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=encoding utf-8
=head1 NAME
ngx_http_referer_module - Module ngx_http_referer_module
=head1
The C<ngx_http_referer_module> module is used to block
access to a site for requests with invalid values in the
C<Referer> header field.
It should be kept in mind that fabricating a request with an appropriate
C<Referer> field value is quite easy, and so the intended
purpose of this module is not to block such requests thoroughly but to block
the mass flow of requests sent by regular browsers.
It should also be taken into consideration that regular browsers may
not send the C<Referer> field even for valid requests.
=head1 Example Configuration
valid_referers none blocked server_names
*.example.com example.* www.example.org/galleries/
~\.google\.;
if ($invalid_referer) {
return 403;
}
=head1 Directives
=head2 referer_hash_bucket_size
B<syntax:> referer_hash_bucket_size I<I<C<size>>>
B<default:> I<64>
B<context:> I<server>
B<context:> I<location>
This directive appeared in version 1.0.5.
Sets the bucket size for the valid referers hash tables.
The details of setting up hash tables are provided in a separate
L<document|hash>.
=head2 referer_hash_max_size
B<syntax:> referer_hash_max_size I<I<C<size>>>
B<default:> I<2048>
B<context:> I<server>
B<context:> I<location>
This directive appeared in version 1.0.5.
Sets the maximum I<C<size>> of the valid referers hash tables.
The details of setting up hash tables are provided in a separate
L<document|hash>.
=head2 valid_referers
B<syntax:> valid_referers I<
C<none> E<verbar>
C<blocked> E<verbar>
C<server_names> E<verbar>
I<C<string>>
...>
B<context:> I<server>
B<context:> I<location>
Specifies the C<Referer> request header field values
that will cause the embedded C<$invalid_referer> variable to
be set to an empty string.
Otherwise, the variable will be set to “C<1>”.
Search for a match is case-insensitive.
Parameters can be as follows:
=over
=item C<none>
the C<Referer> field is missing in the request header;
=item C<blocked>
the C<Referer> field is present in the request header,
but its value has been deleted by a firewall or proxy server;
such values are strings that do not start with
“C<http:E<sol>E<sol>>” or “C<https:E<sol>E<sol>>”;
=item C<server_names>
the C<Referer> request header field contains
one of the server names;
=item arbitrary string
defines a server name and an optional URI prefix.
A server name can have an “C<*>” at the beginning or end.
During the checking, the server’s port in the C<Referer> field
is ignored;
=item regular expression
the first symbol should be a “C<~>”.
It should be noted that an expression will be matched against
the text starting after the “C<http:E<sol>E<sol>>”
or “C<https:E<sol>E<sol>>”.
=back
Example:
valid_referers none blocked server_names
*.example.com example.* www.example.org/galleries/
~\.google\.;
=head1 Embedded Variables
=over
=item C<$invalid_referer>
Empty string, if the C<Referer> request header field
value is considered
valid, otherwise “C<1>”.
=back
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