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When you enable the proxy option, you opt into a more strict set of host checks. This is necessary because leaving the backend open to remote hosts makes your computer vulnerable to DNS rebinding attacks. The issue is explained in this article and this issue.


Unlike the previous example, the value of this inside proxy.set(...) will be not proxy, but the original map. So when the internal implementation of set tries to access this.[[MapData]] internal slot, it succeeds.

mod_proxy and related modules implement a proxy/gateway for Apache HTTP Server, supporting a number of popular protocols as well as several different load balancing algorithms. Third-party modules can add support for additional protocols and load balancing algorithms.

An ordinary forward proxy is an intermediate server that sits between the client and the origin server. In order to get content from the origin server, the client sends a request to the proxy naming the origin server as the target. The proxy then requests the content from the origin server and returns it to the client. The client must be specially configured to use the forward proxy to access other sites.

A typical usage of a forward proxy is to provide Internet access to internal clients that are otherwise restricted by a firewall. The forward proxy can also use caching (as provided by mod_cache) to reduce network usage.

The forward proxy is activated using the ProxyRequests directive. Because forward proxies allow clients to access arbitrary sites through your server and to hide their true origin, it is essential that you secure your server so that only authorized clients can access the proxy before activating a forward proxy.

A reverse proxy (or gateway), by contrast, appears to the client just like an ordinary web server. No special configuration on the client is necessary. The client makes ordinary requests for content in the namespace of the reverse proxy. The reverse proxy then decides where to send those requests and returns the content as if it were itself the origin.

A typical usage of a reverse proxy is to provide Internet users access to a server that is behind a firewall. Reverse proxies can also be used to balance load among several back-end servers or to provide caching for a slower back-end server. In addition, reverse proxies can be used simply to bring several servers into the same URL space.

A reverse proxy is activated using the ProxyPass directive or the [P] flag to the RewriteRule directive. It is not necessary to turn ProxyRequests on in order to configure a reverse proxy.

You can also force a request to be handled as a reverse-proxy request, by creating a suitable Handler pass-through. The example configuration below will pass all requests for PHP scripts to the specified FastCGI server using reverse proxy:

The proxy manages the configuration of origin servers and their communication parameters in objects called workers. There are two built-in workers: the default forward proxy worker and the default reverse proxy worker. Additional workers can be configured explicitly.

Using explicitly configured workers in the forward mode is not very common, because forward proxies usually communicate with many different origin servers. Creating explicit workers for some of the origin servers can still be useful if they are used very often. Explicitly configured workers have no concept of forward or reverse proxying by themselves. They encapsulate a common concept of communication with origin servers. A worker created by ProxyPass for use in a reverse proxy will also be used for forward proxy requests whenever the URL to the origin server matches the worker URL, and vice versa.

Strictly limiting access is essential if you are using a forward proxy (using the ProxyRequests directive). Otherwise, your server can be used by any client to access arbitrary hosts while hiding his or her true identity. This is dangerous both for your network and for the Internet at large. When using a reverse proxy (using the ProxyPass directive with ProxyRequests Off), access control is less critical because clients can only contact the hosts that you have specifically configured.

An Apache httpd proxy server situated in an intranet needs to forward external requests through the company's firewall (for this, configure the ProxyRemote directive to forward the respective scheme to the firewall proxy). 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 " " instead of 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 httpd 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.

For circumstances where mod_proxy is sending requests to an origin server that doesn't properly implement keepalives or HTTP/1.1, there are two environment variables that can force the request to use HTTP/1.0 with no keepalive. These are set via the SetEnv directive.

In 2.4.26 and later, the "no-proxy" environment variable can be set to disable mod_proxy processing the current request. This variable should be set with SetEnvIf, as SetEnv is not evaluated early enough.

Some request methods such as POST include a request body. The HTTP protocol requires that requests which include a body either use chunked transfer encoding or send a Content-Length request header. When passing these requests on to the origin server, mod_proxy_http will always attempt to send the Content-Length. But if the body is large and the original request used chunked encoding, then chunked encoding may also be used in the upstream request. You can control this selection using environment variables. Setting proxy-sendcl ensures maximum compatibility with upstream servers by always sending the Content-Length, while setting proxy-sendchunked minimizes resource usage by using chunked encoding.

This directive is only useful for Apache httpd 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).

This directive determines whether the proxy should forward 100-continue Expect:ation to the origin server and thus let it decide when/if the HTTP request body should be read, or when Off the proxy should generate 100 Continue intermediate response by itself before forwarding the request body.

The ProxyBadHeader directive determines the behavior of mod_proxy if it receives syntactically invalid response header lines (i.e. containing no colon) from the origin server. The following arguments are possible:

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. That may slow down the startup time of the server.

This directive is only useful for Apache httpd 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.

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.)

The ProxyMaxForwards directive specifies the maximum number of proxies through which a request may pass if there's no Max-Forwards header supplied with the request. This may be set to prevent infinite proxy loops or a DoS attack.

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. The local server is often called a reverse proxy or gateway. The path is the name of a local virtual path; url is a partial URL for the remote server and cannot include a query string.

In 2.4.7 and later, support for using a Unix Domain Socket is available by using a target which prepends unix:/path/lis.sock. For example, to proxy HTTP and target the UDS at /home/www.socket, you would use unix:/home/www.socket

Exclusions must come before the general ProxyPass directives. In 2.4.26 and later, the "no-proxy" environment variable is an alternative to exclusions, and is the only way to configure an exclusion of a ProxyPass directive in Location context. This variable should be set with SetEnvIf, as SetEnv is not evaluated early enough.

In Apache HTTP Server 2.1 and later, mod_proxy supports pooled connections to a backend server. Connections created on demand can be retained in a pool for future use. Limits on the pool size and other settings can be coded on the ProxyPass directive using key=value parameters, described in the tables below.

By default, mod_proxy will allow and retain the maximum number of connections that could be used simultaneously by that web server child process. Use the max parameter to reduce the number from the default. The pool of connections is maintained per web server child process, and max and other settings are not coordinated among all child processes, except when only one child process is allowed by configuration or MPM design. 041b061a72

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