How to log in to UCWA using a passive grant type?

I have account in Skype for Bussiness with user@domain access. My first request to lyncdiscover receive to me a json answer

GET http://ift.tt/1N0YaJQ

{
  "_links": {
    "self": {
      "href": "http://ift.tt/1Gh3a5m"
    },
    "user": {
      "href": "http://ift.tt/1N0YaJU"
    },
    "xframe": {
      "href": "http://ift.tt/1Gh3b9p"
    }
  }
}

In next do request to user link

GET http://ift.tt/1N0YaJU

Answer:
Cache-Control → no-cache
Content-Length → 1293
Content-Type → text/html
Date → Fri, 02 Oct 2015 12:47:08 GMT
WWW-Authenticate → Bearer 
trusted_issuers="00000001-0000-0000-c000-000000000000@*", 
client_id="00000004-0000-0ff1-ce00-000000000000", 
authorization_uri="http://ift.tt/1nLu7IU", 
MsRtcOAuth 
href="http://ift.tt/1Gh3a5q",
grant_type="urn:microsoft.rtc:passive,urn:microsoft.rtc:anonmeeting"
X-Content-Type-Options → nosniff
X-MS-Correlation-Id → 2147515548
X-MS-Server-Fqdn → AMS1E01EDG04.infra.lync.com
client-request-id → eb37ab92-78a7-4f47-bc79-2d1fcad90b99

Server return only urn:microsoft.rtc:passive and urn:microsoft.rtc:anonmeeting, not password.

Ok, i,m try to do this use urn:microsoft.rtc:passive:

POST http://ift.tt/1Gh3a5q

grant_type=urn:microsoft.rtc:passive

Answer:
Content-Length → 1293
Content-Type → text/html
Date → Fri, 02 Oct 2015 13:05:11 GMT
X-Content-Type-Options → nosniff
X-MS-Correlation-Id → 2147515642
X-MS-Server-Fqdn → AMS1E01EDG02.infra.lync.com
X-Ms-diagnostics → 
28048;source="AMS1E01EDG02.infra.lync.com";
reason="The user is not signed in with WS Federation Passive credentials."
client-request-id → b4a39398-0089-44f6-bdfb-768902f7289d

Answer body:
401 - Unauthorized: Access is denied due to invalid credentials. 
You do not have permission to view this directory or page using the 
credentials that you supplied

The user is not signed in with WS Federation Passive credentials. How to get this credentials?