#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <openssl/md5.h>

// compile: gcc -o subhash subhash.c -lcrypto -O2 -Wall
// by atom

int main(int argc, char *argv[])
{
  if (argc != 2)
  {
    fprintf (stderr, "Usage: %s hash\n", argv[0]);

    return -1;
  }

  uint32_t target;

  if (sscanf (argv[1], "%08x", &target) != 1)
  {
    fprintf (stderr, "Something is wrong with your hash: %s", argv[1]);

    return -1;
  }

  target = __builtin_bswap32 (target);

  char buf[BUFSIZ];

  while (fgets (buf, BUFSIZ, stdin))
  {
    uint32_t digest[4];

    MD5_CTX c;

    MD5_Init (&c);

    MD5_Update (&c, buf, strlen (buf) - 1);

    MD5_Final ((unsigned char *) digest, &c);

    if (target != digest[0]) continue;

    printf ("Password matches: %s", buf);

    break;
  }

  return 0;
}