Problem: Potential man-in-the-middle attacks due to missing SSL certificate verification in the project codebase and used third-party libraries.
In the past, aiohttp-session/request had the parameter verify_ssl to control SSL certificate verification. This was a boolean value. In aiohttp 3.0, this parameter was deprecated in favor of the ssl parameter. Only when ssl is set to None or provided with a correct configured SSL context the standard SSL certificate verification will happen.
When migrating integrations in Home Assistant and libraries used by Home Assistant, in some cases the verify_ssl parameter value was just moved to the new ssl parameter. This resulted in these integrations and 3rd party libraries using request.ssl = True, which unintentionally turned off SSL certificate verification and opened up a man-in-the-middle attack vector.
When you scan the libraries used by the integrations in Home Assistant, you will find more issues like this.
The general handling in Home Assistant looks good, as homeassistant.helpers.aoihttp_client._async_get_connector handles it correctly.
host=expired.badssl.com, port=443, use-ssl=true, verify-ssl=true.Expected behavior:
ssl.SSLCertVerificationError.The following code shows the problem with ssl=True. No exception is raised when ssl=True (Python 3.11.6).
import asyncio
from ssl import SSLCertVerificationError
import aiohttp
BAD_URL = "https://expired.badssl.com/"
async def run_request(verify_ssl, result_placeholder: str):
async with aiohttp.ClientSession() as session:
exception_fired: bool = False
try:
await session.request("OPTIONS", BAD_URL, ssl=verify_ssl)
except SSLCertVerificationError:
exception_fired = True
except Exception as error:
print(error)
else:
exception_fired = False
print(result_placeholder.format(exception_result=exception_fired))
# Case 1: ssl=False --> expected result: No exception
asyncio.run(run_request(False, "Test case 1: expected result: False - result: {exception_result}"))
# Case 2: ssl=None --> expected result: Exception
asyncio.run(run_request(None, "Test case 2: expected result: True - result: {exception_result}"))
# Case 3: ssl=True --> expected result: No Exception
asyncio.run(run_request(True, "Test case 3: expected result: False - result: {exception_result}"))