interface-ip: harden eui64 IPv6 prefix address generation

Check if a mac address is actually present when generating an eui64 based
IPv6 address; in case of failure bail out.
At the same time make sure the active mac address is used as input for the
eui64 based IPv6 address and guarantee IPv6 prefix address generation is
based on the actual config by resetting the IPv6 prefix address in the
assignment structure when it gets deleted.

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

1 files changed, 22 insertions, 4 deletions

diff --git a/interface-ip.c b/interface-ip.c
index 716a093..dcf3390 100644
--- a/interface-ip.c
+++ b/interface-ip.c
@@ -712,9 +712,16 @@ random_ifaceid(struct in6_addr *addr)
 	addr->s6_addr32[3] = (uint32_t)mrand48();
 }
 
-static void
+static bool
 eui64_ifaceid(struct interface *iface, struct in6_addr *addr)
 {
+	struct device_settings st;
+
+	device_merge_settings(iface->l3_dev.dev, &st);
+
+	if (!(st.flags & DEV_OPT_MACADDR))
+		return false;
+
 	/* get mac address */
 	uint8_t *macaddr = iface->l3_dev.dev->settings.macaddr;
 	uint8_t *ifaceid = addr->s6_addr + 8;
@@ -723,11 +730,15 @@ eui64_ifaceid(struct interface *iface, struct in6_addr *addr)
 	ifaceid[3] = 0xff;
 	ifaceid[4] = 0xfe;
 	ifaceid[0] ^= 0x02;
+
+	return true;
 }
 
-static void
+static bool
 generate_ifaceid(struct interface *iface, struct in6_addr *addr)
 {
+	bool ret = true;
+
 	/* generate new iface id */
 	switch (iface->assignment_iface_id_selection) {
 	case IFID_FIXED:
@@ -741,9 +752,13 @@ generate_ifaceid(struct interface *iface, struct in6_addr *addr)
 		break;
 	case IFID_EUI64:
 		/* eui64 */
-		eui64_ifaceid(iface, addr);
+		ret = eui64_ifaceid(iface, addr);
+		break;
+	default:
+		ret = false;
 		break;
 	}
+	return ret;
 }
 
 static void
@@ -797,12 +812,15 @@ interface_set_prefix_address(struct device_prefix_assignment *assignment,
 		system_del_route(l3_downlink, &route);
 		system_add_address(l3_downlink, &addr);
 
+		assignment->addr = in6addr_any;
 		assignment->enabled = false;
 	} else if (add && (iface->state == IFS_UP || iface->state == IFS_SETUP)) {
 		if (IN6_IS_ADDR_UNSPECIFIED(&addr.addr.in6)) {
 			addr.addr.in6 = prefix->addr;
 			addr.addr.in6.s6_addr32[1] |= htonl(assignment->assigned);
-			generate_ifaceid(iface, &addr.addr.in6);
+			if (!generate_ifaceid(iface, &addr.addr.in6))
+				return;
+
 			assignment->addr = addr.addr.in6;
 			route.addr = addr.addr;
 		}