Backported for 7.0 by Remi


From 8d3dfabef459fe7815e8ea2fd68753fd17859d7b Mon Sep 17 00:00:00 2001
From: Stanislav Malyshev <stas@php.net>
Date: Sat, 29 Dec 2018 20:39:08 -0800
Subject: [PATCH] Fix #77369 - memcpy with negative length via crafted DNS
 response

---
 ext/standard/dns.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/ext/standard/dns.c b/ext/standard/dns.c
index 8e102f816f6e..b5fbcb96f968 100644
--- a/ext/standard/dns.c
+++ b/ext/standard/dns.c
@@ -459,6 +459,10 @@ static u_char *php_parserr(u_char *cp, u
 	GETLONG(ttl, cp);
 	GETSHORT(dlen, cp);
 	CHECKCP(dlen);
+	if (dlen == 0) {
+		/* No data in the response - nothing to do */
+		return NULL;
+	}
 	if (type_to_fetch != T_ANY && type != type_to_fetch) {
 		cp += dlen;
 		return cp;
@@ -549,7 +553,12 @@ static u_char *php_parserr(u_char *cp, u
 			CHECKCP(n);
 			add_assoc_stringl(subarray, "tag", (char*)cp, n);
 			cp += n;
-			add_assoc_string(subarray, "value", (char*)cp);
+			if ( (size_t) dlen < ((size_t)n) + 2 ) {
+				return NULL;
+			}
+ 			n = dlen - n - 2;
+ 			CHECKCP(n);
+ 			add_assoc_stringl(subarray, "value", (char*)cp, n);
 			break;
 		case DNS_T_TXT:
 			{