6cd941e061
* mcron.c (main, react_to_terminal_signal): Use EXIT_SUCCESS and EXIT_FAILURE macros instead of magic numbers.
106 lines
3.6 KiB
C
106 lines
3.6 KiB
C
/* mcron - run jobs at scheduled times
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Copyright (C) 2015, 2016 Mathieu Lirzin
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Copyright (C) 2003, 2014 Dale Mellor
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This file is part of GNU Mcron.
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GNU Mcron is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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GNU Mcron 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Mcron. If not, see <http://www.gnu.org/licenses/>. */
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/* This C code represents the thinnest possible wrapper around the Guile code
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which constitutes all the functionality of the mcron program. There are
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two plus one reasons why we need to do this, and one very unfortunate
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consequence.
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* Firstly, SUID does not work on an executable script. In the end, it is
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the execution of the translator, in our case guile, which determines the
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effective user, and it is not wise to make the system guile installation
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SUID root!
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* Secondly, executable scripts show up in ugly ways in listings of the
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system process table. Guile in particular, with its multi-line
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#! ...\ \n -s ...!#
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idiosyncracies shows up in process listings in a way that is difficult
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to determine what program is actually running.
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* A third reason for the C wrapper which might be mentioned is that a
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security-conscious system administrator can choose to only install a
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binary, thus removing the possibility of a user studying a guile script
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and working out ways of hacking it to his own ends, or worse still
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finding a way to modify it to his own ends.
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* Unfortunately, running the guile script from inside a C program means
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that the sigaction function does not work. Instead, it is necessary to
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perform the signal processing in C. */
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#include <libguile.h>
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#include <signal.h>
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#include <stdlib.h>
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#include <string.h>
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/* Forward declarations. */
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void inner_main (void *closure, int argc, char **argv);
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void react_to_terminal_signal (int sig);
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SCM set_cron_signals (void);
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int
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main (int argc, char **argv)
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{
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setenv ("GUILE_LOAD_PATH", GUILE_LOAD_PATH, 1);
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scm_boot_guile (argc, argv, inner_main, 0);
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return EXIT_SUCCESS;
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}
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/* The effective main function (i.e. the one that actually does some work).
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We register the function above with the guile system, and then execute the
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mcron guile program. */
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void
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inner_main (void *closure, int argc, char **argv)
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{
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scm_set_current_module (scm_c_resolve_module ("mcron main"));
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scm_c_define_gsubr ("c-set-cron-signals", 0, 0, 0, set_cron_signals);
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scm_c_eval_string ("(main)");
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}
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/* This is a function designed to be callable from scheme, and sets up all the
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signal handlers required by the cron personality. */
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SCM
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set_cron_signals ()
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{
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static struct sigaction sa;
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memset (&sa, 0, sizeof (sa));
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sa.sa_handler = react_to_terminal_signal;
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sigaction (SIGTERM, &sa, 0);
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sigaction (SIGINT, &sa, 0);
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sigaction (SIGQUIT, &sa, 0);
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sigaction (SIGHUP, &sa, 0);
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return SCM_BOOL_T;
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}
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/* This is a function designed to be installed as a signal handler, for
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signals which are supposed to initiate shutdown of this program. It calls
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the scheme procedure (see mcron.scm for details) to do all the work, and
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then exits. */
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void
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react_to_terminal_signal (int sig)
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{
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scm_c_eval_string ("(delete-run-file)");
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exit (EXIT_FAILURE);
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}
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