From 79f6cb20e52082e3bb28b713f221a69f93cdb32e Mon Sep 17 00:00:00 2001
From: Romain Tartiere <romain.tartiere@gmail.com>
Date: Sat, 18 Dec 2010 01:45:38 +0000
Subject: [PATCH] Update CMAC code to handle 64 and 128 bit keys.

---
 libfreefare/freefare_internal.h           |  4 +--
 libfreefare/mifare_desfire_authenticate.c | 40 +++++++++++++----------
 test/test_mifare_desfire_aes.c            |  4 +--
 3 files changed, 26 insertions(+), 22 deletions(-)

diff --git a/libfreefare/freefare_internal.h b/libfreefare/freefare_internal.h
index 0296c1d..b1b2f90 100644
--- a/libfreefare/freefare_internal.h
+++ b/libfreefare/freefare_internal.h
@@ -209,8 +209,8 @@ struct mifare_desfire_key {
     } type;
     DES_key_schedule ks1;
     DES_key_schedule ks2;
-    uint8_t aes_sk1[16];
-    uint8_t aes_sk2[16];
+    uint8_t cmac_sk1[16];
+    uint8_t cmac_sk2[16];
     uint8_t aes_version;
 };
 
diff --git a/libfreefare/mifare_desfire_authenticate.c b/libfreefare/mifare_desfire_authenticate.c
index dc32790..271c1e3 100644
--- a/libfreefare/mifare_desfire_authenticate.c
+++ b/libfreefare/mifare_desfire_authenticate.c
@@ -105,54 +105,58 @@ lsl (uint8_t *data, size_t len)
 void
 cmac_generate_subkeys (MifareDESFireKey key)
 {
-    uint8_t l[16];
-    bzero (l, 16);
+    int kbs = key_block_size (key);
+    uint8_t R = (kbs == 8) ? 0x1B : 0x87;
 
-    uint8_t ivect[16];
-    bzero (ivect, 16);
+    uint8_t l[kbs];
+    bzero (l, kbs);
 
-    mifare_cbc_des (key, ivect, l, 16, MD_RECEIVE, 1);
+    uint8_t ivect[kbs];
+    bzero (ivect, kbs);
+
+    mifare_cbc_des (key, ivect, l, kbs, MD_RECEIVE, 1);
 
     bool xor = false;
 
     // Used to compute CMAC on complete blocks
-    memcpy (key->aes_sk1, l, 16);
+    memcpy (key->cmac_sk1, l, kbs);
     xor = l[0] & 0x80;
-    lsl (key->aes_sk1, 16);
+    lsl (key->cmac_sk1, kbs);
     if (xor)
-	key->aes_sk1[15] ^= 0x87;
+	key->cmac_sk1[kbs-1] ^= R;
 
     // Used to compute CMAC on the last block if non-complete
-    memcpy (key->aes_sk2, key->aes_sk1, 16);
-    xor = key->aes_sk1[0] & 0x80;
-    lsl (key->aes_sk2, 16);
+    memcpy (key->cmac_sk2, key->cmac_sk1, kbs);
+    xor = key->cmac_sk1[0] & 0x80;
+    lsl (key->cmac_sk2, kbs);
     if (xor)
-	key->aes_sk2[15] ^= 0x87;
+	key->cmac_sk2[kbs-1] ^= R;
 }
 
 void
 cmac (const MifareDESFireKey key, uint8_t *ivect, const uint8_t *data, size_t len, uint8_t *cmac)
 {
-    uint8_t *buffer = malloc (padded_data_length (len, key_block_size (key)));
+    int kbs = key_block_size (key);
+    uint8_t *buffer = malloc (padded_data_length (len, kbs));
 
     if (!buffer)
 	abort();
 
     memcpy (buffer, data, len);
 
-    if ((!len) || (len % 16)) {
+    if ((!len) || (len % kbs)) {
 	buffer[len++] = 0x80;
-	while (len % 16) {
+	while (len % kbs) {
 	    buffer[len++] = 0x00;
 	}
-	xor (key->aes_sk2, buffer + len - 16, 16);
+	xor (key->cmac_sk2, buffer + len - kbs, kbs);
     } else {
-	xor (key->aes_sk1, buffer + len - 16, 16);
+	xor (key->cmac_sk1, buffer + len - kbs, kbs);
     }
 
     mifare_cbc_des (key, ivect, buffer, len, MD_SEND, 1);
 
-    memcpy (cmac, ivect, 16);
+    memcpy (cmac, ivect, kbs);
 
     free (buffer);
 }
diff --git a/test/test_mifare_desfire_aes.c b/test/test_mifare_desfire_aes.c
index 90efda7..3fdcdcb 100644
--- a/test/test_mifare_desfire_aes.c
+++ b/test/test_mifare_desfire_aes.c
@@ -59,8 +59,8 @@ test_mifare_desfire_aes_generate_subkeys (void)
     MifareDESFireKey key = mifare_desfire_aes_key_new (key_data);
     cmac_generate_subkeys (key);
 
-    cut_assert_equal_memory (sk1, 16, key->aes_sk1, 16, cut_message ("Wrong sub-key 1"));
-    cut_assert_equal_memory (sk2, 16, key->aes_sk2, 16, cut_message ("Wrong sub-key 2"));
+    cut_assert_equal_memory (sk1, 16, key->cmac_sk1, 16, cut_message ("Wrong sub-key 1"));
+    cut_assert_equal_memory (sk2, 16, key->cmac_sk2, 16, cut_message ("Wrong sub-key 2"));
 
     mifare_desfire_key_free (key);
 }