I have tinyproxy installed on localhost (I also tried squid and failed similarly). It runs on port 8888. This works:
curl -x localhost:8888 http://www.google.com
And I see output in the tinyproxy logs.
Now I run the latest version of ngrok and get the following forwarding established:
http://<identifier>.ngrok.io -> localhost:8888
If I open http://<identifier>.ngrok.io on my browser the ngrok connection counter goes up, and I successfully see tinyproxy's "not implemented" error page.
However, this fails:
curl -x <identifier>.ngrok.io:80 http://www.google.com
# => curl: (56) Received HTTP code 404 from proxy after CONNECT
The ngrok counter does not go up, and I do not see messages in the tinyproxy logs, suggesting that the failure is before ngrok accepted the connection.
What am I missing here? I had assumed that both ngrok and tinyproxy forward the HTTP request, but it seems like there might be another protocol operating behind the scenes of curl -x. Is there a way to successfully establish the proxy chain starting at ngrok and going through my localhost?