remove support for running post lock command

This command was used for example to suspend-to-ram (man page example).

On Linux running this command inherits OOM killer immunity. This could be
abused by an other local user on the same machine (abusing resources).

To keep the use-case for suspend-to-ram an user could write a wrapper script
for it, outside the scope of slock.

Simplify argument handling, because the post-lock command parameter is removed.

Reported by: Acts1631 <acts1631kjv@proton.me>

LICENSE

@@ -1,10 +1,10 @@
 MIT/X Consortium License
 
+© 2016-2026 Hiltjo Posthuma <hiltjo@codemadness.org>
 © 2015-2016 Markus Teich <markus.teich@stusta.mhn.de>
 © 2014 Dimitris Papastamos <sin@2f30.org>
 © 2006-2014 Anselm R Garbe <anselm@garbe.us>
 © 2014-2016 Laslo Hunhold <dev@frign.de>
-© 2016-2023 Hiltjo Posthuma <hiltjo@codemadness.org>
 
 Permission is hereby granted, free of charge, to any person obtaining a
 copy of this software and associated documentation files (the "Software"),

Makefile

@@ -11,7 +11,7 @@ all: slock
 .c.o:
 	${CC} -c ${CFLAGS} $<
 
-${OBJ}: config.h config.mk arg.h util.h
+${OBJ}: config.h config.mk util.h
 
 config.h:
 	cp config.def.h $@
@@ -25,7 +25,7 @@ clean:
 dist: clean
 	mkdir -p slock-${VERSION}
 	cp -R LICENSE Makefile README slock.1 config.mk \
-		${SRC} config.def.h arg.h util.h slock-${VERSION}
+		${SRC} config.def.h util.h slock-${VERSION}
 	tar -cf slock-${VERSION}.tar slock-${VERSION}
 	gzip slock-${VERSION}.tar
 	rm -rf slock-${VERSION}

arg.h

@@ -1,65 +0,0 @@
-/*
- * Copy me if you can.
- * by 20h
- */
-
-#ifndef ARG_H__
-#define ARG_H__
-
-extern char *argv0;
-
-/* use main(int argc, char *argv[]) */
-#define ARGBEGIN	for (argv0 = *argv, argv++, argc--;\
-					argv[0] && argv[0][0] == '-'\
-					&& argv[0][1];\
-					argc--, argv++) {\
-				char argc_;\
-				char **argv_;\
-				int brk_;\
-				if (argv[0][1] == '-' && argv[0][2] == '\0') {\
-					argv++;\
-					argc--;\
-					break;\
-				}\
-				for (brk_ = 0, argv[0]++, argv_ = argv;\
-						argv[0][0] && !brk_;\
-						argv[0]++) {\
-					if (argv_ != argv)\
-						break;\
-					argc_ = argv[0][0];\
-					switch (argc_)
-
-/* Handles obsolete -NUM syntax */
-#define ARGNUM				case '0':\
-					case '1':\
-					case '2':\
-					case '3':\
-					case '4':\
-					case '5':\
-					case '6':\
-					case '7':\
-					case '8':\
-					case '9'
-
-#define ARGEND			}\
-			}
-
-#define ARGC()		argc_
-
-#define ARGNUMF()	(brk_ = 1, estrtonum(argv[0], 0, INT_MAX))
-
-#define EARGF(x)	((argv[0][1] == '\0' && argv[1] == NULL)?\
-				((x), abort(), (char *)0) :\
-				(brk_ = 1, (argv[0][1] != '\0')?\
-					(&argv[0][1]) :\
-					(argc--, argv++, argv[0])))
-
-#define ARGF()		((argv[0][1] == '\0' && argv[1] == NULL)?\
-				(char *)0 :\
-				(brk_ = 1, (argv[0][1] != '\0')?\
-					(&argv[0][1]) :\
-					(argc--, argv++, argv[0])))
-
-#define LNGARG()	&argv[0][0]
-
-#endif

config.mk

@@ -1,5 +1,5 @@
 # slock version
-VERSION = 1.6
+VERSION = 1.7
 
 # Customize below to fit your system
 

slock.1

@@ -1,4 +1,4 @@
-.Dd October 6, 2023
+.Dd September 5, 2026
 .Dt SLOCK 1
 .Os
 .Sh NAME
@@ -7,14 +7,9 @@
 .Sh SYNOPSIS
 .Nm
 .Op Fl v
-.Op Ar cmd Op Ar arg ...
 .Sh DESCRIPTION
 .Nm
 is a simple X screen locker.
-If provided,
-.Ar cmd
-is executed after the screen has been locked.
-.Pp
 The options are as follows:
 .Bl -tag -width Ds
 .It Fl v
@@ -22,10 +17,6 @@ Print version information to stdout and exit.
 .El
 .Sh EXIT STATUS
 .Ex -std
-.Sh EXAMPLES
-$
-.Nm
-/usr/sbin/s2ram
 .Sh SECURITY CONSIDERATIONS
 To make sure a locked screen can not be bypassed by switching VTs
 or killing the X server with Ctrl+Alt+Backspace, it is recommended

slock.c

@@ -13,14 +13,12 @@
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
-#include <spawn.h>
 #include <sys/types.h>
 #include <X11/extensions/Xrandr.h>
 #include <X11/keysym.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 
-#include "arg.h"
 #include "util.h"
 
 char *argv0;
@@ -181,10 +179,13 @@ readpw(Display *dpy, struct xrandr *rr, struct lock **locks, int nscreens,
 					passwd[--len] = '\0';
 				break;
 			default:
-				if (num && !iscntrl((int)buf[0]) &&
+				if (num && !iscntrl((unsigned char)buf[0]) &&
 				    (len + num < sizeof(passwd))) {
 					memcpy(passwd + len, buf, num);
 					len += num;
+				} else if (buf[0] == '\025') { /* ctrl-u clears input */
+					explicit_bzero(&passwd, sizeof(passwd));
+					len = 0;
 				}
 				break;
 			}
@@ -301,7 +302,7 @@ lockscreen(Display *dpy, struct xrandr *rr, int screen)
 static void
 usage(void)
 {
-	die("usage: slock [-v] [cmd [arg ...]]\n");
+	die("usage: slock [-v]\n");
 }
 
 int
@@ -316,13 +317,12 @@ main(int argc, char **argv) {
 	Display *dpy;
 	int s, nlocks, nscreens;
 
-	ARGBEGIN {
-	case 'v':
+	if (argc > 1 && !strcmp(argv[1], "-v")) {
 		puts("slock-"VERSION);
 		return 0;
-	default:
+	} else if (argc > 1) {
 		usage();
-	} ARGEND
+	}
 
 	/* validate drop-user and -group */
 	errno = 0;
@@ -375,17 +375,6 @@ main(int argc, char **argv) {
 	if (nlocks != nscreens)
 		return 1;
 
-	/* run post-lock command */
-	if (argc > 0) {
-		pid_t pid;
-		extern char **environ;
-		int err = posix_spawnp(&pid, argv[0], NULL, NULL, argv, environ);
-		if (err) {
-			die("slock: failed to execute post-lock command: %s: %s\n",
-			    argv[0], strerror(err));
-		}
-	}
-
 	/* everything is now blank. Wait for the correct password */
 	readpw(dpy, &rr, locks, nscreens, hash);