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authorDale Mellor <dale@rdmp.org>2015-10-22 06:59:21 +0100
committerDale Mellor <dale@rdmp.org>2015-10-22 06:59:21 +0100
commitc0a6eb14c257a47e9573631e5ac09e6528fba377 (patch)
treea36115815cf89f6bdfd745fb8c7ddd3ae252334c /mcron.c.template
parent024027ae2dcc425f7a3bf5bf3ff3671833b02ce6 (diff)
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Taken on board suggestions of Mathieu Lirzin as per e-mails to the bug-mcron@gnu.org mailing list around September 2015.
Diffstat (limited to 'mcron.c.template')
-rw-r--r--mcron.c.template120
1 files changed, 0 insertions, 120 deletions
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-/* -*-c-*- */
-/*
- * Copyright (C) 2003, 2014 Dale Mellor
- *
- * This file is part of GNU mcron.
- *
- * GNU mcron is free software: you can redistribute it and/or modify it under
- * the terms of the GNU General Public License as published by the Free
- * Software Foundation, either version 3 of the License, or (at your option)
- * any later version.
- *
- * GNU mcron is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
- * more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with GNU mcron. If not, see <http://www.gnu.org/licenses/>.
- */
-
-
-/*
- This C code represents the thinnest possible wrapper around the Guile code
- which constitutes all the functionality of the mcron program. There are two
- plus one reasons why we need to do this, and one very unfortunate
- consequence.
-
- Firstly, SUID does not work on an executable script. In the end, it is
- the execution of the translator, in our case guile, which determines the
- effective user, and it is not wise to make the system guile installation
- SUID root!
-
- Secondly, executable scripts show up in ugly ways in listings of the
- system process table. Guile in particular, with its multi-line
- #! ...\ \n -s ...!#
- idiosyncracies shows up in process listings in a way that is difficult
- to determine what program is actually running.
-
- A third reason for the C wrapper which might be mentioned is that a
- security-conscious system administrator can choose to only install a
- binary, thus removing the possibility of a user studying a guile script
- and working out ways of hacking it to his own ends, or worse still
- finding a way to modify it to his own ends.
-
- Unfortunately, running the guile script from inside a C program means
- that the sigaction function does not work. Instead, it is necessary to
- perform the signal processing in C.
-
- The guile code itself is substituted for the GU1LE_PROGRAM_GOES_HERE (sic)
- token by the makefile, which processes the scheme to make it look like one
- big string.
-*/
-
-
-
-#include <string.h>
-#include <signal.h>
-#include <libguile.h>
-
-
-
-/* This is a function designed to be installed as a signal handler, for signals
- which are supposed to initiate shutdown of this program. It calls the scheme
- procedure (see mcron.scm for details) to do all the work, and then exits. */
-
-void
-react_to_terminal_signal (int sig)
-{
- scm_c_eval_string ("(delete-run-file)");
- exit (1);
-}
-
-
-
-/* This is a function designed to be callable from scheme, and sets up all the
- signal handlers required by the cron personality. */
-
-SCM
-set_cron_signals ()
-{
- static struct sigaction sa;
- memset (&sa, 0, sizeof (sa));
- sa.sa_handler = react_to_terminal_signal;
- sigaction (SIGTERM, &sa, 0);
- sigaction (SIGINT, &sa, 0);
- sigaction (SIGQUIT, &sa, 0);
- sigaction (SIGHUP, &sa, 0);
-
- return SCM_BOOL_T;
-}
-
-
-
-/* The effective main function (i.e. the one that actually does some work). We
- register the function above with the guile system, and then execute the mcron
- guile program. */
-
-void
-inner_main ()
-{
- scm_c_define_gsubr ("c-set-cron-signals", 0, 0, 0, set_cron_signals);
-
- scm_c_eval_string (
- GUILE_PROGRAM_GOES_HERE
- );
-}
-
-
-
-/* The real main function. Does nothing but start up the guile subsystem. */
-
-int
-main (int argc, char **argv)
-{
- setenv ("GUILE_LOAD_PATH", GUILE_LOAD_PATH, 1);
-
- scm_boot_guile (argc, argv, inner_main, 0);
-
- return 0;
-}