Fix rare race condition with missing ccache file

In some circumstances the ccache file may disappear while
mod_auth_gssapi still has a valid cookie and the client is performing a
json server call.

This may lead to credentials getting sourced from the keytab.
Make sure we enforce what GSS NAME we want to resolve so HTTP creds are
never mistakenly sourced.

Ticket: #6972

Signed-off-by: Simo Sorce <simo@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

ipaserver/rpcserver.py

@@ -777,8 +777,17 @@ class jsonserver_session(jsonserver, KerberosSession):
             self.debug('no ccache, need login')
             return self.need_login(start_response)
 
+        # If we have a ccache, make sure we have a GSS_NAME and use
+        # it to resolve the ccache name (Issue: 6972 )
+        principal = environ.get('GSS_NAME')
+        if principal is None:
+            self.debug('no GSS Name, need login')
+            return self.need_login(start_response)
+        gss_name = gssapi.Name(principal, gssapi.NameType.kerberos_principal)
+
         # Redirect to login if Kerberos credentials are expired
-        creds = get_credentials_if_valid(ccache_name=ccache_name)
+        creds = get_credentials_if_valid(name=gss_name,
+                                         ccache_name=ccache_name)
         if not creds:
             self.debug('ccache expired, deleting session, need login')
             # The request is finished with the ccache, destroy it.