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