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Filename : x25519.py
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# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.

from __future__ import annotations

import abc

from cryptography.exceptions import UnsupportedAlgorithm, _Reasons
from cryptography.hazmat.bindings._rust import openssl as rust_openssl
from cryptography.hazmat.primitives import _serialization


class X25519PublicKey(metaclass=abc.ABCMeta):
    @classmethod
    def from_public_bytes(cls, data: bytes) -> X25519PublicKey:
        from cryptography.hazmat.backends.openssl.backend import backend

        if not backend.x25519_supported():
            raise UnsupportedAlgorithm(
                "X25519 is not supported by this version of OpenSSL.",
                _Reasons.UNSUPPORTED_EXCHANGE_ALGORITHM,
            )

        return backend.x25519_load_public_bytes(data)

    @abc.abstractmethod
    def public_bytes(
        self,
        encoding: _serialization.Encoding,
        format: _serialization.PublicFormat,
    ) -> bytes:
        """
        The serialized bytes of the public key.
        """

    @abc.abstractmethod
    def public_bytes_raw(self) -> bytes:
        """
        The raw bytes of the public key.
        Equivalent to public_bytes(Raw, Raw).
        """

    @abc.abstractmethod
    def __eq__(self, other: object) -> bool:
        """
        Checks equality.
        """


# For LibreSSL
if hasattr(rust_openssl, "x25519"):
    X25519PublicKey.register(rust_openssl.x25519.X25519PublicKey)


class X25519PrivateKey(metaclass=abc.ABCMeta):
    @classmethod
    def generate(cls) -> X25519PrivateKey:
        from cryptography.hazmat.backends.openssl.backend import backend

        if not backend.x25519_supported():
            raise UnsupportedAlgorithm(
                "X25519 is not supported by this version of OpenSSL.",
                _Reasons.UNSUPPORTED_EXCHANGE_ALGORITHM,
            )
        return backend.x25519_generate_key()

    @classmethod
    def from_private_bytes(cls, data: bytes) -> X25519PrivateKey:
        from cryptography.hazmat.backends.openssl.backend import backend

        if not backend.x25519_supported():
            raise UnsupportedAlgorithm(
                "X25519 is not supported by this version of OpenSSL.",
                _Reasons.UNSUPPORTED_EXCHANGE_ALGORITHM,
            )

        return backend.x25519_load_private_bytes(data)

    @abc.abstractmethod
    def public_key(self) -> X25519PublicKey:
        """
        Returns the public key assosciated with this private key
        """

    @abc.abstractmethod
    def private_bytes(
        self,
        encoding: _serialization.Encoding,
        format: _serialization.PrivateFormat,
        encryption_algorithm: _serialization.KeySerializationEncryption,
    ) -> bytes:
        """
        The serialized bytes of the private key.
        """

    @abc.abstractmethod
    def private_bytes_raw(self) -> bytes:
        """
        The raw bytes of the private key.
        Equivalent to private_bytes(Raw, Raw, NoEncryption()).
        """

    @abc.abstractmethod
    def exchange(self, peer_public_key: X25519PublicKey) -> bytes:
        """
        Performs a key exchange operation using the provided peer's public key.
        """


# For LibreSSL
if hasattr(rust_openssl, "x25519"):
    X25519PrivateKey.register(rust_openssl.x25519.X25519PrivateKey)