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102 lines
3.5 KiB
102 lines
3.5 KiB
"""
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All function in this module take and return :class:`bytes`
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"""
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import sys
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from os import urandom as random_bytes
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from struct import pack
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from base64 import b64decode
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from cryptography.hazmat.primitives.hmac import HMAC
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from cryptography.hazmat.primitives.hashes import Hash, SHA1
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from cryptography.hazmat.primitives.asymmetric.padding import PSS, OAEP, MGF1
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from cryptography.hazmat.primitives.ciphers import Cipher
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from cryptography.hazmat.primitives.ciphers.algorithms import AES
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from cryptography.hazmat.primitives.ciphers.modes import CBC, ECB
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import cryptography.hazmat.backends
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backend = cryptography.hazmat.backends.default_backend()
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class UniverseKey(object):
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"""Public keys for Universes"""
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Public = backend.load_der_public_key(b64decode("""
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MIGdMA0GCSqGSIb3DQEBAQUAA4GLADCBhwKBgQDf7BrWLBBmLBc1OhSwfFkRf53T
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2Ct64+AVzRkeRuh7h3SiGEYxqQMUeYKO6UWiSRKpI2hzic9pobFhRr3Bvr/WARvY
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gdTckPv+T1JzZsuVcNfFjrocejN1oWI0Rrtgt4Bo+hOneoo3S57G9F1fOpn5nsQ6
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6WOiu4gZKODnFMBCiQIBEQ==
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"""))
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BS = 16
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pad = lambda s: s + (BS - len(s) % BS) * pack('B', BS - len(s) % BS)
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if sys.version_info < (3,):
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unpad = lambda s: s[0:-ord(s[-1])]
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else:
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unpad = lambda s: s[0:-s[-1]]
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def generate_session_key(hmac_secret=b''):
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"""
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:param hmac_secret: optional HMAC
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:type hmac_secret: :class:`bytes`
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:return: (session_key, encrypted_session_key) tuple
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:rtype: :class:`tuple`
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"""
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session_key = random_bytes(32)
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encrypted_session_key = UniverseKey.Public.encrypt(session_key + hmac_secret,
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OAEP(MGF1(SHA1()), SHA1(), None)
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)
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return (session_key, encrypted_session_key)
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def symmetric_encrypt(message, key):
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iv = random_bytes(BS)
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return symmetric_encrypt_with_iv(message, key, iv)
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def symmetric_encrypt_HMAC(message, key, hmac_secret):
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prefix = random_bytes(3)
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hmac = hmac_sha1(hmac_secret, prefix + message)
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iv = hmac[:13] + prefix
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return symmetric_encrypt_with_iv(message, key, iv)
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def symmetric_encrypt_iv(iv, key):
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encryptor = Cipher(AES(key), ECB(), backend).encryptor()
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return encryptor.update(iv) + encryptor.finalize()
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def symmetric_encrypt_with_iv(message, key, iv):
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encrypted_iv = symmetric_encrypt_iv(iv, key)
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encryptor = Cipher(AES(key), CBC(iv), backend).encryptor()
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cyphertext = encryptor.update(pad(message)) + encryptor.finalize()
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return encrypted_iv + cyphertext
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def symmetric_decrypt(cyphertext, key):
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iv = symmetric_decrypt_iv(cyphertext, key)
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return symmetric_decrypt_with_iv(cyphertext, key, iv)
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def symmetric_decrypt_HMAC(cyphertext, key, hmac_secret):
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""":raises: :class:`RuntimeError` when HMAC verification fails"""
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iv = symmetric_decrypt_iv(cyphertext, key)
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message = symmetric_decrypt_with_iv(cyphertext, key, iv)
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hmac = hmac_sha1(hmac_secret, iv[-3:] + message)
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if iv[:13] != hmac[:13]:
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raise RuntimeError("Unable to decrypt message. HMAC does not match.")
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return message
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def symmetric_decrypt_iv(cyphertext, key):
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decryptor = Cipher(AES(key), ECB(), backend).decryptor()
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return decryptor.update(cyphertext[:BS]) + decryptor.finalize()
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def symmetric_decrypt_with_iv(cyphertext, key, iv):
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decryptor = Cipher(AES(key), CBC(iv), backend).decryptor()
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return unpad(decryptor.update(cyphertext[BS:]) + decryptor.finalize())
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def hmac_sha1(secret, data):
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hmac = HMAC(secret, SHA1(), backend)
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hmac.update(data)
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return hmac.finalize()
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def sha1_hash(data):
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sha = Hash(SHA1(), backend)
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sha.update(data)
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return sha.finalize()
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