Annotation of src/usr.bin/ssh/ssh-agent.1, Revision 1.72
1.72 ! djm 1: .\" $OpenBSD: ssh-agent.1,v 1.71 2020/06/19 07:21:42 dtucker 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
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1.1 deraadt 36: .\"
1.72 ! djm 37: .Dd $Mdocdate: June 19 2020 $
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
1.72 ! djm 49: .Op Fl P Ar allowed_providers
1.36 marc 50: .Op Fl t Ar life
1.71 dtucker 51: .Nm ssh-agent
52: .Op Fl a Ar bind_address
53: .Op Fl E Ar fingerprint_hash
1.72 ! djm 54: .Op Fl P Ar allowed_providers
1.71 dtucker 55: .Op Fl t Ar life
56: .Ar command Op Ar arg ...
1.67 jmc 57: .Nm ssh-agent
58: .Op Fl c | s
59: .Fl k
1.11 aaron 60: .Sh DESCRIPTION
1.2 deraadt 61: .Nm
1.68 jmc 62: is a program to hold private keys used for public key authentication.
1.10 aaron 63: Through use of environment variables the agent can be located
1.14 markus 64: and automatically used for authentication when logging in to other
1.1 deraadt 65: machines using
1.2 deraadt 66: .Xr ssh 1 .
67: .Pp
1.7 markus 68: The options are as follows:
69: .Bl -tag -width Ds
1.32 markus 70: .It Fl a Ar bind_address
1.48 sobrado 71: Bind the agent to the
1.49 sobrado 72: .Ux Ns -domain
73: socket
1.32 markus 74: .Ar bind_address .
75: The default is
1.53 djm 76: .Pa $TMPDIR/ssh-XXXXXXXXXX/agent.\*(Ltppid\*(Gt .
1.7 markus 77: .It Fl c
78: Generate C-shell commands on
79: .Dv stdout .
80: This is the default if
81: .Ev SHELL
82: looks like it's a csh style of shell.
1.58 djm 83: .It Fl D
84: Foreground mode.
85: When this option is specified
86: .Nm
87: will not fork.
1.46 sobrado 88: .It Fl d
89: Debug mode.
90: When this option is specified
91: .Nm
1.58 djm 92: will not fork and will write debug information to standard error.
1.57 djm 93: .It Fl E Ar fingerprint_hash
94: Specifies the hash algorithm used when displaying key fingerprints.
95: Valid options are:
96: .Dq md5
97: and
98: .Dq sha256 .
99: The default is
100: .Dq sha256 .
1.46 sobrado 101: .It Fl k
102: Kill the current agent (given by the
103: .Ev SSH_AGENT_PID
104: environment variable).
1.72 ! djm 105: .It Fl P Ar allowed_providers
! 106: Specify a pattern-list of acceptable paths for PKCS#11 provider and FIDO
! 107: authenticator middleware shared libraries that may be used with the
1.68 jmc 108: .Fl S
109: or
1.63 djm 110: .Fl s
1.65 djm 111: options to
1.63 djm 112: .Xr ssh-add 1 .
1.72 ! djm 113: Libraries that do not match the pattern list will be refused.
1.63 djm 114: See PATTERNS in
115: .Xr ssh_config 5
116: for a description of pattern-list syntax.
1.72 ! djm 117: The default list is
1.68 jmc 118: .Dq /usr/lib/*,/usr/local/lib/* .
1.7 markus 119: .It Fl s
120: Generate Bourne shell commands on
121: .Dv stdout .
122: This is the default if
123: .Ev SHELL
124: does not look like it's a csh style of shell.
1.36 marc 125: .It Fl t Ar life
1.37 jmc 126: Set a default value for the maximum lifetime of identities added to the agent.
1.36 marc 127: The lifetime may be specified in seconds or in a time format specified in
1.43 dtucker 128: .Xr sshd_config 5 .
1.36 marc 129: A lifetime specified for an identity with
130: .Xr ssh-add 1
131: overrides this value.
132: Without this option the default maximum lifetime is forever.
1.68 jmc 133: .It Ar command Op Ar arg ...
134: If a command (and optional arguments) is given,
135: this is executed as a subprocess of the agent.
136: The agent exits automatically when the command given on the command
137: line terminates.
1.7 markus 138: .El
139: .Pp
1.68 jmc 140: There are two main ways to get an agent set up.
141: The first is at the start of an X session,
142: where all other windows or programs are started as children of the
143: .Nm
144: program.
145: The agent starts a command under which its environment
146: variables are exported, for example
147: .Cm ssh-agent xterm & .
148: When the command terminates, so does the agent.
1.7 markus 149: .Pp
1.68 jmc 150: The second method is used for a login session.
151: When
152: .Nm
153: is started,
154: it prints the shell commands required to set its environment variables,
155: which in turn can be evaluated in the calling shell, for example
156: .Cm eval `ssh-agent -s` .
1.40 dtucker 157: .Pp
1.68 jmc 158: In both cases,
1.7 markus 159: .Xr ssh 1
1.68 jmc 160: looks at these environment variables and uses them to establish a connection to the agent.
1.29 stevesk 161: .Pp
1.68 jmc 162: The agent initially does not have any private keys.
163: Keys are added using
164: .Xr ssh-add 1
165: or by
166: .Xr ssh 1
167: when
168: .Cm AddKeysToAgent
169: is set in
170: .Xr ssh_config 5 .
171: Multiple identities may be stored in
172: .Nm
173: concurrently and
174: .Xr ssh 1
175: will automatically use them if present.
176: .Xr ssh-add 1
177: is also used to remove keys from
178: .Nm
179: and to query the keys that are held in one.
1.7 markus 180: .Pp
1.68 jmc 181: Connections to
182: .Nm
183: may be forwarded from further remote hosts using the
184: .Fl A
185: option to
186: .Xr ssh 1
187: (but see the caveats documented therein),
188: avoiding the need for authentication data to be stored on other machines.
189: Authentication passphrases and private keys never go over the network:
190: the connection to the agent is forwarded over SSH remote connections
191: and the result is returned to the requester,
192: allowing the user access to their identities anywhere in the network
193: in a secure fashion.
194: .Sh ENVIRONMENT
195: .Bl -tag -width "SSH_AGENT_PID"
196: .It Ev SSH_AGENT_PID
197: When
198: .Nm
199: starts, it stores the name of the agent's process ID (PID) in this variable.
200: .It Ev SSH_AUTH_SOCK
201: When
202: .Nm
203: starts, it creates a
1.49 sobrado 204: .Ux Ns -domain
1.68 jmc 205: socket and stores its pathname in this variable.
206: It is accessible only to the current user,
207: but is easily abused by root or another instance of the same user.
208: .El
1.2 deraadt 209: .Sh FILES
210: .Bl -tag -width Ds
1.64 jmc 211: .It Pa $TMPDIR/ssh-XXXXXXXXXX/agent.<ppid>
1.49 sobrado 212: .Ux Ns -domain
213: sockets used to contain the connection to the authentication agent.
1.10 aaron 214: These sockets should only be readable by the owner.
215: The sockets should get automatically removed when the agent exits.
1.13 aaron 216: .El
1.39 jmc 217: .Sh SEE ALSO
218: .Xr ssh 1 ,
219: .Xr ssh-add 1 ,
220: .Xr ssh-keygen 1 ,
1.68 jmc 221: .Xr ssh_config 5 ,
1.39 jmc 222: .Xr sshd 8
1.17 aaron 223: .Sh AUTHORS
1.64 jmc 224: .An -nosplit
225: OpenSSH is a derivative of the original and free ssh 1.2.12 release by
226: .An Tatu Ylonen .
227: .An Aaron Campbell , Bob Beck , Markus Friedl , Niels Provos , Theo de Raadt
228: and
229: .An Dug Song
230: removed many bugs, re-added newer features and created OpenSSH.
231: .An Markus Friedl
232: contributed the support for SSH protocol versions 1.5 and 2.0.
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