/Apache HTTP Server

Apache Module mod_authz_host

Description: Group authorizations based on host (name or IP address)
Status: Base
ModuleIdentifier: authz_host_module
SourceFile: mod_authz_host.c
Compatibility: The forward-dns provider was addded in 2.4.19


The authorization providers implemented by mod_authz_host are registered using the Require directive. The directive can be referenced within a <Directory>, <Files>, or <Location> section as well as .htaccess files to control access to particular parts of the server. Access can be controlled based on the client hostname or IP address.

In general, access restriction directives apply to all access methods (GET, PUT, 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 <Limit> section.

The Require Directives

Apache's Require directive is used during the authorization phase to ensure that a user is allowed or denied access to a resource. mod_authz_host extends the authorization types with ip, host, forward-dns and local. Other authorization types may also be used but may require that additional authorization modules be loaded.

These authorization providers affect which hosts can access an area of the server. Access can be controlled by hostname, IP Address, or IP Address range.

Since v2.4.8, expressions are supported within the host require directives.

Require ip

The ip provider allows access to the server to be controlled based on the IP address of the remote client. When Require ip ip-address is specified, then the request is allowed access if the IP address matches.

A full IP address:

Require ip
Require ip

An IP address of a host allowed access

A partial IP address:

Require ip 10.1
Require ip 10 172.20 192.168.2

The first 1 to 3 bytes of an IP address, for subnet restriction.

A network/netmask pair:

Require ip

A network a.b.c.d, and a netmask w.x.y.z. For more fine-grained subnet restriction.

A network/nnn CIDR specification:

Require ip

Similar to the previous case, except the netmask consists of nnn high-order 1 bits.

Note that the last three examples above match exactly the same set of hosts.

IPv6 addresses and IPv6 subnets can be specified as shown below:

Require ip 2001:db8::a00:20ff:fea7:ccea
Require ip 2001:db8:1:1::a
Require ip 2001:db8:2:1::/64
Require ip 2001:db8:3::/48

Note: As the IP addresses are parsed on startup, expressions are not evaluated at request time.

Require host

The host provider allows access to the server to be controlled based on the host name of the remote client. When Require host host-name is specified, then the request is allowed access if the host name matches.

A (partial) domain-name

Require host example.org
Require host .net example.edu

Hosts whose names match, or end in, this string are allowed access. Only complete components are matched, so the above example will match foo.example.org but it will not match fooexample.org. This configuration will cause Apache to perform a double reverse DNS lookup on the client IP address, regardless of the setting of the HostnameLookups 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.

Require forward-dns

The forward-dns provider allows access to the server to be controlled based on simple host names. When Require forward-dns host-name is specified, all IP addresses corresponding to host-name are allowed access.

In contrast to the host provider, this provider does not rely on reverse DNS lookups: it simply queries the DNS for the host name and allows a client if its IP matches. As a consequence, it will only work with host names, not domain names. However, as the reverse DNS is not used, it will work with clients which use a dynamic DNS service.

Require forward-dns bla.example.org

A client the IP of which is resolved from the name bla.example.org will be granted access.

The forward-dns provider was added in 2.4.19.

Require local

The local provider allows access to the server if any of the following conditions is true:

  • the client address matches
  • the client address is ::1
  • both the client and the server address of the connection are the same

This allows a convenient way to match connections that originate from the local host:

Require local

Security Note

If you are proxying content to your server, you need to be aware that the client address will be the address of your proxy server, not the address of the client, and so using the Require directive in this context may not do what you mean. See mod_remoteip for one possible solution to this problem.

© 2017 The Apache Software Foundation
Licensed under the Apache License, Version 2.0.