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# Copyright (c) 2016 The Johns Hopkins University/Applied Physics Laboratory
# All Rights Reserved.
#
# 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 logging
import os
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 algorithms
from kmip.core import enums
from kmip.core import exceptions
from kmip.services.server.crypto import api
class CryptographyEngine(api.CryptographicEngine):
"""
A cryptographic engine that uses pyca/cryptography to generate
cryptographic objects and conduct cryptographic operations.
"""
def __init__(self):
"""
Construct a CryptographyEngine.
"""
self.logger = logging.getLogger('kmip.server.engine.cryptography')
self._symmetric_key_algorithms = {
enums.CryptographicAlgorithm.TRIPLE_DES: algorithms.TripleDES,
enums.CryptographicAlgorithm.AES: algorithms.AES,
enums.CryptographicAlgorithm.BLOWFISH: algorithms.Blowfish,
enums.CryptographicAlgorithm.CAMELLIA: algorithms.Camellia,
enums.CryptographicAlgorithm.CAST5: algorithms.CAST5,
enums.CryptographicAlgorithm.IDEA: algorithms.IDEA,
enums.CryptographicAlgorithm.RC4: algorithms.ARC4
}
self._asymetric_key_algorithms = {
enums.CryptographicAlgorithm.RSA: self._create_rsa_key_pair
}
def create_symmetric_key(self, algorithm, length):
"""
Create a symmetric key.
Args:
algorithm(CryptographicAlgorithm): An enumeration specifying the
algorithm for which the created key will be compliant.
length(int): The length of the key to be created. This value must
be compliant with the constraints of the provided algorithm.
Returns:
dict: A dictionary containing the key data, with the following
key/value fields:
* value - the bytes of the key
* format - a KeyFormatType enumeration for the bytes format
Raises:
InvalidField: Raised when the algorithm is unsupported or the
length is incompatible with the algorithm.
CryptographicFailure: Raised when the key generation process
fails.
Example:
>>> engine = CryptographyEngine()
>>> key = engine.create_symmetric_key(
... CryptographicAlgorithm.AES, 256)
"""
if algorithm not in self._symmetric_key_algorithms.keys():
raise exceptions.InvalidField(
"The cryptographic algorithm {0} is not a supported symmetric "
"key algorithm.".format(algorithm)
)
cryptography_algorithm = self._symmetric_key_algorithms.get(algorithm)
if length not in cryptography_algorithm.key_sizes:
raise exceptions.InvalidField(
"The cryptographic length ({0}) is not valid for "
"the cryptographic algorithm ({1}).".format(
length, algorithm.name
)
)
self.logger.info(
"Generating a {0} symmetric key with length: {1}".format(
algorithm.name, length
)
)
key_bytes = os.urandom(length // 8)
try:
cryptography_algorithm(key_bytes)
except Exception as e:
self.logger.exception(e)
raise exceptions.CryptographicFailure(
"Invalid bytes for the provided cryptographic algorithm.")
return {'value': key_bytes, 'format': enums.KeyFormatType.RAW}
def create_asymmetric_key_pair(self, algorithm, length):
"""
Create an asymmetric key pair.
Args:
algorithm(CryptographicAlgorithm): An enumeration specifying the
algorithm for which the created keys will be compliant.
length(int): The length of the keys to be created. This value must
be compliant with the constraints of the provided algorithm.
Returns:
dict: A dictionary containing the public key data, with at least
the following key/value fields:
* value - the bytes of the key
* format - a KeyFormatType enumeration for the bytes format
dict: A dictionary containing the private key data, identical in
structure to the one above.
Raises:
InvalidField: Raised when the algorithm is unsupported or the
length is incompatible with the algorithm.
CryptographicFailure: Raised when the key generation process
fails.
Example:
>>> engine = CryptographyEngine()
>>> key = engine.create_asymmetric_key(
... CryptographicAlgorithm.RSA, 2048)
"""
if algorithm not in self._asymetric_key_algorithms.keys():
raise exceptions.InvalidField(
"The cryptographic algorithm ({0}) is not a supported "
"asymmetric key algorithm.".format(algorithm)
)
engine_method = self._asymetric_key_algorithms.get(algorithm)
return engine_method(length)
def _create_rsa_key_pair(self, length, public_exponent=65537):
"""
Create an RSA key pair.
Args:
length(int): The length of the keys to be created. This value must
be compliant with the constraints of the provided algorithm.
public_exponent(int): The value of the public exponent needed to
generate the keys. Usually a small Fermat prime number.
Optional, defaults to 65537.
Returns:
dict: A dictionary containing the public key data, with the
following key/value fields:
* value - the bytes of the key
* format - a KeyFormatType enumeration for the bytes format
* public_exponent - the public exponent integer
dict: A dictionary containing the private key data, identical in
structure to the one above.
Raises:
CryptographicFailure: Raised when the key generation process
fails.
"""
self.logger.info(
"Generating an RSA key pair with length: {0}, and "
"public_exponent: {1}".format(
length, public_exponent
)
)
try:
private_key = rsa.generate_private_key(
public_exponent=public_exponent,
key_size=length,
backend=default_backend())
public_key = private_key.public_key()
private_bytes = private_key.private_bytes(
serialization.Encoding.DER,
serialization.PrivateFormat.PKCS8,
serialization.NoEncryption())
public_bytes = public_key.public_bytes(
serialization.Encoding.DER,
serialization.PublicFormat.PKCS1)
except Exception as e:
self.logger.exception(e)
raise exceptions.CryptographicFailure(
"An error occurred while generating the RSA key pair. "
"See the server log for more information."
)
public_key = {
'value': public_bytes,
'format': enums.KeyFormatType.PKCS_1,
'public_exponent': public_exponent
}
private_key = {
'value': private_bytes,
'format': enums.KeyFormatType.PKCS_8,
'public_exponent': public_exponent
}
return public_key, private_key
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