login/login.c

   1 /* Copyright (C) 1996 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <limits.h>
  22 #include <string.h>
  23 #include <unistd.h>
  24 #include <stdlib.h>
  25 #include <utmp.h>
  26 \f
  27 /* Return the result of ttyname in the buffer pointed to by TTY, which should
  28    be of length BUF_LEN.  If it is too long to fit in this buffer, a
  29    sufficiently long buffer is allocated using malloc, and returned in TTY.
  30    0 is returned upon success, -1 otherwise.  */
  31 static int
  32 tty_name (int fd, char **tty, size_t buf_len)
  33 {
  34   int rv;                       /* Return value.  0 = success.  */
  35   char *buf = *tty;             /* Buffer for ttyname, initially the user's. */
  36
  37   for (;;)
  38     {
  39       char *new_buf;
  40
  41       if (buf_len)
  42         {
  43           rv = ttyname_r (fd, buf, buf_len);
  44
  45           if (rv < 0 || memchr (buf, '\0', buf_len))
  46             /* We either got an error, or we succeeded and the
  47                returned name fit in the buffer.  */
  48             break;
  49
  50           /* Try again with a longer buffer.  */
  51           buf_len += buf_len;   /* Double it */
  52         }
  53       else
  54         /* No initial buffer; start out by mallocing one.  */
  55         buf_len = 128;          /* First time guess.  */
  56
  57       if (buf != *tty)
  58         /* We've already malloced another buffer at least once.  */
  59         new_buf = realloc (buf, buf_len);
  60       else
  61         new_buf = malloc (buf_len);
  62       if (! new_buf)
  63         {
  64           rv = -1;
  65           __set_errno (ENOMEM);
  66           break;
  67         }
  68     }
  69
  70   if (rv == 0)
  71     *tty = buf;         /* Return buffer to the user.  */
  72   else if (buf != *tty)
  73     free (buf);         /* Free what we malloced when returning an error.  */
  74
  75   return rv;
  76 }
  77 \f
  78 void
  79 login (const struct utmp *ut)
  80 {
  81 #ifdef PATH_MAX
  82   char _tty[PATH_MAX + UT_LINESIZE];
  83 #else
  84   char _tty[512 + UT_LINESIZE];
  85 #endif
  86   char *tty = _tty;
  87   int found_tty;
  88   const char *ttyp;
  89   struct utmp copy = *ut;
  90   struct utmp utbuf;
  91
  92   /* Fill in those fields we supply.  */
  93 #if _HAVE_UT_TYPE - 0
  94   copy.ut_type = USER_PROCESS;
  95 #endif
  96 #if _HAVE_UT_PID - 0
  97   copy.ut_pid = getpid ();
  98 #endif
  99
 100   /* Seek tty.  */
 101   found_tty = tty_name (STDIN_FILENO, &tty, sizeof (_tty));
 102   if (found_tty < 0)
 103     found_tty = tty_name (STDOUT_FILENO, &tty, sizeof (_tty));
 104   if (found_tty < 0)
 105     found_tty = tty_name (STDERR_FILENO, &tty, sizeof (_tty));
 106
 107   if (found_tty >= 0)
 108     {
 109       /* We only want to insert the name of the tty without path.  */
 110       ttyp = basename (tty);
 111
 112       /* Position to record for this tty.  */
 113       strncpy (copy.ut_line, ttyp, UT_LINESIZE);
 114
 115       /* Tell that we want to use the UTMP file.  */
 116       if (utmpname (_PATH_UTMP) != 0)
 117         {
 118           struct utmp *old;
 119
 120           /* Open UTMP file.  */
 121           setutent ();
 122
 123           /* Read the record.  */
 124           getutline_r (&copy, &utbuf, &old);
 125
 126           /* Write the entry.  */
 127           pututline (&copy);
 128
 129           /* Close UTMP file.  */
 130           endutent ();
 131         }
 132
 133       if (tty != _tty)
 134         free (tty);             /* Free buffer malloced by tty_name.  */
 135     }
 136
 137   /* Update the WTMP file.  Here we have to add a new entry.  */
 138   if (utmpname (_PATH_WTMP) != 0)
 139     {
 140       struct utmp *up;
 141
 142       /* Open the WTMP file.  */
 143       setutent ();
 144
 145       /* Position at end of file.  */
 146       while (! getutent_r (&utbuf, &up));
 147
 148       /* Write the new entry.  */
 149       pututline (&copy);
 150
 151       /* Close WTMP file.  */
 152       endutent ();
 153     }
 154 }