applied Vincent's path with some modifications

diff --git a/slock.c b/slock.c
index 164a464d2174a73b627dc87527a2db77ba9e879b..6541b7046cc5c7a50a5c6bda7ef7581e616eec38 100644 (file)
--- a/slock.c
+++ b/slock.c
@@ -3,32 +3,55 @@
  */
 #define _XOPEN_SOURCE 500
 
-#if HAVE_SHADOW_H
-#include <shadow.h>
-#else
-#include <pwd.h>
-#endif
-
 #include <ctype.h>
+#include <pwd.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
+#if HAVE_SHADOW_H
+#include <shadow.h>
+#endif
 #include <sys/types.h>
 #include <X11/keysym.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 
+const char *
+get_password() { /* only run as root */
+       const char *rval;
+       struct passwd *pw;
+
+       if(geteuid() != 0) {
+               fputs("slock: cannot retrieve password entry (make sure to suid slock)\n", stderr);
+               exit(EXIT_FAILURE);
+       }
+       pw = getpwuid(getuid());
+       endpwent();
+       rval =  pw->pw_passwd;
+
+#if HAVE_SHADOW_H
+       {
+               struct spwd *sp;
+               sp = getspnam(getenv("USER"));
+               endspent();
+               rval = sp->sp_pwdp;
+       }
+#endif
+       /* drop privileges */
+       if(setgid(pw->pw_gid) < 0 || setuid(pw->pw_uid) < 0) {
+               fputs("slock: cannot drop privileges\n",stdout);
+               exit(EXIT_FAILURE);
+       }
+       return rval;
+}
+
 int
 main(int argc, char **argv) {
        char curs[] = {0, 0, 0, 0, 0, 0, 0, 0};
        char buf[32], passwd[256];
        int num, screen;
-#if HAVE_SHADOW_H
-       struct spwd *sp;
-#else
-       struct passwd *pw;
-#endif
+       const char *pws;
        unsigned int len;
        Bool running = True;
        Cursor invisible;
@@ -44,17 +67,7 @@ main(int argc, char **argv) {
                fputs("slock-"VERSION", (C)opyright MMVI Anselm R. Garbe\n", stdout);
                exit(EXIT_SUCCESS);
        }
-       if(geteuid() != 0) {
-               fputs("slock: cannot retrieve password entry (make sure to suid slock)\n", stderr);
-               exit(EXIT_FAILURE);
-       }
-#if HAVE_SHADOW_H
-       sp = getspnam(getenv("USER"));
-       endspent();
-#else
-       pw = getpwuid(getuid());
-       endpwent();
-#endif
+       pws = get_password();
        if(!(dpy = XOpenDisplay(0))) {
                fputs("slock: cannot open display\n", stderr);
                exit(EXIT_FAILURE);
@@ -62,7 +75,7 @@ main(int argc, char **argv) {
        screen = DefaultScreen(dpy);
 
        /* init */
-       passwd[0] = 0;
+       len = 0;
 
        wa.override_redirect = 1;
        wa.background_pixel = BlackPixel(dpy, screen);
@@ -89,7 +102,6 @@ main(int argc, char **argv) {
        /* main event loop */
        while(running && !XNextEvent(dpy, &ev))
                if(ev.type == KeyPress) {
-                       len = strlen(passwd);
                        buf[0] = 0;
                        num = XLookupString(&ev.xkey, buf, sizeof(buf), &ksym, 0);
                        if(IsFunctionKey(ksym) || IsKeypadKey(ksym)
@@ -98,28 +110,22 @@ main(int argc, char **argv) {
                                continue;
                        switch(ksym) {
                        case XK_Return:
-#if HAVE_SHADOW_H
-                               if((running = strncmp(crypt(passwd, sp->sp_pwdp), sp->sp_pwdp, sizeof(passwd))))
-#else
-                               if((running = strncmp(crypt(passwd, pw->pw_passwd), pw->pw_passwd, sizeof(passwd))))
-#endif
+                               passwd[len] = 0;
+                               if((running = strcmp(crypt(passwd, pws), pws)) != 0)
                                        XBell(dpy, 100);
-                               passwd[0] = 0;
+                               len = 0;
                                break;
                        case XK_Escape:
-                               passwd[0] = 0;
+                               len = 0;
                                break;
                        case XK_BackSpace:
                                if(len)
-                                       passwd[--len] = 0;
+                                 --len;
                                break;
                        default:
                                if(num && !iscntrl((int) buf[0])) {
-                                       buf[num] = 0;
-                                       if(len)
-                                               strncat(passwd, buf, sizeof(passwd));
-                                       else
-                                               strncpy(passwd, buf, sizeof(passwd));
+                                       memcpy(passwd + len,buf,num);
+                                       len += num;
                                }
                                break;
                        }