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GPG-AGENT(1)                   GNU Privacy Guard                  GPG-AGENT(1)



NAME
       gpg-agent - Secret key management for GnuPG

SYNOPSIS
       gpg-agent [--homedir dir] [--options file] [options]
       gpg-agent [--homedir dir] [--options file] [options] --server
       gpg-agent [--homedir dir] [--options file] [options] --daemon [command_line]


DESCRIPTION
       gpg-agent is a daemon to manage secret (private) keys independently from any protocol.  It is used as a backend
       for gpg and gpgsm as well as for a couple of other utilities.


       The usual way to run the agent is from the ~/.xsession file:

         eval $(gpg-agent --daemon)


       If you don't use an X server, you can also put this into your regular startup file ~/.profile or .bash_profile.
       It  is  best  not  to run multiple instance of the gpg-agent, so you should make sure that only one is running:
       gpg-agent uses an environment variable to inform clients about the communication parameters. You can write  the
       content  of  this  environment variable to a file so that you can test for a running agent.  Here is an example
       using Bourne shell syntax:

         gpg-agent --daemon --enable-ssh-support \
                   --write-env-file "${HOME}/.gpg-agent-info"

       This code should only be run once per user session to initially fire up the agent.  In the example the optional
       support for the included Secure Shell agent is enabled and the information about the agent is written to a file
       in the HOME directory.  Note that by running gpg-agent without arguments you  may  test  whether  an  agent  is
       already running; however such a test may lead to a race condition, thus it is not suggested.


       The second script needs to be run for each interactive session:

         if [ -f "${HOME}/.gpg-agent-info" ]; then
           . "${HOME}/.gpg-agent-info"
           export GPG_AGENT_INFO
           export SSH_AUTH_SOCK
           export SSH_AGENT_PID
         fi


       It reads the data out of the file and exports the variables.  If you don't use Secure Shell, you don't need the
       last two export statements.


       You should always add the following lines to your .bashrc or whatever initialization file is used for all shell
       invocations:

         GPG_TTY=$(tty)
         export GPG_TTY


       It  is important that this environment variable always reflects the output of the tty command.  For W32 systems
       this option is not required.

       Please make sure that a proper pinentry program has been installed under the default filename (which is  system
       dependant)  or use the option pinentry-program to specify the full name of that program.  It is often useful to
       install a symbolic link from the actual used pinentry (e.g. '/usr/bin/pinentry-gtk') to the expected one  (e.g.
       '/usr/bin/pinentry').




COMMANDS
       Commands are not distinguished from options except for the fact that only one command is allowed.


       --version
              Print the program version and licensing information.  Not that you can abbreviate this command.


       --help

       -h     Print  a  usage  message  summarizing the most useful command-line options.  Not that you can abbreviate
              this command.


       --dump-options
              Print a list of all available options and commands.  Not that you can abbreviate this command.


       --server
              Run in server mode and wait for commands on the stdin.  The default mode is to create a socket and  lis-
              ten for commands there.


       --daemon [command line]
              Start  the  gpg-agent  as  a  daemon;  that is, detach it from the console and run it in the background.
              Because gpg-agent prints out important information required for further use, a common  way  of  invoking
              gpg-agent  is:  eval  $(gpg-agent --daemon) to setup the environment variables.  The option --write-env-
              file is another way commonly used to do this.  Yet another way is creating a new process as a  child  of
              gpg-agent:  gpg-agent  --daemon  /bin/sh.  This way you get a new shell with the environment setup prop-
              erly; if you exit from this shell, gpg-agent terminates as well.


OPTIONS
       --options file
              Reads configuration from file instead of from the default per-user configuration file.  The default con-
              figuration file is named 'gpg-agent.conf' and expected in the '.gnupg' directory directly below the home
              directory of the user.



       --homedir dir
              Set the name of the home directory to dir. If this option is not used, the home  directory  defaults  to
              '~/.gnupg'.  It is only recognized when given on the command line.  It also overrides any home directory
              stated through the environment variable 'GNUPGHOME' or (on W32 systems) by means of the  Registry  entry
              HKCU\Software\GNU\GnuPG:HomeDir.




       -v

       --verbose
              Outputs  additional information while running.  You can increase the verbosity by giving several verbose
              commands to gpgsm, such as '-vv'.


       -q

       --quiet
              Try to be as quiet as possible.


       --batch
              Don't invoke a pinentry or do any other thing requiring human interaction.


       --faked-system-time epoch
              This option is only useful for testing; it sets the system time back or forth to epoch which is the num-
              ber of seconds elapsed since the year 1970.


       --debug-level level
              Select the debug level for investigating problems. level may be a numeric value or a keyword:


              none   No debugging at all.  A value of less than 1 may be used instead of the keyword.

              basic  Some basic debug messages.  A value between 1 and 2 may be used instead of the keyword.

              advanced
                     More verbose debug messages.  A value between 3 and 5 may be used instead of the keyword.

              expert Even more detailed messages.  A value between 6 and 8 may be used instead of the keyword.

              guru   All of the debug messages you can get. A value greater than 8 may be used instead of the keyword.
                     The creation of hash tracing files is only enabled if the keyword is used.

       How these messages are mapped to the actual debugging flags is not specified and may change with newer releases
       of this program. They are however carefully selected to best aid in debugging.


       --debug flags
              This option is only useful for debugging and the behaviour may change at any time without notice.  FLAGS
              are bit encoded and may be given in usual C-Syntax. The currently defined bits are:


              0 (1)  X.509 or OpenPGP protocol related data

              1 (2)  values of big number integers

              2 (4)  low level crypto operations

              5 (32) memory allocation

              6 (64) caching

              7 (128)
                     show memory statistics.

              9 (512)
                     write hashed data to files named dbgmd-000*

              10 (1024)
                     trace Assuan protocol

              12 (4096)
                     bypass all certificate validation


       --debug-all
              Same as --debug=0xffffffff


       --debug-wait n
              When running in server mode, wait n seconds before entering the actual processing  loop  and  print  the
              pid.  This gives time to attach a debugger.


       --no-detach
              Don't detach the process from the console.  This is mainly useful for debugging.


       -s

       --sh

       -c

       --csh  Format  the  info  output  in  daemon mode for use with the standard Bourne shell or the C-shell respec-
              tively.  The default is to guess it based on the environment variable SHELL which is correct  in  almost
              all cases.


       --write-env-file file
              Often  it is required to connect to the agent from a process not being an inferior of gpg-agent and thus
              the environment variable with the socket name is not available.  To help setting up those  variables  in
              other  sessions,  this  option may be used to write the information into file.  If file is not specified
              the default name '${HOME}/.gpg-agent-info' will be used.  The format is suitable to be  evaluated  by  a
              Bourne shell like in this simple example:

         eval $(cat file)
         eval $(cut -d= -f 1 < file | xargs echo export)




       --no-grab
              Tell  the  pinentry  not  to  grab the keyboard and mouse.  This option should in general not be used to
              avoid X-sniffing attacks.


       --log-file file
              Append all logging output to file.  This is very helpful in seeing what the agent actually does.



       --allow-mark-trusted
              Allow clients to mark keys as trusted, i.e. put them into the 'trustlist.txt' file.  This is by  default
              not allowed to make it harder for users to inadvertently accept Root-CA keys.


       --ignore-cache-for-signing
              This  option  will let gpg-agent bypass the passphrase cache for all signing operation.  Note that there
              is also a per-session option to control this behaviour but this command line option takes precedence.


       --default-cache-ttl n
              Set the time a cache entry is valid to n seconds.  The default is 600 seconds.


       --default-cache-ttl-ssh n
              Set the time a cache entry used for SSH keys is valid to n seconds.  The default is 1800 seconds.


       --max-cache-ttl n
              Set the maximum time a cache entry is valid to n seconds.  After this time a cache entry will be expired
              even if it has been accessed recently.  The default is 2 hours (7200 seconds).


       --max-cache-ttl-ssh n
              Set  the  maximum  time  a cache entry used for SSH keys is valid to n seconds.  After this time a cache
              entry will be expired even if it has been accessed recently.  The default is 2 hours (7200 seconds).


       --enforce-passphrase-constraints
              Enforce the passphrase constraints by not allowing the user to bypass them using the ''Take it  anyway''
              button.


       --min-passphrase-len n
              Set  the minimal length of a passphrase.  When entering a new passphrase shorter than this value a warn-
              ing will be displayed.  Defaults to 8.


       --min-passphrase-nonalpha n
              Set the minimal number of digits or special characters required in a passphrase.  When  entering  a  new
              passphrase  with  less  than  this  number  of digits or special characters a warning will be displayed.
              Defaults to 1.


       --check-passphrase-pattern file
              Check the passphrase against the pattern given in file.  When entering a new passphrase matching one  of
              these  pattern  a warning will be displayed. file should be an absolute filename.  The default is not to
              use any pattern file.

              Security note: It is known that checking a passphrase against a list of pattern or even against  a  com-
              plete  dictionary  is not very effective to enforce good passphrases.  Users will soon figure up ways to
              bypass such a policy.  A better policy is to educate users on good security behavior and  optionally  to
              run a passphrase cracker regularly on all users passphrases to catch the very simple ones.


       --max-passphrase-days n
              Ask  the  user  to  change  the passphrase if n days have passed since the last change.  With --enforce-
              passphrase-constraints set the user may not bypass this check.


       --enable-passphrase-history
              This option does nothing yet.


       --pinentry-program filename
              Use program filename as the PIN entry.  The default is installation dependent and can be shown with  the
              --version command.


       --pinentry-touch-file filename
              By default the filename of the socket gpg-agent is listening for requests is passed to Pinentry, so that
              it can touch that file before exiting (it does this only in curses mode).  This option changes the  file
              passed  to Pinentry to filename.  The special name /dev/null may be used to completely disable this fea-
              ture.  Note that Pinentry will not create that file, it will only change  the  modification  and  access
              time.



       --scdaemon-program filename
              Use  program  filename  as the Smartcard daemon.  The default is installation dependent and can be shown
              with the --version command.


       --disable-scdaemon
              Do not make use of the scdaemon tool.  This option has the effect of disabling the ability to do  smart-
              card operations.  Note, that enabling this option at runtime does not kill an already forked scdaemon.


       --use-standard-socket

       --no-use-standard-socket
              By  enabling  this  option  gpg-agent will listen on the socket named 'S.gpg-agent', located in the home
              directory, and not create a random socket below a temporary directory.  Tools  connecting  to  gpg-agent
              should  first  try  to  connect to the socket given in environment variable GPG_AGENT_INFO and then fall
              back to this socket.  This option may not be used if the home directory is mounted as a remote file sys-
              tem.  Note, that --use-standard-socket is the default on Windows systems.



       --display string

       --ttyname string

       --ttytype string

       --lc-ctype string

       --lc-messages string

       --xauthority string
              These options are used with the server mode to pass localization information.


       --keep-tty

       --keep-display
              Ignore  requests  to change the current tty or X window system's DISPLAY variable respectively.  This is
              useful to lock the pinentry to pop up at the tty or display you started the agent.



       --enable-ssh-support

              Enable emulation of the OpenSSH Agent protocol.

              In this mode of operation, the agent does not only implement the gpg-agent protocol, but also the  agent
              protocol  used  by  OpenSSH (through a separate socket).  Consequently, it should be possible to use the
              gpg-agent as a drop-in replacement for the well known ssh-agent.

              SSH Keys, which are to be used through the agent, need to be added to the  gpg-agent  initially  through
              the  ssh-add  utility.   When a key is added, ssh-add will ask for the password of the provided key file
              and send the unprotected key material to the agent; this causes the gpg-agent to ask for  a  passphrase,
              which  is to be used for encrypting the newly received key and storing it in a gpg-agent specific direc-
              tory.

              Once a key has been added to the gpg-agent this way, the gpg-agent will be ready to use the key.

              Note: in case the gpg-agent receives a signature request, the user might  need  to  be  prompted  for  a
              passphrase,  which  is  necessary  for decrypting the stored key.  Since the ssh-agent protocol does not
              contain a mechanism for telling the agent on which display/terminal it is running, gpg-agent's  ssh-sup-
              port will use the TTY or X display where gpg-agent has been started.  To switch this display to the cur-
              rent one, the following command may be used:

         echo UPDATESTARTUPTTY | gpg-connect-agent




       All the long options may also be given in the configuration file after stripping off the two leading dashes.



EXAMPLES
       The usual way to invoke gpg-agent is

         $ eval $(gpg-agent --daemon)

       An alternative way is by replacing ssh-agent with gpg-agent.  If for example ssh-agent is started  as  part  of
       the Xsession initialization, you may simply replace ssh-agent by a script like:

         #!/bin/sh

         exec /usr/local/bin/gpg-agent --enable-ssh-support --daemon \
               --write-env-file ${HOME}/.gpg-agent-info "$@"


       and add something like (for Bourne shells)

           if [ -f "${HOME}/.gpg-agent-info" ]; then
             . "${HOME}/.gpg-agent-info"
             export GPG_AGENT_INFO
             export SSH_AUTH_SOCK
             export SSH_AGENT_PID
           fi


       to your shell initialization file (e.g. '~/.bashrc').



FILES
       There  are a few configuration files needed for the operation of the agent. By default they may all be found in
       the current home directory (see: [option --homedir]).



       gpg-agent.conf
                This is the standard configuration file read by gpg-agent on
                startup.  It may contain any valid long option; the leading
                two dashes may not be entered and the option may not be abbreviated.
                This file is also read after a SIGHUP however only a few
                options will actually have an effect.  This default name may be
                changed on the command line (see: [option --options]).
                You should backup this file.


       trustlist.txt
                This is the list of trusted keys.  You should backup this file.

                Comment lines, indicated by a leading hash mark, as well as empty
                lines are ignored.  To mark a key as trusted you need to enter its
                fingerprint followed by a space and a capital letter S.  Colons
                may optionally be used to separate the bytes of a fingerprint; this
                allows to cut and paste the fingerprint from a key listing output.  If
                the line is prefixed with a ! the key is explicitly marked as
                not trusted.

                Here is an example where two keys are marked as ultimately trusted
                and one as not trusted:

                .RS 2
                # CN=Wurzel ZS 3,O=Intevation GmbH,C=DE
                A6935DD34EF3087973C706FC311AA2CCF733765B S

                # CN=PCA-1-Verwaltung-02/O=PKI-1-Verwaltung/C=DE
                DC:BD:69:25:48:BD:BB:7E:31:6E:BB:80:D3:00:80:35:D4:F8:A6:CD S

                # CN=Root-CA/O=Schlapphuete/L=Pullach/C=DE
                !14:56:98:D3:FE:9C:CA:5A:31:6E:BC:81:D3:11:4E:00:90:A3:44:C2 S
                .fi

       Before entering a key into this file, you need to ensure its
       authenticity.  How to do this depends on your organisation; your
       administrator might have already entered those keys which are deemed
       trustworthy enough into this file.  Places where to look for the
       fingerprint of a root certificate are letters received from the CA or
       the website of the CA (after making 100% sure that this is indeed the
       website of that CA).  You may want to consider allowing interactive
       updates of this file by using the see: [option --allow-mark-trusted].
       This is however not as secure as maintaining this file manually.  It is
       even advisable to change the permissions to read-only so that this file
       can't be changed inadvertently.

       As a special feature a line include-default will include a global
       list of trusted certificates (e.g. '/etc/gnupg/trustlist.txt').
       This global list is also used if the local list is not available.

       It is possible to add further flags after the S for use by the
       caller:


              relax  Relax checking of some root certificate requirements.  This is for
                     example required if the certificate is missing the basicConstraints
                     attribute (despite that it is a MUST for CA certificates).


              cm     If validation of a certificate finally issued by a CA with this flag set
                     fails, try again using the chain validation model.




       sshcontrol

              This file is used when support for the secure shell agent protocol has
              been enabled (see: [option --enable-ssh-support]). Only keys present in
              this file are used in the SSH protocol.  You should backup this file.

              The ssh-add tool may be used to add new entries to this file;
              you may also add them manually.  Comment lines, indicated by a leading
              hash mark, as well as empty lines are ignored.  An entry starts with
              optional whitespace, followed by the keygrip of the key given as 40 hex
              digits, optionally followed by the caching TTL in seconds and another
              optional field for arbitrary flags.  A non-zero TTL overrides the global
              default as set by --default-cache-ttl-ssh.

              The keygrip may be prefixed with a ! to disable an entry entry.

              The following example lists exactly one key.  Note that keys available
              through a OpenPGP smartcard in the active smartcard reader are
              implicitly added to this list; i.e. there is no need to list them.

                .RS 2
                # Key added on 2005-02-25 15:08:29
                5A6592BF45DC73BD876874A28FD4639282E29B52 0
                .fi


       private-keys-v1.d/

                This is the directory where gpg-agent stores the private keys.  Each
                key is stored in a file with the name made up of the keygrip and the
                suffix 'key'.  You should backup all files in this directory
                and take great care to keep this backup closed away.



              Note that on larger installations, it is useful to put predefined
              files into the directory '/etc/skel/.gnupg/' so that newly created
              users start up with a working configuration.  For existing users the
              a small helper script is provided to create these files (see: [addgnupghome]).





SIGNALS
       A running gpg-agent may be controlled by signals, i.e. using the kill command to send a signal to the  process.

       Here is a list of supported signals:



       SIGHUP This  signal  flushes  all  cached  passphrases and if the program has been started with a configuration
              file, the configuration file is read again.  Only certain options are honored:  quiet,  verbose,  debug,
              debug-all,  debug-level,  no-grab, pinentry-program, default-cache-ttl, max-cache-ttl, ignore-cache-for-
              signing, allow-mark-trusted and disable-scdaemon.  scdaemon-program is also supported  but  due  to  the
              current  implementation,  which  calls the scdaemon only once, it is not of much use unless you manually
              kill the scdaemon.



       SIGTERM
              Shuts down the process but waits until all current requests are fulfilled.  If the process has  received
              3 of these signals and requests are still pending, a shutdown is forced.


       SIGINT Shuts down the process immediately.


       SIGUSR1
              Dump internal information to the log file.


       SIGUSR2
              This signal is used for internal purposes.




SEE ALSO
       gpg2(1), gpgsm(1), gpg-connect-agent(1), scdaemon(1)

       The  full  documentation  for  this  tool is maintained as a Texinfo manual.  If GnuPG and the info program are
       properly installed at your site, the command

         info gnupg

       should give you access to the complete manual including a menu structure and an index.



GnuPG 2.0.14                      2014-06-30                      GPG-AGENT(1)