Re:Curl those funny IPv4 addresses
by cmeacham98 on Monday April 19, 2021 @10:54AM
(#26863399)
Question: how did this trick help you bypass the proxy?
The only way I can think of this possibly helping you is by changing the Host header and that somehow fooling the proxy into allowing your connection through. However some random testing with both a modern browser and a really old version of firefox I have installed shows that it seems to convert the 'weird number format' into a proper IP address, even when using a proxy. In other words, I cannot see how using these weird IPs ever could make a difference from the proxy's perspective.
When I was in middle school, I needed to research a paper in the school library computers. Their stupid computers were always messed up; first the proxy settings weren't configured in half the machines (I fixed that, and got scolded), then the anti-virus wasn't working (fixed that, got scolded). Then the proxies wouldn't let me search for my paper.
I was a budding hacker, so I figured out the numbering trick mentioned in this article, and was able to bypass the proxy and do my research for my paper. This was a long time ago but I bet the same situation is just as relevant today. (Doubtful that you'd use curl in this scenario, but nice to know they are preserving useful functionality rather than throwing it out)