hf mf mifare:

- gracefully exit on unsuccessful syncs instead of hard watchdog reset

armsrc/iso14443a.c

@@ -2016,6 +2016,7 @@ void ReaderMifare(bool first_try)
 	byte_t par_list[8] = {0x00};
 	byte_t ks_list[8] = {0x00};
 
+	#define PRNG_SEQUENCE_LENGTH  (1 << 16);
 	static uint32_t sync_time;
 	static uint32_t sync_cycles;
 	int catch_up_cycles = 0;
@@ -2026,7 +2027,7 @@ void ReaderMifare(bool first_try)
 	if (first_try) { 
 		mf_nr_ar3 = 0;
 		sync_time = GetCountSspClk() & 0xfffffff8;
-		sync_cycles = 65536;									// theory: Mifare Classic's random generator repeats every 2^16 cycles (and so do the nonces).
+		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;
@@ -2043,8 +2044,12 @@ void ReaderMifare(bool first_try)
 	LED_C_OFF();
 	
 
-	#define DARKSIDE_MAX_TRIES	32		// number of tries to sync on PRNG cycle. Then give up.
+	#define MAX_UNEXPECTED_RANDOM	4		// maximum number of unexpected (i.e. real) random numbers when trying to sync. Then give up.
-	uint16_t unsuccessfull_tries = 0;
+	#define MAX_SYNC_TRIES			16
+	uint16_t unexpected_random = 0;
+	uint16_t sync_tries = 0;
+	int16_t debug_info_nr = -1;
+	uint32_t debug_info[MAX_SYNC_TRIES];
 	
 	for(uint16_t i = 0; TRUE; i++) {
 		
@@ -2062,17 +2067,21 @@ void ReaderMifare(bool first_try)
 			continue;
 		}
 
-		sync_time = (sync_time & 0xfffffff8) + sync_cycles + catch_up_cycles;
+		if (debug_info_nr == -1) {
-		catch_up_cycles = 0;
+			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
+			// if we missed the sync time already, advance to the next nonce repeat
-		while(GetCountSspClk() > sync_time) {
+			while(GetCountSspClk() > sync_time) {
-			sync_time = (sync_time & 0xfffffff8) + sync_cycles;
+				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);
 		}			
 
-		// Transmit MIFARE_CLASSIC_AUTH at synctime. Should result in returning the same tag nonce (== nt_attacked) 
-		ReaderTransmit(mf_auth, sizeof(mf_auth), &sync_time);
-
 		// Receive the (4 Byte) "random" nonce
 		if (!ReaderReceive(receivedAnswer, receivedAnswerPar)) {
 			if (MF_DBGLEVEL >= 1)	Dbprintf("Mifare: Couldn't receive tag nonce");
@@ -2089,19 +2098,32 @@ void ReaderMifare(bool first_try)
 			int nt_distance = dist_nt(previous_nt, nt);
 			if (nt_distance == 0) {
 				nt_attacked = nt;
-			}
+			} else {
-			else {
 				if (nt_distance == -99999) { // invalid nonce received
-					unsuccessfull_tries++;
+					unexpected_random++;
-					if (!nt_attacked && unsuccessfull_tries > DARKSIDE_MAX_TRIES) {
+					if (!nt_attacked && unexpected_random > MAX_UNEXPECTED_RANDOM) {
 						isOK = -3;		// Card has an unpredictable PRNG. Give up	
 						break;
 					} else {
 						continue;		// continue trying...
 					}
 				}
+				if (++sync_tries > MAX_SYNC_TRIES) {
+					if (sync_tries > 2 * MAX_SYNC_TRIES) {
+						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;
+						continue;
+					}
+				}
 				sync_cycles = (sync_cycles - nt_distance);
-				if (MF_DBGLEVEL >= 3) Dbprintf("calibrating in cycle %d. nt_distance=%d, Sync_cycles: %d\n", i, nt_distance, sync_cycles);
+				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);
+				}
 				continue;
 			}
 		}
@@ -2173,6 +2195,14 @@ void ReaderMifare(bool first_try)
 
 	mf_nr_ar[3] &= 0x1F;
 
+	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]);
+			}
+		}
+	}
+	
 	byte_t buf[28];
 	memcpy(buf + 0,  uid, 4);
 	num_to_bytes(nt, 4, buf + 4);

client/cmdhfmf.c

@@ -58,6 +58,7 @@ start:
 				case -1 : PrintAndLog("Button pressed. Aborted.\n"); break;
 				case -2 : PrintAndLog("Card is not vulnerable to Darkside attack (doesn't send NACK on authentication requests).\n"); break;
 				case -3 : PrintAndLog("Card is not vulnerable to Darkside attack (its random number generator is not predictable).\n"); break;
+				case -4 : PrintAndLog("The card's random number generator is vulnerable but behaves somewhat weird (Mifare clone?). This needs to be fixed.\n"); break;
 				default: ;
 			}
 			break;

client/scripts/mifare_autopwn.lua

@@ -112,6 +112,8 @@ function mfcrack_inner()
 				return nil, "Card is not vulnerable to Darkside attack (doesn't send NACK on authentication requests). You can try 'script run mfkeys' or 'hf mf chk' to test various known keys."
 			elseif isOK == 0xFFFFFFFD then
 				return nil, "Card is not vulnerable to Darkside attack (its random number generator is not predictable). You can try 'script run mfkeys' or 'hf mf chk' to test various known keys."
+			elseif isOK == 0xFFFFFFFC then
+				return nil, "The card's random number generator is vulnerable but behaves somewhat weird (Mifare clone?). You can try 'script run mfkeys' or 'hf mf chk' to test various known keys."
 			elseif isOK ~= 1 then 
 				return nil, "Error occurred" 
 			end