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