diff options
| -rw-r--r-- | mcron.c | 47 |
1 files changed, 10 insertions, 37 deletions
@@ -18,31 +18,9 @@ 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. */ +/* This C code represents a thin wrapper around the Guile code of Mcron. It + is needed because the crontab personality requires SUID which is not + permitted for executable scripts. */ #include <libguile.h> #include <signal.h> @@ -63,21 +41,19 @@ main (int argc, char **argv) return EXIT_SUCCESS; } -/* 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. */ - +/* Launch the Mcron Guile main program. */ void inner_main (void *closure, int argc, char **argv) { scm_set_current_module (scm_c_resolve_module ("mcron main")); + /* Register set_cron_signals to be called from Guile. */ scm_c_define_gsubr ("c-set-cron-signals", 0, 0, 0, set_cron_signals); scm_c_eval_string ("(main)"); } -/* This is a function designed to be callable from scheme, and sets up all the - signal handlers required by the cron personality. */ - +/* Set up all the signal handlers as required by the cron personality. This + is necessary to perform the signal processing in C because the sigaction + function won't work when called from Guile. */ SCM set_cron_signals () { @@ -93,11 +69,8 @@ set_cron_signals () return SCM_BOOL_T; } -/* 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. */ - +/* Handle signal SIG and exit. All signals that mcron handles will produce + the same behavior so we don't need to use SIG in the implementation. */ void react_to_terminal_signal (int sig) { |