docs/manual/mod/mod_md.xml

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<modulesynopsis metafile="mod_md.xml.meta">
    
    <name>mod_md</name>
    <description>Managing domains across virtual hosts, certificate provisioning 
        via the ACME protocol
    </description>
    <status>Extension</status>
    <sourcefile>mod_md.c</sourcefile>
    <identifier>md_module</identifier>
    <compatibility>Available in version 2.4.30 and later</compatibility>
    <summary>
        <p>
        This module manages common properties of domains for one or more virtual hosts. 
        Specifically it can use the ACME protocol
        (<a href="https://datatracker.ietf.org/doc/draft-ietf-acme-acme/">RFC Draft</a>) 
        to automate certificate provisioning. These will be configured for managed domains and
        their virtual hosts automatically. This includes renewal of certificates before they
        expire. The most famous Certificate Authority currently implementing the ACME protocol
        is <a href="https://letsencrypt.org/">Let's Encrypt</a>.</p>
        
        <note type="warning"><title>Warning</title>
            <p>This module is experimental. Its behaviors, directives, and 
                defaults are subject to more change from release to 
                release relative to other standard modules. Users are encouraged to 
                consult the "CHANGES" file for potential updates.</p>
        </note>

        <p>Simple configuration example:</p>
        
        <note><title>TLS in a VirtualHost context</title>
        <highlight language="config">
MDomain example.org

&lt;VirtualHost *:443&gt;
    ServerName example.org
    DocumentRoot htdocs/a

    SSLEngine on
    # no certificates specification
&lt;/VirtualHost&gt;
        </highlight>
        <p>
            This setup will, on server start, contact
            <a href="https://letsencrypt.org/">Let's Encrypt</a>
            to request a certificate for the domain. If Let's Encrypt can verify the ownership
            of the domain, the module will retrieve the certificate and its chain, store it
            in the local file system (see <directive module="mod_md">MDStoreDir</directive>)
            and provide it, on next restart, to <module>mod_ssl</module>.
        </p><p>
            This happens while the server is already running. All other hosts will continue
            to work as before. While a certificate is not available, requests for the managed
            domain will be answered with a '503 Service Unavailable'. 
        </p>
        </note>

        <note><title>Prerequisites</title>
        <p>
            This module requires <module>mod_watchdog</module> to be loaded as well.
        </p><p>
            Certificate signup and renewal with Let's Encrypt requires your server to be
            reachable on port 80 (http:) from the outside. The alternative method over
            port 443 (https:) is currently disabled for security reasons (status from
            2018-01-14).
        </p><p>
            The module will select from the methods offered by Let's Encrypt. If LE decides
            at one point in the future, to re-enable it again, <module>mod_md</module> will
            use it when suitable.
        </p><p>
            But for now, only the port 80 variant is available (termed "http-01"). Only
            when LE can reach your server on port 80 will <module>mod_md</module> work for
            you. For now, at least.
        </p><p>
            If you do not want to offer any sites on port 80 any more, you may leave it open
            and redirect all requests to your https: sites instead. Use the
            <directive module="mod_md">MDRequireHttps</directive> described below to do
            that in a convenient fashion. This will continue to answer http: challenges
            from Let's Encrypt. 
        </p>
        </note>
    </summary>
    
    <directivesynopsis>
        <name>MDomain</name>
        <description>Define list of domain names that belong to one group.</description>
        <syntax>MDomain <var>dns-name</var> [ <var>other-dns-name</var>... ] [auto|manual]</syntax>
        <contextlist>
            <context>server config</context>
        </contextlist>
        
        <usage>
            <p>
                All the names in the list are managed as one Managed Domain (MD). 
                <module>mod_md</module> will request one single certificate that is valid for all these names. This
                directive uses the global settings (see other MD directives below). If you
                need specific settings for one MD, use
                the <directive module="mod_md" type="section">MDomainSet</directive>.
            </p><p>
                There are 2 additional settings that are necessary for a Managed Domain:
                <directive module="core">ServerAdmin</directive>
                and <directive module="mod_md">MDCertificateAgreement</directive>.
                The mail address of <directive module="core">ServerAdmin</directive>
                is used to register at the CA (Let's Encrypt by default).
                The CA may use it to notify you about
                changes in its service or status of your certificates.
            </p><p>
                The second setting, <directive module="mod_md">MDCertificateAgreement</directive>, 
                is the URL of the Terms of Service of the CA. When you configure the URL, 
                you confirm that you have read and agree to the terms described in the linked 
                document. Before you do that, the CA will  not hand out certificates to you.
            </p>
            <example><title>Example</title>
                <highlight language="config">
ServerAdmin mailto:admin@example.org
MDCertificateAgreement https://letsencrypt.org/documents/LE-SA-v1.2-November-15-2017.pdf
MDomain example.org www.example.org

&lt;VirtualHost *:443&gt;
    ServerName example.org
    DocumentRoot htdocs/root

    SSLEngine on
&lt;/VirtualHost&gt;

&lt;VirtualHost *:443&gt;
    ServerName www.example.org
    DocumentRoot htdocs/www

    SSLEngine on
&lt;/VirtualHost&gt;
                </highlight>
            </example>
            <p>
                There are two special names that you may use in this directive: 'manual'
                and 'auto'. This determines if a Managed Domain shall have exactly the 
                name list as is configured ('manual') or offer more convenience. With 'auto'
                all names of a virtual host are added to a MD. Conventiently, 'auto' is also
                the default.
            </p>
            <example><title>Example</title>
                <highlight language="config">
MDomain example.org

&lt;VirtualHost *:443&gt;
    ServerName example.org
    ServerAlias www.example.org
    DocumentRoot htdocs/root

    SSLEngine on
&lt;/VirtualHost&gt;

MDomain example2.org auto

&lt;VirtualHost *:443&gt;
    ServerName example2.org
    ServerAlias www.example2.org
    ...
&lt;/VirtualHost&gt;
                </highlight>
            </example>
            <p>
                In this example, the domain 'www.example.org' is automatically added to
                the MD 'example.org'. Similarly for 'example2.org' where 'auto' is configured
                explicitly. Whenever you add more ServerAlias names to this
                virtual host, they will be added as well to the Managed Domain.
            </p><p>
                If you prefer to explicitly declare all the domain names, use 'manual' mode. 
                An error will be logged if the names do not match with the expected ones.
            </p>
        </usage>
    </directivesynopsis>

    <directivesynopsis type="section" idtype="section">
        <name>MDomainSet</name>
        <description>Container for directives applied to the same managed domains.</description>
        <syntax>&lt;MDomainSet <var>dns-name</var> [ <var>other-dns-name</var>... ]&gt;...&lt;/MDomainSet&gt;</syntax>
        <contextlist>
            <context>server config</context>
        </contextlist>
        
        <usage>
            <p>
                This directive allows you to define a Managed Domain (MD) with specific
                settings, different from the global MD* ones. For example, you can have
                such an MD use another CA then Let's Encrypt, have its unique renewal duration
                etc.
            </p>
            <example><title>Example</title>
                <highlight language="config">
&lt;MDomainSet sandbox.example.org&gt;
    MDCertificateAuthority   https://someotherca.com/ACME
    MDCertificateAgreement   https://someotherca.com/terms/v_1.02.pdf
&lt;/MDomainSet&gt;
                </highlight>
            </example>
        <p>This is a specialized version of <directive module="mod_md">MDomain</directive>,
        it should be used only when a fine grained configuration is required.
        <directive module="mod_md">MDomain</directive> is the suggested choice
        for the general use case.</p>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDCertificateAgreement</name>
        <description>The URL of the Terms-of-Service document, that the CA server requires you to accept.</description>
        <syntax>MDCertificateAgreement <var>url-of-terms-of-service</var></syntax>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>When you use <module>mod_md</module> to obtain a certificate, you become a customer of the CA (e.g. Let's Encrypt). That means you need to read and agree to their Terms of Service, 
            so that you understand what they offer and what they might exclude or require from you. 
            <module>mod_md</module> cannot, by itself, agree to such a thing. 
            </p>
            <p>In case of Let's Encrypt, their current <a href="https://letsencrypt.org/documents/LE-SA-v1.2-November-15-2017.pdf">Terms of Service are here</a>. 
            Those terms might (and probably will) change over time. So, the certificate renewal might require you to update this agreement URL.</p>
            <example><title>Example</title>
                <highlight language="config">
MDCertificateAgreement https://letsencrypt.org/documents/LE-SA-v1.2-November-15-2017.pdf
MDomain example.org www.example.org mail.example.org
                </highlight>
            </example>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDCertificateAuthority</name>
        <description>The URL of the ACME Certificate Authority service.</description>
        <syntax>MDCertificateAuthority <var>url</var></syntax>
        <default>MDCertificateAuthority https://acme-v01.api.letsencrypt.org/directory</default>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>
                The URL where the CA offers its service.
            </p><p>
                Let's Encrypt offers, right now, two such URLs. One for the real certificates and
                one for testing (their staging area, at https://acme-staging.api.letsencrypt.org/directory).
                In order to have <module>mod_md</module> use this testing service, configure your
                server like this: 
            </p>
            <example><title>LE Staging Setup</title>
                <highlight language="config">
MDCertificateAuthority https://acme-staging.api.letsencrypt.org/directory
MDCertificateAgreement https://letsencrypt.org/documents/LE-SA-v1.2-November-15-2017.pdf
                </highlight>
            </example>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDCertificateProtocol</name>
        <description>The protocol to use with the Certificate Authority.</description>
        <syntax>MDCertificateProtocol <var>protocol</var></syntax>
        <default>MDCertificateProtocol ACME</default>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>Specifies the protocol to use. Currently, only <code>ACME</code> is supported.</p>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDDriveMode</name>
        <description>Control when it is allowed to obtain/renew certificates.</description>
        <syntax>MDDriveMode always|auto|manual</syntax>
        <default>MDDriveMode auto</default>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>In 'auto' mode, <module>mod_md</module> will <em>drive</em> a Managed Domain's
            properties (e.g. certificate management) whenever necessary. When a MD is not used
            in any virtual host, the module will do nothing. When a certificate is missing, it
            will try to get one. When a certificate expires soon (see 
            <directive module="mod_md">MDRenewWindow</directive>), it will
            renew it.
            </p><p>
            In 'manual' mode, it is your duty to do all this. The module will provide the existing
            certificate to <module>mod_ssl</module>, if available. But it will not contact the CA for signup/renewal.
            This can be useful in clustered setups where you want just one node to perform
            the driving.
            </p><p>
            The third mode 'always' is like 'auto', with the difference that
            <module>mod_md</module> will not check if the MD is actually used. 
            </p>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDHttpProxy</name>
        <description>Define a proxy for outgoing connections.</description>
        <syntax>MDHttpProxy <var>url</var></syntax>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>Use a http proxy to connect to the MDCertificateAuthority. Define this
            if your webserver can only reach the internet with a forward proxy.
            </p>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDMember</name>
        <description>Additional hostname for the managed domain.</description>
        <syntax>MDMember <var>hostname</var></syntax>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>
            Instead of listing all dns names on the same line, you may use
            <directive>MDMember</directive> to add such names
            to a managed domain.
            </p>
            <example><title>Example</title>
                <highlight language="config">
&lt;MDomainSet example.org&gt;
    MDMember www.example.org
    MDMember mail.example.org
&lt;/MDomainSet example.org&gt;
                </highlight>
            </example>
            <p>
               If you use it in the global context, outside a specific MD, you can only
               specify one value, 'auto' or 'manual' as the default for all other MDs. See
               <directive module="mod_md">MDomain</directive> for a
               description of these special values.
            </p>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDMembers</name>
        <description>Control if the alias domain names are automatically added.</description>
        <syntax>MDMembers auto|manual</syntax>
        <default>MDMembers auto</default>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>Defines if the <directive module="core">ServerName</directive> and
               <directive module="core">ServerAlias</directive> values of a VirtualHost
               are automatically added to the members of a Managed Domain or not.
            </p>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDMustStaple</name>
        <description>Control if new certificates carry the OCSP Must Staple flag.</description>
        <syntax>MDMustStaple on|off</syntax>
        <default>MDMustStaple off</default>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>Defines if newly requested certificate should have the OCSP Must Staple flag 
            set or not. If a certificate has this flag, the server is required to send a 
            OCSP stapling response to every client. This only works if you configure 
            <module>mod_ssl</module> to generate this (see <directive module="mod_ssl">SSLUseStapling</directive>
            and friends).
            </p>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDNotifyCmd</name>
        <description>Run a program when Managed Domain are ready.</description>
        <syntax>MDNotifyCmd <var>path</var> [ <var>args</var> ]</syntax>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>The configured executable is run when Managed Domains have signed up or
            renewed their certificates. It is given the names of the processed MDs as
            additional arguments (after the parameters specified here). It should 
            return status code 0 to indicate that it has run successfully.
            </p>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDPortMap</name>
        <description>Map external to internal ports for domain ownership verification.</description>
        <syntax>MDPortMap <var>map1</var> [ <var>map2</var> ]</syntax>
        <default>MDPortMap 80:80 443:443</default>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>
                The ACME protocol provides two methods to verify domain ownership: one that uses
                port 80 and one for port 443. If your server is not reachable by at least one
                of the two, ACME will not work for you.
            </p><p>
                <module>mod_md</module> will look at your server configuration and try to figure
                out which of those are available. Then it can select the proper ACME challenge
                to create a certificate for your site.
            </p><p>
                However if you have some fancy port forwarding in place, your server may be
                reachable from the Internet on port 443, but the local port that httpd uses is
                another one. Your server might only listen on ports 5001 and 5002, but be reached
                on ports 443 and 80. How should <module>mod_md</module> figure that one out?
            </p><p>
                With <directive>MDPortMap</directive> you can tell it which 'Internet port'
                corresponds to which local port.
            </p>
            <example><title>Example</title>
                <highlight language="config">
MDPortMap 80:- 443:5002
                </highlight>
            </example>
            <p>
                This example says that the server is not reachable on port 80 from the outside, but
                local port 5002 is the one responding to https: requests.
            </p>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDPrivateKeys</name>
        <description>Set type and size of the private keys generated.</description>
        <syntax>MDPrivateKeys <var>type</var> [ <var>params</var>... ]</syntax>
        <default>MDPrivateKeys RSA 2048</default>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>
                Defines what kind of private keys are generated for a managed domain and with
                what parameters. The only supported type right now is 'RSA' and the only parameter
                it takes is the number of bits used for the key.
            </p><p>
                The current (2017) recommendation is at least 2048 bits and a smaller number is
                not accepted here. Higher numbers offer longer security, but are computationally more 
                expensive, e.g. increase the load on your server. That might or might not be an
                issue for you.
            </p><p>
                Other key types will be defined in the future.
            </p>
            <example><title>Example</title>
                <highlight language="config">
MDPrivateKeys RSA 3072
                </highlight>
            </example>
            <p>
                Please note that this setting only has an effect on new keys. Any existing
                private key you have remains unaffected. Also, this only affects private keys
                generated for certificates. ACME account keys are unaffected by this.
            </p>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDRenewWindow</name>
        <description>Control when a certificate will be renewed.</description>
        <syntax>MDRenewWindow <var>duration</var></syntax>
        <default>MDRenewWindow 33%</default>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>
            If the validity of the certificate falls below duration, <module>mod_md</module>
            will get a new signed certificate.
            </p><p>
            Normally, certificates are valid for around 90 days and <module>mod_md</module> will renew 
            them the earliest 33% of their complete lifetime before they expire (so for 
            90 days validity, 30 days before it expires). If you think this is not what 
            you need, you can specify either the exact time, as in:
            </p>
            <example><title>Example</title>
                <highlight language="config">
# 21 days before expiry
MDRenewWindow 21d 
# 30 seconds (might be close)
MDRenewWindow 30s
# 10% of the cert lifetime
MDRenewWindow 10%
                </highlight>
            </example>
            <p>When in auto drive mode, the module will check every 12 hours at least 
            what the status of the managed domains is and if it needs to do something. 
            On errors, for example when the CA is unreachable, it will initially retry 
            after some seconds. Should that continue to fail, it will back off to a 
            maximum interval of hourly checks.
            </p>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDRequireHttps</name>
        <description>Redirects http: traffic to https: for Managed Domains.</description>
        <syntax>MDRequireHttps off|temporary|permanent</syntax>
        <default>MDRequireHttps off</default>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>This is a convenience directive to ease http: to https: migration of 
            your Managed Domains. With:
            </p>
            <example><title>Example</title>
                <highlight language="config">
MDRequireHttps temporary                
                </highlight>
            </example>
            <p>you announce that you want all traffic via http: URLs to be redirected 
            to the https: ones, for now. This is safe and you can remove this again at
            any time.
            </p><p>
                <strong>The following has consequences: </strong>if you want client to <strong>no longer</strong> use the
             http: URLs, configure:
            </p>
            <example><title>Permanent (for at least half a year!)</title>
                <highlight language="config">
MDRequireHttps permanent                
                </highlight>
            </example>
            <p>This does two things:
            </p>
            <ol>
                <li>All request to the <code>http:</code> resources are redirected to the
                    same url with the <code>https:</code> scheme using the <code>301</code>
                status code. This tells clients that this is intended to be forever and
                the should update any links they have accordingly.
                </li>
                <li>All answers to <code>https:</code> requests will carry the header
                    <code>Strict-Transport-Security</code> with a life time of half a year.
                    This tells the browser that it <strong>never</strong> (for half a year) shall use <code>http:</code>
                    when talking to this domain name. Browsers will, after having seen this, refuse
                    to contact your unencrypted site. This prevents malicious middleware to
                    downgrade connections and listen/manipulate the traffic. Which is good. But
                    you cannot simply take it back again.
                </li>
            </ol>
            <p>You can achieve the same with <module>mod_alias</module> and some
            <directive module="mod_alias">Redirect</directive> configuration,
            basically. If you do it yourself, please make sure to exclude the paths 
            /.well-known/* from your redirection, otherwise <module>mod_md</module> 
            might have trouble signing on new certificates.
            </p>
            <p>If you set this globally, it applies to all managed domains. If you want 
            it for a specific domain only, use:
            </p>
            <example><title>Example</title>
                <highlight language="config">
&lt;MDomainSet xxx.yyy&gt;
  MDRequireHttps temporary
&lt;/MDomainSet&gt;
                </highlight>
            </example>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDStoreDir</name>
        <description>Path on the local file system to store the Managed Domains data.</description>
        <syntax>MDStoreDir path</syntax>
        <default>MDStoreDir md</default>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>
                Defines where on the local file system the Managed Domain data is stored. This is
                an absolute path or interpreted relative to the server root. The default will create
                a directory 'md' in your server root.
            </p><p>
                If you move this and have already data, be sure to move/copy the data first to
                the new location, reconfigure and then restart the server. If you reconfigure
                and restart first, the server will try to get new certificates that it thinks
                are missing.
            </p>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDCAChallenges</name>
        <description>Type of ACME challenge used to prove domain ownership.</description>
        <syntax>MDCAChallenges <var>name</var> [ <var>name</var> ... ]</syntax>
        <default>MDCAChallenges tls-sni-01 http-01</default>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>
                Sets challenge types and their execution order when proving domain ownership.
                The names are protocol specific.
                The current ACME protocol version implemented by Let's Encrypt defines two challenge
                types that are supported by <module>mod_md</module>. By default, it will try
                the one on port 443 when available.
            </p>
        </usage>
    </directivesynopsis>

    <directivesynopsis>
        <name>MDBaseServer</name>
        <description>Control if base server may be managed or only virtual hosts.</description>
        <syntax>MDBaseServer on|off</syntax>
        <default>MDBaseServer off</default>
        <contextlist>
            <context>server config</context>
        </contextlist>
        <usage>
            <p>
            Controls if the base server, the one outside all VirtualHosts should be managed by 
            <module>mod_md</module> or not. Default is to not do this, for the very reason that 
            it may have confusing side-effects. It is recommended that you have virtual hosts 
            for all managed domains and do not rely on the global, fallback server configuration.
            </p>
        </usage>
    </directivesynopsis>


</modulesynopsis>