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73 lines
2.3 KiB
73 lines
2.3 KiB
import sys
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from struct import pack
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from base64 import b64decode
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from Crypto import Random
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from Crypto.Cipher import PKCS1_OAEP, AES
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from Crypto.PublicKey import RSA
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from Crypto.Hash import HMAC, SHA
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public_key = """
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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 = AES.block_size
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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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session_key = Random.new().read(32)
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cipher = PKCS1_OAEP.new(RSA.importKey(b64decode(public_key)))
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encrypted_session_key = cipher.encrypt(session_key + hmac_secret)
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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.new().read(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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random_bytes = Random.new().read(3)
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hmac = HMAC.new(hmac_secret, digestmod=SHA)
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hmac.update(random_bytes)
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hmac.update(message)
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iv = hmac.digest()[:13] + random_bytes
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return symmetric_encrypt_with_iv(message, key, iv)
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def symmetric_encrypt_with_iv(message, key, iv):
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encrypted_iv = AES.new(key, AES.MODE_ECB).encrypt(iv)
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cyphertext = AES.new(key, AES.MODE_CBC, iv).encrypt(pad(message))
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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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iv = symmetric_decrypt_iv(cyphertext, key)
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message = symmetric_decrypt_with_iv(cyphertext, key, iv)
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hmac = HMAC.new(hmac_secret, digestmod=SHA)
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hmac.update(iv[-3:])
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hmac.update(message)
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if iv[:13] != hmac.digest()[: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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return AES.new(key, AES.MODE_ECB).decrypt(cyphertext[:BS])
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def symmetric_decrypt_with_iv(cyphertext, key, iv):
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message = AES.new(key, AES.MODE_CBC, iv).decrypt(cyphertext[BS:])
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return unpad(message)
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