File nethack-secure.patch of Package nethack-367

Index: util/recover.c
===================================================================
--- util/recover.c.orig
+++ util/recover.c
@@ -17,6 +17,12 @@
 #include <fcntl.h>
 #endif
 
+#ifdef SECURE
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#endif
+
 #ifdef VMS
 extern int FDECL(vms_creat, (const char *, unsigned));
 extern int FDECL(vms_open, (const char *, int, unsigned));
@@ -112,15 +118,23 @@ char *argv[];
     }
 #if defined(SECURE) && !defined(VMS)
     if (dir
-#ifdef HACKDIR
+# ifdef VAR_PLAYGROUND
+	        && strcmp(dir, VAR_PLAYGROUND)
+# else
+#  ifdef HACKDIR
         && strcmp(dir, HACKDIR)
-#endif
+#  endif 
+# endif /* VAR_PLAYGROUND */
             ) {
         (void) setgid(getgid());
         (void) setuid(getuid());
     }
 #endif /* SECURE && !VMS */
 
+#ifdef VAR_PLAYGROUND
+	if (!dir) dir = VAR_PLAYGROUND;
+#endif
+
 #ifdef HACKDIR
     if (!dir)
         dir = HACKDIR;
@@ -166,11 +180,19 @@ int lev;
 #endif
 }
 
+#ifdef SECURE
+static uid_t save_uid = -1;
+#endif
+
 int
 open_levelfile(lev)
 int lev;
 {
     int fd;
+#ifdef SECURE
+	struct stat level_stat;
+	uid_t uid;
+#endif
 
     set_levelfile_name(lev);
 #if defined(MICRO) || defined(WIN32) || defined(MSDOS)
@@ -178,6 +200,21 @@ int lev;
 #else
     fd = open(lock, O_RDONLY, 0);
 #endif
+	/* Security check: does the user calling recover own the file? */
+#ifdef SECURE
+	if (fd != -1) {
+		uid = getuid();
+		if (fstat(fd, &level_stat) == -1) {
+			Fprintf(stderr, "No permission to stat level file %s.\n", lock);
+			return -1;
+		}
+		if (uid != 0 && level_stat.st_uid != uid) {
+			Fprintf(stderr, "You are not the owner of level file %s.\n", lock);
+			return -1;
+		}
+		save_uid = level_stat.st_uid;
+	}
+#endif
     return fd;
 }
 
@@ -191,6 +228,13 @@ create_savefile()
 #else
     fd = creat(savename, FCMASK);
 #endif
+
+#ifdef SECURE
+	if (fchown(fd, save_uid, -1) == -1) {
+		Fprintf(stderr, "could not chown %s to %i!\n", savename, 
+			save_uid);
+	}
+#endif
     return fd;
 }