|
NAME | SYNOPSIS | DESCRIPTION | ENVIRONMENT | FILES | SEE ALSO | AUTHORS | COLOPHON |
SSH-AGENT(1) BSD General Commands Manual SSH-AGENT(1)
ssh-agent — OpenSSH authentication agent
ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]
[-P provider_whitelist] [-t life] [command [arg ...]]
ssh-agent [-c | -s] -k
ssh-agent is a program to hold private keys used for public key authen‐
tication. Through use of environment variables the agent can be
located and automatically used for authentication when logging in to
other machines using ssh(1).
The options are as follows:
-a bind_address
Bind the agent to the UNIX-domain socket bind_address. The
default is $TMPDIR/ssh-XXXXXXXXXX/agent.<ppid>.
-c Generate C-shell commands on stdout. This is the default if
SHELL looks like it's a csh style of shell.
-D Foreground mode. When this option is specified ssh-agent will
not fork.
-d Debug mode. When this option is specified ssh-agent will not
fork and will write debug information to standard error.
-E fingerprint_hash
Specifies the hash algorithm used when displaying key finger‐
prints. Valid options are: “md5” and “sha256”. The default is
“sha256”.
-k Kill the current agent (given by the SSH_AGENT_PID environment
variable).
-P provider_whitelist
Specify a pattern-list of acceptable paths for PKCS#11 and FIDO
authenticator shared libraries that may be used with the -S or
-s options to ssh-add(1). Libraries that do not match the
whitelist will be refused. See PATTERNS in ssh_config(5) for a
description of pattern-list syntax. The default whitelist is
“/usr/lib/*,/usr/local/lib/*”.
-s Generate Bourne shell commands on stdout. This is the default
if SHELL does not look like it's a csh style of shell.
-t 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 sshd_config(5). A lifetime
specified for an identity with ssh-add(1) overrides this value.
Without this option the default maximum lifetime is forever.
command [arg ...]
If a command (and optional arguments) is given, this is exe‐
cuted as a subprocess of the agent. The agent exits automati‐
cally when the command given on the command line terminates.
There are two main ways to get an agent set up. The first is at the
start of an X session, where all other windows or programs are started
as children of the ssh-agent program. The agent starts a command under
which its environment variables are exported, for example ssh-agent
xterm &. When the command terminates, so does the agent.
The second method is used for a login session. When ssh-agent is
started, it prints the shell commands required to set its environment
variables, which in turn can be evaluated in the calling shell, for
example eval `ssh-agent -s`.
In both cases, ssh(1) looks at these environment variables and uses
them to establish a connection to the agent.
The agent initially does not have any private keys. Keys are added
using ssh-add(1) or by ssh(1) when AddKeysToAgent is set in
ssh_config(5). Multiple identities may be stored in ssh-agent concur‐
rently and ssh(1) will automatically use them if present. ssh-add(1)
is also used to remove keys from ssh-agent and to query the keys that
are held in one.
Connections to ssh-agent may be forwarded from further remote hosts
using the -A option to ssh(1) (but see the caveats documented therein),
avoiding the need for authentication data to be stored on other
machines. Authentication passphrases and private keys never go over
the network: the connection to the agent is forwarded over SSH remote
connections and the result is returned to the requester, allowing the
user access to their identities anywhere in the network in a secure
fashion.
SSH_AGENT_PID When ssh-agent starts, it stores the name of the agent's
process ID (PID) in this variable.
SSH_AUTH_SOCK When ssh-agent starts, it creates a UNIX-domain socket
and stores its pathname in this variable. It is acces‐
sible only to the current user, but is easily abused by
root or another instance of the same user.
$TMPDIR/ssh-XXXXXXXXXX/agent.<ppid>
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.
ssh(1), ssh-add(1), ssh-keygen(1), ssh_config(5), sshd(8)
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.
This page is part of the openssh (Portable OpenSSH) project. Informa‐
tion about the project can be found at
http://www.openssh.com/portable.html. If you have a bug report for
this manual page, see ⟨http://www.openssh.com/report.html⟩. This page
was obtained from the tarball openssh-8.3p1.tar.gz fetched from
⟨http://ftp.eu.openbsd.org/pub/OpenBSD/OpenSSH/portable/⟩ on
2020-08-13. If you discover any rendering problems in this HTML ver‐
sion of the page, or you believe there is a better or more up-to-date
source for the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original manual
page), send a mail to man-pages@man7.org
BSD December 21, 2019 BSD