47 lines
1.5 KiB
Python
47 lines
1.5 KiB
Python
# Copyright (c) 2022 by Ron Frederick <ronf@timeheart.net> and others.
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#
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# This program and the accompanying materials are made available under
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# the terms of the Eclipse Public License v2.0 which accompanies this
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# distribution and is available at:
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#
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# http://www.eclipse.org/legal/epl-2.0/
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#
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# This program may also be made available under the following secondary
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# licenses when the conditions for such availability set forth in the
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# Eclipse Public License v2.0 are satisfied:
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#
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# GNU General Public License, Version 2.0, or any later versions of
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# that license
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#
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# SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
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#
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# Contributors:
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# Ron Frederick - initial implementation, API, and documentation
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"""A shim around PyCA for Diffie Hellman key exchange"""
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from cryptography.hazmat.primitives.asymmetric import dh
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class DH:
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"""A shim around PyCA for Diffie Hellman key exchange"""
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def __init__(self, g: int, p: int):
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self._pn = dh.DHParameterNumbers(p, g)
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self._priv_key = self._pn.parameters().generate_private_key()
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def get_public(self) -> int:
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"""Return the public key to send in the handshake"""
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pub_key = self._priv_key.public_key()
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return pub_key.public_numbers().y
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def get_shared(self, peer_public: int) -> int:
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"""Return the shared key from the peer's public key"""
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peer_key = dh.DHPublicNumbers(peer_public, self._pn).public_key()
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shared_key = self._priv_key.exchange(peer_key)
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return int.from_bytes(shared_key, 'big')
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