This module implements a proxy/gateway for Apache. It implements
proxying capability for
FTP,
CONNECT (for SSL),
HTTP/0.9,
HTTP/1.0, and
HTTP/1.1.
The module can be configured to connect to other proxy modules for these
and other protocols.
This module was experimental in Apache 1.1.x. Improvements and bugfixes were made in Apache v1.2.x and Apache v1.3.x, then the module underwent a major overhaul for Apache v2.0. The protocol support was upgraded to HTTP/1.1, and filter support was enabled.
Please note that the caching function present in mod_proxy up to Apache v1.3.x has been removed from mod_proxy and will be incorporated into a new module, mod_cache.
Apache can be configured in both a forward and reverse proxy configuration.
A forward proxy is an intermediate system that enables a browser to connect to a remote network to which it normally does not have access. A forward proxy can also be used to cache data, reducing load on the networks between the forward proxy and the remote webserver.
Apache's mod_proxy can be figured to behave like a forward proxy
using the
A reverse proxy is a webserver system that is capable of serving webpages sourced from other webservers - in addition to webpages on disk or generated dynamically by CGI - making these pages look like they originated at the reverse proxy.
When configured with the mod_cache module the reverse proxy can act as a cache for slower backend webservers. The reverse proxy can also enable advanced URL strategies and management techniques, allowing webpages served using different webserver systems or architectures to coexist inside the same URL space. Reverse proxy systems are also ideal for implementing centralised logging websites with many or diverse website backends. Complex multi-tier webserver systems can be constructed using an Apache mod_proxy frontend and any number of backend webservers.
The reverse proxy is configured using the
You can control who can access your proxy via the normal
A
When configuring a reverse proxy, access control takes on the
attributes of the normal server
You probably don't have that particular file type defined as application/octet-stream in your proxy's mime.types configuration file. A useful line can be
In the rare situation where you must download a specific file using the FTP
ASCII transfer method (while the default transfer is in
binary mode), you can override mod_proxy's default by
suffixing the request with ;type=a to force an ASCII transfer.
(FTP Directory listings are always executed in ASCII mode, however.)
An FTP URI is interpreted relative to the home directory of the user who is logging in. Alas, to reach higher directory levels you cannot use /../, as the dots are interpreted by the browser and not actually sent to the FTP server. To address this problem, the so called "Squid %2f hack" was implemented in the Apache FTP proxy; it is is a solution which is also used by other popular proxy servers like the Squid Proxy Cache. By prepending /%2f to the path of your request, you can make such a proxy change the FTP starting directory to / (instead of the home directory).
Example: To retrieve the file
/etc/motd, you would use the URL
To log in to an FTP server by username and password, Apache uses different strategies. In absense of a user name and password in the URL altogether, Apache sends an anomymous login to the FTP server, i.e.,
This works for all popular FTP servers which are configured for anonymous access.
For a personal login with a specific username, you can embed
the user name into the URL, like in:
ftp://username@host/myfile. If the FTP server
asks for a password when given this username (which it should),
then Apache will reply with a [401 Authorization required] response,
which causes the Browser to pop up the username/password dialog.
Upon entering the password, the connection attempt is retried,
and if successful, the requested resource is presented.
The advantage of this procedure is that your browser does not
display the password in cleartext (which it would if you had used
ftp://username:password@host/myfile in
the first place).
If you're using the
An Apache proxy server situated in an intranet needs to forward
external requests through the company's firewall. However, when it has
to access resources within the intranet, it can bypass the firewall
when accessing hosts. The
Users within an intranet tend to omit the local domain name from their
WWW requests, thus requesting "http://somehost/" instead of
"http://somehost.my.dom.ain/". Some commercial proxy servers let them get
away with this and simply serve the request, implying a configured
local domain. When the
When enabled, this option will pass the Host: line from the incoming request to the proxied host, instead of the hostname specified in the proxypass line.
This option should normally be turned 'off'.
This allows or prevents Apache from functioning as a forward proxy
server. (Setting ProxyRequests to 'off' does not disable use of the
In a typical reverse proxy configuration, this option should be set to 'off'.
This defines remote proxies to this proxy. match is either the name of a URL-scheme that the remote server supports, or a partial URL for which the remote server should be used, or '*' to indicate the server should be contacted for all requests. remote-server is a partial URL for the remote server. Syntax:
remote-server = protocol://hostname[:port]
protocol is the protocol that should be used to communicate with the remote server; only "http" is supported by this module.
Example:
In the last example, the proxy will forward FTP requests, encapsulated as yet another HTTP proxy request, to another proxy which can handle them.
This option also supports reverse proxy configuration - a backend webserver can be embedded within a virtualhost URL space even if that server is hidden by another forward proxy.
This directive allows remote servers to be mapped into the space of the local server; the local server does not act as a proxy in the conventional sense, but appears to be a mirror of the remote server. path is the name of a local virtual path; url is a partial URL for the remote server.
Suppose the local server has address http://wibble.org/;
then
will cause a local request for the
<http://wibble.org/mirror/foo/bar> to be
internally converted into a proxy request to
<http://foo.com/bar>.
The ! directive is useful in situations where you don't want to reverse-proxy a subdirectory. eg.
will proxy all requests to /mirror/foo to foo.com EXCEPT requests made to /mirror/foo/i
This directive lets Apache adjust the URL in the Location,
Content-Location and URI headers on
HTTP redirect responses. This is essential when Apache is used as
a reverse proxy to avoid by-passing the reverse proxy because of HTTP
redirects on the backend servers which stay behind the reverse proxy.
path is the name of a local virtual path.
url is a partial URL for the remote server - the same way they are
used for the
Example:
Suppose the local server has address http://wibble.org/; then
will not only cause a local request for the
<http://wibble.org/mirror/foo/bar> to be internally
converted into a proxy request to <http://foo.com/bar> (the
functionality ProxyPass provides here). It also takes care of
redirects the server foo.com sends: when http://foo.com/bar is
redirected by him to http://foo.com/quux Apache adjusts this to
http://wibble.org/mirror/foo/quux before forwarding the HTTP
redirect response to the client.
Note that this RewriteRule ... [P]") from
The CONNECT method may
connect. Today's browsers use this method when a https
connection is requested and proxy tunneling over http is in
effect.
By default, only the default https port (443) and the
default snews port (563) are enabled. Use the
The
'rocky.wotsamattau.edu' would also be matched if referenced by IP address.
Note that 'wotsamattau' would also be sufficient to match 'wotsamattau.edu'.
Note also that
blocks connections to all sites.
The
The
This directive is only useful for Apache proxy servers within
intranets. The
The arguments to the NoProxy directive are one of the following type list:
.com .apache.org..MyDomain.com and
.mydomain.com. (note the trailing period) are
considered equal. Since a domain comparison does not involve a DNS
lookup, it is much more efficient than subnet comparison.192.168 or 192.168.0.0255.255.0.0)192.168.112.0/21192.168.112.0/21 with a netmask of 21
valid bits (also used in the form 255.255.248.0)prep.ai.mit.edu
www.apache.org.WWW.MyDomain.com
and www.mydomain.com. (note the trailing period) are
considered equal.This directive allows a user to specifiy a timeout on proxy requests. This is usefull when you have a slow/buggy appserver which hangs, and you would rather just return a timeout and fail gracefully instead of waiting however long it takes the server to return
This directive is only useful for Apache proxy servers within
intranets. The
This directive controls the use of the Via: HTTP
header by the proxy. Its intended use is to control the flow of of
proxy requests along a chain of proxy servers. See RFC2068 (HTTP/1.1)
for an explanation of Via: header lines.
Via: header,
it is passed through unchanged.Via: header line added for
the current host.Via: header
line will additionally have the Apache server version shown as a
Via: comment field.Via: header lines
removed. No new Via: header will be generated.This directive is useful for reverse-proxy setups, where you want to have a common look and feel on the error pages seen by the end user. This also allows for included files (via mod_include's SSI) to get the error code and act accordingly (default behavior would display the error page of the proxied server, turning this on shows the SSI Error message).