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#!/usr/bin/env python

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# -*- coding: utf-8 -*-

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# Written by Edouard TISSERANT (C) 2024

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# This file is part of Beremiz IDE

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# See COPYING file for copyrights details.

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"""

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The TLS-PSK adapter that handles SSL connections instead of regular sockets,

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but using Pre Shared Keys instead of Certificates

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Corresponding stunnel.conf on PLC side:

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    [ERPCPSK]

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    accept = 4000

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    connect = 127.0.0.1:3000

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    ciphers = PSK

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    sslVersion = TLSv1.2

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    PSKsecrets = psk.txt

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"""

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import socket

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import ssl

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try:

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    import sslpsk

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except ImportError as e:

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    sslpsk = None

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from erpc.transport import TCPTransport

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class SSLPSKClientTransport(TCPTransport):

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    def __init__(self, host, port, psk):

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        """ overrides TCPTransport's __init__ to wrap socket in SSl wrapper """

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        super(TCPTransport, self).__init__()

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        self._host = host

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        self._port = port

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        self._sock = None

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        self._isServer = False

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        if sslpsk is None:

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             raise ImportError("sslpsk module is not available")

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        self.sslpskctx = sslpsk.SSLPSKContext(ssl.PROTOCOL_TLSv1_2)

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        self.sslpskctx.set_ciphers('PSK')

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        self.sslpskctx.psk = psk

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        raw_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

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        raw_sock.setsockopt(socket.SOL_TCP, socket.TCP_NODELAY, 1)

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        raw_sock.connect((self._host, self._port))

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        self._sock = self.sslpskctx.wrap_socket(raw_sock, server_side=False)

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