 jakob 1320: $ ssh-keygen -r host.example.com.
1.252 jmc 1321: .Ed
1322: .Pp
1323: The output lines will have to be added to the zonefile.
1324: To check that the zone is answering fingerprint queries:
1325: .Pp
1326: .Dl $ dig -t SSHFP host.example.com
1327: .Pp
1328: Finally the client connects:
1329: .Bd -literal -offset indent
1330: $ ssh -o "VerifyHostKeyDNS ask" host.example.com
1331: [...]
1332: Matching host key fingerprint found in DNS.
1333: Are you sure you want to continue connecting (yes/no)?
1334: .Ed
1335: .Pp
1336: See the
1337: .Cm VerifyHostKeyDNS
1338: option in
1339: .Xr ssh_config 5
1340: for more information.
1.250 jmc 1341: .Sh SSH-BASED VIRTUAL PRIVATE NETWORKS
1342: .Nm
1343: contains support for Virtual Private Network (VPN) tunnelling
1344: using the
1345: .Xr tun 4
1346: network pseudo-device,
1347: allowing two networks to be joined securely.
1348: The
1349: .Xr sshd_config 5
1350: configuration option
1351: .Cm PermitTunnel
1352: controls whether the server supports this,
1353: and at what level (layer 2 or 3 traffic).
1354: .Pp
1355: The following example would connect client network 10.0.50.0/24
1.265 otto 1356: with remote network 10.0.99.0/24 using a point-to-point connection
1357: from 10.1.1.1 to 10.1.1.2,
1358: provided that the SSH server running on the gateway to the remote network,
1359: at 192.168.1.15, allows it.
1360: .Pp
1361: On the client:
1.250 jmc 1362: .Bd -literal -offset indent
1363: # ssh -f -w 0:1 192.168.1.15 true
1.265 otto 1364: # ifconfig tun0 10.1.1.1 10.1.1.2 netmask 255.255.255.252
1365: # route add 10.0.99.0/24 10.1.1.2
1366: .Ed
1367: .Pp
1368: On the server:
1369: .Bd -literal -offset indent
1370: # ifconfig tun1 10.1.1.2 10.1.1.1 netmask 255.255.255.252
1371: # route add 10.0.50.0/24 10.1.1.1
1.250 jmc 1372: .Ed
1373: .Pp
1374: Client access may be more finely tuned via the
1375: .Pa /root/.ssh/authorized_keys
1376: file (see below) and the
1377: .Cm PermitRootLogin
1378: server option.
1.255 jmc 1379: The following entry would permit connections on
1.250 jmc 1380: .Xr tun 4
1.255 jmc 1381: device 1 from user
1.250 jmc 1382: .Dq jane
1.255 jmc 1383: and on tun device 2 from user
1.250 jmc 1384: .Dq john ,
1385: if
1386: .Cm PermitRootLogin
1387: is set to
1388: .Dq forced-commands-only :
1389: .Bd -literal -offset 2n
1390: tunnel="1",command="sh /etc/netstart tun1" ssh-rsa ... jane
1.254 msf 1391: tunnel="2",command="sh /etc/netstart tun2" ssh-rsa ... john
1.250 jmc 1392: .Ed
1393: .Pp
1.264 ray 1394: Since an SSH-based setup entails a fair amount of overhead,
1.250 jmc 1395: it may be more suited to temporary setups,
1396: such as for wireless VPNs.
1397: More permanent VPNs are better provided by tools such as
1398: .Xr ipsecctl 8
1399: and
1400: .Xr isakmpd 8 .
1.2 deraadt 1401: .Sh ENVIRONMENT
1402: .Nm
1.1 deraadt 1403: will normally set the following environment variables:
1.237 jmc 1404: .Bl -tag -width "SSH_ORIGINAL_COMMAND"
1.2 deraadt 1405: .It Ev DISPLAY
1406: The
1407: .Ev DISPLAY
1.40 aaron 1408: variable indicates the location of the X11 server.
1.44 aaron 1409: It is automatically set by
1.2 deraadt 1410: .Nm
1411: to point to a value of the form
1.233 jmc 1412: .Dq hostname:n ,
1413: where
1414: .Dq hostname
1415: indicates the host where the shell runs, and
1416: .Sq n
1417: is an integer \*(Ge 1.
1.40 aaron 1418: .Nm
1419: uses this special value to forward X11 connections over the secure
1420: channel.
1.107 markus 1421: The user should normally not set
1422: .Ev DISPLAY
1423: explicitly, as that
1.1 deraadt 1424: will render the X11 connection insecure (and will require the user to
1425: manually copy any required authorization cookies).
1.2 deraadt 1426: .It Ev HOME
1.1 deraadt 1427: Set to the path of the user's home directory.
1.2 deraadt 1428: .It Ev LOGNAME
1429: Synonym for
1.12 aaron 1430: .Ev USER ;
1431: set for compatibility with systems that use this variable.
1.2 deraadt 1432: .It Ev MAIL
1.129 stevesk 1433: Set to the path of the user's mailbox.
1.40 aaron 1434: .It Ev PATH
1.2 deraadt 1435: Set to the default
1436: .Ev PATH ,
1437: as specified when compiling
1.234 jmc 1438: .Nm .
1.118 markus 1439: .It Ev SSH_ASKPASS
1440: If
1441: .Nm
1442: needs a passphrase, it will read the passphrase from the current
1443: terminal if it was run from a terminal.
1444: If
1445: .Nm
1446: does not have a terminal associated with it but
1447: .Ev DISPLAY
1448: and
1449: .Ev SSH_ASKPASS
1450: are set, it will execute the program specified by
1451: .Ev SSH_ASKPASS
1452: and open an X11 window to read the passphrase.
1453: This is particularly useful when calling
1454: .Nm
1455: from a
1.196 jmc 1456: .Pa .xsession
1.118 markus 1457: or related script.
1458: (Note that on some machines it
1459: may be necessary to redirect the input from
1460: .Pa /dev/null
1461: to make this work.)
1.413 djm 1462: .It Ev SSH_ASKPASS_REQUIRE
1.414 jmc 1463: Allows further control over the use of an askpass program.
1.413 djm 1464: If this variable is set to
1465: .Dq never
1466: then
1467: .Nm
1468: will never attempt to use one.
1469: If it is set to
1470: .Dq prefer ,
1471: then
1472: .Nm
1473: will prefer to use the askpass program instead of the TTY when requesting
1474: passwords.
1475: Finally, if the variable is set to
1476: .Dq force ,
1477: then the askpass program will be used for all passphrase input regardless
1478: of whether
1479: .Ev DISPLAY
1480: is set.
1.18 markus 1481: .It Ev SSH_AUTH_SOCK
1.233 jmc 1482: Identifies the path of a
1483: .Ux Ns -domain
1484: socket used to communicate with the agent.
1.166 stevesk 1485: .It Ev SSH_CONNECTION
1486: Identifies the client and server ends of the connection.
1.40 aaron 1487: The variable contains
1.233 jmc 1488: four space-separated values: client IP address, client port number,
1489: server IP address, and server port number.
1.73 markus 1490: .It Ev SSH_ORIGINAL_COMMAND
1.233 jmc 1491: This variable contains the original command line if a forced command
1.73 markus 1492: is executed.
1493: It can be used to extract the original arguments.
1.2 deraadt 1494: .It Ev SSH_TTY
1.1 deraadt 1495: This is set to the name of the tty (path to the device) associated
1.40 aaron 1496: with the current shell or command.
1497: If the current session has no tty,
1.1 deraadt 1498: this variable is not set.
1.387 djm 1499: .It Ev SSH_TUNNEL
1500: Optionally set by
1501: .Xr sshd 8
1502: to contain the interface names assigned if tunnel forwarding was
1503: requested by the client.
1.385 djm 1504: .It Ev SSH_USER_AUTH
1505: Optionally set by
1506: .Xr sshd 8 ,
1507: this variable may contain a pathname to a file that lists the authentication
1508: methods successfully used when the session was established, including any
1509: public keys that were used.
1.2 deraadt 1510: .It Ev TZ
1.214 jmc 1511: This variable is set to indicate the present time zone if it
1.257 jmc 1512: was set when the daemon was started (i.e. the daemon passes the value
1.1 deraadt 1513: on to new connections).
1.2 deraadt 1514: .It Ev USER
1.1 deraadt 1515: Set to the name of the user logging in.
1.2 deraadt 1516: .El
1517: .Pp
1.44 aaron 1518: Additionally,
1.2 deraadt 1519: .Nm
1.44 aaron 1520: reads
1.207 djm 1521: .Pa ~/.ssh/environment ,
1.2 deraadt 1522: and adds lines of the format
1523: .Dq VARNAME=value
1.233 jmc 1524: to the environment if the file exists and users are allowed to
1.161 marc 1525: change their environment.
1.176 jmc 1526: For more information, see the
1.161 marc 1527: .Cm PermitUserEnvironment
1.162 stevesk 1528: option in
1.161 marc 1529: .Xr sshd_config 5 .
1.2 deraadt 1530: .Sh FILES
1.236 jmc 1531: .Bl -tag -width Ds -compact
1.309 jmc 1532: .It Pa ~/.rhosts
1.240 jmc 1533: This file is used for host-based authentication (see above).
1.92 markus 1534: On some machines this file may need to be
1.240 jmc 1535: world-readable if the user's home directory is on an NFS partition,
1.1 deraadt 1536: because
1.2 deraadt 1537: .Xr sshd 8
1.40 aaron 1538: reads it as root.
1539: Additionally, this file must be owned by the user,
1540: and must not have write permissions for anyone else.
1541: The recommended
1.1 deraadt 1542: permission for most machines is read/write for the user, and not
1543: accessible by others.
1.2 deraadt 1544: .Pp
1.309 jmc 1545: .It Pa ~/.shosts
1.240 jmc 1546: This file is used in exactly the same way as
1547: .Pa .rhosts ,
1548: but allows host-based authentication without permitting login with
1549: rlogin/rsh.
1.272 mcbride 1550: .Pp
1.309 jmc 1551: .It Pa ~/.ssh/
1.272 mcbride 1552: This directory is the default location for all user-specific configuration
1553: and authentication information.
1554: There is no general requirement to keep the entire contents of this directory
1555: secret, but the recommended permissions are read/write/execute for the user,
1556: and not accessible by others.
1.236 jmc 1557: .Pp
1.309 jmc 1558: .It Pa ~/.ssh/authorized_keys
1.349 sobrado 1559: Lists the public keys (DSA, ECDSA, Ed25519, RSA)
1.343 naddy 1560: that can be used for logging in as this user.
1.238 jmc 1561: The format of this file is described in the
1562: .Xr sshd 8
1563: manual page.
1564: This file is not highly sensitive, but the recommended
1565: permissions are read/write for the user, and not accessible by others.
1566: .Pp
1.309 jmc 1567: .It Pa ~/.ssh/config
1.238 jmc 1568: This is the per-user configuration file.
1569: The file format and configuration options are described in
1570: .Xr ssh_config 5 .
1571: Because of the potential for abuse, this file must have strict permissions:
1.334 djm 1572: read/write for the user, and not writable by others.
1.238 jmc 1573: .Pp
1.309 jmc 1574: .It Pa ~/.ssh/environment
1.239 jmc 1575: Contains additional definitions for environment variables; see
1576: .Sx ENVIRONMENT ,
1.238 jmc 1577: above.
1578: .Pp
1.309 jmc 1579: .It Pa ~/.ssh/id_dsa
1.310 djm 1580: .It Pa ~/.ssh/id_ecdsa
1.404 naddy 1581: .It Pa ~/.ssh/id_ecdsa_sk
1.343 naddy 1582: .It Pa ~/.ssh/id_ed25519
1.406 naddy 1583: .It Pa ~/.ssh/id_ed25519_sk
1.309 jmc 1584: .It Pa ~/.ssh/id_rsa
1.238 jmc 1585: Contains the private key for authentication.
1586: These files
1587: contain sensitive data and should be readable by the user but not
1588: accessible by others (read/write/execute).
1589: .Nm
1590: will simply ignore a private key file if it is accessible by others.
1591: It is possible to specify a passphrase when
1592: generating the key which will be used to encrypt the
1.389 djm 1593: sensitive part of this file using AES-128.
1.238 jmc 1594: .Pp
1.309 jmc 1595: .It Pa ~/.ssh/id_dsa.pub
1.310 djm 1596: .It Pa ~/.ssh/id_ecdsa.pub
1.404 naddy 1597: .It Pa ~/.ssh/id_ecdsa_sk.pub
1.343 naddy 1598: .It Pa ~/.ssh/id_ed25519.pub
1.406 naddy 1599: .It Pa ~/.ssh/id_ed25519_sk.pub
1.309 jmc 1600: .It Pa ~/.ssh/id_rsa.pub
1.238 jmc 1601: Contains the public key for authentication.
1602: These files are not
1603: sensitive and can (but need not) be readable by anyone.
1604: .Pp
1.309 jmc 1605: .It Pa ~/.ssh/known_hosts
1.244 jmc 1606: Contains a list of host keys for all hosts the user has logged into
1607: that are not already in the systemwide list of known host keys.
1.238 jmc 1608: See
1.244 jmc 1609: .Xr sshd 8
1610: for further details of the format of this file.
1.238 jmc 1611: .Pp
1.309 jmc 1612: .It Pa ~/.ssh/rc
1.238 jmc 1613: Commands in this file are executed by
1614: .Nm
1.245 jmc 1615: when the user logs in, just before the user's shell (or command) is
1.238 jmc 1616: started.
1617: See the
1618: .Xr sshd 8
1619: manual page for more information.
1620: .Pp
1.309 jmc 1621: .It Pa /etc/hosts.equiv
1.240 jmc 1622: This file is for host-based authentication (see above).
1623: It should only be writable by root.
1.236 jmc 1624: .Pp
1.309 jmc 1625: .It Pa /etc/shosts.equiv
1.240 jmc 1626: This file is used in exactly the same way as
1627: .Pa hosts.equiv ,
1628: but allows host-based authentication without permitting login with
1629: rlogin/rsh.
1.236 jmc 1630: .Pp
1.238 jmc 1631: .It Pa /etc/ssh/ssh_config
1632: Systemwide configuration file.
1633: The file format and configuration options are described in
1634: .Xr ssh_config 5 .
1635: .Pp
1.309 jmc 1636: .It Pa /etc/ssh/ssh_host_key
1637: .It Pa /etc/ssh/ssh_host_dsa_key
1.310 djm 1638: .It Pa /etc/ssh/ssh_host_ecdsa_key
1.343 naddy 1639: .It Pa /etc/ssh/ssh_host_ed25519_key
1.309 jmc 1640: .It Pa /etc/ssh/ssh_host_rsa_key
1.325 dtucker 1641: These files contain the private parts of the host keys
1.245 jmc 1642: and are used for host-based authentication.
1.238 jmc 1643: .Pp
1.309 jmc 1644: .It Pa /etc/ssh/ssh_known_hosts
1.238 jmc 1645: Systemwide list of known host keys.
1646: This file should be prepared by the
1647: system administrator to contain the public host keys of all machines in the
1648: organization.
1.244 jmc 1649: It should be world-readable.
1650: See
1.238 jmc 1651: .Xr sshd 8
1.244 jmc 1652: for further details of the format of this file.
1.236 jmc 1653: .Pp
1.309 jmc 1654: .It Pa /etc/ssh/sshrc
1.1 deraadt 1655: Commands in this file are executed by
1.2 deraadt 1656: .Nm
1.245 jmc 1657: when the user logs in, just before the user's shell (or command) is started.
1.44 aaron 1658: See the
1.2 deraadt 1659: .Xr sshd 8
1.1 deraadt 1660: manual page for more information.
1.58 itojun 1661: .El
1.312 jmc 1662: .Sh EXIT STATUS
1663: .Nm
1664: exits with the exit status of the remote command or with 255
1665: if an error occurred.
1.2 deraadt 1666: .Sh SEE ALSO
1667: .Xr scp 1 ,
1.83 djm 1668: .Xr sftp 1 ,
1.2 deraadt 1669: .Xr ssh-add 1 ,
1670: .Xr ssh-agent 1 ,
1671: .Xr ssh-keygen 1 ,
1.242 jmc 1672: .Xr ssh-keyscan 1 ,
1.250 jmc 1673: .Xr tun 4 ,
1.159 stevesk 1674: .Xr ssh_config 5 ,
1.160 naddy 1675: .Xr ssh-keysign 8 ,
1.87 itojun 1676: .Xr sshd 8
1.329 jmc 1677: .Sh STANDARDS
1.106 markus 1678: .Rs
1.329 jmc 1679: .%A S. Lehtinen
1680: .%A C. Lonvick
1681: .%D January 2006
1.256 jmc 1682: .%R RFC 4250
1.329 jmc 1683: .%T The Secure Shell (SSH) Protocol Assigned Numbers
1.256 jmc 1684: .Re
1.329 jmc 1685: .Pp
1.256 jmc 1686: .Rs
1.329 jmc 1687: .%A T. Ylonen
1688: .%A C. Lonvick
1689: .%D January 2006
1.256 jmc 1690: .%R RFC 4251
1.329 jmc 1691: .%T The Secure Shell (SSH) Protocol Architecture
1.256 jmc 1692: .Re
1.329 jmc 1693: .Pp
1.256 jmc 1694: .Rs
1.329 jmc 1695: .%A T. Ylonen
1696: .%A C. Lonvick
1697: .%D January 2006
1.256 jmc 1698: .%R RFC 4252
1.329 jmc 1699: .%T The Secure Shell (SSH) Authentication Protocol
1.256 jmc 1700: .Re
1.329 jmc 1701: .Pp
1.256 jmc 1702: .Rs
1.329 jmc 1703: .%A T. Ylonen
1704: .%A C. Lonvick
1705: .%D January 2006
1.256 jmc 1706: .%R RFC 4253
1.329 jmc 1707: .%T The Secure Shell (SSH) Transport Layer Protocol
1.256 jmc 1708: .Re
1.329 jmc 1709: .Pp
1.256 jmc 1710: .Rs
1.329 jmc 1711: .%A T. Ylonen
1712: .%A C. Lonvick
1713: .%D January 2006
1.256 jmc 1714: .%R RFC 4254
1.329 jmc 1715: .%T The Secure Shell (SSH) Connection Protocol
1.256 jmc 1716: .Re
1.329 jmc 1717: .Pp
1.256 jmc 1718: .Rs
1.329 jmc 1719: .%A J. Schlyter
1720: .%A W. Griffin
1721: .%D January 2006
1.256 jmc 1722: .%R RFC 4255
1.329 jmc 1723: .%T Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints
1.256 jmc 1724: .Re
1.329 jmc 1725: .Pp
1.256 jmc 1726: .Rs
1.329 jmc 1727: .%A F. Cusack
1728: .%A M. Forssen
1729: .%D January 2006
1.256 jmc 1730: .%R RFC 4256
1.329 jmc 1731: .%T Generic Message Exchange Authentication for the Secure Shell Protocol (SSH)
1.256 jmc 1732: .Re
1.329 jmc 1733: .Pp
1.256 jmc 1734: .Rs
1.329 jmc 1735: .%A J. Galbraith
1736: .%A P. Remaker
1737: .%D January 2006
1.256 jmc 1738: .%R RFC 4335
1.329 jmc 1739: .%T The Secure Shell (SSH) Session Channel Break Extension
1.256 jmc 1740: .Re
1.329 jmc 1741: .Pp
1.256 jmc 1742: .Rs
1.329 jmc 1743: .%A M. Bellare
1744: .%A T. Kohno
1745: .%A C. Namprempre
1746: .%D January 2006
1.256 jmc 1747: .%R RFC 4344
1.329 jmc 1748: .%T The Secure Shell (SSH) Transport Layer Encryption Modes
1.256 jmc 1749: .Re
1.329 jmc 1750: .Pp
1.256 jmc 1751: .Rs
1.329 jmc 1752: .%A B. Harris
1753: .%D January 2006
1.256 jmc 1754: .%R RFC 4345
1.329 jmc 1755: .%T Improved Arcfour Modes for the Secure Shell (SSH) Transport Layer Protocol
1.258 djm 1756: .Re
1.329 jmc 1757: .Pp
1.258 djm 1758: .Rs
1.329 jmc 1759: .%A M. Friedl
1760: .%A N. Provos
1761: .%A W. Simpson
1762: .%D March 2006
1.258 djm 1763: .%R RFC 4419
1.329 jmc 1764: .%T Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol
1.266 markus 1765: .Re
1.329 jmc 1766: .Pp
1.266 markus 1767: .Rs
1.329 jmc 1768: .%A J. Galbraith
1769: .%A R. Thayer
1770: .%D November 2006
1.266 markus 1771: .%R RFC 4716
1.329 jmc 1772: .%T The Secure Shell (SSH) Public Key File Format
1.313 djm 1773: .Re
1.329 jmc 1774: .Pp
1.313 djm 1775: .Rs
1.329 jmc 1776: .%A D. Stebila
1777: .%A J. Green
1778: .%D December 2009
1.313 djm 1779: .%R RFC 5656
1.329 jmc 1780: .%T Elliptic Curve Algorithm Integration in the Secure Shell Transport Layer
1.274 grunk 1781: .Re
1.329 jmc 1782: .Pp
1.274 grunk 1783: .Rs
1784: .%A A. Perrig
1785: .%A D. Song
1786: .%D 1999
1.329 jmc 1787: .%O International Workshop on Cryptographic Techniques and E-Commerce (CrypTEC '99)
1788: .%T Hash Visualization: a New Technique to improve Real-World Security
1.106 markus 1789: .Re
1.173 jmc 1790: .Sh AUTHORS
1791: OpenSSH is a derivative of the original and free
1792: ssh 1.2.12 release by Tatu Ylonen.
1793: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1794: Theo de Raadt and Dug Song
1795: removed many bugs, re-added newer features and
1796: created OpenSSH.
1797: Markus Friedl contributed the support for SSH
1798: protocol versions 1.5 and 2.0.
![[BACK]](/icons/back.gif){kind=icon}
Return to ssh.1 CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh