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<h3>Apache HTTP Server Version 1.3</h3>
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<h1 align="center">Module mod_access</h1>
<p>This module provides access control based on client
hostname, IP address, or other characteristics of the client
request.</p>
<p><a href="module-dict.html#Status"
rel="Help"><strong>Status:</strong></a> Base<br />
<a href="module-dict.html#SourceFile"
rel="Help"><strong>Source File:</strong></a> mod_access.c<br />
<a href="module-dict.html#ModuleIdentifier"
rel="Help"><strong>Module Identifier:</strong></a>
access_module</p>
<h2>Summary</h2>
<p>The directives provided by mod_access are used in <code><a
href="core.html#directory"><Directory></a>, <a
href="core.html#files"><Files></a>,</code> and <code><a
href="core.html#location"><Location></a></code> 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
<code>Allow</code> and <code>Deny</code> directives are used to
specify which clients are or are not allowed access to the
server, while the <code>Order</code> directive sets the default
access state, and configures how the <code>Allow</code> and
<code>Deny</code> directives interact with each other.</p>
<p>Both host-based access restrictions and password-based
authentication may be implemented simultaneously. In that case,
the <a href="core.html#satisfy">Satisfy</a> 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 <a href="core.html#limit"><Limit></a> section.</p>
<h2>Directives</h2>
<ul>
<li><a href="#allow">Allow</a></li>
<li><a href="#deny">Deny</a></li>
<li><a href="#order">Order</a></li>
</ul>
<p>See also <a href="core.html#satisfy">Satisfy</a> and <a
href="core.html#require">Require</a>.</p>
<hr />
<h2><a id="allow" name="allow">Allow</a> <a id="allowfromenv"
name="allowfromenv">directive</a></h2>
<p>
<a href="directive-dict.html#Syntax"
rel="Help"><strong>Syntax:</strong></a> Allow from
all|<em>host</em>|env=<em>env-variable</em>
[<em>host</em>|env=<em>env-variable</em>] ...<br />
<a href="directive-dict.html#Context"
rel="Help"><strong>Context:</strong></a> directory,
.htaccess<br />
<a href="directive-dict.html#Override"
rel="Help"><strong>Override:</strong></a> Limit<br />
<a href="directive-dict.html#Status"
rel="Help"><strong>Status:</strong></a> Base<br />
<a href="directive-dict.html#Module"
rel="Help"><strong>Module:</strong></a> mod_access</p>
<p>The <code>Allow</code> directive affects which hosts can
access an area of the server. Access can be controlled by
hostname, IP address, IP address range, or 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 <code>Deny</code> and <code>Order</code> directives as
discussed below. To allow only particular hosts or groups of
hosts to access the server, the <em>host</em> can be specified
in any of the following formats:</p>
<dl>
<dt>A (partial) domain-name</dt>
<dd>Example: <code>Allow from apache.org</code><br />
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 the server to perform a double reverse DNS lookup on the
client IP address, regardless of the setting of the <a
href="core.html#hostnamelookups">HostnameLookups</a>
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.</dd>
<dt>A full IP address</dt>
<dd>Example: <code>Allow from 10.1.2.3</code><br />
An IP address of a host allowed access</dd>
<dt>A partial IP address</dt>
<dd>Example: <code>Allow from 10.1</code><br />
The first 1 to 3 bytes of an IP address, for subnet
restriction.</dd>
<dt>A network/netmask pair</dt>
<dd>Example: <code>Allow from
10.1.0.0/255.255.0.0</code><br />
A network a.b.c.d, and a netmask w.x.y.z. For more
fine-grained subnet restriction. (Apache 1.3 and later)</dd>
<dt>A network/nnn CIDR specification</dt>
<dd>Example: <code>Allow from 10.1.0.0/16</code><br />
Similar to the previous case, except the netmask consists of
nnn high-order 1 bits. (Apache 1.3 and later)</dd>
</dl>
<p>Note that the last three examples above match exactly the
same set of hosts.</p>
<p>The third format of the arguments to the <code>Allow</code>
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=</code><em>env-variable</em> is specified, then the request
is allowed access if the environment variable
<em>env-variable</em> 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 <a href="mod_setenvif.html">mod_setenvif</a>.
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>
<p>Example:</p>
<blockquote>
<pre>
SetEnvIf User-Agent ^KnockKnock/2\.0 let_me_in
<Directory /docroot>
Order Deny,Allow
Deny from all
Allow from env=let_me_in
</Directory>
</pre>
</blockquote>
<p>In this case, browsers with a user-agent string beginning
with <tt>KnockKnock/2.0</tt> will be allowed access, and all
others will be denied.</p>
<p>See also <a href="#deny">Deny</a>, <a
href="#order">Order</a> and <a
href="mod_setenvif.html#setenvif">SetEnvIf</a>.</p>
<hr />
<h2><a id="deny" name="deny">Deny</a> <a id="denyfromenv"
name="denyfromenv">directive</a></h2>
<p>
<a href="directive-dict.html#Syntax"
rel="Help"><strong>Syntax:</strong></a> Deny from
all|<em>host</em>|env=<em>env-variable</em>
[<em>host</em>|env=<em>env-variable</em>] ...<br />
<a href="directive-dict.html#Context"
rel="Help"><strong>Context:</strong></a> directory,
.htaccess<br />
<a href="directive-dict.html#Override"
rel="Help"><strong>Override:</strong></a> Limit<br />
<a href="directive-dict.html#Status"
rel="Help"><strong>Status:</strong></a> Base<br />
<a href="directive-dict.html#Module"
rel="Help"><strong>Module:</strong></a> mod_access</p>
<p>This directive allows access to the server to be restricted
based on hostname, IP address, or environment variables. The
arguments for the <code>Deny</code> directive are identical to
the arguments for the <a href="#allow">Allow</a> directive.</p>
<p>See also <a href="#allow">Allow</a>, <a
href="#order">Order</a> and <a
href="mod_setenvif.html#setenvif">SetEnvIf</a>.</p>
<hr />
<h2><a id="order" name="order">Order directive</a></h2>
<p>
<a href="directive-dict.html#Syntax"
rel="Help"><strong>Syntax:</strong></a> Order
<em>ordering</em><br />
<a href="directive-dict.html#Default"
rel="Help"><strong>Default:</strong></a> <code>Order
Deny,Allow</code><br />
<a href="directive-dict.html#Context"
rel="Help"><strong>Context:</strong></a> directory,
.htaccess<br />
<a href="directive-dict.html#Override"
rel="Help"><strong>Override:</strong></a> Limit<br />
<a href="directive-dict.html#Status"
rel="Help"><strong>Status:</strong></a> Base<br />
<a href="directive-dict.html#Module"
rel="Help"><strong>Module:</strong></a> mod_access</p>
<p>The <code>Order</code> directive, along with the
<code>Allow</code> and <code>Deny</code> directives, controls a
three-pass access control system. The first pass processes either
all <code>Allow</code> or all <code>Deny</code> directives, as
specified by the <code>Order</code> directive. The second pass
parses the rest of the directives (<code>Deny</code> or
<code>Allow</code>). The third pass applies to all requests which do
not match either of the first two.</p>
<p>Note that all <code>Allow</code> and <code>Deny</code> 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 <code>Allow</code>
lines are processed as one group, all <code>Deny</code> 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 <code>Allow</code> directives are evaluated; at
least one must match, or the request is rejected. Next, all
<code>Deny</code> directives are evaluated. If any matches, the
request is rejected. Last, any requests which do not match an
<code>Allow</code> or a <code>Deny</code> directive are denied by
default.</dd>
<dt><code>Deny,Allow</code></dt>
<dd>First, all <code>Deny</code> directives are evaluated; if any
match, the request is denied <strong>unless</strong> it also
matches an <code>Allow</code> directive. Any requests which do not
match any <code>Allow</code> or <code>Deny</code> 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; no whitespace 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>
<blockquote>
<code>Order Deny,Allow<br />
Deny from all<br />
Allow from apache.org<br />
</code>
</blockquote>
<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 <code>Deny</code> access to the server.</p>
<blockquote>
<code>Order Allow,Deny<br />
Allow from apache.org<br />
Deny from foo.apache.org<br />
</code>
</blockquote>
<p>On the other hand, if the <code>Order</code> 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
<code>Allow</code>.</p>
<p>The presence of an <code>Order</code> directive can affect
access to a part of the server even in the absence of
accompanying <code>Allow</code> and <code>Deny</code>
directives because of its effect on the default access state.
For example,</p>
<blockquote>
<code><Directory /www><br />
Order Allow,Deny<br />
</Directory></code>
</blockquote>
<p>will Deny all access to the <code>/www</code> directory
because the default access state is set to
<code>Deny</code>.</p>
<p>The <code>Order</code> directive controls the order of
access directive processing only within each phase of the
server's configuration processing. This implies, for example,
that an <code>Allow</code> or <code>Deny</code> directive
occurring in a <Location> section will always be
evaluated after an <code>Allow</code> or <code>Deny</code>
directive occurring in a <Directory> section or
<code>.htaccess</code> file, regardless of the setting of the
<code>Order</code> 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>
<p>See also: <a href="#deny">Deny</a> and <a
href="#allow">Allow</a>. <hr />
<h3 align="CENTER">Apache HTTP Server Version 1.3</h3>
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