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From Francois-Rene Rideau <f...@tunes.org>
Subject URI lossage with ProxyPass
Date Thu, 17 Jun 2004 09:44:38 GMT
Dear mod_proxy developers,

I have experienced quite some trouble due to design bugs in ProxyPass,
and have proposed a patch for apache 1.3.
The very same bugs are present in apache 2.0, and a similar fix could be used.

Can you tell me if you'll fix the official mod_proxy,
either using my patch or otherwise?

The bug symptoms are that
(1) when a request to a ProxyPass host contains %3A, the %3A is expanded
 to a colon, which yields an incorrect HTTP URL that confuses the remote host.
(2) when a request to a ProxyPass host contains %2F, apache rejects the
 request with a 404 without even contacting the remote host.

The bug causes are that
(1) function modules/proxy/mod_proxy.c:proxy_fixup() makes a misguided attempt
 at URI canonicalization. It should definitely not try to
 when using PROXY_PASS, and probably not in STD_PROXY mode either.
 Since I don't understand all the ins and outs, my patch only adds a bypass
 in the case of PROXY_PASS, but I believe the whole function should be
 scrapped altogether (whoever checks in the patch should ponder that).
(2) r->proxyreq=PROXY_PASS is declared too late, only in
 modules/proxy/mod_proxy.c:proxy_trans(), so that
 main/http_request.c:process_request_internal() already messed up
 with the URL, not realizing there is a proxy request going on.
 Consequently, the ProxyPass alias detection MUST happen not in
 modules/proxy/mod_proxy.c:proxy_trans() but in
 This may or may not interfere with funky rewrites that some people
 may want to do before or after a ProxyPass is used. Someone who understands
 such issues should step in and tell. Maybe my change introduces some
 subtle incompatibilities in *actually deployed* setups, but I would bet not,
 and some mechanism could be devised to restore proper behaviour
 for those who would need such a feature.

I hope my patch doesn't break any expected behaviour, but I can't be sure.
What I'm certain of is that ProxyPass is quite broken without my patch.
Please consider merging this patch into apache, and tell me when it's done.


[ François-René ÐVB Rideau | Reflection&Cybernethics | http://fare.tunes.org ]
[  TUNES project for a Free Reflective Computing System  | http://tunes.org  ]
The last good thing written in C was Franz Schubert's Symphony number 9.
        -- Erwin Dieterich <erwin@cvt12.verfahrenstechnik.uni-stuttgart.de>

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