]> cvs.zerfleddert.de Git - proxmark3-svn/blobdiff - armsrc/iso14443a.c
data askraw patches, data askedgedetect demod,
[proxmark3-svn] / armsrc / iso14443a.c
index a4632aa543cff67e05fb3b1d4c74cc56c95ca76a..b1639a88c0568693e40e5f904b343885e777562a 100644 (file)
@@ -22,9 +22,7 @@
 #include "mifareutil.h"
 
 static uint32_t iso14a_timeout;
-uint8_t *trace = (uint8_t *) BigBuf+TRACE_OFFSET;
 int rsamples = 0;
-int traceLen = 0;
 int tracing = TRUE;
 uint8_t trigger = 0;
 // the block number for the ISO14443-4 PCB
@@ -144,13 +142,14 @@ const uint8_t OddByteParity[256] = {
   1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1
 };
 
-
 void iso14a_set_trigger(bool enable) {
        trigger = enable;
 }
 
 void iso14a_clear_trace() {
-       memset(trace, 0x44, TRACE_SIZE);
+       uint8_t *trace = BigBuf_get_addr();
+       uint16_t max_traceLen = BigBuf_max_traceLen();
+       memset(trace, 0x44, max_traceLen);
        traceLen = 0;
 }
 
@@ -205,11 +204,13 @@ bool RAMFUNC LogTrace(const uint8_t *btBytes, uint16_t iLen, uint32_t timestamp_
 {
        if (!tracing) return FALSE;
        
+       uint8_t *trace = BigBuf_get_addr();
        uint16_t num_paritybytes = (iLen-1)/8 + 1;      // number of valid paritybytes in *parity
        uint16_t duration = timestamp_end - timestamp_start;
 
        // Return when trace is full
-       if (traceLen + sizeof(iLen) + sizeof(timestamp_start) + sizeof(duration) + num_paritybytes + iLen >= TRACE_SIZE) {
+       uint16_t max_traceLen = BigBuf_max_traceLen();
+       if (traceLen + sizeof(iLen) + sizeof(timestamp_start) + sizeof(duration) + num_paritybytes + iLen >= max_traceLen) {
                tracing = FALSE;        // don't trace any more
                return FALSE;
        }
@@ -310,6 +311,7 @@ static RAMFUNC bool MillerDecoding(uint8_t bit, uint32_t non_real_time)
        Uart.twoBits = (Uart.twoBits << 8) | bit;
        
        if (Uart.state == STATE_UNSYNCD) {                                                                                              // not yet synced
+       
                if (Uart.highCnt < 7) {                                                                                                 // wait for a stable unmodulated signal
                        if (Uart.twoBits == 0xffff) {
                                Uart.highCnt++;
@@ -399,7 +401,7 @@ static RAMFUNC bool MillerDecoding(uint8_t bit, uint32_t non_real_time)
                                        if (Uart.len) {
                                                return TRUE;                                                                                    // we are finished with decoding the raw data sequence
                                        } else {
-                                               UartReset();                                                                                    // Nothing received - try again
+                                               UartReset();                                    // Nothing receiver - start over
                                        }
                                }
                                if (Uart.state == STATE_START_OF_COMMUNICATION) {                               // error - must not follow directly after SOC
@@ -473,7 +475,6 @@ void DemodReset()
        Demod.endTime = 0;
 }
 
-
 void DemodInit(uint8_t *data, uint8_t *parity)
 {
        Demod.output = data;
@@ -592,9 +593,6 @@ void RAMFUNC SnoopIso14443a(uint8_t param) {
        // bit 1 - trigger from first reader 7-bit request
        
        LEDsoff();
-       // init trace buffer
-       iso14a_clear_trace();
-       iso14a_set_tracing(TRUE);
 
        // We won't start recording the frames that we acquire until we trigger;
        // a good trigger condition to get started is probably when we see a
@@ -602,22 +600,25 @@ void RAMFUNC SnoopIso14443a(uint8_t param) {
        // triggered == FALSE -- to wait first for card
        bool triggered = !(param & 0x03); 
        
+       // Allocate memory from BigBuf for some buffers
+       // free all previous allocations first
+       BigBuf_free();
+
        // The command (reader -> tag) that we're receiving.
-       // The length of a received command will in most cases be no more than 18 bytes.
-       // So 32 should be enough!
-       uint8_t *receivedCmd = ((uint8_t *)BigBuf) + RECV_CMD_OFFSET;
-       uint8_t *receivedCmdPar = ((uint8_t *)BigBuf) + RECV_CMD_PAR_OFFSET;
+       uint8_t *receivedCmd = BigBuf_malloc(MAX_FRAME_SIZE);
+       uint8_t *receivedCmdPar = BigBuf_malloc(MAX_PARITY_SIZE);
        
        // The response (tag -> reader) that we're receiving.
-       uint8_t *receivedResponse = ((uint8_t *)BigBuf) + RECV_RESP_OFFSET;
-       uint8_t *receivedResponsePar = ((uint8_t *)BigBuf) + RECV_RESP_PAR_OFFSET;
-       
-       // As we receive stuff, we copy it from receivedCmd or receivedResponse
-       // into trace, along with its length and other annotations.
-       //uint8_t *trace = (uint8_t *)BigBuf;
+       uint8_t *receivedResponse = BigBuf_malloc(MAX_FRAME_SIZE);
+       uint8_t *receivedResponsePar = BigBuf_malloc(MAX_PARITY_SIZE);
        
        // The DMA buffer, used to stream samples from the FPGA
-       uint8_t *dmaBuf = ((uint8_t *)BigBuf) + DMA_BUFFER_OFFSET;
+       uint8_t *dmaBuf = BigBuf_malloc(DMA_BUFFER_SIZE);
+
+       // init trace buffer
+       iso14a_clear_trace();
+       iso14a_set_tracing(TRUE);
+
        uint8_t *data = dmaBuf;
        uint8_t previous_data = 0;
        int maxDataLen = 0;
@@ -657,7 +658,7 @@ void RAMFUNC SnoopIso14443a(uint8_t param) {
                // test for length of buffer
                if(dataLen > maxDataLen) {
                        maxDataLen = dataLen;
-                       if(dataLen > 400) {
+                       if(dataLen > (9 * DMA_BUFFER_SIZE / 10)) {
                                Dbprintf("blew circular buffer! dataLen=%d", dataLen);
                                break;
                        }
@@ -763,7 +764,6 @@ static void CodeIso14443aAsTagPar(const uint8_t *cmd, uint16_t len, uint8_t *par
        
        // Send startbit
        ToSend[++ToSendMax] = SEC_D;
-       
        LastProxToAirDuration = 8 * ToSendMax - 4;
 
        for(uint16_t i = 0; i < len; i++) {
@@ -887,7 +887,7 @@ int EmSendCmdPar(uint8_t *resp, uint16_t respLen, uint8_t *par);
 bool EmLogTrace(uint8_t *reader_data, uint16_t reader_len, uint32_t reader_StartTime, uint32_t reader_EndTime, uint8_t *reader_Parity,
                                 uint8_t *tag_data, uint16_t tag_len, uint32_t tag_StartTime, uint32_t tag_EndTime, uint8_t *tag_Parity);
 
-static uint8_t* free_buffer_pointer = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET);
+static uint8_t* free_buffer_pointer;
 
 typedef struct {
   uint8_t* response;
@@ -897,10 +897,6 @@ typedef struct {
   uint32_t ProxToAirDuration;
 } tag_response_info_t;
 
-void reset_free_buffer() {
-  free_buffer_pointer = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET);
-}
-
 bool prepare_tag_modulation(tag_response_info_t* response_info, size_t max_buffer_size) {
        // Example response, answer to MIFARE Classic read block will be 16 bytes + 2 CRC = 18 bytes
        // This will need the following byte array for a modulation sequence
@@ -912,7 +908,8 @@ bool prepare_tag_modulation(tag_response_info_t* response_info, size_t max_buffe
        // ----------- +
        //    166 bytes, since every bit that needs to be send costs us a byte
        //
-  
   // Prepare the tag modulation bits from the message
   CodeIso14443aAsTag(response_info->response,response_info->response_n);
   
@@ -933,15 +930,22 @@ bool prepare_tag_modulation(tag_response_info_t* response_info, size_t max_buffe
   return true;
 }
 
+
+// "precompile" responses. There are 7 predefined responses with a total of 28 bytes data to transmit.
+// Coded responses need one byte per bit to transfer (data, parity, start, stop, correction) 
+// 28 * 8 data bits, 28 * 1 parity bits, 7 start bits, 7 stop bits, 7 correction bits
+// -> need 273 bytes buffer
+#define ALLOCATED_TAG_MODULATION_BUFFER_SIZE 273
+
 bool prepare_allocated_tag_modulation(tag_response_info_t* response_info) {
   // Retrieve and store the current buffer index
   response_info->modulation = free_buffer_pointer;
   
   // Determine the maximum size we can use from our buffer
-  size_t max_buffer_size = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET + FREE_BUFFER_SIZE) - free_buffer_pointer;
+  size_t max_buffer_size = ALLOCATED_TAG_MODULATION_BUFFER_SIZE;
   
   // Forward the prepare tag modulation function to the inner function
-  if (prepare_tag_modulation(response_info,max_buffer_size)) {
+  if (prepare_tag_modulation(response_info, max_buffer_size)) {
     // Update the free buffer offset
     free_buffer_pointer += ToSendMax;
     return true;
@@ -956,10 +960,6 @@ bool prepare_allocated_tag_modulation(tag_response_info_t* response_info) {
 //-----------------------------------------------------------------------------
 void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
 {
-       // Enable and clear the trace
-       iso14a_clear_trace();
-       iso14a_set_tracing(TRUE);
-
        uint8_t sak;
 
        // The first response contains the ATQA (note: bytes are transmitted in reverse order).
@@ -990,6 +990,12 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
                        response1[1] = 0x00;
                        sak = 0x28;
                } break;
+               case 5: { // MIFARE TNP3XXX
+                       // Says: I am a toy
+                       response1[0] = 0x01;
+                       response1[1] = 0x0f;
+                       sak = 0x01;
+               } break;                
                default: {
                        Dbprintf("Error: unkown tagtype (%d)",tagType);
                        return;
@@ -997,10 +1003,11 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
        }
        
        // The second response contains the (mandatory) first 24 bits of the UID
-       uint8_t response2[5];
+       uint8_t response2[5] = {0x00};
 
        // Check if the uid uses the (optional) part
-       uint8_t response2a[5];
+       uint8_t response2a[5] = {0x00};
+       
        if (uid_2nd) {
                response2[0] = 0x88;
                num_to_bytes(uid_1st,3,response2+1);
@@ -1021,12 +1028,12 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
        response2[4] = response2[0] ^ response2[1] ^ response2[2] ^ response2[3];
 
        // Prepare the mandatory SAK (for 4 and 7 byte UID)
-       uint8_t response3[3];
+       uint8_t response3[3]  = {0x00};
        response3[0] = sak;
        ComputeCrc14443(CRC_14443_A, response3, 1, &response3[1], &response3[2]);
 
        // Prepare the optional second SAK (for 7 byte UID), drop the cascade bit
-       uint8_t response3a[3];
+       uint8_t response3a[3]  = {0x00};
        response3a[0] = sak & 0xFB;
        ComputeCrc14443(CRC_14443_A, response3a, 1, &response3a[1], &response3a[2]);
 
@@ -1062,9 +1069,17 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
                .modulation_n = 0
        };
   
-       // Reset the offset pointer of the free buffer
-       reset_free_buffer();
-  
+       BigBuf_free_keep_EM();
+
+       // allocate buffers:
+       uint8_t *receivedCmd = BigBuf_malloc(MAX_FRAME_SIZE);
+       uint8_t *receivedCmdPar = BigBuf_malloc(MAX_PARITY_SIZE);
+       free_buffer_pointer = BigBuf_malloc(ALLOCATED_TAG_MODULATION_BUFFER_SIZE);
+
+       // clear trace
+    iso14a_clear_trace();
+       iso14a_set_tracing(TRUE);
+
        // Prepare the responses of the anticollision phase
        // there will be not enough time to do this at the moment the reader sends it REQA
        for (size_t i=0; i<TAG_RESPONSE_COUNT; i++) {
@@ -1085,10 +1100,6 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
        // We need to listen to the high-frequency, peak-detected path.
        iso14443a_setup(FPGA_HF_ISO14443A_TAGSIM_LISTEN);
 
-       // buffers used on software Uart:
-       uint8_t *receivedCmd = ((uint8_t *)BigBuf) + RECV_CMD_OFFSET;
-       uint8_t *receivedCmdPar = ((uint8_t *)BigBuf) + RECV_CMD_PAR_OFFSET;
-
        cmdsRecvd = 0;
        tag_response_info_t* p_response;
 
@@ -1123,7 +1134,7 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
                        // We already responded, do not send anything with the EmSendCmd14443aRaw() that is called below
                        p_response = NULL;
                } else if(receivedCmd[0] == 0x50) {     // Received a HALT
-//                     DbpString("Reader requested we HALT!:");
+
                        if (tracing) {
                                LogTrace(receivedCmd, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
                        }
@@ -1228,6 +1239,7 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
                        // do the tracing for the previous reader request and this tag answer:
                        uint8_t par[MAX_PARITY_SIZE];
                        GetParity(p_response->response, p_response->response_n, par);
+       
                        EmLogTrace(Uart.output, 
                                                Uart.len, 
                                                Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, 
@@ -1248,6 +1260,7 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
 
        Dbprintf("%x %x %x", happened, happened2, cmdsRecvd);
        LED_A_OFF();
+       BigBuf_free_keep_EM();
 }
 
 
@@ -1308,13 +1321,6 @@ static void TransmitFor14443a(const uint8_t *cmd, uint16_t len, uint32_t *timing
        // clear TXRDY
        AT91C_BASE_SSC->SSC_THR = SEC_Y;
 
-       // for(uint16_t c = 0; c < 10;) {       // standard delay for each transfer (allow tag to be ready after last transmission)
-               // if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-                       // AT91C_BASE_SSC->SSC_THR = SEC_Y;     
-                       // c++;
-               // }
-       // }
-
        uint16_t c = 0;
        for(;;) {
                if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
@@ -1327,7 +1333,6 @@ static void TransmitFor14443a(const uint8_t *cmd, uint16_t len, uint32_t *timing
        }
        
        NextTransferTime = MAX(NextTransferTime, LastTimeProxToAirStart + REQUEST_GUARD_TIME);
-       
 }
 
 
@@ -1669,7 +1674,6 @@ static int GetIso14443aAnswerFromTag(uint8_t *receivedResponse, uint8_t *receive
 
 void ReaderTransmitBitsPar(uint8_t* frame, uint16_t bits, uint8_t *par, uint32_t *timing)
 {
-
        CodeIso14443aBitsAsReaderPar(frame, bits, par);
   
        // Send command to tag
@@ -1730,8 +1734,8 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
        uint8_t sel_all[]    = { 0x93,0x20 };
        uint8_t sel_uid[]    = { 0x93,0x70,0x00,0x00,0x00,0x00,0x00,0x00,0x00};
        uint8_t rats[]       = { 0xE0,0x80,0x00,0x00 }; // FSD=256, FSDI=8, CID=0
-       uint8_t *resp = ((uint8_t *)BigBuf) + RECV_RESP_OFFSET;
-       uint8_t *resp_par = ((uint8_t *)BigBuf) + RECV_RESP_PAR_OFFSET;
+       uint8_t resp[MAX_FRAME_SIZE]; // theoretically. A usual RATS will be much smaller
+       uint8_t resp_par[MAX_PARITY_SIZE];
        byte_t uid_resp[4];
        size_t uid_resp_len;
 
@@ -1744,7 +1748,6 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
        
        // Receive the ATQA
        if(!ReaderReceive(resp, resp_par)) return 0;
-       //Dbprintf("atqa: %02x %02x",resp[1],resp[0]);
 
        if(p_hi14a_card) {
                memcpy(p_hi14a_card->atqa, resp, 2);
@@ -1777,7 +1780,7 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
                                Dbprintf("Multiple tags detected. Collision after Bit %d", Demod.collisionPos);
                                for (uint16_t i = collision_answer_offset; i < Demod.collisionPos; i++, uid_resp_bits++) {      // add valid UID bits before collision point
                                        uint16_t UIDbit = (resp[i/8] >> (i % 8)) & 0x01;
-                                       uid_resp[uid_resp_bits & 0xf8] |= UIDbit << (uid_resp_bits % 8);
+                                       uid_resp[uid_resp_bits 8] |= UIDbit << (uid_resp_bits % 8);
                                }
                                uid_resp[uid_resp_bits/8] |= 1 << (uid_resp_bits % 8);                                  // next time select the card(s) with a 1 in the collision position
                                uid_resp_bits++;
@@ -1800,7 +1803,6 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
                        memcpy(uid_resp, resp, 4);
                }
                uid_resp_len = 4;
-               //Dbprintf("uid: %02x %02x %02x %02x",uid_resp[0],uid_resp[1],uid_resp[2],uid_resp[3]);
 
                // calculate crypto UID. Always use last 4 Bytes.
                if(cuid_ptr) {
@@ -1818,15 +1820,10 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
                if (!ReaderReceive(resp, resp_par)) return 0;
                sak = resp[0];
 
-               // Test if more parts of the uid are comming
+    // Test if more parts of the uid are coming
                if ((sak & 0x04) /* && uid_resp[0] == 0x88 */) {
                        // Remove first byte, 0x88 is not an UID byte, it CT, see page 3 of:
                        // http://www.nxp.com/documents/application_note/AN10927.pdf
-                       // This was earlier:
-                       //memcpy(uid_resp, uid_resp + 1, 3);
-                       // But memcpy should not be used for overlapping arrays, 
-                       // and memmove appears to not be available in the arm build. 
-                       // Therefore:
                        uid_resp[0] = uid_resp[1];
                        uid_resp[1] = uid_resp[2];
                        uid_resp[2] = uid_resp[3]; 
@@ -1849,9 +1846,8 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
                p_hi14a_card->ats_len = 0;
        }
 
-       if( (sak & 0x20) == 0) {
-               return 2; // non iso14443a compliant tag
-       }
+       // non iso14443a compliant tag
+       if( (sak & 0x20) == 0) return 2; 
 
        // Request for answer to select
        AppendCrc14443a(rats, 2);
@@ -1859,6 +1855,7 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
 
        if (!(len = ReaderReceive(resp, resp_par))) return 0;
 
+       
        if(p_hi14a_card) {
                memcpy(p_hi14a_card->ats, resp, sizeof(p_hi14a_card->ats));
                p_hi14a_card->ats_len = len;
@@ -1866,7 +1863,6 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
 
        // reset the PCB block number
        iso14_pcb_blocknum = 0;
-       
        return 1;       
 }
 
@@ -1957,7 +1953,7 @@ void ReaderIso14443a(UsbCommand *c)
        }
 
        if(param & ISO14A_SET_TIMEOUT) {
-               iso14a_timeout = c->arg[2];
+               iso14a_set_timeout(c->arg[2]);
        }
 
        if(param & ISO14A_APDU) {
@@ -2031,9 +2027,12 @@ void ReaderMifare(bool first_try)
        uint8_t mf_nr_ar[]   = { 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 };
        static uint8_t mf_nr_ar3;
 
-       uint8_t* receivedAnswer = (((uint8_t *)BigBuf) + RECV_RESP_OFFSET);
-       uint8_t* receivedAnswerPar = (((uint8_t *)BigBuf) + RECV_RESP_PAR_OFFSET);
+       uint8_t receivedAnswer[MAX_MIFARE_FRAME_SIZE];
+       uint8_t receivedAnswerPar[MAX_MIFARE_PARITY_SIZE];
 
+       // free eventually allocated BigBuf memory. We want all for tracing.
+       BigBuf_free();
+       
        iso14a_clear_trace();
        iso14a_set_tracing(TRUE);
 
@@ -2047,8 +2046,8 @@ void ReaderMifare(bool first_try)
        uint32_t nt = 0;
        uint32_t previous_nt = 0;
        static uint32_t nt_attacked = 0;
-       byte_t par_list[8] = {0,0,0,0,0,0,0,0};
-       byte_t ks_list[8] = {0,0,0,0,0,0,0,0};
+       byte_t par_list[8] = {0x00};
+       byte_t ks_list[8] = {0x00};
 
        static uint32_t sync_time;
        static uint32_t sync_cycles;
@@ -2057,8 +2056,6 @@ void ReaderMifare(bool first_try)
        uint16_t consecutive_resyncs = 0;
        int isOK = 0;
 
-
-
        if (first_try) { 
                mf_nr_ar3 = 0;
                iso14443a_setup(FPGA_HF_ISO14443A_READER_MOD);
@@ -2245,10 +2242,10 @@ void Mifare1ksim(uint8_t flags, uint8_t exitAfterNReads, uint8_t arg2, uint8_t *
        struct Crypto1State *pcs;
        pcs = &mpcs;
        uint32_t numReads = 0;//Counts numer of times reader read a block
-       uint8_t* receivedCmd = get_bigbufptr_recvcmdbuf();
-       uint8_t* receivedCmd_par = receivedCmd + MAX_FRAME_SIZE;
-       uint8_t* response = get_bigbufptr_recvrespbuf();
-       uint8_t* response_par = response + MAX_FRAME_SIZE;
+       uint8_t receivedCmd[MAX_MIFARE_FRAME_SIZE];
+       uint8_t receivedCmd_par[MAX_MIFARE_PARITY_SIZE];
+       uint8_t response[MAX_MIFARE_FRAME_SIZE];
+       uint8_t response_par[MAX_MIFARE_PARITY_SIZE];
        
        uint8_t rATQA[] = {0x04, 0x00}; // Mifare classic 1k 4BUID
        uint8_t rUIDBCC1[] = {0xde, 0xad, 0xbe, 0xaf, 0x62};
@@ -2265,6 +2262,8 @@ void Mifare1ksim(uint8_t flags, uint8_t exitAfterNReads, uint8_t arg2, uint8_t *
        uint32_t ar_nr_responses[] = {0,0,0,0,0,0,0,0};
        uint8_t ar_nr_collected = 0;
 
+       // free eventually allocated BigBuf memory but keep Emulator Memory
+       BigBuf_free_keep_EM();
        // clear trace
     iso14a_clear_trace();
        iso14a_set_tracing(TRUE);
@@ -2735,18 +2734,20 @@ void RAMFUNC SniffMifare(uint8_t param) {
        // The command (reader -> tag) that we're receiving.
        // The length of a received command will in most cases be no more than 18 bytes.
        // So 32 should be enough!
-       uint8_t *receivedCmd = (((uint8_t *)BigBuf) + RECV_CMD_OFFSET);
-       uint8_t *receivedCmdPar = ((uint8_t *)BigBuf) + RECV_CMD_PAR_OFFSET;
+       uint8_t receivedCmd[MAX_MIFARE_FRAME_SIZE];
+       uint8_t receivedCmdPar[MAX_MIFARE_PARITY_SIZE];
        // The response (tag -> reader) that we're receiving.
-       uint8_t *receivedResponse = (((uint8_t *)BigBuf) + RECV_RESP_OFFSET);
-       uint8_t *receivedResponsePar = ((uint8_t *)BigBuf) + RECV_RESP_PAR_OFFSET;
+       uint8_t receivedResponse[MAX_MIFARE_FRAME_SIZE];
+       uint8_t receivedResponsePar[MAX_MIFARE_PARITY_SIZE];
 
        // As we receive stuff, we copy it from receivedCmd or receivedResponse
        // into trace, along with its length and other annotations.
        //uint8_t *trace = (uint8_t *)BigBuf;
        
-       // The DMA buffer, used to stream samples from the FPGA
-       uint8_t *dmaBuf = ((uint8_t *)BigBuf) + DMA_BUFFER_OFFSET;
+       // free eventually allocated BigBuf memory
+       BigBuf_free();
+       // allocate the DMA buffer, used to stream samples from the FPGA
+       uint8_t *dmaBuf = BigBuf_malloc(DMA_BUFFER_SIZE);
        uint8_t *data = dmaBuf;
        uint8_t previous_data = 0;
        int maxDataLen = 0;
@@ -2805,7 +2806,7 @@ void RAMFUNC SniffMifare(uint8_t param) {
                // test for length of buffer
                if(dataLen > maxDataLen) {                                      // we are more behind than ever...
                        maxDataLen = dataLen;                                   
-                       if(dataLen > 400) {
+                       if(dataLen > (9 * DMA_BUFFER_SIZE / 10)) {
                                Dbprintf("blew circular buffer! dataLen=0x%x", dataLen);
                                break;
                        }
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