#!/usr/bin/env python
# Copyright 2020 Espressif Systems (Shanghai) Co., Ltd.
# 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.
import argparse
import os
import sys
import hashlib
import hmac
import struct
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.utils import int_to_bytes

try:
    import esptool
    import espefuse
except ImportError:
    idf_path = os.getenv("IDF_PATH")
    if not idf_path or not os.path.exists(idf_path):
        raise Exception("IDF_PATH not found")
    sys.path.insert(0, os.path.join(idf_path, "components", "esptool_py", "esptool"))
    import esptool
    import espefuse
try:
    import nvs_partition_gen as nvs_gen
except ImportError:
    idf_path = os.getenv("IDF_PATH")
    if not idf_path or not os.path.exists(idf_path):
        raise Exception("IDF_PATH not found")
    sys.path.insert(0, os.path.join(idf_path, "components", "nvs_flash", "nvs_partition_generator"))
    import nvs_partition_gen as nvs_gen


esp_ds_data_dir = 'esp_ds_data'
# hmac_key_file is generated when HMAC_KEY is calculated, it is used when burning HMAC_KEY to efuse
hmac_key_file = esp_ds_data_dir + '/hmac_key.bin'
# csv and bin filenames are default filenames for nvs partition files created with this script
csv_filename = esp_ds_data_dir + '/pre_prov.csv'
bin_filename = esp_ds_data_dir + '/pre_prov.bin'


def load_privatekey(key_file_path, password=None):
    key_file = open(key_file_path, 'rb')
    key = key_file.read()
    key_file.close()
    return serialization.load_pem_private_key(key, password=password, backend=default_backend())


def number_as_bytes(number, pad_bits=None):
    """
    Given a number, format as a little endian array of bytes
    """
    result = int_to_bytes(number)[::-1]
    while pad_bits is not None and len(result) < (pad_bits // 8):
        result += b'\x00'
    return result


def calculate_ds_parameters(privkey, priv_key_pass):
    private_key = load_privatekey(privkey, priv_key_pass)
    if not isinstance(private_key, rsa.RSAPrivateKey):
        print("Only RSA private keys are supported")
        sys.exit(-1)

    priv_numbers = private_key.private_numbers()
    pub_numbers = private_key.public_key().public_numbers()
    Y = priv_numbers.d
    M = pub_numbers.n
    key_size = private_key.key_size
    supported_key_size = [1024, 2048, 3072, 4096]
    if key_size not in supported_key_size:
        print("Key size not supported, supported sizes are" + str(supported_key_size))
        sys.exit(-1)

    hmac_key = os.urandom(32)
    with open(hmac_key_file, 'wb') as key_file:
        key_file.write(hmac_key)

    iv = os.urandom(16)

    rr = 1 << (key_size * 2)
    rinv = rr % pub_numbers.n
    mprime = - rsa._modinv(M, 1 << 32)
    mprime &= 0xFFFFFFFF
    length = key_size // 32 - 1

    aes_key = hmac.HMAC(hmac_key, b"\xFF" * 32, hashlib.sha256).digest()

    md_in = number_as_bytes(Y, 4096) + \
        number_as_bytes(M, 4096) + \
        number_as_bytes(rinv, 4096) + \
        struct.pack("<II", mprime, length) + \
        iv
    assert len(md_in) == 12480 / 8
    md = hashlib.sha256(md_in).digest()

    # Y4096 || M4096 || Rb4096 || M_prime32 || LENGTH32 || MD256 || 0x08*8
    p = number_as_bytes(Y, 4096) + \
        number_as_bytes(M, 4096) + \
        number_as_bytes(rinv, 4096) + \
        md + \
        struct.pack("<II", mprime, length) + \
        b'\x08' * 8

    assert len(p) == 12672 / 8

    cipher = Cipher(algorithms.AES(aes_key), modes.CBC(iv), backend=default_backend())
    encryptor = cipher.encryptor()
    c = encryptor.update(p) + encryptor.finalize()
    return c, iv, key_size


class DefineArgs(object):
    def __init__(self, attributes):
        for key, value in attributes.items():
            self.__setattr__(key, value)


def efuse_summary(esp,args):
    efuses, _efuse_operations = espefuse.get_efuses(esp, esp.CHIP_NAME, False, False, False)

    summary_args = DefineArgs({
        'baud': 115200,
        'before': 'default_reset',
        'chip': esp.CHIP_NAME,
        'debug': False,
        'do_not_confirm': False,
        'file': sys.stdout,
        'mode':'w',
        'encding': 'utf-8',
        'format': 'summary',
        'operation': 'summary',
        'port':args.port,
    })

    print("\n\n\n\t---SUMMARY START---\n")
    espefuse.summary(esp, efuses, summary_args)
    print("\n\t---SUMMARY END---\n\n")


def efuse_burn_key(esp, args):

    efuses, efuse_operations = espefuse.get_efuses(esp, esp.CHIP_NAME, False, False, False)

    if args.efuse_key_id is None:
        print("efuse Key id cannot be None")
        sys.exit(-1)

    key_file = open(hmac_key_file, 'rb')
    # First element of _KEYBLOCKS is config data so add offset of 1
    key_block = efuses._KEYBLOCKS[args.efuse_key_id + 1][0]
    burn_key_args = DefineArgs({
        'baud': 115200,
        'before': 'default_reset',
        'chip': esp.CHIP_NAME,
        'debug': False,
        'do_not_confirm': False,
        'block': [key_block],
        'keyfile': [key_file],
        'keypurpose': ['HMAC_DOWN_DIGITAL_SIGNATURE'],
        'operation': 'burn_key',
        'force_write_always': False,
        'no_read_protect': True,
        'no_write_protect': False,
        'port': args.port,

    })

    try:
        efuse_operations.burn_key(esp, efuses, burn_key_args, None)
        key_file.close()
    except esptool.FatalError:
        print("\nERROR: The provided key block already contains previously burned key, please use a different key block ID")
        sys.exit(-1)


def generate_csv_file(c, iv, hmac_key_id, key_size, csv_file):

    with open(csv_file, 'wt', encoding='utf8') as f:
        f.write("# This is a generated csv file containing required parameters for the Digital Signature operaiton\n")
        f.write("key,type,encoding,value\nesp_ds_ns,namespace,,\n")
        f.write("esp_ds_c,data,hex2bin,%s\n" % (c.hex()))
        f.write("esp_ds_iv,data,hex2bin,%s\n" % (iv.hex()))
        f.write("esp_ds_key_id,data,u8,%d\n" % (hmac_key_id))
        f.write("esp_ds_rsa_len,data,u16,%d\n" % (key_size))


def generate_nvs_partition(input_filename, output_filename):

    nvs_args = DefineArgs({
        'input': input_filename,
        'outdir': os.getcwd(),
        'output': output_filename,
        'size': hex(0x3000),
        'version': 2,
        'keyfile':None,
    })

    nvs_gen.generate(nvs_args, is_encr_enabled=False, encr_key=None)


def flash_nvs_partition(bin_path, addr, esp):
    esp.connect()
    print(bin_path)
    abs_bin_path = os.path.dirname(os.path.abspath(__file__)) + '/' + bin_path
    print(abs_bin_path)
    if (os.path.exists(abs_bin_path) is False):
        print("NVS partition not found")
        sys.exit(-1)

    with open(bin_path, 'rb') as nvs_file:

        flash_file = [(addr, nvs_file)]

        flash_args = DefineArgs({
            'flash_size': '4MB',
            'flash_mode': 'qio',
            'flash_freq': '80m',
            'addr_filename': flash_file,
            'no_stub': False,
            'compress': False,
            'verify': False,
            'encrypt': False,
            'erase_all': False,
        })

        esp.change_baud(baud=921600)
        esptool.write_flash(esp, flash_args)


def main():
    parser = argparse.ArgumentParser(description='''Provision the ESPWROOM32SE device with
        device_certificate and signer_certificate required for TLS authentication''')

    parser.add_argument(
        '--private-key',
        dest='privkey',
        default='main/client.key',
        metavar='relative/path/to/client-priv-key',
        help='relative path(from secure_cert_mfg.py) to signer certificate private key')

    parser.add_argument(
        "--pwd", '--password',
        dest='priv_key_pass',
        metavar='[password]',
        help='the password associated with the private key')

    parser.add_argument(
        '--summary',
        dest='summary',action='store_true',
        help='Provide this option to print efuse summary the chip')

    parser.add_argument(
        '--efuse_key_id',
        dest='efuse_key_id', type=int, choices=range(1,6),
        metavar='[key_id] ',
        default=1,
        help='Provide the efuse key_id which contains/will contain HMAC_KEY, default is 1')

    parser.add_argument(
        "--port", '-p',
        dest='port',
        metavar='[port]',
        required=True,
        help='UART com port to which ESP device is connected')

    parser.add_argument(
        '--overwrite',
        dest='overwrite', action='store_true',
        help='Overwrite previously generated keys')

    args = parser.parse_args()

    esp = esptool.ESPLoader.detect_chip(args.port,baud=115200)
    if (esp.CHIP_NAME != 'ESP32-S2'):
        print("Only ESP32S2 chip is supported")
        sys.exit(-1)

    if args.summary is not False:
        efuse_summary(esp, args)
        sys.exit(0)

    if (os.path.exists(esp_ds_data_dir) is False):
        os.makedirs(esp_ds_data_dir)
    else:
        if (args.overwrite is False):
            print("WARNING: previous ecrypted private key data exists.\nIf you want to overwrite,"
                  " please execute your command with providing \"--overwrite\" option")
            sys.exit(0)
        else:
            print("overwriting previous encrypted private key data, as you have provided \"--overwrite\" option")

    c, iv, key_size = calculate_ds_parameters(args.privkey, args.priv_key_pass)
    efuse_burn_key(esp, args)

    generate_csv_file(c, iv, args.efuse_key_id, key_size, csv_filename)
    generate_nvs_partition(csv_filename, bin_filename)
    flash_nvs_partition(bin_filename, 0x10000, esp)


if __name__ == "__main__":
    main()