Does STSClient support SignChallenge?

[Al Le]

Hello.

WS-Trust 1.4 spec allows the process of obtaining a security token to 
consist not only of two messages (request for token, response with the 
token), but also to have some intermediate requests and responses. In 
these intermediate requests and responses, the STS may challenge the 
token requestor to answer a challenge (e.g. to sign a randomly generated 
string). Only after all challenges have been aswered correctly, would 
the STS sent a real token. See e.g. chapter 8.2 (Signature Challenges) 
of the WS-Trust spec.

Does the CXF's STSClient support such a protocol? I.e. can it response 
to the challenges? If yes, how should it be configured to do so?

Thank you!

AL