/*-
* Copyright (C) 2010, Romain Tartiere.
*
* This program is free software: you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by the
* Free Software Foundation, either version 3 of the License, or (at your
* option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>
*
* $Id$
*/
/*
* This implementation was written based on information provided by the
* following documents:
*
* NIST Special Publication 800-38B
* Recommendation for Block Cipher Modes of Operation: The CMAC Mode for Authentication
* May 2005
*/
#include "desfire_crypto.h"
static void xor(const uint8_t *ivect, uint8_t *data, const size_t len);
static size_t key_macing_length(desfirekey_t key);
// iceman, see memxor inside string.c, dest/src swapped..
static void xor(const uint8_t *ivect, uint8_t *data, const size_t len) {
for (size_t i = 0; i < len; i++) {
data[i] ^= ivect[i];
}
}
void cmac_generate_subkeys(desfirekey_t key) {
int kbs = key_block_size(key);
const uint8_t R = (kbs == 8) ? 0x1B : 0x87;
uint8_t l[kbs];
memset(l, 0, kbs);
uint8_t ivect[kbs];
memset(ivect, 0, kbs);
mifare_cypher_blocks_chained(NULL, key, ivect, l, kbs, MCD_RECEIVE, MCO_ENCYPHER);
bool xor = false;
// Used to compute CMAC on complete blocks
memcpy(key->cmac_sk1, l, kbs);
xor = l[0] & 0x80;
lsl(key->cmac_sk1, kbs);
if (xor)
key->cmac_sk1[kbs - 1] ^= R;
// Used to compute CMAC on the last block if non-complete
memcpy(key->cmac_sk2, key->cmac_sk1, kbs);
xor = key->cmac_sk1[0] & 0x80;
lsl(key->cmac_sk2, kbs);
if (xor)
key->cmac_sk2[kbs - 1] ^= R;
}
void cmac(const desfirekey_t key, uint8_t *ivect, const uint8_t *data, size_t len, uint8_t *cmac) {
int kbs = key_block_size(key);
uint8_t *buffer = malloc(padded_data_length(len, kbs));
memcpy(buffer, data, len);
if ((!len) || (len % kbs)) {
buffer[len++] = 0x80;
while (len % kbs) {
buffer[len++] = 0x00;
}
xor(key->cmac_sk2, buffer + len - kbs, kbs);
} else {
xor(key->cmac_sk1, buffer + len - kbs, kbs);
}
mifare_cypher_blocks_chained(NULL, key, ivect, buffer, len, MCD_SEND, MCO_ENCYPHER);
memcpy(cmac, ivect, kbs);
free(buffer);
}
size_t key_block_size(const desfirekey_t key) {
if (key == NULL)
return 0;
size_t block_size = 8;
switch (key->type) {
case T_DES:
case T_3DES:
case T_3K3DES:
block_size = 8;
break;
case T_AES:
block_size = 16;
break;
}
return block_size;
}
/*
* Size of MACing produced with the key.
*/
static size_t key_macing_length(const desfirekey_t key) {
size_t mac_length = MAC_LENGTH;
switch (key->type) {
case T_DES:
case T_3DES:
mac_length = MAC_LENGTH;
break;
case T_3K3DES:
case T_AES:
mac_length = CMAC_LENGTH;
break;
}
return mac_length;
}
/*
* Size required to store nbytes of data in a buffer of size n*block_size.
*/
size_t padded_data_length(const size_t nbytes, const size_t block_size) {
if ((!nbytes) || (nbytes % block_size))
return ((nbytes / block_size) + 1) * block_size;
else
return nbytes;
}
/*
* Buffer size required to MAC nbytes of data
*/
size_t maced_data_length(const desfirekey_t key, const size_t nbytes) {
return nbytes + key_macing_length(key);
}
/*
* Buffer size required to encipher nbytes of data and a two bytes CRC.
*/
size_t enciphered_data_length(const desfiretag_t tag, const size_t nbytes, int communication_settings) {
size_t crc_length = 0;
if (!(communication_settings & NO_CRC)) {
switch (DESFIRE(tag)->authentication_scheme) {
case AS_LEGACY:
crc_length = 2;
break;
case AS_NEW:
crc_length = 4;
break;
}
}
size_t block_size = DESFIRE(tag)->session_key ? key_block_size(DESFIRE(tag)->session_key) : 1;
return padded_data_length(nbytes + crc_length, block_size);
}
void *mifare_cryto_preprocess_data(desfiretag_t tag, void *data, size_t *nbytes, size_t offset, int communication_settings) {
uint8_t *res = data;
uint8_t mac[4];
size_t edl;
bool append_mac = true;
desfirekey_t key = DESFIRE(tag)->session_key;
if (!key)
return data;
switch (communication_settings & MDCM_MASK) {
case MDCM_PLAIN:
if (AS_LEGACY == DESFIRE(tag)->authentication_scheme)
break;
/*
* When using new authentication methods, PLAIN data transmission from
* the PICC to the PCD are CMACed, so we have to maintain the
* cryptographic initialisation vector up-to-date to check data
* integrity later.
*
* The only difference with CMACed data transmission is that the CMAC
* is not apended to the data send by the PCD to the PICC.
*/
append_mac = false;
/* pass through */
case MDCM_MACED:
switch (DESFIRE(tag)->authentication_scheme) {
case AS_LEGACY:
if (!(communication_settings & MAC_COMMAND))
break;
/* pass through */
edl = padded_data_length(*nbytes - offset, key_block_size(DESFIRE(tag)->session_key)) + offset;
// Fill in the crypto buffer with data ...
memcpy(res, data, *nbytes);
// ... and 0 padding
memset(res + *nbytes, 0, edl - *nbytes);
mifare_cypher_blocks_chained(tag, NULL, NULL, res + offset, edl - offset, MCD_SEND, MCO_ENCYPHER);
memcpy(mac, res + edl - 8, 4);
// Copy again provided data (was overwritten by mifare_cypher_blocks_chained)
memcpy(res, data, *nbytes);
if (!(communication_settings & MAC_COMMAND))
break;
// Append MAC
size_t bla = maced_data_length(DESFIRE(tag)->session_key, *nbytes - offset) + offset;
bla++;
memcpy(res + *nbytes, mac, 4);
*nbytes += 4;
break;
case AS_NEW:
if (!(communication_settings & CMAC_COMMAND))
break;
cmac(key, DESFIRE(tag)->ivect, res, *nbytes, DESFIRE(tag)->cmac);
if (append_mac) {
size_t len = maced_data_length(key, *nbytes);
++len;
memcpy(res, data, *nbytes);
memcpy(res + *nbytes, DESFIRE(tag)->cmac, CMAC_LENGTH);
*nbytes += CMAC_LENGTH;
}
break;
}
break;
case MDCM_ENCIPHERED:
/* |<-------------- data -------------->|
* |<--- offset -->| |
* +---------------+--------------------+-----+---------+
* | CMD + HEADERS | DATA TO BE SECURED | CRC | PADDING |
* +---------------+--------------------+-----+---------+ ----------------
* | |<~~~~v~~~~~~~~~~~~~>| ^ | | (DES / 3DES)
* | | `---- crc16() ----' | |
* | | | ^ | | ----- *or* -----
* |<~~~~~~~~~~~~~~~~~~~~v~~~~~~~~~~~~~>| ^ | | (3K3DES / AES)
* | `---- crc32() ----' | |
* | | ---- *then* ----
* |<---------------------------------->|
* encypher()/decypher()
*/
if (!(communication_settings & ENC_COMMAND))
break;
edl = enciphered_data_length(tag, *nbytes - offset, communication_settings) + offset;
// Fill in the crypto buffer with data ...
memcpy(res, data, *nbytes);
if (!(communication_settings & NO_CRC)) {
// ... CRC ...
switch (DESFIRE(tag)->authentication_scheme) {
case AS_LEGACY:
AddCrc14A(res + offset, *nbytes - offset);
*nbytes += 2;
break;
case AS_NEW:
crc32_append(res, *nbytes);
*nbytes += 4;
break;
}
}
// ... and padding
memset(res + *nbytes, 0, edl - *nbytes);
*nbytes = edl;
mifare_cypher_blocks_chained(tag, NULL, NULL, res + offset, *nbytes - offset, MCD_SEND, (AS_NEW == DESFIRE(tag)->authentication_scheme) ? MCO_ENCYPHER : MCO_DECYPHER);
break;
default:
*nbytes = -1;
res = NULL;
break;
}
return res;
}
void *mifare_cryto_postprocess_data(desfiretag_t tag, void *data, size_t *nbytes, int communication_settings) {
void *res = data;
void *edata = NULL;
uint8_t first_cmac_byte = 0x00;
desfirekey_t key = DESFIRE(tag)->session_key;
if (!key)
return data;
// Return directly if we just have a status code.
if (1 == *nbytes)
return res;
switch (communication_settings & MDCM_MASK) {
case MDCM_PLAIN:
if (AS_LEGACY == DESFIRE(tag)->authentication_scheme)
break;
/* pass through */
case MDCM_MACED:
switch (DESFIRE(tag)->authentication_scheme) {
case AS_LEGACY:
if (communication_settings & MAC_VERIFY) {
*nbytes -= key_macing_length(key);
if (*nbytes == 0) {
*nbytes = -1;
res = NULL;
#ifdef WITH_DEBUG
Dbprintf("No room for MAC!");
#endif
break;
}
size_t edl = enciphered_data_length(tag, *nbytes - 1, communication_settings);
edata = malloc(edl);
memcpy(edata, data, *nbytes - 1);
memset((uint8_t *)edata + *nbytes - 1, 0, edl - *nbytes + 1);
mifare_cypher_blocks_chained(tag, NULL, NULL, edata, edl, MCD_SEND, MCO_ENCYPHER);
if (0 != memcmp((uint8_t *)data + *nbytes - 1, (uint8_t *)edata + edl - 8, 4)) {
#ifdef WITH_DEBUG
Dbprintf("MACing not verified");
hexdump((uint8_t *)data + *nbytes - 1, key_macing_length(key), "Expect ", 0);
hexdump((uint8_t *)edata + edl - 8, key_macing_length(key), "Actual ", 0);
#endif
DESFIRE(tag)->last_pcd_error = CRYPTO_ERROR;
*nbytes = -1;
res = NULL;
}
}
break;
case AS_NEW:
if (!(communication_settings & CMAC_COMMAND))
break;
if (communication_settings & CMAC_VERIFY) {
if (*nbytes < 9) {
*nbytes = -1;
res = NULL;
break;
}
first_cmac_byte = ((uint8_t *)data)[*nbytes - 9];
((uint8_t *)data)[*nbytes - 9] = ((uint8_t *)data)[*nbytes - 1];
}
int n = (communication_settings & CMAC_VERIFY) ? 8 : 0;
cmac(key, DESFIRE(tag)->ivect, ((uint8_t *)data), *nbytes - n, DESFIRE(tag)->cmac);
if (communication_settings & CMAC_VERIFY) {
((uint8_t *)data)[*nbytes - 9] = first_cmac_byte;
if (0 != memcmp(DESFIRE(tag)->cmac, (uint8_t *)data + *nbytes - 9, 8)) {
#ifdef WITH_DEBUG
Dbprintf("CMAC NOT verified :-(");
hexdump((uint8_t *)data + *nbytes - 9, 8, "Expect ", 0);
hexdump(DESFIRE(tag)->cmac, 8, "Actual ", 0);
#endif
DESFIRE(tag)->last_pcd_error = CRYPTO_ERROR;
*nbytes = -1;
res = NULL;
} else {
*nbytes -= 8;
}
}
break;
}
free(edata);
break;
case MDCM_ENCIPHERED:
(*nbytes)--;
bool verified = false;
int crc_pos = 0x00;
int end_crc_pos = 0x00;
uint8_t x;
/*
* AS_LEGACY:
* ,-----------------+-------------------------------+--------+
* \ BLOCK n-1 | BLOCK n | STATUS |
* / PAYLOAD | CRC0 | CRC1 | 0x80? | 0x000000000000 | 0x9100 |
* `-----------------+-------------------------------+--------+
*
* <------------ DATA ------------>
* FRAME = PAYLOAD + CRC(PAYLOAD) + PADDING
*
* AS_NEW:
* ,-------------------------------+-----------------------------------------------+--------+
* \ BLOCK n-1 | BLOCK n | STATUS |
* / PAYLOAD | CRC0 | CRC1 | CRC2 | CRC3 | 0x80? | 0x0000000000000000000000000000 | 0x9100 |
* `-------------------------------+-----------------------------------------------+--------+
* <----------------------------------- DATA ------------------------------------->|
*
* <----------------- DATA ---------------->
* FRAME = PAYLOAD + CRC(PAYLOAD + STATUS) + PADDING + STATUS
* `------------------'
*/
mifare_cypher_blocks_chained(tag, NULL, NULL, res, *nbytes, MCD_RECEIVE, MCO_DECYPHER);
/*
* Look for the CRC and ensure it is followed by NULL padding. We
* can't start by the end because the CRC is supposed to be 0 when
* verified, and accumulating 0's in it should not change it.
*/
switch (DESFIRE(tag)->authentication_scheme) {
case AS_LEGACY:
crc_pos = *nbytes - 8 - 1; // The CRC can be over two blocks
if (crc_pos < 0) {
/* Single block */
crc_pos = 0;
}
break;
case AS_NEW:
/* Move status between payload and CRC */
res = DESFIRE(tag)->crypto_buffer;
memcpy(res, data, *nbytes);
crc_pos = (*nbytes) - 16 - 3;
if (crc_pos < 0) {
/* Single block */
crc_pos = 0;
}
memcpy((uint8_t *)res + crc_pos + 1, (uint8_t *)res + crc_pos, *nbytes - crc_pos);
((uint8_t *)res)[crc_pos] = 0x00;
crc_pos++;
*nbytes += 1;
break;
}
do {
uint16_t crc_16 = 0x00;
uint32_t crc;
switch (DESFIRE(tag)->authentication_scheme) {
case AS_LEGACY:
AddCrc14A((uint8_t *)res, end_crc_pos);
end_crc_pos = crc_pos + 2;
//
crc = crc_16;
break;
case AS_NEW:
end_crc_pos = crc_pos + 4;
crc32_ex(res, end_crc_pos, (uint8_t *)&crc);
break;
}
if (!crc) {
verified = true;
for (int n = end_crc_pos; n < *nbytes - 1; n++) {
uint8_t byte = ((uint8_t *)res)[n];
if (!((0x00 == byte) || ((0x80 == byte) && (n == end_crc_pos))))
verified = false;
}
}
if (verified) {
*nbytes = crc_pos;
switch (DESFIRE(tag)->authentication_scheme) {
case AS_LEGACY:
((uint8_t *)data)[(*nbytes)++] = 0x00;
break;
case AS_NEW:
/* The status byte was already before the CRC */
break;
}
} else {
switch (DESFIRE(tag)->authentication_scheme) {
case AS_LEGACY:
break;
case AS_NEW:
x = ((uint8_t *)res)[crc_pos - 1];
((uint8_t *)res)[crc_pos - 1] = ((uint8_t *)res)[crc_pos];
((uint8_t *)res)[crc_pos] = x;
break;
}
crc_pos++;
}
} while (!verified && (end_crc_pos < *nbytes));
if (!verified) {
#ifdef WITH_DEBUG
/* FIXME In some configurations, the file is transmitted PLAIN */
Dbprintf("CRC not verified in decyphered stream");
#endif
DESFIRE(tag)->last_pcd_error = CRYPTO_ERROR;
*nbytes = -1;
res = NULL;
}
break;
default:
Dbprintf("Unknown communication settings");
*nbytes = -1;
res = NULL;
break;
}
return res;
}
void mifare_cypher_single_block(desfirekey_t key, uint8_t *data, uint8_t *ivect, MifareCryptoDirection direction, MifareCryptoOperation operation, size_t block_size) {
uint8_t ovect[MAX_CRYPTO_BLOCK_SIZE];
if (direction == MCD_SEND) {
xor(ivect, data, block_size);
} else {
memcpy(ovect, data, block_size);
}
uint8_t edata[MAX_CRYPTO_BLOCK_SIZE];
switch (key->type) {
case T_DES:
switch (operation) {
case MCO_ENCYPHER:
//DES_ecb_encrypt ((DES_cblock *) data, (DES_cblock *) edata, &(key->ks1), DES_ENCRYPT);
des_enc(edata, data, key->data);
break;
case MCO_DECYPHER:
//DES_ecb_encrypt ((DES_cblock *) data, (DES_cblock *) edata, &(key->ks1), DES_DECRYPT);
des_dec(edata, data, key->data);
break;
}
break;
case T_3DES:
switch (operation) {
case MCO_ENCYPHER:
// DES_ecb_encrypt ((DES_cblock *) data, (DES_cblock *) edata, &(key->ks1), DES_ENCRYPT);
// DES_ecb_encrypt ((DES_cblock *) edata, (DES_cblock *) data, &(key->ks2), DES_DECRYPT);
// DES_ecb_encrypt ((DES_cblock *) data, (DES_cblock *) edata, &(key->ks1), DES_ENCRYPT);
tdes_enc(edata, data, key->data);
break;
case MCO_DECYPHER:
// DES_ecb_encrypt ((DES_cblock *) data, (DES_cblock *) edata, &(key->ks1), DES_DECRYPT);
// DES_ecb_encrypt ((DES_cblock *) edata, (DES_cblock *) data, &(key->ks2), DES_ENCRYPT);
// DES_ecb_encrypt ((DES_cblock *) data, (DES_cblock *) edata, &(key->ks1), DES_DECRYPT);
tdes_dec(data, edata, key->data);
break;
}
break;
case T_3K3DES:
switch (operation) {
case MCO_ENCYPHER:
tdes_enc(edata, data, key->data);
// DES_ecb_encrypt ((DES_cblock *) data, (DES_cblock *) edata, &(key->ks1), DES_ENCRYPT);
// DES_ecb_encrypt ((DES_cblock *) edata, (DES_cblock *) data, &(key->ks2), DES_DECRYPT);
// DES_ecb_encrypt ((DES_cblock *) data, (DES_cblock *) edata, &(key->ks3), DES_ENCRYPT);
break;
case MCO_DECYPHER:
tdes_dec(data, edata, key->data);
// DES_ecb_encrypt ((DES_cblock *) data, (DES_cblock *) edata, &(key->ks3), DES_DECRYPT);
// DES_ecb_encrypt ((DES_cblock *) edata, (DES_cblock *) data, &(key->ks2), DES_ENCRYPT);
// DES_ecb_encrypt ((DES_cblock *) data, (DES_cblock *) edata, &(key->ks1), DES_DECRYPT);
break;
}
break;
case T_AES:
switch (operation) {
case MCO_ENCYPHER: {
mbedtls_aes_context ctx;
mbedtls_aes_init(&ctx);
mbedtls_aes_setkey_enc(&ctx, key->data, 128);
mbedtls_aes_crypt_cbc(&ctx, MBEDTLS_AES_ENCRYPT, sizeof(edata), ivect, data, edata);
mbedtls_aes_free(&ctx);
break;
}
case MCO_DECYPHER: {
mbedtls_aes_context ctx;
mbedtls_aes_init(&ctx);
mbedtls_aes_setkey_dec(&ctx, key->data, 128);
mbedtls_aes_crypt_cbc(&ctx, MBEDTLS_AES_DECRYPT, sizeof(edata), ivect, edata, data);
mbedtls_aes_free(&ctx);
break;
}
}
break;
}
memcpy(data, edata, block_size);
if (direction == MCD_SEND) {
memcpy(ivect, data, block_size);
} else {
xor(ivect, data, block_size);
memcpy(ivect, ovect, block_size);
}
}
/*
* This function performs all CBC cyphering / deciphering.
*
* The tag argument may be NULL, in which case both key and ivect shall be set.
* When using the tag session_key and ivect for processing data, these
* arguments should be set to NULL.
*
* Because the tag may contain additional data, one may need to call this
* function with tag, key and ivect defined.
*/
void mifare_cypher_blocks_chained(desfiretag_t tag, desfirekey_t key, uint8_t *ivect, uint8_t *data, size_t data_size, MifareCryptoDirection direction, MifareCryptoOperation operation) {
size_t block_size;
if (tag) {
if (!key)
key = DESFIRE(tag)->session_key;
if (!ivect)
ivect = DESFIRE(tag)->ivect;
switch (DESFIRE(tag)->authentication_scheme) {
case AS_LEGACY:
memset(ivect, 0, MAX_CRYPTO_BLOCK_SIZE);
break;
case AS_NEW:
break;
}
}
block_size = key_block_size(key);
size_t offset = 0;
while (offset < data_size) {
mifare_cypher_single_block(key, data + offset, ivect, direction, operation, block_size);
offset += block_size;
}
}