Add support for the RFC 7239 Forwarded header

[Ben Stähli]

As seen here ​https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Forwarded the Forwarded header seems to become the new and standardized way to define the forwarded ip/protocol when using a proxy. And to superseed the existing (well established) X-Forwarded-For/Proto/Protocol/etc headers.

A quick glimpse in into the code looks like currently there is still the "legacy" approach used. Are there any plans to use the new header?

[Claude Paroz]

Can you tell us a bit more about the current adoption state of this header?

[Ben Stähli]

Not really. But it would be a good thing to go ahead and support it, otherwise it will never be adopted. Also, it is an RFC, so I guess it will probably become the new standard. Tomorrow, or in some years only, who knows.

A quick research shows that some frameworks are discussing it.

• ​https://duckduckgo.com/?q=is+RFC-7239+forwarded+support&t=canonical&ia=web
• ​https://github.com/aspnet/AspNetCore/issues/5978
• ​https://issues.jboss.org/browse/UNDERTOW-1207?_sscc=t
• ​http://tomcat.10.x6.nabble.com/Bug-63080-New-Support-rfc7239-Forwarded-header-td5081951.html
• ​https://groups.google.com/forum/#!msg/golang-nuts/wc45kx0bsr8/BX1Dds8cAwAJ

[Carlton Gibson]

I'm tempted to say needsinfo here, but, yes there's the RFC so I guess we should pick it up at some point.

A case insenstive search for x[-_]forwarded doesn't turn up too many results, so in theory it's easy enough... but we'd need to think about supporting both approaches, probably indefinitely, and provide decent documentation around that, and a migration to the new header from the old (ones).

I'd like to see some detail on all that before we say "Yes, let's go! Accepted". As such we'll call it Someday/Maybe for now. (Happy to see more detail and/or an adjustment if someone wants to push it forward.)

[Santiago Basulto]

I'd be tempted to take over this. I'd like to know what would "add support" involves. Is it just trusting hosts based on X-Forwarded as we do with [x-forwarded-host](​https://docs.djangoproject.com/en/3.0/ref/settings/#use-x-forwarded-host)?

[Ben Stähli]

add support means all aspects of the new header need to be covered. as far as I can see, this touches at least these settings/aspects:

• SECURE_PROXY_SSL_HEADER ​https://docs.djangoproject.com/en/3.0/ref/settings/#secure-proxy-ssl-header
• USE_X_FORWARDED_HOST ​https://docs.djangoproject.com/en/3.0/ref/settings/#use-x-forwarded-host
• USE_X_FORWARDED_PORT ​https://docs.djangoproject.com/en/3.0/ref/settings/#use-x-forwarded-port

and, the parsing and security part is not to underestimate, as it's only one header, that must be parsed.

Replying to Santiago Basulto:

I'd be tempted to take over this. I'd like to know what would "add support" involves. Is it just trusting hosts based on X-Forwarded as we do with ​x-forwarded-host?