A framework for testing SSL in a threaded environment

test_ssl.py

"""A framework for testing SSL in a threaded environment.
This script is built with a testing certificate authority in mind.
For this reason, I reccomend building this script into a derrivative
of my docker-python-ssl image for testing:
https://github.com/Kaezon/docker-python-ssl


The MIT License (MIT)
Copyright © 2021 Brett Costabile

Permission is hereby granted, free of charge, to any person obtaining a 
copy of this software and associated documentation files 
(the “Software”), to deal in the Software without restriction, 
including without limitation the rights to use, copy, modify, merge, 
publish, distribute, sublicense, and/or sell copies of the Software, 
and to permit persons to whom the Software is furnished to do so, 
subject to the following conditions:

The above copyright notice and this permission notice shall be included 
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS 
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, 
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE 
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
"""

import socket
import ssl
from threading import Thread

# Set values for sockets and test timeout
thread_timeout = 60
hostname = 'test-server'
port = 8443

# Certificate paths
path_root_cert = '/var/certs/testCA.pem'
path_server_cert = '/var/certs/server.crt'
path_server_key = '/var/certs/server.key'


# Define client and server functions
def run_client(server_hostname: str,
               server_port: int,
               path_root_cert: str) -> None:
    """Connect to a server using SSL.
    This function will attempt to connect to an SSL socket and then
    immediately return.

    Args:
        server_hostname (str): The hostname to connect to
        server_port (int): The port to connect to
        path_root_cert (str): Path to the root certificate
    """
    print(f'Attempting to connect to {server_hostname} on port {server_port}')

    context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
    context.load_verify_locations('/var/certs/testCA.pem')

    with socket.create_connection((server_hostname, server_port)) as sock:
        with context.wrap_socket(
                sock, server_hostname=server_hostname) as ssock:
            print('Client connected')


def run_server(hostname: str,
               port: int,
               path_server_cert: str,
               path_server_key: str) -> None:
    """Listen for SSL connections.
    This function will wait indenfinately for a connection. Once a
    client connects, the connection's origin address will be printed,
    then the function will return.

    Args:
        hostname (str): The hostname to bind to
        port (int): The port to bind to
        path_server_cert (str): Path to the server's certificate
        path_server_key (str): Path to the server's private key
    """
    print(f'Starting server on port {port}, '
          f'listening for connections to {hostname}')

    context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
    context.load_cert_chain('/var/certs/server.crt',
                            '/var/certs/server.key')

    with socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) as sock:
        sock.bind((hostname, port))
        sock.listen(5)
        with context.wrap_socket(sock, server_side=True) as ssock:
            conn, addr = ssock.accept()
            print(f'Server got connection from {addr}')


# Instantiate Thread objects
server_thread = Thread(
    target=run_server,
    args=(hostname, port, path_server_cert, path_server_key),
    daemon=False)

client_thread = Thread(
    target=run_client,
    args=(hostname, port, path_root_cert),
    daemon=False)

# Start threads
server_thread.start()
client_thread.start()

# Wait for server thread to stop or time out
server_thread.join(timeout=thread_timeout)
if server_thread.is_alive():
    print(f'Server thread timed out after {thread_timeout}')