libfreefare/examples/ntag-setauth.c

/*-
 * Copyright (C) 2012, 2017 Romain Tartiere, Martin Dagarin (SloCompTech).
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 */
#include <err.h>
#include <stdlib.h>

#include <nfc/nfc.h>

#include <freefare.h>


int
main(int argc, char *argv[])
{
    int error = EXIT_SUCCESS;
    nfc_device *device = NULL;
    FreefareTag *tags = NULL;

    if (argc > 1)
	errx(EXIT_FAILURE, "usage: %s", argv[0]);

    nfc_connstring devices[8];
    size_t device_count;

    nfc_context *context;
    nfc_init (&context);
    if (context == NULL)
	errx(EXIT_FAILURE, "Unable to init libnfc (malloc)");

    device_count = nfc_list_devices (context, devices, sizeof (devices) / sizeof (*devices));
    if (device_count <= 0)
	errx(EXIT_FAILURE, "No NFC device found");

    for (size_t d = 0; d < device_count; d++) {
	if (!(device = nfc_open (context, devices[d]))) {
	    warnx("nfc_open() failed.");
	    error = EXIT_FAILURE;
	    continue;
	}

	if (!(tags = freefare_get_tags (device))) {
	    nfc_close(device);
	    errx(EXIT_FAILURE, "Error listing tags.");
	}

	for (int i = 0; (!error) && tags[i]; i++) {
	    switch (freefare_get_tag_type(tags[i])) {
	    case NTAG_21x:
		break;
	    default:
		continue;
	    }

	    char *tag_uid = freefare_get_tag_uid(tags[i]);
	    printf("Tag with UID %s is a %s\n", tag_uid, freefare_get_tag_friendly_name(tags[i]));
	    FreefareTag tag = tags[i];
	    int res;
	    if (ntag21x_connect (tag) < 0)
		errx(EXIT_FAILURE, "Error connecting to tag.");

	    uint8_t pwd[4] = {0xff,0xff,0xff,0xff};
	    uint8_t pack[2] = {0xaa,0xaa};

	    NTAG21xKey key;
	    key = ntag21x_key_new(pwd,pack); // Creating key

	    uint8_t auth0 = 0x00; // Buffer for auth0 byte
	    uint8_t authlim = 0x00;
	    switch (true) {
	    case true:
		/*
		   Get information about tag
		   MUST do, because here we are recognizing tag subtype (NTAG213,NTAG215,NTAG216), and gathering all parameters
		   */
		res = ntag21x_get_info(tag);
		if(res < 0) {
		    printf("Error getting info from tag\n");
		    break;
		}
		// Get auth byte from tag
		res = ntag21x_get_auth(tag,&auth0);
		if(res < 0) {
		    printf("Error getting auth0 byte from tag\n");
		    break;
		}
		printf("Old auth0: %#02x\n",auth0);
		res = ntag21x_get_authentication_limit(tag,&authlim);
		if(res < 0) {
		    printf("Error getting auth0 byte from tag\n");
		    break;
		}
		printf("Authlim: %#02x\n",authlim);
		// Check if auth is required to set pwd and pack
		if(auth0 < ntag21x_get_last_page(tag) - 2) { // Check if last 2 pages are protected
		    printf("Error: pwd and PACK sections are protected with unknown password\n");
		    break;
		}
		// Set key
		res = ntag21x_set_key(tag,key);
		if(res < 0) {
		    printf("Error setting key tag\n");
		    break;
		}
		// Protect last 6 pages !! It can be hacked if you don't protect last 4 pages where auth0 byte is located
		res = ntag21x_set_auth(tag,ntag21x_get_last_page(tag)-5);
		if(res < 0) {
		    printf("Error setting auth0 byte \n");
		    break;
		}
		// Enable read & write pwd protection (default: write only protection)
		res = ntag21x_access_enable(tag,NTAG_PROT);
		if(res < 0) {
		    printf("Error setting access byte \n");
		    break;
		}
		// Get auth byte from tag
		res = ntag21x_get_auth(tag,&auth0);
		if(res < 0) {
		    printf("Error getting auth0 byte from tag\n");
		    break;
		}
		printf("New auth0: %#02x\n",auth0);
	    }
	    ntag21x_disconnect (tag);
	    ntag21x_key_free(key); // Delete key
	    free (tag_uid);
	}
	freefare_free_tags(tags);
	nfc_close(device);
    }
    nfc_exit(context);
    exit(error);
}