add a specific check function for static nonces (used in 'hf mf nested') (#911)

* add a specific check function for static nonces in 'hf mf nested'
* uses a fixed nr_enc and does all the crypto operations on client
* for all possible keys calculate par_enc and ar_enc and send them to device
* CHANGELOG update

CHANGELOG.md

@@ -17,6 +17,7 @@ This project uses the changelog in accordance with [keepchangelog](http://keepac
 - `hf mf chk t` save to emulator memory now works as expected (mwalker)
 - Fix `hf mf sim` - wrong access rights to write key B in trailer (@McEloff)
 - allow files > 512Bytes in 'hf iclass eload' (@Sherhannn79)
+- `hf mf nested` now works with fixed nonce tags too (uzlonewolf, piwi)
  
 ### Added
 - Added to `hf 14a apdu` print apdu and compose apdu (@merlokk)

armsrc/mifarecmd.c

@@ -640,8 +640,7 @@ int valid_nonce(uint32_t Nt, uint32_t NtEnc, uint32_t Ks1, uint8_t *parity) {
 // Mifare Classic Cards" in Proceedings of the 22nd ACM SIGSAC Conference on
 // Computer and Communications Security, 2015
 //-----------------------------------------------------------------------------
-void MifareAcquireEncryptedNonces(uint32_t arg0, uint32_t arg1, uint32_t flags, uint8_t *datain)
+void MifareAcquireEncryptedNonces(uint32_t arg0, uint32_t arg1, uint32_t flags, uint8_t *datain) {
-{
 	uint64_t ui64Key = 0;
 	uint8_t uid[10];
 	uint32_t cuid;
@@ -666,7 +665,6 @@ void MifareAcquireEncryptedNonces(uint32_t arg0, uint32_t arg1, uint32_t flags,
 	bool field_off = flags & 0x0004;
 
 	LED_A_ON();
-	LED_C_OFF();
 
 	if (initialize) {
 		iso14443a_setup(FPGA_HF_ISO14443A_READER_LISTEN);
@@ -674,8 +672,6 @@ void MifareAcquireEncryptedNonces(uint32_t arg0, uint32_t arg1, uint32_t flags,
 		set_tracing(true);
 	}
 
-	LED_C_ON();
-
 	uint16_t num_nonces = 0;
 	bool have_uid = false;
 	for (uint16_t i = 0; i <= USB_CMD_DATA_SIZE - 9; ) {
@@ -747,21 +743,18 @@ void MifareAcquireEncryptedNonces(uint32_t arg0, uint32_t arg1, uint32_t flags,
 
 	}
 
-	LED_C_OFF();
-
 	crypto1_destroy(pcs);
 
 	if (field_off) {
 		FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
-		LEDsoff();
+		LED_D_OFF();
 	}
 
-	LED_B_ON();
-	cmd_send(CMD_ACK, isOK, cuid, num_nonces, buf, sizeof(buf));
-	LED_B_OFF();
-
 	if (MF_DBGLEVEL >= 3)   DbpString("AcquireEncryptedNonces finished");
 
+	cmd_send(CMD_ACK, isOK, cuid, num_nonces, buf, sizeof(buf));
+
+	LED_A_OFF();
 }
 
 
@@ -783,9 +776,10 @@ void MifareNested(uint32_t arg0, uint32_t arg1, uint32_t calibrate, uint8_t *dat
 	uint16_t davg;
 	static uint16_t dmin, dmax;
 	uint8_t uid[10];
-	uint32_t cuid, nt1, nt2, nttmp, nttest, ks1;
+	uint32_t cuid, nt1, nt2_enc, nttmp, nttest, ks1;
 	uint8_t par[1];
 	uint32_t target_nt[2], target_ks[2];
+	uint32_t fixed_nt = 0;
 	uint8_t target_nt_duplicate_count = 0;
 
 	uint8_t par_array[4];
@@ -812,7 +806,6 @@ void MifareNested(uint32_t arg0, uint32_t arg1, uint32_t calibrate, uint8_t *dat
 	#define NESTED_MAX_TRIES 12
 	uint16_t unsuccessfull_tries = 0;
 	if (calibrate) {    // for first call only. Otherwise reuse previous calibration
-		LED_B_ON();
 		WDT_HIT();
 
 		davg = dmax = 0;
@@ -846,13 +839,14 @@ void MifareNested(uint32_t arg0, uint32_t arg1, uint32_t calibrate, uint8_t *dat
 				rtr--;
 				continue;
 			};
+			fixed_nt = nt1;
 
 			if (delta_time) {
 				auth2_time = auth1_time + delta_time;
 			} else {
 				auth2_time = 0;
 			}
-			if (mifare_classic_authex(pcs, cuid, blockNo, keyType, ui64Key, AUTH_NESTED, &nt2, &auth2_time, NULL)) {
+			if (mifare_classic_authex(pcs, cuid, blockNo, keyType, ui64Key, AUTH_NESTED, &nt2_enc, &auth2_time, NULL)) {
 				if (MF_DBGLEVEL >= 1)   Dbprintf("Nested: Auth2 error");
 				rtr--;
 				continue;
@@ -861,7 +855,7 @@ void MifareNested(uint32_t arg0, uint32_t arg1, uint32_t calibrate, uint8_t *dat
 			nttmp = prng_successor(nt1, 100);               //NXP Mifare is typical around 840,but for some unlicensed/compatible mifare card this can be 160
 			for (i = 101; i < 1200; i++) {
 				nttmp = prng_successor(nttmp, 1);
-				if (nttmp == nt2) break;
+				if (nttmp == nt2_enc) break;
 			}
 
 			if (i != 1200) {
@@ -889,21 +883,17 @@ void MifareNested(uint32_t arg0, uint32_t arg1, uint32_t calibrate, uint8_t *dat
 		dmin = davg - 2;
 		dmax = davg + 2;
 
-		LED_B_OFF();
-
 	}
 	//  -------------------------------------------------------------------------------------------------
 
-	LED_C_ON();
-
 	//  get crypted nonces for target sector
-	for (i=0; i < 2 && !isOK; i++) { // look for exactly two different nonces
+	for (i = 0; i < 2 && !isOK; i++) { // look for exactly two different nonces
 
 		target_nt[i] = 0;
 		while (target_nt[i] == 0 && !isOK) { // continue until we have an unambiguous nonce
 
 			// prepare next select. No need to power down the card.
-			if(mifare_classic_halt(pcs, cuid)) {
+			if (mifare_classic_halt(pcs, cuid)) {
 				if (MF_DBGLEVEL >= 1)   Dbprintf("Nested: Halt error");
 				continue;
 			}
@@ -934,8 +924,8 @@ void MifareNested(uint32_t arg0, uint32_t arg1, uint32_t calibrate, uint8_t *dat
 				continue;
 			}
 
-			nt2 = bytes_to_num(receivedAnswer, 4);
+			nt2_enc = bytes_to_num(receivedAnswer, 4);
-			if (MF_DBGLEVEL >= 3) Dbprintf("Nonce#%d: Testing nt1=%08x nt2enc=%08x nt2par=%02x", i+1, nt1, nt2, par[0]);
+			if (MF_DBGLEVEL >= 3) Dbprintf("Nonce#%d: Testing nt1=%08x nt2enc=%08x nt2par=%02x", i+1, nt1, nt2_enc, par[0]);
 
 			// Parity validity check
 			for (j = 0; j < 4; j++) {
@@ -946,9 +936,9 @@ void MifareNested(uint32_t arg0, uint32_t arg1, uint32_t calibrate, uint8_t *dat
 			nttest = prng_successor(nt1, dmin - 1);
 			for (j = dmin; j < dmax + 1; j++) {
 				nttest = prng_successor(nttest, 1);
-				ks1 = nt2 ^ nttest;
+				ks1 = nt2_enc ^ nttest;
 
-				if (valid_nonce(nttest, nt2, ks1, par_array)){
+				if (valid_nonce(nttest, nt2_enc, ks1, par_array)){
 					if (ncount > 0) {       // we are only interested in disambiguous nonces, try again
 						if (MF_DBGLEVEL >= 3) Dbprintf("Nonce#%d: dismissed (ambigous), ntdist=%d", i+1, j);
 						target_nt[i] = 0;
@@ -974,28 +964,25 @@ void MifareNested(uint32_t arg0, uint32_t arg1, uint32_t calibrate, uint8_t *dat
 		}
 	}
 
-	LED_C_OFF();
+	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+	LED_D_OFF();
 
-	//  ----------------------------- crypto1 destroy
 	crypto1_destroy(pcs);
 
-	uint8_t buf[4 + 4 * 4 + 4];
+	uint8_t buf[4 + 4 * 4 + 4 + 4];
 	memcpy(buf, &cuid, 4);
 	memcpy(buf+4, &target_nt[0], 4);
 	memcpy(buf+8, &target_ks[0], 4);
 	memcpy(buf+12, &target_nt[1], 4);
 	memcpy(buf+16, &target_ks[1], 4);
 	memcpy(buf+20, &authentication_timeout, 4);
-
+	memcpy(buf+24, &fixed_nt, 4);
-	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
 
 	if (MF_DBGLEVEL >= 3)   DbpString("NESTED FINISHED");
 
-	LED_B_ON();
 	cmd_send(CMD_ACK, isOK, 0, targetBlockNo + (targetKeyType * 0x100), buf, sizeof(buf));
-	LED_B_OFF();
 
-	LEDsoff();
+	LED_A_OFF();
 }
 
 
@@ -1011,6 +998,7 @@ void MifareChkKeys(uint16_t arg0, uint32_t arg1, uint8_t arg2, uint8_t *datain)
 	bool multisectorCheck = arg1 & 0x02;
 	bool init = arg1 & 0x04;
 	bool drop_field = arg1 & 0x08;
+	bool fixed_nonce = arg1 & 0x10;
 	uint32_t auth_timeout = arg1 >> 16;
 	uint8_t keyCount = arg2;
 
@@ -1039,6 +1027,13 @@ void MifareChkKeys(uint16_t arg0, uint32_t arg1, uint8_t arg2, uint8_t *datain)
 		} else {
 			cmd_send(CMD_ACK, 0, res, 0, NULL, 0);
 		}
+	} else if (fixed_nonce) {
+		res = MifareChkBlockKeysFixedNonce(datain, keyCount, blockNo, keyType, &auth_timeout, OLD_MF_DBGLEVEL);
+		if (res > 0) {
+			cmd_send(CMD_ACK, 1, res, 0, NULL, 0); // key found
+		} else {
+			cmd_send(CMD_ACK, 0, res, 0, NULL, 0); // no key found or aborted
+		}
 	} else {
 		res = MifareChkBlockKeys(datain, keyCount, blockNo, keyType, &auth_timeout, OLD_MF_DBGLEVEL);
 		if (res > 0) {

armsrc/mifareutil.c

@@ -78,8 +78,7 @@ uint8_t mf_crypto1_encrypt4bit(struct Crypto1State *pcs, uint8_t data) {
 }
 
 // send X byte basic commands
-int mifare_sendcmd(uint8_t cmd, uint8_t* data, uint8_t data_size, uint8_t* answer, uint8_t *answer_parity, uint32_t *timing)
+int mifare_sendcmd(uint8_t cmd, uint8_t* data, uint8_t data_size, uint8_t* answer, uint8_t *answer_parity, uint32_t *timing) {
-{
 	uint8_t dcmd[data_size+3];
 	dcmd[0] = cmd;
 	memcpy(dcmd+1,data,data_size);
@@ -95,8 +94,7 @@ int mifare_sendcmd(uint8_t cmd, uint8_t* data, uint8_t data_size, uint8_t* answe
 }
 
 // send 2 byte commands
-int mifare_sendcmd_short(struct Crypto1State *pcs, uint8_t crypted, uint8_t cmd, uint8_t data, uint8_t *answer, uint8_t *answer_parity, uint32_t *timing)
+int mifare_sendcmd_short(struct Crypto1State *pcs, uint8_t crypted, uint8_t cmd, uint8_t data, uint8_t *answer, uint8_t *answer_parity, uint32_t *timing) {
-{
 	uint8_t dcmd[4], ecmd[4];
 	uint16_t pos, res;
 	uint8_t par[1];         // 1 Byte parity is enough here
@@ -211,7 +209,7 @@ int mifare_classic_authex(struct Crypto1State *pcs, uint32_t uid, uint8_t blockN
 	//  ar+parity
 	for (pos = 4; pos < 8; pos++) {
 		nt = prng_successor(nt,8);
-		mf_nr_ar[pos] = crypto1_byte(pcs,0x00,0) ^ (nt & 0xff);
+		mf_nr_ar[pos] = crypto1_byte(pcs, 0x00, 0) ^ (nt & 0xff);
 		par[0] |= (((filter(pcs->odd) ^ oddparity8(nt)) & 0x01) << (7-pos));
 	}
 
@@ -814,18 +812,17 @@ int mifare_desfire_des_auth2(uint32_t uid, uint8_t *key, uint8_t *blockData){
 //
 //-----------------------------------------------------------------------------
 // one key check
-int MifareChkBlockKey(uint8_t *uid, uint32_t *cuid, uint8_t *cascade_levels, uint64_t ui64Key, uint8_t blockNo, uint8_t keyType, uint32_t *auth_timeout, uint8_t debugLevel) {
+static int MifareChkBlockKey(uint8_t *uid, uint32_t *cuid, uint8_t *cascade_levels, uint8_t *key, uint8_t blockNo, uint8_t keyType, uint32_t *auth_timeout, uint8_t debugLevel, bool fixed_nonce) {
 
 	struct Crypto1State mpcs = {0, 0};
 	struct Crypto1State *pcs;
 	pcs = &mpcs;
 
-	// Iceman: use piwi's faster nonce collecting part in hardnested.
 	if (*cascade_levels == 0) { // need a full select cycle to get the uid first
 		iso14a_card_select_t card_info;
 		if (!iso14443a_select_card(uid, &card_info, cuid, true, 0, true)) {
 			if (debugLevel >= 1)    Dbprintf("ChkKeys: Can't select card");
-			return  1;
+			return  -1;
 		}
 		switch (card_info.uidlen) {
 			case 4 : *cascade_levels = 1; break;
@@ -836,63 +833,85 @@ int MifareChkBlockKey(uint8_t *uid, uint32_t *cuid, uint8_t *cascade_levels, uin
 	} else { // no need for anticollision. We can directly select the card
 		if (!iso14443a_select_card(uid, NULL, NULL, false, *cascade_levels, true)) {
 			if (debugLevel >= 1)    Dbprintf("ChkKeys: Can't select card (UID) lvl=%d", *cascade_levels);
-			return  1;
+			return  -1;
 		}
 	}
 
+	if (!fixed_nonce) {
+		uint64_t ui64Key = bytes_to_num(key, 6);
 		if (mifare_classic_auth(pcs, *cuid, blockNo, keyType, ui64Key, AUTH_FIRST, auth_timeout)) { // authentication failed
-		return 2;
+			return -2;
 		} else {
 			mifare_classic_halt(pcs, *cuid);
 		}
+	} else {
+		uint8_t receivedAnswer[MAX_MIFARE_FRAME_SIZE];
+		uint8_t receivedAnswerPar[MAX_MIFARE_PARITY_SIZE];
+		// Transmit MIFARE_CLASSIC_AUTH
+		int len = mifare_sendcmd_short(pcs, false, keyType & 0x01 ? MIFARE_AUTH_KEYB : MIFARE_AUTH_KEYA, blockNo, receivedAnswer, receivedAnswerPar, NULL);
+		if (len != 4) return -2;
+		// Transmit encrypted reader nonce and reader answer
+		uint8_t mf_nr_ar[8] = NESTED_FIXED_NR_ENC;
+		memcpy(mf_nr_ar + 4, key, 4);
+		ReaderTransmitPar(mf_nr_ar, sizeof(mf_nr_ar), key + 4, NULL);
+		uint32_t save_timeout = iso14a_get_timeout(); // save standard timeout
+		iso14a_set_timeout(*auth_timeout);            // set timeout for authentication response
+		len = ReaderReceive(receivedAnswer, receivedAnswerPar);
+		iso14a_set_timeout(save_timeout);             // restore standard timeout
+		if (!len) return -2;
+	}
 
-	return 0;
+	return 0; // success
 }
 
-
 // multi key check
-int MifareChkBlockKeys(uint8_t *keys, uint8_t keyCount, uint8_t blockNo, uint8_t keyType, uint32_t *auth_timeout, uint8_t debugLevel) {
+static int MifareChkBlockKeysEx(uint8_t *keys, uint8_t keyCount, uint8_t blockNo, uint8_t keyType, uint32_t *auth_timeout, uint8_t debugLevel, bool fixed_nonce) {
 
 	uint8_t uid[10];
 	uint32_t cuid = 0;
 	uint8_t cascade_levels = 0;
-	uint64_t ui64Key = 0;
 
 	int retryCount = 0;
 	for (uint8_t i = 0; i < keyCount; i++) {
-
+		uint8_t bytes_per_key = fixed_nonce ? 5 : 6;
-		ui64Key = bytes_to_num(keys + i * 6, 6);
+		int res = MifareChkBlockKey(uid, &cuid, &cascade_levels, keys + i*bytes_per_key, blockNo, keyType, auth_timeout, debugLevel, fixed_nonce);
-		int res = MifareChkBlockKey(uid, &cuid, &cascade_levels, ui64Key, blockNo, keyType, auth_timeout, debugLevel);
+		if (res == -1) { 		// couldn't select
-
-		// can't select
-		if (res == 1) {
 			retryCount++;
 			if (retryCount >= 5) {
-				Dbprintf("ChkKeys: block=%d key=%d. Can't select. Exit...", blockNo, keyType);
+				Dbprintf("ChkKeys: block=%d key=%d. Couldn't select. Exit...", blockNo, keyType);
 				return -1;
-			}
+			} else {
 				--i; // try the same key once again
-
 				SpinDelay(20);
-//          Dbprintf("ChkKeys: block=%d key=%d. Try the same key once again...", blockNo, keyType);
+				// Dbprintf("ChkKeys: block=%d key=%d. Try the same key once again...", blockNo, keyType);
+				continue;
+			}
+		}
+		if (res == -2) { 		// couldn't authenticate with this key
+			retryCount = 0;
 			continue;
 		}
 
-		// can't authenticate
+		return i + 1;           // successful authentication
-		if (res == 2) {
-			retryCount = 0;
-			continue; // can't auth. wrong key.
-		}
 
-		// successful authentication
-		return i + 1;
 	}
 
 	if (BUTTON_PRESS()) {
 		return -2;
 	}
 
-	return 0;
+	return 0;                   // couldn't authenticate with any key
+}
+
+
+int MifareChkBlockKeys(uint8_t *keys, uint8_t keyCount, uint8_t blockNo, uint8_t keyType, uint32_t *auth_timeout, uint8_t debugLevel) {
+	return MifareChkBlockKeysEx(keys, keyCount, blockNo, keyType, auth_timeout, debugLevel, false);
+}
+
+
+// fixed nonce check
+int MifareChkBlockKeysFixedNonce(uint8_t *ar_par, uint8_t ar_par_cnt, uint8_t blockNo, uint8_t keyType, uint32_t *auth_timeout, uint8_t debugLevel) {
+	return MifareChkBlockKeysEx(ar_par, ar_par_cnt, blockNo, keyType, auth_timeout, debugLevel, true);
 }
 
 

armsrc/mifareutil.h

@@ -87,7 +87,7 @@ int emlCheckValBl(int blockNum);
 
 // mifare check keys
 typedef uint8_t TKeyIndex[2][40];
-int MifareChkBlockKey(uint8_t *uid, uint32_t *cuid, uint8_t *cascade_levels, uint64_t ui64Key, uint8_t blockNo, uint8_t keyType, uint32_t *auth_timeout, uint8_t debugLevel);
+int MifareChkBlockKeysFixedNonce(uint8_t *ar_par, uint8_t ar_par_cnt, uint8_t blockNo, uint8_t keyType, uint32_t *auth_timeout, uint8_t debugLevel);
 int MifareChkBlockKeys(uint8_t *keys, uint8_t keyCount, uint8_t blockNo, uint8_t keyType, uint32_t *auth_timeout, uint8_t debugLevel);
 int MifareMultisectorChk(uint8_t *keys, uint8_t keyCount, uint8_t SectorCount, uint8_t keyType, uint32_t *auth_timeout, uint8_t debugLevel, TKeyIndex *keyIndex);
 

client/cmdhfmf.c

@@ -677,7 +677,7 @@ int CmdHF14AMfNested(const char *Cmd) {
 		// check if we can authenticate to sector
 		res = mfCheckKeys(blockNo, keyType, timeout14a, true, 1, key, &key64);
 		if (res) {
-			PrintAndLog("Can't authenticate to block:%3d key type:%c key:%s", blockNo, keyType?'B':'A', sprint_hex(key, 6));
+			PrintAndLog("Can't authenticate to block %d, key type %c, key %s", blockNo, keyType?'B':'A', sprint_hex(key, 6));
 			return 3;
 		}
 

client/mifare/mifarehost.c

@@ -221,19 +221,20 @@ int mfDarkside(uint64_t *key) {
 }
 
 
-int mfCheckKeys(uint8_t blockNo, uint8_t keyType, uint16_t timeout14a, bool clear_trace, uint32_t keycnt, uint8_t *keys, uint64_t *found_key) {
+static int mfCheckKeysEx(uint8_t blockNo, uint8_t keyType, uint16_t timeout14a, bool clear_trace, uint32_t keycnt, uint8_t *keys, uint64_t *found_key, bool fixed_nonce) {
 
 	bool display_progress = false;
 	uint64_t start_time = msclock();
 	uint64_t next_print_time = start_time + 5 * 1000;
 
 	if (keycnt > 1000) {
-		PrintAndLog("We have %d keys to check. This will take some time!", keycnt);
+		PrintAndLog("We have %d keys to check. This can take some time!", keycnt);
 		PrintAndLog("Press button to abort.");
 		display_progress = true;
 	}
 
-	uint32_t max_keys  = (keycnt > (USB_CMD_DATA_SIZE / 6)) ? (USB_CMD_DATA_SIZE / 6) : keycnt;
+	uint8_t bytes_per_key = fixed_nonce ? 5 : 6;
+	uint32_t max_keys = keycnt > USB_CMD_DATA_SIZE/bytes_per_key ? USB_CMD_DATA_SIZE/bytes_per_key : keycnt;
 	*found_key = -1;
 	bool multisectorCheck = false;
 
@@ -245,10 +246,10 @@ int mfCheckKeys(uint8_t blockNo, uint8_t keyType, uint16_t timeout14a, bool clea
 
 		bool init = (i == 0);
 		bool drop_field = (max_keys == keycnt);
-		uint8_t flags = clear_trace | multisectorCheck << 1 | init << 2 | drop_field << 3;
+		uint8_t flags = clear_trace | multisectorCheck << 1 | init << 2 | drop_field << 3 | fixed_nonce << 4;
 
 		UsbCommand c = {CMD_MIFARE_CHKKEYS, {((blockNo & 0xff) | ((keyType & 0xff) << 8)), flags | timeout14a << 16, max_keys}};
-		memcpy(c.d.asBytes, keys + i * 6, max_keys * 6);
+		memcpy(c.d.asBytes, keys + i * bytes_per_key, max_keys * bytes_per_key);
 		SendCommand(&c);
 
 		UsbCommand resp;
@@ -256,7 +257,7 @@ int mfCheckKeys(uint8_t blockNo, uint8_t keyType, uint16_t timeout14a, bool clea
 			return 1;
 
 		if ((resp.arg[0] & 0xff) != 0x01) {
-			if (((int)resp.arg[1]) < 0) {   // error
+			if ((int)resp.arg[1] < 0) {   // error or user aborted
 				return (int)resp.arg[1];
 			} else {                        // nothing found yet
 				if (display_progress && msclock() >= next_print_time) {
@@ -268,7 +269,11 @@ int mfCheckKeys(uint8_t blockNo, uint8_t keyType, uint16_t timeout14a, bool clea
 				}
 			}
 		} else {                            // success
+			if (fixed_nonce) {
+				*found_key = i + resp.arg[1] - 1;
+			} else {
 				*found_key = bytes_to_num(resp.d.asBytes, 6);
+			}
 			return 0;
 		}
 	}
@@ -277,7 +282,17 @@ int mfCheckKeys(uint8_t blockNo, uint8_t keyType, uint16_t timeout14a, bool clea
 }
 
 
-int mfCheckKeysSec(uint8_t sectorCnt, uint8_t keyType, uint16_t timeout14a, bool clear_trace, bool init, bool drop_field, uint8_t keycnt, uint8_t * keyBlock, sector_t * e_sector) {
+int mfCheckKeys(uint8_t blockNo, uint8_t keyType, uint16_t timeout14a, bool clear_trace, uint32_t keycnt, uint8_t *keys, uint64_t *found_key) {
+	return mfCheckKeysEx(blockNo, keyType, timeout14a, clear_trace, keycnt, keys, found_key, false);
+}
+
+
+static int mfCheckKeysFixedNonce(uint8_t blockNo, uint8_t keyType, uint16_t timeout14a, bool clear_trace, uint32_t keycnt, uint8_t *keys, uint32_t *key_index) {
+	return mfCheckKeysEx(blockNo, keyType, timeout14a, clear_trace, keycnt, keys, (uint64_t*)key_index, true);
+}
+
+
+int mfCheckKeysSec(uint8_t sectorCnt, uint8_t keyType, uint16_t timeout14a, bool clear_trace, bool init, bool drop_field, uint8_t keycnt, uint8_t *keyBlock, sector_t *e_sector) {
 
 	uint8_t keyPtr = 0;
 
@@ -330,7 +345,7 @@ typedef
 		uint32_t uid;
 		uint32_t blockNo;
 		uint32_t keyType;
-		uint32_t nt_enc;
+		uint32_t nt;
 		uint32_t ks1;
 	} StateList_t;
 
@@ -346,7 +361,7 @@ __attribute__((force_align_arg_pointer))
 	struct Crypto1State *p1;
 	StateList_t *statelist = arg;
 
-	statelist->head.slhead = lfsr_recovery32(statelist->ks1, statelist->nt_enc ^ statelist->uid);
+	statelist->head.slhead = lfsr_recovery32(statelist->ks1, statelist->nt ^ statelist->uid);
 	for (p1 = statelist->head.slhead; *(uint64_t *)p1 != 0; p1++);
 	statelist->len = p1 - statelist->head.slhead;
 	statelist->tail.sltail = --p1;
@@ -356,94 +371,84 @@ __attribute__((force_align_arg_pointer))
 }
 
 
-int mfnested(uint8_t blockNo, uint8_t keyType, uint16_t timeout14a, uint8_t *key, uint8_t trgBlockNo, uint8_t trgKeyType, uint8_t *resultKey, bool calibrate) {
+static int nested_fixed_nonce(StateList_t statelist, uint32_t fixed_nt, uint32_t authentication_timeout, uint8_t *resultKey) {
-	uint32_t i;
+	// We have a tag with a fixed nonce (nt) and therefore only one (usually long) list of possible crypto states.
-	uint32_t uid;
+	// Instead of testing all those keys on the device with a complete authentication cycle, we do all of the crypto operations here.
-	UsbCommand resp;
+	uint8_t nr_enc[4] = NESTED_FIXED_NR_ENC;             // we use a fixed {nr}
+	uint8_t ar[4];
+	num_to_bytes(prng_successor(fixed_nt, 64), 4, ar);   // ... and ar is fixed too
 
-	int num_unique_nonces;
+	// create an array of possible {ar} and parity bits
+	uint32_t num_ar_par = statelist.len;
+	uint8_t *ar_par = calloc(num_ar_par, 5);
+	if (ar_par == NULL) {
+		free(statelist.head.slhead);
+		return -4;
+	}
 
-	StateList_t statelists[2];
+	for (int i = 0; i < num_ar_par; i++) {
-	struct Crypto1State *p1, *p2, *p3, *p4;
+		// roll back to initial state using the nt observed with the nested authentication
+		lfsr_rollback_word(statelist.head.slhead + i, statelist.nt ^ statelist.uid, 0);
+		// instead feed in the fixed_nt for the first authentication
+		struct Crypto1State cs = *(statelist.head.slhead + i);
+		crypto1_word(&cs, fixed_nt ^ statelist.uid, 0);
+		// determine nr such that the resulting {nr} is constant and feed it into the cypher. Calculate the encrypted parity bits
+		uint8_t par_enc = 0;
+		for (int j = 0; j < 4; j++) {
+			uint8_t nr_byte = crypto1_byte(&cs, nr_enc[j], 1) ^ nr_enc[j];
+			par_enc |= (((filter(cs.odd) ^ oddparity8(nr_byte)) & 0x01) << (7-j));
+		}
+		// calculate the encrypted reader response {ar} and its parity bits
+		for (int j = 0; j < 4; j++) {
+			ar_par[5*i + j] = crypto1_byte(&cs, 0, 0) ^ ar[j];
+			par_enc |= ((filter(cs.odd) ^ oddparity8(ar[j])) & 0x01) << (3-j);
+		}
+		ar_par[5*i + 4] = par_enc;
+	}
 
-	uint8_t *keyBlock = NULL;
+	// test each {ar} response
+	uint32_t key_index;
+
+	int isOK = mfCheckKeysFixedNonce(statelist.blockNo, statelist.keyType, authentication_timeout, true, num_ar_par, ar_par, &key_index);
+
+	if (isOK == 0) {     // success, key found
+		// key_index contains the index into the cypher state list
+		struct Crypto1State *p1 = statelist.head.slhead + key_index;
 		uint64_t key64;
-
+		crypto1_get_lfsr(p1, &key64);
-	int isOK = 1;
+		num_to_bytes(key64, 6, resultKey);
-
-	// flush queue
-	(void)WaitForResponseTimeout(CMD_ACK,NULL,100);
-
-	UsbCommand c = {CMD_MIFARE_NESTED, {blockNo + keyType * 0x100, trgBlockNo + trgKeyType * 0x100, calibrate}};
-	memcpy(c.d.asBytes, key, 6);
-	SendCommand(&c);
-
-	if (!WaitForResponseTimeout(CMD_ACK, &resp, 2500)) {
-		// some cards can cause it to get stuck in a loop, so break out of it
-		UsbCommand c = {CMD_PING};
-		SendCommand(&c);
-		(void)WaitForResponseTimeout(CMD_ACK,NULL,500);
-		return -1;
 	}
-
+	if (isOK == 1) {     // timeout
-	if (resp.arg[0]) {
+		isOK = -1;
-		return resp.arg[0];  // error during nested
-	}
-
-	memcpy(&uid, resp.d.asBytes, 4);
-	PrintAndLog("uid:%08x trgbl=%d trgkey=%x", uid, (uint16_t)resp.arg[2] & 0xff, (uint16_t)resp.arg[2] >> 8);
-
-	for (i = 0; i < 2; i++) {
-		statelists[i].blockNo = resp.arg[2] & 0xff;
-		statelists[i].keyType = (resp.arg[2] >> 8) & 0xff;
-		statelists[i].uid = uid;
-		memcpy(&statelists[i].nt_enc,  (void *)(resp.d.asBytes + 4 + i * 8 + 0), 4);
-		memcpy(&statelists[i].ks1, (void *)(resp.d.asBytes + 4 + i * 8 + 4), 4);
-	}
-
-	uint32_t authentication_timeout;
-	memcpy(&authentication_timeout, resp.d.asBytes + 20, 4);
-	PrintAndLog("Setting authentication timeout to %" PRIu32 "us", authentication_timeout * 1000 / 106);
-	
-	if (statelists[0].nt_enc == statelists[1].nt_enc && statelists[0].ks1 == statelists[1].ks1)
-		num_unique_nonces = 1;
-	else
-		num_unique_nonces = 2;
-
-	// calc keys
-
-	pthread_t thread_id[2];
-
-	// create and run worker threads
-	for (i = 0; i < 2; i++) {
-		pthread_create(thread_id + i, NULL, nested_worker_thread, &statelists[i]);
-	}
-
-	// wait for threads to terminate:
-	for (i = 0; i < 2; i++) {
-		pthread_join(thread_id[i], (void*)&statelists[i].head.slhead);
 	}
+	free(statelist.head.slhead);
+	free(ar_par);
+	return isOK;
+}
 
 
-	// the first 16 Bits of the cryptostate already contain part of our key.
+static int nested_standard(StateList_t statelists[2], uint32_t authentication_timeout, uint8_t *resultKey) {
+
+	// the first 16 Bits of the crypto states already contain part of our key.
 	// Create the intersection of the two lists based on these 16 Bits and
-	// roll back the cryptostate
+	// roll back the crypto state for the remaining states
+	struct Crypto1State *p1, *p2, *p3, *p4;
 	p1 = p3 = statelists[0].head.slhead;
 	p2 = p4 = statelists[1].head.slhead;
 	while (p1 <= statelists[0].tail.sltail && p2 <= statelists[1].tail.sltail) {
 		if (Compare16Bits(p1, p2) == 0) {
 			struct Crypto1State savestate, *savep = &savestate;
 			savestate = *p1;
-			while(Compare16Bits(p1, savep) == 0 && p1 <= statelists[0].tail.sltail) {
+			while (Compare16Bits(p1, savep) == 0 && p1 <= statelists[0].tail.sltail) {
 				*p3 = *p1;
-				lfsr_rollback_word(p3, statelists[0].nt_enc ^ statelists[0].uid, 0);
+				lfsr_rollback_word(p3, statelists[0].nt ^ statelists[0].uid, 0);
 				p3++;
 				p1++;
 			}
 			savestate = *p2;
-			while(Compare16Bits(p2, savep) == 0 && p2 <= statelists[1].tail.sltail) {
+			while (Compare16Bits(p2, savep) == 0 && p2 <= statelists[1].tail.sltail) {
 				*p4 = *p2;
-				lfsr_rollback_word(p4, statelists[1].nt_enc ^ statelists[1].uid, 0);
+				lfsr_rollback_word(p4, statelists[1].nt ^ statelists[1].uid, 0);
 				p4++;
 				p2++;
 			}
@@ -460,53 +465,106 @@ int mfnested(uint8_t blockNo, uint8_t keyType, uint16_t timeout14a, uint8_t *key
 	statelists[0].tail.sltail=--p3;
 	statelists[1].tail.sltail=--p4;
 
-	for (i = 0; i < 2; i++) {
+	// the statelists now contain possible crypto states initialized with the key. The key we are searching for
-		PrintAndLog("statelist %d: length:%d block:%02d keytype:%d nt_enc:%08X ks1:%08X", i, statelists[i].len, statelists[i].blockNo, statelists[i].keyType, statelists[i].nt_enc, statelists[i].ks1);
+	// must be in the intersection of both lists. Sort the lists and create the intersection:
-	}
-
-	// the statelists now contain possible keys. The key we are searching for must be in the
-	// intersection of both lists. Create the intersection:
 	qsort(statelists[0].head.keyhead, statelists[0].len, sizeof(uint64_t), compare_uint64);
-
-	if (num_unique_nonces > 1) {
 	qsort(statelists[1].head.keyhead, statelists[1].len, sizeof(uint64_t), compare_uint64);
 	statelists[0].len = intersection(statelists[0].head.keyhead, statelists[1].head.keyhead);
-	}
-	else {
-		PrintAndLog("Nonce 1 and 2 are the same!");
-	}
 
+	// create an array of the possible keys
 	uint32_t num_keys = statelists[0].len;
-	keyBlock = calloc(num_keys, 6);
+	uint8_t *keys = calloc(num_keys, 6);
-	if (keyBlock == NULL) {
+	if (keys == NULL) {
 		free(statelists[0].head.slhead);
 		free(statelists[1].head.slhead);
 		return -4;
 	}
 
-	for (i = 0; i < num_keys; i++) {
+	uint64_t key64 = 0;
+	for (int i = 0; i < num_keys; i++) {
 		crypto1_get_lfsr(statelists[0].head.slhead + i, &key64);
-		num_to_bytes(key64, 6, keyBlock + i*6);
+		num_to_bytes(key64, 6, keys + i*6);
 	}
 
-	// The list may still contain several key candidates. Test each of them with mfCheckKeys
+	// and test each key with mfCheckKeys
-	isOK = mfCheckKeys(statelists[0].blockNo, statelists[0].keyType, authentication_timeout, true, num_keys, keyBlock, &key64);
+	int isOK = mfCheckKeys(statelists[0].blockNo, statelists[0].keyType, authentication_timeout, true, num_keys, keys, &key64);
 
 	if (isOK == 0) {     // success, key found
 		num_to_bytes(key64, 6, resultKey);
 	}
-
 	if (isOK == 1) {     // timeout
 		isOK = -1;
 	}
-
 	free(statelists[0].head.slhead);
 	free(statelists[1].head.slhead);
-	free(keyBlock);
+	free(keys);
-
 	return isOK;
 }
 
+
+int mfnested(uint8_t blockNo, uint8_t keyType, uint16_t timeout14a, uint8_t *key, uint8_t trgBlockNo, uint8_t trgKeyType, uint8_t *resultKey, bool calibrate) {
+
+	// flush queue
+	clearCommandBuffer();
+
+	UsbCommand c = {CMD_MIFARE_NESTED, {blockNo + keyType * 0x100, trgBlockNo + trgKeyType * 0x100, calibrate}};
+	memcpy(c.d.asBytes, key, 6);
+	SendCommand(&c);
+
+	UsbCommand resp;
+	if (!WaitForResponseTimeout(CMD_ACK, &resp, 1500)) {
+		return -1;
+	}
+
+	if ((int)resp.arg[0]) {
+		return (int)resp.arg[0];  // error during nested
+	}
+
+	uint32_t uid;
+	memcpy(&uid, resp.d.asBytes, 4);
+	PrintAndLog("uid:%08x trgbl=%d trgkey=%x", uid, (uint16_t)resp.arg[2] & 0xff, (uint16_t)resp.arg[2] >> 8);
+
+	StateList_t statelists[2];
+	for (int i = 0; i < 2; i++) {
+		statelists[i].blockNo = resp.arg[2] & 0xff;
+		statelists[i].keyType = (resp.arg[2] >> 8) & 0xff;
+		statelists[i].uid = uid;
+		memcpy(&statelists[i].nt,  (void *)(resp.d.asBytes + 4 + i * 8 + 0), 4);
+		memcpy(&statelists[i].ks1, (void *)(resp.d.asBytes + 4 + i * 8 + 4), 4);
+	}
+
+	uint32_t authentication_timeout;
+	memcpy(&authentication_timeout, resp.d.asBytes + 20, 4);
+	PrintAndLog("Setting authentication timeout to %" PRIu32 "us", authentication_timeout * 1000 / 106);
+
+	uint8_t num_unique_nonces;
+	uint32_t fixed_nt = 0;
+	if (statelists[0].nt == statelists[1].nt && statelists[0].ks1 == statelists[1].ks1) {
+		num_unique_nonces = 1;
+		memcpy(&fixed_nt, resp.d.asBytes + 24, 4);
+		PrintAndLog("Fixed nt detected: %08" PRIx32 " on first authentication, %08" PRIx32 " on nested authentication", fixed_nt, statelists[0].nt);
+	} else {
+		num_unique_nonces = 2;
+	}
+
+	// create and run worker threads to calculate possible crypto states
+	pthread_t thread_id[2];
+	for (int i = 0; i < num_unique_nonces; i++) {
+		pthread_create(thread_id + i, NULL, nested_worker_thread, &statelists[i]);
+	}
+	// wait for threads to terminate:
+	for (int i = 0; i < num_unique_nonces; i++) {
+		pthread_join(thread_id[i], (void*)&statelists[i].head.slhead);
+	}
+
+	if (num_unique_nonces == 2) {
+		return nested_standard(statelists, authentication_timeout, resultKey);
+	} else {
+		return nested_fixed_nonce(statelists[0], fixed_nt, authentication_timeout, resultKey);
+	}
+}
+
+
 // MIFARE
 int mfReadSector(uint8_t sectorNo, uint8_t keyType, uint8_t *key, uint8_t *data) {
 

include/mifare.h

@@ -19,6 +19,9 @@
 #define MF_MAD1_SECTOR 0x00
 #define MF_MAD2_SECTOR 0x10
 
+// Fixed encrypted nonce used for nested attack with fixed nonce tags
+#define NESTED_FIXED_NR_ENC   {0x70, 0x69, 0x77, 0x69}
+
 //-----------------------------------------------------------------------------
 // ISO 14443A
 //-----------------------------------------------------------------------------