CPUID

spbctf

Task: ELF64 PIE reverse challenge that reads the CPU vendor via CPUID leaf 0 twice (with a 'swap the processor' prompt in between) and permutes the vendor-string bytes into a 31-char flag. Solution: reverse the fixed byte permutation from the disassembly of main and feed AuthenticAMD (1st read) then GenuineIntel (2nd read) to reproduce the flag; verified with a Python simulator, Unicorn CPUID hook, and QEMU vendor override.