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
  17 not, 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 returned name fit
  47                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           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_data data = { -1 };
  90   struct utmp copy = *ut;
  91
  92   /* Fill in those fields we supply.  */
  93 #if _HAVE_UT_TYPE - 0
  94   copy.ut_type = USER_PROCESS;
  95 #endif
  96   copy.ut_pid = getpid ();
  97
  98   /* Seek tty.  */
  99   found_tty = tty_name (STDIN_FILENO, &tty, sizeof (_tty));
 100   if (found_tty < 0)
 101     found_tty = tty_name (STDOUT_FILENO, &tty, sizeof (_tty));
 102   if (found_tty < 0)
 103     found_tty = tty_name (STDERR_FILENO, &tty, sizeof (_tty));
 104
 105   if (found_tty >= 0)
 106     {
 107       /* We only want to insert the name of the tty without path.  */
 108       ttyp = basename (tty);
 109
 110       /* Position to record for this tty.  */
 111       strncpy (copy.ut_line, ttyp, UT_LINESIZE);
 112
 113       /* Tell that we want to use the UTMP file.  */
 114       if (utmpname (_PATH_UTMP) != 0)
 115         {
 116           struct utmp *old;
 117
 118           /* Open UTMP file.  */
 119           setutent_r (&data);
 120
 121           /* Read the record.  */
 122           if (getutline_r (&copy, &old, &data) >= 0)
 123             {
 124 #if _HAVE_UT_TYPE - 0
 125               /* We have to fake the old entry because this `login'
 126                  function does not fit well into the UTMP file
 127                  handling scheme.  */
 128               old->ut_type = copy.ut_type;
 129 #endif
 130               pututline_r (&copy, &data);
 131             }
 132           else if (errno == ESRCH)
 133             /* We didn't find anything.  pututline_r will add UT at the end
 134                of the file in this case.  */
 135             pututline_r (&copy, &data);
 136
 137           /* Close UTMP file.  */
 138           endutent_r (&data);
 139         }
 140
 141       if (tty != _tty)
 142         free (tty);             /* Free buffer malloced by tty_name.  */
 143     }
 144
 145   /* Update the WTMP file.  Here we have to add a new entry.  */
 146   if (utmpname (_PATH_WTMP) != 0)
 147     {
 148       /* Open the WTMP file.  */
 149       setutent_r (&data);
 150
 151       /* Position at end of file.  */
 152       data.loc_utmp = lseek (data.ut_fd, 0, SEEK_END);
 153       if (data.loc_utmp != -1)
 154         {
 155 #if _HAVE_UT_TYPE - 0
 156           /* We have to fake the old entry because this `login'
 157              function does not fit well into the UTMP file handling
 158              scheme.  */
 159           data.ubuf.ut_type = copy.ut_type;
 160 #endif
 161           pututline_r (&copy, &data);
 162         }
 163
 164       /* Close WTMP file.  */
 165       endutent_r (&data);
 166     }
 167 }