Annotation of src/usr.bin/ssh/ssh-agent.1, Revision 1.55
1.55 ! djm 1: .\" $OpenBSD: ssh-agent.1,v 1.54 2013/12/07 11:58:46 naddy 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: .\"
1.55 ! djm 37: .Dd $Mdocdate: December 7 2013 $
1.2 deraadt 38: .Dt SSH-AGENT 1
39: .Os
40: .Sh NAME
41: .Nm ssh-agent
42: .Nd authentication agent
43: .Sh SYNOPSIS
1.11 aaron 44: .Nm ssh-agent
1.52 jmc 45: .Op Fl c | s
1.46 sobrado 46: .Op Fl d
1.32 markus 47: .Op Fl a Ar bind_address
1.36 marc 48: .Op Fl t Ar life
1.46 sobrado 49: .Op Ar command Op Ar arg ...
1.18 markus 50: .Nm ssh-agent
1.52 jmc 51: .Op Fl c | s
1.18 markus 52: .Fl k
1.11 aaron 53: .Sh DESCRIPTION
1.2 deraadt 54: .Nm
1.14 markus 55: is a program to hold private keys used for public key authentication
1.54 naddy 56: (RSA, DSA, ECDSA, ED25519).
1.2 deraadt 57: .Nm
1.55 ! djm 58: is usually started in the beginning of an X-session or a login session, and
1.7 markus 59: all other windows or programs are started as clients to the ssh-agent
1.10 aaron 60: program.
61: Through use of environment variables the agent can be located
1.14 markus 62: and automatically used for authentication when logging in to other
1.1 deraadt 63: machines using
1.2 deraadt 64: .Xr ssh 1 .
65: .Pp
1.55 ! djm 66: The agent initially does not have any private keys.
! 67: Keys are added using
! 68: .Xr ssh-add 1 .
! 69: Multiple identities may be stored in
! 70: .Nm
! 71: concurrently and
! 72: .Xr ssh 1
! 73: will automatically use them if present.
! 74: .Xr ssh-add 1
! 75: is also used to remove keys from
! 76: .Nm
! 77: and to query the keys that are held in one.
! 78: .Pp
1.7 markus 79: The options are as follows:
80: .Bl -tag -width Ds
1.32 markus 81: .It Fl a Ar bind_address
1.48 sobrado 82: Bind the agent to the
1.49 sobrado 83: .Ux Ns -domain
84: socket
1.32 markus 85: .Ar bind_address .
86: The default is
1.53 djm 87: .Pa $TMPDIR/ssh-XXXXXXXXXX/agent.\*(Ltppid\*(Gt .
1.7 markus 88: .It Fl c
89: Generate C-shell commands on
90: .Dv stdout .
91: This is the default if
92: .Ev SHELL
93: looks like it's a csh style of shell.
1.46 sobrado 94: .It Fl d
95: Debug mode.
96: When this option is specified
97: .Nm
98: will not fork.
99: .It Fl k
100: Kill the current agent (given by the
101: .Ev SSH_AGENT_PID
102: environment variable).
1.7 markus 103: .It Fl s
104: Generate Bourne shell commands on
105: .Dv stdout .
106: This is the default if
107: .Ev SHELL
108: does not look like it's a csh style of shell.
1.36 marc 109: .It Fl t Ar life
1.37 jmc 110: Set a default value for the maximum lifetime of identities added to the agent.
1.36 marc 111: The lifetime may be specified in seconds or in a time format specified in
1.43 dtucker 112: .Xr sshd_config 5 .
1.36 marc 113: A lifetime specified for an identity with
114: .Xr ssh-add 1
115: overrides this value.
116: Without this option the default maximum lifetime is forever.
1.7 markus 117: .El
118: .Pp
119: If a commandline is given, this is executed as a subprocess of the agent.
120: When the command dies, so does the agent.
121: .Pp
1.1 deraadt 122: The idea is that the agent is run in the user's local PC, laptop, or
1.10 aaron 123: terminal.
124: Authentication data need not be stored on any other
1.1 deraadt 125: machine, and authentication passphrases never go over the network.
1.2 deraadt 126: However, the connection to the agent is forwarded over SSH
1.1 deraadt 127: remote logins, and the user can thus use the privileges given by the
128: identities anywhere in the network in a secure way.
1.2 deraadt 129: .Pp
1.38 jmc 130: There are two main ways to get an agent set up:
1.40 dtucker 131: The first is that the agent starts a new subcommand into which some environment
132: variables are exported, eg
133: .Cm ssh-agent xterm & .
134: The second is that the agent prints the needed shell commands (either
1.7 markus 135: .Xr sh 1
136: or
137: .Xr csh 1
1.47 sobrado 138: syntax can be generated) which can be evaluated in the calling shell, eg
1.40 dtucker 139: .Cm eval `ssh-agent -s`
140: for Bourne-type shells such as
141: .Xr sh 1
142: or
143: .Xr ksh 1
144: and
1.41 deraadt 145: .Cm eval `ssh-agent -c`
1.40 dtucker 146: for
147: .Xr csh 1
148: and derivatives.
149: .Pp
1.7 markus 150: Later
151: .Xr ssh 1
1.23 deraadt 152: looks at these variables and uses them to establish a connection to the agent.
1.29 stevesk 153: .Pp
154: The agent will never send a private key over its request channel.
155: Instead, operations that require a private key will be performed
156: by the agent, and the result will be returned to the requester.
157: This way, private keys are not exposed to clients using the agent.
1.7 markus 158: .Pp
1.48 sobrado 159: A
1.49 sobrado 160: .Ux Ns -domain
161: socket is created and the name of this socket is stored in the
1.5 markus 162: .Ev SSH_AUTH_SOCK
1.1 deraadt 163: environment
1.10 aaron 164: variable.
165: The socket is made accessible only to the current user.
1.1 deraadt 166: This method is easily abused by root or another instance of the same
1.4 markus 167: user.
1.7 markus 168: .Pp
169: The
170: .Ev SSH_AGENT_PID
1.34 stevesk 171: environment variable holds the agent's process ID.
1.2 deraadt 172: .Pp
1.1 deraadt 173: The agent exits automatically when the command given on the command
174: line terminates.
1.2 deraadt 175: .Sh FILES
176: .Bl -tag -width Ds
1.53 djm 177: .It Pa $TMPDIR/ssh-XXXXXXXXXX/agent.\*(Ltppid\*(Gt
1.49 sobrado 178: .Ux Ns -domain
179: sockets used to contain the connection to the authentication agent.
1.10 aaron 180: These sockets should only be readable by the owner.
181: The sockets should get automatically removed when the agent exits.
1.13 aaron 182: .El
1.39 jmc 183: .Sh SEE ALSO
184: .Xr ssh 1 ,
185: .Xr ssh-add 1 ,
186: .Xr ssh-keygen 1 ,
187: .Xr sshd 8
1.17 aaron 188: .Sh AUTHORS
1.20 markus 189: OpenSSH is a derivative of the original and free
190: ssh 1.2.12 release by Tatu Ylonen.
191: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
192: Theo de Raadt and Dug Song
193: removed many bugs, re-added newer features and
194: created OpenSSH.
195: Markus Friedl contributed the support for SSH
196: protocol versions 1.5 and 2.0.
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