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
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.
This 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:
Example:
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
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.
Example:
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.
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:
Note that 'wotsamattau' would also be sufficient to match 'wotsamattau.edu'.
Note also that
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:
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:
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:
See Also:
DNS Issues See Also:
DNS Issues
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:
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 usefull for reverse-proxy setups, where you wan't 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 )
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.Why does Apache start more slowly when using the
proxy module?
If you're using the 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.What other functions are useful for an intranet proxy server?
ProxyRequests directive
Syntax: ProxyRequests on|off
Default: ProxyRequests Off
Context: server config, virtual host
Override: Not applicable
Status: Base
Module: mod_proxy
Compatibility: ProxyRequests is only available in
Apache 1.1 and later.
ProxyRemote directive
Syntax: ProxyRemote match remote-server
Default: None
Context: server config, virtual host
Override: Not applicable
Status: Base
Module: mod_proxy
Compatibility: ProxyRemote is only available in
Apache 1.1 and later.
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.
ProxyRemote http://goodguys.com/ http://mirrorguys.com:8000
ProxyRemote * http://cleversite.com
ProxyRemote ftp http://ftpproxy.mydomain.com:8080
In the last example, the proxy will forward FTP requests, encapsulated
as yet another HTTP proxy request, to another proxy which can handle
them.
ProxyPass directive
Syntax: ProxyPass path url
or: ProxyPass url when placed in a <location> directive (Apache 2.0 only)
Default: None
Context: server config, virtual host
Override: Not applicable
Status: Base
Module: mod_proxy
Compatibility: ProxyPass is only available in
Apache 1.1 and later.
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>.
ProxyPassReverse directive
Syntax: ProxyPassReverse path url
or: ProxyPassReverse url when placed in a <location> directive (Apache 2.0 only)
Default: None
Context: server config, virtual host
Override: Not applicable
Status: Base
Module: mod_proxy
Compatibility: ProxyPassReverse is only available in
Apache 1.3b6 and later.
url is a partial URL for the remote server - the same way they are
used for the ProxyPass directive.
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.
AllowCONNECT directive
Syntax: AllowCONNECT port
[port] ...
Default: AllowCONNECT 443 563
Context: server config, virtual host
Override: Not applicable
Status: Base
Module: mod_proxy
Compatibility: AllowCONNECT is only
available in Apache 1.3.2 and later.
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.
ProxyBlock directive
Syntax: ProxyBlock *|word|host|domain
[word|host|domain] ...
Default: None
Context: server config, virtual host
Override: Not applicable
Status: Base
Module: mod_proxy
Compatibility: ProxyBlock is only available in
Apache 1.2 and later.
ProxyBlock joes-garage.com some-host.co.uk rocky.wotsamattau.edu
'rocky.wotsamattau.edu' would also be matched if referenced by IP address.
ProxyBlock *
blocks connections to all sites.
ProxyReceiveBufferSize directive
Syntax: ProxyReceiveBufferSize bytes
Default: None
Context: server config, virtual host
Override: Not applicable
Status: Base
Module: mod_proxy
Compatibility: ProxyReceiveBufferSize is only available in
Apache 1.3 and later.
ProxyReceiveBufferSize 2048
ProxyMaxForwards directive
Syntax: ProxyMaxForwards bytes
Default: 10
Context: server config, virtual host
Override: Not applicable
Status: Base
Module: mod_proxy
Compatibility: ProxyMaxForwards is only available in
Apache 2.0 and later.
ProxyMaxForwards 10
NoProxy directive
Syntax: NoProxy
Domain|SubNet|IpAddr|Hostname
[Domain|SubNet|IpAddr|Hostname] ...
Default: None
Context: server config, virtual host
Override: Not applicable
Status: Base
Module: mod_proxy
Compatibility: NoProxy is only available in
Apache 1.3 and later.
ProxyRemote * http://firewall.mycompany.com:81
NoProxy .mycompany.com 192.168.112.0/21
The arguments to the NoProxy directive are one of the following type list:
Examples: .com .apache.org.
To distinguish Domains from Hostnames (both
syntactically and semantically; a DNS domain can have a DNS A record,
too!), Domains are always written
with a leading period.
Note: Domain name comparisons are done without regard to the case,
and Domains are always assumed to be anchored in the root
of the DNS tree, therefore two domains .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.
Examples:
As a degenerate case, a SubNet with 32 valid bits is the
equivalent to an IPAddr, while a SubNet with zero
valid bits (e.g., 0.0.0.0/0) is the same as the constant
_Default_, matching any IP address.
Example: 192.168.123.7
Note: An IPAddr does not need to be resolved by the DNS
system, so it can result in more effective apache performance.
Examples: prep.ai.mit.edu
www.apache.org.
Note: In many situations, it is more effective to specify an
IPAddr in place of a
Hostname since a DNS lookup
can be avoided. Name resolution in Apache can take a remarkable deal
of time when the connection to the name server uses a slow PPP
link.
Note: Hostname comparisons are done without regard to the case,
and Hostnames are always assumed to be anchored in the root
of the DNS tree, therefore two hosts WWW.MyDomain.com
and www.mydomain.com. (note the trailing period) are
considered equal.
ProxyDomain directive
Syntax: ProxyDomain Domain
Default: None
Context: server config, virtual host
Override: Not applicable
Status: Base
Module: mod_proxy
Compatibility: ProxyDomain is only available in
Apache 1.3 and later.
ProxyRemote * http://firewall.mycompany.com:81
NoProxy .mycompany.com 192.168.112.0/21
ProxyDomain .mycompany.com
ProxyVia directive
Syntax: ProxyVia on|off|full|block
Default: ProxyVia off
Context: server config, virtual host
Override: Not applicable
Status: Base
Module: mod_proxy
Compatibility: ProxyVia is only available in
Apache 1.3.2 and later.
ProxyErrorOverride directive
Syntax: ProxyErrorOverrideon
Default: off
Context: server config, virtual host
Override: Not applicable
Status: Base
Module: mod_proxy
Compatibility: ProxyErrorOverride
Apache 2.0 and later.