mod_proxy/5891: Proxy'd server generated pages contain incorrect hostname in signature

[Ian Morgan <im...@webcon.net>]

>Number:         5891
>Category:       mod_proxy
>Synopsis:       Proxy'd server generated pages contain incorrect hostname in signature
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    apache
>State:          open
>Class:          sw-bug
>Submitter-Id:   apache
>Arrival-Date:   Wed Mar 15 21:40:00 PST 2000
>Closed-Date:
>Last-Modified:
>Originator:     imorgan@webcon.net
>Release:        1.3.12
>Organization:
apache
>Environment:
Linux light.webcon.net 2.2.14 #3 SMP Mon Mar 13 14:00:10 EST 2000 i686 unknown
egcs-1.1.2-24
mod_ssl-2.6.0-1.3.12

>Description:
Pages generated by the server during a proxy request (i.e. FTP through the
proxy server) have misleading information in the "ServerSignature" appended
to the page.

i.e. Browser-A connects to FTP-site-C via proxy-server-B. The page returned
contains the usual ftp directory output + proxy server signature:
Apache 1.3.12 Server at FTP-site-C Port 80

Even worse, if ServerSignature is set to "EMail", then the "FTP-site-C" is
linked to "mailto:ServerAdmin@proxy-server-B"!

Obviously the signature is wrong, it should be:
Apache 1.3.12 Server at proxy-server-B Port 80
>How-To-Repeat:
Connect to any FTP site via an Apache proxy server, while
UseCanonicalHostame is Off.
>Fix:
In function ap_psignature: use of ap_get_server_name(r) results in the
remote hostname rather than the local hostname (the proxy server).
It's related to "UseCanonicalHostname Off". Turning it On makes the
ServerSignature correct. This behaviour seems understandable based
on the purpose of UseCanonicalHostname, but causes extreme confusion since the
proxy server is reporting a completely wrong signature.
The ap_psignature needs to ALWAYS report the canonical hostname within
mod_proxy, and use ap_get_server_name everywhere else.
>Release-Note:
>Audit-Trail:
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