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 struct lock {
  37         int screen;
  38         Window root, win;
  39         Pixmap pmap;
  40         unsigned long colors[NUMCOLS];
  41 };
  42
  43 struct xrandr {
  44         int active;
  45         int evbase;
  46         int errbase;
  47 };
  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 gethash(void)
  89 {
  90         const char *hash;
  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         hash = pw->pw_passwd;
 102
 103 #if HAVE_SHADOW_H
 104         if (hash[0] == 'x' && hash[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                 hash = sp->sp_pwdp;
 109         }
 110 #else
 111         if (hash[0] == '*' && hash[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                 hash = 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 hash;
 123 }
 124
 125 static void
 126 readpw(Display *dpy, struct xrandr *rr, struct lock **locks, int nscreens,
 127        const char *hash)
 128 {
 129         char buf[32], passwd[256], *inputhash;
 130         int num, screen, running, failure;
 131         unsigned int len, color;
 132         KeySym ksym;
 133         XEvent ev;
 134         static int oldc = INIT;
 135
 136         len = 0;
 137         running = 1;
 138         failure = 0;
 139
 140         /* As "slock" stands for "Simple X display locker", the DPMS settings
 141          * had been removed and you can set it with "xset" or some other
 142          * utility. This way the user can easily set a customized DPMS
 143          * timeout. */
 144         while (running && !XNextEvent(dpy, &ev)) {
 145                 if (ev.type == KeyPress) {
 146                         explicit_bzero(&buf, sizeof(buf));
 147                         num = XLookupString(&ev.xkey, buf, sizeof(buf), &ksym, 0);
 148                         if (IsKeypadKey(ksym)) {
 149                                 if (ksym == XK_KP_Enter)
 150                                         ksym = XK_Return;
 151                                 else if (ksym >= XK_KP_0 && ksym <= XK_KP_9)
 152                                         ksym = (ksym - XK_KP_0) + XK_0;
 153                         }
 154                         if (IsFunctionKey(ksym) ||
 155                             IsKeypadKey(ksym) ||
 156                             IsMiscFunctionKey(ksym) ||
 157                             IsPFKey(ksym) ||
 158                             IsPrivateKeypadKey(ksym))
 159                                 continue;
 160                         switch (ksym) {
 161                         case XK_Return:
 162                                 passwd[len] = 0;
 163                                 errno = 0;
 164                                 if (!(inputhash = crypt(passwd, hash)))
 165                                         fprintf(stderr, "slock: crypt: %s\n", strerror(errno));
 166                                 else
 167                                         running = !!strcmp(inputhash, hash);
 168                                 if (running) {
 169                                         XBell(dpy, 100);
 170                                         failure = True;
 171                                 }
 172                                 explicit_bzero(&passwd, sizeof(passwd));
 173                                 len = 0;
 174                                 break;
 175                         case XK_Escape:
 176                                 explicit_bzero(&passwd, sizeof(passwd));
 177                                 len = 0;
 178                                 break;
 179                         case XK_BackSpace:
 180                                 if (len)
 181                                         passwd[len--] = 0;
 182                                 break;
 183                         default:
 184                                 if (num && !iscntrl((int)buf[0]) && (len + num < sizeof(passwd))) {
 185                                         memcpy(passwd + len, buf, num);
 186                                         len += num;
 187                                 }
 188                                 break;
 189                         }
 190                         color = len ? INPUT : (failure || failonclear ? FAILED : INIT);
 191                         if (running && oldc != color) {
 192                                 for (screen = 0; screen < nscreens; screen++) {
 193                                         XSetWindowBackground(dpy, locks[screen]->win, locks[screen]->colors[color]);
 194                                         XClearWindow(dpy, locks[screen]->win);
 195                                 }
 196                                 oldc = color;
 197                         }
 198                 } else if (rr->active && ev.type == rr->evbase + RRScreenChangeNotify) {
 199                         XRRScreenChangeNotifyEvent *rre = (XRRScreenChangeNotifyEvent*)&ev;
 200                         for (screen = 0; screen < nscreens; screen++) {
 201                                 if (locks[screen]->win == rre->window) {
 202                                         XResizeWindow(dpy, locks[screen]->win, rre->width, rre->height);
 203                                         XClearWindow(dpy, locks[screen]->win);
 204                                 }
 205                         }
 206                 } else for (screen = 0; screen < nscreens; screen++)
 207                         XRaiseWindow(dpy, locks[screen]->win);
 208         }
 209 }
 210
 211 static struct lock *
 212 lockscreen(Display *dpy, struct xrandr *rr, int screen)
 213 {
 214         char curs[] = {0, 0, 0, 0, 0, 0, 0, 0};
 215         int i, ptgrab, kbgrab;
 216         struct lock *lock;
 217         XColor color, dummy;
 218         XSetWindowAttributes wa;
 219         Cursor invisible;
 220
 221         if (dpy == NULL || screen < 0 || !(lock = malloc(sizeof(struct lock))))
 222                 return NULL;
 223
 224         lock->screen = screen;
 225         lock->root = RootWindow(dpy, lock->screen);
 226
 227         for (i = 0; i < NUMCOLS; i++) {
 228                 XAllocNamedColor(dpy, DefaultColormap(dpy, lock->screen), colorname[i], &color, &dummy);
 229                 lock->colors[i] = color.pixel;
 230         }
 231
 232         /* init */
 233         wa.override_redirect = 1;
 234         wa.background_pixel = lock->colors[INIT];
 235         lock->win = XCreateWindow(dpy, lock->root, 0, 0, DisplayWidth(dpy, lock->screen), DisplayHeight(dpy, lock->screen),
 236                                   0, DefaultDepth(dpy, lock->screen), CopyFromParent,
 237                                   DefaultVisual(dpy, lock->screen), CWOverrideRedirect | CWBackPixel, &wa);
 238         lock->pmap = XCreateBitmapFromData(dpy, lock->win, curs, 8, 8);
 239         invisible = XCreatePixmapCursor(dpy, lock->pmap, lock->pmap, &color, &color, 0, 0);
 240         XDefineCursor(dpy, lock->win, invisible);
 241
 242         /* Try to grab mouse pointer *and* keyboard for 600ms, else fail the lock */
 243         for (i = 0, ptgrab = kbgrab = -1; i < 6; i++) {
 244                 if (ptgrab != GrabSuccess) {
 245                         ptgrab = XGrabPointer(dpy, lock->root, False,
 246                                  ButtonPressMask | ButtonReleaseMask |
 247                                  PointerMotionMask, GrabModeAsync,
 248                                  GrabModeAsync, None, invisible, CurrentTime);
 249                 }
 250                 if (kbgrab != GrabSuccess) {
 251                         kbgrab = XGrabKeyboard(dpy, lock->root, True,
 252                                  GrabModeAsync, GrabModeAsync, CurrentTime);
 253                 }
 254
 255                 /* input is grabbed: we can lock the screen */
 256                 if (ptgrab == GrabSuccess && kbgrab == GrabSuccess) {
 257                         XMapRaised(dpy, lock->win);
 258                         if (rr->active)
 259                                 XRRSelectInput(dpy, lock->win, RRScreenChangeNotifyMask);
 260
 261                         XSelectInput(dpy, lock->root, SubstructureNotifyMask);
 262                         return lock;
 263                 }
 264
 265                 /* retry on AlreadyGrabbed but fail on other errors */
 266                 if ((ptgrab != AlreadyGrabbed && ptgrab != GrabSuccess) ||
 267                     (kbgrab != AlreadyGrabbed && kbgrab != GrabSuccess))
 268                         break;
 269
 270                 usleep(100000);
 271         }
 272
 273         /* we couldn't grab all input: fail out */
 274         if (ptgrab != GrabSuccess)
 275                 fprintf(stderr, "slock: unable to grab mouse pointer for screen %d\n", screen);
 276         if (kbgrab != GrabSuccess)
 277                 fprintf(stderr, "slock: unable to grab keyboard for screen %d\n", screen);
 278         return NULL;
 279 }
 280
 281 static void
 282 usage(void)
 283 {
 284         die("usage: slock [-v] [cmd [arg ...]]\n");
 285 }
 286
 287 int
 288 main(int argc, char **argv) {
 289         struct xrandr rr;
 290         struct lock **locks;
 291         struct passwd *pwd;
 292         struct group *grp;
 293         uid_t duid;
 294         gid_t dgid;
 295         const char *hash;
 296         Display *dpy;
 297         int s, nlocks, nscreens;
 298
 299         ARGBEGIN {
 300         case 'v':
 301                 fprintf(stderr, "slock-"VERSION"\n");
 302                 return 0;
 303         default:
 304                 usage();
 305         } ARGEND
 306
 307         /* validate drop-user and -group */
 308         errno = 0;
 309         if (!(pwd = getpwnam(user)))
 310                 die("slock: getpwnam %s: %s\n", user, errno ?
 311                     strerror(errno) : "user entry not found");
 312         duid = pwd->pw_uid;
 313         errno = 0;
 314         if (!(grp = getgrnam(group)))
 315                 die("slock: getgrnam %s: %s\n", group, errno ?
 316                     strerror(errno) : "group entry not found");
 317         dgid = grp->gr_gid;
 318
 319 #ifdef __linux__
 320         dontkillme();
 321 #endif
 322
 323         hash = gethash();
 324         if (strlen(hash) < 2)
 325                 die("slock: failed to get user password hash.\n");
 326
 327         if (!(dpy = XOpenDisplay(NULL)))
 328                 die("slock: cannot open display\n");
 329
 330         /* drop privileges */
 331         if (setgroups(0, NULL) < 0)
 332                 die("slock: setgroups: %s\n", strerror(errno));
 333         if (setgid(dgid) < 0)
 334                 die("slock: setgid: %s\n", strerror(errno));
 335         if (setuid(duid) < 0)
 336                 die("slock: setuid: %s\n", strerror(errno));
 337
 338         /* check for Xrandr support */
 339         rr.active = XRRQueryExtension(dpy, &rr.evbase, &rr.errbase);
 340
 341         /* get number of screens in display "dpy" and blank them */
 342         nscreens = ScreenCount(dpy);
 343         if (!(locks = calloc(nscreens, sizeof(struct lock *))))
 344                 die("slock: out of memory\n");
 345         for (nlocks = 0, s = 0; s < nscreens; s++) {
 346                 if ((locks[s] = lockscreen(dpy, &rr, s)) != NULL)
 347                         nlocks++;
 348                 else
 349                         break;
 350         }
 351         XSync(dpy, 0);
 352
 353         /* did we manage to lock everything? */
 354         if (nlocks != nscreens)
 355                 return 1;
 356
 357         /* run post-lock command */
 358         if (argc > 0) {
 359                 switch (fork()) {
 360                 case -1:
 361                         die("slock: fork failed: %s\n", strerror(errno));
 362                 case 0:
 363                         if (close(ConnectionNumber(dpy)) < 0)
 364                                 die("slock: close: %s\n", strerror(errno));
 365                         execvp(argv[0], argv);
 366                         fprintf(stderr, "slock: execvp %s: %s\n", argv[0],
 367                                 strerror(errno));
 368                         _exit(1);
 369                 }
 370         }
 371
 372         /* everything is now blank. Wait for the correct password */
 373         readpw(dpy, &rr, locks, nscreens, hash);
 374
 375         return 0;
 376 }