mylogin.c

#define _BSD_SOURCE /* Get getpass() declaration from <unistd.h> */
#define _XOPEN_SOURCE /* Get crypt() declaration from <unistd.h> */
#include <unistd.h>
#include <limits.h>
#include <pwd.h>
#include <shadow.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <string.h>
#include <errno.h>
#include <termios.h>
#include <crypt.h>
#include "pwdblib.h"


int main(int argc, char const *argv[])
{
  char *username, *password, *encrypted, *p;
  struct pwdb_passwd *pwd;
  int authOk;
  size_t len;
  long lnmax;

  lnmax = sysconf(_SC_LOGIN_NAME_MAX);
  if (lnmax == -1)							/* If limit is indeterminate */
    lnmax = 256;							/* make a guess */

  username = malloc(lnmax);
  if (username == NULL)
    perror("malloc");

  while (1) {
    printf("login: ");
    fflush(stdout);
    if (fgets(username, lnmax, stdin) == NULL)
      exit(EXIT_FAILURE);

    len = strlen(username);
    if (username[len - 1] == '\n')
      username[len - 1] = '\0';				/* Remove trailing 'n'*/

    pwd = pwdb_getpwnam(username);
    int found_user = 1;
    if (pwd == NULL) {
      //printf("pwd null\n");
      if (pwdb_errno == PWDB_NOUSER) {
        // No user found...
        //printf("No user found...");
        found_user = -1;
        //exit(EXIT_FAILURE);
      }

      if (pwdb_errno == PWDB_FILEERR) {
        perror("can't read pwdb file");
        exit(EXIT_FAILURE);
      }

      if (pwdb_errno == PWDB_MEMERR) {
        perror("out of memory");
        exit(EXIT_FAILURE);
      }

      if (pwdb_errno == PWDB_ENTRERR) {
        perror("pwdb entry corrupt");
        exit(EXIT_FAILURE);
      } 
    }
     
    password = getpass("Password: ");

    /* Encrypt password and erase cleartext version immediately */
    if (found_user == 1) {
      encrypted = crypt(password, pwd->pw_passwd);
      for (p = password; *p != '\0'; ) {
        *p++ = '\0';
      }

      if (encrypted == NULL)
        perror("crypt");
    
      authOk = strcmp(encrypted, pwd->pw_passwd) == 0;
    }

    if (!authOk || found_user == -1) {
      printf("Unknown user or incorrect password\n");
      if (found_user == 1) {
        pwd->pw_failed++;  
        printf("failed...\n");
      }

      if (pwd->pw_age >= 5) {
        pwd->pw_passwd[0] = '*';
        pwd->pw_passwd[1] = '\0';
        printf("locking out...\n");
      }

      if (pwdb_update_user(pwd) != 0) {
          printf("pwfile corrupt");
          exit(EXIT_FAILURE);
        }
      //free(pwd);
      //free(spwd);
      //free(password);
      //free(encrypted);
      continue;
    }

    pwd->pw_failed = 0;
    pwd->pw_age++;
    printf("resetting fails, increasing age... %d\n", pwd->pw_age);

    if (pwdb_update_user(pwd) != 0) {
      printf("pwfile corrupt");
      exit(EXIT_FAILURE);
    }

    printf("User authenticated successfully\n");

    return 0;
  }
}