Chip 2004 November/CMCD1104.ISO/Software/Complet/Apache/apache_2.0.52-win32-x86-no_ssl.msi/Data.Cab/F278218_mod_access.xml

Extensible Markup Language | 2004-04-17 | 14KB | 337 lines

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

<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
      </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
      </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
      </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 fe80::a00:20ff:fea7:ccea<br />
       Allow from fe80::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 />
      <Directory /docroot><br />
      <indent>
        Order Deny,Allow<br />
        Deny from all<br />
        Allow from env=let_me_in<br />
      </indent>
      </Directory>
    </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 controls the default
    access state and the order in which <directive
    module="mod_access">Allow</directive> and <directive
    module="mod_access">Deny</directive> directives are evaluated.
    <var>Ordering</var> is one of</p>

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

      <dd>The <directive module="mod_access">Deny</directive> directives
      are evaluated before the <directive
      module="mod_access">Allow</directive> directives. Access is
      allowed by default.  Any client which does not match a
      <directive module="mod_access">Deny</directive> directive or does
      match an <directive module="mod_access">Allow</directive>
      directive will be allowed access to the server.</dd>

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

      <dd>The <directive module="mod_access">Allow</directive>
      directives are evaluated before the <directive
      module="mod_access">Deny</directive> directives. Access is denied
      by default. Any client which does not match an <directive
      module="mod_access">Allow</directive> directive or does match a
      <directive module="mod_access">Deny</directive> directive will be
      denied access to the server.</dd>

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

      <dd>Only those hosts which appear on the <directive
      module="mod_access">Allow</directive> list and do not appear on
      the <directive module="mod_access">Deny</directive> list are
      granted access. This ordering has the same effect as <code>Order
      Allow,Deny</code> and is deprecated in favor of that
      configuration.</dd>
    </dl>

    <p>Keywords may only be separated by a comma; <em>no whitespace</em> is
    allowed between them. Note that in all cases every <directive
    module="mod_access">Allow</directive> and <directive
    module="mod_access">Deny</directive> statement is evaluated.</p>

    <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 deny 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 will change to
    <var>allow</var>.</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>
      <Directory /www><br />
      <indent>
        Order Allow,Deny<br />
      </indent>
      </Directory>
    </example>

    <p>will deny all access to the <code>/www</code> directory
    because the default access state will be set to
    <var>deny</var>.</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>