135 lines
4.0 KiB
C
135 lines
4.0 KiB
C
/* Copyright (C) 1996 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include <alloca.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <utmp.h>
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#include <sys/file.h>
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#include <sys/stat.h>
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/* XXX An alternative solution would be to call a SUID root program
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which write the new value. */
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int
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pututline_r (const struct utmp *id, struct utmp_data *utmp_data)
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{
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struct stat st;
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int result = 0;
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#if _HAVE_UT_TYPE - 0
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/* Test whether ID has any of the legal types because we have to
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prevent illegal entries. */
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if (id->ut_type != RUN_LVL && id->ut_type != BOOT_TIME
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&& id->ut_type != OLD_TIME && id->ut_type != NEW_TIME
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&& id->ut_type != INIT_PROCESS && id->ut_type != LOGIN_PROCESS
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&& id->ut_type != USER_PROCESS && id->ut_type != DEAD_PROCESS)
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/* No, using '<' and '>' for the test is not possible. */
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{
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errno = EINVAL;
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return -1;
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}
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#endif
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/* Open utmp file if not already done. */
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if (utmp_data->ut_fd == -1)
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{
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setutent_r (utmp_data);
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if (utmp_data->ut_fd == -1)
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return -1;
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}
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#if _HAVE_UT_TYPE - 0
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/* Seek position to write. */
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if (utmp_data->loc_utmp >= sizeof (struct utmp)
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&& utmp_data->ubuf.ut_type != id->ut_type)
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{
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/* We must not overwrite the data in UTMP_DATA. */
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struct utmp_data *data_tmp = alloca (sizeof (*data_tmp));
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struct utmp *dummy;
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*data_tmp = *utmp_data;
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utmp_data = data_tmp;
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if (getutid_r (id, &dummy, utmp_data) < 0)
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{
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if (errno != ESRCH)
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/* Some error occured. If no entry was found, the position
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pointer now is at the end of the file. */
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return -1;
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/* Set position pointer to position after adding of the record. */
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utmp_data->loc_utmp += sizeof (struct utmp);
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}
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}
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#endif
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/* Try to lock the file. */
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if (flock (utmp_data->ut_fd, LOCK_EX | LOCK_NB) < 0 && errno != ENOSYS)
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{
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/* Oh, oh. The file is already locked. Wait a bit and try again. */
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sleep (1);
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/* This time we ignore the error. */
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(void) flock (utmp_data->ut_fd, LOCK_EX | LOCK_NB);
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}
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/* Find out how large the file is. */
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result = fstat (utmp_data->ut_fd, &st);
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if (result >= 0)
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/* Position file correctly. */
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if (utmp_data->loc_utmp < sizeof (struct utmp))
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/* Not located at any valid entry. Add at the end. */
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{
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result = lseek (utmp_data->ut_fd, 0L, SEEK_END);
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if (result >= 0)
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/* Where we'll be if the write succeeds. */
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utmp_data->loc_utmp = st.st_size + sizeof (struct utmp);
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}
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else if (utmp_data->loc_utmp <= st.st_size)
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result =
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lseek (utmp_data->ut_fd, utmp_data->loc_utmp - sizeof (struct utmp),
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SEEK_SET);
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if (result >= 0)
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/* Write the new data. */
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if (write (utmp_data->ut_fd, id, sizeof (struct utmp))
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!= sizeof (struct utmp))
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{
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/* If we appended a new record this is only partially written.
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Remove it. */
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if (utmp_data->loc_utmp > st.st_size)
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{
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(void) ftruncate (utmp_data->ut_fd, st.st_size);
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utmp_data->loc_utmp = st.st_size;
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}
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result = -1;
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}
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/* And unlock the file. */
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(void) flock (utmp_data->ut_fd, LOCK_UN);
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return result;
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}
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