f374ba41f5
Release notes are available at https://www.openssh.com/txt/release-9.2 OpenSSH 9.2 contains fixes for two security problems and a memory safety problem. The memory safety problem is not believed to be exploitable. These fixes have already been committed to OpenSSH 9.1 in FreeBSD. Some other notable items from the release notes: * ssh(1): add a new EnableEscapeCommandline ssh_config(5) option that controls whether the client-side ~C escape sequence that provides a command-line is available. Among other things, the ~C command-line could be used to add additional port-forwards at runtime. * sshd(8): add support for channel inactivity timeouts via a new sshd_config(5) ChannelTimeout directive. This allows channels that have not seen traffic in a configurable interval to be automatically closed. Different timeouts may be applied to session, X11, agent and TCP forwarding channels. * sshd(8): add a sshd_config UnusedConnectionTimeout option to terminate client connections that have no open channels for a length of time. This complements the ChannelTimeout option above. * sshd(8): add a -V (version) option to sshd like the ssh client has. * scp(1), sftp(1): add a -X option to both scp(1) and sftp(1) to allow control over some SFTP protocol parameters: the copy buffer length and the number of in-flight requests, both of which are used during upload/download. Previously these could be controlled in sftp(1) only. This makes them available in both SFTP protocol clients using the same option character sequence. * ssh-keyscan(1): allow scanning of complete CIDR address ranges, e.g. "ssh-keyscan 192.168.0.0/24". If a CIDR range is passed, then it will be expanded to all possible addresses in the range including the all-0s and all-1s addresses. bz#976 * ssh(1): support dynamic remote port forwarding in escape command-line's -R processing. bz#3499 MFC after: 1 week Sponsored by: The FreeBSD Foundation
259 lines
7.7 KiB
Groff
259 lines
7.7 KiB
Groff
.\" $OpenBSD: ssh-agent.1,v 1.75 2022/10/07 06:00:58 jmc Exp $
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.\"
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.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
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.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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.\" All rights reserved
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.\"
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.\" As far as I am concerned, the code I have written for this software
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.\" can be used freely for any purpose. Any derived versions of this
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.\" software must be clearly marked as such, and if the derived work is
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.\" incompatible with the protocol description in the RFC file, it must be
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.\" called by a name other than "ssh" or "Secure Shell".
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.\"
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.\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
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.\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
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.\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd $Mdocdate: October 7 2022 $
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.Dt SSH-AGENT 1
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.Os
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.Sh NAME
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.Nm ssh-agent
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.Nd OpenSSH authentication agent
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.Sh SYNOPSIS
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.Nm ssh-agent
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.Op Fl c | s
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.Op Fl \&Ddx
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.Op Fl a Ar bind_address
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.Op Fl E Ar fingerprint_hash
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.Op Fl O Ar option
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.Op Fl P Ar allowed_providers
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.Op Fl t Ar life
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.Nm ssh-agent
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.Op Fl a Ar bind_address
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.Op Fl E Ar fingerprint_hash
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.Op Fl O Ar option
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.Op Fl P Ar allowed_providers
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.Op Fl t Ar life
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.Ar command Op Ar arg ...
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.Nm ssh-agent
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.Op Fl c | s
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.Fl k
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.Sh DESCRIPTION
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.Nm
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is a program to hold private keys used for public key authentication.
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Through use of environment variables the agent can be located
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and automatically used for authentication when logging in to other
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machines using
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.Xr ssh 1 .
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.Pp
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The options are as follows:
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.Bl -tag -width Ds
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.It Fl a Ar bind_address
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Bind the agent to the
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.Ux Ns -domain
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socket
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.Ar bind_address .
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The default is
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.Pa $TMPDIR/ssh-XXXXXXXXXX/agent.\*(Ltppid\*(Gt .
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.It Fl c
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Generate C-shell commands on
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.Dv stdout .
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This is the default if
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.Ev SHELL
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looks like it's a csh style of shell.
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.It Fl D
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Foreground mode.
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When this option is specified,
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.Nm
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will not fork.
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.It Fl d
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Debug mode.
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When this option is specified,
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.Nm
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will not fork and will write debug information to standard error.
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.It Fl E Ar fingerprint_hash
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Specifies the hash algorithm used when displaying key fingerprints.
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Valid options are:
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.Dq md5
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and
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.Dq sha256 .
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The default is
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.Dq sha256 .
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.It Fl k
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Kill the current agent (given by the
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.Ev SSH_AGENT_PID
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environment variable).
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.It Fl O Ar option
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Specify an option when starting
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.Nm .
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Currently only one option is supported:
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.Cm no-restrict-websafe .
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This instructs
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.Nm
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to permit signatures using FIDO keys that might be web authentication
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requests.
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By default,
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.Nm
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refuses signature requests for FIDO keys where the key application string
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does not start with
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.Dq ssh:
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and when the data to be signed does not appear to be a
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.Xr ssh 1
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user authentication request or a
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.Xr ssh-keygen 1
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signature.
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The default behaviour prevents forwarded access to a FIDO key from also
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implicitly forwarding the ability to authenticate to websites.
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.It Fl P Ar allowed_providers
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Specify a pattern-list of acceptable paths for PKCS#11 provider and FIDO
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authenticator middleware shared libraries that may be used with the
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.Fl S
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or
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.Fl s
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options to
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.Xr ssh-add 1 .
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Libraries that do not match the pattern list will be refused.
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See PATTERNS in
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.Xr ssh_config 5
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for a description of pattern-list syntax.
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The default list is
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.Dq /usr/lib/*,/usr/local/lib/* .
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.It Fl s
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Generate Bourne shell commands on
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.Dv stdout .
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This is the default if
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.Ev SHELL
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does not look like it's a csh style of shell.
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.It Fl t Ar life
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Set a default value for the maximum lifetime of identities added to the agent.
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The lifetime may be specified in seconds or in a time format specified in
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.Xr sshd_config 5 .
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A lifetime specified for an identity with
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.Xr ssh-add 1
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overrides this value.
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Without this option the default maximum lifetime is forever.
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.It Fl x
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Exit after the last client has disconnected.
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.It Ar command Op Ar arg ...
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If a command (and optional arguments) is given,
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this is executed as a subprocess of the agent.
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The agent exits automatically when the command given on the command
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line terminates.
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.El
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.Pp
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There are two main ways to get an agent set up.
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The first is at the start of an X session,
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where all other windows or programs are started as children of the
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.Nm
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program.
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The agent starts a command under which its environment
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variables are exported, for example
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.Cm ssh-agent xterm & .
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When the command terminates, so does the agent.
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.Pp
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The second method is used for a login session.
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When
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.Nm
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is started,
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it prints the shell commands required to set its environment variables,
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which in turn can be evaluated in the calling shell, for example
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.Cm eval `ssh-agent -s` .
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.Pp
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In both cases,
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.Xr ssh 1
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looks at these environment variables
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and uses them to establish a connection to the agent.
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.Pp
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The agent initially does not have any private keys.
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Keys are added using
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.Xr ssh-add 1
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or by
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.Xr ssh 1
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when
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.Cm AddKeysToAgent
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is set in
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.Xr ssh_config 5 .
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Multiple identities may be stored in
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.Nm
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concurrently and
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.Xr ssh 1
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will automatically use them if present.
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.Xr ssh-add 1
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is also used to remove keys from
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.Nm
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and to query the keys that are held in one.
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.Pp
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Connections to
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.Nm
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may be forwarded from further remote hosts using the
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.Fl A
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option to
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.Xr ssh 1
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(but see the caveats documented therein),
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avoiding the need for authentication data to be stored on other machines.
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Authentication passphrases and private keys never go over the network:
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the connection to the agent is forwarded over SSH remote connections
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and the result is returned to the requester,
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allowing the user access to their identities anywhere in the network
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in a secure fashion.
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.Sh ENVIRONMENT
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.Bl -tag -width "SSH_AGENT_PID"
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.It Ev SSH_AGENT_PID
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When
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.Nm
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starts, it stores the name of the agent's process ID (PID) in this variable.
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.It Ev SSH_AUTH_SOCK
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When
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.Nm
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starts, it creates a
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.Ux Ns -domain
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socket and stores its pathname in this variable.
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It is accessible only to the current user,
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but is easily abused by root or another instance of the same user.
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.El
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.Sh FILES
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.Bl -tag -width Ds
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.It Pa $TMPDIR/ssh-XXXXXXXXXX/agent.<ppid>
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.Ux Ns -domain
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sockets used to contain the connection to the authentication agent.
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These sockets should only be readable by the owner.
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The sockets should get automatically removed when the agent exits.
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.El
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.Sh SEE ALSO
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.Xr ssh 1 ,
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.Xr ssh-add 1 ,
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.Xr ssh-keygen 1 ,
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.Xr ssh_config 5 ,
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.Xr sshd 8
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.Sh AUTHORS
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.An -nosplit
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OpenSSH is a derivative of the original and free ssh 1.2.12 release by
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.An Tatu Ylonen .
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.An Aaron Campbell , Bob Beck , Markus Friedl , Niels Provos , Theo de Raadt
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and
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.An Dug Song
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removed many bugs, re-added newer features and created OpenSSH.
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.An Markus Friedl
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contributed the support for SSH protocol versions 1.5 and 2.0.
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