How do I respond to a "CONNECT" method request in a proxy server using socket in python?

Question

I am currently programming a proxy server using httplib, and when I try to connect to HTTPS websites (such as facebook and google) my client sends me "CONNECT" requests that look like this:

CONNECT www.google.co.il:443 HTTP/1.1\r\n
User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:35.0) Gecko/20100101 Firefox/35.0\r\n
Proxy-Connection: keep-alive\r\n
Connection: keep-alive\r\n
Host: www.google.co.il:443\r\n
\r\n

I took a working proxy from the internet and put it on, then sniffed the network on wireshark, and the response to this request should look this way:

HTTP/1.1 200 Connection established\n
Proxy-agent: Python Proxy/0.1.0 Draft 1\n
\n

I noticed that the client sends the request to the proxy itself, so I decided to use socket, and send the response to the client in this way:

if getmethod(clientreq) is "CONNECT":
    text="HTTP/1.1 200 Connection established\nProxy-Agent: THE BB Proxy\n\n"
    client.send(text)

I really hoped that handling those "CONNECT" requests would be the solution and that my server will finally take care of HTTPS requests but it doesn't, and the response packets that I send to the client don't even appear on wireshark.

So my questions are: 1. What does the "CONNECT" method really do? 2. What else do I need except handling "CONNECT" method requests in order to communicate with a HTTPS servers?

Answer 1

I am replying after this long time because I recently worked with this concept. It may help others.

To work with CONNECT http method proxy need to create socket connection with the server's https port (ex. 443). Once connection is established you can send "HTTP/1.1 200 Connection established" as response.

After this client and server with communicate with each other through proxy. Proxy has to just transfer data from client socket to server socket and vice versa. Client and server will exchange certificate information for handshaking, once handshaking is done they will start sharing data in encrypted format so proxy will not be able to understand anything.

May the following code helps you.

def _read_write(self):
    socs = [self.client, self.target]
    count = 0
    while 1:
        count += 1
        (recv, _, error) = select.select(socs, [], socs, 3)
        if error:
            break
        if recv:
            for in_ in recv:
                data = in_.recv(BUFLEN)
                if in_ is self.client:
                    out = self.target
                else:
                    out = self.client
                if data:
                    out.send(data)
                    print(data)
                    count = 0
        if count == time_out_max:
            break

Hope this answer helps anyone in need. As I had to go through a lot of things to find this answer.