generate_nrfconnect_chip_factory_data.py

#!/usr/bin/env python3
#
#    Copyright (c) 2022 Project CHIP Authors
#
#    Licensed under the Apache License, Version 2.0 (the "License");
#    you may not use this file except in compliance with the License.
#    You may obtain a copy of the License at
#
#        http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS,
#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#    See the License for the specific language governing permissions and
#    limitations under the License.
#

from os.path import exists
import os
import sys
import json
import jsonschema
import secrets
import argparse
import subprocess
import logging as log
import base64
from collections import namedtuple
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.serialization import load_der_private_key

# A user can not change the factory data version and must be coherent with
# the factory data version set in the nRF Connect platform Kconfig file (CHIP_FACTORY_DATA_VERSION).
FACTORY_DATA_VERSION = 1

MATTER_ROOT = os.path.dirname(os.path.realpath(__file__))[:-len("/scripts/tools/nrfconnect")]
HEX_PREFIX = "hex:"
PUB_KEY_PREFIX = b'\x04'
INVALID_PASSCODES = [00000000, 11111111, 22222222, 33333333, 44444444,
                     55555555, 66666666, 77777777, 88888888, 99999999, 12345678, 87654321]


def get_raw_private_key_der(der_file: str, password: str):
    """ Split given der file to get separated key pair consisting of public and private keys.

    Args:
        der_file (str): Path to .der file containing public and private keys
        password (str): Password to decrypt Keys. It can be None, and then KEY is not encrypted.

    Returns:
        hex string: return a hex string containing extracted and decrypted private KEY from given .der file.
    """
    try:
        with open(der_file, 'rb') as file:
            key_data = file.read()
            if password is None:
                log.warning("KEY password has not been provided. It means that DAC key is not encrypted.")
            keys = load_der_private_key(key_data, password, backend=default_backend())
            private_key = keys.private_numbers().private_value.to_bytes(32, byteorder='big')

            return private_key

    except IOError or ValueError:
        return None


def gen_test_certs(chip_cert_exe: str,
                   output: str,
                   vendor_id: int,
                   product_id: int,
                   device_name: str,
                   generate_cd: bool = False,
                   cd_type: int = 1,
                   paa_cert_path: str = None,
                   paa_key_path: str = None):
    """
    Generate Matter certificates according to given Vendor ID and Product ID using the chip-cert executable.
    To use own Product Attestation Authority certificate provide paa_cert_path and paa_key_path arguments.
    Without providing these arguments a PAA certificate will be get from /credentials/test/attestation directory
    in the Matter repository.

    Args:
        chip_cert_exe (str): path to chip-cert executable
        output (str): output path to store a newly generated certificates (CD, DAC, PAI)
        vendor_id (int): an identification number specific to Vendor
        product_id (int): an identification number specific to Product
        device_name (str): human-readable device name
        generate_cd (bool, optional): Generate Certificate Declaration and store it in thee output directory. Defaults to False.
        paa_cert_path (str, optional): provide PAA certification path. Defaults to None - a path will be set to /credentials/test/attestation directory.
        paa_key_path (str, optional): provide PAA key path. Defaults to None - a path will be set to /credentials/test/attestation directory.

    Returns:
        dictionary: ["PAI_CERT": (str)<path to PAI cert .der file>, 
                     "DAC_CERT": (str)<path to DAC cert .der file>,
                     "DAC_KEY": (str)<path to DAC key .der file>]
    """

    CD_PATH = MATTER_ROOT + "/credentials/test/certification-declaration/Chip-Test-CD-Signing-Cert.pem"
    CD_KEY_PATH = MATTER_ROOT + "/credentials/test/certification-declaration/Chip-Test-CD-Signing-Key.pem"
    PAA_PATH = paa_cert_path if paa_cert_path != None else MATTER_ROOT + "/credentials/test/attestation/Chip-Test-PAA-NoVID-Cert.pem"
    PAA_KEY_PATH = paa_key_path if paa_key_path != None else MATTER_ROOT + "/credentials/test/attestation/Chip-Test-PAA-NoVID-Key.pem"

    attestation_certs = namedtuple("attestation_certs", ["dac_cert", "dac_key", "pai_cert"])

    log.info("Generating new certificates using chip-cert...")

    if generate_cd:
        # generate Certification Declaration
        cmd = [chip_cert_exe, "gen-cd",
               "--key", CD_KEY_PATH,
               "--cert", CD_PATH,
               "--out", output + "/CD.der",
               "--format-version",  "1",
               "--vendor-id",  hex(vendor_id),
               "--product-id",  hex(product_id),
               "--device-type-id", "0",
               "--certificate-id", "FFFFFFFFFFFFFFFFFFF",
               "--security-level",  "0",
               "--security-info",  "0",
               "--certification-type",  str(cd_type),
               "--version-number", "0xFFFF",
               ]
        subprocess.run(cmd)

    new_certificates = {"PAI_CERT": output + "/PAI_cert",
                        "PAI_KEY": output + "/PAI_key",
                        "DAC_CERT": output + "/DAC_cert",
                        "DAC_KEY": output + "/DAC_key"
                        }

    # generate PAI
    cmd = [chip_cert_exe, "gen-att-cert",
           "-t", "i",
           "-c", device_name,
           "-V", hex(vendor_id),
           "-C", PAA_PATH,
           "-K", PAA_KEY_PATH,
           "-o", new_certificates["PAI_CERT"] + ".pem",
           "-O", new_certificates["PAI_KEY"] + ".pem",
           "-l", str(10000),
           ]
    subprocess.run(cmd)

    # generate DAC
    cmd = [chip_cert_exe, "gen-att-cert",
           "-t", "d",
           "-c", device_name,
           "-V", hex(vendor_id),
           "-P", hex(product_id),
           "-C", new_certificates["PAI_CERT"] + ".pem",
           "-K", new_certificates["PAI_KEY"] + ".pem",
           "-o", new_certificates["DAC_CERT"] + ".pem",
           "-O", new_certificates["DAC_KEY"] + ".pem",
           "-l", str(10000),
           ]
    subprocess.run(cmd)

    # convert to .der files
    for cert_k, cert_v in new_certificates.items():
        action_type = "convert-cert" if cert_k.find("CERT") != -1 else "convert-key"
        log.info(cert_v + ".der")
        cmd = [chip_cert_exe, action_type,
               cert_v + ".pem",
               cert_v + ".der",
               "--x509-der",
               ]
        subprocess.run(cmd)

    return attestation_certs(new_certificates["DAC_CERT"] + ".der",
                             new_certificates["DAC_KEY"] + ".der",
                             new_certificates["PAI_CERT"] + ".der")


def gen_spake2p_verifier(passcode: int, it: int, salt: bytes) -> str:
    """ Generate Spake2+ verifier using SPAKE2+ Python Tool

    Args:
        passcode (int): Pairing passcode using in Spake2+
        it (int): Iteration counter for Spake2+ verifier generation
        salt (str): Salt used to generate Spake2+ verifier

    Returns:
        verifier encoded in Base64
    """

    cmd = [
        os.path.join(MATTER_ROOT, 'scripts/tools/spake2p/spake2p.py'), 'gen-verifier',
        '--passcode', str(passcode),
        '--salt', base64.b64encode(salt).decode('ascii'),
        '--iteration-count', str(it),
    ]
    return subprocess.check_output(cmd)


class FactoryDataGenerator:
    """
    Class to generate factory data from given arguments and generate a JSON file

    """

    def __init__(self, arguments) -> None:
        """
        Args:
            arguments (any):All input arguments parsed using ArgParse
        """
        self._args = arguments
        self._factory_data = list()
        self._user_data = dict()

        try:
            self._validate_args()
        except AssertionError as e:
            log.error(e)
            sys.exit(-1)

    def _validate_args(self):
        if self._args.user:
            try:
                self._user_data = json.loads(self._args.user)
            except json.decoder.JSONDecodeError as e:
                raise AssertionError("Provided wrong user data, this is not a JSON format! {}".format(e))
        assert self._args.spake2_verifier or self._args.passcode, \
            "Cannot find Spake2+ verifier, to generate a new one please provide passcode (--passcode)"
        assert (self._args.chip_cert_path or (self._args.dac_cert and self._args.pai_cert and self._args.dac_key)), \
            "Cannot find paths to DAC or PAI certificates .der files. To generate a new ones please provide a path to chip-cert executable (--chip_cert_path)"
        assert self._args.output.endswith(".json"), \
            "Output path doesn't contain .json file path. ({})".format(self._args.output)
        assert not (self._args.passcode in INVALID_PASSCODES), \
            "Provided invalid passcode!"

    def generate_json(self):
        """
        This function generates JSON data, .json file and validates it.

        To validate generated JSON data a scheme must be provided within script's arguments.

        - In the first part, if the rotating device id unique id has been not provided
          as an argument, it will be created.
        - If user-provided passcode and Spake2+ verifier have been not provided
          as an argument, it will be created using an external script
        - Passcode is not stored in JSON by default. To store it for debugging purposes, add --include_passcode argument.
        - Validating output JSON is not mandatory, but highly recommended.

        """
        # generate missing data if needed
        if not self._args.rd_uid:
            if self._args.generate_rd_uid:
                rd_uid = self._generate_rotating_device_uid()
            else:
                # rotating device ID unique ID was not provided, so do not store it in factory data.
                rd_uid = None
        else:
            rd_uid = HEX_PREFIX + self._args.rd_uid

        if not self._args.spake2_verifier:
            spake_2_verifier = self._generate_spake2_verifier()
        else:
            spake_2_verifier = self._args.spake2_verifier

        # convert salt to bytestring to be coherent with Spake2+ verifier type
        spake_2_salt = self._args.spake2_salt

        if self._args.chip_cert_path:
            certs = gen_test_certs(self._args.chip_cert_path,
                                   self._args.output[:self._args.output.rfind("/")],
                                   self._args.vendor_id,
                                   self._args.product_id,
                                   self._args.vendor_name + "_" + self._args.product_name,
                                   self._args.gen_cd,
                                   self._args.cd_type,
                                   self._args.paa_cert,
                                   self._args.paa_key)
            dac_cert = certs.dac_cert
            pai_cert = certs.pai_cert
            dac_key = certs.dac_key
        else:
            dac_cert = self._args.dac_cert
            dac_key = self._args.dac_key
            pai_cert = self._args.pai_cert

        # try to read DAC public and private keys
        dac_priv_key = get_raw_private_key_der(dac_key, self._args.dac_key_password)
        if dac_priv_key is None:
            log.error("Cannot read DAC keys from : {}".format(dac_key))
            sys.exit(-1)

        try:
            json_file = open(self._args.output, "w+")
        except FileNotFoundError:
            print("Cannot create JSON file in this location: {}".format(self._args.output))
            sys.exit(-1)
        with json_file:
            # serialize data
            self._add_entry("version", FACTORY_DATA_VERSION)
            self._add_entry("sn", self._args.sn)
            self._add_entry("vendor_id", self._args.vendor_id)
            self._add_entry("product_id", self._args.product_id)
            self._add_entry("vendor_name", self._args.vendor_name)
            self._add_entry("product_name", self._args.product_name)
            self._add_entry("product_label", self._args.product_label)
            self._add_entry("part_number", self._args.part_number)
            self._add_entry("date", self._args.date)
            self._add_entry("hw_ver", self._args.hw_ver)
            self._add_entry("hw_ver_str", self._args.hw_ver_str)
            self._add_entry("dac_cert", self._process_der(dac_cert))
            self._add_entry("dac_key", dac_priv_key)
            self._add_entry("pai_cert", self._process_der(pai_cert))
            if self._args.include_passcode:
                self._add_entry("passcode", self._args.passcode)
            self._add_entry("spake2_it", self._args.spake2_it)
            self._add_entry("spake2_salt", spake_2_salt)
            self._add_entry("spake2_verifier", spake_2_verifier)
            self._add_entry("discriminator", self._args.discriminator)
            if rd_uid:
                self._add_entry("rd_uid", rd_uid)
            if self._args.enable_key:
                self._add_entry("enable_key", HEX_PREFIX + self._args.enable_key)
            if self._args.user:
                self._add_entry("user", self._args.user)

            factory_data_dict = dict(self._factory_data)

            json_object = json.dumps(factory_data_dict)
            is_json_valid = True

            if self._args.schema:
                is_json_valid = self._validate_output_json(json_object)
            else:
                log.warning("JSON Schema file has not been provided, the output file can be wrong. Be aware of that.")
            try:
                if is_json_valid:
                    json_file.write(json_object)
            except IOError as e:
                log.error("Cannot save output file into directory: {}".format(self._args.output))

    def _add_entry(self, name: str, value: any):
        """ Add single entry to list of tuples ("key", "value") """
        if(isinstance(value, bytes) or isinstance(value, bytearray)):
            value = HEX_PREFIX + value.hex()
        if value or (isinstance(value, int) and value == 0):
            log.debug("Adding entry '{}' with size {} and type {}".format(name, sys.getsizeof(value), type(value)))
            self._factory_data.append((name, value))

    def _generate_spake2_verifier(self):
        """ If verifier has not been provided in arguments list it should be generated via external script """
        return base64.b64decode(gen_spake2p_verifier(self._args.passcode, self._args.spake2_it, self._args.spake2_salt))

    def _generate_rotating_device_uid(self):
        """ If rotating device unique ID has not been provided it should be generated """
        log.warning("Cannot find rotating device UID in provided arguments list. A new one will be generated.")
        rdu = secrets.token_bytes(16)
        log.info("\n\nThe new rotate device UID: {}\n".format(rdu.hex()))
        return rdu

    def _validate_output_json(self, output_json: str):
        """
        Validate output JSON data with provided .scheme file
        This function will raise error if JSON does not match schema.

        """
        try:
            with open(self._args.schema) as schema_file:
                log.info("Validating JSON with schema...")
                schema = json.loads(schema_file.read())
                validator = jsonschema.Draft202012Validator(schema=schema)
                validator.validate(instance=json.loads(output_json))
        except IOError as e:
            log.error("Provided JSON schema file is wrong: {}".format(self._args.schema))
            return False
        else:
            log.info("Validate OK")
            return True

    def _process_der(self, path: str):
        log.debug("Processing der file...")
        try:
            with open(path, 'rb') as f:
                data = f.read()
                return data
        except IOError as e:
            log.error(e)
            raise e


def main():
    parser = argparse.ArgumentParser(description="NrfConnect Factory Data NVS generator tool")

    def allow_any_int(i): return int(i, 0)
    def base64_str(s): return base64.b64decode(s)

    mandatory_arguments = parser.add_argument_group("Mandatory keys", "These arguments must be provided to generate JSON file")
    optional_arguments = parser.add_argument_group(
        "Optional keys", "These arguments are optional and they depend on the user-purpose")
    parser.add_argument("-s", "--schema", type=str,
                        help="JSON schema file to validate JSON output data")
    parser.add_argument("-o", "--output", type=str, required=True,
                        help="Output path to store .json file, e.g. my_dir/output.json")
    parser.add_argument("-v", "--verbose", action="store_true",
                        help="Run this script with DEBUG logging level")
    parser.add_argument("--include_passcode", action="store_true",
                        help="Include passcode in factory data. By default, it is used only for generating Spake2+ verifier.")
    parser.add_argument("--overwrite", action="store_true",
                        help="If output JSON file exist this argument allows to generate new factory data and overwrite it.")
    # Json known-keys values
    # mandatory keys
    mandatory_arguments.add_argument("--sn", type=str, required=True,
                                     help="[ascii string] Serial number of a device which can be used to identify \
	                                        the serial number field in the Matter certificate structure. \
	                                        Maximum length of serial number is 20 bytes. \
	                                        Strings longer than 20 bytes will be declined in script")
    mandatory_arguments.add_argument("--vendor_id", type=allow_any_int,
                                     help="[int | hex int] Provide Vendor Identification Number")
    mandatory_arguments.add_argument("--product_id", type=allow_any_int,
                                     help="[int | hex int] Provide Product Identification Number")
    mandatory_arguments.add_argument("--vendor_name", type=str,
                                     help="[string] provide human-readable vendor name")
    mandatory_arguments.add_argument("--product_name", type=str,
                                     help="[string] provide human-readable product name")
    mandatory_arguments.add_argument("--date", type=str, required=True,
                                     help="[ascii string] Provide manufacturing date \
                                            A manufacturing date specifies the date that the Node was manufactured. \
	                                        Used format for providing a manufacturing date is ISO 8601 e.g. YYYY-MM-DD.")
    mandatory_arguments.add_argument("--hw_ver", type=allow_any_int, required=True,
                                     help="[int | hex int] Provide hardware version in int format.")
    mandatory_arguments.add_argument("--hw_ver_str", type=str, required=True,
                                     help="[ascii string] Provide hardware version in string format.")
    mandatory_arguments.add_argument("--spake2_it", type=allow_any_int, required=True,
                                     help="[int | hex int] Provide Spake2+ iteration count.")
    mandatory_arguments.add_argument("--spake2_salt", type=base64_str, required=True,
                                     help="[base64 string] Provide Spake2+ salt.")
    mandatory_arguments.add_argument("--discriminator", type=allow_any_int, required=True,
                                     help="[int] Provide BLE pairing discriminator. \
                                     A 12-bit value matching the field of the same name in \
                                     the setup code. Discriminator is used during a discovery process.")

    # optional keys
    optional_arguments.add_argument("--product_label", type=str,
                                    help="[string] provide human-readable product label")
    optional_arguments.add_argument("--part_number", type=str,
                                    help="[string] provide human-readable product number")
    optional_arguments.add_argument("--chip_cert_path", type=str,
                                    help="Generate DAC and PAI certificates instead giving a path to .der files. This option requires a path to chip-cert executable."
                                    "By default you can find chip-cert in connectedhomeip/src/tools/chip-cert directory and build it there.")
    optional_arguments.add_argument("--dac_cert", type=str,
                                    help="[.der] Provide the path to .der file containing DAC certificate.")
    optional_arguments.add_argument("--dac_key", type=str,
                                    help="[.der] Provide the path to .der file containing DAC keys.")
    optional_arguments.add_argument("--generate_rd_uid", action="store_true",
                                    help="Generate a new rotating device unique ID, print it out to console output and store it in factory data.")
    optional_arguments.add_argument("--dac_key_password", type=str,
                                    help="Provide a password to decode dac key. If dac key is not encrypted do not provide this argument.")
    optional_arguments.add_argument("--pai_cert", type=str,
                                    help="[.der] Provide the path to .der file containing PAI certificate.")
    optional_arguments.add_argument("--rd_uid", type=str,
                                    help="[hex string] [128-bit hex-encoded] Provide the rotating device unique ID. If this argument is not provided a new rotating device id unique id will be generated.")
    optional_arguments.add_argument("--passcode", type=allow_any_int,
                                    help="[int | hex] Default PASE session passcode. (This is mandatory to generate Spake2+ verifier).")
    optional_arguments.add_argument("--spake2_verifier", type=base64_str,
                                    help="[base64 string] Provide Spake2+ verifier without generating it.")
    optional_arguments.add_argument("--enable_key", type=str,
                                    help="[hex string] [128-bit hex-encoded] The Enable Key is a 128-bit value that triggers manufacturer-specific action while invoking the TestEventTrigger Command."
                                    "This value is used during Certification Tests, and should not be present on production devices.")
    optional_arguments.add_argument("--user", type=str,
                                    help="[string] Provide additional user-specific keys in JSON format: {'name_1': 'value_1', 'name_2': 'value_2', ... 'name_n', 'value_n'}.")
    optional_arguments.add_argument("--gen_cd", action="store_true", default=False,
                                    help="Generate a new Certificate Declaration in .der format according to used Vendor ID and Product ID. This certificate will not be included to the factory data.")
    optional_arguments.add_argument("--cd_type", type=int, default=1,
                                    help="[int] Type of generated Certification Declaration: 0 - development, 1 - provisional, 2 - official")
    optional_arguments.add_argument("--paa_cert", type=str,
                                    help="Provide a path to the Product Attestation Authority (PAA) certificate to generate the PAI certificate. Without providing it, a testing PAA stored in the Matter repository will be used.")
    optional_arguments.add_argument("--paa_key", type=str,
                                    help="Provide a path to the Product Attestation Authority (PAA) key to generate the PAI certificate. Without providing it, a testing PAA key stored in the Matter repository will be used.")
    args = parser.parse_args()

    if args.verbose:
        log.basicConfig(format='[%(asctime)s][%(levelname)s] %(message)s', level=log.DEBUG)
    else:
        log.basicConfig(format='[%(levelname)s] %(message)s', level=log.INFO)

    # check if json file already exist
    if(exists(args.output) and not args.overwrite):
        log.error("Output file: {} already exist, to create a new one add argument '--overwrite'. By default overwriting is disabled".format(args.output))
        return

    generator = FactoryDataGenerator(args)
    generator.generate_json()


if __name__ == "__main__":
    main()