signals.c

/*
 * This file is part of John the Ripper password cracker,
 * Copyright (c) 1996-2003,2006,2010,2013,2015 by Solar Designer
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted.
 *
 * There's ABSOLUTELY NO WARRANTY, express or implied.
 */

#define _XOPEN_SOURCE 500 /* for setitimer(2) and siginterrupt(3) */

#define NEED_OS_TIMER
#define NEED_OS_FORK
#include "os.h"

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <sys/time.h>
#include <errno.h>

#ifdef __DJGPP__
#include <dos.h>
#endif

#ifdef __CYGWIN__
#include <windows.h>
#endif

#include "arch.h"
#include "misc.h"
#include "params.h"
#include "tty.h"
#include "options.h"
#include "config.h"
#include "bench.h"
#include "john.h"

volatile int event_pending = 0;
volatile int event_abort = 0, event_save = 0, event_status = 0;
volatile int event_ticksafety = 0;

static int timer_save_interval, timer_save_value;
static clock_t timer_ticksafety_interval, timer_ticksafety_value;

#if !OS_TIMER

#include <time.h>
#include <sys/times.h>

static clock_t timer_emu_interval = 0;
static unsigned int timer_emu_count = 0, timer_emu_max = 0;

void sig_timer_emu_init(clock_t interval)
{
	timer_emu_interval = interval;
	timer_emu_count = 0; timer_emu_max = 0;
}

void sig_timer_emu_tick(void)
{
	static clock_t last = 0;
	clock_t current;
	struct tms buf;

	if (++timer_emu_count < timer_emu_max) return;

	current = times(&buf);

	if (!last) {
		last = current;
		return;
	}

	if (current - last < timer_emu_interval && current >= last) {
		timer_emu_max += timer_emu_max + 1;
		return;
	}

	last = current;
	timer_emu_count = 0;
	timer_emu_max >>= 1;

	raise(SIGALRM);
}

#endif

#if OS_FORK
static void signal_children(int signum)
{
	int i;
	for (i = 0; i < john_child_count; i++)
		if (john_child_pids[i])
			kill(john_child_pids[i], signum);
}
#endif

static void sig_install_update(void);

static void sig_handle_update(int signum)
{
	event_save = event_pending = 1;

#ifndef SA_RESTART
	sig_install_update();
#endif
}

static void sig_install_update(void)
{
#ifdef SA_RESTART
	struct sigaction sa;

	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = sig_handle_update;
	sa.sa_flags = SA_RESTART;
	sigaction(SIGHUP, &sa, NULL);
#else
	signal(SIGHUP, sig_handle_update);
#endif
}

static void sig_remove_update(void)
{
	signal(SIGHUP, SIG_IGN);
}

void check_abort(int be_async_signal_safe)
{
	if (!event_abort) return;

	tty_done();

	if (be_async_signal_safe) {
		if (john_main_process)
			write_loop(2, "Session aborted\n", 16);
		_exit(1);
	}

	if (john_main_process)
		fprintf(stderr, "Session aborted\n");
	error();
}

static void sig_install_abort(void);

static void sig_handle_abort(int signum)
{
	int saved_errno = errno;

#if OS_FORK
	if (john_main_process) {
/*
 * We assume that our children are running on the same tty with us, so if we
 * receive a SIGINT they probably do as well without us needing to forward the
 * signal to them.  If we forwarded the signal anyway, this could result in
 * them receiving the signal twice for a single Ctrl-C keypress and proceeding
 * with immediate abort without updating the files, which is behavior that we
 * reserve for (presumably intentional) repeated Ctrl-C keypress.
 *
 * We forward the signal as SIGINT even though ours was different (typically a
 * SIGTERM) in order not to trigger a repeated same signal for children if the
 * user does e.g. "killall john", which would send SIGTERM directly to children
 * and also have us forward a signal.
 */
		if (signum != SIGINT)
			signal_children(SIGINT);
	} else {
		static int prev_signum;
/*
 * If it's not the same signal twice in a row, don't proceed with immediate
 * abort since these two signals could have been triggered by the same killall
 * (perhaps a SIGTERM from killall directly and a SIGINT as forwarded by our
 * parent).  event_abort would be set back to 1 just below the check_abort()
 * call.  We only reset it to 0 temporarily to skip the immediate abort here.
 */
		if (prev_signum && signum != prev_signum)
			event_abort = 0;
		prev_signum = signum;
	}
#endif

	check_abort(1);

	event_abort = event_pending = 1;

	write_loop(2, "Wait...\r", 8);

	sig_install_abort();

	errno = saved_errno;
}

#ifdef __CYGWIN__
static CALLBACK BOOL sig_handle_abort_ctrl(DWORD ctrltype)
{
	sig_handle_abort(SIGINT);
	return TRUE;
}
#endif

static void sig_install_abort(void)
{
#ifdef __DJGPP__
	setcbrk(1);
#endif

#ifdef __CYGWIN__
/*
 * "If the HandlerRoutine parameter is NULL, [...] a FALSE value restores
 * normal processing of CTRL+C input.  This attribute of ignoring or processing
 * CTRL+C is inherited by child processes."  So restore normal processing here
 * in case our parent (such as Johnny the GUI) had disabled it.
 */
	SetConsoleCtrlHandler(NULL, FALSE);
	SetConsoleCtrlHandler(sig_handle_abort_ctrl, TRUE);
#endif

	signal(SIGINT, sig_handle_abort);
	signal(SIGTERM, sig_handle_abort);
#ifdef SIGXCPU
	signal(SIGXCPU, sig_handle_abort);
#endif
#ifdef SIGXFSZ
	signal(SIGXFSZ, sig_handle_abort);
#endif
}

static void sig_remove_abort(void)
{
#ifdef __CYGWIN__
	SetConsoleCtrlHandler(sig_handle_abort_ctrl, FALSE);
#endif

	signal(SIGINT, SIG_DFL);
	signal(SIGTERM, SIG_DFL);
#ifdef SIGXCPU
	signal(SIGXCPU, SIG_DFL);
#endif
#ifdef SIGXFSZ
	signal(SIGXFSZ, SIG_DFL);
#endif
}

static void sig_install_timer(void);

static void sig_handle_timer(int signum)
{
	int saved_errno = errno;

	if (!--timer_save_value) {
		timer_save_value = timer_save_interval;

		event_save = event_pending = 1;
	}

	if (!--timer_ticksafety_value) {
		timer_ticksafety_value = timer_ticksafety_interval;

		event_ticksafety = event_pending = 1;
	}

	if (john_main_process) {
		int c;
#if OS_FORK
		int new_abort = 0, new_status = 0;
#endif
		while ((c = tty_getchar()) >= 0) {
			if (c == 3 || c == 'q') {
#if OS_FORK
				new_abort = 1;
#endif
				sig_handle_abort(0);
			} else {
#if OS_FORK
				new_status = 1;
#endif
				event_status = event_pending = 1;
			}
		}

#if OS_FORK
		if (new_abort || new_status)
			signal_children(new_abort ? SIGTERM : SIGUSR2);
#endif
	}

#if !OS_TIMER
	signal(SIGALRM, sig_handle_timer);
#elif !defined(SA_RESTART) && !defined(__DJGPP__)
	sig_install_timer();
#endif

	errno = saved_errno;
}

#if OS_TIMER
static void sig_init_timer(void)
{
	struct itimerval it;

	it.it_value.tv_sec = TIMER_INTERVAL;
	it.it_value.tv_usec = 0;
#if defined(SA_RESTART) || defined(__DJGPP__)
	it.it_interval = it.it_value;
#else
	memset(&it.it_interval, 0, sizeof(it.it_interval));
#endif
	if (setitimer(ITIMER_REAL, &it, NULL))
		pexit("setitimer");
}
#endif

static void sig_install_timer(void)
{
#if !OS_TIMER
	signal(SIGALRM, sig_handle_timer);
	sig_timer_emu_init(TIMER_INTERVAL * clk_tck);
#else
	struct sigaction sa;

	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = sig_handle_timer;
#ifdef SA_RESTART
	sa.sa_flags = SA_RESTART;
#endif
	sigaction(SIGALRM, &sa, NULL);
#if !defined(SA_RESTART) && !defined(__DJGPP__)
	siginterrupt(SIGALRM, 0);
#endif

	sig_init_timer();
#endif
}

static void sig_remove_timer(void)
{
#if OS_TIMER
	struct itimerval it;

	memset(&it, 0, sizeof(it));
	if (setitimer(ITIMER_REAL, &it, NULL)) perror("setitimer");
#endif

	signal(SIGALRM, SIG_DFL);
}

#if OS_FORK
static void sig_handle_status(int signum)
{
	event_status = event_pending = 1;
	signal(SIGUSR2, sig_handle_status);
}
#endif

static void sig_done(void);

void sig_init(void)
{
	clk_tck_init();

	timer_save_interval = cfg_get_int(SECTION_OPTIONS, NULL, "Save");
	if (timer_save_interval < 0)
		timer_save_interval = TIMER_SAVE_DELAY;
	else
	if ((timer_save_interval /= TIMER_INTERVAL) <= 0)
		timer_save_interval = 1;
	timer_save_value = timer_save_interval;

	timer_ticksafety_interval = (clock_t)1 << (sizeof(clock_t) * 8 - 4);
	timer_ticksafety_interval /= clk_tck;
	if ((timer_ticksafety_interval /= TIMER_INTERVAL) <= 0)
		timer_ticksafety_interval = 1;
	timer_ticksafety_value = timer_ticksafety_interval;

	atexit(sig_done);

	sig_install_update();
	sig_install_abort();
	sig_install_timer();
#if OS_FORK
	signal(SIGUSR2, sig_handle_status);
#endif
}

void sig_init_child(void)
{
#if OS_TIMER
	sig_init_timer();
#endif
}

static void sig_done(void)
{
	sig_remove_update();
	sig_remove_abort();
	sig_remove_timer();
}