Warning: This document has been updated to take into account changes made in the 2.0 version of the Apache HTTP Server. Some of the information may still be inaccurate, please use it with care.
This module provides for an HTTP 1.1 proxy / gateway server.
Status: Extension
Source File: mod_proxy.c
Module Identifier: proxy_module
Compatibility: Available in Apache 1.1 and later.
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.
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 ProxyRemote directive. In addition, caching of data can be achieved by configuring Apache mod_cache. Other dedicated forward proxy packages include Squid.
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 ProxyPass and ProxyPassReverse directives. Caching can be enabled using mod_cache as with the forward proxy.
<Directory proxy:*> Order Deny,Allow Deny from [machines you'd like *not* to allow by IP address or name] Allow from [machines you'd like to allow by IP address or name] </Directory>
A <Files> block will also work, and is the only method known to work for all possible URLs in Apache versions earlier than 1.2b10.
When configuring a reverse proxy, access control takes on the attributes of
the normal server
Why doesn't file type xxx download via FTP?
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
application/octet-stream bin dms lha lzh exe class tgz taz
How can I force an FTP ASCII download of File xxx?
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
ftp://user@host/%2f/etc/motd
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.,
user: anonymous
password: apache_proxy@
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).
ProxyBlock
directive, hostnames' IP addresses are looked up and cached during
startup for later match test. This may take a few seconds (or more)
depending on the speed with which the hostname lookups occur.
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 NoProxy directive is useful for specifying which hosts belong to the intranet and should be accessed directly.
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 ProxyDomain directive is used and the server is configured for proxy service, Apache can return a redirect response and send the client to the correct, fully qualified, server address. This is the preferred method since the user's bookmark files will then contain fully qualified hosts.
ProxyPreserveHost OffWhen 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'.
ProxyRequests OffThis allows or prevents Apache from functioning as a forward proxy server. (Setting ProxyRequests to 'off' does not disable use of the ProxyPass directive.)
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:
ProxyRemote http://goodguys.com/ http://mirrorguys.com:8000 ProxyRemote * http://cleversite.com ProxyRemote ftp http://ftpproxy.mydomain.com:8080In 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
ProxyPass /mirror/foo/ http://foo.com/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.
ProxyPass /mirror/foo/i !
ProxyPass /mirror/foo http://foo.com
will proxy all requests to /mirror/foo to foo.com EXCEPT requests made to /mirror/foo/i
NB: order is important. you need to put the exclusions BEFORE the general proxypass directive
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 ProxyPass directive.
Example:
Suppose the local server has address http://wibble.org/; then
ProxyPass /mirror/foo/ http://foo.com/ ProxyPassReverse /mirror/foo/ http://foo.com/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 ProxyPassReverse directive can also be used in conjunction with the proxy pass-through feature ("RewriteRule ... [P]") from mod_rewrite because its doesn't depend on a corresponding ProxyPass directive.
The AllowCONNECT directive specifies a list of port numbers
to which the proxy 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 AllowCONNECT
directive to overrride this default and allow connections to the
listed ports only.
The ProxyBlock directive specifies a list of words, hosts and/or domains, separated by spaces. HTTP, HTTPS, and FTP document requests to sites whose names contain matched words, hosts or domains are blocked by the proxy server. The proxy module will also attempt to determine IP addresses of list items which may be hostnames during startup, and cache them for match test as well. Example:
ProxyBlock joes-garage.com some-host.co.uk rocky.wotsamattau.edu'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
ProxyBlock *blocks connections to all sites.
The ProxyReceiveBufferSize directive specifies an explicit network buffer size for outgoing HTTP and FTP connections, for increased throughput. It has to be greater than 512 or set to 0 to indicate that the system's default buffer size should be used.
Example:
ProxyReceiveBufferSize 2048
The ProxyMaxForwards directive specifies the maximum number of proxies through which a request may pass. This is set to prevent infinite proxy loops, or a DoS attack.
Example:
ProxyMaxForwards 10
This directive is only useful for Apache proxy servers within intranets. The NoProxy directive specifies a list of subnets, IP addresses, hosts and/or domains, separated by spaces. A request to a host which matches one or more of these is always served directly, without forwarding to the configured ProxyRemote proxy server(s).
Example:
ProxyRemote * http://firewall.mycompany.com:81 NoProxy .mycompany.com 192.168.112.0/21The arguments to the NoProxy directive are one of the following type list:
See Also: DNS Issues
See Also: DNS Issues
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 ProxyDomain directive specifies the default domain which the apache proxy server will belong to. If a request to a host without a domain name is encountered, a redirection response to the same host with the configured Domain appended will be generated.
Example:
ProxyRemote * http://firewall.mycompany.com:81 NoProxy .mycompany.com 192.168.112.0/21 ProxyDomain .mycompany.com
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.
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).