Overview
Reversing a binary where the password/flag is constructed dynamically at runtime through sequential byte assignments rather than static strings.
Reconnaissance
Running strings on auth_bin yields no flag. Disassembling with objdump or Ghidra reveals individual byte assignments to stack locations.
Exploitation Strategy
Locate the function responsible for printing the flag and map out byte assignments (e.g. mov byte ptr [rbp-0x20], 0x68, 0x77, 0x6a...). Converting hex values to ASCII reconstructs the flag.
Solution Code
objdump -Mintel -d auth_bin > disasm.txt
# Inspect byte assignments:
# 0x68 -> 'h', 0x77 -> 'w', 0x6a -> 'j', 0x7b -> '{' ...
# Reconstructed: hwj{n0_5tr1ng5_at_runt1m3}Flag
hwj{n0_5tr1ng5_at_runt1m3}