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.\" $OpenBSD: ssh-agent.1,v 1.64 2016/11/30 06:54:26 jmc Exp $
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.\"
.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
.\" All rights reserved
.\"
- (djm) Merge OpenBSD changes: - markus@cvs.openbsd.org 2000/09/05 02:59:57 [session.c] print hostname (not hushlogin) - markus@cvs.openbsd.org 2000/09/05 13:18:48 [authfile.c ssh-add.c] enable ssh-add -d for DSA keys - markus@cvs.openbsd.org 2000/09/05 13:20:49 [sftp-server.c] cleanup - markus@cvs.openbsd.org 2000/09/06 03:46:41 [authfile.h] prototype - deraadt@cvs.openbsd.org 2000/09/07 14:27:56 [ALL] cleanup copyright notices on all files. I have attempted to be accurate with the details. everything is now under Tatu's licence (which I copied from his readme), and/or the core-sdi bsd-ish thing for deattack, or various openbsd developers under a 2-term bsd licence. We're not changing any rules, just being accurate. - markus@cvs.openbsd.org 2000/09/07 14:40:30 [channels.c channels.h clientloop.c serverloop.c ssh.c] cleanup window and packet sizes for ssh2 flow control; ok niels - markus@cvs.openbsd.org 2000/09/07 14:53:00 [scp.c] typo - markus@cvs.openbsd.org 2000/09/07 15:13:37 [auth-options.c auth-options.h auth-rh-rsa.c auth-rsa.c auth.c] [authfile.h canohost.c channels.h compat.c hostfile.h log.c match.h] [pty.c readconf.c] some more Copyright fixes - markus@cvs.openbsd.org 2000/09/08 03:02:51 [README.openssh2] bye bye - deraadt@cvs.openbsd.org 2000/09/11 18:38:33 [LICENCE cipher.c] a few more comments about it being ARC4 not RC4 - markus@cvs.openbsd.org 2000/09/12 14:53:11 [log-client.c log-server.c log.c ssh.1 ssh.c ssh.h sshd.8 sshd.c] multiple debug levels - markus@cvs.openbsd.org 2000/09/14 14:25:15 [clientloop.c] typo - deraadt@cvs.openbsd.org 2000/09/15 01:13:51 [ssh-agent.c] check return value for setenv(3) for failure, and deal appropriately
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.\" 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.
- (djm) Merge OpenBSD changes: - markus@cvs.openbsd.org 2000/09/05 02:59:57 [session.c] print hostname (not hushlogin) - markus@cvs.openbsd.org 2000/09/05 13:18:48 [authfile.c ssh-add.c] enable ssh-add -d for DSA keys - markus@cvs.openbsd.org 2000/09/05 13:20:49 [sftp-server.c] cleanup - markus@cvs.openbsd.org 2000/09/06 03:46:41 [authfile.h] prototype - deraadt@cvs.openbsd.org 2000/09/07 14:27:56 [ALL] cleanup copyright notices on all files. I have attempted to be accurate with the details. everything is now under Tatu's licence (which I copied from his readme), and/or the core-sdi bsd-ish thing for deattack, or various openbsd developers under a 2-term bsd licence. We're not changing any rules, just being accurate. - markus@cvs.openbsd.org 2000/09/07 14:40:30 [channels.c channels.h clientloop.c serverloop.c ssh.c] cleanup window and packet sizes for ssh2 flow control; ok niels - markus@cvs.openbsd.org 2000/09/07 14:53:00 [scp.c] typo - markus@cvs.openbsd.org 2000/09/07 15:13:37 [auth-options.c auth-options.h auth-rh-rsa.c auth-rsa.c auth.c] [authfile.h canohost.c channels.h compat.c hostfile.h log.c match.h] [pty.c readconf.c] some more Copyright fixes - markus@cvs.openbsd.org 2000/09/08 03:02:51 [README.openssh2] bye bye - deraadt@cvs.openbsd.org 2000/09/11 18:38:33 [LICENCE cipher.c] a few more comments about it being ARC4 not RC4 - markus@cvs.openbsd.org 2000/09/12 14:53:11 [log-client.c log-server.c log.c ssh.1 ssh.c ssh.h sshd.8 sshd.c] multiple debug levels - markus@cvs.openbsd.org 2000/09/14 14:25:15 [clientloop.c] typo - deraadt@cvs.openbsd.org 2000/09/15 01:13:51 [ssh-agent.c] check return value for setenv(3) for failure, and deal appropriately
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.\"
.\" 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.
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.\"
.Dd $Mdocdate: November 30 2016 $
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.Dt SSH-AGENT 1
.Os
.Sh NAME
.Nm ssh-agent
.Nd authentication agent
.Sh SYNOPSIS
.Nm ssh-agent
.Op Fl c | s
.Op Fl \&Dd
.Op Fl a Ar bind_address
.Op Fl E Ar fingerprint_hash
.Op Fl P Ar pkcs11_whitelist
.Op Fl t Ar life
.Op Ar command Op Ar arg ...
.Nm ssh-agent
.Op Fl c | s
.Fl k
.Sh DESCRIPTION
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.Nm
- (djm) Pick up LOGIN_PROGRAM from environment or PATH if not set by headers - (djm) OpenBSD CVS updates: - deraadt@cvs.openbsd.org 2000/08/18 20:07:23 [ssh.c] accept remsh as a valid name as well; roman@buildpoint.com - deraadt@cvs.openbsd.org 2000/08/18 20:17:13 [deattack.c crc32.c packet.c] rename crc32() to ssh_crc32() to avoid zlib name clash. do not move to libz crc32 function yet, because it has ugly "long"'s in it; oneill@cs.sfu.ca - deraadt@cvs.openbsd.org 2000/08/18 20:26:08 [scp.1 scp.c] -S prog support; tv@debian.org - deraadt@cvs.openbsd.org 2000/08/18 20:50:07 [scp.c] knf - deraadt@cvs.openbsd.org 2000/08/18 20:57:33 [log-client.c] shorten - markus@cvs.openbsd.org 2000/08/19 12:48:11 [channels.c channels.h clientloop.c ssh.c ssh.h] support for ~. in ssh2 - deraadt@cvs.openbsd.org 2000/08/19 15:29:40 [crc32.h] proper prototype - markus@cvs.openbsd.org 2000/08/19 15:34:44 [authfd.c authfd.h key.c key.h ssh-add.1 ssh-add.c ssh-agent.1] [ssh-agent.c ssh-keygen.c sshconnect1.c sshconnect2.c Makefile] [fingerprint.c fingerprint.h] add SSH2/DSA support to the agent and some other DSA related cleanups. (note that we cannot talk to ssh.com's ssh2 agents) - markus@cvs.openbsd.org 2000/08/19 15:55:52 [channels.c channels.h clientloop.c] more ~ support for ssh2 - markus@cvs.openbsd.org 2000/08/19 16:21:19 [clientloop.c] oops - millert@cvs.openbsd.org 2000/08/20 12:25:53 [session.c] We have to stash the result of get_remote_name_or_ip() before we close our socket or getpeername() will get EBADF and the process will exit. Only a problem for "UseLogin yes". - millert@cvs.openbsd.org 2000/08/20 12:30:59 [session.c] Only check /etc/nologin if "UseLogin no" since login(1) may have its own policy on determining who is allowed to login when /etc/nologin is present. Also use the _PATH_NOLOGIN define. - millert@cvs.openbsd.org 2000/08/20 12:42:43 [auth1.c auth2.c session.c ssh.c] Add calls to setusercontext() and login_get*(). We basically call setusercontext() in most places where previously we did a setlogin(). Add default login.conf file and put root in the "daemon" login class. - millert@cvs.openbsd.org 2000/08/21 10:23:31 [session.c] Fix incorrect PATH setting; noted by Markus.
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is a program to hold private keys used for public key authentication
(RSA, DSA, ECDSA, Ed25519).
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.Nm
is usually started in the beginning of an X-session or a login session, and
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all other windows or programs are started as clients to the ssh-agent
program.
Through use of environment variables the agent can be located
- (djm) Pick up LOGIN_PROGRAM from environment or PATH if not set by headers - (djm) OpenBSD CVS updates: - deraadt@cvs.openbsd.org 2000/08/18 20:07:23 [ssh.c] accept remsh as a valid name as well; roman@buildpoint.com - deraadt@cvs.openbsd.org 2000/08/18 20:17:13 [deattack.c crc32.c packet.c] rename crc32() to ssh_crc32() to avoid zlib name clash. do not move to libz crc32 function yet, because it has ugly "long"'s in it; oneill@cs.sfu.ca - deraadt@cvs.openbsd.org 2000/08/18 20:26:08 [scp.1 scp.c] -S prog support; tv@debian.org - deraadt@cvs.openbsd.org 2000/08/18 20:50:07 [scp.c] knf - deraadt@cvs.openbsd.org 2000/08/18 20:57:33 [log-client.c] shorten - markus@cvs.openbsd.org 2000/08/19 12:48:11 [channels.c channels.h clientloop.c ssh.c ssh.h] support for ~. in ssh2 - deraadt@cvs.openbsd.org 2000/08/19 15:29:40 [crc32.h] proper prototype - markus@cvs.openbsd.org 2000/08/19 15:34:44 [authfd.c authfd.h key.c key.h ssh-add.1 ssh-add.c ssh-agent.1] [ssh-agent.c ssh-keygen.c sshconnect1.c sshconnect2.c Makefile] [fingerprint.c fingerprint.h] add SSH2/DSA support to the agent and some other DSA related cleanups. (note that we cannot talk to ssh.com's ssh2 agents) - markus@cvs.openbsd.org 2000/08/19 15:55:52 [channels.c channels.h clientloop.c] more ~ support for ssh2 - markus@cvs.openbsd.org 2000/08/19 16:21:19 [clientloop.c] oops - millert@cvs.openbsd.org 2000/08/20 12:25:53 [session.c] We have to stash the result of get_remote_name_or_ip() before we close our socket or getpeername() will get EBADF and the process will exit. Only a problem for "UseLogin yes". - millert@cvs.openbsd.org 2000/08/20 12:30:59 [session.c] Only check /etc/nologin if "UseLogin no" since login(1) may have its own policy on determining who is allowed to login when /etc/nologin is present. Also use the _PATH_NOLOGIN define. - millert@cvs.openbsd.org 2000/08/20 12:42:43 [auth1.c auth2.c session.c ssh.c] Add calls to setusercontext() and login_get*(). We basically call setusercontext() in most places where previously we did a setlogin(). Add default login.conf file and put root in the "daemon" login class. - millert@cvs.openbsd.org 2000/08/21 10:23:31 [session.c] Fix incorrect PATH setting; noted by Markus.
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and automatically used for authentication when logging in to other
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machines using
.Xr ssh 1 .
.Pp
The agent initially does not have any private keys.
Keys are added using
.Xr ssh 1
(see
.Cm AddKeysToAgent
in
.Xr ssh_config 5
for details)
or
.Xr ssh-add 1 .
Multiple identities may be stored in
.Nm
concurrently and
.Xr ssh 1
will automatically use them if present.
.Xr ssh-add 1
is also used to remove keys from
.Nm
and to query the keys that are held in one.
.Pp
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The options are as follows:
.Bl -tag -width Ds
.It Fl a Ar bind_address
Bind the agent to the
.Ux Ns -domain
socket
.Ar bind_address .
The default is
.Pa $TMPDIR/ssh-XXXXXXXXXX/agent.\*(Ltppid\*(Gt .
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.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 D
Foreground mode.
When this option is specified
.Nm
will not fork.
.It Fl d
Debug mode.
When this option is specified
.Nm
will not fork and will write debug information to standard error.
.It Fl E Ar fingerprint_hash
Specifies the hash algorithm used when displaying key fingerprints.
Valid options are:
.Dq md5
and
.Dq sha256 .
The default is
.Dq sha256 .
.It Fl k
Kill the current agent (given by the
.Ev SSH_AGENT_PID
environment variable).
.It Fl P Ar pkcs11_whitelist
Specify a pattern-list of acceptable paths for PKCS#11 shared libraries
that may be added using the
.Fl s
option to
.Xr ssh-add 1 .
The default is to allow loading PKCS#11 libraries from
.Dq /usr/lib/*,/usr/local/lib/* .
PKCS#11 libraries that do not match the whitelist will be refused.
See PATTERNS in
.Xr ssh_config 5
for a description of pattern-list syntax.
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.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 t Ar life
Set a default value for the maximum lifetime of identities added to the agent.
The lifetime may be specified in seconds or in a time format specified in
.Xr sshd_config 5 .
A lifetime specified for an identity with
.Xr ssh-add 1
overrides this value.
Without this option the default maximum lifetime is forever.
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.El
.Pp
If a command line is given, this is executed as a subprocess of the agent.
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When the command dies, so does 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
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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 set up:
The first is that the agent starts a new subcommand into which some environment
variables are exported, eg
.Cm ssh-agent xterm & .
The second is that the agent prints the needed shell commands (either
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.Xr sh 1
or
.Xr csh 1
syntax can be generated) which can be evaluated in the calling shell, eg
.Cm eval `ssh-agent -s`
for Bourne-type shells such as
.Xr sh 1
or
.Xr ksh 1
and
.Cm eval `ssh-agent -c`
for
.Xr csh 1
and derivatives.
.Pp
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Later
.Xr ssh 1
looks at these variables and uses them to establish a connection to the agent.
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.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
.Ux Ns -domain
socket is created and the name of this socket is stored in the
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.Ev SSH_AUTH_SOCK
environment
variable.
The socket is made accessible only to the current user.
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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 process ID.
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.Pp
The agent exits automatically when the command given on the command
line terminates.
.Sh FILES
.Bl -tag -width Ds
.It Pa $TMPDIR/ssh-XXXXXXXXXX/agent.<ppid>
.Ux Ns -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 SEE ALSO
.Xr ssh 1 ,
.Xr ssh-add 1 ,
.Xr ssh-keygen 1 ,
.Xr sshd 8
- (djm) Merge OpenBSD changes: - markus@cvs.openbsd.org 2000/11/06 16:04:56 [channels.c channels.h clientloop.c nchan.c serverloop.c] [session.c ssh.c] agent forwarding and -R for ssh2, based on work from jhuuskon@messi.uku.fi - markus@cvs.openbsd.org 2000/11/06 16:13:27 [ssh.c sshconnect.c sshd.c] do not disabled rhosts(rsa) if server port > 1024; from pekkas@netcore.fi - markus@cvs.openbsd.org 2000/11/06 16:16:35 [sshconnect.c] downgrade client to 1.3 if server is 1.4; help from mdb@juniper.net - markus@cvs.openbsd.org 2000/11/09 18:04:40 [auth1.c] typo; from mouring@pconline.com - markus@cvs.openbsd.org 2000/11/12 12:03:28 [ssh-agent.c] off-by-one when removing a key from the agent - markus@cvs.openbsd.org 2000/11/12 12:50:39 [auth-rh-rsa.c auth2.c authfd.c authfd.h] [authfile.c hostfile.c kex.c kex.h key.c key.h myproposal.h] [readconf.c readconf.h rsa.c rsa.h servconf.c servconf.h ssh-add.c] [ssh-agent.c ssh-keygen.1 ssh-keygen.c ssh.1 ssh.c ssh_config] [sshconnect1.c sshconnect2.c sshd.8 sshd.c sshd_config ssh-dss.c] [ssh-dss.h ssh-rsa.c ssh-rsa.h dsa.c dsa.h] add support for RSA to SSH2. please test. there are now 3 types of keys: RSA1 is used by ssh-1 only, RSA and DSA are used by SSH2. you can use 'ssh-keygen -t rsa -f ssh2_rsa_file' to generate RSA keys for SSH2 and use the RSA keys for hostkeys or for user keys. SSH2 RSA or DSA keys are added to .ssh/authorised_keys2 as before. - (djm) Fix up Makefile and Redhat init script to create RSA host keys - (djm) Change to interim version
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.Sh AUTHORS
.An -nosplit
OpenSSH is a derivative of the original and free ssh 1.2.12 release by
.An Tatu Ylonen .
.An Aaron Campbell , Bob Beck , Markus Friedl , Niels Provos , Theo de Raadt
and
.An Dug Song
removed many bugs, re-added newer features and created OpenSSH.
.An Markus Friedl
contributed the support for SSH protocol versions 1.5 and 2.0.