Don't allow "rm -rf /"

Patch from Theo Buehler who was inspired by watching Bryan Cantrill
in BSD Now 103.

Minor tweak from me to turn the complained variables into flags instead
of counters.

"i think it's ok" tedu@
"this isn't 1980 anymore" deraadt@
ok millert@

1 files changed, 22 insertions, 12 deletions

diff --git a/bin/rm/rm.c b/bin/rm/rm.c
index 49ed97e2345..e5e339e9dab 100644
--- a/bin/rm/rm.c
+++ b/bin/rm/rm.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rm.c,v 1.32 2015/10/09 01:37:06 deraadt Exp $	*/
+/*	$OpenBSD: rm.c,v 1.33 2015/10/11 03:08:46 daniel Exp $	*/
 /*	$NetBSD: rm.c,v 1.19 1995/09/07 06:48:50 jtc Exp $	*/
 
 /*-
@@ -54,7 +54,7 @@ extern char *__progname;
 int dflag, eval, fflag, iflag, Pflag, stdin_ok;
 
 int	check(char *, char *, struct stat *);
-void	checkdot(char **);
+void	checkdotorslash(char **);
 void	rm_file(char **);
 int	rm_overwrite(char *, struct stat *);
 int	pass(int, off_t, char *, size_t);
@@ -113,7 +113,7 @@ main(int argc, char *argv[])
 	if (argc < 1 && fflag == 0)
 		usage();
 
-	checkdot(argv);
+	checkdotorslash(argv);
 
 	if (*argv) {
 		stdin_ok = isatty(STDIN_FILENO);
@@ -391,12 +391,12 @@ check(char *path, char *name, struct stat *sp)
  */
 #define ISDOT(a)	((a)[0] == '.' && (!(a)[1] || ((a)[1] == '.' && !(a)[2])))
 void
-checkdot(char **argv)
+checkdotorslash(char **argv)
 {
 	char *p, **save, **t;
-	int complained;
+	int dotcomplained, slashcomplained;
 
-	complained = 0;
+	dotcomplained = slashcomplained = 0;
 	for (t = argv; *t;) {
 		/* strip trailing slashes */
 		p = strrchr (*t, '\0');
@@ -410,14 +410,24 @@ checkdot(char **argv)
 			p = *t;
 
 		if (ISDOT(p)) {
-			if (!complained++)
+			if (!dotcomplained) {
+				dotcomplained = 1;
 				warnx("\".\" and \"..\" may not be removed");
-			eval = 1;
-			for (save = t; (t[0] = t[1]) != NULL; ++t)
-				continue;
-			t = save;
-		} else
+			}
+		} else if (*p == '\0') {
+			if (!slashcomplained) {
+				slashcomplained = 1;
+				warnx("\"/\" may not be removed");
+			}
+		} else {
 			++t;
+			continue;
+		}
+
+		eval = 1;
+		for (save = t; (t[0] = t[1]) != NULL; ++t)
+			continue;
+		t = save;
 	}
 }