slock.c

   1 /* See LICENSE file for license details. */
   2 #define _XOPEN_SOURCE 500
   3 #if HAVE_SHADOW_H
   4 #include <shadow.h>
   5 #endif
   6
   7 #include <ctype.h>
   8 #include <errno.h>
   9 #include <pwd.h>
  10 #include <stdarg.h>
  11 #include <stdlib.h>
  12 #include <stdio.h>
  13 #include <string.h>
  14 #include <unistd.h>
  15 #include <sys/types.h>
  16 #include <X11/extensions/Xrandr.h>
  17 #include <X11/keysym.h>
  18 #include <X11/Xlib.h>
  19 #include <X11/Xutil.h>
  20
  21 #if HAVE_BSD_AUTH
  22 #include <login_cap.h>
  23 #include <bsd_auth.h>
  24 #endif
  25
  26 #include "arg.h"
  27 #include "util.h"
  28
  29 char *argv0;
  30
  31 enum {
  32         INIT,
  33         INPUT,
  34         FAILED,
  35         NUMCOLS
  36 };
  37
  38 #include "config.h"
  39
  40 typedef struct {
  41         int screen;
  42         Window root, win;
  43         Pixmap pmap;
  44         unsigned long colors[NUMCOLS];
  45 } Lock;
  46
  47 static Lock **locks;
  48 static int nscreens;
  49 static Bool running = True;
  50 static Bool failure = False;
  51 static Bool rr;
  52 static int rrevbase;
  53 static int rrerrbase;
  54
  55 static void
  56 die(const char *errstr, ...)
  57 {
  58         va_list ap;
  59
  60         va_start(ap, errstr);
  61         vfprintf(stderr, errstr, ap);
  62         va_end(ap);
  63         exit(1);
  64 }
  65
  66 #ifdef __linux__
  67 #include <fcntl.h>
  68 #include <linux/oom.h>
  69
  70 static void
  71 dontkillme(void)
  72 {
  73         FILE *f;
  74         const char oomfile[] = "/proc/self/oom_score_adj";
  75
  76         if (!(f = fopen(oomfile, "w"))) {
  77                 if (errno == ENOENT)
  78                         return;
  79                 die("slock: fopen %s: %s\n", oomfile, strerror(errno));
  80         }
  81         fprintf(f, "%d", OOM_SCORE_ADJ_MIN);
  82         if (fclose(f)) {
  83                 if (errno == EACCES)
  84                         die("slock: unable to disable OOM killer. "
  85                             "suid or sgid set?\n");
  86                 else
  87                         die("slock: fclose %s: %s\n", oomfile,
  88                             strerror(errno));
  89         }
  90 }
  91 #endif
  92
  93 #ifndef HAVE_BSD_AUTH
  94 /* only run as root */
  95 static const char *
  96 getpw(void)
  97 {
  98         const char *rval;
  99         struct passwd *pw;
 100
 101         errno = 0;
 102         if (!(pw = getpwuid(getuid()))) {
 103                 if (errno)
 104                         die("getpwuid: %s\n", strerror(errno));
 105                 else
 106                         die("cannot retrieve password entry\n");
 107         }
 108         rval = pw->pw_passwd;
 109
 110 #if HAVE_SHADOW_H
 111         if (rval[0] == 'x' && rval[1] == '\0') {
 112                 struct spwd *sp;
 113                 if (!(sp = getspnam(getenv("USER"))))
 114                         die("cannot retrieve shadow entry (make sure to suid or sgid slock)\n");
 115                 rval = sp->sp_pwdp;
 116         }
 117 #endif
 118
 119         /* drop privileges */
 120         if (geteuid() == 0 &&
 121             ((getegid() != pw->pw_gid && setgid(pw->pw_gid) < 0) || setuid(pw->pw_uid) < 0))
 122                 die("cannot drop privileges\n");
 123         return rval;
 124 }
 125 #endif
 126
 127 static void
 128 #ifdef HAVE_BSD_AUTH
 129 readpw(Display *dpy)
 130 #else
 131 readpw(Display *dpy, const char *pws)
 132 #endif
 133 {
 134         char buf[32], passwd[256], *encrypted;
 135         int num, screen;
 136         unsigned int len, color;
 137         KeySym ksym;
 138         XEvent ev;
 139         static int oldc = INIT;
 140
 141         len = 0;
 142         running = True;
 143
 144         /* As "slock" stands for "Simple X display locker", the DPMS settings
 145          * had been removed and you can set it with "xset" or some other
 146          * utility. This way the user can easily set a customized DPMS
 147          * timeout. */
 148         while (running && !XNextEvent(dpy, &ev)) {
 149                 if (ev.type == KeyPress) {
 150                         explicit_bzero(&buf, sizeof(buf));
 151                         num = XLookupString(&ev.xkey, buf, sizeof(buf), &ksym, 0);
 152                         if (IsKeypadKey(ksym)) {
 153                                 if (ksym == XK_KP_Enter)
 154                                         ksym = XK_Return;
 155                                 else if (ksym >= XK_KP_0 && ksym <= XK_KP_9)
 156                                         ksym = (ksym - XK_KP_0) + XK_0;
 157                         }
 158                         if (IsFunctionKey(ksym) ||
 159                             IsKeypadKey(ksym) ||
 160                             IsMiscFunctionKey(ksym) ||
 161                             IsPFKey(ksym) ||
 162                             IsPrivateKeypadKey(ksym))
 163                                 continue;
 164                         switch (ksym) {
 165                         case XK_Return:
 166                                 passwd[len] = 0;
 167 #ifdef HAVE_BSD_AUTH
 168                                 running = !auth_userokay(getlogin(), NULL, "auth-slock", passwd);
 169 #else
 170                                 errno = 0;
 171                                 if (!(encrypted = crypt(passwd, pws)))
 172                                         fprintf(stderr, "slock: crypt: %s\n", strerror(errno));
 173                                 else
 174                                         running = !!strcmp(encrypted, pws);
 175 #endif
 176                                 if (running) {
 177                                         XBell(dpy, 100);
 178                                         failure = True;
 179                                 }
 180                                 explicit_bzero(&passwd, sizeof(passwd));
 181                                 len = 0;
 182                                 break;
 183                         case XK_Escape:
 184                                 explicit_bzero(&passwd, sizeof(passwd));
 185                                 len = 0;
 186                                 break;
 187                         case XK_BackSpace:
 188                                 if (len)
 189                                         passwd[len--] = 0;
 190                                 break;
 191                         default:
 192                                 if (num && !iscntrl((int)buf[0]) && (len + num < sizeof(passwd))) {
 193                                         memcpy(passwd + len, buf, num);
 194                                         len += num;
 195                                 }
 196                                 break;
 197                         }
 198                         color = len ? INPUT : (failure || failonclear ? FAILED : INIT);
 199                         if (running && oldc != color) {
 200                                 for (screen = 0; screen < nscreens; screen++) {
 201                                         XSetWindowBackground(dpy, locks[screen]->win, locks[screen]->colors[color]);
 202                                         XClearWindow(dpy, locks[screen]->win);
 203                                 }
 204                                 oldc = color;
 205                         }
 206                 } else if (rr && ev.type == rrevbase + RRScreenChangeNotify) {
 207                         XRRScreenChangeNotifyEvent *rre = (XRRScreenChangeNotifyEvent*)&ev;
 208                         for (screen = 0; screen < nscreens; screen++) {
 209                                 if (locks[screen]->win == rre->window) {
 210                                         XResizeWindow(dpy, locks[screen]->win, rre->width, rre->height);
 211                                         XClearWindow(dpy, locks[screen]->win);
 212                                 }
 213                         }
 214                 } else for (screen = 0; screen < nscreens; screen++)
 215                         XRaiseWindow(dpy, locks[screen]->win);
 216         }
 217 }
 218
 219 static void
 220 unlockscreen(Display *dpy, Lock *lock)
 221 {
 222         if(dpy == NULL || lock == NULL)
 223                 return;
 224
 225         XUngrabPointer(dpy, CurrentTime);
 226         XUngrabKeyboard(dpy, CurrentTime);
 227         XFreeColors(dpy, DefaultColormap(dpy, lock->screen), lock->colors, NUMCOLS, 0);
 228         XFreePixmap(dpy, lock->pmap);
 229         XDestroyWindow(dpy, lock->win);
 230
 231         free(lock);
 232 }
 233
 234 static void
 235 cleanup(Display *dpy)
 236 {
 237         free(locks);
 238         XCloseDisplay(dpy);
 239 }
 240
 241 static Lock *
 242 lockscreen(Display *dpy, int screen)
 243 {
 244         char curs[] = {0, 0, 0, 0, 0, 0, 0, 0};
 245         int i, ptgrab, kbgrab;
 246         Lock *lock;
 247         XColor color, dummy;
 248         XSetWindowAttributes wa;
 249         Cursor invisible;
 250
 251         if (!running || dpy == NULL || screen < 0 || !(lock = malloc(sizeof(Lock))))
 252                 return NULL;
 253
 254         lock->screen = screen;
 255         lock->root = RootWindow(dpy, lock->screen);
 256
 257         for (i = 0; i < NUMCOLS; i++) {
 258                 XAllocNamedColor(dpy, DefaultColormap(dpy, lock->screen), colorname[i], &color, &dummy);
 259                 lock->colors[i] = color.pixel;
 260         }
 261
 262         /* init */
 263         wa.override_redirect = 1;
 264         wa.background_pixel = lock->colors[INIT];
 265         lock->win = XCreateWindow(dpy, lock->root, 0, 0, DisplayWidth(dpy, lock->screen), DisplayHeight(dpy, lock->screen),
 266                                   0, DefaultDepth(dpy, lock->screen), CopyFromParent,
 267                                   DefaultVisual(dpy, lock->screen), CWOverrideRedirect | CWBackPixel, &wa);
 268         lock->pmap = XCreateBitmapFromData(dpy, lock->win, curs, 8, 8);
 269         invisible = XCreatePixmapCursor(dpy, lock->pmap, lock->pmap, &color, &color, 0, 0);
 270         XDefineCursor(dpy, lock->win, invisible);
 271
 272         /* Try to grab mouse pointer *and* keyboard for 600ms, else fail the lock */
 273         for (i = 6, ptgrab = kbgrab = -1; i; --i) {
 274                 if (ptgrab != GrabSuccess) {
 275                         ptgrab = XGrabPointer(dpy, lock->root, False,
 276                                  ButtonPressMask | ButtonReleaseMask |
 277                                  PointerMotionMask, GrabModeAsync,
 278                                  GrabModeAsync, None, invisible, CurrentTime);
 279                 }
 280                 if (kbgrab != GrabSuccess) {
 281                         kbgrab = XGrabKeyboard(dpy, lock->root, True,
 282                                  GrabModeAsync, GrabModeAsync, CurrentTime);
 283                 }
 284
 285                 /* input is grabbed: we can lock the screen */
 286                 if (ptgrab == GrabSuccess && kbgrab == GrabSuccess) {
 287                         XMapRaised(dpy, lock->win);
 288                         if (rr)
 289                                 XRRSelectInput(dpy, lock->win, RRScreenChangeNotifyMask);
 290
 291                         XSelectInput(dpy, lock->root, SubstructureNotifyMask);
 292                         return lock;
 293                 }
 294
 295                 /* retry on AlreadyGrabbed but fail on other errors */
 296                 if ((ptgrab != AlreadyGrabbed && ptgrab != GrabSuccess) ||
 297                     (kbgrab != AlreadyGrabbed && kbgrab != GrabSuccess))
 298                         break;
 299
 300                 usleep(100000);
 301         }
 302
 303         /* we couldn't grab all input: fail out */
 304         if (ptgrab != GrabSuccess)
 305                 fprintf(stderr, "slock: unable to grab mouse pointer for screen %d\n", screen);
 306         if (kbgrab != GrabSuccess)
 307                 fprintf(stderr, "slock: unable to grab keyboard for screen %d\n", screen);
 308         running = 0;
 309         unlockscreen(dpy, lock);
 310         return NULL;
 311 }
 312
 313 static void
 314 usage(void)
 315 {
 316         die("usage: slock [-v] [cmd [arg ...]]\n");
 317 }
 318
 319 int
 320 main(int argc, char **argv) {
 321 #ifndef HAVE_BSD_AUTH
 322         const char *pws;
 323 #endif
 324         Display *dpy;
 325         int s, nlocks;
 326
 327         ARGBEGIN {
 328         case 'v':
 329                 fprintf(stderr, "slock-"VERSION"\n");
 330                 return 0;
 331         default:
 332                 usage();
 333         } ARGEND
 334
 335 #ifdef __linux__
 336         dontkillme();
 337 #endif
 338
 339         /* Check if the current user has a password entry */
 340         errno = 0;
 341         if (!getpwuid(getuid())) {
 342                 if (errno == 0)
 343                         die("slock: no password entry for current user\n");
 344                 else
 345                         die("slock: getpwuid: %s\n", strerror(errno));
 346         }
 347
 348 #ifndef HAVE_BSD_AUTH
 349         pws = getpw();
 350         if (strlen(pws) < 2)
 351                 die("slock: failed to get user password hash.\n");
 352 #endif
 353
 354         if (!(dpy = XOpenDisplay(NULL)))
 355                 die("slock: cannot open display\n");
 356
 357         /* check for Xrandr support */
 358         rr = XRRQueryExtension(dpy, &rrevbase, &rrerrbase);
 359
 360         /* get number of screens in display "dpy" and blank them */
 361         nscreens = ScreenCount(dpy);
 362         if (!(locks = malloc(sizeof(Lock *) * nscreens))) {
 363                 XCloseDisplay(dpy);
 364                 die("slock: out of memory\n");
 365         }
 366         for (nlocks = 0, s = 0; s < nscreens; s++) {
 367                 if ((locks[s] = lockscreen(dpy, s)) != NULL)
 368                         nlocks++;
 369         }
 370         XSync(dpy, 0);
 371
 372         /* did we actually manage to lock anything? */
 373         if (nlocks == 0) {
 374                 /* nothing to protect */
 375                 cleanup(dpy);
 376                 return 1;
 377         }
 378
 379         /* run post-lock command */
 380         if (argc > 0) {
 381                 switch (fork()) {
 382                 case -1:
 383                         cleanup(dpy);
 384                         die("slock: fork failed: %s\n", strerror(errno));
 385                 case 0:
 386                         if (close(ConnectionNumber(dpy)) < 0)
 387                                 die("slock: close: %s\n", strerror(errno));
 388                         execvp(argv[0], argv);
 389                         fprintf(stderr, "slock: execvp %s: %s\n", argv[0],
 390                                 strerror(errno));
 391                         _exit(1);
 392                 }
 393         }
 394
 395         /* everything is now blank. Wait for the correct password */
 396 #ifdef HAVE_BSD_AUTH
 397         readpw(dpy);
 398 #else
 399         readpw(dpy, pws);
 400 #endif
 401
 402         /* password ok, unlock everything and quit */
 403         for (s = 0; s < nscreens; s++)
 404                 unlockscreen(dpy, locks[s]);
 405
 406         cleanup(dpy);
 407
 408         return 0;
 409 }