1 @c Copyright (C) 2002 Free Software Foundation, Inc.
2 @c This is part of the GnuPG manual.
3 @c For copying conditions, see the file gnupg.texi.
5 @c Note that we use this texinfo file for all versions of GnuPG:
6 @c 2.0 and 2.1. The macro "gpgtwoone" controls parts which are only
7 @c valid for GnuPG 2.1 and later.
10 @node Invoking GPG-AGENT
11 @chapter Invoking GPG-AGENT
12 @cindex GPG-AGENT command options
13 @cindex command options
14 @cindex options, GPG-AGENT command
19 \- Secret key management for GnuPG
50 @command{gpg-agent} is a daemon to manage secret (private) keys
51 independently from any protocol. It is used as a backend for
52 @command{gpg} and @command{gpgsm} as well as for a couple of other
56 The agent is automatically started on demand by @command{gpg},
57 @command{gpgsm}, @command{gpgconf}, or @command{gpg-connect-agent}.
58 Thus there is no reason to start it manually. In case you want to use
59 the included Secure Shell Agent you may start the agent using:
62 gpg-connect-agent /bye
68 The usual way to run the agent is from the @code{~/.xsession} file:
71 eval $(gpg-agent --daemon)
74 If you don't use an X server, you can also put this into your regular
75 startup file @code{~/.profile} or @code{.bash_profile}. It is best not
76 to run multiple instance of the @command{gpg-agent}, so you should make
77 sure that only one is running: @command{gpg-agent} uses an environment
78 variable to inform clients about the communication parameters. You can
79 write the content of this environment variable to a file so that you can
80 test for a running agent. Here is an example using Bourne shell syntax:
83 gpg-agent --daemon --enable-ssh-support \
84 --write-env-file "$@{HOME@}/.gpg-agent-info"
87 This code should only be run once per user session to initially fire up
88 the agent. In the example the optional support for the included Secure
89 Shell agent is enabled and the information about the agent is written to
90 a file in the HOME directory. Note that by running gpg-agent without
91 arguments you may test whether an agent is already running; however such
92 a test may lead to a race condition, thus it is not suggested.
95 The second script needs to be run for each interactive session:
98 if [ -f "$@{HOME@}/.gpg-agent-info" ]; then
99 . "$@{HOME@}/.gpg-agent-info"
100 export GPG_AGENT_INFO
106 It reads the data out of the file and exports the variables. If you
107 don't use Secure Shell, you don't need the last two export statements.
111 You should always add the following lines to your @code{.bashrc} or
112 whatever initialization file is used for all shell invocations:
120 It is important that this environment variable always reflects the
121 output of the @code{tty} command. For W32 systems this option is not
124 Please make sure that a proper pinentry program has been installed
125 under the default filename (which is system dependent) or use the
126 option @option{pinentry-program} to specify the full name of that program.
127 It is often useful to install a symbolic link from the actual used
128 pinentry (e.g. @file{/usr/bin/pinentry-gtk}) to the expected
129 one (e.g. @file{/usr/bin/pinentry}).
133 @xref{Option Index},for an index to @command{GPG-AGENT}'s commands and options.
137 * Agent Commands:: List of all commands.
138 * Agent Options:: List of all options.
139 * Agent Configuration:: Configuration files.
140 * Agent Signals:: Use of some signals.
141 * Agent Examples:: Some usage examples.
142 * Agent Protocol:: The protocol the agent uses.
149 Commands are not distinguished from options except for the fact that
150 only one command is allowed.
155 Print the program version and licensing information. Note that you cannot
156 abbreviate this command.
161 Print a usage message summarizing the most useful command-line options.
162 Note that you cannot abbreviate this command.
165 @opindex dump-options
166 Print a list of all available options and commands. Note that you cannot
167 abbreviate this command.
171 Run in server mode and wait for commands on the @code{stdin}. The
172 default mode is to create a socket and listen for commands there.
174 @item --daemon [@var{command line}]
176 Start the gpg-agent as a daemon; that is, detach it from the console
177 and run it in the background.
179 Because @command{gpg-agent} prints out
180 important information required for further use, a common way of
181 invoking gpg-agent is: @code{eval $(gpg-agent --daemon)} to setup the
182 environment variables. The option @option{--write-env-file} is
183 another way commonly used to do this.
185 Yet another way is creating
186 a new process as a child of gpg-agent: @code{gpg-agent --daemon
187 /bin/sh}. This way you get a new shell with the environment setup
188 properly; if you exit from this shell, gpg-agent terminates as well.
193 @section Option Summary
197 @anchor{option --options}
198 @item --options @var{file}
200 Reads configuration from @var{file} instead of from the default
201 per-user configuration file. The default configuration file is named
202 @file{gpg-agent.conf} and expected in the @file{.gnupg} directory directly
203 below the home directory of the user.
205 @anchor{option --homedir}
206 @include opt-homedir.texi
212 Outputs additional information while running.
213 You can increase the verbosity by giving several
214 verbose commands to @command{gpgsm}, such as @samp{-vv}.
219 Try to be as quiet as possible.
223 Don't invoke a pinentry or do any other thing requiring human interaction.
225 @item --faked-system-time @var{epoch}
226 @opindex faked-system-time
227 This option is only useful for testing; it sets the system time back or
228 forth to @var{epoch} which is the number of seconds elapsed since the year
231 @item --debug-level @var{level}
233 Select the debug level for investigating problems. @var{level} may be
234 a numeric value or a keyword:
238 No debugging at all. A value of less than 1 may be used instead of
241 Some basic debug messages. A value between 1 and 2 may be used
242 instead of the keyword.
244 More verbose debug messages. A value between 3 and 5 may be used
245 instead of the keyword.
247 Even more detailed messages. A value between 6 and 8 may be used
248 instead of the keyword.
250 All of the debug messages you can get. A value greater than 8 may be
251 used instead of the keyword. The creation of hash tracing files is
252 only enabled if the keyword is used.
255 How these messages are mapped to the actual debugging flags is not
256 specified and may change with newer releases of this program. They are
257 however carefully selected to best aid in debugging.
259 @item --debug @var{flags}
261 This option is only useful for debugging and the behaviour may change at
262 any time without notice. FLAGS are bit encoded and may be given in
263 usual C-Syntax. The currently defined bits are:
267 X.509 or OpenPGP protocol related data
269 values of big number integers
271 low level crypto operations
277 show memory statistics.
279 write hashed data to files named @code{dbgmd-000*}
281 trace Assuan protocol
283 bypass all certificate validation
288 Same as @code{--debug=0xffffffff}
290 @item --debug-wait @var{n}
292 When running in server mode, wait @var{n} seconds before entering the
293 actual processing loop and print the pid. This gives time to attach a
296 @item --debug-quick-random
297 @opindex debug-quick-random
298 This option inhibits the use of the very secure random quality level
299 (Libgcrypt’s @code{GCRY_VERY_STRONG_RANDOM}) and degrades all request
300 down to standard random quality. It is only used for testing and
301 shall not be used for any production quality keys. This option is
302 only effective when given on the command line.
306 Don't detach the process from the console. This is mainly useful for
315 Format the info output in daemon mode for use with the standard Bourne
316 shell or the C-shell respectively. The default is to guess it based on
317 the environment variable @code{SHELL} which is correct in almost all
321 @item --write-env-file @var{file}
322 @opindex write-env-file
323 Often it is required to connect to the agent from a process not being an
324 inferior of @command{gpg-agent} and thus the environment variable with
325 the socket name is not available. To help setting up those variables in
326 other sessions, this option may be used to write the information into
327 @var{file}. If @var{file} is not specified the default name
328 @file{$@{HOME@}/.gpg-agent-info} will be used. The format is suitable
329 to be evaluated by a Bourne shell like in this simple example:
332 eval $(cat @var{file})
333 eval $(cut -d= -f 1 < @var{file} | xargs echo export)
340 Tell the pinentry not to grab the keyboard and mouse. This option
341 should in general not be used to avoid X-sniffing attacks.
343 @anchor{option --log-file}
344 @item --log-file @var{file}
346 Append all logging output to @var{file}. This is very helpful in seeing
347 what the agent actually does. If neither a log file nor a log file
348 descriptor has been set on a Windows platform, the Registry entry
349 @code{HKCU\Software\GNU\GnuPG:DefaultLogFile}, if set, is used to specify
353 @anchor{option --no-allow-mark-trusted}
354 @item --no-allow-mark-trusted
355 @opindex no-allow-mark-trusted
356 Do not allow clients to mark keys as trusted, i.e. put them into the
357 @file{trustlist.txt} file. This makes it harder for users to inadvertently
360 @anchor{option --allow-preset-passphrase}
361 @item --allow-preset-passphrase
362 @opindex allow-preset-passphrase
363 This option allows the use of @command{gpg-preset-passphrase} to seed the
364 internal cache of @command{gpg-agent} with passphrases.
367 @anchor{option --allow-loopback-pinentry}
368 @item --allow-loopback-pinentry
369 @opindex allow-loopback-pinentry
370 Allow clients to use the loopback pinentry features; see the option
371 @option{pinentry-mode} for details.
374 @item --ignore-cache-for-signing
375 @opindex ignore-cache-for-signing
376 This option will let @command{gpg-agent} bypass the passphrase cache for all
377 signing operation. Note that there is also a per-session option to
378 control this behaviour but this command line option takes precedence.
380 @item --default-cache-ttl @var{n}
381 @opindex default-cache-ttl
382 Set the time a cache entry is valid to @var{n} seconds. The default is
385 @item --default-cache-ttl-ssh @var{n}
386 @opindex default-cache-ttl
387 Set the time a cache entry used for SSH keys is valid to @var{n}
388 seconds. The default is 1800 seconds.
390 @item --max-cache-ttl @var{n}
391 @opindex max-cache-ttl
392 Set the maximum time a cache entry is valid to @var{n} seconds. After
393 this time a cache entry will be expired even if it has been accessed
394 recently or has been set using @command{gpg-preset-passphrase}. The
395 default is 2 hours (7200 seconds).
397 @item --max-cache-ttl-ssh @var{n}
398 @opindex max-cache-ttl-ssh
399 Set the maximum time a cache entry used for SSH keys is valid to
400 @var{n} seconds. After this time a cache entry will be expired even
401 if it has been accessed recently or has been set using
402 @command{gpg-preset-passphrase}. The default is 2 hours (7200
405 @item --enforce-passphrase-constraints
406 @opindex enforce-passphrase-constraints
407 Enforce the passphrase constraints by not allowing the user to bypass
408 them using the ``Take it anyway'' button.
410 @item --min-passphrase-len @var{n}
411 @opindex min-passphrase-len
412 Set the minimal length of a passphrase. When entering a new passphrase
413 shorter than this value a warning will be displayed. Defaults to 8.
415 @item --min-passphrase-nonalpha @var{n}
416 @opindex min-passphrase-nonalpha
417 Set the minimal number of digits or special characters required in a
418 passphrase. When entering a new passphrase with less than this number
419 of digits or special characters a warning will be displayed. Defaults
422 @item --check-passphrase-pattern @var{file}
423 @opindex check-passphrase-pattern
424 Check the passphrase against the pattern given in @var{file}. When
425 entering a new passphrase matching one of these pattern a warning will
426 be displayed. @var{file} should be an absolute filename. The default is
427 not to use any pattern file.
429 Security note: It is known that checking a passphrase against a list of
430 pattern or even against a complete dictionary is not very effective to
431 enforce good passphrases. Users will soon figure up ways to bypass such
432 a policy. A better policy is to educate users on good security
433 behavior and optionally to run a passphrase cracker regularly on all
434 users passphrases to catch the very simple ones.
436 @item --max-passphrase-days @var{n}
437 @opindex max-passphrase-days
438 Ask the user to change the passphrase if @var{n} days have passed since
439 the last change. With @option{--enforce-passphrase-constraints} set the
440 user may not bypass this check.
442 @item --enable-passphrase-history
443 @opindex enable-passphrase-history
444 This option does nothing yet.
446 @item --pinentry-program @var{filename}
447 @opindex pinentry-program
448 Use program @var{filename} as the PIN entry. The default is
449 installation dependent. With the default configuration the name of
450 the default pinentry is @file{pinentry}; if that file does not exist
451 but a @file{pinentry-basic} exist the latter is used.
453 @item --pinentry-touch-file @var{filename}
454 @opindex pinentry-touch-file
455 By default the filename of the socket gpg-agent is listening for
456 requests is passed to Pinentry, so that it can touch that file before
457 exiting (it does this only in curses mode). This option changes the
458 file passed to Pinentry to @var{filename}. The special name
459 @code{/dev/null} may be used to completely disable this feature. Note
460 that Pinentry will not create that file, it will only change the
461 modification and access time.
464 @item --scdaemon-program @var{filename}
465 @opindex scdaemon-program
466 Use program @var{filename} as the Smartcard daemon. The default is
467 installation dependent and can be shown with the @command{gpgconf}
470 @item --disable-scdaemon
471 @opindex disable-scdaemon
472 Do not make use of the scdaemon tool. This option has the effect of
473 disabling the ability to do smartcard operations. Note, that enabling
474 this option at runtime does not kill an already forked scdaemon.
477 @item --disable-check-own-socket
478 @opindex disable-check-own-socket
479 @command{gpg-agent} employs a periodic self-test to detect a stolen
480 socket. This usually means a second instance of @command{gpg-agent}
481 has taken over the socket and @command{gpg-agent} will then terminate
482 itself. This option may be used to disable this self-test for
486 @item --use-standard-socket
487 @itemx --no-use-standard-socket
488 @itemx --use-standard-socket-p
489 @opindex use-standard-socket
490 @opindex no-use-standard-socket
491 @opindex use-standard-socket-p
493 Since GnuPG 2.1 the standard socket is always used. These options
494 have no more effect. The command @code{gpg-agent
495 --use-standard-socket-p} will thus always return success.
498 By enabling this option @command{gpg-agent} will listen on the socket
499 named @file{S.gpg-agent}, located in the home directory, and not create
500 a random socket below a temporary directory. Tools connecting to
501 @command{gpg-agent} should first try to connect to the socket given in
502 environment variable @var{GPG_AGENT_INFO} and then fall back to this
503 socket. This option may not be used if the home directory is mounted on
504 a remote file system which does not support special files like fifos or
507 Note, that @option{--use-standard-socket} is the default on
510 The default may be changed at build time. It is
511 possible to test at runtime whether the agent has been configured for
512 use with the standard socket by issuing the command @command{gpg-agent
513 --use-standard-socket-p} which returns success if the standard socket
514 option has been enabled.
517 @item --display @var{string}
518 @itemx --ttyname @var{string}
519 @itemx --ttytype @var{string}
520 @itemx --lc-ctype @var{string}
521 @itemx --lc-messages @var{string}
522 @itemx --xauthority @var{string}
529 These options are used with the server mode to pass localization
533 @itemx --keep-display
535 @opindex keep-display
536 Ignore requests to change the current @code{tty} or X window system's
537 @code{DISPLAY} variable respectively. This is useful to lock the
538 pinentry to pop up at the @code{tty} or display you started the agent.
541 @anchor{option --extra-socket}
542 @item --extra-socket @var{name}
543 @opindex extra-socket
544 Also listen on native gpg-agent connections on the given socket. The
545 intended use for this extra socket is to setup a Unix domain socket
546 forwarding from a remote machine to this socket on the local machine.
547 A @command{gpg} running on the remote machine may then connect to the
548 local gpg-agent and use its private keys. This allows to decrypt or
549 sign data on a remote machine without exposing the private keys to the
553 @anchor{option --enable-ssh-support}
554 @item --enable-ssh-support
555 @opindex enable-ssh-support
557 Enable the OpenSSH Agent protocol.
559 In this mode of operation, the agent does not only implement the
560 gpg-agent protocol, but also the agent protocol used by OpenSSH
561 (through a separate socket). Consequently, it should be possible to use
562 the gpg-agent as a drop-in replacement for the well known ssh-agent.
564 SSH Keys, which are to be used through the agent, need to be added to
565 the gpg-agent initially through the ssh-add utility. When a key is
566 added, ssh-add will ask for the password of the provided key file and
567 send the unprotected key material to the agent; this causes the
568 gpg-agent to ask for a passphrase, which is to be used for encrypting
569 the newly received key and storing it in a gpg-agent specific
572 Once a key has been added to the gpg-agent this way, the gpg-agent
573 will be ready to use the key.
575 Note: in case the gpg-agent receives a signature request, the user might
576 need to be prompted for a passphrase, which is necessary for decrypting
577 the stored key. Since the ssh-agent protocol does not contain a
578 mechanism for telling the agent on which display/terminal it is running,
579 gpg-agent's ssh-support will use the TTY or X display where gpg-agent
580 has been started. To switch this display to the current one, the
581 following command may be used:
584 gpg-connect-agent updatestartuptty /bye
587 Although all GnuPG components try to start the gpg-agent as needed, this
588 is not possible for the ssh support because ssh does not know about it.
589 Thus if no GnuPG tool which accesses the agent has been run, there is no
590 guarantee that ssh is able to use gpg-agent for authentication. To fix
591 this you may start gpg-agent if needed using this simple command:
594 gpg-connect-agent /bye
597 Adding the @option{--verbose} shows the progress of starting the agent.
601 All the long options may also be given in the configuration file after
602 stripping off the two leading dashes.
606 @node Agent Configuration
607 @section Configuration
609 There are a few configuration files needed for the operation of the
610 agent. By default they may all be found in the current home directory
611 (@pxref{option --homedir}).
616 @cindex gpg-agent.conf
617 This is the standard configuration file read by @command{gpg-agent} on
618 startup. It may contain any valid long option; the leading
619 two dashes may not be entered and the option may not be abbreviated.
620 This file is also read after a @code{SIGHUP} however only a few
621 options will actually have an effect. This default name may be
622 changed on the command line (@pxref{option --options}).
623 You should backup this file.
626 This is the list of trusted keys. You should backup this file.
628 Comment lines, indicated by a leading hash mark, as well as empty
629 lines are ignored. To mark a key as trusted you need to enter its
630 fingerprint followed by a space and a capital letter @code{S}. Colons
631 may optionally be used to separate the bytes of a fingerprint; this
632 allows to cut and paste the fingerprint from a key listing output. If
633 the line is prefixed with a @code{!} the key is explicitly marked as
636 Here is an example where two keys are marked as ultimately trusted
637 and one as not trusted:
641 # CN=Wurzel ZS 3,O=Intevation GmbH,C=DE
642 A6935DD34EF3087973C706FC311AA2CCF733765B S
644 # CN=PCA-1-Verwaltung-02/O=PKI-1-Verwaltung/C=DE
645 DC:BD:69:25:48:BD:BB:7E:31:6E:BB:80:D3:00:80:35:D4:F8:A6:CD S
647 # CN=Root-CA/O=Schlapphuete/L=Pullach/C=DE
648 !14:56:98:D3:FE:9C:CA:5A:31:6E:BC:81:D3:11:4E:00:90:A3:44:C2 S
652 Before entering a key into this file, you need to ensure its
653 authenticity. How to do this depends on your organisation; your
654 administrator might have already entered those keys which are deemed
655 trustworthy enough into this file. Places where to look for the
656 fingerprint of a root certificate are letters received from the CA or
657 the website of the CA (after making 100% sure that this is indeed the
658 website of that CA). You may want to consider disallowing interactive
659 updates of this file by using the @xref{option --no-allow-mark-trusted}.
660 It might even be advisable to change the permissions to read-only so
661 that this file can't be changed inadvertently.
663 As a special feature a line @code{include-default} will include a global
664 list of trusted certificates (e.g. @file{/etc/gnupg/trustlist.txt}).
665 This global list is also used if the local list is not available.
667 It is possible to add further flags after the @code{S} for use by the
674 Relax checking of some root certificate requirements. As of now this
675 flag allows the use of root certificates with a missing basicConstraints
676 attribute (despite that it is a MUST for CA certificates) and disables
677 CRL checking for the root certificate.
680 If validation of a certificate finally issued by a CA with this flag set
681 fails, try again using the chain validation model.
688 This file is used when support for the secure shell agent protocol has
689 been enabled (@pxref{option --enable-ssh-support}). Only keys present in
690 this file are used in the SSH protocol. You should backup this file.
692 The @command{ssh-add} tool may be used to add new entries to this file;
693 you may also add them manually. Comment lines, indicated by a leading
694 hash mark, as well as empty lines are ignored. An entry starts with
695 optional whitespace, followed by the keygrip of the key given as 40 hex
696 digits, optionally followed by the caching TTL in seconds and another
697 optional field for arbitrary flags. A non-zero TTL overrides the global
698 default as set by @option{--default-cache-ttl-ssh}.
700 The only flag support is @code{confirm}. If this flag is found for a
701 key, each use of the key will pop up a pinentry to confirm the use of
702 that key. The flag is automatically set if a new key was loaded into
703 @code{gpg-agent} using the option @option{-c} of the @code{ssh-add}
706 The keygrip may be prefixed with a @code{!} to disable an entry entry.
708 The following example lists exactly one key. Note that keys available
709 through a OpenPGP smartcard in the active smartcard reader are
710 implicitly added to this list; i.e. there is no need to list them.
714 # Key added on: 2011-07-20 20:38:46
715 # Fingerprint: 5e:8d:c4:ad:e7:af:6e:27:8a:d6:13:e4:79:ad:0b:81
716 34B62F25E277CF13D3C6BCEBFD3F85D08F0A864B 0 confirm
720 @item private-keys-v1.d/
722 This is the directory where gpg-agent stores the private keys. Each
723 key is stored in a file with the name made up of the keygrip and the
724 suffix @file{key}. You should backup all files in this directory
725 and take great care to keep this backup closed away.
730 Note that on larger installations, it is useful to put predefined
731 files into the directory @file{/etc/skel/.gnupg/} so that newly created
732 users start up with a working configuration. For existing users the
733 a small helper script is provided to create these files (@pxref{addgnupghome}).
742 @section Use of some signals.
743 A running @command{gpg-agent} may be controlled by signals, i.e. using
744 the @command{kill} command to send a signal to the process.
746 Here is a list of supported signals:
752 This signal flushes all cached passphrases and if the program has been
753 started with a configuration file, the configuration file is read
754 again. Only certain options are honored: @code{quiet},
755 @code{verbose}, @code{debug}, @code{debug-all}, @code{debug-level},
756 @code{no-grab}, @code{pinentry-program}, @code{default-cache-ttl},
757 @code{max-cache-ttl}, @code{ignore-cache-for-signing},
758 @code{no-allow-mark-trusted}, @code{disable-scdaemon}, and
759 @code{disable-check-own-socket}. @code{scdaemon-program} is also
760 supported but due to the current implementation, which calls the
761 scdaemon only once, it is not of much use unless you manually kill the
767 Shuts down the process but waits until all current requests are
768 fulfilled. If the process has received 3 of these signals and requests
769 are still pending, a shutdown is forced.
773 Shuts down the process immediately.
777 Dump internal information to the log file.
781 This signal is used for internal purposes.
793 It is important to set the GPG_TTY environment variable in
794 your login shell, for example in the @file{~/.bashrc} init script:
798 export GPG_TTY=$(tty)
802 If you enabled the Ssh Agent Support, you also need to tell ssh about
803 it by adding this to your init script:
808 if [ "$@{gnupg_SSH_AUTH_SOCK_by:-0@}" -ne $$ ]; then
809 export SSH_AUTH_SOCK="$@{HOME@}/.gnupg/S.gpg-agent.ssh"
816 The usual way to invoke @command{gpg-agent} is
819 $ eval $(gpg-agent --daemon)
822 An alternative way is by replacing @command{ssh-agent} with
823 @command{gpg-agent}. If for example @command{ssh-agent} is started as
824 part of the Xsession initialization, you may simply replace
825 @command{ssh-agent} by a script like:
831 exec /usr/local/bin/gpg-agent --enable-ssh-support --daemon \
832 --write-env-file $@{HOME@}/.gpg-agent-info "$@@"
837 and add something like (for Bourne shells)
841 if [ -f "$@{HOME@}/.gpg-agent-info" ]; then
842 . "$@{HOME@}/.gpg-agent-info"
843 export GPG_AGENT_INFO
850 to your shell initialization file (e.g. @file{~/.bashrc}).
858 @section Agent's Assuan Protocol
860 Note: this section does only document the protocol, which is used by
861 GnuPG components; it does not deal with the ssh-agent protocol.
864 The @command{gpg-agent} daemon is started on demand by the GnuPG
868 The @command{gpg-agent} should be started by the login shell and set an
869 environment variable to tell clients about the socket to be used.
870 Clients should deny to access an agent with a socket name which does
871 not match its own configuration. An application may choose to start
872 an instance of the gpg-agent if it does not figure that any has been
873 started; it should not do this if a gpg-agent is running but not
874 usable. Because @command{gpg-agent} can only be used in background mode, no
875 special command line option is required to activate the use of the
879 To identify a key we use a thing called keygrip which is the SHA-1 hash
880 of an canonical encoded S-Expression of the public key as used in
881 Libgcrypt. For the purpose of this interface the keygrip is given as a
882 hex string. The advantage of using this and not the hash of a
883 certificate is that it will be possible to use the same keypair for
884 different protocols, thereby saving space on the token used to keep the
888 The @command{gpg-agent} may send status messages during a command or when
889 returning from a command to inform a client about the progress or result of an
890 operation. For example, the @var{INQUIRE_MAXLEN} status message may be sent
891 during a server inquire to inform the client of the maximum usable length of
892 the inquired data (which should not be exceeded).
896 * Agent PKDECRYPT:: Decrypting a session key
897 * Agent PKSIGN:: Signing a Hash
898 * Agent GENKEY:: Generating a Key
899 * Agent IMPORT:: Importing a Secret Key
900 * Agent EXPORT:: Exporting a Secret Key
901 * Agent ISTRUSTED:: Importing a Root Certificate
902 * Agent GET_PASSPHRASE:: Ask for a passphrase
903 * Agent CLEAR_PASSPHRASE:: Expire a cached passphrase
905 * Agent PRESET_PASSPHRASE:: Set a passphrase for a keygrip
907 * Agent GET_CONFIRMATION:: Ask for confirmation
908 * Agent HAVEKEY:: Check whether a key is available
909 * Agent LEARN:: Register a smartcard
910 * Agent PASSWD:: Change a Passphrase
911 * Agent UPDATESTARTUPTTY:: Change the Standard Display
912 * Agent GETEVENTCOUNTER:: Get the Event Counters
913 * Agent GETINFO:: Return information about the process
914 * Agent OPTION:: Set options for the session
917 @node Agent PKDECRYPT
918 @subsection Decrypting a session key
920 The client asks the server to decrypt a session key. The encrypted
921 session key should have all information needed to select the
922 appropriate secret key or to delegate it to a smartcard.
928 Tell the server about the key to be used for decryption. If this is
929 not used, @command{gpg-agent} may try to figure out the key by trying to
930 decrypt the message with each key available.
936 The agent checks whether this command is allowed and then does an
937 INQUIRY to get the ciphertext the client should then send the cipher
941 S: INQUIRE CIPHERTEXT
947 Please note that the server may send status info lines while reading the
948 data lines from the client. The data send is a SPKI like S-Exp with
954 (<param_name1> <mpi>)
956 (<param_namen> <mpi>)))
959 Where algo is a string with the name of the algorithm; see the libgcrypt
960 documentation for a list of valid algorithms. The number and names of
961 the parameters depend on the algorithm. The agent does return an error
962 if there is an inconsistency.
964 If the decryption was successful the decrypted data is returned by
967 Here is an example session:
971 S: INQUIRE CIPHERTEXT
972 C: D (enc-val elg (a 349324324)
973 C: D (b 3F444677CA)))
975 S: # session key follows
977 S: D (value 1234567890ABCDEF0)
978 S: OK descryption successful
982 The “PADDING” status line is only send if gpg-agent can tell what kind
983 of padding is used. As of now only the value 0 is used to indicate
984 that the padding has been removed.
988 @subsection Signing a Hash
990 The client ask the agent to sign a given hash value. A default key
991 will be chosen if no key has been set. To set a key a client first
998 This can be used multiple times to create multiple signature, the list
999 of keys is reset with the next PKSIGN command or a RESET. The server
1000 test whether the key is a valid key to sign something and responds with
1004 SETHASH --hash=<name>|<algo> <hexstring>
1007 The client can use this command to tell the server about the data <hexstring>
1008 (which usually is a hash) to be signed. <algo> is the decimal encoded hash
1009 algorithm number as used by Libgcrypt. Either <algo> or --hash=<name>
1010 must be given. Valid names for <name> are:
1014 The SHA-1 hash algorithm
1016 The SHA-256 hash algorithm
1018 The RIPE-MD160 hash algorithm
1020 The old and broken MD5 hash algorithm
1022 A combined hash algorithm as used by the TLS protocol.
1026 The actual signing is done using
1032 Options are not yet defined, but my later be used to choose among
1033 different algorithms. The agent does then some checks, asks for the
1034 passphrase and as a result the server returns the signature as an SPKI
1035 like S-expression in "D" lines:
1040 (<param_name1> <mpi>)
1042 (<param_namen> <mpi>)))
1046 The operation is affected by the option
1049 OPTION use-cache-for-signing=0|1
1052 The default of @code{1} uses the cache. Setting this option to @code{0}
1053 will lead @command{gpg-agent} to ignore the passphrase cache. Note, that there is
1054 also a global command line option for @command{gpg-agent} to globally disable the
1058 Here is an example session:
1066 S: # I did ask the user whether he really wants to sign
1067 S: # I did ask the user for the passphrase
1069 C: D ABCDEF012345678901234
1071 S: # signature follows
1072 S: D (sig-val rsa (s 45435453654612121212))
1078 @subsection Generating a Key
1080 This is used to create a new keypair and store the secret key inside the
1081 active PSE --- which is in most cases a Soft-PSE. An not yet defined
1082 option allows to choose the storage location. To get the secret key out
1083 of the PSE, a special export tool has to be used.
1087 GENKEY [--no-protection] [--preset] [<cache_nonce>]
1094 Invokes the key generation process and the server will then inquire
1095 on the generation parameters, like:
1099 C: D (genkey (rsa (nbits 1024)))
1103 The format of the key parameters which depends on the algorithm is of
1109 (parameter_name_1 ....)
1111 (parameter_name_n ....)))
1114 If everything succeeds, the server returns the *public key* in a SPKI
1115 like S-Expression like this:
1124 Here is an example session:
1129 C: D (genkey (rsa (nbits 1024)))
1132 S: D (rsa (n 326487324683264) (e 10001)))
1138 The @option{--no-protection} option may be used to prevent prompting for a
1139 passphrase to protect the secret key while leaving the secret key unprotected.
1140 The @option{--preset} option may be used to add the passphrase to the cache
1141 using the default cache parameters.
1143 The @option{--inq-passwd} option may be used to create the key with a
1144 supplied passphrase. When used the agent does an inquiry with the
1145 keyword @code{NEWPASSWD} to retrieve that passphrase. This option
1146 takes precedence over @option{--no-protection}; however if the client
1147 sends a empty (zero-length) passphrase, this is identical to
1148 @option{--no-protection}.
1152 @subsection Importing a Secret Key
1154 This operation is not yet supported by GpgAgent. Specialized tools
1155 are to be used for this.
1157 There is no actual need because we can expect that secret keys
1158 created by a 3rd party are stored on a smartcard. If we have
1159 generated the key ourself, we do not need to import it.
1162 @subsection Export a Secret Key
1166 Should be done by an extra tool.
1168 @node Agent ISTRUSTED
1169 @subsection Importing a Root Certificate
1171 Actually we do not import a Root Cert but provide a way to validate
1172 any piece of data by storing its Hash along with a description and
1173 an identifier in the PSE. Here is the interface description:
1176 ISTRUSTED <fingerprint>
1179 Check whether the OpenPGP primary key or the X.509 certificate with the
1180 given fingerprint is an ultimately trusted key or a trusted Root CA
1181 certificate. The fingerprint should be given as a hexstring (without
1182 any blanks or colons or whatever in between) and may be left padded with
1183 00 in case of an MD5 fingerprint. GPGAgent will answer with:
1189 The key is in the table of trusted keys.
1192 ERR 304 (Not Trusted)
1195 The key is not in this table.
1197 Gpg needs the entire list of trusted keys to maintain the web of
1198 trust; the following command is therefore quite helpful:
1204 GpgAgent returns a list of trusted keys line by line:
1207 S: D 000000001234454556565656677878AF2F1ECCFF P
1208 S: D 340387563485634856435645634856438576457A P
1209 S: D FEDC6532453745367FD83474357495743757435D S
1213 The first item on a line is the hexified fingerprint where MD5
1214 fingerprints are @code{00} padded to the left and the second item is a
1215 flag to indicate the type of key (so that gpg is able to only take care
1216 of PGP keys). P = OpenPGP, S = S/MIME. A client should ignore the rest
1217 of the line, so that we can extend the format in the future.
1219 Finally a client should be able to mark a key as trusted:
1222 MARKTRUSTED @var{fingerprint} "P"|"S"
1225 The server will then pop up a window to ask the user whether she
1226 really trusts this key. For this it will probably ask for a text to
1227 be displayed like this:
1230 S: INQUIRE TRUSTDESC
1231 C: D Do you trust the key with the fingerprint @@FPR@@
1232 C: D bla fasel blurb.
1237 Known sequences with the pattern @@foo@@ are replaced according to this
1242 Format the fingerprint according to gpg rules for a v3 keys.
1244 Format the fingerprint according to gpg rules for a v4 keys.
1246 Choose an appropriate format to format the fingerprint.
1248 Replaced by a single @code{@@}
1251 @node Agent GET_PASSPHRASE
1252 @subsection Ask for a passphrase
1254 This function is usually used to ask for a passphrase to be used for
1255 conventional encryption, but may also be used by programs which need
1256 special handling of passphrases. This command uses a syntax which helps
1257 clients to use the agent with minimum effort.
1260 GET_PASSPHRASE [--data] [--check] [--no-ask] [--repeat[=N]] \
1261 [--qualitybar] @var{cache_id} \
1262 [@var{error_message} @var{prompt} @var{description}]
1265 @var{cache_id} is expected to be a string used to identify a cached
1266 passphrase. Use a @code{X} to bypass the cache. With no other
1267 arguments the agent returns a cached passphrase or an error. By
1268 convention either the hexified fingerprint of the key shall be used for
1269 @var{cache_id} or an arbitrary string prefixed with the name of the
1270 calling application and a colon: Like @code{gpg:somestring}.
1272 @var{error_message} is either a single @code{X} for no error message or
1273 a string to be shown as an error message like (e.g. "invalid
1274 passphrase"). Blanks must be percent escaped or replaced by @code{+}'.
1276 @var{prompt} is either a single @code{X} for a default prompt or the
1277 text to be shown as the prompt. Blanks must be percent escaped or
1278 replaced by @code{+}.
1280 @var{description} is a text shown above the entry field. Blanks must be
1281 percent escaped or replaced by @code{+}.
1283 The agent either returns with an error or with a OK followed by the hex
1284 encoded passphrase. Note that the length of the strings is implicitly
1285 limited by the maximum length of a command. If the option
1286 @option{--data} is used, the passphrase is not returned on the OK line
1287 but by regular data lines; this is the preferred method.
1289 If the option @option{--check} is used, the standard passphrase
1290 constraints checks are applied. A check is not done if the passphrase
1291 has been found in the cache.
1293 If the option @option{--no-ask} is used and the passphrase is not in the
1294 cache the user will not be asked to enter a passphrase but the error
1295 code @code{GPG_ERR_NO_DATA} is returned.
1297 If the option @option{--qualitybar} is used and a minimum passphrase
1298 length has been configured, a visual indication of the entered
1299 passphrase quality is shown.
1302 CLEAR_PASSPHRASE @var{cache_id}
1305 may be used to invalidate the cache entry for a passphrase. The
1306 function returns with OK even when there is no cached passphrase.
1310 @node Agent CLEAR_PASSPHRASE
1311 @subsection Remove a cached passphrase
1313 Use this command to remove a cached passphrase.
1317 CLEAR_PASSPHRASE [--mode=normal] <cache_id>
1320 CLEAR_PASSPHRASE <cache_id>
1325 The @option{--mode=normal} option can be used to clear a @var{cache_id} that
1326 was set by gpg-agent.
1332 @node Agent PRESET_PASSPHRASE
1333 @subsection Set a passphrase for a keygrip
1335 This command adds a passphrase to the cache for the specified @var{keygrip}.
1338 PRESET_PASSPHRASE [--inquire] <string_or_keygrip> <timeout> [<hexstring>]
1341 The passphrase is a hexidecimal string when specified. When not specified, the
1342 passphrase will be retrieved from the pinentry module unless the
1343 @option{--inquire} option was specified in which case the passphrase will be
1344 retrieved from the client.
1346 The @var{timeout} parameter keeps the passphrase cached for the specified
1347 number of seconds. A value of @code{-1} means infinate while @code{0} means
1348 the default (currently only a timeout of -1 is allowed, which means to never
1355 @node Agent GET_CONFIRMATION
1356 @subsection Ask for confirmation
1358 This command may be used to ask for a simple confirmation by
1359 presenting a text and 2 buttons: Okay and Cancel.
1362 GET_CONFIRMATION @var{description}
1365 @var{description}is displayed along with a Okay and Cancel
1366 button. Blanks must be percent escaped or replaced by @code{+}. A
1367 @code{X} may be used to display confirmation dialog with a default
1370 The agent either returns with an error or with a OK. Note, that the
1371 length of @var{description} is implicitly limited by the maximum
1372 length of a command.
1377 @subsection Check whether a key is available
1379 This can be used to see whether a secret key is available. It does
1380 not return any information on whether the key is somehow protected.
1383 HAVEKEY @var{keygrips}
1386 The agent answers either with OK or @code{No_Secret_Key} (208). The
1387 caller may want to check for other error codes as well. More than one
1388 keygrip may be given. In this case the command returns success if at
1389 least one of the keygrips corresponds to an available secret key.
1393 @subsection Register a smartcard
1399 This command is used to register a smartcard. With the --send
1400 option given the certificates are send back.
1404 @subsection Change a Passphrase
1408 PASSWD [--cache-nonce=<c>] [--passwd-nonce=<s>] [--preset] @var{keygrip}
1411 PASSWD @var{keygrip}
1415 This command is used to interactively change the passphrase of the key
1416 identified by the hex string @var{keygrip}.
1419 The @option{--preset} option may be used to add the new passphrase to the
1420 cache using the default cache parameters.
1424 @node Agent UPDATESTARTUPTTY
1425 @subsection Change the standard display
1431 Set the startup TTY and X-DISPLAY variables to the values of this
1432 session. This command is useful to direct future pinentry invocations
1433 to another screen. It is only required because there is no way in the
1434 ssh-agent protocol to convey this information.
1437 @node Agent GETEVENTCOUNTER
1438 @subsection Get the Event Counters
1444 This function return one status line with the current values of the
1445 event counters. The event counters are useful to avoid polling by
1446 delaying a poll until something has changed. The values are decimal
1447 numbers in the range @code{0} to @code{UINT_MAX} and wrapping around to
1448 0. The actual values should not be relied upon; they shall only be used
1451 The currently defined counters are are:
1454 Incremented with any change of any of the other counters.
1456 Incremented for added or removed private keys.
1458 Incremented for changes of the card readers stati.
1462 @subsection Return information about the process
1464 This is a multipurpose function to return a variety of information.
1470 The value of @var{what} specifies the kind of information returned:
1473 Return the version of the program.
1475 Return the process id of the process.
1477 Return the name of the socket used to connect the agent.
1478 @item ssh_socket_name
1479 Return the name of the socket used for SSH connections. If SSH support
1480 has not been enabled the error @code{GPG_ERR_NO_DATA} will be returned.
1484 @subsection Set options for the session
1486 Here is a list of session options which are not yet described with
1487 other commands. The general syntax for an Assuan option is:
1490 OPTION @var{key}=@var{value}
1494 Supported @var{key}s are:
1497 @item agent-awareness
1498 This may be used to tell gpg-agent of which gpg-agent version the
1499 client is aware of. gpg-agent uses this information to enable
1500 features which might break older clients.
1503 Change the session's environment to be used for the
1504 Pinentry. Valid values are:
1508 Delete envvar @var{name}
1510 Set envvar @var{name} to the empty string
1511 @item @var{name}=@var{value}
1512 Set envvar @var{name} to the string @var{value}.
1515 @item use-cache-for-signing
1516 See Assuan command @code{PKSIGN}.
1518 @item allow-pinentry-notify
1519 This does not need any value. It is used to enable the
1520 PINENTRY_LAUNCHED inquiry.
1524 This option is used to change the operation mode of the pinentry. The
1525 following values are defined:
1529 This is the default mode which pops up a pinentry as needed.
1532 Instead of popping up a pinentry, return the error code
1533 @code{GPG_ERR_CANCELED}.
1536 Instead of popping up a pinentry, return the error code
1537 @code{GPG_ERR_NO_PIN_ENTRY}.
1540 Use a loopback pinentry. This fakes a pinentry by using inquiries
1541 back to the caller to ask for a passphrase. This option may only be
1542 set if the agent has been configured for that.
1543 Use the @xref{option --allow-loopback-pinentry}.
1549 @item cache-ttl-opt-preset
1550 This option sets the cache TTL for new entries created by GENKEY and
1551 PASSWD commands when using the @option{--preset} option. It it is not
1552 used a default value is used.
1557 Instead of using the standard S2K count (which is computed on the
1558 fly), the given S2K count is used for new keys or when changing the
1559 passphrase of a key. Values below 65536 are considered to be 0. This
1560 option is valid for the entire session or until reset to 0. This
1561 option is useful if the key is later used on boxes which are either
1562 much slower or faster than the actual box.
1572 @command{gpg-connect-agent}(1),
1573 @command{scdaemon}(1)
1575 @include see-also-note.texi