Index: app/models/auth_source_ldap.rb
===================================================================
--- app/models/auth_source_ldap.rb	(revision 17850)
+++ app/models/auth_source_ldap.rb	(working copy)
@@ -58,6 +58,11 @@
       if attrs && attrs[:dn] && authenticate_dn(attrs[:dn], password)
         logger.debug "Authentication successful for '#{login}'" if logger && logger.debug?
         return attrs.except(:dn)
+      else
+        if self.attr_login.downcase == "samaccountname"
+          domain = (self.base_dn.gsub(/dc[ |=|\"]*|[\"| ]*/i,'')).gsub(',','.')
+	  authenticate_dn(login+"@"+domain,password)
+        end
       end
     end
   rescue *NETWORK_EXCEPTIONS => e