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mifare_desfire_key.c
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mifare_desfire_key.c
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#include <stdlib.h>
#include <string.h>
#include <openssl/des.h>
#include <freefare.h>
#include "freefare_internal.h"
static inline void update_key_schedules(MifareDESFireKey key);
static inline void
update_key_schedules(MifareDESFireKey key)
{
DES_set_key((DES_cblock *)key->data, &(key->ks1));
DES_set_key((DES_cblock *)(key->data + 8), &(key->ks2));
if (MIFARE_KEY_3K3DES == key->type) {
DES_set_key((DES_cblock *)(key->data + 16), &(key->ks3));
}
}
MifareDESFireKey
mifare_desfire_des_key_new(const uint8_t value[8])
{
uint8_t data[8];
memcpy(data, value, 8);
for (int n = 0; n < 8; n++)
data[n] &= 0xfe;
return mifare_desfire_des_key_new_with_version(data);
}
MifareDESFireKey
mifare_desfire_des_key_new_with_version(const uint8_t value[8])
{
MifareDESFireKey key;
if ((key = malloc(sizeof(struct mifare_desfire_key)))) {
key->type = MIFARE_KEY_DES;
memcpy(key->data, value, 8);
memcpy(key->data + 8, value, 8);
update_key_schedules(key);
}
return key;
}
MifareDESFireKey
mifare_desfire_3des_key_new(const uint8_t value[16])
{
uint8_t data[16];
memcpy(data, value, 16);
for (int n = 0; n < 8; n++)
data[n] &= 0xfe;
for (int n = 8; n < 16; n++)
data[n] |= 0x01;
return mifare_desfire_3des_key_new_with_version(data);
}
MifareDESFireKey
mifare_desfire_3des_key_new_with_version(const uint8_t value[16])
{
MifareDESFireKey key;
if ((key = malloc(sizeof(struct mifare_desfire_key)))) {
key->type = MIFARE_KEY_2K3DES;
memcpy(key->data, value, 16);
update_key_schedules(key);
}
return key;
}
MifareDESFireKey
mifare_desfire_3k3des_key_new(const uint8_t value[24])
{
uint8_t data[24];
memcpy(data, value, 24);
for (int n = 0; n < 8; n++)
data[n] &= 0xfe;
return mifare_desfire_3k3des_key_new_with_version(data);
}
MifareDESFireKey
mifare_desfire_3k3des_key_new_with_version(const uint8_t value[24])
{
MifareDESFireKey key;
if ((key = malloc(sizeof(struct mifare_desfire_key)))) {
key->type = MIFARE_KEY_3K3DES;
memcpy(key->data, value, 24);
update_key_schedules(key);
}
return key;
}
MifareDESFireKey
mifare_desfire_aes_key_new(const uint8_t value[16])
{
return mifare_desfire_aes_key_new_with_version(value, 0);
}
MifareDESFireKey
mifare_desfire_aes_key_new_with_version(const uint8_t value[16], uint8_t version)
{
MifareDESFireKey key;
if ((key = malloc(sizeof(struct mifare_desfire_key)))) {
memcpy(key->data, value, 16);
key->type = MIFARE_KEY_AES128;
key->aes_version = version;
}
return key;
}
uint8_t
mifare_desfire_key_get_version(MifareDESFireKey key)
{
uint8_t version = 0;
if (key->type == MIFARE_KEY_AES128)
return key->aes_version;
for (int n = 0; n < 8; n++) {
version |= ((key->data[n] & 1) << (7 - n));
}
return version;
}
void
mifare_desfire_key_set_version(MifareDESFireKey key, uint8_t version)
{
if (key->type == MIFARE_KEY_AES128) {
key->aes_version = version;
return;
}
for (int n = 0; n < 8; n++) {
uint8_t version_bit = ((version & (1 << (7 - n))) >> (7 - n));
key->data[n] &= 0xfe;
key->data[n] |= version_bit;
switch (key->type) {
case MIFARE_KEY_DES:
// DESFire cards always treat DES keys as special cases of 2K3DES
// keys. The DESFire functional specification explicitly points
// out that if the subkeys of a 2K3DES key are exactly identical
// (including parity bits), then (and only then) is the key treated
// as a DES key for authentication purposes. Specifically, the
// version/parity bits must be idential, as well as the rest of the
// key, otherwise the PICC will treat it as a 2K3DES key. This
// next line ensure that.
key->data[n + 8] = key->data[n];
break;
case MIFARE_KEY_2K3DES:
// But what if we really did want the PICC to treat the key as a
// real 2K3DES key, even if the actual 56 bits of the subkeys did
// match? To ensure that such as case still works (largely because
// the datasheet implies authentication would behave differently
// otherwise), we need to ensure that the parity bits on the subkeys
// explicitly do not match. The easiest way to ensure that is to
// always write the bits of `~version` to the parity bits of the
// second subkey. Note that this would only have an effect at the
// PICC level if the subkeys were otherwise identical.
key->data[n + 8] &= 0xfe;
key->data[n + 8] |= !version_bit;
break;
default:
break;
}
}
}
MifareDESFireKey
mifare_desfire_session_key_new(const uint8_t rnda[], const uint8_t rndb[], MifareDESFireKey authentication_key)
{
MifareDESFireKey key = NULL;
uint8_t buffer[24];
switch (authentication_key->type) {
case MIFARE_KEY_DES:
memcpy(buffer, rnda, 4);
memcpy(buffer + 4, rndb, 4);
key = mifare_desfire_des_key_new_with_version(buffer);
break;
case MIFARE_KEY_2K3DES:
memcpy(buffer, rnda, 4);
memcpy(buffer + 4, rndb, 4);
memcpy(buffer + 8, rnda + 4, 4);
memcpy(buffer + 12, rndb + 4, 4);
key = mifare_desfire_3des_key_new_with_version(buffer);
break;
case MIFARE_KEY_3K3DES:
memcpy(buffer, rnda, 4);
memcpy(buffer + 4, rndb, 4);
memcpy(buffer + 8, rnda + 6, 4);
memcpy(buffer + 12, rndb + 6, 4);
memcpy(buffer + 16, rnda + 12, 4);
memcpy(buffer + 20, rndb + 12, 4);
key = mifare_desfire_3k3des_key_new(buffer);
break;
case MIFARE_KEY_AES128:
memcpy(buffer, rnda, 4);
memcpy(buffer + 4, rndb, 4);
memcpy(buffer + 8, rnda + 12, 4);
memcpy(buffer + 12, rndb + 12, 4);
key = mifare_desfire_aes_key_new(buffer);
break;
}
return key;
}
void
mifare_desfire_key_free(MifareDESFireKey key)
{
free(key);
}