Drone access restriction by using NFC Tags

/**
 * @file quick_start_example1.c
 * @brief Quick start example that presents how to use libnfc
 */

// To compile this simple example:
// gcc -o MIFARE_Ultralight_read MIFARE_Ultralight_read.c -lnfc

#include <stdio.h>
#include <stdlib.h>
#include <nfc/nfc.h>
#include <string.h>


const char* getfield(char* line, int num)
{
    const char* tok;
    for (tok = strtok(line, ";");
            tok && *tok;
            tok = strtok(NULL, ";\n"))
    {
        if (!--num)
            return tok;
    }
    return NULL;
}

static void
print_hex(const uint8_t *pbtData, const size_t szBytes)
{
  size_t  szPos;

  for (szPos = 0; szPos < szBytes; szPos++) {
    printf("%02x  ", pbtData[szPos]);
  }
  printf("\n");
}

int
main(int argc, const char *argv[])
{
  nfc_device *pnd;
  nfc_target nt;

  // Allocate only a pointer to nfc_context
  nfc_context *context;

  // Initialize libnfc and set the nfc_context
  nfc_init(&context);
  if (context == NULL) {
    printf("Unable to init libnfc (malloc)\n");
    exit(EXIT_FAILURE);
  }

  // Display libnfc version
  const char *acLibnfcVersion = nfc_version();
  (void)argc;
  printf("%s uses libnfc %s\n", argv[0], acLibnfcVersion);

  // Open, using the first available NFC device which can be in order of selection:
  //   - default device specified using environment variable or
  //   - first specified device in libnfc.conf (/etc/nfc) or
  //   - first specified device in device-configuration directory (/etc/nfc/devices.d) or
  //   - first auto-detected (if feature is not disabled in libnfc.conf) device
  pnd = nfc_open(context, NULL);

  if (pnd == NULL) {
    printf("ERROR: %s\n", "Unable to open NFC device.");
    exit(EXIT_FAILURE);
  }
  // Set opened NFC device to initiator mode
  if (nfc_initiator_init(pnd) < 0) {
    nfc_perror(pnd, "nfc_initiator_init");
    exit(EXIT_FAILURE);
  }

  printf("NFC reader: %s opened\n", nfc_device_get_name(pnd));

  // Poll for a ISO14443A (MIFARE) tag
  const size_t szModulations = 1;
  const nfc_modulation nmMifare[1] = {
	{    .nmt = NMT_ISO14443A, .nbr = NBR_106}
  };


  printf("Polling for target...\n");
  //  while (nfc_initiator_select_passive_target(pnd, nmMifare, NULL, 0, &nt) <= 0);
  while(nfc_initiator_poll_target(pnd, nmMifare, szModulations, 0xFF, 0x05, &nt) <= 0);
 
 printf("Target detected!\n");


  printf("Tag UID: ");
  char curuid[15];
  if(nt.nti.nai.szUidLen == 7) sprintf (curuid,"%02X%02X%02X%02X%02X%02X%02X", nt.nti.nai.abtUid[0],nt.nti.nai.abtUid[1],nt.nti.nai.abtUid[2],nt.nti.nai.abtUid[3],nt.nti.nai.abtUid[4],nt.nti.nai.abtUid[5],nt.nti.nai.abtUid[6]);
  else if (nt.nti.nai.szUidLen == 4) sprintf (curuid,"%02X%02X%02X%02X", nt.nti.nai.abtUid[0],nt.nti.nai.abtUid[1],nt.nti.nai.abtUid[2],nt.nti.nai.abtUid[3]);
  else return 0; //No valid UID found

  printf("%s\n", curuid);


  //Read UID file and check if UID is there
  FILE* stream = fopen("/home/navq/nfc_example/uids.csv", "r");

  printf("Check if UID is in CSV file...\n");

    char line[128];
    while (fgets(line, 128, stream))
    {
        const char* uid = getfield(strdup(line), 1);
	const char* script = getfield(strdup(line), 2);

        if(strcmp(uid,curuid)==0)
	{
	  printf("UID found: %s\n", uid); 
	  //UID was found!
	  char command[120];
    	  sprintf(command,"%s%s", "sudo -u navq ", script);
	  int status = system(command);
	  printf("Run Command: %s\n",command);
	}
    }


 // int status = system("sudo -u navq ./test.sh");

/*
    printf("The following (NFC) ISO14443A tag was found:\n");
    printf("    ATQA (SENS_RES): ");
    print_hex(nt.nti.nai.abtAtqa, 2);
    printf("       UID (NFCID%c): ", (nt.nti.nai.abtUid[0] == 0x08 ? '3' : '1'));
    print_hex(nt.nti.nai.abtUid, nt.nti.nai.szUidLen);
    printf("      SAK (SEL_RES): ");
    print_hex(&nt.nti.nai.btSak, 1);
    if (nt.nti.nai.szAtsLen) {
      printf("          ATS (ATR): ");
      print_hex(nt.nti.nai.abtAts, nt.nti.nai.szAtsLen);
    }
  */


  // Close NFC device
  nfc_close(pnd);
  // Release the context
  nfc_exit(context);
  exit(EXIT_SUCCESS);
}