#!/usr/bin/env python3.7
#
# Copyright (c) 2013-2024 by Ron Frederick <ronf@timeheart.net> and others.
#
# This program and the accompanying materials are made available under
# the terms of the Eclipse Public License v2.0 which accompanies this
# distribution and is available at:
#
#     http://www.eclipse.org/legal/epl-2.0/
#
# This program may also be made available under the following secondary
# licenses when the conditions for such availability set forth in the
# Eclipse Public License v2.0 are satisfied:
#
#    GNU General Public License, Version 2.0, or any later versions of
#    that license
#
# SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
#
# Contributors:
#     Ron Frederick - initial implementation, API, and documentation

# To run this program, the file ``ssh_host_key`` must exist with an SSH
# private key in it to use as a server host key. An SSH host certificate
# can optionally be provided in the file ``ssh_host_key-cert.pub``.

import asyncio
import sys
from typing import Optional

import asyncssh
import bcrypt

passwords = {
    "guest": b"",  # guest account with no password
    "user": bcrypt.hashpw(b"user", bcrypt.gensalt()),
}


def handle_client(process: asyncssh.SSHServerProcess) -> None:
    username = process.get_extra_info("username")
    process.stdout.write(f"Welcome to my SSH server, {username}!\n")
    # process.exit(0)


class MySSHServer(asyncssh.SSHServer):
    def connection_made(self, conn: asyncssh.SSHServerConnection) -> None:
        peername = conn.get_extra_info("peername")[0]
        print(f"SSH connection received from {peername}.")

    def connection_lost(self, exc: Optional[Exception]) -> None:
        if exc:
            print("SSH connection error: " + str(exc), file=sys.stderr)
        else:
            print("SSH connection closed.")

    def begin_auth(self, username: str) -> bool:
        # If the user's password is the empty string, no auth is required
        return passwords.get(username) != b""

    def password_auth_supported(self) -> bool:
        return True

    def validate_password(self, username: str, password: str) -> bool:
        if username not in passwords:
            return False
        pw = passwords[username]
        if not password and not pw:
            return True
        return bcrypt.checkpw(password.encode("utf-8"), pw)


async def start_server() -> None:
    await asyncssh.create_server(
        MySSHServer,
        "",
        2231,
        server_host_keys=["ssh_host_key"],
        process_factory=handle_client,
    )


loop = asyncio.new_event_loop()

try:
    loop.run_until_complete(start_server())
except (OSError, asyncssh.Error) as exc:
    sys.exit("Error starting server: " + str(exc))

loop.run_forever()
