slock.c - slock - simple X display locker utility
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slock.c (9472B)
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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 <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 "util.h"
23
24 char *argv0;
25
26 enum {
27 INIT,
28 INPUT,
29 FAILED,
30 NUMCOLS
31 };
32
33 struct lock {
34 int screen;
35 Window root, win;
36 Pixmap pmap;
37 unsigned long colors[NUMCOLS];
38 };
39
40 struct xrandr {
41 int active;
42 int evbase;
43 int errbase;
44 };
45
46 #include "config.h"
47
48 static void
49 die(const char *errstr, ...)
50 {
51 va_list ap;
52
53 va_start(ap, errstr);
54 vfprintf(stderr, errstr, ap);
55 va_end(ap);
56 exit(1);
57 }
58
59 #ifdef __linux__
60 #include <fcntl.h>
61 #include <linux/oom.h>
62
63 static void
64 dontkillme(void)
65 {
66 FILE *f;
67 const char oomfile[] = "/proc/self/oom_score_adj";
68
69 if (!(f = fopen(oomfile, "w"))) {
70 if (errno == ENOENT)
71 return;
72 die("slock: fopen %s: %s\n", oomfile, strerror(errno));
73 }
74 fprintf(f, "%d", OOM_SCORE_ADJ_MIN);
75 if (fclose(f)) {
76 if (errno == EACCES)
77 die("slock: unable to disable OOM killer. "
78 "Make sure to suid or sgid slock.\n");
79 else
80 die("slock: fclose %s: %s\n", oomfile, strerror(errno));
81 }
82 }
83 #endif
84
85 static const char *
86 gethash(void)
87 {
88 const char *hash;
89 struct passwd *pw;
90
91 /* Check if the current user has a password entry */
92 errno = 0;
93 if (!(pw = getpwuid(getuid()))) {
94 if (errno)
95 die("slock: getpwuid: %s\n", strerror(errno));
96 else
97 die("slock: cannot retrieve password entry\n");
98 }
99 hash = pw->pw_passwd;
100
101 #if HAVE_SHADOW_H
102 if (!strcmp(hash, "x")) {
103 struct spwd *sp;
104 if (!(sp = getspnam(pw->pw_name)))
105 die("slock: getspnam: cannot retrieve shadow entry. "
106 "Make sure to suid or sgid slock.\n");
107 hash = sp->sp_pwdp;
108 }
109 #else
110 if (!strcmp(hash, "*")) {
111 #ifdef __OpenBSD__
112 if (!(pw = getpwuid_shadow(getuid())))
113 die("slock: getpwnam_shadow: cannot retrieve shadow entry. "
114 "Make sure to suid or sgid slock.\n");
115 hash = pw->pw_passwd;
116 #else
117 die("slock: getpwuid: cannot retrieve shadow entry. "
118 "Make sure to suid or sgid slock.\n");
119 #endif /* __OpenBSD__ */
120 }
121 #endif /* HAVE_SHADOW_H */
122
123 return hash;
124 }
125
126 static void
127 readpw(Display *dpy, struct xrandr *rr, struct lock **locks, int nscreens,
128 const char *hash)
129 {
130 XRRScreenChangeNotifyEvent *rre;
131 char buf[32], passwd[256], *inputhash;
132 int num, screen, running, failure, oldc;
133 unsigned int len, color;
134 KeySym ksym;
135 XEvent ev;
136
137 len = 0;
138 running = 1;
139 failure = 0;
140 oldc = INIT;
141
142 while (running && !XNextEvent(dpy, &ev)) {
143 if (ev.type == KeyPress) {
144 explicit_bzero(&buf, sizeof(buf));
145 num = XLookupString(&ev.xkey, buf, sizeof(buf), &ksym, 0);
146 if (IsKeypadKey(ksym)) {
147 if (ksym == XK_KP_Enter)
148 ksym = XK_Return;
149 else if (ksym >= XK_KP_0 && ksym <= XK_KP_9)
150 ksym = (ksym - XK_KP_0) + XK_0;
151 }
152 if (IsFunctionKey(ksym) ||
153 IsKeypadKey(ksym) ||
154 IsMiscFunctionKey(ksym) ||
155 IsPFKey(ksym) ||
156 IsPrivateKeypadKey(ksym))
157 continue;
158 switch (ksym) {
159 case XK_Return:
160 passwd[len] = '\0';
161 errno = 0;
162 if (!(inputhash = crypt(passwd, hash)))
163 fprintf(stderr, "slock: crypt: %s\n", strerror(errno));
164 else
165 running = !!strcmp(inputhash, hash);
166 if (running) {
167 XBell(dpy, 100);
168 failure = 1;
169 }
170 explicit_bzero(&passwd, sizeof(passwd));
171 len = 0;
172 break;
173 case XK_Escape:
174 explicit_bzero(&passwd, sizeof(passwd));
175 len = 0;
176 break;
177 case XK_BackSpace:
178 if (len)
179 passwd[--len] = '\0';
180 break;
181 default:
182 if (num && !iscntrl((unsigned char)buf[0]) &&
183 (len + num < sizeof(passwd))) {
184 memcpy(passwd + len, buf, num);
185 len += num;
186 } else if (buf[0] == '\025') { /* ctrl-u clears input */
187 explicit_bzero(&passwd, sizeof(passwd));
188 len = 0;
189 }
190 break;
191 }
192 color = len ? INPUT : ((failure || failonclear) ? FAILED : INIT);
193 if (running && oldc != color) {
194 for (screen = 0; screen < nscreens; screen++) {
195 XSetWindowBackground(dpy,
196 locks[screen]->win,
197 locks[screen]->colors[color]);
198 XClearWindow(dpy, locks[screen]->win);
199 }
200 oldc = color;
201 }
202 } else if (rr->active && ev.type == rr->evbase + RRScreenChangeNotify) {
203 rre = (XRRScreenChangeNotifyEvent*)&ev;
204 for (screen = 0; screen < nscreens; screen++) {
205 if (locks[screen]->win == rre->window) {
206 if (rre->rotation == RR_Rotate_90 ||
207 rre->rotation == RR_Rotate_270)
208 XResizeWindow(dpy, locks[screen]->win,
209 rre->height, rre->width);
210 else
211 XResizeWindow(dpy, locks[screen]->win,
212 rre->width, rre->height);
213 XClearWindow(dpy, locks[screen]->win);
214 break;
215 }
216 }
217 } else {
218 for (screen = 0; screen < nscreens; screen++)
219 XRaiseWindow(dpy, locks[screen]->win);
220 }
221 }
222 }
223
224 static struct lock *
225 lockscreen(Display *dpy, struct xrandr *rr, int screen)
226 {
227 char curs[] = {0, 0, 0, 0, 0, 0, 0, 0};
228 int i, ptgrab, kbgrab;
229 struct lock *lock;
230 XColor color, dummy;
231 XSetWindowAttributes wa;
232 Cursor invisible;
233
234 if (dpy == NULL || screen < 0 || !(lock = malloc(sizeof(struct lock))))
235 return NULL;
236
237 lock->screen = screen;
238 lock->root = RootWindow(dpy, lock->screen);
239
240 for (i = 0; i < NUMCOLS; i++) {
241 XAllocNamedColor(dpy, DefaultColormap(dpy, lock->screen),
242 colorname[i], &color, &dummy);
243 lock->colors[i] = color.pixel;
244 }
245
246 /* init */
247 wa.override_redirect = 1;
248 wa.background_pixel = lock->colors[INIT];
249 lock->win = XCreateWindow(dpy, lock->root, 0, 0,
250 DisplayWidth(dpy, lock->screen),
251 DisplayHeight(dpy, lock->screen),
252 0, DefaultDepth(dpy, lock->screen),
253 CopyFromParent,
254 DefaultVisual(dpy, lock->screen),
255 CWOverrideRedirect | CWBackPixel, &wa);
256 lock->pmap = XCreateBitmapFromData(dpy, lock->win, curs, 8, 8);
257 invisible = XCreatePixmapCursor(dpy, lock->pmap, lock->pmap,
258 &color, &color, 0, 0);
259 XDefineCursor(dpy, lock->win, invisible);
260
261 /* Try to grab mouse pointer *and* keyboard for 600ms, else fail the lock */
262 for (i = 0, ptgrab = kbgrab = -1; i < 6; i++) {
263 if (ptgrab != GrabSuccess) {
264 ptgrab = XGrabPointer(dpy, lock->root, False,
265 ButtonPressMask | ButtonReleaseMask |
266 PointerMotionMask, GrabModeAsync,
267 GrabModeAsync, None, invisible, CurrentTime);
268 }
269 if (kbgrab != GrabSuccess) {
270 kbgrab = XGrabKeyboard(dpy, lock->root, True,
271 GrabModeAsync, GrabModeAsync, CurrentTime);
272 }
273
274 /* input is grabbed: we can lock the screen */
275 if (ptgrab == GrabSuccess && kbgrab == GrabSuccess) {
276 XMapRaised(dpy, lock->win);
277 if (rr->active)
278 XRRSelectInput(dpy, lock->win, RRScreenChangeNotifyMask);
279
280 XSelectInput(dpy, lock->root, SubstructureNotifyMask);
281 return lock;
282 }
283
284 /* retry on AlreadyGrabbed but fail on other errors */
285 if ((ptgrab != AlreadyGrabbed && ptgrab != GrabSuccess) ||
286 (kbgrab != AlreadyGrabbed && kbgrab != GrabSuccess))
287 break;
288
289 usleep(100000);
290 }
291
292 /* we couldn't grab all input: fail out */
293 if (ptgrab != GrabSuccess)
294 fprintf(stderr, "slock: unable to grab mouse pointer for screen %d\n",
295 screen);
296 if (kbgrab != GrabSuccess)
297 fprintf(stderr, "slock: unable to grab keyboard for screen %d\n",
298 screen);
299 return NULL;
300 }
301
302 static void
303 usage(void)
304 {
305 die("usage: slock [-v]\n");
306 }
307
308 int
309 main(int argc, char **argv) {
310 struct xrandr rr;
311 struct lock **locks;
312 struct passwd *pwd;
313 struct group *grp;
314 uid_t duid;
315 gid_t dgid;
316 const char *hash;
317 Display *dpy;
318 int s, nlocks, nscreens;
319
320 if (argc > 1 && !strcmp(argv[1], "-v")) {
321 puts("slock-"VERSION);
322 return 0;
323 } else if (argc > 1) {
324 usage();
325 }
326
327 /* validate drop-user and -group */
328 errno = 0;
329 if (!(pwd = getpwnam(user)))
330 die("slock: getpwnam %s: %s\n", user,
331 errno ? strerror(errno) : "user entry not found");
332 duid = pwd->pw_uid;
333 errno = 0;
334 if (!(grp = getgrnam(group)))
335 die("slock: getgrnam %s: %s\n", group,
336 errno ? strerror(errno) : "group entry not found");
337 dgid = grp->gr_gid;
338
339 #ifdef __linux__
340 dontkillme();
341 #endif
342
343 hash = gethash();
344 errno = 0;
345 if (!crypt("", hash))
346 die("slock: crypt: %s\n", strerror(errno));
347
348 if (!(dpy = XOpenDisplay(NULL)))
349 die("slock: cannot open display\n");
350
351 /* drop privileges */
352 if (setgroups(0, NULL) < 0)
353 die("slock: setgroups: %s\n", strerror(errno));
354 if (setgid(dgid) < 0)
355 die("slock: setgid: %s\n", strerror(errno));
356 if (setuid(duid) < 0)
357 die("slock: setuid: %s\n", strerror(errno));
358
359 /* check for Xrandr support */
360 rr.active = XRRQueryExtension(dpy, &rr.evbase, &rr.errbase);
361
362 /* get number of screens in display "dpy" and blank them */
363 nscreens = ScreenCount(dpy);
364 if (!(locks = calloc(nscreens, sizeof(struct lock *))))
365 die("slock: out of memory\n");
366 for (nlocks = 0, s = 0; s < nscreens; s++) {
367 if ((locks[s] = lockscreen(dpy, &rr, s)) != NULL)
368 nlocks++;
369 else
370 break;
371 }
372 XSync(dpy, 0);
373
374 /* did we manage to lock everything? */
375 if (nlocks != nscreens)
376 return 1;
377
378 /* everything is now blank. Wait for the correct password */
379 readpw(dpy, &rr, locks, nscreens, hash);
380
381 return 0;
382 }