#define PRNG_SEQUENCE_LENGTH (1 << 16);
static uint32_t sync_time;
- static uint32_t sync_cycles;
+ static int32_t sync_cycles;
int catch_up_cycles = 0;
int last_catch_up = 0;
+ uint16_t elapsed_prng_sequences;
uint16_t consecutive_resyncs = 0;
int isOK = 0;
sync_time = GetCountSspClk() & 0xfffffff8;
sync_cycles = PRNG_SEQUENCE_LENGTH; // theory: Mifare Classic's random generator repeats every 2^16 cycles (and so do the tag nonces).
nt_attacked = 0;
- nt = 0;
par[0] = 0;
}
else {
#define MAX_UNEXPECTED_RANDOM 4 // maximum number of unexpected (i.e. real) random numbers when trying to sync. Then give up.
- #define MAX_SYNC_TRIES 16
+ #define MAX_SYNC_TRIES 32
+ #define NUM_DEBUG_INFOS 8 // per strategy
+ #define MAX_STRATEGY 3
uint16_t unexpected_random = 0;
uint16_t sync_tries = 0;
int16_t debug_info_nr = -1;
- uint32_t debug_info[MAX_SYNC_TRIES];
+ uint16_t strategy = 0;
+ int32_t debug_info[MAX_STRATEGY][NUM_DEBUG_INFOS];
+ uint32_t select_time;
+ uint32_t halt_time;
for(uint16_t i = 0; TRUE; i++) {
break;
}
+ if (strategy == 2) {
+ // test with additional hlt command
+ halt_time = 0;
+ int len = mifare_sendcmd_short(NULL, false, 0x50, 0x00, receivedAnswer, receivedAnswerPar, &halt_time);
+ if (len && MF_DBGLEVEL >= 3) {
+ Dbprintf("Unexpected response of %d bytes to hlt command (additional debugging).", len);
+ }
+ }
+
+ if (strategy == 3) {
+ // test with FPGA power off/on
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+ SpinDelay(200);
+ iso14443a_setup(FPGA_HF_ISO14443A_READER_MOD);
+ SpinDelay(100);
+ }
+
if(!iso14443a_select_card(uid, NULL, &cuid)) {
if (MF_DBGLEVEL >= 1) Dbprintf("Mifare: Can't select card");
continue;
}
+ select_time = GetCountSspClk();
+ elapsed_prng_sequences = 1;
if (debug_info_nr == -1) {
sync_time = (sync_time & 0xfffffff8) + sync_cycles + catch_up_cycles;
catch_up_cycles = 0;
// if we missed the sync time already, advance to the next nonce repeat
while(GetCountSspClk() > sync_time) {
+ elapsed_prng_sequences++;
sync_time = (sync_time & 0xfffffff8) + sync_cycles;
}
// Transmit MIFARE_CLASSIC_AUTH at synctime. Should result in returning the same tag nonce (== nt_attacked)
ReaderTransmit(mf_auth, sizeof(mf_auth), &sync_time);
} else {
- ReaderTransmit(mf_auth, sizeof(mf_auth), NULL);
+ // collect some information on tag nonces for debugging:
+ #define DEBUG_FIXED_SYNC_CYCLES PRNG_SEQUENCE_LENGTH
+ if (strategy == 0) {
+ // nonce distances at fixed time after card select:
+ sync_time = select_time + DEBUG_FIXED_SYNC_CYCLES;
+ } else if (strategy == 1) {
+ // nonce distances at fixed time between authentications:
+ sync_time = sync_time + DEBUG_FIXED_SYNC_CYCLES;
+ } else if (strategy == 2) {
+ // nonce distances at fixed time after halt:
+ sync_time = halt_time + DEBUG_FIXED_SYNC_CYCLES;
+ } else {
+ // nonce_distances at fixed time after power on
+ sync_time = DEBUG_FIXED_SYNC_CYCLES;
+ }
+ ReaderTransmit(mf_auth, sizeof(mf_auth), &sync_time);
}
// Receive the (4 Byte) "random" nonce
} else {
if (nt_distance == -99999) { // invalid nonce received
unexpected_random++;
- if (!nt_attacked && unexpected_random > MAX_UNEXPECTED_RANDOM) {
+ if (unexpected_random > MAX_UNEXPECTED_RANDOM) {
isOK = -3; // Card has an unpredictable PRNG. Give up
break;
} else {
}
}
if (++sync_tries > MAX_SYNC_TRIES) {
- if (sync_tries > 2 * MAX_SYNC_TRIES) {
+ if (strategy > MAX_STRATEGY || MF_DBGLEVEL < 3) {
isOK = -4; // Card's PRNG runs at an unexpected frequency or resets unexpectedly
break;
} else { // continue for a while, just to collect some debug info
- debug_info[++debug_info_nr] = nt_distance;
+ debug_info[strategy][debug_info_nr] = nt_distance;
+ debug_info_nr++;
+ if (debug_info_nr == NUM_DEBUG_INFOS) {
+ strategy++;
+ debug_info_nr = 0;
+ }
continue;
}
}
- sync_cycles = (sync_cycles - nt_distance);
+ sync_cycles = (sync_cycles - nt_distance/elapsed_prng_sequences);
if (sync_cycles <= 0) {
sync_cycles += PRNG_SEQUENCE_LENGTH;
}
if (MF_DBGLEVEL >= 3) {
- Dbprintf("calibrating in cycle %d. nt_distance=%d, Sync_cycles: %d\n", i, nt_distance, sync_cycles);
+ Dbprintf("calibrating in cycle %d. nt_distance=%d, elapsed_prng_sequences=%d, new sync_cycles: %d\n", i, nt_distance, elapsed_prng_sequences, sync_cycles);
}
continue;
}
catch_up_cycles = 0;
continue;
}
+ catch_up_cycles /= elapsed_prng_sequences;
if (catch_up_cycles == last_catch_up) {
consecutive_resyncs++;
}
else {
sync_cycles = sync_cycles + catch_up_cycles;
if (MF_DBGLEVEL >= 3) Dbprintf("Lost sync in cycle %d for the fourth time consecutively (nt_distance = %d). Adjusting sync_cycles to %d.\n", i, -catch_up_cycles, sync_cycles);
+ last_catch_up = 0;
+ catch_up_cycles = 0;
+ consecutive_resyncs = 0;
}
continue;
}
consecutive_resyncs = 0;
// Receive answer. This will be a 4 Bit NACK when the 8 parity bits are OK after decoding
- if (ReaderReceive(receivedAnswer, receivedAnswerPar))
- {
+ if (ReaderReceive(receivedAnswer, receivedAnswerPar)) {
catch_up_cycles = 8; // the PRNG is delayed by 8 cycles due to the NAC (4Bits = 0x05 encrypted) transfer
- if (nt_diff == 0)
- {
+ if (nt_diff == 0) {
par_low = par[0] & 0xE0; // there is no need to check all parities for other nt_diff. Parity Bits for mf_nr_ar[0..2] won't change
}
if (isOK == -4) {
if (MF_DBGLEVEL >= 3) {
- for(uint16_t i = 0; i < MAX_SYNC_TRIES; i++) {
- Dbprintf("collected debug info[%d] = %d\n", i, debug_info[i]);
+ for (uint16_t i = 0; i <= MAX_STRATEGY; i++) {
+ for(uint16_t j = 0; j < NUM_DEBUG_INFOS; j++) {
+ Dbprintf("collected debug info[%d][%d] = %d", i, j, debug_info[i][j]);
+ }
}
}
}
projects / proxmark3-svn / blobdiff