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Update CMAC code to handle 64 and 128 bit keys.

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This commit is contained in:
Romain Tartiere 2010-12-18 01:45:38 +00:00
parent 8d74401e87
commit 79f6cb20e5
3 changed files with 26 additions and 22 deletions
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4
libfreefare/freefare_internal.h
View file

@ -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;
};

40
libfreefare/mifare_desfire_authenticate.c
View file

@ -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);
}

4
test/test_mifare_desfire_aes.c
View file

@ -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);
}