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Ensure Polyphemus-Mitigation and properly drop privileges
[slock.git] / slock.c
diff --git a/slock.c b/slock.c
index 2dce109..7127ebe 100644 (file)
--- a/slock.c
+++ b/slock.c
@@ -6,6 +6,7 @@
 
 #include <ctype.h>
 #include <errno.h>
 
 #include <ctype.h>
 #include <errno.h>
+#include <grp.h>
 #include <pwd.h>
 #include <stdarg.h>
 #include <stdlib.h>
 #include <pwd.h>
 #include <stdarg.h>
 #include <stdlib.h>
@@ -13,262 +14,395 @@
 #include <string.h>
 #include <unistd.h>
 #include <sys/types.h>
 #include <string.h>
 #include <unistd.h>
 #include <sys/types.h>
+#include <X11/extensions/Xrandr.h>
 #include <X11/keysym.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 
 #include <X11/keysym.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 
-#if HAVE_BSD_AUTH
-#include <login_cap.h>
-#include <bsd_auth.h>
-#endif
+#include "arg.h"
+#include "util.h"
+
+char *argv0;
+
+enum {
+       INIT,
+       INPUT,
+       FAILED,
+       NUMCOLS
+};
+
+#include "config.h"
 
 
-struct st_lock {
+typedef struct {
        int screen;
        int screen;
-       Window root, w;
+       Window root, win;
        Pixmap pmap;
        Pixmap pmap;
-};
+       unsigned long colors[NUMCOLS];
+} Lock;
 
 
-extern const char *__progname;
+static Lock **locks;
+static int nscreens;
+static Bool rr;
+static int rrevbase;
+static int rrerrbase;
 
 static void
 
 static void
-die(const char *errstr, ...) {
+die(const char *errstr, ...)
+{
        va_list ap;
 
        va_list ap;
 
-       fprintf(stderr, "%s: ", __progname);
        va_start(ap, errstr);
        vfprintf(stderr, errstr, ap);
        va_end(ap);
        va_start(ap, errstr);
        vfprintf(stderr, errstr, ap);
        va_end(ap);
-       fprintf(stderr, "\n");
-       fflush(stderr);
+       exit(1);
+}
+
+#ifdef __linux__
+#include <fcntl.h>
+#include <linux/oom.h>
+
+static void
+dontkillme(void)
+{
+       FILE *f;
+       const char oomfile[] = "/proc/self/oom_score_adj";
 
 
-       exit(EXIT_FAILURE);
+       if (!(f = fopen(oomfile, "w"))) {
+               if (errno == ENOENT)
+                       return;
+               die("slock: fopen %s: %s\n", oomfile, strerror(errno));
+       }
+       fprintf(f, "%d", OOM_SCORE_ADJ_MIN);
+       if (fclose(f)) {
+               if (errno == EACCES)
+                       die("slock: unable to disable OOM killer. "
+                           "suid or sgid set?\n");
+               else
+                       die("slock: fclose %s: %s\n", oomfile,
+                           strerror(errno));
+       }
 }
 }
+#endif
 
 
-#ifndef HAVE_BSD_AUTH
 static const char *
 static const char *
-getpw(void) { /* only run as root */
+getpw(void)
+{
        const char *rval;
        struct passwd *pw;
 
        const char *rval;
        struct passwd *pw;
 
-       if(geteuid() != 0)
-               die("cannot retrieve password entry (make sure to suid slock)");
-       pw = getpwuid(getuid());
-       endpwent();
-       rval =  pw->pw_passwd;
+       /* Check if the current user has a password entry */
+       errno = 0;
+       if (!(pw = getpwuid(getuid()))) {
+               if (errno)
+                       die("slock: getpwuid: %s\n", strerror(errno));
+               else
+                       die("slock: cannot retrieve password entry\n");
+       }
+       rval = pw->pw_passwd;
 
 #if HAVE_SHADOW_H
 
 #if HAVE_SHADOW_H
-       {
+       if (rval[0] == 'x' && rval[1] == '\0') {
                struct spwd *sp;
                struct spwd *sp;
-               sp = getspnam(getenv("USER"));
-               endspent();
+               if (!(sp = getspnam(getenv("USER"))))
+                       die("slock: getspnam: cannot retrieve shadow entry (make sure to suid or sgid slock)\n");
                rval = sp->sp_pwdp;
        }
                rval = sp->sp_pwdp;
        }
-#endif
+#else
+       if (rval[0] == '*' && rval[1] == '\0') {
+#ifdef __OpenBSD__
+               if (!(pw = getpwnam_shadow(getenv("USER"))))
+                       die("slock: getpwnam_shadow: cannot retrieve shadow entry (make sure to suid or sgid slock)\n");
+               rval = pw->pw_passwd;
+#else
+               die("slock: getpwuid: cannot retrieve shadow entry (make sure to suid or sgid slock)\n");
+#endif /* __OpenBSD__ */
+       }
+#endif /* HAVE_SHADOW_H */
 
 
-       /* drop privileges */
-       if(setgid(pw->pw_gid) < 0 || setuid(pw->pw_uid) < 0)
-               die("cannot drop privileges");
        return rval;
 }
        return rval;
 }
-#endif
 
 static void
 
 static void
-#ifdef HAVE_BSD_AUTH
-readpw(Display *dpy)
-#else
 readpw(Display *dpy, const char *pws)
 readpw(Display *dpy, const char *pws)
-#endif
 {
 {
-       char buf[32], passwd[256];
-       int num;
-
-       unsigned int len;
-       Bool running = True;
+       char buf[32], passwd[256], *encrypted;
+       int num, screen, running, failure;
+       unsigned int len, color;
        KeySym ksym;
        XEvent ev;
        KeySym ksym;
        XEvent ev;
+       static int oldc = INIT;
 
        len = 0;
 
        len = 0;
-       running = True;
+       running = 1;
+       failure = 0;
 
        /* As "slock" stands for "Simple X display locker", the DPMS settings
         * had been removed and you can set it with "xset" or some other
         * utility. This way the user can easily set a customized DPMS
         * timeout. */
 
        /* As "slock" stands for "Simple X display locker", the DPMS settings
         * had been removed and you can set it with "xset" or some other
         * utility. This way the user can easily set a customized DPMS
         * timeout. */
-
-       while(running && !XNextEvent(dpy, &ev)) {
-               if(ev.type == KeyPress) {
-                       buf[0] = 0;
-                       num = XLookupString(&ev.xkey, buf, sizeof buf, &ksym, 0);
-                       if(IsKeypadKey(ksym)) {
-                               if(ksym == XK_KP_Enter)
+       while (running && !XNextEvent(dpy, &ev)) {
+               if (ev.type == KeyPress) {
+                       explicit_bzero(&buf, sizeof(buf));
+                       num = XLookupString(&ev.xkey, buf, sizeof(buf), &ksym, 0);
+                       if (IsKeypadKey(ksym)) {
+                               if (ksym == XK_KP_Enter)
                                        ksym = XK_Return;
                                        ksym = XK_Return;
-                               else if(ksym >= XK_KP_0 && ksym <= XK_KP_9)
+                               else if (ksym >= XK_KP_0 && ksym <= XK_KP_9)
                                        ksym = (ksym - XK_KP_0) + XK_0;
                        }
                                        ksym = (ksym - XK_KP_0) + XK_0;
                        }
-                       if(IsFunctionKey(ksym) || IsKeypadKey(ksym)
-                                       || IsMiscFunctionKey(ksym) || IsPFKey(ksym)
-                                       || IsPrivateKeypadKey(ksym))
+                       if (IsFunctionKey(ksym) ||
+                           IsKeypadKey(ksym) ||
+                           IsMiscFunctionKey(ksym) ||
+                           IsPFKey(ksym) ||
+                           IsPrivateKeypadKey(ksym))
                                continue;
                                continue;
-                       switch(ksym) {
+                       switch (ksym) {
                        case XK_Return:
                                passwd[len] = 0;
                        case XK_Return:
                                passwd[len] = 0;
-#ifdef HAVE_BSD_AUTH
-                               running = !auth_userokay(getlogin(), NULL, "auth-xlock", passwd);
-#else
-                               running = strcmp(crypt(passwd, pws), pws);
-#endif
-                               if (running != 0)
+                               errno = 0;
+                               if (!(encrypted = crypt(passwd, pws)))
+                                       fprintf(stderr, "slock: crypt: %s\n", strerror(errno));
+                               else
+                                       running = !!strcmp(encrypted, pws);
+                               if (running) {
                                        XBell(dpy, 100);
                                        XBell(dpy, 100);
+                                       failure = True;
+                               }
+                               explicit_bzero(&passwd, sizeof(passwd));
                                len = 0;
                                break;
                        case XK_Escape:
                                len = 0;
                                break;
                        case XK_Escape:
+                               explicit_bzero(&passwd, sizeof(passwd));
                                len = 0;
                                break;
                        case XK_BackSpace:
                                len = 0;
                                break;
                        case XK_BackSpace:
-                               if(len)
-                                       --len;
+                               if (len)
+                                       passwd[len--] = 0;
                                break;
                        default:
                                break;
                        default:
-                               if(num && !iscntrl((int) buf[0]) && (len + num < sizeof passwd)) { 
+                               if (num && !iscntrl((int)buf[0]) && (len + num < sizeof(passwd))) {
                                        memcpy(passwd + len, buf, num);
                                        len += num;
                                }
                                break;
                        }
                                        memcpy(passwd + len, buf, num);
                                        len += num;
                                }
                                break;
                        }
-               }
+                       color = len ? INPUT : (failure || failonclear ? FAILED : INIT);
+                       if (running && oldc != color) {
+                               for (screen = 0; screen < nscreens; screen++) {
+                                       XSetWindowBackground(dpy, locks[screen]->win, locks[screen]->colors[color]);
+                                       XClearWindow(dpy, locks[screen]->win);
+                               }
+                               oldc = color;
+                       }
+               } else if (rr && ev.type == rrevbase + RRScreenChangeNotify) {
+                       XRRScreenChangeNotifyEvent *rre = (XRRScreenChangeNotifyEvent*)&ev;
+                       for (screen = 0; screen < nscreens; screen++) {
+                               if (locks[screen]->win == rre->window) {
+                                       XResizeWindow(dpy, locks[screen]->win, rre->width, rre->height);
+                                       XClearWindow(dpy, locks[screen]->win);
+                               }
+                       }
+               } else for (screen = 0; screen < nscreens; screen++)
+                       XRaiseWindow(dpy, locks[screen]->win);
        }
 }
 
 static void
        }
 }
 
 static void
-unlockscreen(Display *dpy, struct st_lock *lock) {
-       if (dpy == NULL || lock == NULL)
+unlockscreen(Display *dpy, Lock *lock)
+{
+       if(dpy == NULL || lock == NULL)
                return;
 
        XUngrabPointer(dpy, CurrentTime);
                return;
 
        XUngrabPointer(dpy, CurrentTime);
+       XUngrabKeyboard(dpy, CurrentTime);
+       XFreeColors(dpy, DefaultColormap(dpy, lock->screen), lock->colors, NUMCOLS, 0);
        XFreePixmap(dpy, lock->pmap);
        XFreePixmap(dpy, lock->pmap);
-       XDestroyWindow(dpy, lock->w);
+       XDestroyWindow(dpy, lock->win);
 
        free(lock);
 }
 
 
        free(lock);
 }
 
-static struct st_lock *
-lockscreen(Display *dpy, int screen) {
+static void
+cleanup(Display *dpy)
+{
+       int s;
+
+       for (s = 0; s < nscreens; ++s)
+               unlockscreen(dpy, locks[s]);
+
+       free(locks);
+       XCloseDisplay(dpy);
+}
+
+static Lock *
+lockscreen(Display *dpy, int screen)
+{
        char curs[] = {0, 0, 0, 0, 0, 0, 0, 0};
        char curs[] = {0, 0, 0, 0, 0, 0, 0, 0};
-       unsigned int len;
-       struct st_lock *lock;
-       Bool running = True;
-       XColor black, dummy;
+       int i, ptgrab, kbgrab;
+       Lock *lock;
+       XColor color, dummy;
        XSetWindowAttributes wa;
        Cursor invisible;
 
        XSetWindowAttributes wa;
        Cursor invisible;
 
-       if (dpy == NULL || screen < 0)
-               return NULL;
-
-       lock = malloc(sizeof(struct st_lock));
-       if (lock == NULL)
+       if (dpy == NULL || screen < 0 || !(lock = malloc(sizeof(Lock))))
                return NULL;
 
        lock->screen = screen;
                return NULL;
 
        lock->screen = screen;
-
        lock->root = RootWindow(dpy, lock->screen);
 
        lock->root = RootWindow(dpy, lock->screen);
 
+       for (i = 0; i < NUMCOLS; i++) {
+               XAllocNamedColor(dpy, DefaultColormap(dpy, lock->screen), colorname[i], &color, &dummy);
+               lock->colors[i] = color.pixel;
+       }
+
        /* init */
        wa.override_redirect = 1;
        /* init */
        wa.override_redirect = 1;
-       wa.background_pixel = BlackPixel(dpy, lock->screen);
-       lock->w = XCreateWindow(dpy, lock->root, 0, 0, DisplayWidth(dpy, lock->screen), DisplayHeight(dpy, lock->screen),
-                       0, DefaultDepth(dpy, lock->screen), CopyFromParent,
-                       DefaultVisual(dpy, lock->screen), CWOverrideRedirect | CWBackPixel, &wa);
-       XAllocNamedColor(dpy, DefaultColormap(dpy, lock->screen), "black", &black, &dummy);
-       lock->pmap = XCreateBitmapFromData(dpy, lock->w, curs, 8, 8);
-       invisible = XCreatePixmapCursor(dpy, lock->pmap, lock->pmap, &black, &black, 0, 0);
-       XDefineCursor(dpy, lock->w, invisible);
-       XMapRaised(dpy, lock->w);
-       for(len = 1000; len; len--) {
-               if(XGrabPointer(dpy, lock->root, False, ButtonPressMask | ButtonReleaseMask | PointerMotionMask,
-                       GrabModeAsync, GrabModeAsync, None, invisible, CurrentTime) == GrabSuccess)
-                       break;
-               usleep(1000);
-       }
-       if((running = running && (len > 0))) {
-               for(len = 1000; len; len--) {
-                       if(XGrabKeyboard(dpy, lock->root, True, GrabModeAsync, GrabModeAsync, CurrentTime)
-                               == GrabSuccess)
-                               break;
-                       usleep(1000);
+       wa.background_pixel = lock->colors[INIT];
+       lock->win = XCreateWindow(dpy, lock->root, 0, 0, DisplayWidth(dpy, lock->screen), DisplayHeight(dpy, lock->screen),
+                                 0, DefaultDepth(dpy, lock->screen), CopyFromParent,
+                                 DefaultVisual(dpy, lock->screen), CWOverrideRedirect | CWBackPixel, &wa);
+       lock->pmap = XCreateBitmapFromData(dpy, lock->win, curs, 8, 8);
+       invisible = XCreatePixmapCursor(dpy, lock->pmap, lock->pmap, &color, &color, 0, 0);
+       XDefineCursor(dpy, lock->win, invisible);
+
+       /* Try to grab mouse pointer *and* keyboard for 600ms, else fail the lock */
+       for (i = 0, ptgrab = kbgrab = -1; i < 6; i++) {
+               if (ptgrab != GrabSuccess) {
+                       ptgrab = XGrabPointer(dpy, lock->root, False,
+                                ButtonPressMask | ButtonReleaseMask |
+                                PointerMotionMask, GrabModeAsync,
+                                GrabModeAsync, None, invisible, CurrentTime);
                }
                }
-               running = (len > 0);
-       }
+               if (kbgrab != GrabSuccess) {
+                       kbgrab = XGrabKeyboard(dpy, lock->root, True,
+                                GrabModeAsync, GrabModeAsync, CurrentTime);
+               }
+
+               /* input is grabbed: we can lock the screen */
+               if (ptgrab == GrabSuccess && kbgrab == GrabSuccess) {
+                       XMapRaised(dpy, lock->win);
+                       if (rr)
+                               XRRSelectInput(dpy, lock->win, RRScreenChangeNotifyMask);
+
+                       XSelectInput(dpy, lock->root, SubstructureNotifyMask);
+                       return lock;
+               }
+
+               /* retry on AlreadyGrabbed but fail on other errors */
+               if ((ptgrab != AlreadyGrabbed && ptgrab != GrabSuccess) ||
+                   (kbgrab != AlreadyGrabbed && kbgrab != GrabSuccess))
+                       break;
 
 
-       if (!running) {
-               unlockscreen(dpy, lock);
-               lock = NULL;
+               usleep(100000);
        }
 
        }
 
-       return lock;
+       /* we couldn't grab all input: fail out */
+       if (ptgrab != GrabSuccess)
+               fprintf(stderr, "slock: unable to grab mouse pointer for screen %d\n", screen);
+       if (kbgrab != GrabSuccess)
+               fprintf(stderr, "slock: unable to grab keyboard for screen %d\n", screen);
+       return NULL;
 }
 
 static void
 }
 
 static void
-usage(void) {
-       fprintf(stderr, "usage: %s -v", __progname);
-       exit(EXIT_FAILURE);
-}
-
-static int
-xerrordummy(Display *dpy, XErrorEvent *ee) {
-       return 0;
+usage(void)
+{
+       die("usage: slock [-v] [cmd [arg ...]]\n");
 }
 
 int
 main(int argc, char **argv) {
 }
 
 int
 main(int argc, char **argv) {
-#ifndef HAVE_BSD_AUTH
+       struct passwd *pwd;
+       struct group *grp;
+       uid_t duid;
+       gid_t dgid;
        const char *pws;
        const char *pws;
-#endif
        Display *dpy;
        Display *dpy;
-       int nscreens, screen;
-
-       struct st_lock **locks;
+       int s, nlocks;
 
 
-       if((argc == 2) && !strcmp("-v", argv[1]))
-               die("slock-%s, © 2006-2012 Anselm R Garbe", VERSION);
-       else if(argc != 1)
+       ARGBEGIN {
+       case 'v':
+               fprintf(stderr, "slock-"VERSION"\n");
+               return 0;
+       default:
                usage();
                usage();
+       } ARGEND
+
+       /* validate drop-user and -group */
+       errno = 0;
+       if (!(pwd = getpwnam(user)))
+               die("slock: getpwnam %s: %s\n", user, errno ?
+                   strerror(errno) : "user entry not found");
+       duid = pwd->pw_uid;
+       errno = 0;
+       if (!(grp = getgrnam(group)))
+               die("slock: getgrnam %s: %s\n", group, errno ?
+                   strerror(errno) : "group entry not found");
+       dgid = grp->gr_gid;
+
+#ifdef __linux__
+       dontkillme();
+#endif
 
 
-       if(!getpwuid(getuid()))
-               die("no passwd entry for you");
-
-#ifndef HAVE_BSD_AUTH
        pws = getpw();
        pws = getpw();
-#endif
+       if (strlen(pws) < 2)
+               die("slock: failed to get user password hash.\n");
 
 
-       if(!(dpy = XOpenDisplay(0)))
-               die("cannot open display");
-       /* prevent default error handler to take over */
-       XSetErrorHandler(xerrordummy);
-       /* Get the number of screens in display "dpy" and blank them all. */
-       nscreens = ScreenCount(dpy);
-       locks = malloc(sizeof(struct st_lock *) * nscreens);
-       if (locks == NULL)
-               die("malloc: %s", strerror(errno));
+       if (!(dpy = XOpenDisplay(NULL)))
+               die("slock: cannot open display\n");
 
 
-       for (screen = 0; screen < nscreens; screen++)
-               locks[screen] = lockscreen(dpy, screen);
+       /* drop privileges */
+       if (setgroups(0, NULL) < 0)
+               die("slock: setgroups: %s\n", strerror(errno));
+       if (setgid(dgid) < 0)
+               die("slock: setgid: %s\n", strerror(errno));
+       if (setuid(duid) < 0)
+               die("slock: setuid: %s\n", strerror(errno));
 
 
-       XSync(dpy, False);
+       /* check for Xrandr support */
+       rr = XRRQueryExtension(dpy, &rrevbase, &rrerrbase);
 
 
-       /* Everything is now blank. Now wait for the correct password. */
-#ifdef HAVE_BSD_AUTH
-       readpw(dpy);
-#else
-       readpw(dpy, pws);
-#endif
+       /* get number of screens in display "dpy" and blank them */
+       nscreens = ScreenCount(dpy);
+       if (!(locks = calloc(nscreens, sizeof(Lock *)))) {
+               XCloseDisplay(dpy);
+               die("slock: out of memory\n");
+       }
+       for (nlocks = 0, s = 0; s < nscreens; s++) {
+               if ((locks[s] = lockscreen(dpy, s)) != NULL)
+                       nlocks++;
+               else
+                       break;
+       }
+       XSync(dpy, 0);
 
 
-       /* Password ok, unlock everything and quit. */
-       for (screen = 0; screen < nscreens; screen++)
-               unlockscreen(dpy, locks[screen]);
+       /* did we manage to lock everything? */
+       if (nlocks != nscreens) {
+               cleanup(dpy);
+               return 1;
+       }
 
 
-       free(locks);
+       /* run post-lock command */
+       if (argc > 0) {
+               switch (fork()) {
+               case -1:
+                       cleanup(dpy);
+                       die("slock: fork failed: %s\n", strerror(errno));
+               case 0:
+                       if (close(ConnectionNumber(dpy)) < 0)
+                               die("slock: close: %s\n", strerror(errno));
+                       execvp(argv[0], argv);
+                       fprintf(stderr, "slock: execvp %s: %s\n", argv[0],
+                               strerror(errno));
+                       _exit(1);
+               }
+       }
 
 
-       XCloseDisplay(dpy);
+       /* everything is now blank. Wait for the correct password */
+       readpw(dpy, pws);
+
+       /* password ok, unlock everything and quit */
+       cleanup(dpy);
 
        return 0;
 }
 
        return 0;
 }