[gssapi-openssh.git] / openssh / ssh-agent.1

.\" $OpenBSD: ssh-agent.1,v 1.31 2002/02/04 20:41:16 stevesk Exp $
.\"
.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
.\"                    All rights reserved
.\"
.\" As far as I am concerned, the code I have written for this software
.\" can be used freely for any purpose.  Any derived versions of this
.\" software must be clearly marked as such, and if the derived work is
.\" incompatible with the protocol description in the RFC file, it must be
.\" called by a name other than "ssh" or "Secure Shell".
.\"
.\" Copyright (c) 1999,2000 Markus Friedl.  All rights reserved.
.\" Copyright (c) 1999 Aaron Campbell.  All rights reserved.
.\" Copyright (c) 1999 Theo de Raadt.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd September 25, 1999
.Dt SSH-AGENT 1
.Os
.Sh NAME
.Nm ssh-agent
.Nd authentication agent
.Sh SYNOPSIS
.Nm ssh-agent
.Op Fl c Li | Fl s
.Op Fl d
.Op Ar command Op Ar args ...
.Nm ssh-agent
.Op Fl c Li | Fl s
.Fl k
.Sh DESCRIPTION
.Nm
is a program to hold private keys used for public key authentication
(RSA, DSA).
The idea is that
.Nm
is started in the beginning of an X-session or a login session, and
all other windows or programs are started as clients to the ssh-agent
program.
Through use of environment variables the agent can be located
and automatically used for authentication when logging in to other
machines using
.Xr ssh 1 .
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl c
Generate C-shell commands on
.Dv stdout .
This is the default if
.Ev SHELL
looks like it's a csh style of shell.
.It Fl s
Generate Bourne shell commands on
.Dv stdout .
This is the default if
.Ev SHELL
does not look like it's a csh style of shell.
.It Fl k
Kill the current agent (given by the
.Ev SSH_AGENT_PID
environment variable).
.It Fl d
Debug mode.  When this option is specified
.Nm
will not fork.
.El
.Pp
If a commandline is given, this is executed as a subprocess of the agent.
When the command dies, so does the agent.
.Pp
The agent initially does not have any private keys.
Keys are added using
.Xr ssh-add 1 .
When executed without arguments,
.Xr ssh-add 1
adds the files
.Pa $HOME/.ssh/id_rsa ,
.Pa $HOME/.ssh/id_dsa 
and
.Pa $HOME/.ssh/identity .
If the identity has a passphrase,
.Xr ssh-add 1
asks for the passphrase (using a small X11 application if running
under X11, or from the terminal if running without X).
It then sends the identity to the agent.
Several identities can be stored in the
agent; the agent can automatically use any of these identities.
.Ic ssh-add -l
displays the identities currently held by the agent.
.Pp
The idea is that the agent is run in the user's local PC, laptop, or
terminal.
Authentication data need not be stored on any other
machine, and authentication passphrases never go over the network.
However, the connection to the agent is forwarded over SSH
remote logins, and the user can thus use the privileges given by the
identities anywhere in the network in a secure way.
.Pp
There are two main ways to get an agent setup:
Either the agent starts a new subcommand into which some environment
variables are exported, or the agent prints the needed shell commands
(either
.Xr sh 1
or
.Xr csh 1
syntax can be generated) which can be evalled in the calling shell.
Later
.Xr ssh 1
looks at these variables and uses them to establish a connection to the agent.
.Pp
The agent will never send a private key over its request channel.
Instead, operations that require a private key will be performed
by the agent, and the result will be returned to the requester.
This way, private keys are not exposed to clients using the agent.
.Pp
A unix-domain socket is created
.Pq Pa /tmp/ssh-XXXXXXXX/agent.<pid> ,
and the name of this socket is stored in the
.Ev SSH_AUTH_SOCK
environment
variable.
The socket is made accessible only to the current user.
This method is easily abused by root or another instance of the same
user.
.Pp
The
.Ev SSH_AGENT_PID
environment variable holds the agent's PID.
.Pp
The agent exits automatically when the command given on the command
line terminates.
.Sh FILES
.Bl -tag -width Ds
.It Pa $HOME/.ssh/identity
Contains the protocol version 1 RSA authentication identity of the user.
.It Pa $HOME/.ssh/id_dsa
Contains the protocol version 2 DSA authentication identity of the user.
.It Pa $HOME/.ssh/id_rsa
Contains the protocol version 2 RSA authentication identity of the user.
.It Pa /tmp/ssh-XXXXXXXX/agent.<pid>
Unix-domain sockets used to contain the connection to the
authentication agent.
These sockets should only be readable by the owner.
The sockets should get automatically removed when the agent exits.
.El
.Sh AUTHORS
OpenSSH is a derivative of the original and free
ssh 1.2.12 release by Tatu Ylonen.
Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
Theo de Raadt and Dug Song
removed many bugs, re-added newer features and
created OpenSSH.
Markus Friedl contributed the support for SSH
protocol versions 1.5 and 2.0.
.Sh SEE ALSO
.Xr ssh 1 ,
.Xr ssh-add 1 ,
.Xr ssh-keygen 1 ,
.Xr sshd 8
Commit	Line	Data
e9a17296	1	.\" $OpenBSD: ssh-agent.1,v 1.31 2002/02/04 20:41:16 stevesk Exp $
3c0ef626	2	.\"
	3	.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
	4	.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	5	.\" All rights reserved
	6	.\"
	7	.\" As far as I am concerned, the code I have written for this software
	8	.\" can be used freely for any purpose. Any derived versions of this
	9	.\" software must be clearly marked as such, and if the derived work is
	10	.\" incompatible with the protocol description in the RFC file, it must be
	11	.\" called by a name other than "ssh" or "Secure Shell".
	12	.\"
	13	.\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
	14	.\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
	15	.\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
	16	.\"
	17	.\" Redistribution and use in source and binary forms, with or without
	18	.\" modification, are permitted provided that the following conditions
	19	.\" are met:
	20	.\" 1. Redistributions of source code must retain the above copyright
	21	.\" notice, this list of conditions and the following disclaimer.
	22	.\" 2. Redistributions in binary form must reproduce the above copyright
	23	.\" notice, this list of conditions and the following disclaimer in the
	24	.\" documentation and/or other materials provided with the distribution.
	25	.\"
	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.
	36	.\"
	37	.Dd September 25, 1999
	38	.Dt SSH-AGENT 1
	39	.Os
	40	.Sh NAME
	41	.Nm ssh-agent
	42	.Nd authentication agent
	43	.Sh SYNOPSIS
	44	.Nm ssh-agent
	45	.Op Fl c Li \| Fl s
	46	.Op Fl d
	47	.Op Ar command Op Ar args ...
	48	.Nm ssh-agent
	49	.Op Fl c Li \| Fl s
	50	.Fl k
	51	.Sh DESCRIPTION
	52	.Nm
	53	is a program to hold private keys used for public key authentication
	54	(RSA, DSA).
	55	The idea is that
	56	.Nm
	57	is started in the beginning of an X-session or a login session, and
	58	all other windows or programs are started as clients to the ssh-agent
	59	program.
	60	Through use of environment variables the agent can be located
	61	and automatically used for authentication when logging in to other
	62	machines using
	63	.Xr ssh 1 .
	64	.Pp
	65	The options are as follows:
66	.Bl -tag -width Ds
67	.It Fl c
68	Generate C-shell commands on
69	.Dv stdout .
70	This is the default if
71	.Ev SHELL
72	looks like it's a csh style of shell.
73	.It Fl s
74	Generate Bourne shell commands on
75	.Dv stdout .
76	This is the default if
77	.Ev SHELL
78	does not look like it's a csh style of shell.
79	.It Fl k
80	Kill the current agent (given by the
81	.Ev SSH_AGENT_PID
82	environment variable).
83	.It Fl d
84	Debug mode. When this option is specified
85	.Nm
86	will not fork.
87	.El
88	.Pp
89	If a commandline is given, this is executed as a subprocess of the agent.
90	When the command dies, so does the agent.
91	.Pp
92	The agent initially does not have any private keys.
93	Keys are added using
94	.Xr ssh-add 1 .
95	When executed without arguments,
96	.Xr ssh-add 1
e9a17296	97	adds the files
	98	.Pa $HOME/.ssh/id_rsa ,
	99	.Pa $HOME/.ssh/id_dsa
	100	and
	101	.Pa $HOME/.ssh/identity .
3c0ef626	102	If the identity has a passphrase,
	103	.Xr ssh-add 1
	104	asks for the passphrase (using a small X11 application if running
	105	under X11, or from the terminal if running without X).
	106	It then sends the identity to the agent.
	107	Several identities can be stored in the
	108	agent; the agent can automatically use any of these identities.
	109	.Ic ssh-add -l
	110	displays the identities currently held by the agent.
	111	.Pp
	112	The idea is that the agent is run in the user's local PC, laptop, or
	113	terminal.
	114	Authentication data need not be stored on any other
	115	machine, and authentication passphrases never go over the network.
	116	However, the connection to the agent is forwarded over SSH
	117	remote logins, and the user can thus use the privileges given by the
	118	identities anywhere in the network in a secure way.
	119	.Pp
	120	There are two main ways to get an agent setup:
	121	Either the agent starts a new subcommand into which some environment
	122	variables are exported, or the agent prints the needed shell commands
	123	(either
	124	.Xr sh 1
	125	or
	126	.Xr csh 1
	127	syntax can be generated) which can be evalled in the calling shell.
	128	Later
	129	.Xr ssh 1
	130	looks at these variables and uses them to establish a connection to the agent.
	131	.Pp
e9a17296	132	The agent will never send a private key over its request channel.
	133	Instead, operations that require a private key will be performed
	134	by the agent, and the result will be returned to the requester.
	135	This way, private keys are not exposed to clients using the agent.
	136	.Pp
3c0ef626	137	A unix-domain socket is created
	138	.Pq Pa /tmp/ssh-XXXXXXXX/agent.<pid> ,
	139	and the name of this socket is stored in the
	140	.Ev SSH_AUTH_SOCK
	141	environment
	142	variable.
	143	The socket is made accessible only to the current user.
	144	This method is easily abused by root or another instance of the same
	145	user.
	146	.Pp
	147	The
	148	.Ev SSH_AGENT_PID
	149	environment variable holds the agent's PID.
	150	.Pp
	151	The agent exits automatically when the command given on the command
	152	line terminates.
	153	.Sh FILES
	154	.Bl -tag -width Ds
	155	.It Pa $HOME/.ssh/identity
	156	Contains the protocol version 1 RSA authentication identity of the user.
3c0ef626	157	.It Pa $HOME/.ssh/id_dsa
	158	Contains the protocol version 2 DSA authentication identity of the user.
	159	.It Pa $HOME/.ssh/id_rsa
	160	Contains the protocol version 2 RSA authentication identity of the user.
	161	.It Pa /tmp/ssh-XXXXXXXX/agent.<pid>
	162	Unix-domain sockets used to contain the connection to the
	163	authentication agent.
	164	These sockets should only be readable by the owner.
	165	The sockets should get automatically removed when the agent exits.
	166	.El
	167	.Sh AUTHORS
	168	OpenSSH is a derivative of the original and free
	169	ssh 1.2.12 release by Tatu Ylonen.
	170	Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
	171	Theo de Raadt and Dug Song
	172	removed many bugs, re-added newer features and
	173	created OpenSSH.
	174	Markus Friedl contributed the support for SSH
	175	protocol versions 1.5 and 2.0.
	176	.Sh SEE ALSO
	177	.Xr ssh 1 ,
	178	.Xr ssh-add 1 ,
	179	.Xr ssh-keygen 1 ,
	180	.Xr sshd 8