I am writing a program that encrypts data in Python and heard about padding oracle attacks, but I think they are overrated (I mean, what are the real-world uses?) even for the old implementations that are vulnerable (the ones that tell if padding is right or wrong like SSLv3).
- If all I need are two ciphertexts $c(n-1)$, $c(n)$ which are the last two encrypted messages blocks, and a server to tell me if the padding of decrypted $c(n)$is correct or whatever, doesn't that mean that the server just decrypts whatever you send to it (I mean, just send the whole encrypted message as you received it and read the output). I mean, this is the server bug that it doesn't take a key in the first place and check if it's correct.
- Let's assume that all we have to do is send those two cipher messages to know and decrypt the last block (the padding block). This only works since the padding plaintext is known or at least not random or whatever reason.
But what about, say, c2 and c3 which are in the middle of the whole message? We know c3 and c2, but we don't know and we will never know either p3 or p2 (plaintext), nor the intermediate state IS3; i.e. we can't XOR c2 with is3 to obtain p3, so this attack I think only allow us to decrypt the padding block with the only new thing we actually knew is an intermediate state of padding block.
I am asking to know if this attack is just a one with no real-world implications and no real data decryption capabilities (actual data).