class HTTPClient::ProxyAuth

SSPINegotiateAuth requires ‘win32/sspi’ module.
NegotiateAuth requires ‘ruby/ntlm’ module.
and delegates some operations to it.
ProxyAuth has sub filters (BasicAuth, NegotiateAuth, and SSPINegotiateAuth)
traps HTTP request header for inserting necessary authentication header.
It traps HTTP response header and maintains authentication state, and
Authentication filter is implemented using request filter of HTTPClient.
generates ‘Proxy-Authorization’ header in request.
Proxy server. Parses ‘Proxy-Authentication’ header in response and
Authentication filter for handling authentication negotiation between

def filter_request(req)

'Proxy-Authorization' header if needed.
Filter API implementation. Traps HTTP request and insert 
def filter_request(req)
  @authenticator.each do |auth|
    next unless auth.set? # hasn't be set, don't use it
    if cred = auth.get(req)
      if cred == :skip
        # some authenticator (NTLM and Negotiate) does not
        # need to send extra header after authorization. In such case
        # it should block other authenticators to respond and :skip is
        # the marker for such case.
        return
      end
      req.header.set('Proxy-Authorization', auth.scheme + " " + cred)
      return
    end
  end
end

def filter_response(req, res)

'Proxy-Authenticate' header.
Filter API implementation. Traps HTTP response and parses 
def filter_response(req, res)
  command = nil
  if res.status == HTTP::Status::PROXY_AUTHENTICATE_REQUIRED
    if challenge = parse_authentication_header(res, 'proxy-authenticate')
      uri = req.header.request_uri
      challenge.each do |scheme, param_str|
        @authenticator.each do |auth|
          next unless auth.set? # hasn't be set, don't use it
          if scheme.downcase == auth.scheme.downcase
            challengeable = auth.challenge(uri, param_str)
            command = :retry if challengeable
          end
        end
      end
      # ignore unknown authentication scheme
    end
  end
  command
end

def initialize

Creates new ProxyAuth. 
def initialize
  @basic_auth = ProxyBasicAuth.new
  @negotiate_auth = NegotiateAuth.new
  @ntlm_auth = NegotiateAuth.new('NTLM')
  @sspi_negotiate_auth = SSPINegotiateAuth.new
  @digest_auth = ProxyDigestAuth.new
  # sort authenticators by priority
  @authenticator = [@negotiate_auth, @ntlm_auth, @sspi_negotiate_auth, @digest_auth, @basic_auth]
end

def reset_challenge

Resets challenge state. See sub filters for more details. 
def reset_challenge
  @authenticator.each do |auth|
    auth.reset_challenge
  end
end

def set_auth(user, passwd)

Set authentication credential. See sub filters for more details. 
def set_auth(user, passwd)
  @authenticator.each do |auth|
    auth.set(nil, user, passwd)
  end
  reset_challenge
end