session {add|delete} ssl question

 
 rule c_cert_session { 
 when RULE_INIT { 
   set ::key [AES::key 128] 
   log local0. "the key is:  $::key" 
 } 
  
 when CLIENTSSL_CLIENTCERT { 
  session add ssl [SSL::sessionid] [X509::verify_cert_error_string [SSL::verify_result]] 180 
 } 
  
 when HTTP_REQUEST { 
   set id [SSL::sessionid] 
   set y [session lookup ssl $id] 
   if { $y ne "" } { 
     set z [b64encode [AES::encrypt $::key $y]] 
     log local0.  "z is:  $z" 
     session delete ssl $id 
   } elseif { [HTTP::cookie exists ClientZ]} { 
     HTTP::header insert ClientCert  [AES::decrypt $::key [b64decode [HTTP::cookie ClientZ]]] 
     log local0.  "Inserting HTTP header ClientCert:   [AES::decrypt $::key [b64decode [HTTP::cookie ClientZ]]]" 
   } else { 
     set z [b64encode [AES::encrypt $::key none]] 
     log local0.  "no session, no cookie.  z is:  $z" 
   } 
 } 
  
 when HTTP_RESPONSE { 
   if { [info exists z ]} { 
     log local0.  "in http response Z is: $z" 
     HTTP::header insert "Set-Cookie ClientZ=$z" 
   } 
  } 
 }