docs/manual/mod/mod_access.xml

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<modulesynopsis metafile="mod_access.xml.meta" upgrade="mod_access_compat">

<name>mod_access</name> 
<description>Provides access control based on client hostname, IP
address, or other characteristics of the client request.</description>
<status>Base</status>
<sourcefile>mod_access.c</sourcefile>
<identifier>access_module</identifier>
<compatibility>Available only in versions prior to 2.1</compatibility>

<summary>
    <p>The directives provided by <module>mod_access</module> are used
    in <directive module="core" type="section">Directory</directive>,
    <directive module="core" type="section">Files</directive>, and
    <directive module="core" type="section">Location</directive> sections
    as well as <code><a href="core.html#accessfilename">.htaccess</a></code>
    files to control access to particular parts of the server. Access
    can be controlled based on the client hostname, IP address, or
    other characteristics of the client request, as captured in <a
    href="../env.html">environment variables</a>. The <directive
    module="mod_access">Allow</directive> and <directive
    module="mod_access">Deny</directive> directives are used to
    specify which clients are or are not allowed access to the server,
    while the <directive module="mod_access">Order</directive>
    directive sets the default access state, and configures how the
    <directive module="mod_access">Allow</directive> and <directive
    module="mod_access">Deny</directive> directives interact with each
    other.</p>

    <p>Both host-based access restrictions and password-based
    authentication may be implemented simultaneously. In that case,
    the <directive module="core">Satisfy</directive> directive is used
    to determine how the two sets of restrictions interact.</p>

    <p>In general, access restriction directives apply to all
    access methods (<code>GET</code>, <code>PUT</code>,
    <code>POST</code>, etc). This is the desired behavior in most
    cases. However, it is possible to restrict some methods, while
    leaving other methods unrestricted, by enclosing the directives
    in a <directive module="core" type="section">Limit</directive> section.</p>
</summary>

<seealso><directive module="core">Satisfy</directive></seealso>
<seealso><directive module="core">Require</directive></seealso>

<directivesynopsis>
<name>Allow</name>

<description>Controls which hosts can access an area of the
server</description>
<syntax> Allow from
    all|<var>host</var>|env=<var>env-variable</var>
    [<var>host</var>|env=<var>env-variable</var>] ...</syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>Limit</override>

<usage>

    <p>The <directive>Allow</directive> directive affects which hosts can
    access an area of the server. Access can be controlled by
    hostname, IP address, IP address range, or by other
    characteristics of the client request captured in environment
    variables.</p>

    <p>The first argument to this directive is always
    <code>from</code>. The subsequent arguments can take three
    different forms. If <code>Allow from all</code> is specified, then
    all hosts are allowed access, subject to the configuration of the
    <directive module="mod_access">Deny</directive> and <directive
    module="mod_access">Order</directive> directives as discussed
    below. To allow only particular hosts or groups of hosts to access
    the server, the <var>host</var> can be specified in any of the
    following formats:</p>

    <dl>
      <dt>A (partial) domain-name</dt>

      <dd>
      <example><title>Example:</title>
        Allow from apache.org<br />
        Allow from .net example.edu
      </example>
      <p>Hosts whose names match, or end in, this string are allowed
      access. Only complete components are matched, so the above
      example will match <code>foo.apache.org</code> but it will not
      match <code>fooapache.org</code>. This configuration will cause
      Apache to perform a double reverse DNS lookup on the client IP
      address, regardless of the setting of the <directive
      module="core">HostnameLookups</directive> directive.  It will do
      a reverse DNS lookup on the IP address to find the associated
      hostname, and then do a forward lookup on the hostname to assure
      that it matches the original IP address.  Only if the forward
      and reverse DNS are consistent and the hostname matches will
      access be allowed.</p></dd>

      <dt>A full IP address</dt>

      <dd>
      <example><title>Example:</title>
        Allow from 10.1.2.3<br />
        Allow from 192.168.1.104 192.168.1.205
      </example>
      <p>An IP address of a host allowed access</p></dd>

      <dt>A partial IP address</dt>

      <dd>
      <example><title>Example:</title>
        Allow from 10.1<br />
        Allow from 10 172.20 192.168.2
      </example>
      <p>The first 1 to 3 bytes of an IP address, for subnet
      restriction.</p></dd>

      <dt>A network/netmask pair</dt>

      <dd>
      <example><title>Example:</title>
        Allow from 10.1.0.0/255.255.0.0
      </example>
      <p>A network a.b.c.d, and a netmask w.x.y.z. For more
      fine-grained subnet restriction.</p></dd>

      <dt>A network/nnn CIDR specification</dt>

      <dd>
      <example><title>Example:</title>
        Allow from 10.1.0.0/16
      </example>
      <p>Similar to the previous case, except the netmask consists of
      nnn high-order 1 bits.</p></dd>
    </dl>

    <p>Note that the last three examples above match exactly the
    same set of hosts.</p>

    <p>IPv6 addresses and IPv6 subnets can be specified as shown
    below:</p>

    <example>
       Allow from 2001:db8::a00:20ff:fea7:ccea<br />
       Allow from 2001:db8::a00:20ff:fea7:ccea/10
    </example>

    <p>The third format of the arguments to the
    <directive>Allow</directive> directive allows access to the server
    to be controlled based on the existence of an <a
    href="../env.html">environment variable</a>. When <code>Allow from
    env=<var>env-variable</var></code> is specified, then the request is
    allowed access if the environment variable <var>env-variable</var>
    exists. The server provides the ability to set environment
    variables in a flexible way based on characteristics of the client
    request using the directives provided by
    <module>mod_setenvif</module>.  Therefore, this directive can be
    used to allow access based on such factors as the clients
    <code>User-Agent</code> (browser type), <code>Referer</code>, or
    other HTTP request header fields.</p>

    <example><title>Example:</title>
      SetEnvIf User-Agent ^KnockKnock/2\.0 let_me_in<br />
      &lt;Directory /docroot&gt;<br />
      <indent>
        Order Deny,Allow<br />
        Deny from all<br />
        Allow from env=let_me_in<br />
      </indent>
      &lt;/Directory&gt;
    </example>

    <p>In this case, browsers with a user-agent string beginning
    with <code>KnockKnock/2.0</code> will be allowed access, and all
    others will be denied.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>Deny</name>
<description>Controls which hosts are denied access to the
server</description>
<syntax> Deny from all|<var>host</var>|env=<var>env-variable</var>
[<var>host</var>|env=<var>env-variable</var>] ...</syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>Limit</override>

<usage>
    <p>This directive allows access to the server to be restricted
    based on hostname, IP address, or environment variables. The
    arguments for the <directive>Deny</directive> directive are
    identical to the arguments for the <directive
    module="mod_access">Allow</directive> directive.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>Order</name>
<description>Controls the default access state and the order in which
<directive>Allow</directive> and <directive>Deny</directive> are
evaluated.</description>
<syntax> Order <var>ordering</var></syntax>
<default>Order Deny,Allow</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>Limit</override>

<usage>

    <p>The <directive>Order</directive> directive, along with the
    <directive module="mod_access">Allow</directive> and <directive
    module="mod_access">Deny</directive> directives, controls a
    three-pass access control system. The first pass processes either
    all <directive module="mod_access">Allow</directive> or all
    <directive module="mod_access">Deny</directive> directives, as
    specified by the <directive>Order</directive> directive. The second
    pass parses the rest of the directives (<directive
    module="mod_access">Deny</directive> or <directive
    module="mod_access">Allow</directive>). The third pass applies to
    all requests which do not match either of the first two.</p>

    <p>Note that all <directive module="mod_access">Allow</directive>
    and <directive module="mod_access">Deny</directive> directives are
    processed, unlike a typical firewall, where only the first match is
    used. The last match is effective (also unlike a typical firewall).
    Additionally, the order in which lines appear in the configuration
    files is not significant -- all <directive
    module="mod_access">Allow</directive> lines are processed as one
    group, all <directive module="mod_access">Deny</directive> lines are
    considered as another, and the default state is considered by
    itself.</p>

    <p><em>Ordering</em> is one of:</p>

    <dl>
      <dt><code>Allow,Deny</code></dt>

      <dd>First, all <directive module="mod_access">Allow</directive>
      directives are evaluated; at least one must match, or the request
      is rejected. Next, all <directive
      module="mod_access">Deny</directive> directives are evaluated. If
      any matches, the request is rejected. Last, any requests which do
      not match an <directive module="mod_access">Allow</directive> or a
      <directive module="mod_access">Deny</directive> directive are
      denied by default.</dd>

      <dt><code>Deny,Allow</code></dt>

      <dd>First, all <directive module="mod_access">Deny</directive>
      directives are evaluated; if any match, the request is denied
      <strong>unless</strong> it also matches an <directive
      module="mod_access">Allow</directive> directive. Any requests
      which do not match any <directive
      module="mod_access">Allow</directive> or <directive
      module="mod_access">Deny</directive> directives are
      permitted.</dd>

      <dt><code>Mutual-failure</code></dt>

      <dd>This order has the same effect as <code>Order
      Allow,Deny</code> and is deprecated in its favor.</dd>
    </dl>

    <p>Keywords may only be separated by a comma; <em>no whitespace</em>
    is allowed between them.</p>

    <table border="1">
      <tr>
        <th>Match</th>
        <th>Allow,Deny result</th>
        <th>Deny,Allow result</th>
      </tr><tr>
        <th>Match Allow only</th>
        <td>Request allowed</td>
        <td>Request allowed</td>
      </tr><tr>
        <th>Match Deny only</th>
        <td>Request denied</td>
        <td>Request denied</td>
      </tr><tr>
        <th>No match</th>
        <td>Default to second directive: Denied</td>
        <td>Default to second directive: Allowed</td>
      </tr><tr>
        <th>Match both Allow &amp; Deny</th>
        <td>Final match controls: Denied</td>
        <td>Final match controls: Allowed</td>
      </tr>
    </table>

    <p>In the following example, all hosts in the apache.org domain
    are allowed access; all other hosts are denied access.</p>

    <example>
      Order Deny,Allow<br />
      Deny from all<br />
      Allow from apache.org
    </example>

    <p>In the next example, all hosts in the apache.org domain are
    allowed access, except for the hosts which are in the foo.apache.org
    subdomain, who are denied access. All hosts not in the apache.org
    domain are denied access because the default state is to <directive
    module="mod_access">Deny</directive> access to the server.</p>

    <example>
      Order Allow,Deny<br />
      Allow from apache.org<br />
      Deny from foo.apache.org
    </example>

    <p>On the other hand, if the <directive>Order</directive> in the
    last example is changed to <code>Deny,Allow</code>, all hosts will
    be allowed access. This happens because, regardless of the actual
    ordering of the directives in the configuration file, the
    <code>Allow from apache.org</code> will be evaluated last and will
    override the <code>Deny from foo.apache.org</code>. All hosts not in
    the <code>apache.org</code> domain will also be allowed access
    because the default state is <directive
    module="mod_access">Allow</directive>.</p>

    <p>The presence of an <directive>Order</directive> directive can
    affect access to a part of the server even in the absence of
    accompanying <directive module="mod_access">Allow</directive> and
    <directive module="mod_access">Deny</directive> directives because
    of its effect on the default access state.  For example,</p>

    <example>
      &lt;Directory /www&gt;<br />
      <indent>
        Order Allow,Deny<br />
      </indent>
      &lt;/Directory&gt;
    </example>

    <p>will <directive module="mod_access">Deny</directive> all access
    to the <code>/www</code> directory because the default access state
    is set to <directive module="mod_access">Deny</directive>.</p>

    <p>The <directive>Order</directive> directive controls the order of
    access directive processing only within each phase of the server's
    configuration processing. This implies, for example, that an
    <directive module="mod_access">Allow</directive> or <directive
    module="mod_access">Deny</directive> directive occurring in a
    <directive module="core" type="section">Location</directive> section
    will always be evaluated after an <directive
    module="mod_access">Allow</directive> or <directive
    module="mod_access">Deny</directive> directive occurring in a
    <directive module="core" type="section">Directory</directive>
    section or <code>.htaccess</code> file, regardless of the setting of
    the <directive>Order</directive> directive. For details on the
    merging of configuration sections, see the documentation on <a
    href="../sections.html">How Directory, Location and Files sections
    work</a>.</p>
</usage>
</directivesynopsis>

</modulesynopsis>