Updating MQTT client example for CryptoAuthLib

examples/common/atecc_get_pubkey.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+
+"""Tool to pull public keys from Microchip ATECC* secure element.
+
+Dependencies installation:
+    pip install cryptoauthlib ecdsa
+
+Usage example:
+    $ python atecc_get_pubkey.py --slot 2
+"""
+
+from cryptoauthlib import *
+from ecdsa import VerifyingKey
+from ecdsa.curves import NIST256p
+
+ATCA_SUCCESS = 0x00
+
+
+def key_to_pem(key_raw):
+    k = VerifyingKey.from_string(key_raw, curve=NIST256p)
+    return k.to_pem()
+
+def hex_str(bytearray):
+    return ''.join(format(x, '02X') for x in bytearray)
+
+if __name__ == '__main__':
+    import argparse
+
+    parser = argparse.ArgumentParser(description='Get the public key from a slot')
+    parser.add_argument('slot', type=int, help='Slot ID')
+    args = parser.parse_args()
+
+    load_cryptoauthlib()
+    assert ATCA_SUCCESS == atcab_init(cfg_ateccx08a_kithid_default())
+
+    key = bytearray(64)
+    assert ATCA_SUCCESS == atcab_get_pubkey(args.slot, key)
+    print("Public key from slot %d: %s" % (args.slot, hex_str(key)))
+    print()
+    print("In PEM format:\n%s" % key_to_pem(key).decode())

examples/common/rules.mk

@@ -48,6 +48,11 @@ IOTC_FLAGS_INCLUDE += $(foreach i,$(IOTC_CLIENT_INC_PATH),-I$i)
 
 IOTC_FLAGS_COMPILER ?= -Wall -Werror -Wno-pointer-arith -Wno-format -fstrict-aliasing -Os -Wextra
 
+# -lm is only needed by linux
+# -lpthread only if both linux and multithreading is enabled in the
+# Google Cloud IoT Device SDK Client at compile time
+IOTC_FLAGS_LINKER := -L$(IOTC_CLIENT_LIB_PATH) -liotc -lm -lpthread
+
 # TLS BSP related configuration
 IOTC_BSP_TLS ?= mbedtls
 
@@ -58,9 +63,21 @@ ifneq ("$(IOTC_BSP_TLS)", "")
 
   TLS_LIB_CONFIG_FLAGS := -L$(addprefix $(IOTC_CLIENT_PATH),$(IOTC_TLS_LIB_DIR))
   TLS_LIB_CONFIG_FLAGS += $(foreach d, $(IOTC_TLS_LIB_NAME), -l$d)
+  IOTC_FLAGS_LINKER += $(TLS_LIB_CONFIG_FLAGS)
 endif
 
-# -lm is only needed by linux
-# -lpthread only if both linux and multithreading is enabled in the
-# Google Cloud IoT EmbeddedC Client at compile time
-IOTC_FLAGS_LINKER := -L$(IOTC_CLIENT_LIB_PATH) -liotc -lpthread $(TLS_LIB_CONFIG_FLAGS) -lm
+# Crypto BSP related configuration
+IOTC_BSP_CRYPTO ?= mbedtls
+
+ifeq ("$(IOTC_BSP_CRYPTO)", "cryptoauthlib")
+  IOTC_FLAGS_INCLUDE += -I$(addprefix $(IOTC_CLIENT_PATH), third_party/cryptoauthlib/lib)
+  CRYPTO_LIB_CONFIG_FLAGS := -L$(addprefix $(IOTC_CLIENT_PATH), third_party/cryptoauthlib/build)
+  CRYPTO_LIB_CONFIG_FLAGS += -lcryptoauth
+  IOTC_FLAGS_LINKER += $(CRYPTO_LIB_CONFIG_FLAGS)
+
+  # For a secure element connected via USB
+  IOTC_FLAGS_LINKER += -ludev -lusb -lusb-1.0
+
+  # For selectively enabling Cryptoauthlib in the examples
+  IOTC_FLAGS_COMPILER += -DENABLE_CRYPTOAUTHLIB=1
+endif

examples/common/src/commandline.c

@@ -43,15 +43,22 @@ const char* iotc_publish_topic;
 const char* iotc_publish_message;
 const char* iotc_private_key_filename;
 
+#ifdef ENABLE_CRYPTOAUTHLIB
+uint8_t iotc_private_key_slot;
+#endif
+
 int iotc_parse(int argc, char** argv, char* valid_options,
                unsigned options_length) {
   int c;
   int iotc_help_flag = 0;
   iotc_project_id = NULL;
   iotc_device_path = NULL;
   iotc_publish_topic = NULL;
-  iotc_private_key_filename = DEFAULT_PRIVATE_KEY_FIILENAME;
   iotc_publish_message = "Hello From Your IoTC client!";
+  iotc_private_key_filename = DEFAULT_PRIVATE_KEY_FIILENAME;
+#ifdef ENABLE_CRYPTOAUTHLIB
+  iotc_private_key_slot = 0xFF;
+#endif
 
   while (1) {
     static struct option long_options[] = {
@@ -61,6 +68,9 @@ int iotc_parse(int argc, char** argv, char* valid_options,
         {"publish_topic", required_argument, 0, 't'},
         {"publish_message", required_argument, 0, 'm'},
         {"private_key_filename", optional_argument, 0, 'f'},
+#ifdef ENABLE_CRYPTOAUTHLIB
+        {"private_key_slot", required_argument, 0, 's'},
+#endif
         {0, 0, 0, 0}};
 
     /* getopt_long stores the option index here. */
@@ -89,6 +99,11 @@ int iotc_parse(int argc, char** argv, char* valid_options,
       case 'f':
         iotc_private_key_filename = optarg;
         break;
+#ifdef ENABLE_CRYPTOAUTHLIB
+      case 's':
+        iotc_private_key_slot = (uint8_t) strtol(optarg, NULL, 10);
+        break;
+#endif
       case 'h':
       default:
         iotc_help_flag = 1;
@@ -155,6 +170,12 @@ void iotc_usage(const char* options, unsigned options_length) {
         printf(" \t of the device identifying private_key. Defaults to: %s\n",
                DEFAULT_PRIVATE_KEY_FIILENAME);
         break;
+#ifdef ENABLE_CRYPTOAUTHLIB
+      case 's':
+        printf(
+            "-s --private_key_slot\n\tThe secure element slot ID containing "
+            "\tthe device identifying private_key.");
+#endif
       case 'h': /* Don't print anything for the help option since we're printing
                    usage */
         break;

examples/common/src/commandline.h

@@ -17,7 +17,7 @@
 /*
  * This module implements a command line argument parser.
  */
-
+#include <stdint.h>
 #include <iotc_mqtt.h>
 
 /* Flags set by commandline arguments. */
@@ -30,5 +30,9 @@ extern const char* iotc_publish_topic;
 extern const char* iotc_publish_message;
 extern const char* iotc_private_key_filename;
 
+#ifdef ENABLE_CRYPTOAUTHLIB
+extern uint8_t iotc_private_key_slot;
+#endif
+
 int iotc_parse(int argc, char** argv, char* valid_options,
                const unsigned options_length);

examples/common/src/example_utils.c

@@ -20,6 +20,11 @@
 #include "example_utils.h"
 #include "commandline.h"
 
+#ifdef ENABLE_CRYPTOAUTHLIB
+#include "cryptoauthlib.h"
+#endif
+
+
 #define IOTC_UNUSED(x) (void)(x)
 
 extern iotc_crypto_key_data_t iotc_connect_private_key_data;
@@ -28,7 +33,13 @@ static iotc_timed_task_handle_t delayed_publish_task =
     IOTC_INVALID_TIMED_TASK_HANDLE;
 
 int iotc_example_handle_command_line_args(int argc, char* argv[]) {
+
+#ifdef ENABLE_CRYPTOAUTHLIB
+  char options[] = "h:p:d:t:m:f:s:";
+#else
   char options[] = "h:p:d:t:m:f:";
+#endif
+
   int missingparameter = 0;
   int retval = 0;
 
@@ -62,6 +73,13 @@ int iotc_example_handle_command_line_args(int argc, char* argv[]) {
     printf("-t --publish_topic is required\n");
   }
 
+#ifdef ENABLE_CRYPTOAUTHLIB
+  if (0xFF == iotc_private_key_slot) {
+    missingparameter = 1;
+    printf("-s --private_key_slot is required\n");
+  }
+#endif
+
   if (1 == missingparameter) {
     /* Error has already been logged, above.  Silently exit here */
     printf("\n");
@@ -110,6 +128,20 @@ int load_ec_private_key_pem_from_posix_fs(char* buf_ec_private_key_pem, size_t b
   return 0;
 }
 
+#ifdef ENABLE_CRYPTOAUTHLIB
+int init_cryptoauthlib() {
+  ATCA_STATUS atca_status;
+  if ((atca_status = atcab_init(&cfg_ateccx08a_kithid_default)) != ATCA_SUCCESS) {
+      printf("Unable to initialize interface, status: %x\n", atca_status);
+      return -1;
+  } else {
+    printf("Successfully initialized secure element.\n");
+  }
+
+  return 0;
+}
+#endif
+
 void on_connection_state_changed(iotc_context_handle_t in_context_handle,
                                  void* data, iotc_state_t state) {
   iotc_connection_data_t* conn_data = (iotc_connection_data_t*)data;

examples/common/src/example_utils.h

@@ -32,6 +32,15 @@ int iotc_example_handle_command_line_args(int argc, char* argv[]);
    also be used. Please see the Crypto BSP for more information. */
 int load_ec_private_key_pem_from_posix_fs(char* buf_ec_private_key_pem, size_t buf_len);
 
+#ifdef ENABLE_CRYPTOAUTHLIB
+/**
+ * Initializes Microchip's Cryptoauthlib.
+ *
+ * Used to sign tokens using the private key stored in a secure element.
+ */
+int init_cryptoauthlib();
+#endif
+
 /* A callback function that will be invoked whenever the connection state
    has changed.
 

examples/iot_core_mqtt_client/src/iot_core_mqtt_client.c

@@ -46,14 +46,20 @@ int main(int argc, char* argv[]) {
     return -1;
   }
 
-  /* This example assumes the private key to be used to  sign the IoT Core
-     Connect JWT credential is a PEM encoded ES256 private key,
-     and passes it IoT Core Device Client functions as a byte array.
-     There are other ways of passing key data to the client, including
-     passing Key Slot IDs for using keys stored in secure elements.
+  /* This example assumes the key used to sign the IoT Core
+     Connect JWT credential is an ES256 private key.
+     It demonstrates two ways of passing the key:
+      - from a PEM encoded string in a byte array
+      - from a key stored in a secure element
+
+     This behaviour can be selected using the ENABLE_CRYPTOAUTHLIB
+     preprocessor variable.
      For more information, please see the iotc_crypto_key_data_t
      documentation in include/iotc_types.h. */
 
+#ifndef ENABLE_CRYPTOAUTHLIB
+  /* Using a private key in PEM format. */
+
   /* Use the example utils function to load the key from disk into memory. */
   if (0 != load_ec_private_key_pem_from_posix_fs(ec_private_key_pem,
                                                  PRIVATE_KEY_BUFFER_SIZE)) {
@@ -71,6 +77,19 @@ int main(int argc, char* argv[]) {
   iotc_connect_private_key_data.crypto_key_union.key_pem.key =
       ec_private_key_pem;
 
+#else
+  /* Using a private key stored in a secure element. */
+
+  init_cryptoauthlib(); // Initialize the secure element
+
+  iotc_connect_private_key_data.crypto_key_signature_algorithm =
+      IOTC_CRYPTO_KEY_SIGNATURE_ALGORITHM_ES256;
+  iotc_connect_private_key_data.crypto_key_union_type =
+      IOTC_CRYPTO_KEY_UNION_TYPE_SLOT_ID;
+  iotc_connect_private_key_data.crypto_key_union.key_slot.slot_id =
+      iotc_private_key_slot;
+#endif
+
   /* Initialize iotc library and create a context to use to connect to the
    * GCP IoT Core Service. */
   const iotc_state_t error_init = iotc_initialize();

make/mt-config/mt-crypto.mk

@@ -38,7 +38,7 @@ $(CRYPTOAUTHLIB_BUILD_DIR):
 	mkdir -p $(CRYPTOAUTHLIB_BUILD_DIR)
 
 $(CRYPTOAUTHLIB_MAKEFILE): | $(CRYPTOAUTHLIB_BUILD_DIR)
-	cmake -B$(CRYPTOAUTHLIB_BUILD_DIR) -H$(CRYPTOAUTHLIB_DIR) 
+	cmake -B$(CRYPTOAUTHLIB_BUILD_DIR) -H$(CRYPTOAUTHLIB_DIR) -DATCA_BUILD_SHARED_LIBS=OFF
 
 $(CRYPTOAUTHLIB_LIBRARY): | $(CRYPTOAUTHLIB_MAKEFILE)
 	make -C $(CRYPTOAUTHLIB_BUILD_DIR)