login/login.c

   1 /* Copyright (C) 1996, 1997, 1998, 2002 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 Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <assert.h>
  21 #include <errno.h>
  22 #include <limits.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <stdlib.h>
  26 #include <utmp.h>
  27
  28
  29 /* Return the result of ttyname in the buffer pointed to by TTY, which should
  30    be of length BUF_LEN.  If it is too long to fit in this buffer, a
  31    sufficiently long buffer is allocated using malloc, and returned in TTY.
  32    0 is returned upon success, -1 otherwise.  */
  33 static int
  34 tty_name (int fd, char **tty, size_t buf_len)
  35 {
  36   int rv;                       /* Return value.  0 = success.  */
  37   char *buf = *tty;             /* Buffer for ttyname, initially the user's. */
  38
  39   for (;;)
  40     {
  41       char *new_buf;
  42
  43       if (buf_len)
  44         {
  45           rv = ttyname_r (fd, buf, buf_len);
  46
  47           if (rv != 0 || memchr (buf, '\0', buf_len))
  48             /* We either got an error, or we succeeded and the
  49                returned name fit in the buffer.  */
  50             break;
  51
  52           /* Try again with a longer buffer.  */
  53           buf_len += buf_len;   /* Double it */
  54         }
  55       else
  56         /* No initial buffer; start out by mallocing one.  */
  57         buf_len = 128;          /* First time guess.  */
  58
  59       if (buf != *tty)
  60         /* We've already malloced another buffer at least once.  */
  61         new_buf = realloc (buf, buf_len);
  62       else
  63         new_buf = malloc (buf_len);
  64       if (! new_buf)
  65         {
  66           rv = -1;
  67           __set_errno (ENOMEM);
  68           break;
  69         }
  70       buf = new_buf;
  71     }
  72
  73   if (rv == 0)
  74     *tty = buf;         /* Return buffer to the user.  */
  75   else if (buf != *tty)
  76     free (buf);         /* Free what we malloced when returning an error.  */
  77
  78   return rv;
  79 }
  80 \f
  81 void
  82 login (const struct utmp *ut)
  83 {
  84 #ifdef PATH_MAX
  85   char _tty[PATH_MAX + UT_LINESIZE];
  86 #else
  87   char _tty[512 + UT_LINESIZE];
  88 #endif
  89   char *tty = _tty;
  90   int found_tty;
  91   const char *ttyp;
  92   struct utmp copy = *ut;
  93
  94   /* Fill in those fields we supply.  */
  95 #if _HAVE_UT_TYPE - 0
  96   copy.ut_type = USER_PROCESS;
  97 #endif
  98 #if _HAVE_UT_PID - 0
  99   copy.ut_pid = getpid ();
 100 #endif
 101
 102   /* Seek tty.  */
 103   found_tty = tty_name (STDIN_FILENO, &tty, sizeof (_tty));
 104   if (found_tty < 0)
 105     found_tty = tty_name (STDOUT_FILENO, &tty, sizeof (_tty));
 106   if (found_tty < 0)
 107     found_tty = tty_name (STDERR_FILENO, &tty, sizeof (_tty));
 108
 109   if (found_tty >= 0)
 110     {
 111       /* We only want to insert the name of the tty without path.
 112          But take care of name like /dev/pts/3.  */
 113       if (strncmp (tty, "/dev/", 5) == 0)
 114         ttyp = tty + 5;         /* Skip the "/dev/".  */
 115       else
 116         ttyp = basename (tty);
 117
 118       /* Position to record for this tty.  */
 119       strncpy (copy.ut_line, ttyp, UT_LINESIZE);
 120
 121       /* Tell that we want to use the UTMP file.  */
 122       if (utmpname (_PATH_UTMP) == 0)
 123         {
 124           /* Open UTMP file.  */
 125           setutent ();
 126
 127           /* Write the entry.  */
 128           pututline (&copy);
 129
 130           /* Close UTMP file.  */
 131           endutent ();
 132         }
 133
 134       if (tty != _tty)
 135         free (tty);             /* Free buffer malloced by tty_name.  */
 136     }
 137   else
 138     /* We provide a default value so that the output does not contain
 139        an random bytes in this field.  */
 140     strncpy (copy.ut_line, "???", UT_LINESIZE);
 141
 142   /* Update the WTMP file.  Here we have to add a new entry.  */
 143   updwtmp (_PATH_WTMP, &copy);
 144 }