How to handle challenge response using PAM auth in FreeRadius

Rajendra Hegde Rajendra.hegde at
Mon Mar 15 17:16:48 CET 2010

I am developing a PAM module for radius server. 
The radius server is configured to use PAM auth.
It reads /etc/pam.d/radiusd and loads it on receiving auth request.
The PAM module talks to external Authentication server and sometimes gets back  "Challenge Respose".
How can this be returned back to radius server from  pam_sm_authenticate from  my PAM module ?
Please note that this is different than what pam_radius_auth.c does. 
pam_radius_auth.c talks to radius directly via network
where as my module directly gets loaded by Radius.
Why should not there be a way to return "Challenge Respose" 
from linux PAM back to it's loader ?
Can this possible linux limitation be overcome by radius calling another exported  function for 
PAM module covering all scenarios including "Challenge Response" ?
Where should I look into in the freeradius codebase, if I were to
add that functionality ?
with best regards,

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