source: mod_gnutls/doc/mod_gnutls_manual.md @ 8daef10

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1* * * * *
2
3`mod_gnutls` is a module for the Apache web server that provides HTTPS
4(HTTP over Transport Layer Security (TLS)) using the GnuTLS library.
5More information about the module can be found at
6[the project's website](https://mod.gnutls.org/).
7
8* * * * *
9
10Compilation & Installation
11==========================
12
13`mod_gnutls` uses the `./configure && make && make install` mechanism
14common to many Open Source programs.  Most of the dirty work is
15handled by either `./configure` or Apache's `apxs` utility. If you have
16built Apache modules before, there shouldn't be any surprises for you.
17
18The interesting options you can pass to configure are:
19
20`--with-apxs=PATH` 
21:   This option is used to specify the location of the apxs utility that
22    was installed as part of apache. Specify the location of the
23    binary, not the directory it is located in.
24
25`--with-apu-config=PATH`
26:   Path to APR Utility Library config tool (`apu-1-config`)
27
28`--help`
29:   Provides a list of all available configure options.
30
31It is recommended to run `make check` before installation. If your
32system doesn't have a loopback device with IPv6 and IPv4 support or
33`localhost` does not resolve to at least one of `[::1]` and
34`127.0.0.1`, you may have to set the `TEST_HOST` or `TEST_IP`
35environment variables when running `./configure` to make the test
36suite work correctly.
37
38* * * * *
39
40Integration
41===========
42
43To activate `mod_gnutls` just add the following line to your httpd.conf
44and restart Apache:
45
46    LoadModule gnutls_module modules/mod_gnutls.so
47
48Module Dependencies
49-------------------
50
51`mod_gnutls` uses the Apache HTTPD [Shared Object
52Cache](http://httpd.apache.org/docs/current/en/socache.html) to cache
53[OCSP responses for OCSP stapling](#gnutlsocspcache) and [TLS
54sessions](#gnutlscache). To use either cache you need to load a
55suitable `mod_socache_PROVIDER` module, which should be provided by
56your Apache installation.
57
58It is recommended to load at least `mod_socache_shmcb`. If that module
59is loaded `mod_gnutls` will [enable OCSP stapling by
60default](#gnutlsocspstapling), without needing any further
61configuration other than a [certificate chain](#gnutlscertificatefile)
62with OCSP support.
63
64* * * * *
65
66Configuration Directives
67========================
68
69General Options
70---------------
71
72### GnuTLSEnable
73
74Enable GnuTLS for this virtual host
75
76    GnuTLSEnable [on|off]
77
78Default: *off*\
79Context: virtual host
80
81This directive enables SSL/TLS Encryption for a Virtual Host.
82
83### GnuTLSCache
84
85Configure TLS Session Cache
86
87    GnuTLSCache (shmcb|dbm|memcache|...|none)[:PARAMETERS]
88
89Default: `GnuTLSCache none`\
90Context: server config
91
92This directive configures the TLS Session Cache for `mod_gnutls`. This
93could be shared between machines of different architectures. If the
94selected cache implementation is not thread-safe, access is serialized
95using the `gnutls-cache` mutex.
96
97Which cache implementations are available depends on your Apache
98installation and configuration, `mod_gnutls` can use any socache
99provider. In general you will need to load a `mod_socache_PROVIDER`
100module. Common options are described below, please check the Apache
101HTTPD documentation for details on available providers and their
102configuration.
103
104`shmcb`
105:   Uses a shared memory segment. This is a high performance local
106    cache. The parameter is a relative or absolute path to be used if
107    the local shared memory implementation requires one, followed by
108    the cache size in bytes enclosed in parentheses.
109
110    Example: `shmcb:cache/gnutls_cache(65536)`
111
112`dbm`
113:   Uses a DBM cache file. The parameter is a relative or absolute
114    path to be used as the DBM cache file.
115
116    Example: `dbm:cache/gnutls_cache`
117
118`memcache`
119:   Uses memcached server(s) to cache TLS session data. The parameter
120    is a comma separated list of servers (host:port). This can be used
121    to share a session cache between all servers in a cluster.
122
123    Example: `memcache:memcache.example.com:12345,memcache2.example.com:12345`
124
125`none`
126:   Turns off all caching of TLS sessions.
127
128    This can significantly reduce the performance of `mod_gnutls`
129    since even followup connections by a client must renegotiate
130    parameters instead of reusing old ones. This is the default, since
131    it requires no configuration.
132
133    Session tickets are an alternative to using a session cache,
134    please see `GnuTLSSessionTickets`. Note that for TLS 1.3 GnuTLS
135    supports resumption using session tickets only as of version
136    3.6.4.
137
138### GnuTLSCacheTimeout
139
140Timeout for TLS Session Cache expiration
141
142    GnuTLSCacheTimeout SECONDS
143
144Default: `GnuTLSCacheTimeout 300`\
145Context: server config, virtual host
146
147Sets the expiration timeout for cached TLS sessions.
148
149### GnuTLSSessionTickets
150
151Enable Session Tickets for the server
152
153    GnuTLSSessionTickets [on|off]
154
155Default: `on` with GnuTLS 3.6.4 and newer, `off` otherwise\
156Context: server config, virtual host
157
158Session tickets allow TLS session resumption without session state
159stored on the server, using encrypted tickets provided to the clients
160instead. Tickets are an alternative to using a session cache, and
161currently the only session resumption mechanism in TLS 1.3. For a pool
162of servers this option is not recommended since the tickets are bound
163to the issuing server only.
164
165If this option is set in the global configuration, virtual hosts
166without a `GnuTLSSessionTickets` setting will use the global setting.
167
168*Warning:* With GnuTLS version before 3.6.4 the master key that
169protects the tickets is generated only on server start, and there is
170no mechanism to roll over the key. If session tickets are enabled it
171is highly recommended to restart the server regularly to protect past
172sessions in case an attacker gains access to server memory. GnuTLS
1733.6.4 introduced an automatic TOTP-based key rollover, so this warning
174does not apply any more and tickets are enabled by default.
175
176### GnuTLSDHFile
177
178Use the provided PKCS \#3 encoded Diffie-Hellman parameters
179
180    GnuTLSDHFile FILEPATH
181
182Default: *none*\
183Context: server config, virtual host
184
185By default `mod_gnutls` uses the DH parameters included with GnuTLS
186corresponding to the security level of the configured private keys.
187
188If you need to use different DH parameters, you can provide a PEM file
189containing them in PKCS \#3 encoding using this option. Please see the
190"[Parameter
191generation](https://gnutls.org/manual/html_node/Parameter-generation.html)"
192section of the GnuTLS documentation for a short discussion of the
193security implications.
194
195### GnuTLSPriorities
196
197Set the allowed protocol versions, ciphers, key exchange algorithms,
198MACs and compression methods
199
200    GnuTLSPriorities NORMAL:+CIPHER_0:+CIPHER_1:...:+CIPHER_N
201
202Default: `NORMAL`\
203Context: server config, virtual host
204
205Sets the allowed protocol version(s), ciphers, key exchange methods,
206message authentication codes, and other TLS parameters for the server.
207The parameter is a GnuTLS priority string as described in the
208[the GnuTLS documentation](https://gnutls.org/manual/html_node/Priority-Strings.html).
209
210For example, to disable TLS 1.0 use `NORMAL:-VERS-TLS1.0`.
211
212### GnuTLSP11Module
213
214Load this PKCS #11 module.
215
216    GnuTLSP11Module PATH_TO_LIBRARY
217
218Default: *none*\
219Context: server config
220
221Load this PKCS #11 provider module, instead of the system
222defaults. May occur multiple times to load multiple modules.
223
224### GnuTLSPIN
225
226Set the PIN to be used to access encrypted key files or PKCS #11 objects.
227
228    GnuTLSPIN XXXXXX
229
230Default: *none*\
231Context: server config, virtual host
232
233Takes a string to be used as a PIN for the protected objects in
234a security module, or as a key to be used to decrypt PKCS #8, PKCS #12,
235or openssl encrypted keys.
236
237### GnuTLSSRKPIN
238
239Set the SRK PIN to be used to access the TPM.
240
241    GnuTLSSRKPIN XXXXXX
242
243Default: *none*\
244Context: server config, virtual host
245
246Takes a string to be used as a PIN for the protected objects in
247the TPM module.
248
249### GnuTLSExportCertificates
250
251Export the PEM encoded certificates to CGIs
252
253    GnuTLSExportCertificates [off|on|SIZE]
254
255Default: `off`\
256Context: server config, virtual host
257
258This directive configures exporting the full certificates of the
259server and the client to CGI scripts via the `SSL_SERVER_CERT` and
260`SSL_CLIENT_CERT` environment variables. The exported certificates
261will be PEM-encoded, limited to the given size. The type of the
262certificate will be exported in `SSL_SERVER_CERT_TYPE` and
263`SSL_CLIENT_CERT_TYPE`.
264
265SIZE should be an integer number of bytes, or may be written with a
266trailing `K` to indicate kibibytes.  `off` means the same thing as
267`0`, in which case the certificates will not be exported to the
268environment. `on` is an alias for `16K`. If a non-zero size is
269specified for this directive, but a certificate is too large to fit in
270the buffer, then the corresponding environment variable will contain
271the fixed string `GNUTLS_CERTIFICATE_SIZE_LIMIT_EXCEEDED`.
272
273With GnuTLSExportCertificates enabled, `mod_gnutls` exports the same
274environment variables to the CGI process as `mod_ssl`.
275
276X.509 Certificate Authentication
277--------------------------------
278
279### GnuTLSCertificateFile
280
281Set the PEM encoded server certificate or certificate chain
282
283    GnuTLSCertificateFile FILEPATH
284
285Default: *none*\
286Context: server config, virtual host
287
288FILEPATH is an absolute or relative path to a file containing the
289PEM-encoded X.509 certificate to use as this Server's End Entity (EE)
290certificate, and optionally those of the issuing Certificate
291Authorities (CAs). If the file contains multiple certificates they
292must be ordered from EE to the CA closest to the root CA.
293
294Including the full certificate chain is highly recommended because the
295CA certificates are needed for [OCSP stapling](#ocsp-stapling-configuration).
296
297Since version 0.7 this can be a PKCS #11 URL instead of a file.
298
299On Linux and other Unix-like systems you can create the file with a
300command like this (assuming "CA 1" issued the server certificate and
301has been issued by "Root CA" itself):
302
303        $ cat server.pem ca-1.pem root-ca.pem >server-chain.pem
304
305### GnuTLSKeyFile
306
307Set to the PEM Encoded Server Private Key
308
309    GnuTLSKeyFile FILEPATH
310
311Default: *none*\
312Context: server config, virtual host
313
314Takes an absolute or relative path to the Server Private Key. Set
315`GnuTLSPIN` if the key file is encrypted.
316
317Since version 0.7 this can be a PKCS #11 URL.
318
319**Security Warning:**\
320This private key must be protected. It is read while Apache is still
321running as root, and does not need to be readable by the nobody or
322apache user.
323
324### GnuTLSClientVerify
325
326Enable client certificate verification
327
328    GnuTLSClientVerify [ignore|request|require]
329
330Default: `ignore`\
331Context: server config, virtual host, directory, .htaccess
332
333This directive controls if clients need to authenticate with a
334certificate to access resources. If a mode other than `ignore` is used
335in a directory context the server may request post-handshake
336authentication (TLS 1.3 only, see below). Trusted CAs for certificate
337validation are set using [`GnuTLSClientCAFile`](#gnutlsclientcafile).
338
339`ignore`
340:   `mod_gnutls` will not request certificates from clients, and allow
341    any requests.
342
343`request`
344:   Client certificates will be requested, but requests are still
345    allowed if the client does not send one or the provided
346    certificate is invalid. If the client authenticates, the
347    certificate validation status will be stored in the
348    [`SSL_CLIENT_VERIFY`](#ssl_client_verify) environment variable and
349    can be `SUCCESS`, `FAILED` or `NONE`.
350
351`require`
352:   Client certificate authentication will be required for access. If
353    set at server or virtual host level TLS connections from clients
354    without a valid certificate will be denied. If set at directory
355    level any requests without a valid client certificate will be
356    denied with a 403 Forbidden error. The `SSL_CLIENT_VERIFY`
357    environment variable will be set to `SUCCESS` if access is
358    allowed, additional [environment
359    variables](#environment-variables) will hold details on the client
360    certificate.
361
362When using TLS 1.3 `mod_gnutls` will request [post-handshake
363authentication](https://tools.ietf.org/html/rfc8446#section-4.6.2) as
364necessary if the client announced support during the handshake. With
365TLS versions 1.2 and earlier `mod_gnutls` supports client
366authentication only during the initial handshake.
367
368If you want clients that do not support TLS 1.3 at all or do not
369support the post-handshake authentication extension to have access to
370resources that require authentication, you can set `GnuTLSClientVerify
371request` at the server or virtual host level so clients can
372authenticate during the initial handshake.
373
374### GnuTLSClientCAFile
375
376Set the PEM encoded Certificate Authority list to use for X.509 base
377client authentication
378
379    GnuTLSClientCAFile FILEPATH
380
381Default: *none*
382Context: server config, virtual host
383
384Takes an absolute or relative path to a PEM Encoded Certificate to use
385as a Certificate Authority with Client Certificate Authentication.
386This file may contain a list of trusted authorities.
387
388SRP Authentication
389------------------
390
391### GnuTLSSRPPasswdFile
392
393Set to the SRP password file for SRP ciphersuites
394
395    GnuTLSSRPPasswdFile FILEPATH
396
397Default: *none*\
398Context: server config, virtual host
399
400Takes an absolute or relative path to an SRP password file. This is
401the same format as used in libsrp.  You can generate such file using
402the command `srptool --passwd /etc/tpasswd --passwd-conf
403/etc/tpasswd.conf -u test` to set a password for user test.  This
404password file holds the username, a password verifier and the
405dependency to the SRP parameters.
406
407### GnuTLSSRPPasswdConfFile
408
409Set to the SRP password.conf file for SRP ciphersuites
410
411    GnuTLSSRPPasswdConfFile FILEPATH
412
413Default: *none*\
414Context: server config, virtual host
415
416Takes an absolute or relative path to an SRP password.conf file. This
417is the same format as used in `libsrp`.  You can generate such file
418using the command `srptool --create-conf /etc/tpasswd.conf`.  This
419file holds the SRP parameters and is associate with the password file
420(the verifiers depends on these parameters).
421
422TLS Proxy Configuration
423-----------------------
424
425### GnuTLSProxyEngine
426
427Enable TLS proxy connections for this virtual host
428
429    GnuTLSProxyEngine [on|off]
430
431Default: *off*\
432Context: virtual host
433
434This directive enables support for TLS proxy connections for a virtual
435host.
436
437### GnuTLSProxyCAFile
438
439Set to the PEM encoded Certificate Authority Certificate
440
441    GnuTLSProxyCAFile FILEPATH
442
443Default: *none*\
444Context: server config, virtual host
445
446Takes an absolute or relative path to a PEM encoded certificate to use
447as a Certificate Authority when verifying certificates provided by
448proxy back end servers. This file may contain a list of trusted
449authorities. If not set, verification of TLS back end servers will
450always fail due to lack of a trusted CA.
451
452### GnuTLSProxyCRLFile
453
454Set to the PEM encoded Certificate Revocation List
455
456    GnuTLSProxyCRLFile FILEPATH
457
458Default: *none*\
459Context: server config, virtual host
460
461Takes an absolute or relative path to a PEM encoded Certificate
462Revocation List to use when verifying certificates provided by proxy
463back end servers. The file may contain a list of CRLs.
464
465### GnuTLSProxyCertificateFile
466
467Set to the PEM encoded Client Certificate
468
469    GnuTLSProxyCertificateFile FILEPATH
470
471Default: *none*\
472Context: server config, virtual host
473
474Takes an absolute or relative path to a PEM encoded X.509 certificate
475to use as this Server's End Entity (EE) client certificate for TLS
476client authentication in proxy TLS connections. If you need to supply
477certificates for intermediate Certificate Authorities (iCAs), they
478should be listed in sequence in the file, from EE to the iCA closest
479to the root CA. Optionally, you can also include the root CA's
480certificate as the last certificate in the list.
481
482If not set, TLS client authentication will be disabled for TLS proxy
483connections. If set, `GnuTLSProxyKeyFile` must be set as well to
484provide the matching private key.
485
486### GnuTLSProxyKeyFile
487
488Set to the PEM encoded Private Key
489
490    GnuTLSProxyKeyFile FILEPATH
491
492Default: *none*\
493Context: server config, virtual host
494
495Takes an absolute or relative path to the Private Key matching the
496certificate configured using the `GnuTLSProxyCertificateFile`
497directive. This key cannot currently be password protected.
498
499**Security Warning:**\
500This private key must be protected. It is read while Apache is still
501running as root, and does not need to be readable by the nobody or
502apache user.
503
504### GnuTLSProxyPriorities
505
506Set the allowed ciphers, key exchange algorithms, MACs and compression
507methods for proxy connections
508
509    GnuTLSProxyPriorities NORMAL:+CIPHER_0:+CIPHER_1:...:+CIPHER_N
510
511Default: `NORMAL`\
512Context: server config, virtual host
513
514Sets the allowed protocol version(s), ciphers, key exchange methods,
515message authentication codes, and other TLS parameters for TLS proxy
516connections. Like for `GnuTLSPriorities` the parameter is a GnuTLS
517priority string as described in the
518[the GnuTLS documentation](https://gnutls.org/manual/html_node/Priority-Strings.html).
519
520OCSP Stapling Configuration
521---------------------------
522
523OCSP stapling, formally known as the TLS Certificate Status Request
524extension, allows the server to provide the client with a cached OCSP
525response for its certificate during the handshake. With OCSP stapling
526the client does not have to send an OCSP request to the issuer CA to
527check the certificate status, which offers privacy and performance
528advantages, and avoids the security issue of how to handle errors that
529prevent the client from getting a response.
530
531With TLS 1.2 stapling can be used only for the server certificate,
532with TLS 1.3 mod\_gnutls supports stapling for all certificates in the
533certificate chain except the root CA.
534
535Mod\_gnutls enables OCSP stapling by default if possible. The following
536requirements must be met:
537
538* OCSP responses are verified using the issuer CAs of the certificates
539  being checked, so the CAs must be included in
540  [`GnuTLSCertificateFile`](#gnutlscertificatefile). Providing the
541  whole certificate chain (including the root CA) is recommended.
542
543* Mod\_gnutls needs a cache to store OCSP responses for stapling. If
544  [mod\_socache\_shmcb](http://httpd.apache.org/docs/current/en/mod/mod_socache_shmcb.html)
545  is loaded mod\_gnutls can set up the cache without additional
546  configuration, for other options see
547  [`GnuTLSOCSPCache`](#gnutlsocspcache).
548
549* The certificates must contain OCSP access URIs using HTTP so
550  mod_gnutls can fetch responses, alternatively you may provide
551  responses using [`GnuTLSOCSPResponseFile`](#gnutlsocspresponsefile).
552
553If a server certificate contains the "must-staple" extension (X.509
554TLS Feature extension defined in [RFC
5557633](https://tools.ietf.org/html/rfc7633)) and the configuration does
556not support stapling mod_gnutls will refuse to start.
557
558By default mod\_gnutls regularly refreshes the cached OCSP responses
559in the background, see
560[`GnuTLSOCSPAutoRefresh`](#gnutlsocspautorefresh) for details.
561
562### GnuTLSOCSPStapling
563
564Enable OCSP stapling for this (virtual) host.
565
566    GnuTLSOCSPStapling [On|Off]
567
568Default: *on* if requirements are met, *off* otherwise\
569Context: server config, virtual host
570
571Stapling is activated by default if the requirements [listed
572above](#ocsp-stapling-configuration) are met.
573
574If the server certificate requires stapling ("must-staple") or
575`GnuTLSOCSPStapling` is explicitly set to `on` unmet requirements are
576an error.
577
578OCSP cache updates are serialized using the `gnutls-ocsp` mutex.
579
580### GnuTLSOCSPCache
581
582OCSP stapling cache configuration
583
584        GnuTLSOCSPCache (shmcb|memcache|...|none)[:PARAMETERS]
585
586Default: `shmcb:gnutls_ocsp_cache`\
587Context: server config
588
589This directive configures the OCSP stapling cache, and uses the same
590syntax as `GnuTLSOCSPCache`. Please check there for details.
591
592The default should be reasonable for most servers and requires
593[mod\_socache\_shmcb](http://httpd.apache.org/docs/current/en/mod/mod_socache_shmcb.html)
594to be loaded. Servers with very many virtual hosts may need to
595increase the default cache size via the parameters string, those with
596few virtual hosts and memory constraints could save a few KB by reducing
597it. Note that `mod_socache_dbm` has a size constraint for entries that
598is generally too small for OCSP responses.
599
600If the selected cache implementation is not thread-safe, access
601is serialized using the `gnutls-ocsp-cache` mutex.
602
603### GnuTLSOCSPAutoRefresh
604
605Regularly refresh cached OCSP responses independent of TLS handshakes?
606
607    GnuTLSOCSPAutoRefresh [On|Off]
608
609Default: *on*\
610Context: server config, virtual host
611
612By default `mod_gnutls` will regularly refresh the cached OCSP
613responses, regardless of whether they are used. This has advantages
614over updating OCSP responses only when a TLS handshake needs them:
615
616* Handshakes are not delayed by updating the OCSP response cache
617  first.
618
619* Updating the cached response before it expires can hide short
620  unavailability of the OCSP responder, if a repeated request is
621  successful before the cache expires (see below).
622
623The interval to the next request is determined as follows: After a
624successful OCSP request the next one is scheduled for a random period
625between `GnuTLSOCSPFuzzTime` and half of it before
626`GnuTLSOCSPCacheTimeout` expires. For example, if the cache timeout is
6273600 seconds and the fuzz time 600 seconds, the next request will be
628sent after 3000 to 3300 seconds. If the validity period of the
629response expires before then, the selected interval is halved until it
630is smaller than the time until expiry. If an OCSP request fails, it is
631retried after `GnuTLSOCSPFailureTimeout`.
632
633Regularly updating the OCSP cache requires `mod_watchdog`,
634`mod_gnutls` will fall back to updating the OCSP cache during
635handshakes if `mod_watchdog` is not available or this option is set to
636`Off`.
637
638### GnuTLSOCSPCheckNonce
639
640Check the nonce in OCSP responses?
641
642    GnuTLSOCSPCheckNonce [On|Off]
643
644Default: *on*\
645Context: server config, virtual host
646
647Some CAs refuse to send nonces in their OCSP responses, probably
648because that way they can cache responses. If your CA is one of them
649you can use this flag to disable nonce verification. Note that
650`mod_gnutls` will _send_ a nonce either way.
651
652### GnuTLSOCSPResponseFile
653
654Read OCSP responses for stapling from these files (one or more)
655instead of sending a request over HTTP.
656
657    GnuTLSOCSPResponseFile /path/to/response.der [...]
658
659Default: *empty*\
660Context: server config, virtual host
661
662The first listed file must contain a response for the server
663certificate, responses for intermediate CAs may be added in the order
664they appear in [GnuTLSCertificateFile](#gnutlscertificatefile). You
665can revert to the default fetch mechanism for a specific certificate
666(including the server certificate) by giving the empty string (`""`)
667instead of a file path.
668
669The response files must be updated externally, for example using a
670cron job. This option is an alternative to the server fetching OCSP
671responses over HTTP. Reasons to use this option include:
672
673* Performing OCSP requests separate from the web server (e.g. to share
674  responses across a server cluster).
675* The issuer CA uses an access method other than HTTP, or doesn't
676  include an OCSP URL in the certificate.
677* Testing
678
679You can use a GnuTLS `ocsptool` command like the following to create
680and update the response file:
681
682    ocsptool --ask --nonce --load-issuer ca_cert.pem \
683        --load-cert server_cert.pem --outfile ocsp_response.der
684
685Additional error checking is highly recommended. You may have to
686remove the `--nonce` option if the OCSP responder of your CA does not
687support nonces.
688
689### GnuTLSOCSPCacheTimeout
690
691Cache timeout for OCSP responses
692
693    GnuTLSOCSPCacheTimeout SECONDS
694
695Default: *3600*\
696Context: server config, virtual host
697
698Cached OCSP responses will be refreshed after the configured number of
699seconds. How long this timeout should reasonably be depends on your
700CA, namely how often its OCSP responder is updated and how long
701responses are valid. Note that a response will not be cached beyond
702its lifetime as denoted in the `nextUpdate` field of the response.
703
704### GnuTLSOCSPFailureTimeout
705
706Wait this many seconds before retrying a failed OCSP request.
707
708    GnuTLSOCSPFailureTimeout SECONDS
709
710Default: *300*\
711Context: server config, virtual host
712
713Retries of failed OCSP requests must be rate limited to avoid
714overloading both the server using mod_gnutls and the CA's OCSP
715responder. A shorter value increases the load on both sides, a longer
716one means that stapling will remain disabled for longer after a failed
717request. The auto-refresh mechanism updates OCSP responses before they
718expire and can cover short unavailability of OCSP responders, see
719[`GnuTLSOCSPAutoRefresh`](#gnutlsocspautorefresh) for details.
720
721### GnuTLSOCSPFuzzTime
722
723Update the cached OCSP response up to this time before the cache expires
724
725    GnuTLSOCSPFuzzTime SECONDS
726
727Default: *larger of GnuTLSOCSPCacheTimeout / 8 and GnuTLSOCSPFailureTimeout \* 2*\
728Context: server config, virtual host
729
730Refreshing the cached response before it expires hides short OCSP
731responder unavailability. See `GnuTLSOCSPAutoRefresh` for how this
732value is used, using at least twice `GnuTLSOCSPFailureTimeout` is
733recommended.
734
735### GnuTLSOCSPSocketTimeout
736
737Timeout for TCP sockets used to send OCSP requests
738
739    GnuTLSOCSPFailureTimeout SECONDS
740
741Default: *6*\
742Context: server config, virtual host
743
744Stalled OCSP requests must time out after a while to prevent stalling
745the server too much. However, if the timeout is too short requests may
746fail with a slow OCSP responder or high latency network
747connection. This parameter allows you to adjust the timeout if
748necessary.
749
750Note that this is not an upper limit for the completion of an OCSP
751request but a socket timeout. The connection will time out if there is
752no activity (successful send or receive) at all for the configured
753time.
754
755* * * * *
756
757Configuration Examples
758======================
759
760Minimal Example
761---------------
762
763A minimal server configuration using mod_gnutls might look like this
764(other than the default setup):
765
766```apache
767# Load mod_gnutls into Apache.
768LoadModule gnutls_module modules/mod_gnutls.so
769
770Listen 192.0.2.1:443
771
772<VirtualHost _default_:443>
773        # Standard virtual host stuff
774        DocumentRoot /www/site1.example.com/html
775        ServerName site1.example.com:443
776
777        # Minimal mod_gnutls setup: enable, and set credentials
778        GnuTLSEnable on
779        GnuTLSCertificateFile conf/tls/site1_cert_chain.pem
780        GnuTLSKeyFile conf/tls/site1_key.pem
781</VirtualHost>
782```
783
784This gives you an HTTPS site using the GnuTLS `NORMAL` set of
785ciphersuites. OCSP stapling will be enabled if the server certificate
786contains an OCSP URI, `conf/tls/site1_cert_chain.pem` contains the
787issuer certificate in addition to the server's, and
788[mod\_socache\_shmcb](http://httpd.apache.org/docs/current/en/mod/mod_socache_shmcb.html)
789is loaded. With Gnutls 3.6.4 or newer session tickets are enabled,
790too.
791
792Virtual Hosts with Server Name Indication
793-----------------------------------------
794
795`mod_gnutls` supports Server Name Indication (SNI), as specified in
796[RFC 6066, Section 3](https://tools.ietf.org/html/rfc6066#section-3).
797This allows hosting many TLS websites with a single IP address, you
798can just add virtual host configurations. All recent browsers support
799this standard. Here is an example using SNI:
800
801```apache
802# Load the module into Apache.
803LoadModule gnutls_module modules/mod_gnutls.so
804# This example server uses session tickets, no cache.
805GnuTLSSessionTickets on
806
807# SNI allows hosting multiple sites using one IP address. This
808# could also be 'Listen *:443', just like '*:80' is common for
809# non-HTTPS
810Listen 198.51.100.1:443
811
812<VirtualHost _default_:443>
813        GnuTLSEnable on
814        DocumentRoot /www/site1.example.com/html
815    ServerName site1.example.com:443
816        GnuTLSCertificateFile conf/tls/site1.crt
817        GnuTLSKeyFile conf/tls/site1.key
818</VirtualHost>
819
820<VirtualHost _default_:443>
821        GnuTLSEnable on
822        DocumentRoot /www/site2.example.com/html
823        ServerName site2.example.com:443
824        GnuTLSCertificateFile conf/tls/site2.crt
825        GnuTLSKeyFile conf/tls/site2.key
826</VirtualHost>
827
828<VirtualHost _default_:443>
829        GnuTLSEnable on
830        DocumentRoot /www/site3.example.com/html
831        ServerName site3.example.com:443
832        GnuTLSCertificateFile conf/tls/site3.crt
833        GnuTLSKeyFile conf/tls/site3.key
834        # Enable HTTP/2
835        Protocols h2 http/1.1
836</VirtualHost>
837```
838
839Virtual Hosts without SNI
840-------------------------
841
842If you need to support clients that do not use SNI, you have to use a
843unique IP address/port combination for each virtual host. In this
844example all virtual hosts use the default port for HTTPS (443) and
845different IP addresses.
846
847```apache
848# Load the module into Apache.
849LoadModule gnutls_module modules/mod_gnutls.so
850# This example server uses a session cache.
851GnuTLSCache dbm:/var/cache/www-tls-cache
852GnuTLSCacheTimeout 1200
853
854# Without SNI you need one IP Address per site. The IP addresses
855# are listed separately for clarity, you could also use "Listen 443"
856# to use that port on all available IP addresses.
857Listen 192.0.2.1:443
858Listen 192.0.2.2:443
859Listen 192.0.2.3:443
860
861<VirtualHost 192.0.2.1:443>
862        GnuTLSEnable on
863        GnuTLSPriorities SECURE128
864        DocumentRoot /www/site1.example.com/html
865        ServerName site1.example.com:443
866        GnuTLSCertificateFile conf/tls/site1.crt
867        GnuTLSKeyFile conf/tls/site1.key
868</VirtualHost>
869
870<VirtualHost 192.0.2.2:443>
871    # This virtual host enables SRP authentication
872        GnuTLSEnable on
873        GnuTLSPriorities NORMAL:+SRP
874        DocumentRoot /www/site2.example.com/html
875        ServerName site2.example.com:443
876        GnuTLSSRPPasswdFile conf/tls/tpasswd.site2
877        GnuTLSSRPPasswdConfFile conf/tls/tpasswd.site2.conf
878</VirtualHost>
879
880<VirtualHost 192.0.2.3:443>
881        # This server enables SRP and X.509 authentication.
882        GnuTLSEnable on
883        GnuTLSPriorities NORMAL:+SRP:+SRP-RSA:+SRP-DSS
884        DocumentRoot /www/site3.example.com/html
885        ServerName site3.example.com:443
886        GnuTLSCertificateFile conf/tls/site3.crt
887        GnuTLSKeyFile conf/tls/site3.key
888        GnuTLSSRPPasswdFile conf/tls/tpasswd.site3
889        GnuTLSSRPPasswdConfFile conf/tls/tpasswd.site3.conf
890</VirtualHost>
891```
892
893OCSP Stapling Example
894---------------------
895
896This is an example with a customized OCSP stapling configuration. What
897is a resonable cache timeout varies depending on how long your CA's
898OCSP responses are valid. Some CAs provide responses that are valid
899for multiple days, in that case timeout and fuzz time could be
900significantly larger.
901
902```apache
903# Load the module into Apache.
904LoadModule gnutls_module modules/mod_gnutls.so
905# A 64K cache is more than enough for one response
906GnuTLSOCSPCache shmcb:ocsp_cache(65536)
907
908Listen 192.0.2.1:443
909
910<VirtualHost _default_:443>
911        GnuTLSEnable           On
912        DocumentRoot           /www/site1.example.com/html
913        ServerName             site1.example.com:443
914        GnuTLSCertificateFile  conf/tls/site1_cert_chain.pem
915        GnuTLSKeyFile          conf/tls/site1_key.pem
916        GnuTLSOCSPStapling     On
917        # The cached OCSP response is kept for up to 4 hours,
918        # with updates scheduled every 3 to 3.5 hours.
919        GnuTLSOCSPCacheTimeout 21600
920        GnuTLSOCSPFuzzTime     3600
921</VirtualHost>
922```
923
924* * * * *
925
926Environment Variables
927=====================
928
929`mod_gnutls` exports the following environment variables to scripts.
930These are compatible with `mod_ssl`.
931
932`HTTPS`
933-------
934
935Can be `on` or `off`
936
937`SSL_VERSION_LIBRARY`
938---------------------
939
940The version of the GnuTLS library
941
942`SSL_VERSION_INTERFACE`
943-----------------------
944
945The version of this module
946
947`SSL_PROTOCOL`
948--------------
949
950The SSL or TLS protocol name (such as `TLS 1.0` etc.)
951
952`SSL_CIPHER`
953------------
954
955The SSL or TLS cipher suite name
956
957`SSL_COMPRESS_METHOD`
958---------------------
959
960The negotiated compression method (`NULL` or `DEFLATE`)
961
962`SSL_SRP_USER`
963--------------
964
965The SRP username used for authentication (only set when
966`GnuTLSSRPPasswdFile` and `GnuTLSSRPPasswdConfFile` are configured).
967
968`SSL_CIPHER_USEKEYSIZE` & `SSL_CIPHER_ALGKEYSIZE`
969-------------------------------------------------
970
971The number if bits used in the used cipher algorithm.
972
973This does not fully reflect the security level since the size of
974RSA or DHE key exchange parameters affect the security level too.
975
976`SSL_DH_PRIME_BITS`
977-------------------
978
979The number if bits in the modulus for the DH group, if DHE or static
980DH is used.
981
982This will not be set if DH is not used.
983
984`SSL_CIPHER_EXPORT`
985-------------------
986
987`True` or `False`. Whether the cipher suite negotiated is an export one.
988
989`SSL_SESSION_ID`
990----------------
991
992The session ID negotiated in this session. Can be the same during client
993reloads.
994
995`SSL_CLIENT_VERIFY`
996-------------------
997
998Verification status of the client's certificate, if any. May be
999`SUCCESS`, `FAILED` or `NONE`. See
1000[`GnuTLSClientVerify`](#gnutlsclientverify).
1001
1002`SSL_CLIENT_V_REMAIN`
1003---------------------
1004
1005The number of days until the client's certificate is expired.
1006
1007`SSL_CLIENT_V_START`
1008--------------------
1009
1010The activation time of client's certificate.
1011
1012`SSL_CLIENT_V_END`
1013------------------
1014
1015The expiration time of client's certificate.
1016
1017`SSL_CLIENT_S_DN`
1018-----------------
1019
1020The distinguished name of client's certificate in RFC2253 format.
1021
1022`SSL_CLIENT_I_DN`
1023-----------------
1024
1025The distinguished name of the issuer of the client's certificate in
1026RFC2253 format.
1027
1028`SSL_CLIENT_S_AN%`
1029------------------
1030
1031These will contain the alternative names of the client certificate (`%` is
1032a number starting from zero).
1033
1034The values will be prepended by `DNSNAME:`, `RFC822NAME:` or `URI:`
1035depending on the type.
1036
1037If it is not supported the value `UNSUPPORTED` will be set.
1038
1039`SSL_SERVER_M_SERIAL`
1040---------------------
1041
1042The serial number of the server's certificate.
1043
1044`SSL_SERVER_M_VERSION`
1045----------------------
1046
1047The version of the server's certificate.
1048
1049`SSL_SERVER_A_SIG`
1050------------------
1051
1052The algorithm used for the signature in server's certificate.
1053
1054`SSL_SERVER_A_KEY`
1055------------------
1056
1057The public key algorithm in server's certificate.
1058
1059`SSL_SERVER_CERT`
1060------------------
1061
1062The PEM-encoded (X.509) server certificate (see the
1063`GnuTLSExportCertificates` directive).
1064
1065`SSL_SERVER_CERT_TYPE`
1066----------------------
1067
1068The certificate type will be `X.509`.
1069
1070`SSL_CLIENT_CERT`
1071------------------
1072
1073PEM-encoded (X.509) client certificate, if any (see the
1074`GnuTLSExportCertificates` directive).
1075
1076`SSL_CLIENT_CERT_TYPE`
1077----------------------
1078
1079The certificate type will be `X.509`, if any.
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