realip for Caddy v2

This repo is a port of captncraig's "realip" module to Caddy v2. See original plugin below:

https://github.com/captncraig/caddy-realip

UPDATE 04/06/2023

Upon upcoming release of Caddy 2.7 this plugin should no longer be required. See discussion at this link.

IMPORTANT

Effective as of Caddy 2.5.x, this plugin no longer works. See the following thread for additional information on the specifics: https://caddy.community/t/trouble-with-logging-changes/16408

If you want to continue using this plugin, do not upgrade your Caddy instance beyond 2.4.6.

Syntax

# tell caddy to process realip before other plugins
order realip first

realip {
    header name
    from cidr
    maxhops #
    strict
}

name is the name of the header containing the actual IP address. recommended value is "X-Forwarded-For".

cidr is the address range of expected proxy servers. As a security measure, IP headers are only accepted from known proxy servers. Must be a valid cidr block notation. This may be specified multiple times. cloudflare and cloudfront are currently supported.

maxhops specifies a limiting number of forwards if using "X-Forwarded-For" or similar headers as the identifier. Recommended value is 5.

strict, if specified, will reject requests from unkown proxy IPs with a 403 status. If not specified, it will simply leave the original IP in place.

Example

Simple usage to read X-Forwarded-For from cloudflare:

# tell caddy to process realip before other plugins
order realip first

realip {
  header "X-Forwarded-For"
  from cloudflare
  maxhops 5
}