dnsproxy-old-assignment.py

import sys
import socket
import ssl

class DNSproxy():
    def __init__(self):
        self.listen_addr   = '127.0.0.1'
        self.listen_port   = 1053
        self.upstream_dns  = '1.1.1.1'
        self.upstream_port = 853

    def port_listener(self):
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        try:
            s.bind((self.listen_addr, self.listen_port))
            print('Succcess!')
        except socket.error as e:
            # Replace with syslog
            print('[ERROR]: Socket bind failed. Err code: {} Message: {}').format(e[0], e[1])
            sys.exit()
        s.listen(10)
        while True:
            conn, addr = s.accept()
            print("{} {}").format(conn, addr)
            self.handle_conn(conn=conn)

    def handle_conn(self, conn):
        while True:
            data = conn.recv(1024)
            if data:
                resp = self.send_message(query=data)
                conn.sendall(resp)
                data = None
            else:
                break
        conn.close()

    def send_message(self, query, dns='1.1.1.1', ca_path='/etc/ssl/cert.pem'):
        server = (dns, 853)
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.settimeout(20)

        ctx = ssl.create_default_context()
        ctx = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
        ctx.verify_mode = ssl.CERT_REQUIRED
        ctx.check_hostname = False
        ctx.load_verify_locations(ca_path)

        wrapped_socket = ctx.wrap_socket(sock, server_hostname=dns)
        wrapped_socket.connect(server)
        print("Server peer certificate: %s", str(wrapped_socket.getpeercert()))

        tcp_msg = query
        print("Client request: %s", str(tcp_msg))
        wrapped_socket.send(tcp_msg)
        data = wrapped_socket.recv(1024)
        #print('Debug: {}').format(data)
        return data

d = DNSproxy()
d.port_listener()