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.
7 @node Invoking GPG-AGENT
8 @chapter Invoking GPG-AGENT
9 @cindex GPG-AGENT command options
10 @cindex command options
11 @cindex options, GPG-AGENT command
16 \- Secret key management for GnuPG
47 @command{gpg-agent} is a daemon to manage secret (private) keys
48 independently from any protocol. It is used as a backend for
49 @command{gpg} and @command{gpgsm} as well as for a couple of other
52 The agent is automatically started on demand by @command{gpg},
53 @command{gpgsm}, @command{gpgconf}, or @command{gpg-connect-agent}.
54 Thus there is no reason to start it manually. In case you want to use
55 the included Secure Shell Agent you may start the agent using:
58 gpg-connect-agent /bye
62 You should always add the following lines to your @code{.bashrc} or
63 whatever initialization file is used for all shell invocations:
71 It is important that this environment variable always reflects the
72 output of the @code{tty} command. For W32 systems this option is not
75 Please make sure that a proper pinentry program has been installed
76 under the default filename (which is system dependent) or use the
77 option @option{pinentry-program} to specify the full name of that program.
78 It is often useful to install a symbolic link from the actual used
79 pinentry (e.g. @file{@value{BINDIR}/pinentry-gtk}) to the expected
80 one (e.g. @file{@value{BINDIR}/pinentry}).
84 @xref{Option Index},for an index to @command{GPG-AGENT}'s commands and options.
88 * Agent Commands:: List of all commands.
89 * Agent Options:: List of all options.
90 * Agent Configuration:: Configuration files.
91 * Agent Signals:: Use of some signals.
92 * Agent Examples:: Some usage examples.
93 * Agent Protocol:: The protocol the agent uses.
100 Commands are not distinguished from options except for the fact that
101 only one command is allowed.
106 Print the program version and licensing information. Note that you cannot
107 abbreviate this command.
112 Print a usage message summarizing the most useful command-line options.
113 Note that you cannot abbreviate this command.
116 @opindex dump-options
117 Print a list of all available options and commands. Note that you cannot
118 abbreviate this command.
122 Run in server mode and wait for commands on the @code{stdin}. The
123 default mode is to create a socket and listen for commands there.
125 @item --daemon [@var{command line}]
127 Start the gpg-agent as a daemon; that is, detach it from the console
128 and run it in the background.
130 As an alternative you may create a new process as a child of
131 gpg-agent: @code{gpg-agent --daemon /bin/sh}. This way you get a new
132 shell with the environment setup properly; after you exit from this
133 shell, gpg-agent terminates within a few seconds.
138 @section Option Summary
142 @anchor{option --options}
143 @item --options @var{file}
145 Reads configuration from @var{file} instead of from the default
146 per-user configuration file. The default configuration file is named
147 @file{gpg-agent.conf} and expected in the @file{.gnupg} directory directly
148 below the home directory of the user.
150 @anchor{option --homedir}
151 @include opt-homedir.texi
157 Outputs additional information while running.
158 You can increase the verbosity by giving several
159 verbose commands to @command{gpgsm}, such as @samp{-vv}.
164 Try to be as quiet as possible.
168 Don't invoke a pinentry or do any other thing requiring human interaction.
170 @item --faked-system-time @var{epoch}
171 @opindex faked-system-time
172 This option is only useful for testing; it sets the system time back or
173 forth to @var{epoch} which is the number of seconds elapsed since the year
176 @item --debug-level @var{level}
178 Select the debug level for investigating problems. @var{level} may be
179 a numeric value or a keyword:
183 No debugging at all. A value of less than 1 may be used instead of
186 Some basic debug messages. A value between 1 and 2 may be used
187 instead of the keyword.
189 More verbose debug messages. A value between 3 and 5 may be used
190 instead of the keyword.
192 Even more detailed messages. A value between 6 and 8 may be used
193 instead of the keyword.
195 All of the debug messages you can get. A value greater than 8 may be
196 used instead of the keyword. The creation of hash tracing files is
197 only enabled if the keyword is used.
200 How these messages are mapped to the actual debugging flags is not
201 specified and may change with newer releases of this program. They are
202 however carefully selected to best aid in debugging.
204 @item --debug @var{flags}
206 This option is only useful for debugging and the behaviour may change at
207 any time without notice. FLAGS are bit encoded and may be given in
208 usual C-Syntax. The currently defined bits are:
212 X.509 or OpenPGP protocol related data
214 values of big number integers
216 low level crypto operations
222 show memory statistics.
224 write hashed data to files named @code{dbgmd-000*}
226 trace Assuan protocol
228 bypass all certificate validation
233 Same as @code{--debug=0xffffffff}
235 @item --debug-wait @var{n}
237 When running in server mode, wait @var{n} seconds before entering the
238 actual processing loop and print the pid. This gives time to attach a
241 @item --debug-quick-random
242 @opindex debug-quick-random
243 This option inhibits the use of the very secure random quality level
244 (Libgcrypt’s @code{GCRY_VERY_STRONG_RANDOM}) and degrades all request
245 down to standard random quality. It is only used for testing and
246 shall not be used for any production quality keys. This option is
247 only effective when given on the command line.
249 @item --debug-pinentry
250 @opindex debug-pinentry
251 This option enables extra debug information pertaining to the
252 Pinentry. As of now it is only useful when used along with
257 Don't detach the process from the console. This is mainly useful for
266 Format the info output in daemon mode for use with the standard Bourne
267 shell or the C-shell respectively. The default is to guess it based on
268 the environment variable @code{SHELL} which is correct in almost all
274 Tell the pinentry not to grab the keyboard and mouse. This option
275 should in general not be used to avoid X-sniffing attacks.
277 @anchor{option --log-file}
278 @item --log-file @var{file}
280 Append all logging output to @var{file}. This is very helpful in seeing
281 what the agent actually does. If neither a log file nor a log file
282 descriptor has been set on a Windows platform, the Registry entry
283 @code{HKCU\Software\GNU\GnuPG:DefaultLogFile}, if set, is used to specify
287 @anchor{option --no-allow-mark-trusted}
288 @item --no-allow-mark-trusted
289 @opindex no-allow-mark-trusted
290 Do not allow clients to mark keys as trusted, i.e. put them into the
291 @file{trustlist.txt} file. This makes it harder for users to inadvertently
294 @anchor{option --allow-preset-passphrase}
295 @item --allow-preset-passphrase
296 @opindex allow-preset-passphrase
297 This option allows the use of @command{gpg-preset-passphrase} to seed the
298 internal cache of @command{gpg-agent} with passphrases.
300 @anchor{option --allow-loopback-pinentry}
301 @item --allow-loopback-pinentry
302 @opindex allow-loopback-pinentry
303 Allow clients to use the loopback pinentry features; see the option
304 @option{pinentry-mode} for details.
306 @item --no-allow-external-cache
307 @opindex no-allow-external-cache
308 Tell Pinentry not to enable features which use an external cache for
311 Some desktop environments prefer to unlock all
312 credentials with one master password and may have installed a Pinentry
313 which employs an additional external cache to implement such a policy.
314 By using this option the Pinentry is advised not to make use of such a
315 cache and instead always ask the user for the requested passphrase.
317 @item --allow-emacs-pinentry
318 @opindex allow-emacs-pinentry
319 Tell Pinentry to allow features to divert the passphrase entry to a
320 running Emacs instance. How this is exactly handled depends on the
321 version of the used Pinentry.
323 @item --ignore-cache-for-signing
324 @opindex ignore-cache-for-signing
325 This option will let @command{gpg-agent} bypass the passphrase cache for all
326 signing operation. Note that there is also a per-session option to
327 control this behaviour but this command line option takes precedence.
329 @item --default-cache-ttl @var{n}
330 @opindex default-cache-ttl
331 Set the time a cache entry is valid to @var{n} seconds. The default
332 is 600 seconds. Each time a cache entry is accessed, the entry's
333 timer is reset. To set an entry's maximum lifetime, use
334 @command{max-cache-ttl}.
336 @item --default-cache-ttl-ssh @var{n}
337 @opindex default-cache-ttl
338 Set the time a cache entry used for SSH keys is valid to @var{n}
339 seconds. The default is 1800 seconds. Each time a cache entry is
340 accessed, the entry's timer is reset. To set an entry's maximum
341 lifetime, use @command{max-cache-ttl-ssh}.
343 @item --max-cache-ttl @var{n}
344 @opindex max-cache-ttl
345 Set the maximum time a cache entry is valid to @var{n} seconds. After
346 this time a cache entry will be expired even if it has been accessed
347 recently or has been set using @command{gpg-preset-passphrase}. The
348 default is 2 hours (7200 seconds).
350 @item --max-cache-ttl-ssh @var{n}
351 @opindex max-cache-ttl-ssh
352 Set the maximum time a cache entry used for SSH keys is valid to
353 @var{n} seconds. After this time a cache entry will be expired even
354 if it has been accessed recently or has been set using
355 @command{gpg-preset-passphrase}. The default is 2 hours (7200
358 @item --enforce-passphrase-constraints
359 @opindex enforce-passphrase-constraints
360 Enforce the passphrase constraints by not allowing the user to bypass
361 them using the ``Take it anyway'' button.
363 @item --min-passphrase-len @var{n}
364 @opindex min-passphrase-len
365 Set the minimal length of a passphrase. When entering a new passphrase
366 shorter than this value a warning will be displayed. Defaults to 8.
368 @item --min-passphrase-nonalpha @var{n}
369 @opindex min-passphrase-nonalpha
370 Set the minimal number of digits or special characters required in a
371 passphrase. When entering a new passphrase with less than this number
372 of digits or special characters a warning will be displayed. Defaults
375 @item --check-passphrase-pattern @var{file}
376 @opindex check-passphrase-pattern
377 Check the passphrase against the pattern given in @var{file}. When
378 entering a new passphrase matching one of these pattern a warning will
379 be displayed. @var{file} should be an absolute filename. The default is
380 not to use any pattern file.
382 Security note: It is known that checking a passphrase against a list of
383 pattern or even against a complete dictionary is not very effective to
384 enforce good passphrases. Users will soon figure up ways to bypass such
385 a policy. A better policy is to educate users on good security
386 behavior and optionally to run a passphrase cracker regularly on all
387 users passphrases to catch the very simple ones.
389 @item --max-passphrase-days @var{n}
390 @opindex max-passphrase-days
391 Ask the user to change the passphrase if @var{n} days have passed since
392 the last change. With @option{--enforce-passphrase-constraints} set the
393 user may not bypass this check.
395 @item --enable-passphrase-history
396 @opindex enable-passphrase-history
397 This option does nothing yet.
399 @item --pinentry-program @var{filename}
400 @opindex pinentry-program
401 Use program @var{filename} as the PIN entry. The default is
402 installation dependent. With the default configuration the name of
403 the default pinentry is @file{pinentry}; if that file does not exist
404 but a @file{pinentry-basic} exist the latter is used.
406 On a Windows platform the default is to use the first existing program
408 @file{bin\pinentry.exe},
409 @file{..\Gpg4win\bin\pinentry.exe},
410 @file{..\Gpg4win\pinentry.exe},
411 @file{..\GNU\GnuPG\pinentry.exe},
412 @file{..\GNU\bin\pinentry.exe},
413 @file{bin\pinentry-basic.exe}
414 where the file names are relative to the GnuPG installation directory.
417 @item --pinentry-touch-file @var{filename}
418 @opindex pinentry-touch-file
419 By default the filename of the socket gpg-agent is listening for
420 requests is passed to Pinentry, so that it can touch that file before
421 exiting (it does this only in curses mode). This option changes the
422 file passed to Pinentry to @var{filename}. The special name
423 @code{/dev/null} may be used to completely disable this feature. Note
424 that Pinentry will not create that file, it will only change the
425 modification and access time.
428 @item --scdaemon-program @var{filename}
429 @opindex scdaemon-program
430 Use program @var{filename} as the Smartcard daemon. The default is
431 installation dependent and can be shown with the @command{gpgconf}
434 @item --disable-scdaemon
435 @opindex disable-scdaemon
436 Do not make use of the scdaemon tool. This option has the effect of
437 disabling the ability to do smartcard operations. Note, that enabling
438 this option at runtime does not kill an already forked scdaemon.
440 @item --disable-check-own-socket
441 @opindex disable-check-own-socket
442 @command{gpg-agent} employs a periodic self-test to detect a stolen
443 socket. This usually means a second instance of @command{gpg-agent}
444 has taken over the socket and @command{gpg-agent} will then terminate
445 itself. This option may be used to disable this self-test for
448 @item --use-standard-socket
449 @itemx --no-use-standard-socket
450 @itemx --use-standard-socket-p
451 @opindex use-standard-socket
452 @opindex no-use-standard-socket
453 @opindex use-standard-socket-p
454 Since GnuPG 2.1 the standard socket is always used. These options
455 have no more effect. The command @code{gpg-agent
456 --use-standard-socket-p} will thus always return success.
458 @item --display @var{string}
459 @itemx --ttyname @var{string}
460 @itemx --ttytype @var{string}
461 @itemx --lc-ctype @var{string}
462 @itemx --lc-messages @var{string}
463 @itemx --xauthority @var{string}
470 These options are used with the server mode to pass localization
474 @itemx --keep-display
476 @opindex keep-display
477 Ignore requests to change the current @code{tty} or X window system's
478 @code{DISPLAY} variable respectively. This is useful to lock the
479 pinentry to pop up at the @code{tty} or display you started the agent.
482 @anchor{option --extra-socket}
483 @item --extra-socket @var{name}
484 @opindex extra-socket
485 Also listen on native gpg-agent connections on the given socket. The
486 intended use for this extra socket is to setup a Unix domain socket
487 forwarding from a remote machine to this socket on the local machine.
488 A @command{gpg} running on the remote machine may then connect to the
489 local gpg-agent and use its private keys. This allows to decrypt or
490 sign data on a remote machine without exposing the private keys to the
494 @anchor{option --enable-ssh-support}
495 @item --enable-ssh-support
496 @itemx --enable-putty-support
497 @opindex enable-ssh-support
498 @opindex enable-putty-support
500 Enable the OpenSSH Agent protocol.
502 In this mode of operation, the agent does not only implement the
503 gpg-agent protocol, but also the agent protocol used by OpenSSH
504 (through a separate socket). Consequently, it should be possible to use
505 the gpg-agent as a drop-in replacement for the well known ssh-agent.
507 SSH Keys, which are to be used through the agent, need to be added to
508 the gpg-agent initially through the ssh-add utility. When a key is
509 added, ssh-add will ask for the password of the provided key file and
510 send the unprotected key material to the agent; this causes the
511 gpg-agent to ask for a passphrase, which is to be used for encrypting
512 the newly received key and storing it in a gpg-agent specific
515 Once a key has been added to the gpg-agent this way, the gpg-agent
516 will be ready to use the key.
518 Note: in case the gpg-agent receives a signature request, the user might
519 need to be prompted for a passphrase, which is necessary for decrypting
520 the stored key. Since the ssh-agent protocol does not contain a
521 mechanism for telling the agent on which display/terminal it is running,
522 gpg-agent's ssh-support will use the TTY or X display where gpg-agent
523 has been started. To switch this display to the current one, the
524 following command may be used:
527 gpg-connect-agent updatestartuptty /bye
530 Although all GnuPG components try to start the gpg-agent as needed, this
531 is not possible for the ssh support because ssh does not know about it.
532 Thus if no GnuPG tool which accesses the agent has been run, there is no
533 guarantee that ssh is able to use gpg-agent for authentication. To fix
534 this you may start gpg-agent if needed using this simple command:
537 gpg-connect-agent /bye
540 Adding the @option{--verbose} shows the progress of starting the agent.
542 The @option{--enable-putty-support} is only available under Windows
543 and allows the use of gpg-agent with the ssh implementation
544 @command{putty}. This is similar to the regular ssh-agent support but
545 makes use of Windows message queue as required by @command{putty}.
550 All the long options may also be given in the configuration file after
551 stripping off the two leading dashes.
555 @node Agent Configuration
556 @section Configuration
558 There are a few configuration files needed for the operation of the
559 agent. By default they may all be found in the current home directory
560 (@pxref{option --homedir}).
565 @cindex gpg-agent.conf
566 This is the standard configuration file read by @command{gpg-agent} on
567 startup. It may contain any valid long option; the leading
568 two dashes may not be entered and the option may not be abbreviated.
569 This file is also read after a @code{SIGHUP} however only a few
570 options will actually have an effect. This default name may be
571 changed on the command line (@pxref{option --options}).
572 You should backup this file.
575 This is the list of trusted keys. You should backup this file.
577 Comment lines, indicated by a leading hash mark, as well as empty
578 lines are ignored. To mark a key as trusted you need to enter its
579 fingerprint followed by a space and a capital letter @code{S}. Colons
580 may optionally be used to separate the bytes of a fingerprint; this
581 allows to cut and paste the fingerprint from a key listing output. If
582 the line is prefixed with a @code{!} the key is explicitly marked as
585 Here is an example where two keys are marked as ultimately trusted
586 and one as not trusted:
590 # CN=Wurzel ZS 3,O=Intevation GmbH,C=DE
591 A6935DD34EF3087973C706FC311AA2CCF733765B S
593 # CN=PCA-1-Verwaltung-02/O=PKI-1-Verwaltung/C=DE
594 DC:BD:69:25:48:BD:BB:7E:31:6E:BB:80:D3:00:80:35:D4:F8:A6:CD S
596 # CN=Root-CA/O=Schlapphuete/L=Pullach/C=DE
597 !14:56:98:D3:FE:9C:CA:5A:31:6E:BC:81:D3:11:4E:00:90:A3:44:C2 S
601 Before entering a key into this file, you need to ensure its
602 authenticity. How to do this depends on your organisation; your
603 administrator might have already entered those keys which are deemed
604 trustworthy enough into this file. Places where to look for the
605 fingerprint of a root certificate are letters received from the CA or
606 the website of the CA (after making 100% sure that this is indeed the
607 website of that CA). You may want to consider disallowing interactive
608 updates of this file by using the @xref{option --no-allow-mark-trusted}.
609 It might even be advisable to change the permissions to read-only so
610 that this file can't be changed inadvertently.
612 As a special feature a line @code{include-default} will include a global
613 list of trusted certificates (e.g. @file{@value{SYSCONFDIR}/trustlist.txt}).
614 This global list is also used if the local list is not available.
616 It is possible to add further flags after the @code{S} for use by the
623 Relax checking of some root certificate requirements. As of now this
624 flag allows the use of root certificates with a missing basicConstraints
625 attribute (despite that it is a MUST for CA certificates) and disables
626 CRL checking for the root certificate.
629 If validation of a certificate finally issued by a CA with this flag set
630 fails, try again using the chain validation model.
637 This file is used when support for the secure shell agent protocol has
638 been enabled (@pxref{option --enable-ssh-support}). Only keys present in
639 this file are used in the SSH protocol. You should backup this file.
641 The @command{ssh-add} tool may be used to add new entries to this file;
642 you may also add them manually. Comment lines, indicated by a leading
643 hash mark, as well as empty lines are ignored. An entry starts with
644 optional whitespace, followed by the keygrip of the key given as 40 hex
645 digits, optionally followed by the caching TTL in seconds and another
646 optional field for arbitrary flags. A non-zero TTL overrides the global
647 default as set by @option{--default-cache-ttl-ssh}.
649 The only flag support is @code{confirm}. If this flag is found for a
650 key, each use of the key will pop up a pinentry to confirm the use of
651 that key. The flag is automatically set if a new key was loaded into
652 @code{gpg-agent} using the option @option{-c} of the @code{ssh-add}
655 The keygrip may be prefixed with a @code{!} to disable an entry entry.
657 The following example lists exactly one key. Note that keys available
658 through a OpenPGP smartcard in the active smartcard reader are
659 implicitly added to this list; i.e. there is no need to list them.
663 # Key added on: 2011-07-20 20:38:46
664 # Fingerprint: 5e:8d:c4:ad:e7:af:6e:27:8a:d6:13:e4:79:ad:0b:81
665 34B62F25E277CF13D3C6BCEBFD3F85D08F0A864B 0 confirm
669 @item private-keys-v1.d/
671 This is the directory where gpg-agent stores the private keys. Each
672 key is stored in a file with the name made up of the keygrip and the
673 suffix @file{key}. You should backup all files in this directory
674 and take great care to keep this backup closed away.
679 Note that on larger installations, it is useful to put predefined
680 files into the directory @file{@value{SYSCONFSKELDIR}} so that newly created
681 users start up with a working configuration. For existing users the
682 a small helper script is provided to create these files (@pxref{addgnupghome}).
691 @section Use of some signals.
692 A running @command{gpg-agent} may be controlled by signals, i.e. using
693 the @command{kill} command to send a signal to the process.
695 Here is a list of supported signals:
701 This signal flushes all cached passphrases and if the program has been
702 started with a configuration file, the configuration file is read
703 again. Only certain options are honored: @code{quiet},
704 @code{verbose}, @code{debug}, @code{debug-all}, @code{debug-level},
705 @code{debug-pinentry},
706 @code{no-grab}, @code{pinentry-program}, @code{default-cache-ttl},
707 @code{max-cache-ttl}, @code{ignore-cache-for-signing},
708 @code{no-allow-external-cache}, @code{allow-emacs-pinentry},
709 @code{no-allow-mark-trusted}, @code{disable-scdaemon}, and
710 @code{disable-check-own-socket}. @code{scdaemon-program} is also
711 supported but due to the current implementation, which calls the
712 scdaemon only once, it is not of much use unless you manually kill the
718 Shuts down the process but waits until all current requests are
719 fulfilled. If the process has received 3 of these signals and requests
720 are still pending, a shutdown is forced.
724 Shuts down the process immediately.
728 Dump internal information to the log file.
732 This signal is used for internal purposes.
743 It is important to set the GPG_TTY environment variable in
744 your login shell, for example in the @file{~/.bashrc} init script:
748 export GPG_TTY=$(tty)
752 If you enabled the Ssh Agent Support, you also need to tell ssh about
753 it by adding this to your init script:
758 if [ "$@{gnupg_SSH_AUTH_SOCK_by:-0@}" -ne $$ ]; then
759 export SSH_AUTH_SOCK="$@{HOME@}/.gnupg/S.gpg-agent.ssh"
770 @section Agent's Assuan Protocol
772 Note: this section does only document the protocol, which is used by
773 GnuPG components; it does not deal with the ssh-agent protocol.
775 The @command{gpg-agent} daemon is started on demand by the GnuPG
778 To identify a key we use a thing called keygrip which is the SHA-1 hash
779 of an canonical encoded S-Expression of the public key as used in
780 Libgcrypt. For the purpose of this interface the keygrip is given as a
781 hex string. The advantage of using this and not the hash of a
782 certificate is that it will be possible to use the same keypair for
783 different protocols, thereby saving space on the token used to keep the
786 The @command{gpg-agent} may send status messages during a command or when
787 returning from a command to inform a client about the progress or result of an
788 operation. For example, the @var{INQUIRE_MAXLEN} status message may be sent
789 during a server inquire to inform the client of the maximum usable length of
790 the inquired data (which should not be exceeded).
793 * Agent PKDECRYPT:: Decrypting a session key
794 * Agent PKSIGN:: Signing a Hash
795 * Agent GENKEY:: Generating a Key
796 * Agent IMPORT:: Importing a Secret Key
797 * Agent EXPORT:: Exporting a Secret Key
798 * Agent ISTRUSTED:: Importing a Root Certificate
799 * Agent GET_PASSPHRASE:: Ask for a passphrase
800 * Agent CLEAR_PASSPHRASE:: Expire a cached passphrase
801 * Agent PRESET_PASSPHRASE:: Set a passphrase for a keygrip
802 * Agent GET_CONFIRMATION:: Ask for confirmation
803 * Agent HAVEKEY:: Check whether a key is available
804 * Agent LEARN:: Register a smartcard
805 * Agent PASSWD:: Change a Passphrase
806 * Agent UPDATESTARTUPTTY:: Change the Standard Display
807 * Agent GETEVENTCOUNTER:: Get the Event Counters
808 * Agent GETINFO:: Return information about the process
809 * Agent OPTION:: Set options for the session
812 @node Agent PKDECRYPT
813 @subsection Decrypting a session key
815 The client asks the server to decrypt a session key. The encrypted
816 session key should have all information needed to select the
817 appropriate secret key or to delegate it to a smartcard.
823 Tell the server about the key to be used for decryption. If this is
824 not used, @command{gpg-agent} may try to figure out the key by trying to
825 decrypt the message with each key available.
831 The agent checks whether this command is allowed and then does an
832 INQUIRY to get the ciphertext the client should then send the cipher
836 S: INQUIRE CIPHERTEXT
842 Please note that the server may send status info lines while reading the
843 data lines from the client. The data send is a SPKI like S-Exp with
849 (<param_name1> <mpi>)
851 (<param_namen> <mpi>)))
854 Where algo is a string with the name of the algorithm; see the libgcrypt
855 documentation for a list of valid algorithms. The number and names of
856 the parameters depend on the algorithm. The agent does return an error
857 if there is an inconsistency.
859 If the decryption was successful the decrypted data is returned by
862 Here is an example session:
866 S: INQUIRE CIPHERTEXT
867 C: D (enc-val elg (a 349324324)
868 C: D (b 3F444677CA)))
870 S: # session key follows
872 S: D (value 1234567890ABCDEF0)
873 S: OK descryption successful
877 The “PADDING” status line is only send if gpg-agent can tell what kind
878 of padding is used. As of now only the value 0 is used to indicate
879 that the padding has been removed.
883 @subsection Signing a Hash
885 The client ask the agent to sign a given hash value. A default key
886 will be chosen if no key has been set. To set a key a client first
893 This can be used multiple times to create multiple signature, the list
894 of keys is reset with the next PKSIGN command or a RESET. The server
895 test whether the key is a valid key to sign something and responds with
899 SETHASH --hash=<name>|<algo> <hexstring>
902 The client can use this command to tell the server about the data <hexstring>
903 (which usually is a hash) to be signed. <algo> is the decimal encoded hash
904 algorithm number as used by Libgcrypt. Either <algo> or --hash=<name>
905 must be given. Valid names for <name> are:
909 The SHA-1 hash algorithm
911 The SHA-256 hash algorithm
913 The RIPE-MD160 hash algorithm
915 The old and broken MD5 hash algorithm
917 A combined hash algorithm as used by the TLS protocol.
921 The actual signing is done using
927 Options are not yet defined, but my later be used to choose among
928 different algorithms. The agent does then some checks, asks for the
929 passphrase and as a result the server returns the signature as an SPKI
930 like S-expression in "D" lines:
935 (<param_name1> <mpi>)
937 (<param_namen> <mpi>)))
941 The operation is affected by the option
944 OPTION use-cache-for-signing=0|1
947 The default of @code{1} uses the cache. Setting this option to @code{0}
948 will lead @command{gpg-agent} to ignore the passphrase cache. Note, that there is
949 also a global command line option for @command{gpg-agent} to globally disable the
953 Here is an example session:
961 S: # I did ask the user whether he really wants to sign
962 S: # I did ask the user for the passphrase
964 C: D ABCDEF012345678901234
966 S: # signature follows
967 S: D (sig-val rsa (s 45435453654612121212))
973 @subsection Generating a Key
975 This is used to create a new keypair and store the secret key inside the
976 active PSE --- which is in most cases a Soft-PSE. An not yet defined
977 option allows to choose the storage location. To get the secret key out
978 of the PSE, a special export tool has to be used.
981 GENKEY [--no-protection] [--preset] [<cache_nonce>]
984 Invokes the key generation process and the server will then inquire
985 on the generation parameters, like:
989 C: D (genkey (rsa (nbits 1024)))
993 The format of the key parameters which depends on the algorithm is of
999 (parameter_name_1 ....)
1001 (parameter_name_n ....)))
1004 If everything succeeds, the server returns the *public key* in a SPKI
1005 like S-Expression like this:
1014 Here is an example session:
1019 C: D (genkey (rsa (nbits 1024)))
1022 S: D (rsa (n 326487324683264) (e 10001)))
1027 The @option{--no-protection} option may be used to prevent prompting for a
1028 passphrase to protect the secret key while leaving the secret key unprotected.
1029 The @option{--preset} option may be used to add the passphrase to the cache
1030 using the default cache parameters.
1032 The @option{--inq-passwd} option may be used to create the key with a
1033 supplied passphrase. When used the agent does an inquiry with the
1034 keyword @code{NEWPASSWD} to retrieve that passphrase. This option
1035 takes precedence over @option{--no-protection}; however if the client
1036 sends a empty (zero-length) passphrase, this is identical to
1037 @option{--no-protection}.
1040 @subsection Importing a Secret Key
1042 This operation is not yet supported by GpgAgent. Specialized tools
1043 are to be used for this.
1045 There is no actual need because we can expect that secret keys
1046 created by a 3rd party are stored on a smartcard. If we have
1047 generated the key ourself, we do not need to import it.
1050 @subsection Export a Secret Key
1054 Should be done by an extra tool.
1056 @node Agent ISTRUSTED
1057 @subsection Importing a Root Certificate
1059 Actually we do not import a Root Cert but provide a way to validate
1060 any piece of data by storing its Hash along with a description and
1061 an identifier in the PSE. Here is the interface description:
1064 ISTRUSTED <fingerprint>
1067 Check whether the OpenPGP primary key or the X.509 certificate with the
1068 given fingerprint is an ultimately trusted key or a trusted Root CA
1069 certificate. The fingerprint should be given as a hexstring (without
1070 any blanks or colons or whatever in between) and may be left padded with
1071 00 in case of an MD5 fingerprint. GPGAgent will answer with:
1077 The key is in the table of trusted keys.
1080 ERR 304 (Not Trusted)
1083 The key is not in this table.
1085 Gpg needs the entire list of trusted keys to maintain the web of
1086 trust; the following command is therefore quite helpful:
1092 GpgAgent returns a list of trusted keys line by line:
1095 S: D 000000001234454556565656677878AF2F1ECCFF P
1096 S: D 340387563485634856435645634856438576457A P
1097 S: D FEDC6532453745367FD83474357495743757435D S
1101 The first item on a line is the hexified fingerprint where MD5
1102 fingerprints are @code{00} padded to the left and the second item is a
1103 flag to indicate the type of key (so that gpg is able to only take care
1104 of PGP keys). P = OpenPGP, S = S/MIME. A client should ignore the rest
1105 of the line, so that we can extend the format in the future.
1107 Finally a client should be able to mark a key as trusted:
1110 MARKTRUSTED @var{fingerprint} "P"|"S"
1113 The server will then pop up a window to ask the user whether she
1114 really trusts this key. For this it will probably ask for a text to
1115 be displayed like this:
1118 S: INQUIRE TRUSTDESC
1119 C: D Do you trust the key with the fingerprint @@FPR@@
1120 C: D bla fasel blurb.
1125 Known sequences with the pattern @@foo@@ are replaced according to this
1130 Format the fingerprint according to gpg rules for a v3 keys.
1132 Format the fingerprint according to gpg rules for a v4 keys.
1134 Choose an appropriate format to format the fingerprint.
1136 Replaced by a single @code{@@}
1139 @node Agent GET_PASSPHRASE
1140 @subsection Ask for a passphrase
1142 This function is usually used to ask for a passphrase to be used for
1143 symmetric encryption, but may also be used by programs which need
1144 special handling of passphrases. This command uses a syntax which helps
1145 clients to use the agent with minimum effort.
1148 GET_PASSPHRASE [--data] [--check] [--no-ask] [--repeat[=N]] \
1149 [--qualitybar] @var{cache_id} \
1150 [@var{error_message} @var{prompt} @var{description}]
1153 @var{cache_id} is expected to be a string used to identify a cached
1154 passphrase. Use a @code{X} to bypass the cache. With no other
1155 arguments the agent returns a cached passphrase or an error. By
1156 convention either the hexified fingerprint of the key shall be used for
1157 @var{cache_id} or an arbitrary string prefixed with the name of the
1158 calling application and a colon: Like @code{gpg:somestring}.
1160 @var{error_message} is either a single @code{X} for no error message or
1161 a string to be shown as an error message like (e.g. "invalid
1162 passphrase"). Blanks must be percent escaped or replaced by @code{+}'.
1164 @var{prompt} is either a single @code{X} for a default prompt or the
1165 text to be shown as the prompt. Blanks must be percent escaped or
1166 replaced by @code{+}.
1168 @var{description} is a text shown above the entry field. Blanks must be
1169 percent escaped or replaced by @code{+}.
1171 The agent either returns with an error or with a OK followed by the hex
1172 encoded passphrase. Note that the length of the strings is implicitly
1173 limited by the maximum length of a command. If the option
1174 @option{--data} is used, the passphrase is not returned on the OK line
1175 but by regular data lines; this is the preferred method.
1177 If the option @option{--check} is used, the standard passphrase
1178 constraints checks are applied. A check is not done if the passphrase
1179 has been found in the cache.
1181 If the option @option{--no-ask} is used and the passphrase is not in the
1182 cache the user will not be asked to enter a passphrase but the error
1183 code @code{GPG_ERR_NO_DATA} is returned.
1185 If the option @option{--qualitybar} is used and a minimum passphrase
1186 length has been configured, a visual indication of the entered
1187 passphrase quality is shown.
1190 CLEAR_PASSPHRASE @var{cache_id}
1193 may be used to invalidate the cache entry for a passphrase. The
1194 function returns with OK even when there is no cached passphrase.
1198 @node Agent CLEAR_PASSPHRASE
1199 @subsection Remove a cached passphrase
1201 Use this command to remove a cached passphrase.
1204 CLEAR_PASSPHRASE [--mode=normal] <cache_id>
1207 The @option{--mode=normal} option can be used to clear a @var{cache_id} that
1208 was set by gpg-agent.
1211 @node Agent PRESET_PASSPHRASE
1212 @subsection Set a passphrase for a keygrip
1214 This command adds a passphrase to the cache for the specified @var{keygrip}.
1217 PRESET_PASSPHRASE [--inquire] <string_or_keygrip> <timeout> [<hexstring>]
1220 The passphrase is a hexidecimal string when specified. When not specified, the
1221 passphrase will be retrieved from the pinentry module unless the
1222 @option{--inquire} option was specified in which case the passphrase will be
1223 retrieved from the client.
1225 The @var{timeout} parameter keeps the passphrase cached for the specified
1226 number of seconds. A value of @code{-1} means infinate while @code{0} means
1227 the default (currently only a timeout of -1 is allowed, which means to never
1231 @node Agent GET_CONFIRMATION
1232 @subsection Ask for confirmation
1234 This command may be used to ask for a simple confirmation by
1235 presenting a text and 2 buttons: Okay and Cancel.
1238 GET_CONFIRMATION @var{description}
1241 @var{description}is displayed along with a Okay and Cancel
1242 button. Blanks must be percent escaped or replaced by @code{+}. A
1243 @code{X} may be used to display confirmation dialog with a default
1246 The agent either returns with an error or with a OK. Note, that the
1247 length of @var{description} is implicitly limited by the maximum
1248 length of a command.
1253 @subsection Check whether a key is available
1255 This can be used to see whether a secret key is available. It does
1256 not return any information on whether the key is somehow protected.
1259 HAVEKEY @var{keygrips}
1262 The agent answers either with OK or @code{No_Secret_Key} (208). The
1263 caller may want to check for other error codes as well. More than one
1264 keygrip may be given. In this case the command returns success if at
1265 least one of the keygrips corresponds to an available secret key.
1269 @subsection Register a smartcard
1275 This command is used to register a smartcard. With the --send
1276 option given the certificates are send back.
1280 @subsection Change a Passphrase
1283 PASSWD [--cache-nonce=<c>] [--passwd-nonce=<s>] [--preset] @var{keygrip}
1286 This command is used to interactively change the passphrase of the key
1287 identified by the hex string @var{keygrip}. The @option{--preset}
1288 option may be used to add the new passphrase to the cache using the
1289 default cache parameters.
1292 @node Agent UPDATESTARTUPTTY
1293 @subsection Change the standard display
1299 Set the startup TTY and X-DISPLAY variables to the values of this
1300 session. This command is useful to direct future pinentry invocations
1301 to another screen. It is only required because there is no way in the
1302 ssh-agent protocol to convey this information.
1305 @node Agent GETEVENTCOUNTER
1306 @subsection Get the Event Counters
1312 This function return one status line with the current values of the
1313 event counters. The event counters are useful to avoid polling by
1314 delaying a poll until something has changed. The values are decimal
1315 numbers in the range @code{0} to @code{UINT_MAX} and wrapping around to
1316 0. The actual values should not be relied upon; they shall only be used
1319 The currently defined counters are are:
1322 Incremented with any change of any of the other counters.
1324 Incremented for added or removed private keys.
1326 Incremented for changes of the card readers stati.
1330 @subsection Return information about the process
1332 This is a multipurpose function to return a variety of information.
1338 The value of @var{what} specifies the kind of information returned:
1341 Return the version of the program.
1343 Return the process id of the process.
1345 Return the name of the socket used to connect the agent.
1346 @item ssh_socket_name
1347 Return the name of the socket used for SSH connections. If SSH support
1348 has not been enabled the error @code{GPG_ERR_NO_DATA} will be returned.
1352 @subsection Set options for the session
1354 Here is a list of session options which are not yet described with
1355 other commands. The general syntax for an Assuan option is:
1358 OPTION @var{key}=@var{value}
1362 Supported @var{key}s are:
1365 @item agent-awareness
1366 This may be used to tell gpg-agent of which gpg-agent version the
1367 client is aware of. gpg-agent uses this information to enable
1368 features which might break older clients.
1371 Change the session's environment to be used for the
1372 Pinentry. Valid values are:
1376 Delete envvar @var{name}
1378 Set envvar @var{name} to the empty string
1379 @item @var{name}=@var{value}
1380 Set envvar @var{name} to the string @var{value}.
1383 @item use-cache-for-signing
1384 See Assuan command @code{PKSIGN}.
1386 @item allow-pinentry-notify
1387 This does not need any value. It is used to enable the
1388 PINENTRY_LAUNCHED inquiry.
1391 This option is used to change the operation mode of the pinentry. The
1392 following values are defined:
1396 This is the default mode which pops up a pinentry as needed.
1399 Instead of popping up a pinentry, return the error code
1400 @code{GPG_ERR_CANCELED}.
1403 Instead of popping up a pinentry, return the error code
1404 @code{GPG_ERR_NO_PIN_ENTRY}.
1407 Use a loopback pinentry. This fakes a pinentry by using inquiries
1408 back to the caller to ask for a passphrase. This option may only be
1409 set if the agent has been configured for that.
1410 Use the @xref{option --allow-loopback-pinentry}.
1414 @item cache-ttl-opt-preset
1415 This option sets the cache TTL for new entries created by GENKEY and
1416 PASSWD commands when using the @option{--preset} option. It it is not
1417 used a default value is used.
1420 Instead of using the standard S2K count (which is computed on the
1421 fly), the given S2K count is used for new keys or when changing the
1422 passphrase of a key. Values below 65536 are considered to be 0. This
1423 option is valid for the entire session or until reset to 0. This
1424 option is useful if the key is later used on boxes which are either
1425 much slower or faster than the actual box.
1434 @command{gpg-connect-agent}(1),
1435 @command{scdaemon}(1)
1437 @include see-also-note.texi