Add Nicira extension to OpenFlow for dropping spoofed ARP packets.

"ARP spoofing" is when a host claims an incorrect association between an
IP address and a MAC address for deceptive purposes.  OpenFlow by itself
can prevent a host from sending out ARP replies from an incorrect MAC
address in the Ethernet L2 header, but it cannot control the MAC addresses
inside the ARP L3 packet.  This commit adds a new action that can be used
to drop these spoofed packets.

CC: Paul Ingram <paul@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>

diff --git a/datapath/actions.c b/datapath/actions.c
index a6771b6c58c4d97c49725dde8dd2a82244259fad..943d7570569b6c876fef650b0d38a88160402c05 100644 (file)
--- a/datapath/actions.c
+++ b/datapath/actions.c
@@ -14,6 +14,7 @@
 #include <linux/tcp.h>
 #include <linux/udp.h>
 #include <linux/in6.h>
+#include <linux/if_arp.h>
 #include <linux/if_vlan.h>
 #include <net/inet_ecn.h>
 #include <net/ip.h>
@@ -318,6 +319,35 @@ static struct sk_buff *set_tp_port(struct sk_buff *skb,
        return skb;
 }
 
+/**
+ * is_spoofed_arp - check for invalid ARP packet
+ *
+ * @skb: skbuff containing an Ethernet packet, with network header pointing
+ * just past the Ethernet and optional 802.1Q header.
+ * @key: flow key extracted from @skb by flow_extract()
+ *
+ * Returns true if @skb is an invalid Ethernet+IPv4 ARP packet: one with screwy
+ * or truncated header fields or one whose inner and outer Ethernet address
+ * differ.
+ */
+static bool is_spoofed_arp(struct sk_buff *skb, const struct odp_flow_key *key)
+{
+       struct arp_eth_header *arp;
+
+       if (key->dl_type != htons(ETH_P_ARP))
+               return false;
+
+       if (skb_network_offset(skb) + sizeof(struct arp_eth_header) > skb->len)
+               return true;
+
+       arp = (struct arp_eth_header *)skb_network_header(skb);
+       return (arp->ar_hrd != htons(ARPHRD_ETHER) ||
+               arp->ar_pro != htons(ETH_P_IP) ||
+               arp->ar_hln != ETH_ALEN ||
+               arp->ar_pln != 4 ||
+               compare_ether_addr(arp->ar_sha, eth_hdr(skb)->h_source));
+}
+
 static void do_output(struct datapath *dp, struct sk_buff *skb, int out_port)
 {
        struct dp_port *p;
@@ -484,10 +514,16 @@ int execute_actions(struct datapath *dp, struct sk_buff *skb,
                case ODPAT_POP_PRIORITY:
                        skb->priority = priority;
                        break;
+
+               case ODPAT_DROP_SPOOFED_ARP:
+                       if (unlikely(is_spoofed_arp(skb, key)))
+                               goto exit;
+                       break;
                }
                if (!skb)
                        return -ENOMEM;
        }
+exit:
        if (prev_port != -1)
                do_output(dp, skb, prev_port);
        else

diff --git a/datapath/flow.c b/datapath/flow.c
index 5e362e300290ac161a33e143f8d8b358b7cb740f..c37c8e0ff99742d8a59ad9a550540b8172a4341e 100644 (file)
--- a/datapath/flow.c
+++ b/datapath/flow.c
@@ -34,21 +34,6 @@
 struct kmem_cache *flow_cache;
 static unsigned int hash_seed;
 
-struct arp_eth_header
-{
-       __be16      ar_hrd;     /* format of hardware address   */
-       __be16      ar_pro;     /* format of protocol address   */
-       unsigned char   ar_hln; /* length of hardware address   */
-       unsigned char   ar_pln; /* length of protocol address   */
-       __be16      ar_op;      /* ARP opcode (command)     */
-
-       /* Ethernet+IPv4 specific members. */
-       unsigned char       ar_sha[ETH_ALEN];   /* sender hardware address  */
-       unsigned char       ar_sip[4];          /* sender IP address        */
-       unsigned char       ar_tha[ETH_ALEN];   /* target hardware address  */
-       unsigned char       ar_tip[4];          /* target IP address        */
-} __attribute__((packed));
-
 static inline bool arphdr_ok(struct sk_buff *skb)
 {
        int nh_ofs = skb_network_offset(skb);

diff --git a/datapath/flow.h b/datapath/flow.h
index 534c7af24c3f8d4157c7c7427bcaf3f58261dbc6..80a5b66b1018a84aa193d92b9009c5c9f30ac1f6 100644 (file)
--- a/datapath/flow.h
+++ b/datapath/flow.h
@@ -14,6 +14,7 @@
 #include <linux/types.h>
 #include <linux/rcupdate.h>
 #include <linux/gfp.h>
+#include <linux/if_ether.h>
 #include <linux/jiffies.h>
 #include <linux/time.h>
 
@@ -42,6 +43,21 @@ struct sw_flow {
        u8 tcp_flags;           /* Union of seen TCP flags. */
 };
 
+struct arp_eth_header
+{
+       __be16      ar_hrd;     /* format of hardware address   */
+       __be16      ar_pro;     /* format of protocol address   */
+       unsigned char   ar_hln; /* length of hardware address   */
+       unsigned char   ar_pln; /* length of protocol address   */
+       __be16      ar_op;      /* ARP opcode (command)     */
+
+       /* Ethernet+IPv4 specific members. */
+       unsigned char       ar_sha[ETH_ALEN];   /* sender hardware address  */
+       unsigned char       ar_sip[4];          /* sender IP address        */
+       unsigned char       ar_tha[ETH_ALEN];   /* target hardware address  */
+       unsigned char       ar_tip[4];          /* target IP address        */
+} __attribute__((packed));
+
 extern struct kmem_cache *flow_cache;
 
 struct sw_flow_actions *flow_actions_alloc(size_t n_actions);

diff --git a/include/openflow/nicira-ext.h b/include/openflow/nicira-ext.h
index a80439c599fb606fc5d967ff97e541d0c9dad1cd..885e01da6a8f7bed19dfff962be9fc6a08212b94 100644 (file)
--- a/include/openflow/nicira-ext.h
+++ b/include/openflow/nicira-ext.h
@@ -131,7 +131,18 @@ enum nx_action_subtype {
      */
     NXAST_RESUBMIT,
 
-    NXAST_SET_TUNNEL                /* Set encapsulating tunnel ID. */
+    /* Set encapsulating tunnel ID. */
+    NXAST_SET_TUNNEL,
+
+    /* Stops processing further actions, if the packet being processed is an
+     * Ethernet+IPv4 ARP packet for which the source Ethernet address inside
+     * the ARP packet differs from the source Ethernet address in the Ethernet
+     * header.
+     *
+     * This is useful because OpenFlow does not provide a way to match on the
+     * Ethernet addresses inside ARP packets, so there is no other way to drop
+     * spoofed ARPs other than sending every packet up to the controller. */
+    NXAST_DROP_SPOOFED_ARP
 };
 
 /* Action structure for NXAST_RESUBMIT. */

diff --git a/include/openvswitch/datapath-protocol.h b/include/openvswitch/datapath-protocol.h
index c3ec4dcf2f7a88417aa592b65532d94966b41d74..839c4846289e7f2bbdedd773c6458f97b8a4af8c 100644 (file)
--- a/include/openvswitch/datapath-protocol.h
+++ b/include/openvswitch/datapath-protocol.h
@@ -281,7 +281,8 @@ struct odp_flowvec {
 #define ODPAT_SET_TUNNEL        13   /* Set the encapsulating tunnel ID. */
 #define ODPAT_SET_PRIORITY      14   /* Set skb->priority. */
 #define ODPAT_POP_PRIORITY      15   /* Restore original skb->priority. */
-#define ODPAT_N_ACTIONS         16
+#define ODPAT_DROP_SPOOFED_ARP  16   /* Drop ARPs with spoofed source MAC. */
+#define ODPAT_N_ACTIONS         17
 
 struct odp_action_output {
     uint16_t type;              /* ODPAT_OUTPUT. */

diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index c17b52572ebd70eb19ecf5139de0fda88fe0f450..6c813299f7aea5302e7c41bceb17093f0912a84d 100644 (file)
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -1269,6 +1269,34 @@ dp_netdev_output_control(struct dp_netdev *dp, const struct ofpbuf *packet,
     return 0;
 }
 
+/* Returns true if 'packet' is an invalid Ethernet+IPv4 ARP packet: one with
+ * screwy or truncated header fields or one whose inner and outer Ethernet
+ * address differ. */
+static bool
+dp_netdev_is_spoofed_arp(struct ofpbuf *packet, const struct odp_flow_key *key)
+{
+    struct arp_eth_header *arp;
+    struct eth_header *eth;
+    ptrdiff_t l3_size;
+
+    if (key->dl_type != htons(ETH_TYPE_ARP)) {
+        return false;
+    }
+
+    l3_size = (char *) ofpbuf_end(packet) - (char *) packet->l3;
+    if (l3_size < sizeof(struct arp_eth_header)) {
+        return true;
+    }
+
+    eth = packet->l2;
+    arp = packet->l3;
+    return (arp->ar_hrd != htons(ARP_HRD_ETHERNET)
+            || arp->ar_pro != htons(ARP_PRO_IP)
+            || arp->ar_hln != ETH_HEADER_LEN
+            || arp->ar_pln != 4
+            || !eth_addr_equals(arp->ar_sha, eth->eth_src));
+}
+
 static int
 dp_netdev_execute_actions(struct dp_netdev *dp,
                           struct ofpbuf *packet, const flow_t *key,
@@ -1329,6 +1357,11 @@ dp_netdev_execute_actions(struct dp_netdev *dp,
                case ODPAT_SET_TP_DST:
                        dp_netdev_set_tp_port(packet, key, &a->tp_port);
                        break;
+
+        case ODPAT_DROP_SPOOFED_ARP:
+            if (dp_netdev_is_spoofed_arp(packet, key)) {
+                return 0;
+            }
                }
        }
     return 0;

diff --git a/ofproto/ofproto.c b/ofproto/ofproto.c
index 91ff02388c3b09d72d8c0a45a7317437c01558f9..2e1530a3f99768222a0c6ea736b730c9dc73389a 100644 (file)
--- a/ofproto/ofproto.c
+++ b/ofproto/ofproto.c
@@ -2631,6 +2631,12 @@ xlate_nicira_action(struct action_xlate_ctx *ctx,
         ctx->flow.tun_id = oa->tunnel.tun_id = nast->tun_id;
         break;
 
+    case NXAST_DROP_SPOOFED_ARP:
+        if (ctx->flow.dl_type == htons(ETH_TYPE_ARP)) {
+            odp_actions_add(ctx->out, ODPAT_DROP_SPOOFED_ARP);
+        }
+        break;
+
     /* If you add a new action here that modifies flow data, don't forget to
      * update the flow key in ctx->flow at the same time. */