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changeset 4278:7263f7c073b4 draft

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dhcp: Clarify range checks in valid UDP packets
author Roy Marples <roy@marples.name>
date Mon, 07 May 2018 15:01:46 +0100
parents 97f2363a60cf
children cdffb0137daa
files src/dhcp.c
diffstat 1 files changed, 7 insertions(+), 1 deletions(-) [+]
line wrap: on
line diff
--- a/src/dhcp.c	Sun May 06 16:50:35 2018 +0100
+++ b/src/dhcp.c	Mon May 07 15:01:46 2018 +0100
@@ -3276,7 +3276,7 @@
 	struct bootp_pkt *p;
 	uint16_t bytes;
 
-	if (data_len < sizeof(p->ip) + sizeof(p->udp)) {
+	if (data_len < sizeof(p->ip)) {
 		if (from)
 			from->s_addr = INADDR_ANY;
 		errno = ERANGE;
@@ -3291,6 +3291,12 @@
 	}
 
 	bytes = ntohs(p->ip.ip_len);
+	/* Check we have a payload */
+	if (bytes <= sizeof(p->ip) + sizeof(p->udp)) {
+		errno = ERANGE;
+		return -1;
+	}
+	/* Check we don't go beyond the payload */
 	if (bytes > data_len) {
 		errno = ENOBUFS;
 		return -1;