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Highlights from the release notes are reproduced below. Some security and bug fixes were previously merged into FreeBSD and have been elided. See the upstream release notes for full details (https://www.openssh.com/releasenotes.html). --- Future deprecation notice ========================= OpenSSH plans to remove support for the DSA signature algorithm in early 2025. Potentially-incompatible changes -------------------------------- * sshd(8): the server will now block client addresses that repeatedly fail authentication, repeatedly connect without ever completing authentication or that crash the server. See the discussion of PerSourcePenalties below for more information. Operators of servers that accept connections from many users, or servers that accept connections from addresses behind NAT or proxies may need to consider these settings. * sshd(8): the server has been split into a listener binary, sshd(8), and a per-session binary "sshd-session". This allows for a much smaller listener binary, as it no longer needs to support the SSH protocol. As part of this work, support for disabling privilege separation (which previously required code changes to disable) and disabling re-execution of sshd(8) has been removed. Further separation of sshd-session into additional, minimal binaries is planned for the future. * sshd(8): several log messages have changed. In particular, some log messages will be tagged with as originating from a process named "sshd-session" rather than "sshd". * ssh-keyscan(1): this tool previously emitted comment lines containing the hostname and SSH protocol banner to standard error. This release now emits them to standard output, but adds a new "-q" flag to silence them altogether. * sshd(8): (portable OpenSSH only) sshd will no longer use argv[0] as the PAM service name. A new "PAMServiceName" sshd_config(5) directive allows selecting the service name at runtime. This defaults to "sshd". bz2101 New features ------------ * sshd(8): sshd(8) will now penalise client addresses that, for various reasons, do not successfully complete authentication. This feature is controlled by a new sshd_config(5) PerSourcePenalties option and is on by default. * ssh(8): allow the HostkeyAlgorithms directive to disable the implicit fallback from certificate host key to plain host keys. Portability ----------- * sshd(8): expose SSH_AUTH_INFO_0 always to PAM auth modules unconditionally. The previous behaviour was to expose it only when particular authentication methods were in use. * ssh(1), ssh-agent(8): allow the presence of the WAYLAND_DISPLAY environment variable to enable SSH_ASKPASS, similarly to the X11 DISPLAY environment variable. GHPR479 --- Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D48914 (cherry picked from commit 0fdf8fae8b569bf9fff3b5171e669dcd7cf9c79e) (cherry picked from commit b4bb480ae9294d7e4b375f0ead9ae57517c79ef3) (cherry picked from commit e95979047aec384852102cf8bb1d55278ea77eeb) (cherry picked from commit dcb4ae528d357f34e4a4b4882c2757c67c98e395) Approved by: re (accelerated MFC)
348 lines
10 KiB
Groff
348 lines
10 KiB
Groff
.\" $OpenBSD: ssh-add.1,v 1.87 2024/06/17 08:30:29 djm 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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.\"
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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: June 17 2024 $
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.Dt SSH-ADD 1
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.Os
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.Sh NAME
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.Nm ssh-add
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.Nd adds private key identities to the OpenSSH authentication agent
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.Sh SYNOPSIS
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.Nm ssh-add
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.Op Fl CcDdKkLlqvXx
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.Op Fl E Ar fingerprint_hash
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.Op Fl H Ar hostkey_file
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.Op Fl h Ar destination_constraint
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.Op Fl S Ar provider
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.Op Fl t Ar life
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.Op Ar
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.Nm ssh-add
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.Fl s Ar pkcs11
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.Op Fl Cv
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.Op Ar certificate ...
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.Nm ssh-add
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.Fl e Ar pkcs11
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.Nm ssh-add
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.Fl T
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.Ar pubkey ...
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.Sh DESCRIPTION
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.Nm
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adds private key identities to the authentication agent,
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.Xr ssh-agent 1 .
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When run without arguments, it adds the files
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.Pa ~/.ssh/id_rsa ,
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.Pa ~/.ssh/id_ecdsa ,
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.Pa ~/.ssh/id_ecdsa_sk ,
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.Pa ~/.ssh/id_ed25519
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and
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.Pa ~/.ssh/id_ed25519_sk .
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After loading a private key,
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.Nm
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will try to load corresponding certificate information from the
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filename obtained by appending
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.Pa -cert.pub
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to the name of the private key file.
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Alternative file names can be given on the command line.
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.Pp
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If any file requires a passphrase,
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.Nm
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asks for the passphrase from the user.
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The passphrase is read from the user's tty.
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.Nm
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retries the last passphrase if multiple identity files are given.
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.Pp
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The authentication agent must be running and the
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.Ev SSH_AUTH_SOCK
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environment variable must contain the name of its socket for
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.Nm
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to work.
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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 C
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When loading keys into or deleting keys from the agent, process
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certificates only and skip plain keys.
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.It Fl c
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Indicates that added identities should be subject to confirmation before
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being used for authentication.
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Confirmation is performed by
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.Xr ssh-askpass 1 .
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Successful confirmation is signaled by a zero exit status from
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.Xr ssh-askpass 1 ,
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rather than text entered into the requester.
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.It Fl D
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Deletes all identities from the agent.
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.It Fl d
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Instead of adding identities, removes identities from the agent.
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If
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.Nm
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has been run without arguments, the keys for the default identities and
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their corresponding certificates will be removed.
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Otherwise, the argument list will be interpreted as a list of paths to
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public key files to specify keys and certificates to be removed from the agent.
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If no public key is found at a given path,
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.Nm
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will append
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.Pa .pub
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and retry.
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If the argument list consists of
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.Dq -
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then
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.Nm
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will read public keys to be removed from standard input.
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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 e Ar pkcs11
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Remove keys provided by the PKCS#11 shared library
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.Ar pkcs11 .
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.It Fl H Ar hostkey_file
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Specifies a known hosts file to look up hostkeys when using
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destination-constrained keys via the
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.Fl h
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flag.
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This option may be specified multiple times to allow multiple files to be
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searched.
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If no files are specified,
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.Nm
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will use the default
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.Xr ssh_config 5
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known hosts files:
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.Pa ~/.ssh/known_hosts ,
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.Pa ~/.ssh/known_hosts2 ,
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.Pa /etc/ssh/ssh_known_hosts ,
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and
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.Pa /etc/ssh/ssh_known_hosts2 .
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.It Fl h Ar destination_constraint
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When adding keys, constrain them to be usable only through specific hosts or to
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specific destinations.
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.Pp
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Destination constraints of the form
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.Sq [user@]dest-hostname
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permit use of the key only from the origin host (the one running
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.Xr ssh-agent 1 )
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to the listed destination host, with optional user name.
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.Pp
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Constraints of the form
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.Sq src-hostname>[user@]dst-hostname
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allow a key available on a forwarded
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.Xr ssh-agent 1
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to be used through a particular host (as specified by
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.Sq src-hostname )
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to authenticate to a further host,
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specified by
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.Sq dst-hostname .
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.Pp
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Multiple destination constraints may be added when loading keys.
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When attempting authentication with a key that has destination constraints,
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the whole connection path, including
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.Xr ssh-agent 1
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forwarding, is tested against those constraints and each
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hop must be permitted for the attempt to succeed.
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For example, if key is forwarded to a remote host,
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.Sq host-b ,
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and is attempting authentication to another host,
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.Sq host-c ,
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then the operation will be successful only if
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.Sq host-b
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was permitted from the origin host and the subsequent
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.Sq host-b>host-c
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hop is also permitted by destination constraints.
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.Pp
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Hosts are identified by their host keys, and are looked up from known hosts
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files by
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.Nm .
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Wildcards patterns may be used for hostnames and certificate host
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keys are supported.
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By default, keys added by
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.Nm
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are not destination constrained.
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.Pp
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Destination constraints were added in OpenSSH release 8.9.
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Support in both the remote SSH client and server is required when using
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destination-constrained keys over a forwarded
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.Xr ssh-agent 1
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channel.
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.Pp
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It is also important to note that destination constraints can only be
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enforced by
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.Xr ssh-agent 1
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when a key is used, or when it is forwarded by a
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.Sy cooperating
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.Xr ssh 1 .
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Specifically, it does not prevent an attacker with access to a remote
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.Ev SSH_AUTH_SOCK
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from forwarding it again and using it on a different host (but only to
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a permitted destination).
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.It Fl K
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Load resident keys from a FIDO authenticator.
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.It Fl k
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When loading keys into or deleting keys from the agent, process plain private
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keys only and skip certificates.
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.It Fl L
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Lists public key parameters of all identities currently represented
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by the agent.
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.It Fl l
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Lists fingerprints of all identities currently represented by the agent.
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.It Fl q
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Be quiet after a successful operation.
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.It Fl S Ar provider
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Specifies a path to a library that will be used when adding
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FIDO authenticator-hosted keys, overriding the default of using the
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internal USB HID support.
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.It Fl s Ar pkcs11
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Add keys provided by the PKCS#11 shared library
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.Ar pkcs11 .
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Certificate files may optionally be listed as command-line arguments.
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If these are present, then they will be loaded into the agent using any
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corresponding private keys loaded from the PKCS#11 token.
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.It Fl T Ar pubkey ...
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Tests whether the private keys that correspond to the specified
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.Ar pubkey
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files are usable by performing sign and verify operations on each.
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.It Fl t Ar life
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Set a maximum lifetime when adding identities to an agent.
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The lifetime may be specified in seconds or in a time format
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specified in
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.Xr sshd_config 5 .
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.It Fl v
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Verbose mode.
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Causes
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.Nm
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to print debugging messages about its progress.
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This is helpful in debugging problems.
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Multiple
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.Fl v
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options increase the verbosity.
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The maximum is 3.
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.It Fl X
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Unlock the agent.
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.It Fl x
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Lock the agent with a password.
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.El
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.Sh ENVIRONMENT
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.Bl -tag -width Ds
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.It Ev "DISPLAY", "SSH_ASKPASS" and "SSH_ASKPASS_REQUIRE"
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If
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.Nm
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needs a passphrase, it will read the passphrase from the current
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terminal if it was run from a terminal.
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If
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.Nm
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does not have a terminal associated with it but
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.Ev DISPLAY
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and
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.Ev SSH_ASKPASS
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are set, it will execute the program specified by
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.Ev SSH_ASKPASS
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(by default
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.Dq ssh-askpass )
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and open an X11 window to read the passphrase.
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This is particularly useful when calling
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.Nm
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from a
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.Pa .xsession
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or related script.
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.Pp
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.Ev SSH_ASKPASS_REQUIRE
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allows further control over the use of an askpass program.
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If this variable is set to
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.Dq never
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then
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.Nm
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will never attempt to use one.
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If it is set to
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.Dq prefer ,
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then
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.Nm
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will prefer to use the askpass program instead of the TTY when requesting
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passwords.
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Finally, if the variable is set to
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.Dq force ,
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then the askpass program will be used for all passphrase input regardless
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of whether
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.Ev DISPLAY
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is set.
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.It Ev SSH_AUTH_SOCK
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Identifies the path of a
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.Ux Ns -domain
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socket used to communicate with the agent.
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.It Ev SSH_SK_PROVIDER
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Specifies a path to a library that will be used when loading any
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FIDO authenticator-hosted keys, overriding the default of using
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the built-in USB HID support.
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.El
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.Sh FILES
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.Bl -tag -width Ds -compact
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.It Pa ~/.ssh/id_ecdsa
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.It Pa ~/.ssh/id_ecdsa_sk
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.It Pa ~/.ssh/id_ed25519
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.It Pa ~/.ssh/id_ed25519_sk
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.It Pa ~/.ssh/id_rsa
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Contains the ECDSA, authenticator-hosted ECDSA, Ed25519,
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authenticator-hosted Ed25519 or RSA authentication identity of the user.
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.El
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.Pp
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Identity files should not be readable by anyone but the user.
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Note that
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.Nm
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ignores identity files if they are accessible by others.
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.Sh EXIT STATUS
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Exit status is 0 on success, 1 if the specified command fails,
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and 2 if
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.Nm
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is unable to contact the authentication agent.
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.Sh SEE ALSO
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.Xr ssh 1 ,
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.Xr ssh-agent 1 ,
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.Xr ssh-askpass 1 ,
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.Xr ssh-keygen 1 ,
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.Xr sshd 8
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.Sh AUTHORS
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OpenSSH is a derivative of the original and free
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ssh 1.2.12 release by Tatu Ylonen.
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Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
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Theo de Raadt and Dug Song
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removed many bugs, re-added newer features and
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created OpenSSH.
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Markus Friedl contributed the support for SSH
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protocol versions 1.5 and 2.0.
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