Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
SSH-AGENT(1)		  BSD General Commands Manual		  SSH-AGENT(1)

     ssh-agent -- authentication agent

     ssh-agent [-c | -s] [-Ddx]	[-a bind_address] [-E fingerprint_hash]
	       [-P pkcs11_whitelist] [-t life] [command	[arg ...]]
     ssh-agent [-c | -s] -k

     ssh-agent is a program to hold private keys used for public key authenti-
     cation (RSA, DSA, ECDSA, Ed25519).	 ssh-agent is usually 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 ssh(1).

     The agent initially does not have any private keys.  Keys are added using
     ssh(1) (see AddKeysToAgent	in ssh_config(5) for details) or ssh-add(1).
     Multiple identities may be	stored in ssh-agent concurrently and ssh(1)
     will automatically	use them if present.  ssh-add(1) is also used to re-
     move keys from ssh-agent and to query the keys that are held in one.

     The options are as	follows:

     -a	bind_address
	     Bind the agent to the UNIX-domain socket bind_address.  The de-
	     fault 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

     -k	     Kill the current agent (given by the SSH_AGENT_PID	environment

     -P	pkcs11_whitelist
	     Specify a pattern-list of acceptable paths	for PKCS#11 shared li-
	     braries that may be added using the -s option to ssh-add(1).  The
	     default is	to allow loading PKCS#11 libraries from
	     "/usr/lib/*,/usr/local/lib/*".  PKCS#11 libraries that do not
	     match the whitelist will be refused.  See PATTERNS	in
	     ssh_config(5) for a description of	pattern-list syntax.

     -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.

     -x	     Exit after	the last client	has disconnected.

     If	a command line is given, this is executed as a subprocess of the
     agent.  When the command dies, so does the	agent.

     The idea is that the agent	is run in the user's local PC, laptop, or ter-
     minal.  Authentication data need not be stored on any other machine, and
     authentication passphrases	never go over the network.  However, the con-
     nection to	the agent is forwarded over SSH	remote logins, and the user
     can thus use the privileges given by the identities anywhere in the net-
     work in a secure way.

     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 ssh-agent xterm &.  The second is that the agent prints the
     needed shell commands (either sh(1) or csh(1) syntax can be generated)
     which can be evaluated in the calling shell, eg eval `ssh-agent -s` for
     Bourne-type shells	such as	sh(1) or ksh(1)	and eval `ssh-agent -c`	for
     csh(1) and	derivatives.

     Later ssh(1) looks	at these variables and uses them to establish a	con-
     nection to	the agent.

     The agent will never send a private key over its request channel.	In-
     stead, operations that require a private key will be performed by the
     agent, and	the result will	be returned to the requester.  This way, pri-
     vate keys are not exposed to clients using	the agent.

     A UNIX-domain socket is created and the name of this socket is stored in
     the SSH_AUTH_SOCK environment variable.  The socket is made accessible
     only to the current user.	This method is easily abused by	root or	an-
     other instance of the same	user.

     The SSH_AGENT_PID environment variable holds the agent's process ID.

     The agent exits automatically when	the command given on the command line

	     UNIX-domain sockets used to contain the connection	to the authen-
	     tication 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),	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 cre-
     ated OpenSSH.  Markus Friedl contributed the support for SSH protocol
     versions 1.5 and 2.0.

BSD			       November	30, 2016			   BSD


Want to link to this manual page? Use this URL:

home | help