Solve fix 403 forbidden when dial with CDN edge IP with Custom SNI

[mebest100]

When dial with CDN edge IP with Custom SNI, such as url: wss://${cdn_edgeIP}:443/path, CDN will report 403 forbidden error

That is because CDN will verify both TLS SNI name and Host in request header , but your below code will take IP as Host in request header when dial with CDN edge IP

build_host(wsuri.host, wsuri.port, wsuri.secure)

Hence we need to correct this bug.
The test code as below:

import ssl
from websockets.client import connect
import asyncio
async def WssHandshake():
  
    server_host = '104.16.177.217' 
    server_port = 443  
    sni_hostname = 'testwebsocket.icanfly668.top'  

    
    ssl_context = ssl.create_default_context()


    headers = {
        'Host': sni_hostname,
        "User-agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/109.0.0.0 Safari/537.36"
    }

  
    uri = f"wss://{server_host}:{server_port}/ws"
    async with connect(uri=uri, ssl=ssl_context,server_hostname=sni_hostname, 
        extra_headers=headers, subprotocols=["chat"]) as websocket:
        await websocket.send("Hello, WebSocket with SNI!")
        response = await websocket.recv()
        print(response)

asyncio.run(WssHandshake())

I hv submitted the PR to fix this problem.
#1553

[aaugustin]

Try this: https://websockets.readthedocs.io/en/stable/faq/client.html#how-do-i-force-the-ip-address-that-the-client-connects-to

[aaugustin]

i.e. use host="<cdn_edgeIP>" to force the IP rather the Host header to force the host.

[mebest100]

Yes, it does work if take host parameter, but why?

I find below code seems relating to it.

     # If host and port are given, override values from the URI.
            host = kwargs.pop("host", host)
            port = kwargs.pop("port", port)
            create_connection = functools.partial(
                loop.create_connection, factory, host, port, **kwargs
            )

But I cannot find any clue why the given host can override values from the URI.
Could you explain it in details? Thx!

[aaugustin]

Please read the documentation. It's explained in https://websockets.readthedocs.io/en/stable/reference/asyncio/client.html