squid proxy login after freeradius login ( like SSO)

Hi, I'm using FreeRADIUS Version 2.2.5. I use ttls/chap for authentification. Users must use login/password to authentificate. After freeradius validation, they have to authentificate against proxy squid. freeradius and squid proxy are using the same database for authentification. now I would like to do SSO. In other word, when I user authentificate against freeradius, freeradius must request the squid proxy for user authentification for web browsing. can you help me ? thank you sande7kouata@gmail.com