Proxomitron Reborn

[amy]

(Jul. 23, 2024 03:40 AM)rasczak Wrote:  Noticed a problem loading this site: www. fs.usda.gov

- Using reborn 4701 with new 3.0 openssl dlls
---- It looked like it would start to load normally, then it would ping-pong tcp 'keep alive' and 'window update' packets back and forth until my machine sent a tcp reset and then the site would stop responding with no resources transmitted to my browser (site doesn't load at all) and proxo keeps the connection open. (Abort button hangs proxo and requires killing the process.)

- Using reborn 4701 with old 1.0 openssl dlls
---- It looked like it would start to load normally, then it would ping-pong tcp 'keep alive' and 'window update' packets back and forth for a bit, then load the site. Then go back to ping-pong for a bit, then stop. Proxo wouldn't close the connection.

- Bypassing reborn 4701 loads the site normally.
- Old proxomitron and 1.0 openssl dlls loads the site normally..

That looks like a site which appears to discriminate based on user-agent header. If I don't send any UA header it hangs too, and if I send some non-standard or old UA, it also hangs. However, I can confirm that this one works:

Code:

User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:45.0) Gecko/20100101 Firefox/80.0

A useful tip for troubleshooting is to bypass outgoing header filters, which lets Proxomitron still handle the TLS negotiation with the site and filter incoming content, but otherwise outgoing headers from the browser remain unfiltered. You can also bypass incoming and page filters if you suspect those are the cause. If bypassing all filtering doesn't work but "full" bypass (i.e. Bypass button) does, then it's probably some form of TLS fingerprinting (which I'm still working on a solution to); if a site works with outgoing header filtering bypassed, then it's probably some filter you have which is altering outgoing headers in a way that the remote server doesn't like.