applied Vincent's path with some modifications

1 files changed, 43 insertions, 37 deletions

diff --git a/slock.c b/slock.c
index 164a464..6541b70 100644
--- 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;
                         }