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                             "Make sure to suid or sgid slock.\n");
  80                 else
  81                         die("slock: fclose %s: %s\n", oomfile, strerror(errno));
  82         }
  83 }
  84 #endif
  85
  86 static const char *
  87 gethash(void)
  88 {
  89         const char *hash;
  90         struct passwd *pw;
  91
  92         /* Check if the current user has a password entry */
  93         errno = 0;
  94         if (!(pw = getpwuid(getuid()))) {
  95                 if (errno)
  96                         die("slock: getpwuid: %s\n", strerror(errno));
  97                 else
  98                         die("slock: cannot retrieve password entry\n");
  99         }
 100         hash = pw->pw_passwd;
 101
 102 #if HAVE_SHADOW_H
 103         if (hash[0] == 'x' && hash[1] == '\0') {
 104                 struct spwd *sp;
 105                 if (!(sp = getspnam(pw->pw_name)))
 106                         die("slock: getspnam: cannot retrieve shadow entry. "
 107                             "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 = getpwuid_shadow(getuid())))
 114                         die("slock: getpwnam_shadow: cannot retrieve shadow entry. "
 115                             "Make sure to suid or sgid slock.\n");
 116                 hash = pw->pw_passwd;
 117 #else
 118                 die("slock: getpwuid: cannot retrieve shadow entry. "
 119                     "Make sure to suid or sgid slock.\n");
 120 #endif /* __OpenBSD__ */
 121         }
 122 #endif /* HAVE_SHADOW_H */
 123
 124         return hash;
 125 }
 126
 127 static void
 128 readpw(Display *dpy, struct xrandr *rr, struct lock **locks, int nscreens,
 129        const char *hash)
 130 {
 131         XRRScreenChangeNotifyEvent *rre;
 132         char buf[32], passwd[256], *inputhash;
 133         int num, screen, running, failure;
 134         unsigned int len, color;
 135         KeySym ksym;
 136         XEvent ev;
 137         static int oldc = INIT;
 138
 139         len = 0;
 140         running = 1;
 141         failure = 0;
 142
 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 (!(inputhash = crypt(passwd, hash)))
 164                                         fprintf(stderr, "slock: crypt: %s\n", strerror(errno));
 165                                 else
 166                                         running = !!strcmp(inputhash, hash);
 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]) &&
 184                                     (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,
 194                                                              locks[screen]->win,
 195                                                              locks[screen]->colors[color]);
 196                                         XClearWindow(dpy, locks[screen]->win);
 197                                 }
 198                                 oldc = color;
 199                         }
 200                 } else if (rr->active && ev.type == rr->evbase + RRScreenChangeNotify) {
 201                         rre = (XRRScreenChangeNotifyEvent*)&ev;
 202                         for (screen = 0; screen < nscreens; screen++) {
 203                                 if (locks[screen]->win == rre->window) {
 204                                         XResizeWindow(dpy, locks[screen]->win,
 205                                                       rre->width, rre->height);
 206                                         XClearWindow(dpy, locks[screen]->win);
 207                                 }
 208                         }
 209                 } else for (screen = 0; screen < nscreens; screen++)
 210                         XRaiseWindow(dpy, locks[screen]->win);
 211         }
 212 }
 213
 214 static struct lock *
 215 lockscreen(Display *dpy, struct xrandr *rr, int screen)
 216 {
 217         char curs[] = {0, 0, 0, 0, 0, 0, 0, 0};
 218         int i, ptgrab, kbgrab;
 219         struct lock *lock;
 220         XColor color, dummy;
 221         XSetWindowAttributes wa;
 222         Cursor invisible;
 223
 224         if (dpy == NULL || screen < 0 || !(lock = malloc(sizeof(struct lock))))
 225                 return NULL;
 226
 227         lock->screen = screen;
 228         lock->root = RootWindow(dpy, lock->screen);
 229
 230         for (i = 0; i < NUMCOLS; i++) {
 231                 XAllocNamedColor(dpy, DefaultColormap(dpy, lock->screen),
 232                                  colorname[i], &color, &dummy);
 233                 lock->colors[i] = color.pixel;
 234         }
 235
 236         /* init */
 237         wa.override_redirect = 1;
 238         wa.background_pixel = lock->colors[INIT];
 239         lock->win = XCreateWindow(dpy, lock->root, 0, 0,
 240                                   DisplayWidth(dpy, lock->screen),
 241                                   DisplayHeight(dpy, lock->screen),
 242                                   0, DefaultDepth(dpy, lock->screen),
 243                                   CopyFromParent,
 244                                   DefaultVisual(dpy, lock->screen),
 245                                   CWOverrideRedirect | CWBackPixel, &wa);
 246         lock->pmap = XCreateBitmapFromData(dpy, lock->win, curs, 8, 8);
 247         invisible = XCreatePixmapCursor(dpy, lock->pmap, lock->pmap,
 248                                         &color, &color, 0, 0);
 249         XDefineCursor(dpy, lock->win, invisible);
 250
 251         /* Try to grab mouse pointer *and* keyboard for 600ms, else fail the lock */
 252         for (i = 0, ptgrab = kbgrab = -1; i < 6; i++) {
 253                 if (ptgrab != GrabSuccess) {
 254                         ptgrab = XGrabPointer(dpy, lock->root, False,
 255                                               ButtonPressMask | ButtonReleaseMask |
 256                                               PointerMotionMask, GrabModeAsync,
 257                                               GrabModeAsync, None, invisible, CurrentTime);
 258                 }
 259                 if (kbgrab != GrabSuccess) {
 260                         kbgrab = XGrabKeyboard(dpy, lock->root, True,
 261                                                GrabModeAsync, GrabModeAsync, CurrentTime);
 262                 }
 263
 264                 /* input is grabbed: we can lock the screen */
 265                 if (ptgrab == GrabSuccess && kbgrab == GrabSuccess) {
 266                         XMapRaised(dpy, lock->win);
 267                         if (rr->active)
 268                                 XRRSelectInput(dpy, lock->win, RRScreenChangeNotifyMask);
 269
 270                         XSelectInput(dpy, lock->root, SubstructureNotifyMask);
 271                         return lock;
 272                 }
 273
 274                 /* retry on AlreadyGrabbed but fail on other errors */
 275                 if ((ptgrab != AlreadyGrabbed && ptgrab != GrabSuccess) ||
 276                     (kbgrab != AlreadyGrabbed && kbgrab != GrabSuccess))
 277                         break;
 278
 279                 usleep(100000);
 280         }
 281
 282         /* we couldn't grab all input: fail out */
 283         if (ptgrab != GrabSuccess)
 284                 fprintf(stderr, "slock: unable to grab mouse pointer for screen %d\n",
 285                         screen);
 286         if (kbgrab != GrabSuccess)
 287                 fprintf(stderr, "slock: unable to grab keyboard for screen %d\n",
 288                         screen);
 289         return NULL;
 290 }
 291
 292 static void
 293 usage(void)
 294 {
 295         die("usage: slock [-v] [cmd [arg ...]]\n");
 296 }
 297
 298 int
 299 main(int argc, char **argv) {
 300         struct xrandr rr;
 301         struct lock **locks;
 302         struct passwd *pwd;
 303         struct group *grp;
 304         uid_t duid;
 305         gid_t dgid;
 306         const char *hash;
 307         Display *dpy;
 308         int s, nlocks, nscreens;
 309
 310         ARGBEGIN {
 311         case 'v':
 312                 fprintf(stderr, "slock-"VERSION"\n");
 313                 return 0;
 314         default:
 315                 usage();
 316         } ARGEND
 317
 318         /* validate drop-user and -group */
 319         errno = 0;
 320         if (!(pwd = getpwnam(user)))
 321                 die("slock: getpwnam %s: %s\n", user,
 322                     errno ? strerror(errno) : "user entry not found");
 323         duid = pwd->pw_uid;
 324         errno = 0;
 325         if (!(grp = getgrnam(group)))
 326                 die("slock: getgrnam %s: %s\n", group,
 327                     errno ? strerror(errno) : "group entry not found");
 328         dgid = grp->gr_gid;
 329
 330 #ifdef __linux__
 331         dontkillme();
 332 #endif
 333
 334         hash = gethash();
 335         errno = 0;
 336         if (!crypt("", hash))
 337                 die("slock: crypt: %s\n", strerror(errno));
 338
 339         if (!(dpy = XOpenDisplay(NULL)))
 340                 die("slock: cannot open display\n");
 341
 342         /* drop privileges */
 343         if (setgroups(0, NULL) < 0)
 344                 die("slock: setgroups: %s\n", strerror(errno));
 345         if (setgid(dgid) < 0)
 346                 die("slock: setgid: %s\n", strerror(errno));
 347         if (setuid(duid) < 0)
 348                 die("slock: setuid: %s\n", strerror(errno));
 349
 350         /* check for Xrandr support */
 351         rr.active = XRRQueryExtension(dpy, &rr.evbase, &rr.errbase);
 352
 353         /* get number of screens in display "dpy" and blank them */
 354         nscreens = ScreenCount(dpy);
 355         if (!(locks = calloc(nscreens, sizeof(struct lock *))))
 356                 die("slock: out of memory\n");
 357         for (nlocks = 0, s = 0; s < nscreens; s++) {
 358                 if ((locks[s] = lockscreen(dpy, &rr, s)) != NULL)
 359                         nlocks++;
 360                 else
 361                         break;
 362         }
 363         XSync(dpy, 0);
 364
 365         /* did we manage to lock everything? */
 366         if (nlocks != nscreens)
 367                 return 1;
 368
 369         /* run post-lock command */
 370         if (argc > 0) {
 371                 switch (fork()) {
 372                 case -1:
 373                         die("slock: fork failed: %s\n", strerror(errno));
 374                 case 0:
 375                         if (close(ConnectionNumber(dpy)) < 0)
 376                                 die("slock: close: %s\n", strerror(errno));
 377                         execvp(argv[0], argv);
 378                         fprintf(stderr, "slock: execvp %s: %s\n", argv[0], strerror(errno));
 379                         _exit(1);
 380                 }
 381         }
 382
 383         /* everything is now blank. Wait for the correct password */
 384         readpw(dpy, &rr, locks, nscreens, hash);
 385
 386         return 0;
 387 }