Nintendo Switch RSA-PKCS#1 Public Key Recovery
This is a short writeup of a fun (but ultimately pretty useless) attack I implemented on the Nintendo Switch a few months ago resulting in the recovery of some otherwise unobtainable RSA public keys. Since public keys aren't private keys, this is pretty useless, apart from letting us validate some signatures on PC. Even so, the attack is a pretty cool one, so I thought I'd write it up.
Every Switch gamecart has a unique certificate (called its "CERT"), storing an RSA signature followed by some kind of unknown but unique encrypted data. I was trying to reverse how these certificates work, and the obvious first step was to try to see how they were validated. However, when I tried looking through the FileSystem (FS) module, which should be responsible for validating these certificates, I found no references to the format at all. The "CERT" magic number was nowhere to be seen, and I couldn't find an RSA modulus that validated the signatures I had. This was in