IE 5.x's automatic configuration script issues

[William Moore]

Hoping someone may have some insight on this. We have some resources offered
to the students and staff that are restricted by IP address. As some of the
students and staff work from home, we have setup a proxy server that they
can use to gain access to these resources. The server of course prompts them
for a login id and password before allowing them to use it.

Specifically we have two sets of documents that are IP restricted, one set
is for resources not maintained on our network (external links) and the
other is for resources within our network. An automatic proxy configuration
script had been created which performs two checks on a url to determine if
the proxy server is needed or not. The one test checks the host value to see
if it is one of the external sites which will require the proxy server, if
it fails that test it then checks to see if the url contains a specific file
or path and if it does then tells the browser to use the proxy server. If it
fails both tests it tells the browser to connect directly and not through
the proxy.

In all browsers the host check works flawlessly, however the url check only
works correctly in Netscape and IE 4.x. For IE 5 and later it would appear
that the browsers caches the response from the script for the given host
value and not the url. (perhaps an example shall help)

Given the following function in the proxy.pac file:
function FindProxyForURL(url, host)
{
  if (shExpMatch(url, "*webspirs.cgi*")) {
    return 'PROXY proxy:5555';
  } else {
    return 'DIRECT';
  }
}

1. In IE 5.x if you go to http://www.umanitoba.ca the script will check the
url and not find webspirs.cgi in the path. It will fail on the test and tell
the browser to connect directly. (which is correct of course)
2. If you then go to
http://www.umanitoba.ca/cgi-bin/libraries/ws/webspirs.cgi IE 5.x does not
use the proxy although it should as it contains webspirs.cgi in the url

Now if you were to go to
http://www.umanitoba.ca/cgi-bin/libraries/ws/webspirs.cgi first, the script
will find webspirs.cgi, direct you to the proxy and ask for an id and
password. If you then go to http://www.umanitoba.ca the browser will still
use the proxy server even though it is not required.

Now the questions I have are:
1. Has anyone encountered this as well?
2. Is there a possible fix for this, within the realms of the proxy.pac
config file?
3. Are there any good sites for proxy script creation? (I've been to the
Netscape and Microsoft one)

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    William Moore                          mailto:william_moore at umanitoba.ca
    LETS Web Developer                                        (204) 474-6523
                  http://www.umanitoba.ca/libraries/units/lets
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