No support for an upstream proxy that uses NTLM authentication

Many corporate/enterprise environments still have proxies that use NTLM authentication also sometimes referred to as the NT challenge/response (NTCR) scheme. As far as I can tell, this is old Microsoft products that just refuse to die.

The following document explains the protocol:

https://www.innovation.ch/personal/ronald/ntlm.html

There does appear to be a C library implementing the protocol at:

http://cntlm.sourceforge.net/

There is also a Python 1.x implementation at:

http://ntlmaps.sourceforge.net/