[master] Added check for invalid failover message type.

Merges in rt36653

RELNOTES

@@ -62,6 +62,9 @@ by Eric Young (eay@cryptsoft.com).
   and hmac-sha512
   [ISC-Bugs #36947]
 
+- Added check for invalid failover message type.
+  [ISC-Bugs #36653]
+
 - Corrected rate limiting checks for bad packet logging.
   [ISC-Bugs #36897]
 

includes/failover.h

@@ -161,6 +161,8 @@ typedef struct {
 #define FTM_CONTACT		11
 #define FTM_DISCONNECT		12
 
+#define FTM_MAX			FTM_DISCONNECT
+
 /* Reject reasons from Section 12.21: */
 #define FTR_ILLEGAL_IP_ADDR	1
 #define FTR_FATAL_CONFLICT	2

server/failover.c

@@ -626,6 +626,12 @@ static isc_result_t do_a_failover_option (c, link)
 		return DHCP_R_PROTOCOLERROR;
 	}
 
+	if (link->imsg->type > FTM_MAX) {
+		log_error ("FAILOVER: invalid message type: %d",
+			   link->imsg->type);
+		return DHCP_R_PROTOCOLERROR;
+	}
+
 	/* Get option code. */
 	omapi_connection_get_uint16 (c, &option_code);
 	link -> imsg_count += 2;