87 lines
2.4 KiB
Python
87 lines
2.4 KiB
Python
"""
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Decrypts messages encrypted with RSA.
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"""
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import base64
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from cryptography.hazmat.backends import default_backend
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from cryptography.hazmat.primitives import serialization, hashes
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from cryptography.hazmat.primitives.asymmetric import padding
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class RSADecryptor:
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"""
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Module for decrypting messages encrypted with RSA.
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Provides
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--------
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* :class:`RSADecryptor` - class for decrypting messages.
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"""
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def __init__(self, private_key_file):
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"""
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Initialize an RSADecryptor with a file containing a private RSA key.
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Parameters
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----------
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private_key_file : str
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The path to the private key file, which should be in PEM format.
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Attributes
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----------
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private_key_file : str
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The path to the private key file, which should be in PEM format.
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private_key : cryptography.hazmat.primitives.asymmetric.rsa.RSAPrivateKey
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The loaded private key.
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"""
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self.private_key_file = private_key_file
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self.private_key = self.load_private_key()
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def load_private_key(self):
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"""
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Load a private key from a file.
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The file should be in PEM format and contain the private key.
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Returns
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-------
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private_key : cryptography.hazmat.primitives.asymmetric.rsa.RSAPrivateKey
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The loaded private key.
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"""
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with open(self.private_key_file, 'rb') as f:
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private_key_data = f.read()
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private_key = serialization.load_pem_private_key(
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private_key_data,
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password=None,
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backend=default_backend()
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)
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return private_key
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def decrypt_message(self, encrypted_message):
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"""
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Decrypt an encrypted message.
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Parameters
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----------
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encrypted_message : str
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The encrypted message as a base64 encoded string.
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Returns
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-------
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decrypted_message : str
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The decrypted message as a string.
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"""
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encrypted_bytes = base64.b64decode(encrypted_message)
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try:
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decrypted = self.private_key.decrypt(
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encrypted_bytes,
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padding.OAEP(
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mgf=padding.MGF1(algorithm=hashes.SHA256()),
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algorithm=hashes.SHA256(),
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label=None
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)
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)
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return decrypted.decode()
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except ValueError:
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return None
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