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Enhance the mifare_cryto_postprocess_data() function.

Browse source 
Update issue 52
Both code snippets are now similar and it should be possible to merge them
together.
This commit is contained in:
Romain Tartiere 2011-04-23 15:17:11 +00:00
parent 1c7b7dcbe4
commit 52e1c90425
1 changed files with 58 additions and 31 deletions
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89
libfreefare/mifare_desfire_crypto.c
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@ -380,9 +380,9 @@ mifare_cryto_preprocess_data (MifareTag tag, void *data, size_t *nbytes, off_t o
case MDCM_ENCIPHERED:
/* |<-------------- data -------------->|
* |<--- offset -->| |
* +-----+---------+--------------------+-----+---------+
* +---------------+--------------------+-----+---------+
* | CMD + HEADERS | DATA TO BE SECURED | CRC | PADDING |
* +-----+---------+--------------------+-----+---------+ ----------------
* +---------------+--------------------+-----+---------+ ----------------
* | |<~~~~v~~~~~~~~~~~~~>| ^ | | (DES / 3DES)
* | | `---- crc16() ----' | |
* | | | ^ | | ----- *or* -----
@ -523,6 +523,8 @@ mifare_cryto_postprocess_data (MifareTag tag, void *data, ssize_t *nbytes, int c
break;
case MDCM_ENCIPHERED:
(*nbytes)--;
bool verified = false;
int end_crc_pos;
switch (MIFARE_DESFIRE (tag)->authentication_scheme) {
case AS_LEGACY:
mifare_cypher_blocks_chained (tag, NULL, NULL, res, *nbytes, MCD_RECEIVE, MCO_DECYPHER);
@ -532,8 +534,7 @@ mifare_cryto_postprocess_data (MifareTag tag, void *data, ssize_t *nbytes, int c
* 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.
*/
bool verified = false;
int end_crc_pos = *nbytes - 7; // The CRC can be over two blocks
end_crc_pos = *nbytes - 7; // The CRC can be over two blocks
do {
uint16_t crc;
@ -566,32 +567,67 @@ mifare_cryto_postprocess_data (MifareTag tag, void *data, ssize_t *nbytes, int c
case AS_NEW:
mifare_cypher_blocks_chained (tag, NULL, NULL, res, *nbytes, MCD_RECEIVE, MCO_DECYPHER);
uint8_t *p = ((uint8_t *)res) + *nbytes - 1;
while (!*p) {
p--;
/*
* ,----------------------------+-----------------------------------------+-------------+
* \ BLOCK n-1 | BLOCK n | STATUS|
* / DATA | CRC0 | CRC1 | CRC2 | CRC3 | 0x80? | 0x00 | 0x00 | ... | 0x00 | 0x91 | 0x00 |
* `----------------------------+-----------------------------------------+-------------+
* <------------------------------ DATA --------------------------------->|
*
* <----------------- DATA ---------------->
* FRAME = PAYLOAD + CRC(PAYLOAD + STATUS) + PADDING + STATUS
* ^ |
* | |
* `------------------'
*/
/* Move status between payload and CRC */
res = assert_crypto_buffer_size (tag, (*nbytes) + 1);
memcpy (res, data, *nbytes);
int crc_pos = (*nbytes) - 16 - 3;
if (crc_pos < 0) {
/* Single block */
crc_pos = 0;
}
if (0x80 == *p)
p--;
p -= 3;
memmove (res + crc_pos + 1, res + crc_pos, *nbytes - crc_pos);
((uint8_t *)res)[crc_pos] = 0x00;
crc_pos++;
*nbytes += 1;
uint8_t crc_ref[4];
memcpy (crc_ref, p, 4);
*p++ = ((uint8_t *)res)[*nbytes];
do {
uint32_t crc;
end_crc_pos = crc_pos + 4;
desfire_crc32 (res, end_crc_pos, (uint8_t *)&crc);
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 - 1;
((uint8_t *)data)[(*nbytes)++] = 0x00;
} else {
uint8_t x = ((uint8_t *)res)[crc_pos - 1];
((uint8_t *)res)[crc_pos - 1] = ((uint8_t *)res)[crc_pos];
((uint8_t *)res)[crc_pos] = x;
crc_pos++;
}
} while (!verified && (end_crc_pos < *nbytes));
uint8_t crc[4];
desfire_crc32 (res, p - (uint8_t *)res, crc);
if (memcmp (crc, crc_ref, 4)) {
if (!verified) {
#if WITH_DEBUG
warnx ("AES CRC32 not verified in AES stream");
hexdump (crc_ref, 4, "Expect ", 0);
hexdump (crc, 4, "Actual ", 0);
hexdump (res, *nbytes, "KO ", 0);
warnx ("AES not verified");
#endif
MIFARE_DESFIRE (tag)->last_pcd_error = CRYPTO_ERROR;
*nbytes = -1;
res = NULL;
}
*nbytes = p - (uint8_t *)res;
}
break;
default:
@ -717,16 +753,7 @@ mifare_cypher_blocks_chained (MifareTag tag, MifareDESFireKey key, uint8_t *ivec
if (!key || !ivect)
abort();
switch (key->type) {
case T_DES:
case T_3DES:
case T_3K3DES:
block_size = 8;
break;
case T_AES:
block_size = 16;
break;
}
block_size = key_block_size (key);
size_t offset = 0;
while (offset < data_size) {