checksum

spbctf

Task: heavily protected, self-checksumming x86-64 ELF whose 'important calculations' are logged to /dev/null and discarded; on-disk patching triggers a tamper trap. Solution: bypass the self-checksum without touching the file by using an LD_PRELOAD shared object that hooks fopen/fwrite/vfprintf, mirroring the /dev/null log into a real file, then concatenate the 'The Target Result: N' byte values into the flag.