/*	Routines to read and write the /etc/utmp file.			*/
/*									*/

#include	<sys/types.h>
#include	<sys/stat.h>
#include	<utmp.h>
#include	<errno.h>

#define	TRUE	1
#define	FALSE	0
#define	FAILURE	-1

#define NULL	0

#define	MAXFILE	79	/* Maximum pathname length for "utmp" file */

#ifdef	DEBUG

#undef	UTMP_FILE
#define	UTMP_FILE "utmp"

#endif

static int fd = FAILURE ;	/* File descriptor for the utmp file. */
static char utmpfile[MAXFILE+1] = UTMP_FILE ;	/* Name of the current
						 * "utmp" like file.
						 */
static char utmplock[MAXFILE+5] ;
static long loc_utmp ;	/* Where in "utmp" the current "ubuf" was
			 * found.
			 */
static struct utmp ubuf ;	/* Copy of last entry read in. */

/*	"getutent" gets the next entry in the utmp file.		*/

struct utmp *getutent()
  {
	extern int fd ;
	extern char utmpfile[] ;
	extern struct utmp ubuf ;
	extern long loc_utmp,lseek() ;
	extern int errno ;
	register char *u ;
	register int i ;

/*	If the "utmp" file is not open, attempt to open it for		*/
/*	reading.  If there is no file, attempt to create one.  If	*/
/*	both attempts fail, return NULL.  If the file exists, but	*/
/*	isn't readable and writeable, do not attempt to create.		*/

	if (fd == FAILURE)
	  {
	    if ((fd = open(&utmpfile[0],2)) == FAILURE)
	      {
/*	If the open failed because the file didn't exist, then try to	*/
/*	create one.							*/

		if (errno == ENOENT)
		  {
		    if (creat(&utmpfile[0],0644) == FAILURE) return(NULL) ;
		    close(fd) ;
		    if ((fd = open(&utmpfile[0],2)) == FAILURE) return(NULL) ;
		  }

/*	If the open failed for permissions, try opening it only for	*/
/*	reading.  All "pututline()" later will fail the writes.		*/

		else if (errno == EACCES)
		  {
		    if ((fd = open(&utmpfile[0],0)) == FAILURE) return(NULL) ;
		  }

		else return(NULL) ;
	      }
	  }

/*	Try to read in the next entry from the utmp file.  If the	*/
/*	read fails, return NULL.					*/

	if (read(fd,&ubuf,sizeof(ubuf)) != sizeof(ubuf))
	  {

/*	Make sure ubuf is zeroed.					*/

	    for (i=0,u= (char *)(&ubuf); i < sizeof(ubuf)
		; i++) *u++ = '\0' ;
	    loc_utmp = 0 ;
	    return(NULL) ;
	  }

/*	Save the location in the file where this entry was found.	*/

	loc_utmp = lseek(fd,0L,1) - (long)(sizeof(struct utmp)) ;
	return(&ubuf) ;
  }

/*	"getutid" finds the specified entry in the utmp file.  If	*/
/*	it can't find it, it returns NULL.				*/

struct utmp *getutid(entry)

register struct utmp *entry ;

  {
	extern struct utmp ubuf ;
	struct utmp *getutent() ;
	register short type ;

/*	Start looking for entry.  Look in our current buffer before	*/
/*	reading in new entries.						*/

	do
	  {
/*	If there is no entry in "ubuf", skip to the read.		*/

	    if (ubuf.ut_time != 0)
	      {
		   if (strncmp(ubuf.ut_name,entry->ut_name,8)==0)
			return(&ubuf) ;
		    break ;
	      }
	  }
	while (getutent() != NULL) ;

/*	Return NULL since the proper entry wasn't found.		*/

	return(NULL) ;
  }

/*	"getutline" searches the "utmp" file for a LOGIN_PROCESS or	*/
/*	USER_PROCESS with the same "line" as the specified "entry".	*/

struct utmp *getutline(entry)

register struct utmp *entry ;

  {
	extern struct utmp ubuf,*getutent() ;
	register struct utmp *cur ;

/*	Start by using the entry currently incore.  This prevents	*/
/*	doing reads that aren't necessary.				*/

	cur = &ubuf ;
	do
	  {
/*	If the current entry is the one we are interested in, return	*/
/*	a pointer to it.						*/

	    if (strncmp(entry->ut_line,cur->ut_line,8) == 0) return(cur) ;
	  }
	while ((cur = getutent()) != NULL) ;

/*	Since entry wasn't found, return NULL.				*/

	return(NULL) ;
  }

/*	"pututline" writes the structure sent into the utmp file.	*/
/*	If there is already an entry with the same id, then it is	*/
/*	overwritten, otherwise a new entry is made at the end of the	*/
/*	utmp file.							*/

struct utmp *pututline(entry)

struct utmp *entry ;

  {
	register int i,type ;
	struct utmp *answer ;
	struct stat statbuf ;
	extern long time() ;
	extern struct utmp ubuf ;
	extern long loc_utmp,lseek() ;
	extern struct utmp *getutid() ;
	extern int fd,errno ;
	struct utmp tmpbuf ;

/*	Copy the user supplied entry into our temporary buffer to	*/
/*	avoid the possibility that the user is actually passing us	*/
/*	the address of "ubuf".						*/

	tmpbuf = *entry ;

/*	Create a lock link file before attempting to modify the utmp	*/
/*	file.  Wait for up to sixty seconds, but then continue		*/
/*	regardless of the lock file. If sixty seconds isn't enough time,*/
/*	the original creator of the lock probably has died.		*/

	sprintf(&utmplock[0],"%s.lck",&utmpfile[0]) ;
	while (link(&utmpfile[0],&utmplock[0]) == FAILURE)
	  {
	    if (errno == EEXIST)
	      {
		if (stat(&utmpfile[0],&statbuf) != FAILURE)
		  {
		    if (time(0) - statbuf.st_ctime > 60) unlink(&utmplock[0]) ;
		    else sleep(3) ;
		  }
	      }
	    else if (errno == ENOENT)
	      {
/*	If the utmp file doesn't exist, make one by trying to find the	*/
/*	entry of interest.  "getutent()" will create the file.		*/

		getutent() ;
		if (fd == FAILURE)
		  {
#ifdef	ERRDEBUG
		    gdebug("pututline: Unable to create utmp file.\n") ;
#endif
		    return((struct utmp *)NULL) ;
		  }
	      }
	    else
	      {
#ifdef	ERRDEBUG
		gdebug("pututline failed: link of lock file failed-%d",errno) ;
#endif
		return((struct utmp *)NULL) ;
	      }
	  }

/*	Find the proper entry in the utmp file.  Start at the current	*/
/*	location.  If it isn't found from here to the end of the	*/
/*	file, then reset to the beginning of the file and try again.	*/
/*	If it still isn't found, then write a new entry at the end of	*/
/*	the file.  (Making sure the location is an integral number of	*/
/*	utmp structures into the file incase the file is scribbled.)	*/

	if (getutid(&tmpbuf) == NULL)
	  {
#ifdef	ERRDEBUG
	    gdebug("First getutid() failed.  fd: %d",fd) ;
#endif
	    setutent() ;
	    if (getutid(&tmpbuf) == NULL)
	      {
		loc_utmp = lseek(fd,0L,1) ;
		loc_utmp -= loc_utmp % sizeof(struct utmp) ;
#ifdef	ERRDEBUG
		gdebug("Second getutid() failed.  fd: %d loc_utmp: %ld\n",
		    fd,loc_utmp) ;
#endif
	      }
	  }

/*	Seek to the proper place on the file descriptor for writing.	*/

	lseek(fd,loc_utmp,0) ;

/*	Write out the user supplied structure.  If the write fails,	*/
/*	then the user probably doesn't have permission to write the	*/
/*	utmp file.							*/

	if (write(fd,&tmpbuf,sizeof(tmpbuf)) != sizeof(tmpbuf))
	  {
#ifdef	ERRDEBUG
	    gdebug("pututline failed: write-%d\n",errno) ;
#endif
	    answer = (struct utmp *)NULL ;
	  }
	else
	  {
/*	Copy the user structure into ubuf so that it will be up to	*/
/*	date in the future.						*/

	    ubuf = tmpbuf ;
	    answer = &ubuf ;

#ifdef	ERRDEBUG
	    gdebug("id: %c%c loc: %x\n",ubuf.ut_id[0],ubuf.ut_id[1],
		ubuf.ut_id[2],ubuf.ut_id[3],loc_utmp) ;
#endif
	  }

/*	Remove the lock file (even if it wasn't your own creation).	*/

	unlink(&utmplock[0]) ;
	return(answer) ;
  }

/*	"setutent" just resets the utmp file back to the beginning.	*/

setutent()
  {
	register char *ptr ;
	register int i ;
	extern int fd ;
	extern struct utmp ubuf ;
	extern long loc_utmp ;

	if (fd != FAILURE) lseek(fd,0L,0) ;

/*	Zero the stored copy of the last entry read, since we are	*/
/*	resetting to the beginning of the file.				*/

	for (i=0,ptr=(char*)&ubuf; i < sizeof(ubuf) ;i++) *ptr++ = '\0' ;
	loc_utmp = 0L ;
  }

/*	"endutent" closes the utmp file.				*/

endutent()
  {
	extern int fd ;
	extern long loc_utmp ;
	extern struct utmp ubuf ;
	register char *ptr ;
	register int i ;

	if (fd != FAILURE) close(fd) ;
	fd = FAILURE ;
	loc_utmp = 0 ;
	for (i=0,ptr= (char *)(&ubuf); i < sizeof(ubuf) ;i++) *ptr++ = '\0' ;
  }

/*	"utmpname" allows the user to read a file other than the	*/
/*	normal "utmp" file.						*/

utmpname(newfile)

char *newfile ;

  {
	extern char utmpfile[] ;

/*	Determine if the new filename will fit.  If not, return FALSE.	*/

	if (strlen(newfile) > MAXFILE) return (FALSE) ;

/*	Otherwise copy in the new file name.				*/

	else strcpy(&utmpfile[0],newfile) ;

/*	Make sure everything is reset to the beginning state.		*/

	endutent() ;

	return(TRUE) ;
  }
#ifdef	ERRDEBUG
#include	<stdio.h>

gdebug(format,arg1,arg2,arg3,arg4,arg5,arg6)

char *format ;
int arg1,arg2,arg3,arg4,arg5,arg6 ;

  {
	register FILE *fp ;
	register int errnum ;
	extern int errno ;

	if ((fp = fopen("/etc/dbg.getut","a+")) == NULL) return ;

	fprintf(fp,format,arg1,arg2,arg3,arg4,arg5,arg6) ;
	fclose(fp) ;
  }
#endif