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chg: getting crazy out of sync when running against magic cards.

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This commit is contained in:
iceman1001 2017-12-05 12:30:40 +01:00
commit 08193fd2e5
2 changed files with 22 additions and 4 deletions
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15
armsrc/iso14443a.c
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@ -2578,8 +2578,9 @@ void DetectNACKbug() {
uint8_t num_nacks = 0;
#define PRNG_SEQUENCE_LENGTH (1 << 16)
#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 32
#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 32
#define MAX_PRNG_TRIES 20 // when we gone through 10 prng sequences without managing to sync, then give up.
AppendCrc14443a(mf_auth, 2);
@ -2649,6 +2650,11 @@ void DetectNACKbug() {
// Transmit reader nonce with fake par
ReaderTransmitPar(mf_nr_ar, sizeof(mf_nr_ar), par, NULL);
if ( elapsed_prng_sequences > MAX_PRNG_TRIES) {
isOK = -4; // Card's PRNG runs at an unexpected frequency or resets unexpectedly
break;
}
// we didn't calibrate our clock yet,
// iceman: has to be calibrated every time.
if (previous_nt && !nt_attacked) {
@ -2682,6 +2688,11 @@ void DetectNACKbug() {
if (sync_cycles <= 0)
sync_cycles += PRNG_SEQUENCE_LENGTH;
if (sync_cycles > PRNG_SEQUENCE_LENGTH * 2 ) {
isOK = -4; // Card's PRNG runs at an unexpected frequency or resets unexpectedly
break;
}
if (MF_DBGLEVEL >= 4)
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);