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<?xml version="1.0"?>
<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
<!-- $LastChangedRevision$ -->
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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 />
<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, 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 & 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>
<Directory /www><br />
<indent>
Order Allow,Deny<br />
</indent>
</Directory>
</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>
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