From 23677e98fe628331f7eb20a472bb7005f0ce7087 Mon Sep 17 00:00:00 2001
From: Bill Paul <wpaul@FreeBSD.org>
Date: Tue, 30 Sep 1997 18:08:11 +0000
Subject: [PATCH] Putting records with zero-length keys into a Berkeley DB hash
 database is asking for trouble (sequential database enumerations can get
 caught in an infinite loop). The yp_mkdb(8) utility avoids putting such
 records into a database, but ypxfr does not. Today I got bit by a NULL entry
 in one of the amd maps on my network, which is served by a SunOS master. The
 map was transfered successfully to my FreeBSD slave, but attempting to dump
 it with ypcat(1) caused ypserv(8) to transmit the same record over and over
 again, making the map appear to be infinitely large. I finally noticed the
 problem while testing a new version of amd under development at the Columbia
 CS department, which began gobbling up insane amounts of memory while trying
 to swallow the map.

To deal with this problem, I'm modifying ypxfr to watch for records
with zero-length keys and turn them into something less destructive
before writing them to the database.
---
 libexec/ypxfr/ypxfr_main.c | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/libexec/ypxfr/ypxfr_main.c b/libexec/ypxfr/ypxfr_main.c
index 6e42c05ae93..1c905cca367 100644
--- a/libexec/ypxfr/ypxfr_main.c
+++ b/libexec/ypxfr/ypxfr_main.c
@@ -29,7 +29,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: ypxfr_main.c,v 1.8 1997/02/22 14:22:48 peter Exp $
+ *	$Id: ypxfr_main.c,v 1.9 1997/03/28 15:48:21 imp Exp $
  */
 #include <stdio.h>
 #include <stdlib.h>
@@ -51,7 +51,7 @@ struct dom_binding {};
 #include "ypxfr_extern.h"
 
 #ifndef lint
-static const char rcsid[] = "$Id: ypxfr_main.c,v 1.8 1997/02/22 14:22:48 peter Exp $";
+static const char rcsid[] = "$Id: ypxfr_main.c,v 1.9 1997/03/28 15:48:21 imp Exp $";
 #endif
 
 char *progname = "ypxfr";
@@ -133,10 +133,26 @@ int ypxfr_foreach(status, key, keylen, val, vallen, data)
 	if (status != YP_TRUE)
 		return (status);
 
-	dbkey.data = key;
-	dbkey.size = keylen;
-	dbval.data = val;
-	dbval.size = vallen;
+	/*
+	 * XXX Do not attempt to write zero-length keys or
+	 * data into a Berkeley DB hash database. It causes a
+	 * strange failure mode where sequential searches get
+	 * caught in an infinite loop.
+	 */
+	if (keylen) {
+		dbkey.data = key;
+		dbkey.size = keylen;
+	} else {
+		dbkey.data = "";
+		dbkey.size = 1;
+	}
+	if (vallen) {
+		dbval.data = val;
+		dbval.size = vallen;
+	} else {
+		dbval.data = "";
+		dbval.size = 1;
+	}
 
 	if (yp_put_record(dbp, &dbkey, &dbval, 0) != YP_TRUE)
 		return(yp_errno);