From 48b161d67ccacd0e63c609d32c1b92b5d6c71c20 Mon Sep 17 00:00:00 2001
From: Romain Tartiere <romain.tartiere@gmail.com>
Date: Sat, 18 Dec 2010 01:32:56 +0000
Subject: [PATCH] Invalidate authentication when changing the currently used
 key.

---
 libfreefare/mifare_desfire.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/libfreefare/mifare_desfire.c b/libfreefare/mifare_desfire.c
index a312d3f..f42c69e 100644
--- a/libfreefare/mifare_desfire.c
+++ b/libfreefare/mifare_desfire.c
@@ -554,6 +554,15 @@ mifare_desfire_change_key (MifareTag tag, uint8_t key_no, MifareDESFireKey new_k
     ssize_t sn = __res_n;
     mifare_cryto_postprocess_data (tag, res, &sn, MDCM_PLAIN | CMAC_COMMAND | CMAC_VERIFY);
 
+    /*
+     * If we changed the current authenticated key, we are not authenticated
+     * anymore.
+     */
+    if (key_no == MIFARE_DESFIRE (tag)->authenticated_key_no) {
+	free (MIFARE_DESFIRE (tag)->session_key);
+	MIFARE_DESFIRE (tag)->session_key = NULL;
+    }
+
     return 0;
 }