Fix issue #97 with very basic signal handling

main.c

@@ -107,6 +107,8 @@ int main(int argc, char **argv) {
 	int try = 0, root_user = 1;
 	uid_t owner;
 	userinfo_t *u = &user;
+	int sigusr1recieved = 0;
+	sigset_t sigusr1;
 
 	oldvt = oldsysrq = oldprintk = vt.nr = vt.fd = -1;
 	vt.ios = NULL;
@@ -121,9 +123,14 @@ int main(int argc, char **argv) {
 	setup_signal(SIGQUIT, sa_handler_exit);
 	setup_signal(SIGHUP, SIG_IGN);
 	setup_signal(SIGINT, SIG_IGN);
-	setup_signal(SIGUSR1, SIG_IGN);
+	if (options->staggered != 1) {
+		setup_signal(SIGUSR1, SIG_IGN);
+	}
 	setup_signal(SIGUSR2, SIG_IGN);
 
+	sigemptyset(&sigusr1);
+	sigaddset(&sigusr1, SIGUSR1);
+
 	vt_init();
 	vt_get_current(&oldvt, &owner);
 
@@ -186,6 +193,13 @@ int main(int argc, char **argv) {
 
 	locked = 1;
 
+	if (options->staggered == 1) {
+		sigprocmask(SIG_BLOCK,&sigusr1,NULL);
+		sigwait(&sigusr1, &sigusr1recieved);
+		sigprocmask(SIG_UNBLOCK,&sigusr1,NULL);
+		fflush(vt.ios);
+	}
+
 	while (locked) {
 		if (!root_user && try >= (u == &root ? 1 : 3)) {
 			u = u == &root ? &user : &root;

options.c

@@ -28,7 +28,7 @@ static options_t _options;
 const options_t *options = (const options_t*) &_options;
 
 void print_usage() {
-	printf("usage: physlock [-dhLlmsv] [-p MSG]\n");
+	printf("usage: physlock [-dhLlmsvw] [-p MSG]\n");
 }
 
 void print_version() {
@@ -45,8 +45,9 @@ void parse_options(int argc, char **argv) {
 	_options.disable_sysrq = 0;
 	_options.lock_switch = -1;
 	_options.mute_kernel_messages = 0;
+	_options.staggered = 0;
 
-	while ((opt = getopt(argc, argv, "dhLlmp:sv")) != -1) {
+	while ((opt = getopt(argc, argv, "dhLlmp:svw")) != -1) {
 		switch (opt) {
 			case '?':
 				print_usage();
@@ -75,6 +76,9 @@ void parse_options(int argc, char **argv) {
 			case 'v':
 				print_version();
 				exit(0);
+			case 'w':
+				_options.staggered = 1;
+				break;
 		}
 	}
 }

physlock.1

@@ -49,6 +49,14 @@ Disable SysRq mechanism while physlock is running.
 .TP
 .B \-v
 Print version information to standard output and exit.
+.TP
+.B \-w
+Wait until a SIGUSR1 signal is received to prompt for authentication.
+Useful if the first authentication attempt always fails
+due to bad input buffering in the virtual terminal.
+.BI WARNING:
+When using this option, ensure that some external program sends a SIGUSR1
+signal to physlock. Otherwise, you will be locked out of your session.
 .SH AUTHORS
 .TP
 Bert Muennich <ber.t at gmx.com>

physlock.h

@@ -54,6 +54,7 @@ typedef struct options_s {
 	int disable_sysrq;
 	int lock_switch;
 	int mute_kernel_messages;
+	int staggered;
 	const char *prompt;
 } options_t;