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slock
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adding basic slock

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TiynGER 5 years ago
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24
LICENSE
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MIT/X Consortium License
© 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>
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.

61
Makefile
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# 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
config.h:
@echo creating $@ from config.def.h
@cp config.def.h $@
slock: ${OBJ}
@echo CC -o $@
@${CC} -o $@ ${OBJ} ${LDFLAGS}
clean:
@echo cleaning
@rm -f slock ${OBJ} slock-${VERSION}.tar.gz
dist: clean
@echo creating dist tarball
@mkdir -p slock-${VERSION}
@cp -R LICENSE Makefile README slock.1 config.mk \
${SRC} explicit_bzero.c config.def.h arg.h util.h slock-${VERSION}
@tar -cf slock-${VERSION}.tar slock-${VERSION}
@gzip slock-${VERSION}.tar
@rm -rf slock-${VERSION}
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
@echo installing manual page to ${DESTDIR}${MANPREFIX}/man1
@mkdir -p ${DESTDIR}${MANPREFIX}/man1
@sed "s/VERSION/${VERSION}/g" <slock.1 >${DESTDIR}${MANPREFIX}/man1/slock.1
@chmod 644 ${DESTDIR}${MANPREFIX}/man1/slock.1
uninstall:
@echo removing executable file from ${DESTDIR}${PREFIX}/bin
@rm -f ${DESTDIR}${PREFIX}/bin/slock
@echo removing manual page from ${DESTDIR}${MANPREFIX}/man1
@rm -f ${DESTDIR}${MANPREFIX}/man1/slock.1
.PHONY: all options clean dist install uninstall

65
arg.h
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/*
* 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

12
config.def.h
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/* 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;

32
config.mk
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# 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

19
explicit_bzero.c
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/* $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);
}

39
slock.1
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.Dd 2016-08-23
.Dt SLOCK 1
.Sh NAME
.Nm slock
.Nd simple X screen locker
.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 Op Ar arg ...
is executed after the screen has been locked.
.Sh OPTIONS
.Bl -tag -width Ds
.It Fl v
Print version information to stdout and exit.
.El
.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
to disable both in
.Xr xorg.conf 5
for maximum security:
.Bd -literal -offset left
Section "ServerFlags"
Option "DontVTSwitch" "True"
Option "DontZap" "True"
EndSection
.Ed
.Sh EXAMPLES
$
.Nm
/usr/sbin/s2ram
.Sh CUSTOMIZATION
.Nm
can be customized by creating a custom config.h from config.def.h and
(re)compiling the source code. This keeps it fast, secure and simple.

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slock.c
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/* 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;
}

2
util.h
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#undef explicit_bzero
void explicit_bzero(void *, size_t);
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