slock.c - slock - simple X display locker utility
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slock.c (9755B)
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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 <spawn.h>
17 #include <sys/types.h>
18 #include <X11/extensions/Xrandr.h>
19 #include <X11/keysym.h>
20 #include <X11/Xlib.h>
21 #include <X11/Xutil.h>
22
23 #include "arg.h"
24 #include "util.h"
25
26 char *argv0;
27
28 enum {
29 INIT,
30 INPUT,
31 FAILED,
32 NUMCOLS
33 };
34
35 struct lock {
36 int screen;
37 Window root, win;
38 Pixmap pmap;
39 unsigned long colors[NUMCOLS];
40 };
41
42 struct xrandr {
43 int active;
44 int evbase;
45 int errbase;
46 };
47
48 #include "config.h"
49
50 static void
51 die(const char *errstr, ...)
52 {
53 va_list ap;
54
55 va_start(ap, errstr);
56 vfprintf(stderr, errstr, ap);
57 va_end(ap);
58 exit(1);
59 }
60
61 #ifdef __linux__
62 #include <fcntl.h>
63 #include <linux/oom.h>
64
65 static void
66 dontkillme(void)
67 {
68 FILE *f;
69 const char oomfile[] = "/proc/self/oom_score_adj";
70
71 if (!(f = fopen(oomfile, "w"))) {
72 if (errno == ENOENT)
73 return;
74 die("slock: fopen %s: %s\n", oomfile, strerror(errno));
75 }
76 fprintf(f, "%d", OOM_SCORE_ADJ_MIN);
77 if (fclose(f)) {
78 if (errno == EACCES)
79 die("slock: unable to disable OOM killer. "
80 "Make sure to suid or sgid slock.\n");
81 else
82 die("slock: fclose %s: %s\n", oomfile, 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 (!strcmp(hash, "x")) {
105 struct spwd *sp;
106 if (!(sp = getspnam(pw->pw_name)))
107 die("slock: getspnam: cannot retrieve shadow entry. "
108 "Make sure to suid or sgid slock.\n");
109 hash = sp->sp_pwdp;
110 }
111 #else
112 if (!strcmp(hash, "*")) {
113 #ifdef __OpenBSD__
114 if (!(pw = getpwuid_shadow(getuid())))
115 die("slock: getpwnam_shadow: cannot retrieve shadow entry. "
116 "Make sure to suid or sgid slock.\n");
117 hash = pw->pw_passwd;
118 #else
119 die("slock: getpwuid: cannot retrieve shadow entry. "
120 "Make sure to suid or sgid slock.\n");
121 #endif /* __OpenBSD__ */
122 }
123 #endif /* HAVE_SHADOW_H */
124
125 return hash;
126 }
127
128 static void
129 readpw(Display *dpy, struct xrandr *rr, struct lock **locks, int nscreens,
130 const char *hash)
131 {
132 XRRScreenChangeNotifyEvent *rre;
133 char buf[32], passwd[256], *inputhash;
134 int num, screen, running, failure, oldc;
135 unsigned int len, color;
136 KeySym ksym;
137 XEvent ev;
138
139 len = 0;
140 running = 1;
141 failure = 0;
142 oldc = INIT;
143
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 = 1;
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]) &&
185 (len + num < sizeof(passwd))) {
186 memcpy(passwd + len, buf, num);
187 len += num;
188 } else if (buf[0] == '\025') { /* ctrl-u clears input */
189 explicit_bzero(&passwd, sizeof(passwd));
190 len = 0;
191 }
192 break;
193 }
194 color = len ? INPUT : ((failure || failonclear) ? FAILED : INIT);
195 if (running && oldc != color) {
196 for (screen = 0; screen < nscreens; screen++) {
197 XSetWindowBackground(dpy,
198 locks[screen]->win,
199 locks[screen]->colors[color]);
200 XClearWindow(dpy, locks[screen]->win);
201 }
202 oldc = color;
203 }
204 } else if (rr->active && ev.type == rr->evbase + RRScreenChangeNotify) {
205 rre = (XRRScreenChangeNotifyEvent*)&ev;
206 for (screen = 0; screen < nscreens; screen++) {
207 if (locks[screen]->win == rre->window) {
208 if (rre->rotation == RR_Rotate_90 ||
209 rre->rotation == RR_Rotate_270)
210 XResizeWindow(dpy, locks[screen]->win,
211 rre->height, rre->width);
212 else
213 XResizeWindow(dpy, locks[screen]->win,
214 rre->width, rre->height);
215 XClearWindow(dpy, locks[screen]->win);
216 break;
217 }
218 }
219 } else {
220 for (screen = 0; screen < nscreens; screen++)
221 XRaiseWindow(dpy, locks[screen]->win);
222 }
223 }
224 }
225
226 static struct lock *
227 lockscreen(Display *dpy, struct xrandr *rr, int screen)
228 {
229 char curs[] = {0, 0, 0, 0, 0, 0, 0, 0};
230 int i, ptgrab, kbgrab;
231 struct lock *lock;
232 XColor color, dummy;
233 XSetWindowAttributes wa;
234 Cursor invisible;
235
236 if (dpy == NULL || screen < 0 || !(lock = malloc(sizeof(struct lock))))
237 return NULL;
238
239 lock->screen = screen;
240 lock->root = RootWindow(dpy, lock->screen);
241
242 for (i = 0; i < NUMCOLS; i++) {
243 XAllocNamedColor(dpy, DefaultColormap(dpy, lock->screen),
244 colorname[i], &color, &dummy);
245 lock->colors[i] = color.pixel;
246 }
247
248 /* init */
249 wa.override_redirect = 1;
250 wa.background_pixel = lock->colors[INIT];
251 lock->win = XCreateWindow(dpy, lock->root, 0, 0,
252 DisplayWidth(dpy, lock->screen),
253 DisplayHeight(dpy, lock->screen),
254 0, DefaultDepth(dpy, lock->screen),
255 CopyFromParent,
256 DefaultVisual(dpy, lock->screen),
257 CWOverrideRedirect | CWBackPixel, &wa);
258 lock->pmap = XCreateBitmapFromData(dpy, lock->win, curs, 8, 8);
259 invisible = XCreatePixmapCursor(dpy, lock->pmap, lock->pmap,
260 &color, &color, 0, 0);
261 XDefineCursor(dpy, lock->win, invisible);
262
263 /* Try to grab mouse pointer *and* keyboard for 600ms, else fail the lock */
264 for (i = 0, ptgrab = kbgrab = -1; i < 6; i++) {
265 if (ptgrab != GrabSuccess) {
266 ptgrab = XGrabPointer(dpy, lock->root, False,
267 ButtonPressMask | ButtonReleaseMask |
268 PointerMotionMask, GrabModeAsync,
269 GrabModeAsync, None, invisible, CurrentTime);
270 }
271 if (kbgrab != GrabSuccess) {
272 kbgrab = XGrabKeyboard(dpy, lock->root, True,
273 GrabModeAsync, GrabModeAsync, CurrentTime);
274 }
275
276 /* input is grabbed: we can lock the screen */
277 if (ptgrab == GrabSuccess && kbgrab == GrabSuccess) {
278 XMapRaised(dpy, lock->win);
279 if (rr->active)
280 XRRSelectInput(dpy, lock->win, RRScreenChangeNotifyMask);
281
282 XSelectInput(dpy, lock->root, SubstructureNotifyMask);
283 return lock;
284 }
285
286 /* retry on AlreadyGrabbed but fail on other errors */
287 if ((ptgrab != AlreadyGrabbed && ptgrab != GrabSuccess) ||
288 (kbgrab != AlreadyGrabbed && kbgrab != GrabSuccess))
289 break;
290
291 usleep(100000);
292 }
293
294 /* we couldn't grab all input: fail out */
295 if (ptgrab != GrabSuccess)
296 fprintf(stderr, "slock: unable to grab mouse pointer for screen %d\n",
297 screen);
298 if (kbgrab != GrabSuccess)
299 fprintf(stderr, "slock: unable to grab keyboard for screen %d\n",
300 screen);
301 return NULL;
302 }
303
304 static void
305 usage(void)
306 {
307 die("usage: slock [-v] [cmd [arg ...]]\n");
308 }
309
310 int
311 main(int argc, char **argv) {
312 struct xrandr rr;
313 struct lock **locks;
314 struct passwd *pwd;
315 struct group *grp;
316 uid_t duid;
317 gid_t dgid;
318 const char *hash;
319 Display *dpy;
320 int s, nlocks, nscreens;
321
322 ARGBEGIN {
323 case 'v':
324 puts("slock-"VERSION);
325 return 0;
326 default:
327 usage();
328 } ARGEND
329
330 /* validate drop-user and -group */
331 errno = 0;
332 if (!(pwd = getpwnam(user)))
333 die("slock: getpwnam %s: %s\n", user,
334 errno ? strerror(errno) : "user entry not found");
335 duid = pwd->pw_uid;
336 errno = 0;
337 if (!(grp = getgrnam(group)))
338 die("slock: getgrnam %s: %s\n", group,
339 errno ? strerror(errno) : "group entry not found");
340 dgid = grp->gr_gid;
341
342 #ifdef __linux__
343 dontkillme();
344 #endif
345
346 hash = gethash();
347 errno = 0;
348 if (!crypt("", hash))
349 die("slock: crypt: %s\n", strerror(errno));
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.active = XRRQueryExtension(dpy, &rr.evbase, &rr.errbase);
364
365 /* get number of screens in display "dpy" and blank them */
366 nscreens = ScreenCount(dpy);
367 if (!(locks = calloc(nscreens, sizeof(struct lock *))))
368 die("slock: out of memory\n");
369 for (nlocks = 0, s = 0; s < nscreens; s++) {
370 if ((locks[s] = lockscreen(dpy, &rr, s)) != NULL)
371 nlocks++;
372 else
373 break;
374 }
375 XSync(dpy, 0);
376
377 /* did we manage to lock everything? */
378 if (nlocks != nscreens)
379 return 1;
380
381 /* run post-lock command */
382 if (argc > 0) {
383 pid_t pid;
384 extern char **environ;
385 int err = posix_spawnp(&pid, argv[0], NULL, NULL, argv, environ);
386 if (err) {
387 die("slock: failed to execute post-lock command: %s: %s\n",
388 argv[0], strerror(err));
389 }
390 }
391
392 /* everything is now blank. Wait for the correct password */
393 readpw(dpy, &rr, locks, nscreens, hash);
394
395 return 0;
396 }