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import os
from abc import ABCMeta
class JWEAlgorithmBase(metaclass=ABCMeta):
"""Base interface for all JWE algorithms.
"""
EXTRA_HEADERS = None
name = None
description = None
algorithm_type = 'JWE'
algorithm_location = 'alg'
def prepare_key(self, raw_data):
raise NotImplementedError
def generate_preset(self, enc_alg, key):
raise NotImplementedError
class JWEAlgorithm(JWEAlgorithmBase, metaclass=ABCMeta):
"""Interface for JWE algorithm conforming to RFC7518.
JWA specification (RFC7518) SHOULD implement the algorithms for JWE with this base implementation.
"""
def wrap(self, enc_alg, headers, key, preset=None):
raise NotImplementedError
def unwrap(self, enc_alg, ek, headers, key):
raise NotImplementedError
class JWEAlgorithmWithTagAwareKeyAgreement(JWEAlgorithmBase, metaclass=ABCMeta):
"""Interface for JWE algorithm with tag-aware key agreement (in key agreement with key wrapping mode).
ECDH-1PU is an example of such an algorithm.
"""
def generate_keys_and_prepare_headers(self, enc_alg, key, sender_key, preset=None):
raise NotImplementedError
def agree_upon_key_and_wrap_cek(self, enc_alg, headers, key, sender_key, epk, cek, tag):
raise NotImplementedError
def wrap(self, enc_alg, headers, key, sender_key, preset=None):
raise NotImplementedError
def unwrap(self, enc_alg, ek, headers, key, sender_key, tag=None):
raise NotImplementedError
class JWEEncAlgorithm:
name = None
description = None
algorithm_type = 'JWE'
algorithm_location = 'enc'
IV_SIZE = None
CEK_SIZE = None
def generate_cek(self):
return os.urandom(self.CEK_SIZE // 8)
def generate_iv(self):
return os.urandom(self.IV_SIZE // 8)
def check_iv(self, iv):
if len(iv) * 8 != self.IV_SIZE:
raise ValueError('Invalid "iv" size')
def encrypt(self, msg, aad, iv, key):
"""Encrypt the given "msg" text.
:param msg: text to be encrypt in bytes
:param aad: additional authenticated data in bytes
:param iv: initialization vector in bytes
:param key: encrypted key in bytes
:return: (ciphertext, tag)
"""
raise NotImplementedError
def decrypt(self, ciphertext, aad, iv, tag, key):
"""Decrypt the given cipher text.
:param ciphertext: ciphertext in bytes
:param aad: additional authenticated data in bytes
:param iv: initialization vector in bytes
:param tag: authentication tag in bytes
:param key: encrypted key in bytes
:return: message
"""
raise NotImplementedError
class JWEZipAlgorithm:
name = None
description = None
algorithm_type = 'JWE'
algorithm_location = 'zip'
def compress(self, s):
raise NotImplementedError
def decompress(self, s):
raise NotImplementedError
class JWESharedHeader(dict):
"""Shared header object for JWE.
Combines protected header and shared unprotected header together.
"""
def __init__(self, protected, unprotected):
obj = {}
if protected:
obj.update(protected)
if unprotected:
obj.update(unprotected)
super().__init__(obj)
self.protected = protected if protected else {}
self.unprotected = unprotected if unprotected else {}
def update_protected(self, addition):
self.update(addition)
self.protected.update(addition)
@classmethod
def from_dict(cls, obj):
if isinstance(obj, cls):
return obj
return cls(obj.get('protected'), obj.get('unprotected'))
class JWEHeader(dict):
"""Header object for JWE.
Combines protected header, shared unprotected header and specific recipient's unprotected header together.
"""
def __init__(self, protected, unprotected, header):
obj = {}
if protected:
obj.update(protected)
if unprotected:
obj.update(unprotected)
if header:
obj.update(header)
super().__init__(obj)
self.protected = protected if protected else {}
self.unprotected = unprotected if unprotected else {}
self.header = header if header else {}