# Problem with port number in URLs via CERN httpd proxy server

owner-uri@bunyip.com
Sat, 17 Dec 1994 01:43:23 -0500

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    From: owner-uri@bunyip.com

    Date: Sat, 17 Dec 1994 01:43:23 -0500

    Message-Id: <199412170643.BAA25912@services.bunyip.com>

>From listmaster Fri Dec 16 21:37:31 1994
To: uri@bunyip.com
Subject: ftp URLs
Date: Fri, 16 Dec 1994 18:36:21 -0800
From: "Roy T. Fielding" <fielding@avron.ICS.UCI.EDU>
Sender: owner-uri@bunyip.com
Precedence: bulk

Since most people on this list don't subscribe to www-proxy, I thought
I'd forward this message here. I think it demonstrates the problem
of describing ftp as a sequence of CWD commands without also saying that
the client should first attempt RETR /full-path and only attempt the separate
CWD commands if the RETR fails.

In this case, the proxy is following the URL spec's behavior and failing,
but it works just fine with XMosaic.

......Roy Fielding ICS Grad Student, University of California, Irvine USA
<fielding@ics.uci.edu>
<URL:http://www.ics.uci.edu/dir/grad/Software/fielding>

------- Forwarded Message

Date: Fri, 16 Dec 1994 23:47:20 +0100
Message-Id: <9412162233.AA13092@godot.pa.dec.com>
Reply-To: steveg@pa.dec.com
Sender: www-proxy@www0.cern.ch
Precedence: bulk
From: steveg@pa.dec.com
To: Multiple recipients of list <www-proxy@www0.cern.ch>
Subject: proxies and FTP

We are having difficulties with our proxy when we try to get to
the url:
ftp://reports.adm.cs.cmu.edu/usr/anon/1994/CMU-CS-94-100.ps
or
ftp://reports.adm.cs.cmu.edu/%2fusr/anon/1994/CMU-CS-94-100.ps
or
ftp://reports.adm.cs.cmu.edu//usr/anon/1994/CMU-CS-94-100.ps

We are running a CERN 3.0 proxy on our external corporate firewall.

The problem occurs because "reports.adm.cs.cmu.edu" automatically
cd's to /usr/anon on anonymous ftp connections. A cd to "/usr/anon/1994"
succeeds but a "cwd /; cwd usr; cwd 1994;" style FTP command sequence
is forbidden for security reasons.

The URL - ftp://reports.adm.cs.cmu.edu/1994/CMU-CS-94-100.ps - does
work, but I doubt it works for non-proxied browsers.

So the questions are:

1) According to the URL spec
(http://ds.internic.net/internet-drafts/draft-ietf-uri-url-08.txt)
the second of the 3 methods given above should work. Does the request
fail because the proxy is going through a series of FTP "cwd" commands
rather than a single "cwd"?

2) Do "standard" browsers do the right thing with FTP requests?
i.e. does ftp://reports.adm.cs.cmu.edu/1994/CMU-CS-94-100.ps work
is you are not going through a firewall? Or do other browsers "cwd
/1994" rather than "cwd 1994" (as the spec claims?).

3) Is there some other way out of this mess?

Steve
steveg@pa.dec.com

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