p7: forwarding Proxy-*

Mark Nottingham <mnot@mnot.net> Tue, 30 April 2013 01:40 UTC

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From: Mark Nottingham <mnot@mnot.net>
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Subject: p7: forwarding Proxy-*
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(editorial) 

p7 4.2 says:
 
> Unlike WWW-Authenticate, the Proxy-Authenticate header field applies only to the current connection, and intermediaries should not forward it to downstream clients. However, an intermediate proxy might need to obtain its own credentials by requesting them from the downstream client, which in some circumstances will appear as if the proxy is forwarding the Proxy-Authenticate header field.

and 4.3 says:

> Unlike Authorization, the Proxy-Authorization header field applies only to the next outbound proxy that demanded authentication using the Proxy-Authenticate field. When multiple proxies are used in a chain, the Proxy-Authorization header field is consumed by the first outbound proxy that was expecting to receive credentials. A proxy may relay the credentials from the client request to the next proxy if that is the mechanism by which the proxies cooperatively authenticate a given request.


However, neither says that the header needs to be listed in the Connection header; i.e. that it's hop-by-hop, as per RFC2616 13.5.1. If you recall, we removed the explicit list of hop-by-hop headers, opting to say that they needed to be listed in Connection, because doing so was causing confusion. However, we haven't actually specified that for these two headers.

Recommend language like this:

"""
Unlike WWW-Authenticate, the Proxy-Authenticate header field applies only to the current connection, and thus MUST be listed in the Connection header field [ref], so that it is consumed on the next hop. Note that an intermediate proxy might need to obtain its own credentials by requesting them from the downstream client, which in some circumstances will appear as if the proxy is forwarding the Proxy-Authenticate header field.
"""


--
Mark Nottingham   http://www.mnot.net/