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26 <div id="page-content">
27 <div id="preamble"><h1>Apache Module mod_ssl_ct</h1>
29 <p><span>Available Languages: </span><a href="../en/mod/mod_ssl_ct.html" title="English"> en </a></p>
31 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Implementation of Certificate Transparency (RFC 6962)
33 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
34 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>ssl_ct_module</td></tr>
35 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_ssl_ct.c</td></tr></table>
39 <p>This module provides an implementation of Certificate Transparency, in
40 conjunction with <code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code> and command-line tools from the
41 <a href="https://code.google.com/p/certificate-transparency/">certificate-transparency</a>
42 open source project. The goal of Certificate Transparency is to expose the
43 use of server certificates which are trusted by browsers but were mistakenly
44 or maliciously issued. More information about Certificate Transparency is
45 available at <a href="http://www.certificate-transparency.org/">
46 http://www.certificate-transparency.org/</a>. Key terminology used in
47 this documentation:</p>
50 <dt>Certificate log</dt>
51 <dd>A certificate log, referred to simply as <q>log</q> in this documentation,
52 is a network service to which server certificates have been submitted. A
53 user agent can confirm that the certificate of a server which it accesses
54 has been submitted to a log which it trusts, and that the log itself has
55 not been tampered with.</dd>
57 <dt>Signed Certificate Timestamp (SCT)</dt>
58 <dd>This is an acknowledgement from a log that it has accepted a valid
59 certificate. It is signed with the log's public key. One or more SCTs
60 is passed to clients during the handshake, either in the ServerHello
61 (TLS extension), certificate extension, or in a stapled OCSP response.</dd>
64 <p>This implementation for Apache httpd provides these features for TLS
65 servers and proxies:</p>
68 <li>Signed Certificate Timestamps (SCTs) can be obtained from logs
69 automatically and, in conjunction with any statically configured SCTs, sent
70 to aware clients in the ServerHello (during the handshake).</li>
71 <li>SCTs can be received by the proxy from origin servers in the ServerHello,
72 in a certificate extension, and/or within stapled OCSP responses; any SCTs
73 received can be partially validated on-line and optionally queued for off-line
75 <li>The proxy can be configured to disallow communication with an origin
76 server which does not provide an SCT which passes on-line validation.</li>
79 <p>Configuration information about logs can be defined statically in the web
80 server configuration or maintained in a SQLite3 database. In the latter case,
81 <code class="module"><a href="../mod/mod_ssl_ct.html">mod_ssl_ct</a></code> will reload the database periodically, so any
82 site-specific infrastructure for maintaining and propagating log configuration
83 information does not have to also restart httpd to make it take effect.</p>
85 <div class="note">This module is experimental for the following reasons:
87 <li>Insufficient test and review</li>
88 <li>Reliance on an unreleased version of OpenSSL (1.0.2, Beta 3 or later) for
90 <li>Incomplete <a href="#audit">off-line audit capability</a></li>
93 <p>Configuration mechanisms, format of data saved for off-line audit, and
94 other characteristics are subject to change based on further feedback and
98 <div id="quickview"><h3>Topics</h3>
100 <li><img alt="" src="../images/down.gif" /> <a href="#server">Server processing overview</a></li>
101 <li><img alt="" src="../images/down.gif" /> <a href="#proxy">Proxy processing overview</a></li>
102 <li><img alt="" src="../images/down.gif" /> <a href="#logconf">Log configuration</a></li>
103 <li><img alt="" src="../images/down.gif" /> <a href="#static">Storing SCTs in a form consumable by mod_ssl_ct</a></li>
104 <li><img alt="" src="../images/down.gif" /> <a href="#logging">Logging CT status in the access log</a></li>
105 <li><img alt="" src="../images/down.gif" /> <a href="#audit">Off-line audit for proxy</a></li>
106 </ul><h3 class="directives">Directives</h3>
108 <li><img alt="" src="../images/down.gif" /> <a href="#ctauditstorage">CTAuditStorage</a></li>
109 <li><img alt="" src="../images/down.gif" /> <a href="#ctlogclient">CTLogClient</a></li>
110 <li><img alt="" src="../images/down.gif" /> <a href="#ctlogconfigdb">CTLogConfigDB</a></li>
111 <li><img alt="" src="../images/down.gif" /> <a href="#ctmaxsctage">CTMaxSCTAge</a></li>
112 <li><img alt="" src="../images/down.gif" /> <a href="#ctproxyawareness">CTProxyAwareness</a></li>
113 <li><img alt="" src="../images/down.gif" /> <a href="#ctsctstorage">CTSCTStorage</a></li>
114 <li><img alt="" src="../images/down.gif" /> <a href="#ctserverhellosctlimit">CTServerHelloSCTLimit</a></li>
115 <li><img alt="" src="../images/down.gif" /> <a href="#ctstaticlogconfig">CTStaticLogConfig</a></li>
116 <li><img alt="" src="../images/down.gif" /> <a href="#ctstaticscts">CTStaticSCTs</a></li>
118 <h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&list_id=144532&product=Apache%20httpd-2&query_format=specific&order=changeddate%20DESC%2Cpriority%2Cbug_severity&component=mod_ssl_ct">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&component=mod_ssl_ct">Report a bug</a></li></ul><h3>See also</h3>
120 <li><a href="#comments_section">Comments</a></li></ul></div>
121 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
122 <div class="section">
123 <h2><a name="server" id="server">Server processing overview</a></h2>
126 <p>Servers need to send SCTs to their clients. SCTs in a certificate
127 extension or stapled OCSP response will be sent without any special program
128 logic. This module handles sending SCTs configured by the administrator or
129 received from configured logs.</p>
131 <p>The number of SCTs sent in the ServerHello (i.e., not including those in a
132 certificate extension or stapled OCSP response) can be limited by the
133 <code class="directive"><a href="#ctserverhellosctlimit">CTServerHelloSCTLimit</a></code>
136 <p>For each server certificate, a daemon process maintains an SCT list to be
137 sent in the ServerHello, created from statically configured SCTs as well as
138 those received from logs. Logs marked as untrusted or with a maximum valid
139 timestamp before the present time will be ignored. Periodically the daemon
140 will submit certificates to a log as necessary (due to changed log
141 configuration or age) and rebuild the concatenation of SCTs.</p>
143 <p>The SCT list for a server certificate will be sent to any client that
144 indicates awareness in the ClientHello when that particular server certificate
147 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
148 <div class="section">
149 <h2><a name="proxy" id="proxy">Proxy processing overview</a></h2>
152 <p>The proxy indicates Certificate Transparency awareness in the ClientHello
153 by including the <em>signed_certificate_timestamp</em> extension. It can
154 recognize SCTs received in the ServerHello, in an extension in the certificate
155 for an origin server, or in a stapled OCSP response.</p>
157 <p>On-line verification is attempted for each received SCT:</p>
160 <li>For any SCT, the timestamp can be checked to see if it is not yet valid
161 based on the current time as well as any configured valid time interval for
163 <li>For an SCT from a log for which a public key is configured, the server
164 signature will be checked.</li>
167 <p>If verification fails for at least one SCT and verification was not
168 successful for at least one SCT, the connection is aborted if
169 <code class="directive"><a href="#ctproxyawareness">CTProxyAwareness</a></code> is set to
170 <em>require</em>.</p>
172 <p>Additionally, the server certificate chain and SCTs are stored for off-line
173 verification if the <code class="directive"><a href="#ctauditstorage">CTAuditStorage</a></code>
174 directive is configured.</p>
176 <p>As an optimization, on-line verification and storing of data from the
177 server is only performed the first time a web server child process receives
178 the data. This saves some processing time as well as disk space. For typical
179 reverse proxy setups, very little processing overhead will be required.</p>
181 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
182 <div class="section">
183 <h2><a name="logconf" id="logconf">Log configuration</a></h2>
186 <p>Servers and proxies use different information about logs for their processing.
187 This <em>log configuration</em> can be set in two ways:</p>
190 <li>Create a log configuration database using <code class="program"><a href="../programs/ctlogconfig.html">ctlogconfig</a></code>,
191 and configure the path to that database using the <code class="directive"><a href="#ctlogconfig">
192 CTLogConfig</a></code> directive. This method of configuration supports
193 dynamic updates; <code class="module"><a href="../mod/mod_ssl_ct.html">mod_ssl_ct</a></code> will re-read the database at
194 intervals. Additionally, the off-line audit program <code>ctauditscts</code>
195 can use this configuration to find the URL of logs.</li>
197 <li>Configure information about logs statically using the <code class="directive"><a href="#ctstaticlogconfig">CTStaticLogConfig</a></code> directive. As with all other
198 directives, the server must be restarted in order to pick up changes to the
202 <p>The information that can be configured about a log using either mechanism is
207 <dd>The log id is the SHA-256 hash of the log's public key, and is part of
208 every SCT. This is a convenient way to identify a particular log when
209 configuring valid timestamp ranges or certain other information.</dd>
211 <dt>public key of the log</dt>
212 <dd>A proxy must have the public key of the log in order to check the
213 signature in SCTs it receives which were obtained from the log.
215 A server must have the public key of the log in order to submit certificates
218 <dt>general trust/distrust setting</dt>
219 <dd>This is a mechanism to distrust or restore trust in a particular log,
220 for whatever reason (including simply avoiding interaction with the
221 log in situations where it is off-line).</dd>
223 <dt>minimum and/or maximum valid timestamps</dt>
224 <dd>When configured, the proxy will check that timestamps from SCTs
225 are within the valid range.</dd>
228 <dd>The URL of the log (for its API) is required by a server in order to
229 submit server certificates to the log. The server will submit
230 each server certificate in order to obtain an SCT for each log with a
231 configured URL, except when the log is also marked as distrusted or the
232 current time is not within any configured valid timestamp range.
234 The log URL is also needed by off-line auditing of SCTs received by a
238 <p>Generally, only a small subset of this information is configured for a
239 particular log. Refer to the documentation for the <code class="directive"><a href="#ctstaticlogconfig">CTStaticLogConfig</a></code> directive and the
240 <code class="program"><a href="../programs/ctlogconfig.html">ctlogconfig</a></code> command for more specific information.</p>
242 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
243 <div class="section">
244 <h2><a name="static" id="static">Storing SCTs in a form consumable by mod_ssl_ct</a></h2>
247 <p><code class="module"><a href="../mod/mod_ssl_ct.html">mod_ssl_ct</a></code> allows you to configure SCTs statically
248 using the <code class="directive">CTStaticSCTs</code> directive. These must be
249 in binary form, ready to send to a client.</p>
251 <p>Sample code in the form of a Python script to build an SCT in the correct
252 format from data received from a log can be found in
253 <a href="https://github.com/tomrittervg/ct-tools">Tom Ritter's ct-tools
254 repository</a>. Refer to <code>write-sct.py</code></p>
255 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
256 <div class="section">
257 <h2><a name="logging" id="logging">Logging CT status in the access log</a></h2>
260 <p>Proxy and server modes set the <code>SSL_CT_PROXY_STATUS</code> and
261 <code>SSL_CT_CLIENT_STATUS</code> variables, respectively, to indicate
262 if the corresponding peer is CT-aware.</p>
264 <p>Proxy mode sets the <code>SSL_CT_PROXY_SCT_SOURCES</code> variable to
265 indicate whether and where SCTs were obtained (ServerHello, certificate
266 extension, etc.).</p>
268 <p>These variables can be logged with the <code>%{<em>varname</em>}e</code>
269 format of <code class="module"><a href="../mod/mod_log_config.html">mod_log_config</a></code>.</p>
270 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
271 <div class="section">
272 <h2><a name="audit" id="audit">Off-line audit for proxy</a></h2>
275 <p>Experimental support for this is implemented in the <code>ctauditscts</code>
276 command, which itself relies on the <code>verify_single_proof.py</code> tool in the
277 <em>certificate-transparency</em> open source project. <code>ctauditscts</code>
278 can parse data for off-line audit (enabled with the <code class="directive"><a href="#ctauditstorage">
279 CTAuditStorage</a></code> directive) and invoke <code>verify_single_proof.py</code>.
282 <p>Here are rough notes for using <code>ctauditscts</code>:</p>
285 <li>Create a <em>virtualenv</em> using the <code>requirements.txt</code> file
286 from the <em>certificate-transparency</em> project and run the following steps
287 with that <em>virtualenv</em> activated.</li>
288 <li>Set <code>PYTHONPATH</code> to include the <code>python</code>
289 directory within the <em>certificate-transparency</em> tools.</li>
290 <li>Set <code>PATH</code> to include the <code>python/ct/client/tools</code>
292 <li>Run <code>ctauditscts</code>, passing the value of the
293 <code class="directive">CTAuditStorage</code> directive and, optionally, the path to
294 the log configuration database. The latter will be used to look up log URLs
298 <p>The data saved for audit can also be used by other programs; refer to the
299 <code>ctauditscts</code> source code for details on processing the data.</p>
301 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
302 <div class="directive-section"><h2><a name="CTAuditStorage" id="CTAuditStorage">CTAuditStorage</a> <a name="ctauditstorage" id="ctauditstorage">Directive</a></h2>
303 <table class="directive">
304 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Existing directory where data for off-line audit will be stored</td></tr>
305 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CTAuditStorage <em>directory</em></code></td></tr>
306 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
307 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
308 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
309 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_ssl_ct</td></tr>
311 <p>The <code class="directive">CTAuditStorage</code> directive sets the name of a
312 directory where data will be stored for off-line audit. If <em>directory</em>
313 is not absolute then it is assumed to be relative to <code class="directive"><a href="../mod/core.html#defaultruntimedir">
314 DefaultRuntimeDir</a></code>.</p>
316 <p>If this directive is not specified, data will not be stored for off-line
319 <p>The directory will contain files named <code><em>PID</em>.tmp</code> for
320 active child processes and files named <code><em>PID</em>.out</code> for exited
321 child processes. These <code>.out</code> files are ready for off-line audit.
322 The experimental command <code>ctauditscts</code> (in the httpd source tree, not
323 currently installed) interfaces with <em>certificate-transparency</em> tools to
324 perform the audit.</p>
327 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
328 <div class="directive-section"><h2><a name="CTLogClient" id="CTLogClient">CTLogClient</a> <a name="ctlogclient" id="ctlogclient">Directive</a></h2>
329 <table class="directive">
330 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location of certificate-transparency log client tool</td></tr>
331 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CTLogClient <em>executable</em></code></td></tr>
332 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
333 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
334 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
335 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_ssl_ct</td></tr>
337 <p><em>executable</em> is the full path to the log client tool, which is
338 normally file <code>cpp/client/ct</code> (or <code>ct.exe</code>) within the
340 <a href="https://code.google.com/p/certificate-transparency/">
341 certificate-transparency</a> open source project.</p>
343 <p>An alternative implementation could be used to retrieve SCTs for a
344 server certificate as long as the command-line interface is equivalent.</p>
346 <p>If this directive is not configured, server certificates cannot be
347 submitted to logs in order to obtain SCTs; thus, only admin-managed
348 SCTs or SCTs in certificate extensions will be provided to clients.</p>
351 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
352 <div class="directive-section"><h2><a name="CTLogConfigDB" id="CTLogConfigDB">CTLogConfigDB</a> <a name="ctlogconfigdb" id="ctlogconfigdb">Directive</a></h2>
353 <table class="directive">
354 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Log configuration database supporting dynamic updates</td></tr>
355 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CTLogConfigDB <em>filename</em></code></td></tr>
356 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
357 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
358 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
359 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_ssl_ct</td></tr>
361 <p>The <code class="directive">CTLogConfigDB</code> directive sets the name of a database
362 containing configuration about known logs. If <em>filename</em> is not absolute
363 then it is assumed to be relative to
364 <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</p>
366 <p>Refer to the documentation for the <code class="program"><a href="../programs/ctlogconfig.html">ctlogconfig</a></code> program,
367 which manages the database.</p>
370 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
371 <div class="directive-section"><h2><a name="CTMaxSCTAge" id="CTMaxSCTAge">CTMaxSCTAge</a> <a name="ctmaxsctage" id="ctmaxsctage">Directive</a></h2>
372 <table class="directive">
373 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum age of SCT obtained from a log, before it will be
375 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CTMaxSCTAge <em>num-seconds</em></code></td></tr>
376 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>1 day</code></td></tr>
377 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
378 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
379 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_ssl_ct</td></tr>
381 <p>Server certificates with SCTs which are older than this maximum age will
382 be resubmitted to configured logs. Generally the log will return the same SCT
383 as before, but that is subject to log operation. SCTs will be refreshed as
384 necessary during normal server operation, with new SCTs returned to clients
385 as they become available.</p>
388 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
389 <div class="directive-section"><h2><a name="CTProxyAwareness" id="CTProxyAwareness">CTProxyAwareness</a> <a name="ctproxyawareness" id="ctproxyawareness">Directive</a></h2>
390 <table class="directive">
391 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Level of CT awareness and enforcement for a proxy
393 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CTProxyAwareness <em>oblivious|aware|require</em></code></td></tr>
394 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>aware</code></td></tr>
395 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
396 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
397 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_ssl_ct</td></tr>
399 <p>This directive controls awareness and checks for valid SCTs for a
400 proxy. Several options are available:</p>
404 <dd>The proxy will neither ask for nor examine SCTs. Certificate
405 Transparency processing for the proxy is completely disabled.</dd>
408 <dd>The proxy will perform all appropriate Certificate Transparency
409 processing, such as asking for and examining SCTs. However, the
410 proxy will not disallow communication if the origin server does
411 not provide any valid SCTs.</dd>
414 <dd>The proxy will abort communication with the origin server if it
415 does not provide at least one SCT which passes on-line validation.</dd>
420 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
421 <div class="directive-section"><h2><a name="CTSCTStorage" id="CTSCTStorage">CTSCTStorage</a> <a name="ctsctstorage" id="ctsctstorage">Directive</a></h2>
422 <table class="directive">
423 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Existing directory where SCTs are managed</td></tr>
424 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CTSCTStorage <em>directory</em></code></td></tr>
425 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
426 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
427 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
428 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_ssl_ct</td></tr>
430 <p>The <code class="directive">CTSCTStorage</code> directive sets the name of a
431 directory where SCTs and SCT lists will be stored. If <em>directory</em>
432 is not absolute then it is assumed to be relative to <code class="directive"><a href="../mod/core.html#defaultruntimedir">
433 DefaultRuntimeDir</a></code>.</p>
435 <p>A subdirectory for each server certificate contains information relative
436 to that certificate; the name of the subdirectory is the SHA-256 hash of the
439 <p>The certificate-specific directory contains SCTs retrieved from configured
440 logs, SCT lists prepared from statically configured SCTs and retrieved SCTs,
441 and other information used for managing SCTs.</p>
444 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
445 <div class="directive-section"><h2><a name="CTServerHelloSCTLimit" id="CTServerHelloSCTLimit">CTServerHelloSCTLimit</a> <a name="ctserverhellosctlimit" id="ctserverhellosctlimit">Directive</a></h2>
446 <table class="directive">
447 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limit on number of SCTs that can be returned in
448 ServerHello</td></tr>
449 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CTServerHelloSCTLimit <em>limit</em></code></td></tr>
450 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>100</code></td></tr>
451 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
452 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
453 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_ssl_ct</td></tr>
455 <p>This directive can be used to limit the number of SCTs which can be
456 returned by a TLS server in ServerHello, in case the number of configured
457 logs and statically-defined SCTs is relatively high.</p>
459 <p>Typically only a few SCTs would be available, so this directive is only
460 needed in special circumstances.</p>
462 <p>The directive does not take into account SCTs which may be provided in
463 certificate extensions or in stapled OCSP responses.</p>
466 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
467 <div class="directive-section"><h2><a name="CTStaticLogConfig" id="CTStaticLogConfig">CTStaticLogConfig</a> <a name="ctstaticlogconfig" id="ctstaticlogconfig">Directive</a></h2>
468 <table class="directive">
469 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Static configuration of information about a log</td></tr>
470 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CTStaticLogConfig <em>log-id|-</em> <em>public-key-file|-</em>
471 <em>1|0|-</em> <em>min-timestamp|-</em> <em>max-timestamp|-</em>
472 <em>log-URL|-</em></code></td></tr>
473 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
474 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
475 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
476 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_ssl_ct</td></tr>
478 <p>This directive is used to configure information about a particular log.
479 This directive is appropriate when configuration information changes rarely.
480 If dynamic configuration updates must be supported, refer to the
481 <code class="directive"><a href="#ctlogconfigdb">CTLogConfigDB</a></code> directive.</p>
483 <p>Each of the six fields must be specified, but usually only a small
484 amount of information must be configured for each log; use <em>-</em> when no
485 information is available for the field. For example, in support of a
486 server-only configuration (i.e., no proxy), the administrator might
487 configure only the log URL to be used when submitting server certificates
488 and obtaining a Signed Certificate Timestamp.</p>
490 <p>The fields are defined as follows:</p>
493 <dt><em>log-id</em></dt>
494 <dd>This is the id of the log, which is the SHA-256 hash of the log's
495 public key, provided in hexadecimal format. This string is 64 characters
498 This field should be omitted when <em>public-key-file</em> is provided.</dd>
500 <dt><em>public-key-file</em></dt>
501 <dd>This is the name of a file containing the PEM encoding of the log's
502 public key. If the name is not absolute, then it is assumed to be relative
503 to <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</dd>
505 <dt><em>trust/distrust</em></dt>
506 <dd>Set this field to <em>1</em> to distrust this log, or to otherwise avoid
507 using it for server certificate submission. Set this to <em>-</em> or
508 <em>0</em> (the default) to treat the log normally.</dd>
510 <dt><em>min-timestamp</em> and <em>max-timestamp</em></dt>
511 <dd>A timestamp is a time as expressed in the number of milliseconds since the
512 epoch, ignoring leap seconds. This is the form of time used in Signed Certificate
513 Timestamps. This must be provided as a decimal number.
515 Specify <strong><code>-</code></strong> for one of the timestamps if it is unknown.
516 For example, when configuring the minimum valid timestamp for a log which remains
517 valid, specify <strong><code>-</code></strong> for <em>max-timestamp</em>.
519 SCTs received from this log by the proxy are invalid if the timestamp
520 is older than <em>min-timestamp</em> or newer than <em>max-timestamp</em>.</dd>
522 <dt><em>log-URL</em></dt>
523 <dd>This is the URL of the log, for use in submitting server certificates
524 and in turn obtaining an SCT to be sent to clients.</dd>
529 <li><a href="#logconf">Log configuration</a> contains more general information
530 about the fields which can be configured with this directive.</li>
533 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
534 <div class="directive-section"><h2><a name="CTStaticSCTs" id="CTStaticSCTs">CTStaticSCTs</a> <a name="ctstaticscts" id="ctstaticscts">Directive</a></h2>
535 <table class="directive">
536 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Static configuration of one or more SCTs for a server certificate
538 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CTStaticSCTs <em>certificate-pem-file</em> <em>sct-directory</em></code></td></tr>
539 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
540 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
541 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
542 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_ssl_ct</td></tr>
544 <p>This directive is used to statically define one or more SCTs corresponding
545 to a server certificate. This mechanism can be used instead of or in
546 addition to dynamically obtaining SCTs from configured logs. Any changes to
547 the set of SCTs for a particular server certificate will be adopted dynamically
548 without the need to restart the server.</p>
550 <p><em>certificate-pem-file</em> refers to the server certificate in PEM
551 format. If the name is not absolute, then it is assumed to be relative to
552 <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</p>
554 <p><em>sct-directory</em> should contain one or more files with extension
555 <code>.sct</code>, representing one or more SCTs corresponding to the
556 server certificate. If <em>sct-directory</em> is not absolute, then it is
557 assumed to be relative to <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</p>
559 <p>If <em>sct-directory</em> is empty, no error will be raised.</p>
561 <p>This directive could be used to identify directories of SCTs maintained by
562 other infrastructure, provided that they are saved in binary format with
563 file extension <em>.sct</em></p>
567 <div class="bottomlang">
568 <p><span>Available Languages: </span><a href="../en/mod/mod_ssl_ct.html" title="English"> en </a></p>
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