commit 67e2c550b2fa9603d148330b208317a7f3d33270
Author: Valentin Ochs <a@0au.de>
Date:   Sun Feb 21 23:35:53 2021 +0100

    Initial commit

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..2b5dce6
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+*.o
+*.d
+.ccls-cache
+key
+poll_desfire
+compile_commands.json
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..8b5a59d
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,9 @@
+CFLAGS += -Wall -pedantic --std=c99 $(shell pkg-config --cflags libfreefare) -g -O0 -D_POSIX_C_SOURCE=200809L
+LDFLAGS += $(shell pkg-config --libs libfreefare)
+
+all: poll_desfire
+
+clean:
+	rm -f poll_desfire *.o
+
+.PHONY: all clean
diff --git a/poll_desfire.c b/poll_desfire.c
new file mode 100644
index 0000000..3f4f568
--- /dev/null
+++ b/poll_desfire.c
@@ -0,0 +1,129 @@
+#include <err.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.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;
+
+  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)");
+  }
+
+  uint8_t const key_data_null[8]  = {0, 0, 0, 0, 0, 0, 0, 0};
+  MifareDESFireKey key_null = mifare_desfire_des_key_new_with_version(key_data_null);
+
+  uint8_t key_data_real[16] = {0};
+  {
+    FILE *f = fopen("key", "rb");
+    if (!f) {
+      errx(EXIT_FAILURE, "error opening key file.");
+    }
+    if (fread(key_data_real, 1, sizeof key_data_real, f) < sizeof key_data_real) {
+      errx(EXIT_FAILURE, "key file too small.");
+    }
+    fclose(f);
+  }
+  MifareDESFireKey key_real = mifare_desfire_aes_key_new(key_data_real);
+
+  device_count = nfc_list_devices(context, devices, sizeof(devices) / sizeof(devices[0]));
+  if (device_count <= 0) {
+    errx(EXIT_FAILURE, "No NFC device found.");
+  }
+
+  if (device_count > 1) {
+    printf("More than 1 device available. Using %s\n", devices[0]);
+  }
+
+  device = nfc_open(context, devices[0]);
+  if (!device) {
+    errx(EXIT_FAILURE, "nfc_open() failed.");
+  }
+
+  if (nfc_initiator_init(device) < 0) {
+    errx(EXIT_FAILURE, "Initiator failed.");
+  }
+
+  while (true) {
+    /* Poll for targets */
+    const nfc_modulation nmModulations = {.nmt = NMT_ISO14443A, .nbr = NBR_106};
+    nfc_target target;
+    nfc_initiator_poll_target(device, &nmModulations, 1, 0x10, 1, &target);
+
+    /* Got at least one, read tag list */
+    tags = freefare_get_tags(device);
+    if (!tags) {
+      nfc_close(device);
+      errx(EXIT_FAILURE, "Error listing tags.");
+    }
+
+    if (!tags[0]) {
+      printf("Tag list returned no tags\n");
+      goto free_tags;
+    }
+
+    FreefareTag tag = tags[0];
+    if (MIFARE_DESFIRE != freefare_get_tag_type(tag))
+      goto free_tags;
+
+    char *tag_uid = freefare_get_tag_uid(tag);
+
+    /* Result of various operations */
+    int res;
+
+    res = mifare_desfire_connect(tag);
+    if (res < 0) {
+      warnx("Can't connect to Mifare DESFire target.");
+      goto free_tag;
+    }
+
+    res = mifare_desfire_authenticate(tag, 0, key_null);
+    if (res >= 0) {
+      // Default key still active, create new key
+      res = mifare_desfire_change_key(tag, 0, key_real, key_null);
+
+      if (res < 0) {
+        warnx("Error changing key");
+        goto free_tag;
+      }
+    }
+
+    res = mifare_desfire_authenticate_aes(tag, 0, key_real);
+    if (res < 0) {
+      warnx("Authentication on master application failed");
+      goto free_tag;
+    } else {
+      printf("Valid key: %s\n", tag_uid);
+    }
+
+  wait_disconnect:
+    while (0 == nfc_initiator_target_is_present(device, 0))
+      ;
+    mifare_desfire_disconnect(tag);
+
+  free_tag:
+    free(tag_uid);
+  free_tags:
+    freefare_free_tags(tags);
+
+  }
+
+  mifare_desfire_key_free(key_null);
+  mifare_desfire_key_free(key_real);
+
+  nfc_close(device);
+  nfc_exit(context);
+
+  exit(error);
+}