p club secy task -- infosec
841f980abd04b26fe804ca0c207a574bef504cb6a3c3599a449e845ca993d2cf
ltrace and strace didnt give anything very usefull after some crude and adhoc attempts; so i tried radare2
running:
r2 -d ./rev hi
aaa
afl
revealed a function sym.print_flag. However sadly pdf @main further revealed that main didnt contain any entry point for the print function.
So now I just had to guide the flow of the program and make it enter print_flag to capture the flag.
Stopping main before entering printf by adding a breakpoint db 0x08048581 ; setting eip to sym.print_flag by dr eip = 0x0804849c
(followed by respective dc s) made the program print a perfect 64 digit hexadecimal;
or a 256 bit binary which had to be the required SHA256 hash.
r2 -d ./rev hi
aaa
afl
pdf @main
db 0x08048581
dc
dr eip = 0x0804849c
dc