slock

commit 6f76e0a9275e2ff3e101e9bf56627024b0174fe0
Author: Matthew Carlson <matt@mcarlson.xyz>
Date:   Fri, 16 Jul 2021 00:20:48 -0400

slock

Diffstat:
A
Makefile
 | 
39
+++++++++++++++++++++++++++++++++++++++
A
arg.h
 | 
65
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
config.h
 | 
12
++++++++++++
A
config.mk
 | 
32
++++++++++++++++++++++++++++++++
A
explicit_bzero.c
 | 
19
+++++++++++++++++++
A
slock.c
 | 
395
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
util.h
 | 
2
++

7 files changed, 564 insertions(+), 0 deletions(-)
diff --git a/Makefile b/Makefile
@@ -0,0 +1,39 @@
+# slock - simple screen locker
+# See LICENSE file for copyright and license details.
+
+include config.mk
+
+SRC = slock.c ${COMPATSRC}
+OBJ = ${SRC:.c=.o}
+
+all: options slock
+
+options:
+	@echo slock build options:
+	@echo "CFLAGS   = ${CFLAGS}"
+	@echo "LDFLAGS  = ${LDFLAGS}"
+	@echo "CC       = ${CC}"
+
+.c.o:
+	@echo CC $<
+	@${CC} -c ${CFLAGS} $<
+
+${OBJ}: config.h config.mk arg.h util.h
+
+slock: ${OBJ}
+	@echo CC -o $@
+	@${CC} -o $@ ${OBJ} ${LDFLAGS}
+
+install: all
+	@echo installing executable file to ${DESTDIR}${PREFIX}/bin
+	@mkdir -p ${DESTDIR}${PREFIX}/bin
+	@cp -f slock ${DESTDIR}${PREFIX}/bin
+	@chmod 755 ${DESTDIR}${PREFIX}/bin/slock
+	@chmod u+s ${DESTDIR}${PREFIX}/bin/slock
+	@rm -f slock *.o
+
+uninstall:
+	@echo removing executable file from ${DESTDIR}${PREFIX}/bin
+	@rm -f ${DESTDIR}${PREFIX}/bin/slock
+
+.PHONY: all options install uninstall
diff --git a/arg.h b/arg.h
@@ -0,0 +1,65 @@
+/*
+ * 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
diff --git a/config.h b/config.h
@@ -0,0 +1,12 @@
+/* user and group to drop privileges to */
+static const char *user  = "nobody";
+static const char *group = "nogroup";
+
+static const char *colorname[NUMCOLS] = {
+	[INIT] =   "black",     /* after initialization */
+	[INPUT] =  "#005577",   /* during input */
+	[FAILED] = "#CC3333",   /* wrong password */
+};
+
+/* treat a cleared input like a wrong password (color) */
+static const int failonclear = 1;
diff --git a/config.mk b/config.mk
@@ -0,0 +1,32 @@
+# slock version
+VERSION = 1.4
+
+# Customize below to fit your system
+
+# paths
+PREFIX = /usr/local
+MANPREFIX = ${PREFIX}/share/man
+
+X11INC = /usr/X11R6/include
+X11LIB = /usr/X11R6/lib
+
+# includes and libs
+INCS = -I. -I/usr/include -I${X11INC}
+LIBS = -L/usr/lib -lc -lcrypt -L${X11LIB} -lX11 -lXext -lXrandr
+
+# flags
+CPPFLAGS = -DVERSION=\"${VERSION}\" -D_DEFAULT_SOURCE -DHAVE_SHADOW_H
+CFLAGS = -std=c99 -pedantic -Wall -Os ${INCS} ${CPPFLAGS}
+LDFLAGS = -s ${LIBS}
+COMPATSRC = explicit_bzero.c
+
+# On OpenBSD and Darwin remove -lcrypt from LIBS
+#LIBS = -L/usr/lib -lc -L${X11LIB} -lX11 -lXext -lXrandr
+# On *BSD remove -DHAVE_SHADOW_H from CPPFLAGS
+# On NetBSD add -D_NETBSD_SOURCE to CPPFLAGS
+#CPPFLAGS = -DVERSION=\"${VERSION}\" -D_BSD_SOURCE -D_NETBSD_SOURCE
+# On OpenBSD set COMPATSRC to empty
+#COMPATSRC =
+
+# compiler and linker
+CC = cc
diff --git a/explicit_bzero.c b/explicit_bzero.c
@@ -0,0 +1,19 @@
+/*	$OpenBSD: explicit_bzero.c,v 1.3 2014/06/21 02:34:26 matthew Exp $ */
+/*
+ * Public domain.
+ * Written by Matthew Dempsky.
+ */
+
+#include <string.h>
+
+__attribute__((weak)) void
+__explicit_bzero_hook(void *buf, size_t len)
+{
+}
+
+void
+explicit_bzero(void *buf, size_t len)
+{
+	memset(buf, 0, len);
+	__explicit_bzero_hook(buf, len);
+}
diff --git a/slock.c b/slock.c
@@ -0,0 +1,395 @@
+/* See LICENSE file for license details. */
+#define _XOPEN_SOURCE 500
+#if HAVE_SHADOW_H
+#include <shadow.h>
+#endif
+
+#include <ctype.h>
+#include <errno.h>
+#include <grp.h>
+#include <pwd.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.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;
+
+enum {
+	INIT,
+	INPUT,
+	FAILED,
+	NUMCOLS
+};
+
+struct lock {
+	int screen;
+	Window root, win;
+	Pixmap pmap;
+	unsigned long colors[NUMCOLS];
+};
+
+struct xrandr {
+	int active;
+	int evbase;
+	int errbase;
+};
+
+#include "config.h"
+
+static void
+die(const char *errstr, ...)
+{
+	va_list ap;
+
+	va_start(ap, errstr);
+	vfprintf(stderr, errstr, ap);
+	va_end(ap);
+	exit(1);
+}
+
+#ifdef __linux__
+#include <fcntl.h>
+#include <linux/oom.h>
+
+static void
+dontkillme(void)
+{
+	FILE *f;
+	const char oomfile[] = "/proc/self/oom_score_adj";
+
+	if (!(f = fopen(oomfile, "w"))) {
+		if (errno == ENOENT)
+			return;
+		die("slock: fopen %s: %s\n", oomfile, strerror(errno));
+	}
+	fprintf(f, "%d", OOM_SCORE_ADJ_MIN);
+	if (fclose(f)) {
+		if (errno == EACCES)
+			die("slock: unable to disable OOM killer. "
+			    "Make sure to suid or sgid slock.\n");
+		else
+			die("slock: fclose %s: %s\n", oomfile, strerror(errno));
+	}
+}
+#endif
+
+static const char *
+gethash(void)
+{
+	const char *hash;
+	struct passwd *pw;
+
+	/* Check if the current user has a password entry */
+	errno = 0;
+	if (!(pw = getpwuid(getuid()))) {
+		if (errno)
+			die("slock: getpwuid: %s\n", strerror(errno));
+		else
+			die("slock: cannot retrieve password entry\n");
+	}
+	hash = pw->pw_passwd;
+
+#if HAVE_SHADOW_H
+	if (!strcmp(hash, "x")) {
+		struct spwd *sp;
+		if (!(sp = getspnam(pw->pw_name)))
+			die("slock: getspnam: cannot retrieve shadow entry. "
+			    "Make sure to suid or sgid slock.\n");
+		hash = sp->sp_pwdp;
+	}
+#else
+	if (!strcmp(hash, "*")) {
+#ifdef __OpenBSD__
+		if (!(pw = getpwuid_shadow(getuid())))
+			die("slock: getpwnam_shadow: cannot retrieve shadow entry. "
+			    "Make sure to suid or sgid slock.\n");
+		hash = pw->pw_passwd;
+#else
+		die("slock: getpwuid: cannot retrieve shadow entry. "
+		    "Make sure to suid or sgid slock.\n");
+#endif /* __OpenBSD__ */
+	}
+#endif /* HAVE_SHADOW_H */
+
+	return hash;
+}
+
+static void
+readpw(Display *dpy, struct xrandr *rr, struct lock **locks, int nscreens,
+       const char *hash)
+{
+	XRRScreenChangeNotifyEvent *rre;
+	char buf[32], passwd[256], *inputhash;
+	int num, screen, running, failure, oldc;
+	unsigned int len, color;
+	KeySym ksym;
+	XEvent ev;
+
+	len = 0;
+	running = 1;
+	failure = 0;
+	oldc = INIT;
+
+	while (running && !XNextEvent(dpy, &ev)) {
+		if (ev.type == KeyPress) {
+			explicit_bzero(&buf, sizeof(buf));
+			num = XLookupString(&ev.xkey, buf, sizeof(buf), &ksym, 0);
+			if (IsKeypadKey(ksym)) {
+				if (ksym == XK_KP_Enter)
+					ksym = XK_Return;
+				else if (ksym >= XK_KP_0 && ksym <= XK_KP_9)
+					ksym = (ksym - XK_KP_0) + XK_0;
+			}
+			if (IsFunctionKey(ksym) ||
+			    IsKeypadKey(ksym) ||
+			    IsMiscFunctionKey(ksym) ||
+			    IsPFKey(ksym) ||
+			    IsPrivateKeypadKey(ksym))
+				continue;
+			switch (ksym) {
+			case XK_Return:
+				passwd[len] = '\0';
+				errno = 0;
+				if (!(inputhash = crypt(passwd, hash)))
+					fprintf(stderr, "slock: crypt: %s\n", strerror(errno));
+				else
+					running = !!strcmp(inputhash, hash);
+				if (running) {
+					XBell(dpy, 100);
+					failure = 1;
+				}
+				explicit_bzero(&passwd, sizeof(passwd));
+				len = 0;
+				break;
+			case XK_Escape:
+				explicit_bzero(&passwd, sizeof(passwd));
+				len = 0;
+				break;
+			case XK_BackSpace:
+				if (len)
+					passwd[--len] = '\0';
+				break;
+			default:
+				if (num && !iscntrl((int)buf[0]) &&
+				    (len + num < sizeof(passwd))) {
+					memcpy(passwd + len, buf, num);
+					len += num;
+				}
+				break;
+			}
+			color = len ? INPUT : ((failure || failonclear) ? FAILED : INIT);
+			if (running && oldc != color) {
+				for (screen = 0; screen < nscreens; screen++) {
+					XSetWindowBackground(dpy,
+					                     locks[screen]->win,
+					                     locks[screen]->colors[color]);
+					XClearWindow(dpy, locks[screen]->win);
+				}
+				oldc = color;
+			}
+		} else if (rr->active && ev.type == rr->evbase + RRScreenChangeNotify) {
+			rre = (XRRScreenChangeNotifyEvent*)&ev;
+			for (screen = 0; screen < nscreens; screen++) {
+				if (locks[screen]->win == rre->window) {
+					if (rre->rotation == RR_Rotate_90 ||
+					    rre->rotation == RR_Rotate_270)
+						XResizeWindow(dpy, locks[screen]->win,
+						              rre->height, rre->width);
+					else
+						XResizeWindow(dpy, locks[screen]->win,
+						              rre->width, rre->height);
+					XClearWindow(dpy, locks[screen]->win);
+					break;
+				}
+			}
+		} else {
+			for (screen = 0; screen < nscreens; screen++)
+				XRaiseWindow(dpy, locks[screen]->win);
+		}
+	}
+}
+
+static struct lock *
+lockscreen(Display *dpy, struct xrandr *rr, int screen)
+{
+	char curs[] = {0, 0, 0, 0, 0, 0, 0, 0};
+	int i, ptgrab, kbgrab;
+	struct lock *lock;
+	XColor color, dummy;
+	XSetWindowAttributes wa;
+	Cursor invisible;
+
+	if (dpy == NULL || screen < 0 || !(lock = malloc(sizeof(struct lock))))
+		return NULL;
+
+	lock->screen = screen;
+	lock->root = RootWindow(dpy, lock->screen);
+
+	for (i = 0; i < NUMCOLS; i++) {
+		XAllocNamedColor(dpy, DefaultColormap(dpy, lock->screen),
+		                 colorname[i], &color, &dummy);
+		lock->colors[i] = color.pixel;
+	}
+
+	/* init */
+	wa.override_redirect = 1;
+	wa.background_pixel = lock->colors[INIT];
+	lock->win = XCreateWindow(dpy, lock->root, 0, 0,
+	                          DisplayWidth(dpy, lock->screen),
+	                          DisplayHeight(dpy, lock->screen),
+	                          0, DefaultDepth(dpy, lock->screen),
+	                          CopyFromParent,
+	                          DefaultVisual(dpy, lock->screen),
+	                          CWOverrideRedirect | CWBackPixel, &wa);
+	lock->pmap = XCreateBitmapFromData(dpy, lock->win, curs, 8, 8);
+	invisible = XCreatePixmapCursor(dpy, lock->pmap, lock->pmap,
+	                                &color, &color, 0, 0);
+	XDefineCursor(dpy, lock->win, invisible);
+
+	/* Try to grab mouse pointer *and* keyboard for 600ms, else fail the lock */
+	for (i = 0, ptgrab = kbgrab = -1; i < 6; i++) {
+		if (ptgrab != GrabSuccess) {
+			ptgrab = XGrabPointer(dpy, lock->root, False,
+			                      ButtonPressMask | ButtonReleaseMask |
+			                      PointerMotionMask, GrabModeAsync,
+			                      GrabModeAsync, None, invisible, CurrentTime);
+		}
+		if (kbgrab != GrabSuccess) {
+			kbgrab = XGrabKeyboard(dpy, lock->root, True,
+			                       GrabModeAsync, GrabModeAsync, CurrentTime);
+		}
+
+		/* input is grabbed: we can lock the screen */
+		if (ptgrab == GrabSuccess && kbgrab == GrabSuccess) {
+			XMapRaised(dpy, lock->win);
+			if (rr->active)
+				XRRSelectInput(dpy, lock->win, RRScreenChangeNotifyMask);
+
+			XSelectInput(dpy, lock->root, SubstructureNotifyMask);
+			return lock;
+		}
+
+		/* retry on AlreadyGrabbed but fail on other errors */
+		if ((ptgrab != AlreadyGrabbed && ptgrab != GrabSuccess) ||
+		    (kbgrab != AlreadyGrabbed && kbgrab != GrabSuccess))
+			break;
+
+		usleep(100000);
+	}
+
+	/* we couldn't grab all input: fail out */
+	if (ptgrab != GrabSuccess)
+		fprintf(stderr, "slock: unable to grab mouse pointer for screen %d\n",
+		        screen);
+	if (kbgrab != GrabSuccess)
+		fprintf(stderr, "slock: unable to grab keyboard for screen %d\n",
+		        screen);
+	return NULL;
+}
+
+static void
+usage(void)
+{
+	die("usage: slock [-v] [cmd [arg ...]]\n");
+}
+
+int
+main(int argc, char **argv) {
+	struct xrandr rr;
+	struct lock **locks;
+	struct passwd *pwd;
+	struct group *grp;
+	uid_t duid;
+	gid_t dgid;
+	const char *hash;
+	Display *dpy;
+	int s, nlocks, nscreens;
+
+	ARGBEGIN {
+	case 'v':
+		fprintf(stderr, "slock-"VERSION"\n");
+		return 0;
+	default:
+		usage();
+	} ARGEND
+
+	/* validate drop-user and -group */
+	errno = 0;
+	if (!(pwd = getpwnam(user)))
+		die("slock: getpwnam %s: %s\n", user,
+		    errno ? strerror(errno) : "user entry not found");
+	duid = pwd->pw_uid;
+	errno = 0;
+	if (!(grp = getgrnam(group)))
+		die("slock: getgrnam %s: %s\n", group,
+		    errno ? strerror(errno) : "group entry not found");
+	dgid = grp->gr_gid;
+
+#ifdef __linux__
+	dontkillme();
+#endif
+
+	hash = gethash();
+	errno = 0;
+	if (!crypt("", hash))
+		die("slock: crypt: %s\n", strerror(errno));
+
+	if (!(dpy = XOpenDisplay(NULL)))
+		die("slock: cannot open display\n");
+
+	/* drop privileges */
+	if (setgroups(0, NULL) < 0)
+		die("slock: setgroups: %s\n", strerror(errno));
+	if (setgid(dgid) < 0)
+		die("slock: setgid: %s\n", strerror(errno));
+	if (setuid(duid) < 0)
+		die("slock: setuid: %s\n", strerror(errno));
+
+	/* check for Xrandr support */
+	rr.active = XRRQueryExtension(dpy, &rr.evbase, &rr.errbase);
+
+	/* get number of screens in display "dpy" and blank them */
+	nscreens = ScreenCount(dpy);
+	if (!(locks = calloc(nscreens, sizeof(struct lock *))))
+		die("slock: out of memory\n");
+	for (nlocks = 0, s = 0; s < nscreens; s++) {
+		if ((locks[s] = lockscreen(dpy, &rr, s)) != NULL)
+			nlocks++;
+		else
+			break;
+	}
+	XSync(dpy, 0);
+
+	/* did we manage to lock everything? */
+	if (nlocks != nscreens)
+		return 1;
+
+	/* run post-lock command */
+	if (argc > 0) {
+		switch (fork()) {
+		case -1:
+			die("slock: fork failed: %s\n", strerror(errno));
+		case 0:
+			if (close(ConnectionNumber(dpy)) < 0)
+				die("slock: close: %s\n", strerror(errno));
+			execvp(argv[0], argv);
+			fprintf(stderr, "slock: execvp %s: %s\n", argv[0], strerror(errno));
+			_exit(1);
+		}
+	}
+
+	/* everything is now blank. Wait for the correct password */
+	readpw(dpy, &rr, locks, nscreens, hash);
+
+	return 0;
+}
diff --git a/util.h b/util.h
@@ -0,0 +1,2 @@
+#undef explicit_bzero
+void explicit_bzero(void *, size_t);