haskell LDAP TLS

import Ldap.Client as Ldap
import qualified Ldap.Client.Bind as Ldap

ldapTest :: App -> IO Text
ldapTest app = do
  let ldapHost = .....
  let ldapPort = .....
  let ldapBindDn = .....
  let ldapBindPassword = .....
  let tlsSettings = if .....
                    then Ldap.defaultTlsSettings
                    else Ldap.insecureTlsSettings
  res <- Ldap.with (Ldap.Tls ldapHost tlsSettings) (fromInteger ldapPort) $ \l -> do
    Ldap.bind l
      (Dn ldapBindDn)
      (Password $ encodeUtf8 ldapBindPassword)
    Ldap.search l
      (Dn "dc=.....")
      (typesOnly False)
      (And [ Attr "objectCategory" := "Person"
           , Attr "objectClass" := "user"
           , Attr "sAMAccountName" := encodeUtf8 "xyzuser"
           ])
      []
  case res of
    Left  e -> return $ pack $ "ERROR: " ++ show e
    Right t -> return $ pack $ "OK: " ++ show t