How can I specify a map_remote rule in mitmproxy to redirect from a remote HTTPS URL to an HTTP URL?

Question

I'd like to set up a map_remote rewrite from an https address to my local machine running a service on http only.

The documentation for the option (https://docs.mitmproxy.org/stable/concepts-options/) seems to indicate I should do this

mitmproxy --map-remote "|https://foo.bar.com|http://localhost:8081|"

But this doesn't seem to rewrite any requests.

What's the correct syntax to accomplish this?

Answer 1

The problem in your example is the trailing |. Map Remote specifications can either be:

• |flow-filter|url-regex|replacement or
• |url-regex|replacement

By append a final | to your two-part spec, you inadvertedly use the first form, and https://foo.bar.com is applied as the filter and not as the url regex. Long story short:

mitmproxy --map-remote "|https://foo.bar.com|http://localhost:8081|"  # wrong
mitmproxy --map-remote "|https://foo.bar.com|http://localhost:8081"   # correct

You may also find the extended feature documentation at https://docs.mitmproxy.org/stable/overview-features/#map-remote helpful. :)