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client.py
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client.py
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from ..errors.evervault_errors import (
UndefinedDataError,
InvalidPublicKeyError,
MissingTeamEcdhKey,
UnknownEncryptType,
)
from ..datatypes.map import map_header_type
from cryptography.hazmat.primitives.asymmetric import ec
from cryptography.hazmat.primitives.asymmetric.ec import EllipticCurvePublicKey
from cryptography.hazmat.primitives.serialization import Encoding, PublicFormat
from cryptography.hazmat.primitives.ciphers.aead import AESGCM
from cryptography.hazmat.primitives import hashes
from secrets import token_bytes
import base64
import time
from .version import VERSION
from .curves.p256 import P256PublicKey
BS = 32
KEY_INTERVAL = 15
SECP256R1 = "SECP256R1"
SECP256K1 = "SECP256K1"
CURVES = {"SECP256K1": ec.SECP256K1, "SECP256R1": ec.SECP256R1}
class Client(object):
def __init__(self, api_key=None, curve="SECP256K1"):
self.curve = curve
self.public_key = None
self.team_ecdh_key = None
self.decoded_team_cage_key = None
self.compressed_public_key = None
self.uncompressed_public_key = None
self.shared_key = None
self.start_time = int(time.time())
self.api_key = api_key
self.ev_version = self.__base_64_remove_padding(
base64.b64encode(bytes(VERSION[self.curve], "utf8")).decode("utf")
)
def encrypt_data(self, fetch, data):
if data is None:
raise UndefinedDataError("Data not defined")
self.__fetch_cage_key(fetch)
self.shared_key = self.__derive_shared_key()
if self.shared_key is None or type(self.shared_key) != bytes:
raise InvalidPublicKeyError("Provided EC compressed point is invalid")
if type(data) == bytes or type(data) == bytearray :
return self.__encrypt_file(data)
elif type(data) == dict or type(data) == list or type(data) == set:
return self.__traverse_and_encrypt(data)
elif self.__encryptable_data(data):
return self.__encrypt_string(data)
else:
raise UnknownEncryptType(f"Cannot encrypt unsupported type {data}")
def __traverse_and_encrypt(self, data):
if type(data) == list:
for idx, item in enumerate(data):
if not self.__encryptable_data(item):
data[idx] = self.__traverse_and_encrypt(item)
else:
data[idx] = self.__encrypt_string(item)
return data
elif type(data) == dict:
return self.__encrypt_object(data)
elif type(data) == set:
return self.__encrypt_set(data)
elif self.__encryptable_data(data):
return self.__encrypt_string(data)
else:
raise UnknownEncryptType(f"Cannot encrypt unsupported type {data}")
def __encrypt_object(self, data):
encrypted_data = {}
for key, value in data.items():
if self.__encryptable_data(value):
encrypted_data[key] = self.__encrypt_string(value)
else:
encrypted_data[key] = self.__traverse_and_encrypt(value)
return encrypted_data
def __encrypt_set(self, data):
encrypted_set = set()
for item in data:
if self.__encryptable_data(item):
encrypted_set.add(self.__encrypt_string(item))
else:
encrypted_set.add(self.__traverse_and_encrypt(item))
return encrypted_set
def __encrypt_string(self, data):
header_type = map_header_type(data)
coerced_data = self.__coerce_type(data)
iv = token_bytes(12)
aesgcm = AESGCM(self.shared_key)
encrypted_bytes = b""
if self.curve == SECP256K1:
encrypted_bytes = aesgcm.encrypt(iv, bytes(coerced_data, "utf8"), None)
else:
encrypted_bytes = aesgcm.encrypt(
iv, bytes(coerced_data, "utf8"), self.decoded_team_cage_key
)
return self.__format(
header_type,
base64.b64encode(iv).decode("utf"),
base64.b64encode(self.compressed_public_key).decode("utf"),
base64.b64encode(encrypted_bytes).decode("utf"),
)
def __encrypt_file(self, data):
iv = token_bytes(12)
aesgcm = AESGCM(self.shared_key)
encrypted_bytes = b""
if self.curve == SECP256K1 :
encrypted_bytes = aesgcm.encrypt(iv, data, None)
else:
encrypted_bytes = aesgcm.encrypt(
iv, data, self.decoded_team_cage_key
)
return self.__format_file(
iv,
self.compressed_public_key,
encrypted_bytes,
)
def __coerce_type(self, data):
if type(data) == bool:
return str(int(data))
elif type(data) == int or type(data) == float:
return str(data)
else:
return data
def __format(self, header, iv, public_key, encrypted_payload):
prefix = f":{header}" if header != "string" else ""
return f"ev:{self.ev_version}{prefix}:{self.__base_64_remove_padding(iv)}:{self.__base_64_remove_padding(public_key)}:{self.__base_64_remove_padding(encrypted_payload)}:$"
def __format_file(self, iv, public_key, encrypted_bytes) :
encrypted_file_identifier = bytes(b'\x25\x45\x56\x45\x4e\x43')
verion_number = bytes(b'\00') if self.curve == SECP256K1 else bytes(b'\01')
offset_to_data = bytes([55,00])
flags = bytes(b'\00')
return encrypted_file_identifier + verion_number + offset_to_data + bytes(public_key) + bytes(iv) + flags + bytes(encrypted_bytes)
def __base_64_remove_padding(self, data):
return data.rstrip("=")
def __encryptable_data(self, data):
return data is not None and (
type(data) == str
or type(data) == bool
or type(data) == int
or type(data) == float
)
def __fetch_cage_key(self, fetch):
if self.team_ecdh_key is None:
resp = fetch.get("cages/key")
key_name = "ecdhKey" if self.curve == "SECP256K1" else "ecdhP256Key"
self.decoded_team_cage_key = base64.b64decode(resp[key_name])
self.team_ecdh_key = EllipticCurvePublicKey.from_encoded_point(
CURVES[self.curve](), self.decoded_team_cage_key
)
def __derive_shared_key(self):
if self.team_ecdh_key is None:
raise MissingTeamEcdhKey("Team ECDH key not set in client")
elif self.shared_key is None:
return self.__generate_shared_key()
else:
now = int(time.time())
time_diff = now - self.start_time
if time_diff > KEY_INTERVAL:
self.start_time = now
return self.__generate_shared_key()
return self.shared_key
def __generate_shared_key(self):
generated_key = ec.generate_private_key(CURVES[self.curve])
public_key = generated_key.public_key()
self.compressed_public_key = public_key.public_bytes(
Encoding.X962, PublicFormat.CompressedPoint
)
self.uncompressed_public_key = public_key.public_bytes(
Encoding.X962, PublicFormat.UncompressedPoint
)
shared_key = generated_key.exchange(ec.ECDH(), self.team_ecdh_key)
if self.curve == SECP256R1:
# Perform KDF
hash_input = (
shared_key
+ b"\x00\x00\x00\x01"
+ P256PublicKey(self.uncompressed_public_key.hex()).encode()
)
digest = hashes.Hash(hashes.SHA256())
digest.update(hash_input)
return digest.finalize()
return shared_key