[p2p-hackers] Automatic proxy detection / tunneling

[David Barrett]

What is the best method for a client to detect and use any web proxy 
that separates it from the Internet?

Under Win32 I see the functions "WinHttpGetProxyForUrl( )" and 
"WinHttpGetIEProxyConfigForCurrentUser( )" which help discover the 
proxy.  What I specifically don't see are:

1) What type of proxy do these functions return?  The return value 
contains a list in the form of:

	([<scheme>=][<scheme>"://"]<server>[":"<port>])

What is the range of possible "schemes"?  Will this be something like 
"socksv4" or "socksv5" or what?

2) If it's a SOCKSv5 proxy, how do I determine what kind of 
authentication method and credentials to use?

3) If it's not a SOCKS proxy, what kind is it?  The HTTP protocol RFC 
mentions proxies and gateways (like the Squid web-cache), but they are 
implied to be wholly transparent.  Am I wrong?  What other kind of 
proxies exist?

Basically, I want to tunnel out of restrictive enterprises that employ 
firewalls and web proxies.  But I'm not entirely sure what comprises 
these deployments.  Can you offer any hints to point me in the right 
direction?  Thanks!

-david




However, this is Win32-dependent code.  Do you know:

1) Is there a platform-independent library available that auto-detects 
web-proxies and executes any resulting PAC