Plug.RewriteOn (Plug v1.18.1)

A plug to rewrite the request's host/port/protocol from x-forwarded-* headers.

If your Plug application is behind a proxy that handles HTTPS, you may need to tell Plug to parse the proper protocol from the x-forwarded-* header.

plug Plug.RewriteOn, [:x_forwarded_host, :x_forwarded_port, :x_forwarded_proto]

The supported values are:

• :x_forwarded_for - to override the remote IP based on the "x-forwarded-for" header
• :x_forwarded_host - to override the host based on the "x-forwarded-host" header
• :x_forwarded_port - to override the port based on the "x-forwarded-port" header
• :x_forwarded_proto - to override the protocol based on the "x-forwarded-proto" header

Some HTTPS proxies use nonstandard headers, which can be specified in the list via tuples:

• {:remote_ip, header} - to override the remote IP based on a custom header
• {:host, header} - to override the host based on a custom header
• {:port, header} - to override the port based on a custom header
• {:scheme, header} - to override the protocol based on a custom header

A tuple representing a Module-Function-Args can also be given as argument instead of a list.

Since rewriting the scheme based on x-forwarded-* headers can open up security vulnerabilities, only use this plug if:

• your app is behind a proxy
• your proxy strips the given x-forwarded-* headers from all incoming requests
• your proxy sets the x-forwarded-* headers and sends it to Plug