1 @c Copyright (C) 2002 Klar"alvdalens Datakonsult AB
2 @c Copyright (C) 2004, 2005, 2006, 2007 g10 Code GmbH
3 @c This is part of the GnuPG manual.
4 @c For copying conditions, see the file gnupg.texi.
9 @chapter Invoking DIRMNGR
10 @cindex DIRMNGR command options
11 @cindex command options
12 @cindex options, DIRMNGR command
17 \- CRL and OCSP daemon
29 Since version 2.1 of GnuPG, @command{dirmngr} takes care of accessing
30 the OpenPGP keyservers. As with previous versions it is also used as
31 a server for managing and downloading certificate revocation lists
32 (CRLs) for X.509 certificates, downloading X.509 certificates, and
33 providing access to OCSP providers. Dirmngr is invoked internally by
34 @command{gpg}, @command{gpgsm}, or via the @command{gpg-connect-agent}
39 @xref{Option Index},for an index to @command{DIRMNGR}'s commands and
44 * Dirmngr Commands:: List of all commands.
45 * Dirmngr Options:: List of all options.
46 * Dirmngr Configuration:: Configuration files.
47 * Dirmngr Signals:: Use of signals.
48 * Dirmngr Examples:: Some usage examples.
49 * Dirmngr Protocol:: The protocol dirmngr uses.
53 @node Dirmngr Commands
57 Commands are not distinguished from options except for the fact that
58 only one command is allowed.
63 Print the program version and licensing information. Note that you cannot
64 abbreviate this command.
68 Print a usage message summarizing the most useful command-line options.
69 Note that you cannot abbreviate this command.
73 Print a list of all available options and commands. Note that you cannot
74 abbreviate this command.
78 Run in server mode and wait for commands on the @code{stdin}. The
79 default mode is to create a socket and listen for commands there.
80 This is only used for testing.
84 Run in background daemon mode and listen for commands on a socket.
85 This is the way @command{dirmngr} is started on demand by the other
86 GnuPG components. To force starting @command{dirmngr} it is in
87 general best to use @code{gpgconf --launch dirmngr}.
91 Run in the foreground, sending logs to stderr, and listening on file
92 descriptor 3, which must already be bound to a listening socket. This
93 is useful when running under systemd or other similar process
94 supervision schemes. This option is not supported on Windows.
98 List the contents of the CRL cache on @code{stdout}. This is probably
99 only useful for debugging purposes.
101 @item --load-crl @var{file}
103 This command requires a filename as additional argument, and it will
104 make Dirmngr try to import the CRL in @var{file} into it's cache.
105 Note, that this is only possible if Dirmngr is able to retrieve the
106 CA's certificate directly by its own means. In general it is better
107 to use @code{gpgsm}'s @code{--call-dirmngr loadcrl filename} command
108 so that @code{gpgsm} can help dirmngr.
110 @item --fetch-crl @var{url}
112 This command requires an URL as additional argument, and it will make
113 dirmngr try to retrieve and import the CRL from that @var{url} into
114 it's cache. This is mainly useful for debugging purposes. The
115 @command{dirmngr-client} provides the same feature for a running dirmngr.
119 This commands shuts down an running instance of Dirmngr. This command
120 has currently no effect.
124 This command removes all CRLs from Dirmngr's cache. Client requests
125 will thus trigger reading of fresh CRLs.
131 @node Dirmngr Options
132 @section Option Summary
136 @item --options @var{file}
138 Reads configuration from @var{file} instead of from the default
139 per-user configuration file. The default configuration file is named
140 @file{dirmngr.conf} and expected in the home directory.
142 @item --homedir @var{dir}
144 Set the name of the home directory to @var{dir}. This option is only
145 effective when used on the command line. The default is
146 the directory named @file{.gnupg} directly below the home directory
147 of the user unless the environment variable @code{GNUPGHOME} has been set
148 in which case its value will be used. Many kinds of data are stored within
156 Outputs additional information while running.
157 You can increase the verbosity by giving several
158 verbose commands to @sc{dirmngr}, such as @option{-vv}.
161 @item --log-file @var{file}
163 Append all logging output to @var{file}. This is very helpful in
164 seeing what the agent actually does. Use @file{socket://} to log to
167 @item --debug-level @var{level}
169 Select the debug level for investigating problems. @var{level} may be a
170 numeric value or by a keyword:
174 No debugging at all. A value of less than 1 may be used instead of
177 Some basic debug messages. A value between 1 and 2 may be used
178 instead of the keyword.
180 More verbose debug messages. A value between 3 and 5 may be used
181 instead of the keyword.
183 Even more detailed messages. A value between 6 and 8 may be used
184 instead of the keyword.
186 All of the debug messages you can get. A value greater than 8 may be
187 used instead of the keyword. The creation of hash tracing files is
188 only enabled if the keyword is used.
191 How these messages are mapped to the actual debugging flags is not
192 specified and may change with newer releases of this program. They are
193 however carefully selected to best aid in debugging.
195 @item --debug @var{flags}
197 This option is only useful for debugging and the behavior may change at
198 any time without notice. FLAGS are bit encoded and may be given in
203 Same as @code{--debug=0xffffffff}
205 @item --gnutls-debug @var{level}
206 @opindex gnutls-debug
207 Enable debugging of GNUTLS at @var{level}.
209 @item --debug-wait @var{n}
211 When running in server mode, wait @var{n} seconds before entering the
212 actual processing loop and print the pid. This gives time to attach a
215 @item --disable-check-own-socket
216 @opindex disable-check-own-socket
217 On some platforms @command{dirmngr} is able to detect the removal of
218 its socket file and shutdown itself. This option disable this
219 self-test for debugging purposes.
229 Format the info output in daemon mode for use with the standard Bourne
230 shell respective the C-shell. The default is to guess it based on the
231 environment variable @code{SHELL} which is in almost all cases
236 Enabling this option forces loading of expired CRLs; this is only
237 useful for debugging.
241 This option switches Dirmngr and thus GnuPG into ``Tor mode'' to route
242 all network access via Tor (an anonymity network). Certain other
243 features are disabled if this mode is active.
245 @item --standard-resolver
246 @opindex standard-resolver
247 This option forces the use of the system's standard DNS resolver code.
248 This is mainly used for debugging. Note that on Windows a standard
249 resolver is not used and all DNS access will return the error ``Not
250 Implemented'' if this function is used.
252 @item --recursive-resolver
253 @opindex recursive-resolver
254 When possible use a recursive resolver instead of a stub resolver.
256 @item --resolver-timeout @var{n}
257 Set the timeout for the DNS resolver to N seconds. The default are 30
260 @item --allow-version-check
261 @opindex allow-version-check
262 Allow Dirmngr to connect to @code{https://versions.gnupg.org} to get
263 the list of current software versions. If this option is enabled, or
264 if @option{use-tor} is active, the list is retrieved when the local
265 copy does not exist or is older than 5 to 7 days. See the option
266 @option{--query-swdb} of the command @command{gpgconf} for more
269 @item --keyserver @var{name}
271 Use @var{name} as your keyserver. This is the server that @command{gpg}
272 communicates with to receive keys, send keys, and search for
273 keys. The format of the @var{name} is a URI:
274 `scheme:[//]keyservername[:port]' The scheme is the type of keyserver:
275 "hkp" for the HTTP (or compatible) keyservers, "ldap" for the LDAP
276 keyservers, or "mailto" for the Graff email keyserver. Note that your
277 particular installation of GnuPG may have other keyserver types
278 available as well. Keyserver schemes are case-insensitive. After the
279 keyserver name, optional keyserver configuration options may be
280 provided. These are the same as the @option{--keyserver-options} of
281 @command{gpg}, but apply only to this particular keyserver.
283 Most keyservers synchronize with each other, so there is generally no
284 need to send keys to more than one server. The keyserver
285 @code{hkp://keys.gnupg.net} uses round robin DNS to give a different
286 keyserver each time you use it.
288 If exactly two keyservers are configured and only one is a Tor hidden
289 service (.onion), Dirmngr selects the keyserver to use depending on
290 whether Tor is locally running or not. The check for a running Tor is
291 done for each new connection.
293 If no keyserver is explicitly configured, dirmngr will use the
294 built-in default of hkps://hkps.pool.sks-keyservers.net.
296 @item --nameserver @var{ipaddr}
298 In ``Tor mode'' Dirmngr uses a public resolver via Tor to resolve DNS
299 names. If the default public resolver, which is @code{8.8.8.8}, shall
300 not be used a different one can be given using this option. Note that
301 a numerical IP address must be given (IPv6 or IPv4) and that no error
302 checking is done for @var{ipaddr}.
305 @opindex disable-ldap
306 Entirely disables the use of LDAP.
309 @opindex disable-http
310 Entirely disables the use of HTTP.
312 @item --ignore-http-dp
313 @opindex ignore-http-dp
314 When looking for the location of a CRL, the to be tested certificate
315 usually contains so called @dfn{CRL Distribution Point} (DP) entries
316 which are URLs describing the way to access the CRL. The first found DP
317 entry is used. With this option all entries using the @acronym{HTTP}
318 scheme are ignored when looking for a suitable DP.
320 @item --ignore-ldap-dp
321 @opindex ignore-ldap-dp
322 This is similar to @option{--ignore-http-dp} but ignores entries using
323 the @acronym{LDAP} scheme. Both options may be combined resulting in
324 ignoring DPs entirely.
326 @item --ignore-ocsp-service-url
327 @opindex ignore-ocsp-service-url
328 Ignore all OCSP URLs contained in the certificate. The effect is to
329 force the use of the default responder.
331 @item --honor-http-proxy
332 @opindex honor-http-proxy
333 If the environment variable @env{http_proxy} has been set, use its
334 value to access HTTP servers.
336 @item --http-proxy @var{host}[:@var{port}]
339 Use @var{host} and @var{port} to access HTTP servers. The use of this
340 option overrides the environment variable @env{http_proxy} regardless
341 whether @option{--honor-http-proxy} has been set.
344 @item --ldap-proxy @var{host}[:@var{port}]
346 Use @var{host} and @var{port} to connect to LDAP servers. If @var{port}
347 is omitted, port 389 (standard LDAP port) is used. This overrides any
348 specified host and port part in a LDAP URL and will also be used if host
349 and port have been omitted from the URL.
351 @item --only-ldap-proxy
352 @opindex only-ldap-proxy
353 Never use anything else but the LDAP "proxy" as configured with
354 @option{--ldap-proxy}. Usually @command{dirmngr} tries to use other
355 configured LDAP server if the connection using the "proxy" failed.
358 @item --ldapserverlist-file @var{file}
359 @opindex ldapserverlist-file
360 Read the list of LDAP servers to consult for CRLs and certificates from
361 file instead of the default per-user ldap server list file. The default
362 value for @var{file} is @file{dirmngr_ldapservers.conf}.
364 This server list file contains one LDAP server per line in the format
366 @sc{hostname:port:username:password:base_dn}
368 Lines starting with a @samp{#} are comments.
370 Note that as usual all strings entered are expected to be UTF-8 encoded.
371 Obviously this will lead to problems if the password has originally been
372 encoded as Latin-1. There is no other solution here than to put such a
373 password in the binary encoding into the file (i.e. non-ascii characters
374 won't show up readable).@footnote{The @command{gpgconf} tool might be
375 helpful for frontends as it enables editing this configuration file using
376 percent-escaped strings.}
379 @item --ldaptimeout @var{secs}
381 Specify the number of seconds to wait for an LDAP query before timing
382 out. The default is currently 100 seconds. 0 will never timeout.
387 This option makes dirmngr add any servers it discovers when validating
388 certificates against CRLs to the internal list of servers to consult for
389 certificates and CRLs.
391 This option is useful when trying to validate a certificate that has
392 a CRL distribution point that points to a server that is not already
393 listed in the ldapserverlist. Dirmngr will always go to this server and
394 try to download the CRL, but chances are high that the certificate used
395 to sign the CRL is located on the same server. So if dirmngr doesn't add
396 that new server to list, it will often not be able to verify the
397 signature of the CRL unless the @code{--add-servers} option is used.
399 Note: The current version of dirmngr has this option disabled by default.
404 This option enables OCSP support if requested by the client.
406 OCSP requests are rejected by default because they may violate the
407 privacy of the user; for example it is possible to track the time when
408 a user is reading a mail.
411 @item --ocsp-responder @var{url}
412 @opindex ocsp-responder
413 Use @var{url} as the default OCSP Responder if the certificate does
414 not contain information about an assigned responder. Note, that
415 @code{--ocsp-signer} must also be set to a valid certificate.
417 @item --ocsp-signer @var{fpr}|@var{file}
419 Use the certificate with the fingerprint @var{fpr} to check the
420 responses of the default OCSP Responder. Alternatively a filename can be
421 given in which case the response is expected to be signed by one of the
422 certificates described in that file. Any argument which contains a
423 slash, dot or tilde is considered a filename. Usual filename expansion
424 takes place: A tilde at the start followed by a slash is replaced by the
425 content of @env{HOME}, no slash at start describes a relative filename
426 which will be searched at the home directory. To make sure that the
427 @var{file} is searched in the home directory, either prepend the name
428 with "./" or use a name which contains a dot.
430 If a response has been signed by a certificate described by these
431 fingerprints no further check upon the validity of this certificate is
434 The format of the @var{FILE} is a list of SHA-1 fingerprint, one per
435 line with optional colons between the bytes. Empty lines and lines
436 prefix with a hash mark are ignored.
439 @item --ocsp-max-clock-skew @var{n}
440 @opindex ocsp-max-clock-skew
441 The number of seconds a skew between the OCSP responder and them local
442 clock is accepted. Default is 600 (10 minutes).
444 @item --ocsp-max-period @var{n}
445 @opindex ocsp-max-period
446 Seconds a response is at maximum considered valid after the time given
447 in the thisUpdate field. Default is 7776000 (90 days).
449 @item --ocsp-current-period @var{n}
450 @opindex ocsp-current-period
451 The number of seconds an OCSP response is considered valid after the
452 time given in the NEXT_UPDATE datum. Default is 10800 (3 hours).
455 @item --max-replies @var{n}
457 Do not return more that @var{n} items in one query. The default is
460 @item --ignore-cert-extension @var{oid}
461 @opindex ignore-cert-extension
462 Add @var{oid} to the list of ignored certificate extensions. The
463 @var{oid} is expected to be in dotted decimal form, like
464 @code{2.5.29.3}. This option may be used more than once. Critical
465 flagged certificate extensions matching one of the OIDs in the list
466 are treated as if they are actually handled and thus the certificate
467 won't be rejected due to an unknown critical extension. Use this
468 option with care because extensions are usually flagged as critical
471 @item --hkp-cacert @var{file}
472 Use the root certificates in @var{file} for verification of the TLS
473 certificates used with @code{hkps} (keyserver access over TLS). If
474 the file is in PEM format a suffix of @code{.pem} is expected for
475 @var{file}. This option may be given multiple times to add more
476 root certificates. Tilde expansion is supported.
478 If no @code{hkp-cacert} directive is present, dirmngr will make a
479 reasonable choice: if the keyserver in question is the special pool
480 @code{hkps.pool.sks-keyservers.net}, it will use the bundled root
481 certificate for that pool. Otherwise, it will use the system CAs.
487 @c Dirmngr Configuration
490 @node Dirmngr Configuration
491 @section Configuration
493 Dirmngr makes use of several directories when running in daemon mode:
498 This is the standard home directory for all configuration files.
500 @item /etc/gnupg/trusted-certs
501 This directory should be filled with certificates of Root CAs you
502 are trusting in checking the CRLs and signing OCSP Responses.
504 Usually these are the same certificates you use with the applications
505 making use of dirmngr. It is expected that each of these certificate
506 files contain exactly one @acronym{DER} encoded certificate in a file
507 with the suffix @file{.crt} or @file{.der}. @command{dirmngr} reads
508 those certificates on startup and when given a SIGHUP. Certificates
509 which are not readable or do not make up a proper X.509 certificate
510 are ignored; see the log file for details.
512 Applications using dirmngr (e.g. gpgsm) can request these
513 certificates to complete a trust chain in the same way as with the
514 extra-certs directory (see below).
516 Note that for OCSP responses the certificate specified using the option
517 @option{--ocsp-signer} is always considered valid to sign OCSP requests.
519 @item /etc/gnupg/extra-certs
520 This directory may contain extra certificates which are preloaded
521 into the internal cache on startup. Applications using dirmngr (e.g. gpgsm)
522 can request cached certificates to complete a trust chain.
523 This is convenient in cases you have a couple intermediate CA certificates
524 or certificates usually used to sign OCSP responses.
525 These certificates are first tried before going
526 out to the net to look for them. These certificates must also be
527 @acronym{DER} encoded and suffixed with @file{.crt} or @file{.der}.
529 @item ~/.gnupg/crls.d
530 This directory is used to store cached CRLs. The @file{crls.d}
531 part will be created by dirmngr if it does not exists but you need to
532 make sure that the upper directory exists.
537 To be able to see what's going on you should create the configure file
538 @file{~/gnupg/dirmngr.conf} with at least one line:
541 log-file ~/dirmngr.log
544 To be able to perform OCSP requests you probably want to add the line:
550 To make sure that new options are read and that after the installation
551 of a new GnuPG versions the installed dirmngr is running, you may want
552 to kill an existing dirmngr first:
555 gpgconf --kill dirmngr
558 You may check the log file to see whether all desired root
559 certificates have been loaded correctly.
566 @node Dirmngr Signals
567 @section Use of signals
569 A running @command{dirmngr} may be controlled by signals, i.e. using
570 the @command{kill} command to send a signal to the process.
572 Here is a list of supported signals:
578 This signal flushes all internally cached CRLs as well as any cached
579 certificates. Then the certificate cache is reinitialized as on
580 startup. Options are re-read from the configuration file. Instead of
581 sending this signal it is better to use
583 gpgconf --reload dirmngr
588 Shuts down the process but waits until all current requests are
589 fulfilled. If the process has received 3 of these signals and requests
590 are still pending, a shutdown is forced. You may also use
592 gpgconf --kill dirmngr
594 instead of this signal
598 Shuts down the process immediately.
603 This prints some caching statistics to the log file.
613 @node Dirmngr Examples
616 Here is an example on how to show dirmngr's internal table of OpenPGP
617 keyserver addresses. The output is intended for debugging purposes
618 and not part of a defined API.
621 gpg-connect-agent --dirmngr 'keyserver --hosttable' /bye
624 To inhibit the use of a particular host you have noticed in one of the
625 keyserver pools, you may use
628 gpg-connect-agent --dirmngr 'keyserver --dead pgpkeys.bnd.de' /bye
631 The description of the @code{keyserver} command can be printed using
634 gpg-connect-agent --dirmngr 'help keyserver' /bye
643 @node Dirmngr Protocol
644 @section Dirmngr's Assuan Protocol
646 Assuan is the IPC protocol used to access dirmngr. This is a
647 description of the commands implemented by dirmngr.
650 * Dirmngr LOOKUP:: Look up a certificate via LDAP
651 * Dirmngr ISVALID:: Validate a certificate using a CRL or OCSP.
652 * Dirmngr CHECKCRL:: Validate a certificate using a CRL.
653 * Dirmngr CHECKOCSP:: Validate a certificate using OCSP.
654 * Dirmngr CACHECERT:: Put a certificate into the internal cache.
655 * Dirmngr VALIDATE:: Validate a certificate for debugging.
659 @subsection Return the certificate(s) found
661 Lookup certificate. To allow multiple patterns (which are ORed)
662 quoting is required: Spaces are to be translated into "+" or into
663 "%20"; obviously this requires that the usual escape quoting rules
664 are applied. The server responds with:
667 S: D <DER encoded certificate>
669 S: D <second DER encoded certificate>
674 In this example 2 certificates are returned. The server may return
675 any number of certificates; OK will also be returned when no
676 certificates were found. The dirmngr might return a status line
683 To indicate that the output was truncated to N items due to a
684 limitation of the server or by an arbitrary set limit.
686 The option @option{--url} may be used if instead of a search pattern a
687 complete URL to the certificate is known:
690 C: LOOKUP --url CN%3DWerner%20Koch,o%3DIntevation%20GmbH,c%3DDE?userCertificate
693 If the option @option{--cache-only} is given, no external lookup is done
694 so that only certificates from the cache are returned.
696 With the option @option{--single}, the first and only the first match
697 will be returned. Unless option @option{--cache-only} is also used, no
698 local lookup will be done in this case.
702 @node Dirmngr ISVALID
703 @subsection Validate a certificate using a CRL or OCSP
706 ISVALID [--only-ocsp] [--force-default-responder] @var{certid}|@var{certfpr}
709 Check whether the certificate described by the @var{certid} has been
710 revoked. Due to caching, the Dirmngr is able to answer immediately in
713 The @var{certid} is a hex encoded string consisting of two parts,
714 delimited by a single dot. The first part is the SHA-1 hash of the
715 issuer name and the second part the serial number.
717 Alternatively the certificate's SHA-1 fingerprint @var{certfpr} may be
718 given in which case an OCSP request is done before consulting the CRL.
719 If the option @option{--only-ocsp} is given, no fallback to a CRL check
720 will be used. If the option @option{--force-default-responder} is
721 given, only the default OCSP responder will be used and any other
722 methods of obtaining an OCSP responder URL won't be used.
725 Common return values are:
728 @item GPG_ERR_NO_ERROR (0)
729 This is the positive answer: The certificate is not revoked and we have
730 an up-to-date revocation list for that certificate. If OCSP was used
731 the responder confirmed that the certificate has not been revoked.
733 @item GPG_ERR_CERT_REVOKED
734 This is the negative answer: The certificate has been revoked. Either
735 it is in a CRL and that list is up to date or an OCSP responder informed
736 us that it has been revoked.
738 @item GPG_ERR_NO_CRL_KNOWN
739 No CRL is known for this certificate or the CRL is not valid or out of
742 @item GPG_ERR_NO_DATA
743 The OCSP responder returned an ``unknown'' status. This means that it
744 is not aware of the certificate's status.
746 @item GPG_ERR_NOT_SUPPORTED
747 This is commonly seen if OCSP support has not been enabled in the
751 If DirMngr has not enough information about the given certificate (which
752 is the case for not yet cached certificates), it will will inquire the
756 S: INQUIRE SENDCERT <CertID>
757 C: D <DER encoded certificate>
761 A client should be aware that DirMngr may ask for more than one
764 If Dirmngr has a certificate but the signature of the certificate
765 could not been validated because the root certificate is not known to
766 dirmngr as trusted, it may ask back to see whether the client trusts
767 this the root certificate:
770 S: INQUIRE ISTRUSTED <CertHexfpr>
775 Only this answer will let Dirmngr consider the certificate as valid.
778 @node Dirmngr CHECKCRL
779 @subsection Validate a certificate using a CRL
781 Check whether the certificate with FINGERPRINT (SHA-1 hash of the
782 entire X.509 certificate blob) is valid or not by consulting the CRL
783 responsible for this certificate. If the fingerprint has not been
784 given or the certificate is not known, the function inquires the
788 S: INQUIRE TARGETCERT
789 C: D <DER encoded certificate>
793 Thus the caller is expected to return the certificate for the request
794 (which should match FINGERPRINT) as a binary blob. Processing then
795 takes place without further interaction; in particular dirmngr tries
796 to locate other required certificate by its own mechanism which
797 includes a local certificate store as well as a list of trusted root
801 The return code is 0 for success; i.e. the certificate has not been
802 revoked or one of the usual error codes from libgpg-error.
804 @node Dirmngr CHECKOCSP
805 @subsection Validate a certificate using OCSP
808 CHECKOCSP [--force-default-responder] [@var{fingerprint}]
811 Check whether the certificate with @var{fingerprint} (the SHA-1 hash of
812 the entire X.509 certificate blob) is valid by consulting the appropriate
813 OCSP responder. If the fingerprint has not been given or the
814 certificate is not known by Dirmngr, the function inquires the
818 S: INQUIRE TARGETCERT
819 C: D <DER encoded certificate>
823 Thus the caller is expected to return the certificate for the request
824 (which should match @var{fingerprint}) as a binary blob. Processing
825 then takes place without further interaction; in particular dirmngr
826 tries to locate other required certificates by its own mechanism which
827 includes a local certificate store as well as a list of trusted root
830 If the option @option{--force-default-responder} is given, only the
831 default OCSP responder is used. This option is the per-command variant
832 of the global option @option{--ignore-ocsp-service-url}.
836 The return code is 0 for success; i.e. the certificate has not been
837 revoked or one of the usual error codes from libgpg-error.
839 @node Dirmngr CACHECERT
840 @subsection Put a certificate into the internal cache
842 Put a certificate into the internal cache. This command might be
843 useful if a client knows in advance certificates required for a test and
844 wants to make sure they get added to the internal cache. It is also
845 helpful for debugging. To get the actual certificate, this command
846 immediately inquires it using
849 S: INQUIRE TARGETCERT
850 C: D <DER encoded certificate>
854 Thus the caller is expected to return the certificate for the request
858 The return code is 0 for success; i.e. the certificate has not been
859 successfully cached or one of the usual error codes from libgpg-error.
861 @node Dirmngr VALIDATE
862 @subsection Validate a certificate for debugging
864 Validate a certificate using the certificate validation function used
865 internally by dirmngr. This command is only useful for debugging. To
866 get the actual certificate, this command immediately inquires it using
869 S: INQUIRE TARGETCERT
870 C: D <DER encoded certificate>
874 Thus the caller is expected to return the certificate for the request
881 @command{dirmngr-client}(1)
883 @include see-also-note.texi
886 @c !!! UNDER CONSTRUCTION !!!
889 @c @section Verifying a Certificate
891 @c There are several ways to request services from Dirmngr. Almost all of
892 @c them are done using the Assuan protocol. What we describe here is the
893 @c Assuan command CHECKCRL as used for example by the dirmnr-client tool if
897 @c dirmngr-client foo.crt
900 @c This command will send an Assuan request to an already running Dirmngr
901 @c instance. foo.crt is expected to be a standard X.509 certificate and
902 @c dirmngr will receive the Assuan command
905 @c CHECKCRL @var [{fingerprint}]
908 @c @var{fingerprint} is optional and expected to be the SHA-1 has of the
909 @c DER encoding of the certificate under question. It is to be HEX
910 @c encoded. The rationale for sending the fingerprint is that it allows
911 @c dirmngr to reply immediately if it has already cached such a request. If
912 @c this is not the case and no certificate has been found in dirmngr's
913 @c internal certificate storage, dirmngr will request the certificate using
914 @c the Assuan inquiry
917 @c INQUIRE TARGETCERT
920 @c The caller (in our example dirmngr-client) is then expected to return
921 @c the certificate for the request (which should match @var{fingerprint})
924 @c Dirmngr now passes control to @code{crl_cache_cert_isvalid}. This
925 @c function checks whether a CRL item exists for target certificate. These
926 @c CRL items are kept in a database of already loaded and verified CRLs.
927 @c This mechanism is called the CRL cache. Obviously timestamps are kept
928 @c there with each item to cope with the expiration date of the CRL. The
929 @c possible return values are: @code{0} to indicate that a valid CRL is
930 @c available for the certificate and the certificate itself is not listed
931 @c in this CRL, @code{GPG_ERR_CERT_REVOKED} to indicate that the certificate is
932 @c listed in the CRL or @code{GPG_ERR_NO_CRL_KNOWN} in cases where no CRL or no
933 @c information is available. The first two codes are immediately returned to
934 @c the caller and the processing of this request has been done.
936 @c Only the @code{GPG_ERR_NO_CRL_KNOWN} needs more attention: Dirmngr now
937 @c calls @code{clr_cache_reload_crl} and if this succeeds calls
938 @c @code{crl_cache_cert_isvald) once more. All further errors are
939 @c immediately returned to the caller.
941 @c @code{crl_cache_reload_crl} is the actual heart of the CRL management.
942 @c It locates the corresponding CRL for the target certificate, reads and
943 @c verifies this CRL and stores it in the CRL cache. It works like this:
945 @c * Loop over all crlDPs in the target certificate.
946 @c * If the crlDP is invalid immediately terminate the loop.
947 @c * Loop over all names in the current crlDP.
948 @c * If the URL scheme is unknown or not enabled
949 @c (--ignore-http-dp, --ignore-ldap-dp) continues with
951 @c * @code{crl_fetch} is called to actually retrieve the CRL.
952 @c In case of problems this name is ignore and we continue with
953 @c the next name. Note that @code{crl_fetch} does only return
954 @c a descriptor for the CRL for further reading so does the CRL
955 @c does not yet end up in memory.
956 @c * @code{crl_cache_insert} is called with that descriptor to
957 @c actually read the CRL into the cache. See below for a
958 @c description of this function. If there is any error (e.g. read
959 @c problem, CRL not correctly signed or verification of signature
960 @c not possible), this descriptor is rejected and we continue
961 @c with the next name. If the CRL has been successfully loaded,
962 @c the loop is terminated.
963 @c * If no crlDP has been found in the previous loop use a default CRL.
964 @c Note, that if any crlDP has been found but loading of the CRL failed,
965 @c this condition is not true.
966 @c * Try to load a CRL from all configured servers (ldapservers.conf)
967 @c in turn. The first server returning a CRL is used.
968 @c * @code(crl_cache_insert) is then used to actually insert the CRL
969 @c into the cache. If this failed we give up immediately without
970 @c checking the rest of the servers from the first step.
974 @c The @code{crl_cache_insert} function takes care of reading the bulk of
975 @c the CRL, parsing it and checking the signature. It works like this: A
976 @c new database file is created using a temporary file name. The CRL
977 @c parsing machinery is started and all items of the CRL are put into
978 @c this database file. At the end the issuer certificate of the CRL
979 @c needs to be retrieved. Three cases are to be distinguished:
981 @c a) An authorityKeyIdentifier with an issuer and serialno exits: The
982 @c certificate is retrieved using @code{find_cert_bysn}. If
983 @c the certificate is in the certificate cache, it is directly
984 @c returned. Then the requester (i.e. the client who requested the
985 @c CRL check) is asked via the Assuan inquiry ``SENDCERT'' whether
986 @c he can provide this certificate. If this succeed the returned
987 @c certificate gets cached and returned. Note, that dirmngr does not
988 @c verify in any way whether the expected certificate is returned.
989 @c It is in the interest of the client to return a useful certificate
990 @c as otherwise the service request will fail due to a bad signature.
991 @c The last way to get the certificate is by looking it up at
992 @c external resources. This is done using the @code{ca_cert_fetch}
993 @c and @code{fetch_next_ksba_cert} and comparing the returned
994 @c certificate to match the requested issuer and seriano (This is
995 @c needed because the LDAP layer may return several certificates as
996 @c LDAP as no standard way to retrieve by serial number).
998 @c b) An authorityKeyIdentifier with a key ID exists: The certificate is
999 @c retrieved using @code{find_cert_bysubject}. If the certificate is
1000 @c in the certificate cache, it is directly returned. Then the
1001 @c requester is asked via the Assuan inquiry ``SENDCERT_SKI'' whether
1002 @c he can provide this certificate. If this succeed the returned
1003 @c certificate gets cached and returned. Note, that dirmngr does not
1004 @c verify in any way whether the expected certificate is returned.
1005 @c It is in the interest of the client to return a useful certificate
1006 @c as otherwise the service request will fail due to a bad signature.
1007 @c The last way to get the certificate is by looking it up at
1008 @c external resources. This is done using the @code{ca_cert_fetch}
1009 @c and @code{fetch_next_ksba_cert} and comparing the returned
1010 @c certificate to match the requested subject and key ID.
1012 @c c) No authorityKeyIdentifier exits: The certificate is retrieved
1013 @c using @code{find_cert_bysubject} without the key ID argument. If
1014 @c the certificate is in the certificate cache the first one with a
1015 @c matching subject is is directly returned. Then the requester is
1016 @c asked via the Assuan inquiry ``SENDCERT'' and an exact
1017 @c specification of the subject whether he can
1018 @c provide this certificate. If this succeed the returned
1019 @c certificate gets cached and returned. Note, that dirmngr does not
1020 @c verify in any way whether the expected certificate is returned.
1021 @c It is in the interest of the client to return a useful certificate
1022 @c as otherwise the service request will fail due to a bad signature.
1023 @c The last way to get the certificate is by looking it up at
1024 @c external resources. This is done using the @code{ca_cert_fetch}
1025 @c and @code{fetch_next_ksba_cert} and comparing the returned
1026 @c certificate to match the requested subject; the first certificate
1027 @c with a matching subject is then returned.
1029 @c If no certificate was found, the function returns with the error
1030 @c GPG_ERR_MISSING_CERT. Now the signature is verified. If this fails,
1031 @c the erro is returned. On success the @code{validate_cert_chain} is
1032 @c used to verify that the certificate is actually valid.
1034 @c Here we may encounter a recursive situation:
1035 @c @code{validate_cert_chain} needs to look at other certificates and
1036 @c also at CRLs to check whether these other certificates and well, the
1037 @c CRL issuer certificate itself are not revoked. FIXME: We need to make
1038 @c sure that @code{validate_cert_chain} does not try to lookup the CRL we
1039 @c are currently processing. This would be a catch-22 and may indicate a
1040 @c broken PKI. However, due to overlapping expiring times and imprecise
1041 @c clocks this may actually happen.
1043 @c For historical reasons the Assuan command ISVALID is a bit different
1044 @c to CHECKCRL but this is mainly due to different calling conventions.
1045 @c In the end the same fucntionality is used, albeit hidden by a couple
1046 @c of indirection and argument and result code mangling. It furthere
1047 @c ingetrages OCSP checking depending on options are the way it is
1048 @c called. GPGSM still uses this command but might eventuall switch over
1049 @c to CHECKCRL and CHECKOCSP so that ISVALID can be retired.
1052 @c @section Validating a certificate
1054 @c We describe here how the internal function @code{validate_cert_chain}
1055 @c works. Note that mainly testing purposes this functionality may be
1056 @c called directly using @cmd{dirmngr-client --validate @file{foo.crt}}.
1058 @c The function takes the target certificate and a mode argument as
1059 @c parameters and returns an error code and optionally the closes
1060 @c expiration time of all certificates in the chain.
1062 @c We first check that the certificate may be used for the requested
1063 @c purpose (i.e. OCSP or CRL signing). If this is not the case
1064 @c GPG_ERR_WRONG_KEY_USAGE is returned.
1066 @c The next step is to find the trust anchor (root certificate) and to
1067 @c assemble the chain in memory: Starting with the target certificate,
1068 @c the expiration time is checked against the current date, unknown
1069 @c critical extensions are detected and certificate policies are matched
1070 @c (We only allow 2.289.9.9 but I have no clue about that OID and from
1071 @c where I got it - it does not even seem to be assigned - debug cruft?).
1073 @c Now if this certificate is a self-signed one, we have reached the
1074 @c trust anchor. In this case we check that the signature is good, the
1075 @c certificate is allowed to act as a CA, that it is a trusted one (by
1076 @c checking whether it is has been put into the trusted-certs
1077 @c configuration directory) and finally prepend into to our list
1078 @c representing the certificate chain. This steps ends then.
1080 @c If it is not a self-signed certificate, we check that the chain won't
1081 @c get too long (current limit is 100), if this is the case we terminate
1082 @c with the error GPG_ERR_BAD_CERT_CHAIN.
1084 @c Now the issuer's certificate is looked up: If an
1085 @c authorityKeyIdentifier is available, this one is used to locate the
1086 @c certificate either using issuer and serialnumber or subject DN
1087 @c (i.e. the issuer's DN) and the keyID. The functions
1088 @c @code{find_cert_bysn) and @code{find_cert_bysubject} are used
1089 @c respectively. The have already been described above under the
1090 @c description of @code{crl_cache_insert}. If no certificate was found
1091 @c or with no authorityKeyIdentifier, only the cache is consulted using
1092 @c @code{get_cert_bysubject}. The latter is is done under the assumption
1093 @c that a matching certificate has explicitly been put into the
1094 @c certificate cache. If the issuer's certificate could not be found,
1095 @c the validation terminates with the error code @code{GPG_ERR_MISSING_CERT}.
1097 @c If the issuer's certificate has been found, the signature of the
1098 @c actual certificate is checked and in case this fails the error
1099 @c #code{GPG_ERR_BAD_CERT_CHAIN} is returned. If the signature checks out, the
1100 @c maximum chain length of the issuing certificate is checked as well as
1101 @c the capability of the certificate (i.e. whether he may be used for
1102 @c certificate signing). Then the certificate is prepended to our list
1103 @c representing the certificate chain. Finally the loop is continued now
1104 @c with the issuer's certificate as the current certificate.
1106 @c After the end of the loop and if no error as been encountered
1107 @c (i.e. the certificate chain has been assempled correctly), a check is
1108 @c done whether any certificate expired or a critical policy has not been
1109 @c met. In any of these cases the validation terminates with an
1110 @c appropriate error.
1112 @c Finally the function @code{check_revocations} is called to verify no
1113 @c certificate in the assempled chain has been revoked: This is an
1114 @c recursive process because a CRL has to be checked for each certificate
1115 @c in the chain except for the root certificate, of which we already know
1116 @c that it is trusted and we avoid checking a CRL here due to common
1117 @c setup problems and the assumption that a revoked root certifcate has
1118 @c been removed from the list of trusted certificates.
1123 @c @section Looking up certificates through LDAP.
1125 @c This describes the LDAP layer to retrieve certificates.
1126 @c the functions @code{ca_cert_fetch} and @code{fetch_next_ksba_cert} are
1127 @c used for this. The first one starts a search and the second one is
1128 @c used to retrieve certificate after certificate.