How to do domain fronting in Python with Requests. Send a request to an arbitrary IP address and force the SNI field and Host HTTP header to a certain value.

domain_fronting.py

#
# How to do domain fronting in Python with Requests.
#
# Send a request to an arbitrary IP address and force the
# SNI field and Host HTTP header to a certain value. 
#
import http.client

import requests
import urllib3
from requests.adapters import HTTPAdapter

http.client.HTTPConnection.debuglevel = 5
urllib3.add_stderr_logger()


class FrontingAdapter(HTTPAdapter):
    """"Transport adapter" that allows us to use SSLv3."""

    def __init__(self, fronted_domain=None, **kwargs):
        self.fronted_domain = fronted_domain
        super(FrontingAdapter, self).__init__(**kwargs)

    def send(self, request, **kwargs):
        connection_pool_kwargs = self.poolmanager.connection_pool_kw
        if self.fronted_domain:
            connection_pool_kwargs["assert_hostname"] = self.fronted_domain
        elif "assert_hostname" in connection_pool_kwargs:
            connection_pool_kwargs.pop("assert_hostname", None)
        return super(FrontingAdapter, self).send(request, **kwargs)

    def init_poolmanager(self, *args, **kwargs):
        server_hostname = None
        if self.fronted_domain:
            server_hostname = self.fronted_domain
        super(FrontingAdapter, self).init_poolmanager(server_hostname=server_hostname, *args, **kwargs)


# Based on the domain fronting example at https://digi.ninja/blog/cloudfront_example.php
s = requests.Session()
s.mount('https://', FrontingAdapter(fronted_domain="fronted.digi.ninja"))
r = s.get("https://54.230.14.90/", headers={"Host": "d1sdh26o090vk5.cloudfront.net"})
print()
print(r.content)

It's awesome, but is there a way not to expose mytest.com? What we are experiencing is that the request is rejected based on the domain visible in the client hello.

After a small amount of experimentation, it seems that this can be trimmed down to a one-liner (as of June 2022):

session.get_adapter('https://').poolmanager.connection_pool_kw['assert_hostname'] = 'my-fake-hostname-here'

It's great! But I also need to set server_hostname for it to take effect. （Python3.7, requests == 2.28.1)

s = requests.Session()
s.get_adapter('https://').poolmanager.connection_pool_kw['server_hostname'] = "mytest.com"
s.get_adapter('https://').poolmanager.connection_pool_kw['assert_hostname'] = "mytest.com"

r = s.get("https://93.184.216.34", headers= {"Host": "mytest.com"})
print(r.content)