[proxmark3-svn] / client / mifarehost.c

// Merlok, 2011, 2012
// people from mifare@nethemba.com, 2010
//
// This code is licensed to you under the terms of the GNU GPL, version 2 or,
// at your option, any later version. See the LICENSE.txt file for the text of
// the license.
//-----------------------------------------------------------------------------
// mifare commands
//-----------------------------------------------------------------------------

#include "mifarehost.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>

#include "crapto1/crapto1.h"
#include "proxmark3.h"
#include "usb_cmd.h"
#include "cmdmain.h"
#include "ui.h"
#include "util.h"
#include "iso14443crc.h"

#include "mifare.h"

// mifare tracer flags used in mfTraceDecode()
#define TRACE_IDLE                                              0x00
#define TRACE_AUTH1                                             0x01
#define TRACE_AUTH2                                             0x02
#define TRACE_AUTH_OK                                   0x03
#define TRACE_READ_DATA                                 0x04
#define TRACE_WRITE_OK                                  0x05
#define TRACE_WRITE_DATA                                0x06
#define TRACE_ERROR                                             0xFF


static int compare_uint64(const void *a, const void *b) {
        // didn't work: (the result is truncated to 32 bits)
        //return (*(int64_t*)b - *(int64_t*)a);

        // better:
        if (*(uint64_t*)b == *(uint64_t*)a) return 0;
        else if (*(uint64_t*)b < *(uint64_t*)a) return 1;
        else return -1;
}


// create the intersection (common members) of two sorted lists. Lists are terminated by -1. Result will be in list1. Number of elements is returned.
static uint32_t intersection(uint64_t *list1, uint64_t *list2)
{
        if (list1 == NULL || list2 == NULL) {
                return 0;
        }
        uint64_t *p1, *p2, *p3;
        p1 = p3 = list1;
        p2 = list2;

        while ( *p1 != -1 && *p2 != -1 ) {
                if (compare_uint64(p1, p2) == 0) {
                        *p3++ = *p1++;
                        p2++;
                }
                else {
                        while (compare_uint64(p1, p2) < 0) ++p1;
                        while (compare_uint64(p1, p2) > 0) ++p2;
                }
        }
        *p3 = -1;
        return p3 - list1;
}


// Darkside attack (hf mf mifare)
static uint32_t nonce2key(uint32_t uid, uint32_t nt, uint32_t nr, uint64_t par_info, uint64_t ks_info, uint64_t **keys) {
        struct Crypto1State *states;
        uint32_t i, pos, rr; //nr_diff;
        uint8_t bt, ks3x[8], par[8][8];
        uint64_t key_recovered;
        static uint64_t *keylist;
        rr = 0;

        // Reset the last three significant bits of the reader nonce
        nr &= 0xffffff1f;

        for (pos=0; pos<8; pos++) {
                ks3x[7-pos] = (ks_info >> (pos*8)) & 0x0f;
                bt = (par_info >> (pos*8)) & 0xff;
                for (i=0; i<8; i++)     {
                                par[7-pos][i] = (bt >> i) & 0x01;
                }
        }

        states = lfsr_common_prefix(nr, rr, ks3x, par, (par_info == 0));

        if (states == NULL) {
                *keys = NULL;
                return 0;
        }

        keylist = (uint64_t*)states;

        for (i = 0; keylist[i]; i++) {
                lfsr_rollback_word(states+i, uid^nt, 0);
                crypto1_get_lfsr(states+i, &key_recovered);
                keylist[i] = key_recovered;
        }
        keylist[i] = -1;

        *keys = keylist;
        return i;
}


int mfDarkside(uint64_t *key)
{
        uint32_t uid = 0;
        uint32_t nt = 0, nr = 0;
        uint64_t par_list = 0, ks_list = 0;
        uint64_t *keylist = NULL, *last_keylist = NULL;
        uint32_t keycount = 0;
        int16_t isOK = 0;

        UsbCommand c = {CMD_READER_MIFARE, {true, 0, 0}};

        // message
        printf("-------------------------------------------------------------------------\n");
        printf("Executing command. Expected execution time: 25sec on average\n");
        printf("Press button on the proxmark3 device to abort both proxmark3 and client.\n");
        printf("-------------------------------------------------------------------------\n");


        while (true) {
                clearCommandBuffer();
                SendCommand(&c);

                //flush queue
                while (ukbhit()) {
                        int c = getchar(); (void) c;
                }

                // wait cycle
                while (true) {
                        printf(".");
                        fflush(stdout);
                        if (ukbhit()) {
                                return -5;
                                break;
                        }

                        UsbCommand resp;
                        if (WaitForResponseTimeout(CMD_ACK, &resp, 1000)) {
                                isOK  = resp.arg[0];
                                if (isOK < 0) {
                                        return isOK;
                                }
                                uid = (uint32_t)bytes_to_num(resp.d.asBytes +  0, 4);
                                nt =  (uint32_t)bytes_to_num(resp.d.asBytes +  4, 4);
                                par_list = bytes_to_num(resp.d.asBytes +  8, 8);
                                ks_list = bytes_to_num(resp.d.asBytes +  16, 8);
                                nr = bytes_to_num(resp.d.asBytes + 24, 4);
                                break;
                        }
                }

                if (par_list == 0 && c.arg[0] == true) {
                        PrintAndLog("Parity is all zero. Most likely this card sends NACK on every failed authentication.");
                        PrintAndLog("Attack will take a few seconds longer because we need two consecutive successful runs.");
                }
                c.arg[0] = false;

                keycount = nonce2key(uid, nt, nr, par_list, ks_list, &keylist);

                if (keycount == 0) {
                        PrintAndLog("Key not found (lfsr_common_prefix list is null). Nt=%08x", nt);
                        PrintAndLog("This is expected to happen in 25%% of all cases. Trying again with a different reader nonce...");
                        continue;
                }

                if (par_list == 0) {
                        qsort(keylist, keycount, sizeof(*keylist), compare_uint64);
                        keycount = intersection(last_keylist, keylist);
                        if (keycount == 0) {
                                free(last_keylist);
                                last_keylist = keylist;
                                continue;
                        }
                }

                if (keycount > 1) {
                        PrintAndLog("Found %u possible keys. Trying to authenticate with each of them ...\n", keycount);
                } else {
                        PrintAndLog("Found a possible key. Trying to authenticate...\n");
                }

                *key = -1;
                uint8_t keyBlock[USB_CMD_DATA_SIZE];
                int max_keys = USB_CMD_DATA_SIZE/6;
                for (int i = 0; i < keycount; i += max_keys) {
                        int size = keycount - i > max_keys ? max_keys : keycount - i;
                        for (int j = 0; j < size; j++) {
                                if (par_list == 0) {
                                        num_to_bytes(last_keylist[i*max_keys + j], 6, keyBlock);
                                } else {
                                        num_to_bytes(keylist[i*max_keys + j], 6, keyBlock);
                                }
                        }
                        if (!mfCheckKeys(0, 0, false, size, keyBlock, key)) {
                                break;
                        }
                }

                if (*key != -1) {
                        free(last_keylist);
                        free(keylist);
                        break;
                } else {
                        PrintAndLog("Authentication failed. Trying again...");
                        free(last_keylist);
                        last_keylist = keylist;
                }
        }

        return 0;
}


int mfCheckKeys (uint8_t blockNo, uint8_t keyType, bool clear_trace, uint8_t keycnt, uint8_t * keyBlock, uint64_t * key){

        *key = -1;

        UsbCommand c = {CMD_MIFARE_CHKKEYS, {((blockNo & 0xff) | ((keyType & 0xff) << 8)), clear_trace, keycnt}}; 
        memcpy(c.d.asBytes, keyBlock, 6 * keycnt);
        SendCommand(&c);

        UsbCommand resp;
        if (!WaitForResponseTimeout(CMD_ACK,&resp,3000)) return 1; 
        if ((resp.arg[0] & 0xff) != 0x01) return 2;
        *key = bytes_to_num(resp.d.asBytes, 6);
        return 0;
}

int mfCheckKeysSec(uint8_t sectorCnt, uint8_t keyType, uint8_t timeout14a, bool clear_trace, uint8_t keycnt, uint8_t * keyBlock, sector_t * e_sector){

        uint8_t keyPtr = 0;

        if (e_sector == NULL)
                return -1;

        UsbCommand c = {CMD_MIFARE_CHKKEYS, {((sectorCnt & 0xff) | ((keyType & 0xff) << 8)), (clear_trace | 0x02)|((timeout14a & 0xff) << 8), keycnt}}; 
        memcpy(c.d.asBytes, keyBlock, 6 * keycnt);
        SendCommand(&c);

        UsbCommand resp;
        if (!WaitForResponseTimeoutW(CMD_ACK, &resp, MAX(3000, 1000 + 13 * sectorCnt * keycnt * (keyType == 2 ? 2 : 1)), false)) return 1; // timeout: 13 ms / fail auth
        if ((resp.arg[0] & 0xff) != 0x01) return 2;
        
        bool foundAKey = false;
        for(int sec = 0; sec < sectorCnt; sec++){
                for(int keyAB = 0; keyAB < 2; keyAB++){
                        keyPtr = *(resp.d.asBytes + keyAB * 40 + sec);
                        if (keyPtr){
                                e_sector[sec].foundKey[keyAB] = true;
                                e_sector[sec].Key[keyAB] = bytes_to_num(keyBlock + (keyPtr - 1) * 6, 6);
                                foundAKey = true;
                        }
                }
        }
        return foundAKey ? 0 : 3;
}

// Compare 16 Bits out of cryptostate
int Compare16Bits(const void * a, const void * b) {
        if ((*(uint64_t*)b & 0x00ff000000ff0000) == (*(uint64_t*)a & 0x00ff000000ff0000)) return 0;
        else if ((*(uint64_t*)b & 0x00ff000000ff0000) > (*(uint64_t*)a & 0x00ff000000ff0000)) return 1;
        else return -1;
}

typedef
        struct {
                union {
                        struct Crypto1State *slhead;
                        uint64_t *keyhead;
                } head;
                union {
                        struct Crypto1State *sltail;
                        uint64_t *keytail;
                } tail;
                uint32_t len;
                uint32_t uid;
                uint32_t blockNo;
                uint32_t keyType;
                uint32_t nt;
                uint32_t ks1;
        } StateList_t;


// wrapper function for multi-threaded lfsr_recovery32
void
#ifdef __has_attribute
#if __has_attribute(force_align_arg_pointer)
__attribute__((force_align_arg_pointer)) 
#endif
#endif
*nested_worker_thread(void *arg)
{
        struct Crypto1State *p1;
        StateList_t *statelist = arg;

        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;
        qsort(statelist->head.slhead, statelist->len, sizeof(uint64_t), Compare16Bits);

        return statelist->head.slhead;
}


int mfnested(uint8_t blockNo, uint8_t keyType, uint8_t *key, uint8_t trgBlockNo, uint8_t trgKeyType, uint8_t *resultKey, bool calibrate)
{
        uint16_t i;
        uint32_t uid;
        UsbCommand resp;

        StateList_t statelists[2];
        struct Crypto1State *p1, *p2, *p3, *p4;

        // flush queue
        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, 1500)) {
                return -1;
        }

        if (resp.arg[0]) {
                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,  (void *)(resp.d.asBytes + 4 + i * 8 + 0), 4);
                memcpy(&statelists[i].ks1, (void *)(resp.d.asBytes + 4 + i * 8 + 4), 4);
        }

        // 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);
        }


        // the first 16 Bits of the cryptostate already contain part of our key.
        // Create the intersection of the two lists based on these 16 Bits and
        // roll back the cryptostate
        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) {
                                *p3 = *p1;
                                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) {
                                *p4 = *p2;
                                lfsr_rollback_word(p4, statelists[1].nt ^ statelists[1].uid, 0);
                                p4++;
                                p2++;
                        }
                }
                else {
                        while (Compare16Bits(p1, p2) == -1) p1++;
                        while (Compare16Bits(p1, p2) == 1) p2++;
                }
        }
        *(uint64_t*)p3 = -1;
        *(uint64_t*)p4 = -1;
        statelists[0].len = p3 - statelists[0].head.slhead;
        statelists[1].len = p4 - statelists[1].head.slhead;
        statelists[0].tail.sltail=--p3;
        statelists[1].tail.sltail=--p4;

        // 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);
        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);

        memset(resultKey, 0, 6);
        // The list may still contain several key candidates. Test each of them with mfCheckKeys
        for (i = 0; i < statelists[0].len; i++) {
                uint8_t keyBlock[6];
                uint64_t key64;
                crypto1_get_lfsr(statelists[0].head.slhead + i, &key64);
                num_to_bytes(key64, 6, keyBlock);
                key64 = 0;
                if (!mfCheckKeys(statelists[0].blockNo, statelists[0].keyType, false, 1, keyBlock, &key64)) {
                        num_to_bytes(key64, 6, resultKey);
                        break;
                }
        }

        free(statelists[0].head.slhead);
        free(statelists[1].head.slhead);

        return 0;
}

// EMULATOR

int mfEmlGetMem(uint8_t *data, int blockNum, int blocksCount) {
        UsbCommand c = {CMD_MIFARE_EML_MEMGET, {blockNum, blocksCount, 0}};
        SendCommand(&c);

  UsbCommand resp;
        if (!WaitForResponseTimeout(CMD_ACK,&resp,1500)) return 1;
        memcpy(data, resp.d.asBytes, blocksCount * 16);
        return 0;
}

int mfEmlSetMem(uint8_t *data, int blockNum, int blocksCount) {
        UsbCommand c = {CMD_MIFARE_EML_MEMSET, {blockNum, blocksCount, 0}};
        memcpy(c.d.asBytes, data, blocksCount * 16);
        SendCommand(&c);
        return 0;
}

// "MAGIC" CARD

int mfCGetBlock(uint8_t blockNo, uint8_t *data, uint8_t params) {
        uint8_t isOK = 0;

        UsbCommand c = {CMD_MIFARE_CGETBLOCK, {params, 0, blockNo}};
        SendCommand(&c);

        UsbCommand resp;
        if (WaitForResponseTimeout(CMD_ACK,&resp,1500)) {
                isOK  = resp.arg[0] & 0xff;
                memcpy(data, resp.d.asBytes, 16);
                if (!isOK) return 2;
        } else {
                PrintAndLog("Command execute timeout");
                return 1;
        }
        return 0;
}

int mfCSetBlock(uint8_t blockNo, uint8_t *data, uint8_t *uid, bool wantWipe, uint8_t params) {

        uint8_t isOK = 0;
        UsbCommand c = {CMD_MIFARE_CSETBLOCK, {wantWipe, params & (0xFE | (uid == NULL ? 0:1)), blockNo}};
        memcpy(c.d.asBytes, data, 16);
        SendCommand(&c);

        UsbCommand resp;
        if (WaitForResponseTimeout(CMD_ACK, &resp, 1500)) {
                isOK  = resp.arg[0] & 0xff;
                if (uid != NULL)
                        memcpy(uid, resp.d.asBytes, 4);
                if (!isOK)
                        return 2;
        } else {
                PrintAndLog("Command execute timeout");
                return 1;
        }

        return 0;
}

int mfCWipe(uint32_t numSectors, bool gen1b, bool wantWipe, bool wantFill) {
        uint8_t isOK = 0;
        uint8_t cmdParams = wantWipe + wantFill * 0x02 + gen1b * 0x04;
        UsbCommand c = {CMD_MIFARE_CWIPE, {numSectors, cmdParams, 0}};
        SendCommand(&c);

        UsbCommand resp;
        WaitForResponse(CMD_ACK,&resp);
        isOK  = resp.arg[0] & 0xff;
        
        return isOK;
}

int mfCSetUID(uint8_t *uid, uint8_t *atqa, uint8_t *sak, uint8_t *oldUID) {
        uint8_t oldblock0[16] = {0x00};
        uint8_t block0[16] = {0x00};
        int gen = 0, res;

        gen = mfCIdentify();

        /* generation 1a magic card by default */
        uint8_t cmdParams = CSETBLOCK_SINGLE_OPER;
        if (gen == 2) {
                /* generation 1b magic card */
                cmdParams = CSETBLOCK_SINGLE_OPER | CSETBLOCK_MAGIC_1B;
        }
        
        res = mfCGetBlock(0, oldblock0, cmdParams);

        if (res == 0) {
                memcpy(block0, oldblock0, 16);
                PrintAndLog("old block 0:  %s", sprint_hex(block0,16));
        } else {
                PrintAndLog("Couldn't get old data. Will write over the last bytes of Block 0.");
        }

        // fill in the new values
        // UID
        memcpy(block0, uid, 4);
        // Mifare UID BCC
        block0[4] = block0[0] ^ block0[1] ^ block0[2] ^ block0[3];
        // mifare classic SAK(byte 5) and ATQA(byte 6 and 7, reversed)
        if (sak != NULL)
                block0[5] = sak[0];
        if (atqa != NULL) {
                block0[6] = atqa[1];
                block0[7] = atqa[0];
        }
        PrintAndLog("new block 0:  %s", sprint_hex(block0, 16));

        res = mfCSetBlock(0, block0, oldUID, false, cmdParams);
        if (res) {
                PrintAndLog("Can't set block 0. Error: %d", res);
                return res;
        }
        
        return 0;
}

int mfCIdentify() {
        UsbCommand c = {CMD_MIFARE_CIDENT, {0, 0, 0}};
        SendCommand(&c);
        UsbCommand resp;
        WaitForResponse(CMD_ACK,&resp);

        uint8_t isGeneration = resp.arg[0] & 0xff;
        switch( isGeneration ){
                case 1: PrintAndLog("Chinese magic backdoor commands (GEN 1a) detected"); break;
                case 2: PrintAndLog("Chinese magic backdoor command (GEN 1b) detected"); break;
                default: PrintAndLog("No chinese magic backdoor command detected"); break;
        }

        return (int) isGeneration;
}


// SNIFFER

// constants
static uint8_t trailerAccessBytes[4] = {0x08, 0x77, 0x8F, 0x00};

// variables
char logHexFileName[FILE_PATH_SIZE] = {0x00};
static uint8_t traceCard[4096] = {0x00};
static char traceFileName[FILE_PATH_SIZE] = {0x00};
static int traceState = TRACE_IDLE;
static uint8_t traceCurBlock = 0;
static uint8_t traceCurKey = 0;

struct Crypto1State *traceCrypto1 = NULL;

struct Crypto1State *revstate;
uint64_t lfsr;
uint32_t ks2;
uint32_t ks3;

uint32_t uid;     // serial number
uint32_t nt;      // tag challenge
uint32_t nr_enc;  // encrypted reader challenge
uint32_t ar_enc;  // encrypted reader response
uint32_t at_enc;  // encrypted tag response

int isTraceCardEmpty(void) {
        return ((traceCard[0] == 0) && (traceCard[1] == 0) && (traceCard[2] == 0) && (traceCard[3] == 0));
}

int isBlockEmpty(int blockN) {
        for (int i = 0; i < 16; i++)
                if (traceCard[blockN * 16 + i] != 0) return 0;

        return 1;
}

int isBlockTrailer(int blockN) {
 return ((blockN & 0x03) == 0x03);
}

int saveTraceCard(void) {
        FILE * f;

        if ((!strlen(traceFileName)) || (isTraceCardEmpty())) return 0;

        f = fopen(traceFileName, "w+");
        if ( !f ) return 1;

        for (int i = 0; i < 64; i++) {  // blocks
                for (int j = 0; j < 16; j++)  // bytes
                        fprintf(f, "%02x", *(traceCard + i * 16 + j));
                if (i < 63)
                        fprintf(f,"\n");
        }
        fclose(f);
        return 0;
}

int loadTraceCard(uint8_t *tuid) {
        FILE * f;
        char buf[64] = {0x00};
        uint8_t buf8[64] = {0x00};
        int i, blockNum;

        if (!isTraceCardEmpty())
                saveTraceCard();

        memset(traceCard, 0x00, 4096);
        memcpy(traceCard, tuid + 3, 4);

        FillFileNameByUID(traceFileName, tuid, ".eml", 7);

        f = fopen(traceFileName, "r");
        if (!f) return 1;

        blockNum = 0;

        while(!feof(f)){

                memset(buf, 0, sizeof(buf));
                if (fgets(buf, sizeof(buf), f) == NULL) {
                        PrintAndLog("File reading error.");
                        fclose(f);
                        return 2;
        }

                if (strlen(buf) < 32){
                        if (feof(f)) break;
                        PrintAndLog("File content error. Block data must include 32 HEX symbols");
                        fclose(f);
                        return 2;
                }
                for (i = 0; i < 32; i += 2)
                        sscanf(&buf[i], "%02x", (unsigned int *)&buf8[i / 2]);

                memcpy(traceCard + blockNum * 16, buf8, 16);

                blockNum++;
        }
        fclose(f);

        return 0;
}

int mfTraceInit(uint8_t *tuid, uint8_t *atqa, uint8_t sak, bool wantSaveToEmlFile) {

        if (traceCrypto1)
                crypto1_destroy(traceCrypto1);

        traceCrypto1 = NULL;

        if (wantSaveToEmlFile)
                loadTraceCard(tuid);

        traceCard[4] = traceCard[0] ^ traceCard[1] ^ traceCard[2] ^ traceCard[3];
        traceCard[5] = sak;
        memcpy(&traceCard[6], atqa, 2);
        traceCurBlock = 0;
        uid = bytes_to_num(tuid + 3, 4);

        traceState = TRACE_IDLE;

        return 0;
}

void mf_crypto1_decrypt(struct Crypto1State *pcs, uint8_t *data, int len, bool isEncrypted){
        uint8_t bt = 0;
        int i;

        if (len != 1) {
                for (i = 0; i < len; i++)
                        data[i] = crypto1_byte(pcs, 0x00, isEncrypted) ^ data[i];
        } else {
                bt = 0;
                for (i = 0; i < 4; i++)
                        bt |= (crypto1_bit(pcs, 0, isEncrypted) ^ BIT(data[0], i)) << i;

                data[0] = bt;
        }
        return;
}


int mfTraceDecode(uint8_t *data_src, int len, bool wantSaveToEmlFile) {
        uint8_t data[64];

        if (traceState == TRACE_ERROR) return 1;
        if (len > 64) {
                traceState = TRACE_ERROR;
                return 1;
        }

        memcpy(data, data_src, len);
        if ((traceCrypto1) && ((traceState == TRACE_IDLE) || (traceState > TRACE_AUTH_OK))) {
                mf_crypto1_decrypt(traceCrypto1, data, len, 0);
                PrintAndLog("dec> %s", sprint_hex(data, len));
                AddLogHex(logHexFileName, "dec> ", data, len);
        }

        switch (traceState) {
        case TRACE_IDLE:
                // check packet crc16!
                if ((len >= 4) && (!CheckCrc14443(CRC_14443_A, data, len))) {
                        PrintAndLog("dec> CRC ERROR!!!");
                        AddLogLine(logHexFileName, "dec> ", "CRC ERROR!!!");
                        traceState = TRACE_ERROR;  // do not decrypt the next commands
                        return 1;
                }

                // AUTHENTICATION
                if ((len ==4) && ((data[0] == 0x60) || (data[0] == 0x61))) {
                        traceState = TRACE_AUTH1;
                        traceCurBlock = data[1];
                        traceCurKey = data[0] == 60 ? 1:0;
                        return 0;
                }

                // READ
                if ((len ==4) && ((data[0] == 0x30))) {
                        traceState = TRACE_READ_DATA;
                        traceCurBlock = data[1];
                        return 0;
                }

                // WRITE
                if ((len ==4) && ((data[0] == 0xA0))) {
                        traceState = TRACE_WRITE_OK;
                        traceCurBlock = data[1];
                        return 0;
                }

                // HALT
                if ((len ==4) && ((data[0] == 0x50) && (data[1] == 0x00))) {
                        traceState = TRACE_ERROR;  // do not decrypt the next commands
                        return 0;
                }

                return 0;
        break;

        case TRACE_READ_DATA:
                if (len == 18) {
                        traceState = TRACE_IDLE;

                        if (isBlockTrailer(traceCurBlock)) {
                                memcpy(traceCard + traceCurBlock * 16 + 6, data + 6, 4);
                        } else {
                                memcpy(traceCard + traceCurBlock * 16, data, 16);
                        }
                        if (wantSaveToEmlFile) saveTraceCard();
                        return 0;
                } else {
                        traceState = TRACE_ERROR;
                        return 1;
                }
        break;

        case TRACE_WRITE_OK:
                if ((len == 1) && (data[0] == 0x0a)) {
                        traceState = TRACE_WRITE_DATA;

                        return 0;
                } else {
                        traceState = TRACE_ERROR;
                        return 1;
                }
        break;

        case TRACE_WRITE_DATA:
                if (len == 18) {
                        traceState = TRACE_IDLE;

                        memcpy(traceCard + traceCurBlock * 16, data, 16);
                        if (wantSaveToEmlFile) saveTraceCard();
                        return 0;
                } else {
                        traceState = TRACE_ERROR;
                        return 1;
                }
        break;

        case TRACE_AUTH1:
                if (len == 4) {
                        traceState = TRACE_AUTH2;
                        nt = bytes_to_num(data, 4);
                        return 0;
                } else {
                        traceState = TRACE_ERROR;
                        return 1;
                }
        break;

        case TRACE_AUTH2:
                if (len == 8) {
                        traceState = TRACE_AUTH_OK;

                        nr_enc = bytes_to_num(data, 4);
                        ar_enc = bytes_to_num(data + 4, 4);
                        return 0;
                } else {
                        traceState = TRACE_ERROR;
                        return 1;
                }
        break;

        case TRACE_AUTH_OK:
                if (len ==4) {
                        traceState = TRACE_IDLE;

                        if (!traceCrypto1) {
                                at_enc = bytes_to_num(data, 4);

                                //  decode key here)
                                ks2 = ar_enc ^ prng_successor(nt, 64);
                                ks3 = at_enc ^ prng_successor(nt, 96);
                                revstate = lfsr_recovery64(ks2, ks3);
                                lfsr_rollback_word(revstate, 0, 0);
                                lfsr_rollback_word(revstate, 0, 0);
                                lfsr_rollback_word(revstate, nr_enc, 1);
                                lfsr_rollback_word(revstate, uid ^ nt, 0);

                                crypto1_get_lfsr(revstate, &lfsr);
                                printf("key> %x%x\n", (unsigned int)((lfsr & 0xFFFFFFFF00000000) >> 32), (unsigned int)(lfsr & 0xFFFFFFFF));
                                AddLogUint64(logHexFileName, "key> ", lfsr);
                        } else {
                                printf("key> nested not implemented!\n");
                                at_enc = bytes_to_num(data, 4);
                                
                                crypto1_destroy(traceCrypto1);

                                // not implemented
                                traceState = TRACE_ERROR;
                        }

                        int blockShift = ((traceCurBlock & 0xFC) + 3) * 16;
                        if (isBlockEmpty((traceCurBlock & 0xFC) + 3)) memcpy(traceCard + blockShift + 6, trailerAccessBytes, 4);

                        if (traceCurKey) {
                                num_to_bytes(lfsr, 6, traceCard + blockShift + 10);
                        } else {
                                num_to_bytes(lfsr, 6, traceCard + blockShift);
                        }
                        if (wantSaveToEmlFile) saveTraceCard();

                        if (traceCrypto1) {
                                crypto1_destroy(traceCrypto1);
                        }

                        // set cryptosystem state
                        traceCrypto1 = lfsr_recovery64(ks2, ks3);
                        return 0;
                } else {
                        traceState = TRACE_ERROR;
                        return 1;
                }
        break;

        default:
                traceState = TRACE_ERROR;
                return 1;
        }

        return 0;
}

// DECODING

int tryDecryptWord(uint32_t nt, uint32_t ar_enc, uint32_t at_enc, uint8_t *data, int len){
        /*
        uint32_t nt;      // tag challenge
        uint32_t ar_enc;  // encrypted reader response
        uint32_t at_enc;  // encrypted tag response
        */
        if (traceCrypto1) {
                crypto1_destroy(traceCrypto1);
        }
        ks2 = ar_enc ^ prng_successor(nt, 64);
        ks3 = at_enc ^ prng_successor(nt, 96);
        traceCrypto1 = lfsr_recovery64(ks2, ks3);

        mf_crypto1_decrypt(traceCrypto1, data, len, 0);

        PrintAndLog("Decrypted data: [%s]", sprint_hex(data,len) );
        crypto1_destroy(traceCrypto1);
        return 0;
}

/** validate_prng_nonce
 * Determine if nonce is deterministic. ie: Suspectable to Darkside attack.
 * returns
 *   true = weak prng
 *   false = hardend prng
 */
bool validate_prng_nonce(uint32_t nonce) {
        uint16_t *dist = 0;
        uint16_t x, i;

        dist = malloc(2 << 16);
        if(!dist)
                return -1;

        // init prng table:
        for (x = i = 1; i; ++i) {
                dist[(x & 0xff) << 8 | x >> 8] = i;
                x = x >> 1 | (x ^ x >> 2 ^ x >> 3 ^ x >> 5) << 15;
        }
        
        uint32_t res = (65535 - dist[nonce >> 16] + dist[nonce & 0xffff]) % 65535;
        
        free(dist);     
        return (res == 16);
}

/* Detect Tag Prng, 
* function performs a partial AUTH,  where it tries to authenticate against block0, key A, but only collects tag nonce.
* the tag nonce is check to see if it has a predictable PRNG.
* @returns 
*       TRUE if tag uses WEAK prng (ie Now the NACK bug also needs to be present for Darkside attack)
*   FALSE is tag uses HARDEND prng (ie hardnested attack possible, with known key)
*/
int DetectClassicPrng(void){

        UsbCommand resp, respA; 
        uint8_t cmd[] = {0x60, 0x00}; // MIFARE_AUTH_KEYA
        uint32_t flags = ISO14A_CONNECT | ISO14A_RAW | ISO14A_APPEND_CRC | ISO14A_NO_RATS;
        
        UsbCommand c = {CMD_READER_ISO_14443a, {flags, sizeof(cmd), 0}};
        memcpy(c.d.asBytes, cmd, sizeof(cmd));

        clearCommandBuffer();
        SendCommand(&c);
        if (!WaitForResponseTimeout(CMD_ACK, &resp, 2000)) {
        PrintAndLog("PRNG UID: Reply timeout.");
                return -1;
        }
        
        // if select tag failed.
        if (resp.arg[0] == 0) {
                PrintAndLog("PRNG error: selecting tag failed, can't detect prng.");
                return -1;
        }
        
        if (!WaitForResponseTimeout(CMD_ACK, &respA, 5000)) {
        PrintAndLog("PRNG data: Reply timeout.");
                return -1;
        }

        // check respA
        if (respA.arg[0] != 4) {
                PrintAndLog("PRNG data error: Wrong length: %d", respA.arg[0]);
                return -1;
        }

        uint32_t nonce = bytes_to_num(respA.d.asBytes, respA.arg[0]);
        return validate_prng_nonce(nonce);
}