Prevent negative array index accesses when strlen(buff) == 0.

OK joris@

1 files changed, 10 insertions, 8 deletions

diff --git a/usr.bin/rcs/date.y b/usr.bin/rcs/date.y
index e5ed23c0180..5e08849ed0d 100644
--- a/usr.bin/rcs/date.y
+++ b/usr.bin/rcs/date.y
@@ -1,5 +1,5 @@
 %{
-/*	$OpenBSD: date.y,v 1.4 2006/05/17 20:38:05 xsa Exp $	*/
+/*	$OpenBSD: date.y,v 1.5 2007/01/20 06:57:54 ray Exp $	*/
 
 /*
 **  Originally written by Steven M. Bellovin <smb@research.att.com> while
@@ -628,6 +628,7 @@ RelativeMonth(time_t Start, time_t RelMonth)
 static int
 lookup(char *buff)
 {
+	size_t		len;
 	char		*p, *q;
 	int		i, abbrev;
 	const TABLE	*tp;
@@ -646,12 +647,14 @@ lookup(char *buff)
 		return (tMERIDIAN);
 	}
 
+	len = strlen(buff);
 	/* See if we have an abbreviation for a month. */
-	if (strlen(buff) == 3)
+	if (len == 3)
 		abbrev = 1;
-	else if (strlen(buff) == 4 && buff[3] == '.') {
+	else if (len == 4 && buff[3] == '.') {
 		abbrev = 1;
 		buff[3] = '\0';
+		--len;
 	} else
 		abbrev = 0;
 
@@ -683,15 +686,14 @@ lookup(char *buff)
 		}
 
 	/* Strip off any plural and try the units table again. */
-	i = strlen(buff) - 1;
-	if (buff[i] == 's') {
-		buff[i] = '\0';
+	if (len != 0 && buff[len - 1] == 's') {
+		buff[len - 1] = '\0';
 		for (tp = UnitsTable; tp->name; tp++)
 			if (strcmp(buff, tp->name) == 0) {
 				yylval.Number = tp->value;
 				return (tp->type);
 			}
-		buff[i] = 's';	/* Put back for "this" in OtherTable. */
+		buff[len - 1] = 's';	/* Put back for "this" in OtherTable. */
 	}
 
 	for (tp = OtherTable; tp->name; tp++)
@@ -701,7 +703,7 @@ lookup(char *buff)
 		}
 
 	/* Military timezones. */
-	if (buff[1] == '\0' && isalpha(*buff)) {
+	if (len == 1 && isalpha(*buff)) {
 		for (tp = MilitaryTable; tp->name; tp++)
 			if (strcmp(buff, tp->name) == 0) {
 				yylval.Number = tp->value;