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SSH-AGENT(1)		    General Commands Manual		  SSH-AGENT(1)

NAME
       ssh-agent - OpenSSH authentication agent

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

DESCRIPTION
       ssh-agent is a program to hold private keys used	for public key authen-
       tication.  Through use of environment variables the agent  can  be  lo-
       cated  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  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 ``sha256''.

       -k     Kill the current agent (given by the  SSH_AGENT_PID  environment
	      variable).

       -P allowed_providers
	      Specify  a pattern-list of acceptable paths for PKCS#11 provider
	      and FIDO authenticator middleware	shared libraries that  may  be
	      used with	the -S or -s options to	ssh-add(1).  Libraries that do
	      not match	the pattern list will be  refused.   See  PATTERNS  in
	      ssh_config(5) for	a description of pattern-list syntax.  The de-
	      fault list 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.

       -x     Exit after the last client has disconnected.

       command [arg...]
	      If a command (and	optional arguments) is given, this is executed
	      as a subprocess of the agent.   The  agent  exits	 automatically
	      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 ex-
       ample 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 us-
       ing ssh-add(1) or by ssh(1) when	 AddKeysToAgent	 is  set  in  ssh_con-
       fig(5).	 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	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 us-
       ing  the	 -A option to ssh(1) (but see the caveats documented therein),
       avoiding	the need for authentication data to be	stored	on  other  ma-
       chines.	 Authentication	passphrases and	private	keys never go over the
       network:	the connection to the agent is forwarded over SSH remote  con-
       nections	and the	result is returned to the requester, allowing the user
       access to their identities anywhere in the network in a secure fashion.

ENVIRONMENT
       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 accessible only  to
	      the  current  user,  but is easily abused	by root	or another in-
	      stance of	the same user.

FILES
       $TMPDIR/ssh-XXXXXXXXXX/agent.<ppid>
	      UNIX-domain sockets used to contain the connection  to  the  au-
	      thentication  agent.   These  sockets should only	be readable by
	      the owner.  The sockets should get  automatically	 removed  when
	      the agent	exits.

SEE ALSO
       ssh(1), ssh-add(1), ssh-keygen(1), ssh_config(5), sshd(8)

AUTHORS
       -nosplit	 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.

				 June 22 2020			  SSH-AGENT(1)

NAME | SYNOPSIS | DESCRIPTION | ENVIRONMENT | FILES | SEE ALSO | AUTHORS

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