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 usualy started on demand by @command{gpg}, @command{gpgsm},
57 @command{gpgconf} or @command{gpg-connect-agent}. Thus there is no
58 reason to start it manually. In case you want to use the included
59 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 dependant) 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. Because @command{gpg-agent} prints out
178 important information required for further use, a common way of
179 invoking gpg-agent is: @code{eval $(gpg-agent --daemon)} to setup the
180 environment variables. The option @option{--write-env-file} is
181 another way commonly used to do this. Yet another way is creating
182 a new process as a child of gpg-agent: @code{gpg-agent --daemon
183 /bin/sh}. This way you get a new shell with the environment setup
184 properly; if you exit from this shell, gpg-agent terminates as well.
189 @section Option Summary
193 @anchor{option --options}
194 @item --options @var{file}
196 Reads configuration from @var{file} instead of from the default
197 per-user configuration file. The default configuration file is named
198 @file{gpg-agent.conf} and expected in the @file{.gnupg} directory directly
199 below the home directory of the user.
201 @anchor{option --homedir}
202 @include opt-homedir.texi
208 Outputs additional information while running.
209 You can increase the verbosity by giving several
210 verbose commands to @command{gpgsm}, such as @samp{-vv}.
215 Try to be as quiet as possible.
219 Don't invoke a pinentry or do any other thing requiring human interaction.
221 @item --faked-system-time @var{epoch}
222 @opindex faked-system-time
223 This option is only useful for testing; it sets the system time back or
224 forth to @var{epoch} which is the number of seconds elapsed since the year
227 @item --debug-level @var{level}
229 Select the debug level for investigating problems. @var{level} may be
230 a numeric value or a keyword:
234 No debugging at all. A value of less than 1 may be used instead of
237 Some basic debug messages. A value between 1 and 2 may be used
238 instead of the keyword.
240 More verbose debug messages. A value between 3 and 5 may be used
241 instead of the keyword.
243 Even more detailed messages. A value between 6 and 8 may be used
244 instead of the keyword.
246 All of the debug messages you can get. A value greater than 8 may be
247 used instead of the keyword. The creation of hash tracing files is
248 only enabled if the keyword is used.
251 How these messages are mapped to the actual debugging flags is not
252 specified and may change with newer releases of this program. They are
253 however carefully selected to best aid in debugging.
255 @item --debug @var{flags}
257 This option is only useful for debugging and the behaviour may change at
258 any time without notice. FLAGS are bit encoded and may be given in
259 usual C-Syntax. The currently defined bits are:
263 X.509 or OpenPGP protocol related data
265 values of big number integers
267 low level crypto operations
273 show memory statistics.
275 write hashed data to files named @code{dbgmd-000*}
277 trace Assuan protocol
279 bypass all certificate validation
284 Same as @code{--debug=0xffffffff}
286 @item --debug-wait @var{n}
288 When running in server mode, wait @var{n} seconds before entering the
289 actual processing loop and print the pid. This gives time to attach a
294 Don't detach the process from the console. This is mainly useful for
303 Format the info output in daemon mode for use with the standard Bourne
304 shell or the C-shell respectively. The default is to guess it based on
305 the environment variable @code{SHELL} which is correct in almost all
308 @item --write-env-file @var{file}
309 @opindex write-env-file
310 Often it is required to connect to the agent from a process not being an
311 inferior of @command{gpg-agent} and thus the environment variable with
312 the socket name is not available. To help setting up those variables in
313 other sessions, this option may be used to write the information into
314 @var{file}. If @var{file} is not specified the default name
315 @file{$@{HOME@}/.gpg-agent-info} will be used. The format is suitable
316 to be evaluated by a Bourne shell like in this simple example:
319 eval $(cat @var{file})
320 eval $(cut -d= -f 1 < @var{file} | xargs echo export)
327 Tell the pinentry not to grab the keyboard and mouse. This option
328 should in general not be used to avoid X-sniffing attacks.
330 @anchor{option --log-file}
331 @item --log-file @var{file}
333 Append all logging output to @var{file}. This is very helpful in seeing
334 what the agent actually does. If neither a log file nor a log file
335 descriptor has been set on a Windows platform, the Registry entry
336 @code{HKCU\Software\GNU\GnuPG:DefaultLogFile}, if set, is used to specify
340 @anchor{option --allow-mark-trusted}
341 @item --allow-mark-trusted
342 @opindex allow-mark-trusted
343 Allow clients to mark keys as trusted, i.e. put them into the
344 @file{trustlist.txt} file. This is by default not allowed to make it
345 harder for users to inadvertently accept Root-CA keys.
348 @anchor{option --allow-loopback-pinentry}
349 @item --allow-loopback-pinentry
350 @opindex allow-loopback-pinentry
351 Allow clients to use the loopback pinentry features; see the option
352 @option{pinentry-mode} for details.
355 @item --no-allow-external-cache
356 @opindex no-allow-external-cache
357 Tell Pinentry not to enable features which use an external cache for
360 Some desktop environments prefer to unlock all
361 credentials with one master password and may have installed a Pinentry
362 which employs an additional external cache to implement such a policy.
363 By using this option the Pinentry is advised not to make use of such a
364 cache and instead always ask the user for the requested passphrase.
366 @item --ignore-cache-for-signing
367 @opindex ignore-cache-for-signing
368 This option will let @command{gpg-agent} bypass the passphrase cache for all
369 signing operation. Note that there is also a per-session option to
370 control this behaviour but this command line option takes precedence.
372 @item --default-cache-ttl @var{n}
373 @opindex default-cache-ttl
374 Set the time a cache entry is valid to @var{n} seconds. The default is
377 @item --default-cache-ttl-ssh @var{n}
378 @opindex default-cache-ttl
379 Set the time a cache entry used for SSH keys is valid to @var{n}
380 seconds. The default is 1800 seconds.
382 @item --max-cache-ttl @var{n}
383 @opindex max-cache-ttl
384 Set the maximum time a cache entry is valid to @var{n} seconds. After
385 this time a cache entry will be expired even if it has been accessed
386 recently or has been set using @command{gpg-preset-passphrase}. The
387 default is 2 hours (7200 seconds).
389 @item --max-cache-ttl-ssh @var{n}
390 @opindex max-cache-ttl-ssh
391 Set the maximum time a cache entry used for SSH keys is valid to
392 @var{n} seconds. After this time a cache entry will be expired even
393 if it has been accessed recently or has been set using
394 @command{gpg-preset-passphrase}. The default is 2 hours (7200
397 @item --enforce-passphrase-constraints
398 @opindex enforce-passphrase-constraints
399 Enforce the passphrase constraints by not allowing the user to bypass
400 them using the ``Take it anyway'' button.
402 @item --min-passphrase-len @var{n}
403 @opindex min-passphrase-len
404 Set the minimal length of a passphrase. When entering a new passphrase
405 shorter than this value a warning will be displayed. Defaults to 8.
407 @item --min-passphrase-nonalpha @var{n}
408 @opindex min-passphrase-nonalpha
409 Set the minimal number of digits or special characters required in a
410 passphrase. When entering a new passphrase with less than this number
411 of digits or special characters a warning will be displayed. Defaults
414 @item --check-passphrase-pattern @var{file}
415 @opindex check-passphrase-pattern
416 Check the passphrase against the pattern given in @var{file}. When
417 entering a new passphrase matching one of these pattern a warning will
418 be displayed. @var{file} should be an absolute filename. The default is
419 not to use any pattern file.
421 Security note: It is known that checking a passphrase against a list of
422 pattern or even against a complete dictionary is not very effective to
423 enforce good passphrases. Users will soon figure up ways to bypass such
424 a policy. A better policy is to educate users on good security
425 behavior and optionally to run a passphrase cracker regularly on all
426 users passphrases to catch the very simple ones.
428 @item --max-passphrase-days @var{n}
429 @opindex max-passphrase-days
430 Ask the user to change the passphrase if @var{n} days have passed since
431 the last change. With @option{--enforce-passphrase-constraints} set the
432 user may not bypass this check.
434 @item --enable-passphrase-history
435 @opindex enable-passphrase-history
436 This option does nothing yet.
438 @item --pinentry-program @var{filename}
439 @opindex pinentry-program
440 Use program @var{filename} as the PIN entry. The default is installation
443 @item --pinentry-touch-file @var{filename}
444 @opindex pinentry-touch-file
445 By default the filename of the socket gpg-agent is listening for
446 requests is passed to Pinentry, so that it can touch that file before
447 exiting (it does this only in curses mode). This option changes the
448 file passed to Pinentry to @var{filename}. The special name
449 @code{/dev/null} may be used to completely disable this feature. Note
450 that Pinentry will not create that file, it will only change the
451 modification and access time.
454 @item --scdaemon-program @var{filename}
455 @opindex scdaemon-program
456 Use program @var{filename} as the Smartcard daemon. The default is
457 installation dependent and can be shown with the @command{gpgconf}
460 @item --disable-scdaemon
461 @opindex disable-scdaemon
462 Do not make use of the scdaemon tool. This option has the effect of
463 disabling the ability to do smartcard operations. Note, that enabling
464 this option at runtime does not kill an already forked scdaemon.
467 @item --disable-check-own-socket
468 @opindex disable-check-own-socket
469 @command{gpg-agent} employs a periodic self-test to detect a stolen
470 socket. This usually means a second instance of @command{gpg-agent}
471 has taken over the socket and @command{gpg-agent} will then terminate
472 itself. This option may be used to disable this self-test for
476 @item --use-standard-socket
477 @itemx --no-use-standard-socket
478 @opindex use-standard-socket
479 @opindex no-use-standard-socket
480 By enabling this option @command{gpg-agent} will listen on the socket
481 named @file{S.gpg-agent}, located in the home directory, and not create
482 a random socket below a temporary directory. Tools connecting to
483 @command{gpg-agent} should first try to connect to the socket given in
484 environment variable @var{GPG_AGENT_INFO} and then fall back to this
485 socket. This option may not be used if the home directory is mounted on
486 a remote file system which does not support special files like fifos or
489 Note, that @option{--use-standard-socket} is the default on all
490 systems since GnuPG 2.1.
493 Note, that @option{--use-standard-socket} is the default on
496 The default may be changed at build time. It is
497 possible to test at runtime whether the agent has been configured for
498 use with the standard socket by issuing the command @command{gpg-agent
499 --use-standard-socket-p} which returns success if the standard socket
500 option has been enabled.
502 @item --display @var{string}
503 @itemx --ttyname @var{string}
504 @itemx --ttytype @var{string}
505 @itemx --lc-ctype @var{string}
506 @itemx --lc-messages @var{string}
507 @itemx --xauthority @var{string}
514 These options are used with the server mode to pass localization
518 @itemx --keep-display
520 @opindex keep-display
521 Ignore requests to change the current @code{tty} or X window system's
522 @code{DISPLAY} variable respectively. This is useful to lock the
523 pinentry to pop up at the @code{tty} or display you started the agent.
525 @anchor{option --enable-ssh-support}
526 @item --enable-ssh-support
527 @opindex enable-ssh-support
529 Enable the OpenSSH Agent protocol.
531 In this mode of operation, the agent does not only implement the
532 gpg-agent protocol, but also the agent protocol used by OpenSSH
533 (through a separate socket). Consequently, it should be possible to use
534 the gpg-agent as a drop-in replacement for the well known ssh-agent.
536 SSH Keys, which are to be used through the agent, need to be added to
537 the gpg-agent initially through the ssh-add utility. When a key is
538 added, ssh-add will ask for the password of the provided key file and
539 send the unprotected key material to the agent; this causes the
540 gpg-agent to ask for a passphrase, which is to be used for encrypting
541 the newly received key and storing it in a gpg-agent specific
544 Once a key has been added to the gpg-agent this way, the gpg-agent
545 will be ready to use the key.
547 Note: in case the gpg-agent receives a signature request, the user might
548 need to be prompted for a passphrase, which is necessary for decrypting
549 the stored key. Since the ssh-agent protocol does not contain a
550 mechanism for telling the agent on which display/terminal it is running,
551 gpg-agent's ssh-support will use the TTY or X display where gpg-agent
552 has been started. To switch this display to the current one, the
553 following command may be used:
556 gpg-connect-agent updatestartuptty /bye
559 Although all GnuPG components try to start the gpg-agent as needed, this
560 is not possible for the ssh support because ssh does not know about it.
561 Thus if no GnuPG tool which accesses the agent has been run, there is no
562 guarantee that ssh is abale to use gpg-agent for authentication. To fix
563 this you may start gpg-agent if needed using this simple command:
566 gpg-connect-agent /bye
569 Adding the @option{--verbose} shows the progress of starting the agent.
573 All the long options may also be given in the configuration file after
574 stripping off the two leading dashes.
578 @node Agent Configuration
579 @section Configuration
581 There are a few configuration files needed for the operation of the
582 agent. By default they may all be found in the current home directory
583 (@pxref{option --homedir}).
588 @cindex gpg-agent.conf
589 This is the standard configuration file read by @command{gpg-agent} on
590 startup. It may contain any valid long option; the leading
591 two dashes may not be entered and the option may not be abbreviated.
592 This file is also read after a @code{SIGHUP} however only a few
593 options will actually have an effect. This default name may be
594 changed on the command line (@pxref{option --options}).
595 You should backup this file.
598 This is the list of trusted keys. You should backup this file.
600 Comment lines, indicated by a leading hash mark, as well as empty
601 lines are ignored. To mark a key as trusted you need to enter its
602 fingerprint followed by a space and a capital letter @code{S}. Colons
603 may optionally be used to separate the bytes of a fingerprint; this
604 allows to cut and paste the fingerprint from a key listing output. If
605 the line is prefixed with a @code{!} the key is explicitly marked as
608 Here is an example where two keys are marked as ultimately trusted
609 and one as not trusted:
612 # CN=Wurzel ZS 3,O=Intevation GmbH,C=DE
613 A6935DD34EF3087973C706FC311AA2CCF733765B S
615 # CN=PCA-1-Verwaltung-02/O=PKI-1-Verwaltung/C=DE
616 DC:BD:69:25:48:BD:BB:7E:31:6E:BB:80:D3:00:80:35:D4:F8:A6:CD S
618 # CN=Root-CA/O=Schlapphuete/L=Pullach/C=DE
619 !14:56:98:D3:FE:9C:CA:5A:31:6E:BC:81:D3:11:4E:00:90:A3:44:C2 S
622 Before entering a key into this file, you need to ensure its
623 authenticity. How to do this depends on your organisation; your
624 administrator might have already entered those keys which are deemed
625 trustworthy enough into this file. Places where to look for the
626 fingerprint of a root certificate are letters received from the CA or
627 the website of the CA (after making 100% sure that this is indeed the
628 website of that CA). You may want to consider allowing interactive
629 updates of this file by using the @xref{option --allow-mark-trusted}.
630 This is however not as secure as maintaining this file manually. It is
631 even advisable to change the permissions to read-only so that this file
632 can't be changed inadvertently.
634 As a special feature a line @code{include-default} will include a global
635 list of trusted certificates (e.g. @file{/etc/gnupg/trustlist.txt}).
636 This global list is also used if the local list is not available.
638 It is possible to add further flags after the @code{S} for use by the
645 Relax checking of some root certificate requirements. As of now this
646 flag allows the use of root certificates with a missing basicConstraints
647 attribute (despite that it is a MUST for CA certificates) and disables
648 CRL checking for the root certificate.
651 If validation of a certificate finally issued by a CA with this flag set
652 fails, try again using the chain validation model.
659 This file is used when support for the secure shell agent protocol has
660 been enabled (@pxref{option --enable-ssh-support}). Only keys present in
661 this file are used in the SSH protocol. You should backup this file.
663 The @command{ssh-add} tool may be used to add new entries to this file;
664 you may also add them manually. Comment lines, indicated by a leading
665 hash mark, as well as empty lines are ignored. An entry starts with
666 optional whitespace, followed by the keygrip of the key given as 40 hex
667 digits, optionally followed by the caching TTL in seconds and another
668 optional field for arbitrary flags. A non-zero TTL overrides the global
669 default as set by @option{--default-cache-ttl-ssh}.
671 The only flag support is @code{confirm}. If this flag is found for a
672 key, each use of the key will pop up a pinentry to confirm the use of
673 that key. The flag is automatically set if a new key was loaded into
674 @code{gpg-agent} using the option @option{-c} of the @code{ssh-add}
677 The keygrip may be prefixed with a @code{!} to disable an entry entry.
679 The following example lists exactly one key. Note that keys available
680 through a OpenPGP smartcard in the active smartcard reader are
681 implicitly added to this list; i.e. there is no need to list them.
684 # Key added on: 2011-07-20 20:38:46
685 # Fingerprint: 5e:8d:c4:ad:e7:af:6e:27:8a:d6:13:e4:79:ad:0b:81
686 34B62F25E277CF13D3C6BCEBFD3F85D08F0A864B 0 confirm
689 @item private-keys-v1.d/
691 This is the directory where gpg-agent stores the private keys. Each
692 key is stored in a file with the name made up of the keygrip and the
693 suffix @file{key}. You should backup all files in this directory
694 and take great care to keep this backup closed away.
699 Note that on larger installations, it is useful to put predefined
700 files into the directory @file{/etc/skel/.gnupg/} so that newly created
701 users start up with a working configuration. For existing users the
702 a small helper script is provided to create these files (@pxref{addgnupghome}).
711 @section Use of some signals.
712 A running @command{gpg-agent} may be controlled by signals, i.e. using
713 the @command{kill} command to send a signal to the process.
715 Here is a list of supported signals:
721 This signal flushes all cached passphrases and if the program has been
722 started with a configuration file, the configuration file is read
723 again. Only certain options are honored: @code{quiet},
724 @code{verbose}, @code{debug}, @code{debug-all}, @code{debug-level},
725 @code{no-grab}, @code{pinentry-program}, @code{default-cache-ttl},
726 @code{max-cache-ttl}, @code{ignore-cache-for-signing},
727 @code{no-allow-external-cache},
728 @code{allow-mark-trusted}, @code{disable-scdaemon}, and
729 @code{disable-check-own-socket}. @code{scdaemon-program} is also
730 supported but due to the current implementation, which calls the
731 scdaemon only once, it is not of much use unless you manually kill the
737 Shuts down the process but waits until all current requests are
738 fulfilled. If the process has received 3 of these signals and requests
739 are still pending, a shutdown is forced.
743 Shuts down the process immediately.
747 Dump internal information to the log file.
751 This signal is used for internal purposes.
762 The usual way to invoke @command{gpg-agent} is
765 $ eval $(gpg-agent --daemon)
768 An alternative way is by replacing @command{ssh-agent} with
769 @command{gpg-agent}. If for example @command{ssh-agent} is started as
770 part of the Xsession initialization, you may simply replace
771 @command{ssh-agent} by a script like:
777 exec /usr/local/bin/gpg-agent --enable-ssh-support --daemon \
778 --write-env-file $@{HOME@}/.gpg-agent-info "$@@"
783 and add something like (for Bourne shells)
787 if [ -f "$@{HOME@}/.gpg-agent-info" ]; then
788 . "$@{HOME@}/.gpg-agent-info"
789 export GPG_AGENT_INFO
796 to your shell initialization file (e.g. @file{~/.bashrc}).
803 @section Agent's Assuan Protocol
805 Note: this section does only document the protocol, which is used by
806 GnuPG components; it does not deal with the ssh-agent protocol.
808 The @command{gpg-agent} should be started by the login shell and set an
809 environment variable to tell clients about the socket to be used.
810 Clients should deny to access an agent with a socket name which does
811 not match its own configuration. An application may choose to start
812 an instance of the gpgagent if it does not figure that any has been
813 started; it should not do this if a gpgagent is running but not
814 usable. Because @command{gpg-agent} can only be used in background mode, no
815 special command line option is required to activate the use of the
818 To identify a key we use a thing called keygrip which is the SHA-1 hash
819 of an canonical encoded S-Expression of the public key as used in
820 Libgcrypt. For the purpose of this interface the keygrip is given as a
821 hex string. The advantage of using this and not the hash of a
822 certificate is that it will be possible to use the same keypair for
823 different protocols, thereby saving space on the token used to keep the
827 The @command{gpg-agent} may send status messages during a command or when
828 returning from a command to inform a client about the progress or result of an
829 operation. For example, the @var{INQUIRE_MAXLEN} status message may be sent
830 during a server inquire to inform the client of the maximum usable length of
831 the inquired data (which should not be exceeded).
835 * Agent PKDECRYPT:: Decrypting a session key
836 * Agent PKSIGN:: Signing a Hash
837 * Agent GENKEY:: Generating a Key
838 * Agent IMPORT:: Importing a Secret Key
839 * Agent EXPORT:: Exporting a Secret Key
840 * Agent ISTRUSTED:: Importing a Root Certificate
841 * Agent GET_PASSPHRASE:: Ask for a passphrase
842 * Agent CLEAR_PASSPHRASE:: Expire a cached passphrase
844 * Agent PRESET_PASSPHRASE:: Set a passphrase for a keygrip
846 * Agent GET_CONFIRMATION:: Ask for confirmation
847 * Agent HAVEKEY:: Check whether a key is available
848 * Agent LEARN:: Register a smartcard
849 * Agent PASSWD:: Change a Passphrase
850 * Agent UPDATESTARTUPTTY:: Change the Standard Display
851 * Agent GETEVENTCOUNTER:: Get the Event Counters
852 * Agent GETINFO:: Return information about the process
853 * Agent OPTION:: Set options for the session
856 @node Agent PKDECRYPT
857 @subsection Decrypting a session key
859 The client asks the server to decrypt a session key. The encrypted
860 session key should have all information needed to select the
861 appropriate secret key or to delegate it to a smartcard.
867 Tell the server about the key to be used for decryption. If this is
868 not used, @command{gpg-agent} may try to figure out the key by trying to
869 decrypt the message with each key available.
875 The agent checks whether this command is allowed and then does an
876 INQUIRY to get the ciphertext the client should then send the cipher
880 S: INQUIRE CIPHERTEXT
886 Please note that the server may send status info lines while reading the
887 data lines from the client. The data send is a SPKI like S-Exp with
893 (<param_name1> <mpi>)
895 (<param_namen> <mpi>)))
898 Where algo is a string with the name of the algorithm; see the libgcrypt
899 documentation for a list of valid algorithms. The number and names of
900 the parameters depend on the algorithm. The agent does return an error
901 if there is an inconsistency.
903 If the decryption was successful the decrypted data is returned by
906 Here is an example session:
910 S: INQUIRE CIPHERTEXT
911 C: D (enc-val elg (a 349324324)
912 C: D (b 3F444677CA)))
914 S: # session key follows
916 S: D (value 1234567890ABCDEF0)
917 S: OK descryption successful
920 The “PADDING” status line is only send if gpg-agent can tell what kind
921 of padding is used. As of now only the value 0 is used to indicate
922 that the padding has been removed.
926 @subsection Signing a Hash
928 The client ask the agent to sign a given hash value. A default key
929 will be chosen if no key has been set. To set a key a client first
936 This can be used multiple times to create multiple signature, the list
937 of keys is reset with the next PKSIGN command or a RESET. The server
938 test whether the key is a valid key to sign something and responds with
942 SETHASH --hash=<name>|<algo> <hexstring>
945 The client can use this command to tell the server about the data <hexstring>
946 (which usually is a hash) to be signed. <algo> is the decimal encoded hash
947 algorithm number as used by Libgcrypt. Either <algo> or --hash=<name>
948 must be given. Valid names for <name> are:
959 The actual signing is done using
965 Options are not yet defined, but my later be used to choose among
966 different algorithms. The agent does then some checks, asks for the
967 passphrase and as a result the server returns the signature as an SPKI
968 like S-expression in "D" lines:
973 (<param_name1> <mpi>)
975 (<param_namen> <mpi>)))
979 The operation is affected by the option
982 OPTION use-cache-for-signing=0|1
985 The default of @code{1} uses the cache. Setting this option to @code{0}
986 will lead @command{gpg-agent} to ignore the passphrase cache. Note, that there is
987 also a global command line option for @command{gpg-agent} to globally disable the
991 Here is an example session:
999 S: # I did ask the user whether he really wants to sign
1000 S: # I did ask the user for the passphrase
1002 C: D ABCDEF012345678901234
1004 S: # signature follows
1005 S: D (sig-val rsa (s 45435453654612121212))
1011 @subsection Generating a Key
1013 This is used to create a new keypair and store the secret key inside the
1014 active PSE --- which is in most cases a Soft-PSE. An not yet defined
1015 option allows to choose the storage location. To get the secret key out
1016 of the PSE, a special export tool has to be used.
1020 GENKEY [--no-protection] [--preset] [<cache_nonce>]
1027 Invokes the key generation process and the server will then inquire
1028 on the generation parameters, like:
1032 C: D (genkey (rsa (nbits 1024)))
1036 The format of the key parameters which depends on the algorithm is of
1042 (parameter_name_1 ....)
1044 (parameter_name_n ....)))
1047 If everything succeeds, the server returns the *public key* in a SPKI
1048 like S-Expression like this:
1057 Here is an example session:
1062 C: D (genkey (rsa (nbits 1024)))
1065 S: D (rsa (n 326487324683264) (e 10001)))
1070 The @option{--no-protection} option may be used to prevent prompting for a
1071 passphrase to protect the secret key while leaving the secret key unprotected.
1072 The @option{--preset} option may be used to add the passphrase to the cache
1073 using the default cache parameters.
1077 @subsection Importing a Secret Key
1079 This operation is not yet supported by GpgAgent. Specialized tools
1080 are to be used for this.
1082 There is no actual need because we can expect that secret keys
1083 created by a 3rd party are stored on a smartcard. If we have
1084 generated the key ourself, we do not need to import it.
1087 @subsection Export a Secret Key
1091 Should be done by an extra tool.
1093 @node Agent ISTRUSTED
1094 @subsection Importing a Root Certificate
1096 Actually we do not import a Root Cert but provide a way to validate
1097 any piece of data by storing its Hash along with a description and
1098 an identifier in the PSE. Here is the interface description:
1101 ISTRUSTED <fingerprint>
1104 Check whether the OpenPGP primary key or the X.509 certificate with the
1105 given fingerprint is an ultimately trusted key or a trusted Root CA
1106 certificate. The fingerprint should be given as a hexstring (without
1107 any blanks or colons or whatever in between) and may be left padded with
1108 00 in case of an MD5 fingerprint. GPGAgent will answer with:
1114 The key is in the table of trusted keys.
1117 ERR 304 (Not Trusted)
1120 The key is not in this table.
1122 Gpg needs the entire list of trusted keys to maintain the web of
1123 trust; the following command is therefore quite helpful:
1129 GpgAgent returns a list of trusted keys line by line:
1132 S: D 000000001234454556565656677878AF2F1ECCFF P
1133 S: D 340387563485634856435645634856438576457A P
1134 S: D FEDC6532453745367FD83474357495743757435D S
1138 The first item on a line is the hexified fingerprint where MD5
1139 fingerprints are @code{00} padded to the left and the second item is a
1140 flag to indicate the type of key (so that gpg is able to only take care
1141 of PGP keys). P = OpenPGP, S = S/MIME. A client should ignore the rest
1142 of the line, so that we can extend the format in the future.
1144 Finally a client should be able to mark a key as trusted:
1147 MARKTRUSTED @var{fingerprint} "P"|"S"
1150 The server will then pop up a window to ask the user whether she
1151 really trusts this key. For this it will probably ask for a text to
1152 be displayed like this:
1155 S: INQUIRE TRUSTDESC
1156 C: D Do you trust the key with the fingerprint @@FPR@@
1157 C: D bla fasel blurb.
1162 Known sequences with the pattern @@foo@@ are replaced according to this
1167 Format the fingerprint according to gpg rules for a v3 keys.
1169 Format the fingerprint according to gpg rules for a v4 keys.
1171 Choose an appropriate format to format the fingerprint.
1173 Replaced by a single @code{@@}
1176 @node Agent GET_PASSPHRASE
1177 @subsection Ask for a passphrase
1179 This function is usually used to ask for a passphrase to be used for
1180 conventional encryption, but may also be used by programs which need
1181 special handling of passphrases. This command uses a syntax which helps
1182 clients to use the agent with minimum effort.
1185 GET_PASSPHRASE [--data] [--check] [--no-ask] [--repeat[=N]] [--qualitybar] @var{cache_id} [@var{error_message} @var{prompt} @var{description}]
1188 @var{cache_id} is expected to be a string used to identify a cached
1189 passphrase. Use a @code{X} to bypass the cache. With no other
1190 arguments the agent returns a cached passphrase or an error. By
1191 convention either the hexified fingerprint of the key shall be used for
1192 @var{cache_id} or an arbitrary string prefixed with the name of the
1193 calling application and a colon: Like @code{gpg:somestring}.
1195 @var{error_message} is either a single @code{X} for no error message or
1196 a string to be shown as an error message like (e.g. "invalid
1197 passphrase"). Blanks must be percent escaped or replaced by @code{+}'.
1199 @var{prompt} is either a single @code{X} for a default prompt or the
1200 text to be shown as the prompt. Blanks must be percent escaped or
1201 replaced by @code{+}.
1203 @var{description} is a text shown above the entry field. Blanks must be
1204 percent escaped or replaced by @code{+}.
1206 The agent either returns with an error or with a OK followed by the hex
1207 encoded passphrase. Note that the length of the strings is implicitly
1208 limited by the maximum length of a command. If the option
1209 @option{--data} is used, the passphrase is not returned on the OK line
1210 but by regular data lines; this is the preferred method.
1212 If the option @option{--check} is used, the standard passphrase
1213 constraints checks are applied. A check is not done if the passphrase
1214 has been found in the cache.
1216 If the option @option{--no-ask} is used and the passphrase is not in the
1217 cache the user will not be asked to enter a passphrase but the error
1218 code @code{GPG_ERR_NO_DATA} is returned.
1220 If the option @option{--qualitybar} is used and a minimum passphrase
1221 length has been configured, a visual indication of the entered
1222 passphrase quality is shown.
1225 CLEAR_PASSPHRASE @var{cache_id}
1228 may be used to invalidate the cache entry for a passphrase. The
1229 function returns with OK even when there is no cached passphrase.
1233 @node Agent CLEAR_PASSPHRASE
1234 @subsection Remove a cached passphrase
1236 Use this command to remove a cached passphrase.
1240 CLEAR_PASSPHRASE [--mode=normal] <cache_id>
1243 CLEAR_PASSPHRASE <cache_id>
1248 The @option{--mode=normal} option can be used to clear a @var{cache_id} that
1249 was set by gpg-agent.
1255 @node Agent PRESET_PASSPHRASE
1256 @subsection Set a passphrase for a keygrip
1258 This command adds a passphrase to the cache for the specified @var{keygrip}.
1261 PRESET_PASSPHRASE [--inquire] <string_or_keygrip> <timeout> [<hexstring>]
1264 The passphrase is a hexidecimal string when specified. When not specified, the
1265 passphrase will be retrieved from the pinentry module unless the
1266 @option{--inquire} option was specified in which case the passphrase will be
1267 retrieved from the client.
1269 The @var{timeout} parameter keeps the passphrase cached for the specified
1270 number of seconds. A value of @code{-1} means infinate while @code{0} means
1271 the default (currently only a timeout of -1 is allowed, which means to never
1278 @node Agent GET_CONFIRMATION
1279 @subsection Ask for confirmation
1281 This command may be used to ask for a simple confirmation by
1282 presenting a text and 2 buttons: Okay and Cancel.
1285 GET_CONFIRMATION @var{description}
1288 @var{description}is displayed along with a Okay and Cancel
1289 button. Blanks must be percent escaped or replaced by @code{+}. A
1290 @code{X} may be used to display confirmation dialog with a default
1293 The agent either returns with an error or with a OK. Note, that the
1294 length of @var{description} is implicitly limited by the maximum
1295 length of a command.
1300 @subsection Check whether a key is available
1302 This can be used to see whether a secret key is available. It does
1303 not return any information on whether the key is somehow protected.
1306 HAVEKEY @var{keygrips}
1309 The agent answers either with OK or @code{No_Secret_Key} (208). The
1310 caller may want to check for other error codes as well. More than one
1311 keygrip may be given. In this case the command returns success if at
1312 least one of the keygrips corresponds to an available secret key.
1316 @subsection Register a smartcard
1322 This command is used to register a smartcard. With the --send
1323 option given the certificates are send back.
1327 @subsection Change a Passphrase
1331 PASSWD [--cache-nonce=<c>] [--passwd-nonce=<s>] [--preset] @var{keygrip}
1334 PASSWD @var{keygrip}
1338 This command is used to interactively change the passphrase of the key
1339 identified by the hex string @var{keygrip}.
1342 The @option{--preset} option may be used to add the new passphrase to the
1343 cache using the default cache parameters.
1347 @node Agent UPDATESTARTUPTTY
1348 @subsection Change the standard display
1354 Set the startup TTY and X-DISPLAY variables to the values of this
1355 session. This command is useful to direct future pinentry invocations
1356 to another screen. It is only required because there is no way in the
1357 ssh-agent protocol to convey this information.
1360 @node Agent GETEVENTCOUNTER
1361 @subsection Get the Event Counters
1367 This function return one status line with the current values of the
1368 event counters. The event counters are useful to avoid polling by
1369 delaying a poll until something has changed. The values are decimal
1370 numbers in the range @code{0} to @code{UINT_MAX} and wrapping around to
1371 0. The actual values should not be relied upon; they shall only be used
1374 The currently defined counters are are:
1377 Incremented with any change of any of the other counters.
1379 Incremented for added or removed private keys.
1381 Incremented for changes of the card readers stati.
1385 @subsection Return information about the process
1387 This is a multipurpose function to return a variety of information.
1393 The value of @var{what} specifies the kind of information returned:
1396 Return the version of the program.
1398 Return the process id of the process.
1400 Return the name of the socket used to connect the agent.
1401 @item ssh_socket_name
1402 Return the name of the socket used for SSH connections. If SSH support
1403 has not been enabled the error @code{GPG_ERR_NO_DATA} will be returned.
1407 @subsection Set options for the session
1409 Here is a list of session options which are not yet described with
1410 other commands. The general syntax for an Assuan option is:
1413 OPTION @var{key}=@var{value}
1417 Supported @var{key}s are:
1420 @item agent-awareness
1421 This may be used to tell gpg-agent of which gpg-agent version the
1422 client is aware of. gpg-agent uses this information to enable
1423 features which might break older clients.
1426 Change the session's environment to be used for the
1427 Pinentry. Valid values are:
1431 Delete envvar @var{name}
1433 Set envvar @var{name} to the empty string
1434 @item @var{name}=@var{value}
1435 Set envvar @var{name} to the string @var{value}.
1438 @item use-cache-for-signing
1439 See Assuan command @code{PKSIGN}.
1441 @item allow-pinentry-notify
1442 This does not need any value. It is used to enable the
1443 PINENTRY_LAUNCHED inquiry.
1447 This option is used to change the operation mode of the pinentry. The
1448 following values are defined:
1452 This is the default mode which pops up a pinentry as needed.
1455 Instead of popping up a pinentry, return the error code
1456 @code{GPG_ERR_CANCELED}.
1459 Instead of popping up a pinentry, return the error code
1460 @code{GPG_ERR_NO_PIN_ENTRY}.
1463 Use a loopback pinentry. This fakes a pinentry by using inquiries
1464 back to the caller to ask for a passphrase. This option may only be
1465 set if the agent has been configured for that.
1466 Use the @xref{option --allow-loopback-pinentry}.
1472 @item cache-ttl-opt-preset
1473 This option sets the cache TTL for new entries created by GENKEY and
1474 PASSWD commands when using the @option{--preset} option. It it is not
1475 used a default value is used.
1480 Instead of using the standard S2K count (which is computed on the
1481 fly), the given S2K count is used for new keys or when changing the
1482 passphrase of a key. Values below 65536 are considered to be 0. This
1483 option is valid for the entire session or until reset to 0. This
1484 option is useful if the key is later used on boxes which are either
1485 much slower or faster than the actual box.
1495 @command{gpg-connect-agent}(1),
1496 @command{scdaemon}(1)
1498 @include see-also-note.texi