After days of reversing a certain x86-64 target running Linux, you're finally able to execute up to 64 bytes of shellcode. You also know the location of a function (0xAAAAAAAAAAAA) that will store a username and password. You can then use these credentials to retrieve the flag. Thankfully, symbols were left in.
NOTE: The format of the flag is ATR[], for example: ATR[foobar]. The flag must be submitted in full, including the ATR and square bracket parts.
The hint is in the file ".hint"