Proxy users can't authenticate at sharepoint site

[Guest]

[toonviso]

If the user uses the proxy they can't authenticate at the sharepoint site (port 56000).

I made the following setting:
Firewall- outgoing traffic allow tcp 56000
Proxy - transparant

Any idea what I did wrong?

[kashifmax]

First, enable the firewall/proxy log (logs are very helpful) and than make a outgoing rule with all ports and check the website with or without proxy. If it is working without proxy, than I think (don't know exactly which port sharepoint is using) add ssl port or safe port in squid.conf file...

[toonviso]

It works fine without the proxy...

It still not works after adding port 56000 in the http proxy configuration (allow ports and allowed ssl ports) and making an outgoing rule to allow all ports.
Somehow there must be some connection being established, because the popup for authentication appears. After entering the credentials, the popup keeps coming back (3x times), asking for the credentials.

I use the ntlm-authentication method in the http proxy, could this make a conflict with the authentication for the sharepoint site?

Proxylog:
43 127.0.0.1 TCP_MISS/401 1048 GET .be:56000/ - DIRECT/194.78.55.135 text/htmlWeb prox..2012-05-10 12:26:13
85 172.16.0.147 TCP_MISS/401 1248 GET .be:56000/ - FIRST_UP_PARENT/content3 text/htmlWeb prox..2012-05-10 12:26:13
49 127.0.0.1 TCP_MISS/401 462 GET .be:56000/ - DIRECT/194.78.55.135 -Web prox..2012-05-10 12:26:13
54 172.16.0.147 TCP_MISS/401 662 GET .be:56000/ - FIRST_UP_PARENT/content3 -
Firewalllog:
no remarks

[kashifmax]

I am not sure about the conflict but only I can say that the server configuration files may need some addition, if you are using NTLM Authentication method. Here are some links that might help.

http://wiki.squid-cache.org/ConfigExamples/Authenticate/Ntlm
http://www.cyberciti.biz/faq/squid-ntlm-authentication-configuration-howto/