mirror of
https://github.com/espressif/esp-idf.git
synced 2024-10-05 20:47:46 -04:00
394 lines
16 KiB
Python
394 lines
16 KiB
Python
#!/usr/bin/env python
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# SPDX-FileCopyrightText: 2020-2022 Espressif Systems (Shanghai) CO LTD
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# SPDX-License-Identifier: Apache-2.0
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import argparse
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import hashlib
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import hmac
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import json
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import os
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import struct
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import subprocess
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import sys
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from cryptography.hazmat.backends import default_backend
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from cryptography.hazmat.primitives import serialization
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from cryptography.hazmat.primitives.asymmetric import rsa
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from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
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from cryptography.utils import int_to_bytes
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try:
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import nvs_partition_gen as nvs_gen
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except ImportError:
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idf_path = os.getenv('IDF_PATH')
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if not idf_path or not os.path.exists(idf_path):
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raise Exception('IDF_PATH not found')
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sys.path.insert(0, os.path.join(idf_path, 'components', 'nvs_flash', 'nvs_partition_generator'))
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import nvs_partition_gen as nvs_gen
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# Check python version is proper or not to avoid script failure
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assert sys.version_info >= (3, 6, 0), 'Python version too low.'
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esp_ds_data_dir = 'esp_ds_data'
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# hmac_key_file is generated when HMAC_KEY is calculated, it is used when burning HMAC_KEY to efuse
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hmac_key_file = esp_ds_data_dir + '/hmac_key.bin'
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# csv and bin filenames are default filenames for nvs partition files created with this script
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csv_filename = esp_ds_data_dir + '/pre_prov.csv'
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bin_filename = esp_ds_data_dir + '/pre_prov.bin'
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expected_json_path = os.path.join('build', 'config', 'sdkconfig.json')
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# Targets supported by the script
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supported_targets = {'esp32s2', 'esp32c3'}
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supported_key_size = {'esp32s2':[1024, 2048, 3072, 4096], 'esp32c3':[1024, 2048, 3072]}
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# @return
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# on success idf_target - value of the IDF_TARGET read from build/config/sdkconfig.json
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# on failure None
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def get_idf_target():
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if os.path.exists(expected_json_path):
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sdkconfig = json.load(open(expected_json_path))
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idf_target_read = sdkconfig['IDF_TARGET']
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return idf_target_read
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else:
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print('ERROR: IDF_TARGET has not been set for the supported targets,'
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"\nplase execute command \"idf.py set-target {TARGET}\" in the example directory")
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return None
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def load_privatekey(key_file_path, password=None):
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key_file = open(key_file_path, 'rb')
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key = key_file.read()
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key_file.close()
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return serialization.load_pem_private_key(key, password=password, backend=default_backend())
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def number_as_bytes(number, pad_bits=None):
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"""
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Given a number, format as a little endian array of bytes
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"""
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result = int_to_bytes(number)[::-1]
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while pad_bits is not None and len(result) < (pad_bits // 8):
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result += b'\x00'
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return result
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# @return
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# c : ciphertext_c
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# iv : initialization vector
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# key_size : key size of the RSA private key in bytes.
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# @input
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# privkey : path to the RSA private key
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# priv_key_pass : path to the RSA privaete key password
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# hmac_key : HMAC key value ( to calculate DS params)
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# idf_target : The target chip for the script (e.g. esp32s2, esp32c3)
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# @info
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# The function calculates the encrypted private key parameters.
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# Consult the DS documentation (available for the ESP32-S2) in the esp-idf programming guide for more details about the variables and calculations.
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def calculate_ds_parameters(privkey, priv_key_pass, hmac_key, idf_target):
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private_key = load_privatekey(privkey, priv_key_pass)
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if not isinstance(private_key, rsa.RSAPrivateKey):
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print('ERROR: Only RSA private keys are supported')
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sys.exit(-1)
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if hmac_key is None:
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print('ERROR: hmac_key cannot be None')
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sys.exit(-2)
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priv_numbers = private_key.private_numbers()
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pub_numbers = private_key.public_key().public_numbers()
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Y = priv_numbers.d
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M = pub_numbers.n
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key_size = private_key.key_size
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if key_size not in supported_key_size[idf_target]:
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print('ERROR: Private key size {0} not supported for the target {1},\nthe supported key sizes are {2}'
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.format(key_size, idf_target, str(supported_key_size[idf_target])))
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sys.exit(-1)
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iv = os.urandom(16)
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rr = 1 << (key_size * 2)
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rinv = rr % pub_numbers.n
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mprime = - rsa._modinv(M, 1 << 32)
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mprime &= 0xFFFFFFFF
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length = key_size // 32 - 1
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# get max supported key size for the respective target
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max_len = max(supported_key_size[idf_target])
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aes_key = hmac.HMAC(hmac_key, b'\xFF' * 32, hashlib.sha256).digest()
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md_in = number_as_bytes(Y, max_len) + \
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number_as_bytes(M, max_len) + \
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number_as_bytes(rinv, max_len) + \
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struct.pack('<II', mprime, length) + \
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iv
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# expected_len = max_len_Y + max_len_M + max_len_rinv + (mprime + length packed (8 bytes))+ iv (16 bytes)
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expected_len = (max_len / 8) * 3 + 8 + 16
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assert len(md_in) == expected_len
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md = hashlib.sha256(md_in).digest()
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# In case of ESP32-S2
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# Y4096 || M4096 || Rb4096 || M_prime32 || LENGTH32 || MD256 || 0x08*8
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# In case of ESP32-C3
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# Y3072 || M3072 || Rb3072 || M_prime32 || LENGTH32 || MD256 || 0x08*8
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p = number_as_bytes(Y, max_len) + \
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number_as_bytes(M, max_len) + \
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number_as_bytes(rinv, max_len) + \
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md + \
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struct.pack('<II', mprime, length) + \
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b'\x08' * 8
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# expected_len = max_len_Y + max_len_M + max_len_rinv + md (32 bytes) + (mprime + length packed (8bytes)) + padding (8 bytes)
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expected_len = (max_len / 8) * 3 + 32 + 8 + 8
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assert len(p) == expected_len
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cipher = Cipher(algorithms.AES(aes_key), modes.CBC(iv), backend=default_backend())
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encryptor = cipher.encryptor()
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c = encryptor.update(p) + encryptor.finalize()
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return c, iv, key_size
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# @info
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# The function makes use of the "espefuse.py" script to read the efuse summary
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def efuse_summary(args, idf_target):
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os.system('python $IDF_PATH/components/esptool_py/esptool/espefuse.py --chip {0} -p {1} summary'.format(idf_target, (args.port)))
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# @info
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# The function makes use of the "espefuse.py" script to burn the HMAC key on the efuse.
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def efuse_burn_key(args, idf_target):
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# In case of a development (default) usecase we disable the read protection.
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key_block_status = '--no-read-protect'
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if args.production is True:
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# Whitespace character will have no additional effect on the command and
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# read protection will be enabled as the default behaviour of the command
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key_block_status = ' '
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os.system('python $IDF_PATH/components/esptool_py/esptool/espefuse.py --chip {0} -p {1} burn_key '
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'{2} {3} HMAC_DOWN_DIGITAL_SIGNATURE {4}'
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.format((idf_target), (args.port), ('BLOCK_KEY' + str(args.efuse_key_id)), (hmac_key_file), (key_block_status)))
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# @info
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# Generate a custom csv file of encrypted private key parameters.
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# The csv file is required by the nvs_partition_generator utility to create the nvs partition.
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def generate_csv_file(c, iv, hmac_key_id, key_size, csv_file):
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with open(csv_file, 'wt', encoding='utf8') as f:
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f.write('# This is a generated csv file containing required parameters for the Digital Signature operation\n')
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f.write('key,type,encoding,value\nesp_ds_ns,namespace,,\n')
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f.write('esp_ds_c,data,hex2bin,%s\n' % (c.hex()))
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f.write('esp_ds_iv,data,hex2bin,%s\n' % (iv.hex()))
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f.write('esp_ds_key_id,data,u8,%d\n' % (hmac_key_id))
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f.write('esp_ds_rsa_len,data,u16,%d\n' % (key_size))
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class DefineArgs(object):
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def __init__(self, attributes):
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for key, value in attributes.items():
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self.__setattr__(key, value)
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# @info
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# This function uses the nvs_partition_generater utility
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# to generate the nvs partition of the encrypted private key parameters.
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def generate_nvs_partition(input_filename, output_filename):
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nvs_args = DefineArgs({
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'input': input_filename,
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'outdir': os.getcwd(),
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'output': output_filename,
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'size': hex(0x3000),
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'version': 2,
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'keyfile':None,
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})
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nvs_gen.generate(nvs_args, is_encr_enabled=False, encr_key=None)
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# @return
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# The json formatted summary of the efuse.
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def get_efuse_summary_json(args, idf_target):
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_efuse_summary = None
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try:
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_efuse_summary = subprocess.check_output(('python $IDF_PATH/components/esptool_py/esptool/espefuse.py '
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'--chip {0} -p {1} summary --format json'.format(idf_target, (args.port))), shell=True)
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except subprocess.CalledProcessError as e:
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print((e.output).decode('UTF-8'))
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sys.exit(-1)
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_efuse_summary = _efuse_summary.decode('UTF-8')
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# Remove everything before actual json data from efuse_summary command output.
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_efuse_summary = _efuse_summary[_efuse_summary.find('{'):]
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try:
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_efuse_summary_json = json.loads(_efuse_summary)
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except json.JSONDecodeError:
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print('ERROR: failed to parse the json output')
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sys.exit(-1)
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return _efuse_summary_json
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# @return
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# on success: 256 bit HMAC key present in the given key_block (args.efuse_key_id)
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# on failure: None
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# @info
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# This function configures the provided efuse key_block.
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# If the provided efuse key_block is empty the function generates a new HMAC key and burns it in the efuse key_block.
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# If the key_block already contains a key the function reads the key from the efuse key_block
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def configure_efuse_key_block(args, idf_target):
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efuse_summary_json = get_efuse_summary_json(args, idf_target)
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key_blk = 'BLOCK_KEY' + str(args.efuse_key_id)
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key_purpose = 'KEY_PURPOSE_' + str(args.efuse_key_id)
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kb_writeable = efuse_summary_json[key_blk]['writeable']
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kb_readable = efuse_summary_json[key_blk]['readable']
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hmac_key_read = None
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# If the efuse key block is writable (empty) then generate and write
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# the new hmac key and check again
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# If the efuse key block is not writable (already contains a key) then check if it is redable
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if kb_writeable is True:
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print('Provided key block (KEY BLOCK %1d) is writable\n Generating a new key and burning it in the efuse..\n' % (args.efuse_key_id))
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new_hmac_key = os.urandom(32)
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with open(hmac_key_file, 'wb') as key_file:
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key_file.write(new_hmac_key)
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# Burn efuse key
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efuse_burn_key(args, idf_target)
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if args.production is False:
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# Read fresh summary of the efuse to read the key value from efuse.
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# If the key read from efuse matches with the key generated
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# on host then burn_key operation was successfull
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new_efuse_summary_json = get_efuse_summary_json(args, idf_target)
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hmac_key_read = new_efuse_summary_json[key_blk]['value']
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print(hmac_key_read)
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hmac_key_read = bytes.fromhex(hmac_key_read)
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if new_hmac_key == hmac_key_read:
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print('Key was successfully written to the efuse (KEY BLOCK %1d)' % (args.efuse_key_id))
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else:
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print('ERROR: Failed to burn the hmac key to efuse (KEY BLOCK %1d),'
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'\nPlease execute the script again using a different key id' % (args.efuse_key_id))
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return None
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else:
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new_efuse_summary_json = get_efuse_summary_json(args, idf_target)
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if new_efuse_summary_json[key_purpose]['value'] != 'HMAC_DOWN_DIGITAL_SIGNATURE':
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print('ERROR: Failed to verify the key purpose of the key block{})'.format(args.efuse_key_id))
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return None
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hmac_key_read = new_hmac_key
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else:
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# If the efuse key block is redable, then read the key from efuse block and use it for encrypting the RSA private key parameters.
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# If the efuse key block is not redable or it has key purpose set to a different
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# value than "HMAC_DOWN_DIGITAL_SIGNATURE" then we cannot use it for DS operation
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if kb_readable is True:
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if efuse_summary_json[key_purpose]['value'] == 'HMAC_DOWN_DIGITAL_SIGNATURE':
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print('Provided efuse key block (KEY BLOCK %1d) already contains a key with key_purpose=HMAC_DOWN_DIGITAL_SIGNATURE,'
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'\nusing the same key for encrypting the private key data...\n' % (args.efuse_key_id))
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hmac_key_read = efuse_summary_json[key_blk]['value']
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hmac_key_read = bytes.fromhex(hmac_key_read)
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if args.keep_ds_data is True:
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with open(hmac_key_file, 'wb') as key_file:
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key_file.write(hmac_key_read)
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else:
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print('ERROR: Provided efuse key block ((KEY BLOCK %1d)) contains a key with key purpose different'
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'than HMAC_DOWN_DIGITAL_SIGNATURE,\nplease execute the script again with a different value of the efuse key id.' % (args.efuse_key_id))
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return None
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else:
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print('ERROR: Provided efuse key block (KEY BLOCK %1d) is not readable and writeable,'
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'\nplease execute the script again with a different value of the efuse key id.' % (args.efuse_key_id))
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return None
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# Return the hmac key burned into the efuse
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return hmac_key_read
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def cleanup(args):
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if args.keep_ds_data is False:
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if os.path.exists(hmac_key_file):
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os.remove(hmac_key_file)
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if os.path.exists(csv_filename):
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os.remove(csv_filename)
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def main():
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parser = argparse.ArgumentParser(description='''Generate an HMAC key and burn it in the desired efuse key block (required for Digital Signature),
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Generates an NVS partition containing the encrypted private key parameters from the client private key.
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''')
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parser.add_argument(
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'--private-key',
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dest='privkey',
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default='client.key',
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metavar='relative/path/to/client-priv-key',
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help='relative path to client private key')
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parser.add_argument(
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'--pwd', '--password',
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dest='priv_key_pass',
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metavar='[password]',
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help='the password associated with the private key')
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parser.add_argument(
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'--summary',
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dest='summary',action='store_true',
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help='Provide this option to print efuse summary of the chip')
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parser.add_argument(
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'--efuse_key_id',
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dest='efuse_key_id', type=int, choices=range(1,6),
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metavar='[key_id] ',
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default=1,
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help='Provide the efuse key_id which contains/will contain HMAC_KEY, default is 1')
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parser.add_argument(
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'--port', '-p',
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dest='port',
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metavar='[port]',
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required=True,
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help='UART com port to which the ESP device is connected')
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parser.add_argument(
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'--keep_ds_data_on_host','-keep_ds_data',
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dest='keep_ds_data', action='store_true',
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help='Keep encrypted private key data and key on host machine for testing purpose')
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parser.add_argument(
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'--production', '-prod',
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dest='production', action='store_true',
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help='Enable production configurations. e.g.keep efuse key block read protection enabled')
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args = parser.parse_args()
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idf_target = get_idf_target()
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if idf_target not in supported_targets:
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if idf_target is not None:
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print('ERROR: The script does not support the target %s' % idf_target)
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sys.exit(-1)
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idf_target = str(idf_target)
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if args.summary is not False:
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efuse_summary(args, idf_target)
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sys.exit(0)
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if (os.path.exists(args.privkey) is False):
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print('ERROR: The provided private key file does not exist')
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sys.exit(-1)
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if (os.path.exists(esp_ds_data_dir) is False):
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os.makedirs(esp_ds_data_dir)
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# Burn hmac_key on the efuse block (if it is empty) or read it
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# from the efuse block (if the efuse block already contains a key).
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hmac_key_read = configure_efuse_key_block(args, idf_target)
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if hmac_key_read is None:
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sys.exit(-1)
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# Calculate the encrypted private key data along with all other parameters
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c, iv, key_size = calculate_ds_parameters(args.privkey, args.priv_key_pass, hmac_key_read, idf_target)
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# Generate csv file for the DS data and generate an NVS partition.
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generate_csv_file(c, iv, args.efuse_key_id, key_size, csv_filename)
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generate_nvs_partition(csv_filename, bin_filename)
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cleanup(args)
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if __name__ == '__main__':
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main()
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