Access Control - Apache HTTP Server

Apache HTTP Server Version 2.2

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# Access Control

Available Languages: en

Access control refers to any means of controlling access to any resource. This is separate from authentication and authorization.

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## Related Modules and Directives

Access control can be done by several different modules. The most important of these is `mod_authz_host`. Other modules discussed in this document include `mod_setenvif` and `mod_rewrite`.

## Access control by host

If you wish to restrict access to portions of your site based on the host address of your visitors, this is most easily done using `mod_authz_host`.

The `Allow` and `Deny` directives let you allow and deny access based on the host name, or host address, of the machine requesting a document. The `Order` directive goes hand-in-hand with these two, and tells Apache in which order to apply the filters.

The usage of these directives is:

`Allow from address`

where address is an IP address (or a partial IP address) or a fully qualified domain name (or a partial domain name); you may provide multiple addresses or domain names, if desired.

For example, if you have someone spamming your message board, and you want to keep them out, you could do the following:

`Deny from 10.252.46.165`

Visitors coming from that address will not be able to see the content covered by this directive. If, instead, you have a machine name, rather than an IP address, you can use that.

`Deny from host.example.com`

And, if you'd like to block access from an entire domain, you can specify just part of an address or domain name:

`Deny from 192.168.205
Deny from phishers.example.com moreidiots.example
Deny from ke`

Using `Order` will let you be sure that you are actually restricting things to the group that you want to let in, by combining a `Deny` and an `Allow` directive:

`Order deny,allow
Deny from all
Allow from dev.example.com`

Listing just the `Allow` directive would not do what you want, because it will let folks from that host in, in addition to letting everyone in. What you want is to let only those folks in.

## Access control by environment variable

`mod_authz_host`, in conjunction with `mod_setenvif`, can be used to restrict access to your website based on the value of arbitrary environment variables. This is done with the `Allow from env=` and `Deny from env=` syntax.

`SetEnvIf User-Agent BadBot GoAway=1
Order allow,deny
Allow from all
Deny from env=GoAway`

### Warning:

Access control by `User-Agent` is an unreliable technique, since the `User-Agent` header can be set to anything at all, at the whim of the end user.

In the above example, the environment variable `GoAway` is set to `1` if the `User-Agent` matches the string `BadBot`. Then we deny access for any request when this variable is set. This blocks that particular user agent from the site.

An environment variable test can be negated using the `=!` syntax:

Allow from env=!GoAway

## Access control with mod_rewrite

The `[F]` `RewriteRule` flag causes a 403 Forbidden response to be sent. Using this, you can deny access to a resource based on arbitrary criteria.

For example, if you wish to block access to a resource between 8pm and 6am, you can do this using `mod_rewrite`.

`RewriteEngine On
RewriteCond %{TIME_HOUR} >20 [OR]
RewriteCond %{TIME_HOUR} <07
RewriteRule ^/fridge - [F]`

This will return a 403 Forbidden response for any request after 8pm or before 7am. This technique can be used for any criteria that you wish to check. You can also redirect, or otherwise rewrite these requests, if that approach is preferred.

## More information

You should also read the documentation for `mod_auth_basic` and `mod_authz_host` which contain some more information about how this all works. `mod_authn_alias` can also help in simplifying certain authentication configurations.

See the Authentication and Authorization howto.

Available Languages: en

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