Annotation of src/usr.bin/ssh/ssh-agent.1, Revision 1.75
1.75 ! jmc 1: .\" $OpenBSD: ssh-agent.1,v 1.74 2022/10/07 04:06:26 djm Exp $
1.7 markus 2: .\"
1.16 deraadt 3: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: .\" All rights reserved
1.1 deraadt 6: .\"
1.16 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".
1.1 deraadt 12: .\"
1.22 deraadt 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.
1.8 deraadt 16: .\"
1.16 deraadt 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: .\"
1.16 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
33: .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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: .\"
1.75 ! jmc 37: .Dd $Mdocdate: October 7 2022 $
1.2 deraadt 38: .Dt SSH-AGENT 1
39: .Os
40: .Sh NAME
41: .Nm ssh-agent
1.69 jmc 42: .Nd OpenSSH authentication agent
1.2 deraadt 43: .Sh SYNOPSIS
1.11 aaron 44: .Nm ssh-agent
1.52 jmc 45: .Op Fl c | s
1.67 jmc 46: .Op Fl \&Dd
1.32 markus 47: .Op Fl a Ar bind_address
1.57 djm 48: .Op Fl E Ar fingerprint_hash
1.74 djm 49: .Op Fl O Ar option
1.72 djm 50: .Op Fl P Ar allowed_providers
1.36 marc 51: .Op Fl t Ar life
1.71 dtucker 52: .Nm ssh-agent
53: .Op Fl a Ar bind_address
54: .Op Fl E Ar fingerprint_hash
1.74 djm 55: .Op Fl O Ar option
1.72 djm 56: .Op Fl P Ar allowed_providers
1.71 dtucker 57: .Op Fl t Ar life
58: .Ar command Op Ar arg ...
1.67 jmc 59: .Nm ssh-agent
60: .Op Fl c | s
61: .Fl k
1.11 aaron 62: .Sh DESCRIPTION
1.2 deraadt 63: .Nm
1.68 jmc 64: is a program to hold private keys used for public key authentication.
1.10 aaron 65: Through use of environment variables the agent can be located
1.14 markus 66: and automatically used for authentication when logging in to other
1.1 deraadt 67: machines using
1.2 deraadt 68: .Xr ssh 1 .
69: .Pp
1.7 markus 70: The options are as follows:
71: .Bl -tag -width Ds
1.32 markus 72: .It Fl a Ar bind_address
1.48 sobrado 73: Bind the agent to the
1.49 sobrado 74: .Ux Ns -domain
75: socket
1.32 markus 76: .Ar bind_address .
77: The default is
1.53 djm 78: .Pa $TMPDIR/ssh-XXXXXXXXXX/agent.\*(Ltppid\*(Gt .
1.7 markus 79: .It Fl c
80: Generate C-shell commands on
81: .Dv stdout .
82: This is the default if
83: .Ev SHELL
84: looks like it's a csh style of shell.
1.58 djm 85: .It Fl D
86: Foreground mode.
1.73 naddy 87: When this option is specified,
1.58 djm 88: .Nm
89: will not fork.
1.46 sobrado 90: .It Fl d
91: Debug mode.
1.73 naddy 92: When this option is specified,
1.46 sobrado 93: .Nm
1.58 djm 94: will not fork and will write debug information to standard error.
1.57 djm 95: .It Fl E Ar fingerprint_hash
96: Specifies the hash algorithm used when displaying key fingerprints.
97: Valid options are:
98: .Dq md5
99: and
100: .Dq sha256 .
101: The default is
102: .Dq sha256 .
1.46 sobrado 103: .It Fl k
104: Kill the current agent (given by the
105: .Ev SSH_AGENT_PID
106: environment variable).
1.74 djm 107: .It Fl O Ar option
108: Specify an option when starting
1.75 ! jmc 109: .Nm .
1.74 djm 110: Currently only one option is supported:
111: .Cm no-restrict-websafe .
112: This instructs
1.75 ! jmc 113: .Nm
1.74 djm 114: to permit signatures using FIDO keys that might be web authentication
115: requests.
116: By default,
1.75 ! jmc 117: .Nm
1.74 djm 118: refuses signature requests for FIDO keys where the key application string
119: does not start with
120: .Dq ssh:
121: and when the data to be signed does not appear to be a
122: .Xr ssh 1
123: user authentication request or a
124: .Xr ssh-keygen 1
125: signature.
126: The default behaviour prevents forwarded access to a FIDO key from also
127: implicitly forwarding the ability to authenticate to websites.
1.72 djm 128: .It Fl P Ar allowed_providers
129: Specify a pattern-list of acceptable paths for PKCS#11 provider and FIDO
130: authenticator middleware shared libraries that may be used with the
1.68 jmc 131: .Fl S
132: or
1.63 djm 133: .Fl s
1.65 djm 134: options to
1.63 djm 135: .Xr ssh-add 1 .
1.72 djm 136: Libraries that do not match the pattern list will be refused.
1.63 djm 137: See PATTERNS in
138: .Xr ssh_config 5
139: for a description of pattern-list syntax.
1.72 djm 140: The default list is
1.68 jmc 141: .Dq /usr/lib/*,/usr/local/lib/* .
1.7 markus 142: .It Fl s
143: Generate Bourne shell commands on
144: .Dv stdout .
145: This is the default if
146: .Ev SHELL
147: does not look like it's a csh style of shell.
1.36 marc 148: .It Fl t Ar life
1.37 jmc 149: Set a default value for the maximum lifetime of identities added to the agent.
1.36 marc 150: The lifetime may be specified in seconds or in a time format specified in
1.43 dtucker 151: .Xr sshd_config 5 .
1.36 marc 152: A lifetime specified for an identity with
153: .Xr ssh-add 1
154: overrides this value.
155: Without this option the default maximum lifetime is forever.
1.68 jmc 156: .It Ar command Op Ar arg ...
157: If a command (and optional arguments) is given,
158: this is executed as a subprocess of the agent.
159: The agent exits automatically when the command given on the command
160: line terminates.
1.7 markus 161: .El
162: .Pp
1.68 jmc 163: There are two main ways to get an agent set up.
164: The first is at the start of an X session,
165: where all other windows or programs are started as children of the
166: .Nm
167: program.
168: The agent starts a command under which its environment
169: variables are exported, for example
170: .Cm ssh-agent xterm & .
171: When the command terminates, so does the agent.
1.7 markus 172: .Pp
1.68 jmc 173: The second method is used for a login session.
174: When
175: .Nm
176: is started,
177: it prints the shell commands required to set its environment variables,
178: which in turn can be evaluated in the calling shell, for example
179: .Cm eval `ssh-agent -s` .
1.40 dtucker 180: .Pp
1.68 jmc 181: In both cases,
1.7 markus 182: .Xr ssh 1
1.75 ! jmc 183: looks at these environment variables
! 184: and uses them to establish a connection to the agent.
1.29 stevesk 185: .Pp
1.68 jmc 186: The agent initially does not have any private keys.
187: Keys are added using
188: .Xr ssh-add 1
189: or by
190: .Xr ssh 1
191: when
192: .Cm AddKeysToAgent
193: is set in
194: .Xr ssh_config 5 .
195: Multiple identities may be stored in
196: .Nm
197: concurrently and
198: .Xr ssh 1
199: will automatically use them if present.
200: .Xr ssh-add 1
201: is also used to remove keys from
202: .Nm
203: and to query the keys that are held in one.
1.7 markus 204: .Pp
1.68 jmc 205: Connections to
206: .Nm
207: may be forwarded from further remote hosts using the
208: .Fl A
209: option to
210: .Xr ssh 1
211: (but see the caveats documented therein),
212: avoiding the need for authentication data to be stored on other machines.
213: Authentication passphrases and private keys never go over the network:
214: the connection to the agent is forwarded over SSH remote connections
215: and the result is returned to the requester,
216: allowing the user access to their identities anywhere in the network
217: in a secure fashion.
218: .Sh ENVIRONMENT
219: .Bl -tag -width "SSH_AGENT_PID"
220: .It Ev SSH_AGENT_PID
221: When
222: .Nm
223: starts, it stores the name of the agent's process ID (PID) in this variable.
224: .It Ev SSH_AUTH_SOCK
225: When
226: .Nm
227: starts, it creates a
1.49 sobrado 228: .Ux Ns -domain
1.68 jmc 229: socket and stores its pathname in this variable.
230: It is accessible only to the current user,
231: but is easily abused by root or another instance of the same user.
232: .El
1.2 deraadt 233: .Sh FILES
234: .Bl -tag -width Ds
1.64 jmc 235: .It Pa $TMPDIR/ssh-XXXXXXXXXX/agent.<ppid>
1.49 sobrado 236: .Ux Ns -domain
237: sockets used to contain the connection to the authentication agent.
1.10 aaron 238: These sockets should only be readable by the owner.
239: The sockets should get automatically removed when the agent exits.
1.13 aaron 240: .El
1.39 jmc 241: .Sh SEE ALSO
242: .Xr ssh 1 ,
243: .Xr ssh-add 1 ,
244: .Xr ssh-keygen 1 ,
1.68 jmc 245: .Xr ssh_config 5 ,
1.39 jmc 246: .Xr sshd 8
1.17 aaron 247: .Sh AUTHORS
1.64 jmc 248: .An -nosplit
249: OpenSSH is a derivative of the original and free ssh 1.2.12 release by
250: .An Tatu Ylonen .
251: .An Aaron Campbell , Bob Beck , Markus Friedl , Niels Provos , Theo de Raadt
252: and
253: .An Dug Song
254: removed many bugs, re-added newer features and created OpenSSH.
255: .An Markus Friedl
256: contributed the support for SSH protocol versions 1.5 and 2.0.
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