Use mitmproxy with GNOME Web (Epiphany)

To use mitmproxy with Epiphany you need to install CA certificate from mitmproxy. To do that, start mitmproxy and navigate to mitm.it. Download *.pem certificate (available under Other link). Install mitmproxy certificate with command:

sudo trust anchor mitmproxy-ca-cert.pem 

With this command you can also install any custom certificate to use in Epiphany.

Overwrite response body with mitmproxy 2

Run python script with mitmproxy:

mitmproxy --ignore ws.sitesupport.net:443 -s script.py

Script example:

from mitmproxy.script import concurrent

OLD = """var totalExpGems=0;"""
NEW = """var totalExpGems=0;debugger;"""


@concurrent
def response(flow):
    if "gem_finder" in flow.request.path:
        flow.response.headers["XX"] = "PATCHED"
        body = flow.response.content.decode("utf-8")
        if OLD in body:
            flow.response.content = body.replace(OLD, NEW).encode("utf-8")
            flow.response.headers["XXX"] = "PATCHED"

Overwrite response body with mitmproxy

It is possible to run python script with mitmproxy. For example:

mitmproxy -s "modify_response_body.py"

The modification process is very simple. Take a look at the modify_response_body.py code:

from mitmproxy.models import decoded


def response(context, flow):
    if "site.custom.min.js" in flow.request.path:
        with decoded(flow.response):  # automatically decode gzipped responses.
            flow.response.content = flow.response.content.replace(
                "surfly.com",
                "sitesupport.net")

The script will look for a request with path that contains site.custom.min.js and replace all occurences of surfly.com with sitesupport.net

mitmproxy and websocket connections

mitmproxy does not really supports websocket connections. However, there is a workaround: it is possible to just ignore them. For example all your websocket conections are encrypted and go to the special subdomain:

mitmproxy --ignore ws.sitesupport.net:443