#include <security/pam_modules.h>

#include <stdlib.h>
#include <stdio.h>
#include <time.h>

#ifdef PRINT
#undef PRINT
#endif

#ifdef DEBUG_PRINT_ENABLED
 #include <stdio.h>
 #define PRINT(x) printf x;
#else
 #define PRINT(x)
#endif

#define MIN_X -20
#define MAX_X 20

#define MIN_A -10
#define MAX_A 10

PAM_EXTERN int pam_sm_authenticate(pam_handle_t * pamh, int flags, int argc, const char **argv) {
 int retval;
 const char *name;

 int a, b, c, x1, x2;

 retval = pam_get_user(pamh, &name;, NULL);
 PRINT(("Obtained username: %s\n", name));

 {
  struct pam_message msg[2], *pmsg[2];
  struct pam_response *resp;

  const char *promptx[] = { "x1 = ", "x2 = " };

  srand(time(NULL));

  x1 = MIN_X + rand() % (MAX_X - MIN_X - 1);
  x2 = MIN_X + rand() % (MAX_X - MIN_X - 1);

  while (!(a = MIN_A + rand() % (MAX_A - MIN_A - 1)));
  b = (-1) * (x1 + x2) * a;
  c = x1 * x2 * a;

  printf("%dx^2%+dx%+d=0\n", a, b, c);

  pmsg[0] = &msg;[0];
  msg[0].msg_style = PAM_PROMPT_ECHO_ON;
  msg[0].msg = promptx[0];

  pmsg[1] = &msg;[1];
  msg[1].msg_style = PAM_PROMPT_ECHO_ON;
  msg[1].msg = promptx[1];

  {
   struct pam_conv *conv;
   int y1, y2;

   pam_get_item(pamh, PAM_CONV, (const void **) &conv;);
   
   conv->conv(2, (const struct pam_message **) pmsg, &resp;, conv->appdata_ptr);

   y1 = atoi(resp[0].resp);
   y2 = atoi(resp[1].resp);

   if (x1 == y1 && x2 == y2 || x1 == y2 && x2 == y1)
    return PAM_SUCCESS;   
  }
 }
 
 return PAM_AUTH_ERR;
}

PAM_EXTERN int pam_sm_setcred(pam_handle_t *pamh, int flags, int argc, const char **argv) {
 return PAM_SUCCESS;
}

#ifdef PAM_STATIC
struct pam_module _pam_quadec_modstruct = {
 "pam_quadeq",
 pam_sm_authenticate,
 pam_sm_setcred,
 NULL,
 NULL,
 NULL,
 NULL,
};
#endif