Apache module mod_access
This module provides access control based on client hostname, IP address, or other characteristics of the client request.
Source File: mod_access.c
Module Identifier: access_module
The directives provided by mod_access are used in
, , and sections as well as
.htaccess 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 environment variables. The
Deny directives are used to specify which clients are or are not allowed access to the server, while the
Order directive sets the default access state, and configures how the
Deny directives interact with each other.
Both host-based access restrictions and password-based authentication may be implemented simultaneously. In that case, the Satisfy directive is used to determine how the two sets of restrictions interact.
In general, access restriction directives apply to all access methods (
POST, 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 section.
See also Satisfy and Require.
Syntax: Allow from all|host|env=variablename [host|env=variablename] …
Context: directory, .htaccess
Allow 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.
The first argument to this directive is always
from. The subsequent arguments can take three different forms. If
Allow from all is specified, then all hosts are allowed access, subject to the configuration of the
Order directives as discussed below. To allow only particular hosts or groups of hosts to access the server, the host can be specified in any of the following formats:
A (partial) domain-name Example:
Allow from apache.org
Hosts whose names match, or end in, this string are allowed access. Only complete components are matched, so the above example will match
foo.apache.org but it will not match
fooapache.org. This configuration will cause the server to perform a reverse DNS lookup on the client IP address, regardless of the setting of the HostNameLookups directive. A full IP address Example:
Allow from 10.1.2.3
An IP address of a host allowed access A partial IP address Example:
Allow from 10.1
The first 1 to 3 bytes of an IP address, for subnet restriction. A network/netmask pair Example:
Allow from 10.1.0.0/255.255.0.0
A network a.b.c.d, and a netmask w.x.y.z. For more fine-grained subnet restriction. (Apache 1.3 and later) A network/nnn CIDR specification Example:
Allow from 10.1.0.0/16
Similar to the previous case, except the netmask consists of nnn high-order 1 bits. (Apache 1.3 and later)
Note that the last three examples above match exactly the same set of hosts.
The third format of the arguments to the
Allow directive allows access to the server to be controlled based on the existence of an environment variable. When
Allow from env=variablename is specified, then the request is allowed access if the environment variable variablename 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 mod_setenvif. Therefore, this directive can be used to allow access based on such factors as the clients
User-Agent (browser type),
Referer, or other HTTP request header fields.
SetEnvIf User-Agent ^KnockKnock/2.0 let_me_in Order Deny,Allow Deny from all Allow from env=let_me_in
In this case, browsers with a user-agent string beginning with KnockKnock/2.0 will be allowed access, and all others will be denied.
See also Deny, Order and SetEnvIf.
Syntax: Deny from all|host|env=variablename [host|env=variablename] …
Context: directory, .htaccess
This directive allows access to the server to be restricted based on hostname, IP address, or environment variables. The arguments for the
Deny directive are identical to the arguments for the Allow directive.
See also Allow, Order and SetEnvIf.
Syntax: Order ordering
Context: directory, .htaccess
Order directive controls the default access state and the order in which Allow and Deny directives are evaluated. Ordering is one of
Deny directives are evaluated before the
Allow directives. Access is allowed by default. Any client which does not match a
Deny directive or does match an
Allow directive will be allowed access to the server. Allow,Deny The
Allow directives are evaluated before the
Deny directives. Access is denied by default. Any client which does not match an
Allow directive or does match a
Deny directive will be denied access to the server. Mutual-failure Only those hosts which appear on the
Allow list and do not appear on the
Deny list are granted access. This ordering has the same effect as
Order Allow,Deny and is deprecated in favor of that configuration.
Keywords may only be separated by a comma; no whitespace is allowed between them. Note that in all cases every
Deny statement is evaluated.
In the following example, all hosts in the apache.org domain are allowed access; all other hosts are denied access.
Order Deny,Allow Deny from all Allow from apache.org
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.
Order Allow,Deny Allow from apache.org Deny from foo.apache.org
On the other hand, if the
Order in the last example is changed to
Deny,Allow, all hosts will be allowed access. This happens because, regardless of the actual ordering of the directives in the configuration file, the
Allow from apache.org will be evaluated last and will override the
Deny from foo.apache.org. All hosts not in the
apache.org domain will also be allowed access because the default state will change to allow.
The presence of an
Order directive can affect access to a part of the server even in the absence of accompanying
Deny directives because of its effect on the default access state. For example,
will deny all access to the
/www directory because the default access state will be set to deny.
Order directive controls the order of access directive processing only within each phase of the server’s configuration processing. This implies, for example, that an
Deny directive occurring in a section will always be evaluated after an
Deny directive occurring in a section or
.htaccess file, regardless of the setting of the
Order directive. For details on the merging of configuration sections, see the documentation on How Directory, Location and Files sections work.
See also: Deny and Allow.
Apache HTTP Server Version 1.3