ipsec: drop outbound ESP when no crypto alg set

Type: fix

If a tunnel interface has the crypto alg set on the outbound SA to
IPSEC_CRYPTO_ALG_NONE and packets are sent out that interface,
the attempt to write an ESP trailer on the packet occurs at the
wrong offset and the vnet buffer opaque data is corrupted, which
can result in a SEGV when a subsequent node attempts to use that
data.

When an outbound SA is set on a tunnel interface which has no crypto
alg set, add a node to the ip{4,6}-output feature arcs which drops all
packets leaving that interface instead of adding the node which would
try to encrypt the packets.

Change-Id: Ie0ac8d8fdc8a035ab8bb83b72b6a94161bebaa48
Signed-off-by: Matthew Smith <mgsmith@netgate.com>

4 files changed, 162 insertions, 5 deletions

diff --git a/src/vnet/ipsec/esp_encrypt.c b/src/vnet/ipsec/esp_encrypt.c
index c879a404b54..041b268975d 100644
--- a/src/vnet/ipsec/esp_encrypt.c
+++ b/src/vnet/ipsec/esp_encrypt.c
@@ -666,6 +666,137 @@ VNET_FEATURE_INIT (esp6_encrypt_tun_feat_node, static) =
 };
 /* *INDENT-ON* */
 
+typedef struct
+{
+  u32 sa_index;
+} esp_no_crypto_trace_t;
+
+static u8 *
+format_esp_no_crypto_trace (u8 * s, va_list * args)
+{
+  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
+  CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
+  esp_no_crypto_trace_t *t = va_arg (*args, esp_no_crypto_trace_t *);
+
+  s = format (s, "esp-no-crypto: sa-index %u", t->sa_index);
+
+  return s;
+}
+
+enum
+{
+  ESP_NO_CRYPTO_NEXT_DROP,
+  ESP_NO_CRYPTO_N_NEXT,
+};
+
+enum
+{
+  ESP_NO_CRYPTO_ERROR_RX_PKTS,
+};
+
+static char *esp_no_crypto_error_strings[] = {
+  "Outbound ESP packets received",
+};
+
+always_inline uword
+esp_no_crypto_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
+		      vlib_frame_t * frame)
+{
+  vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b = bufs;
+  u16 nexts[VLIB_FRAME_SIZE], *next = nexts;
+  u32 *from = vlib_frame_vector_args (frame);
+  u32 n_left = frame->n_vectors;
+
+  vlib_get_buffers (vm, from, b, n_left);
+
+  while (n_left > 0)
+    {
+      u32 next0;
+      u32 sa_index0;
+
+      /* packets are always going to be dropped, but get the sa_index */
+      sa_index0 = *(u32 *) vnet_feature_next_with_data (&next0, b[0],
+							sizeof (sa_index0));
+
+      next[0] = ESP_NO_CRYPTO_NEXT_DROP;
+
+      if (PREDICT_FALSE (b[0]->flags & VLIB_BUFFER_IS_TRACED))
+	{
+	  esp_no_crypto_trace_t *tr = vlib_add_trace (vm, node, b[0],
+						      sizeof (*tr));
+	  tr->sa_index = sa_index0;
+	}
+
+      n_left -= 1;
+      next += 1;
+      b += 1;
+    }
+
+  vlib_node_increment_counter (vm, node->node_index,
+			       ESP_NO_CRYPTO_ERROR_RX_PKTS, frame->n_vectors);
+
+  vlib_buffer_enqueue_to_next (vm, node, from, nexts, frame->n_vectors);
+
+  return frame->n_vectors;
+}
+
+VLIB_NODE_FN (esp4_no_crypto_tun_node) (vlib_main_t * vm,
+					vlib_node_runtime_t * node,
+					vlib_frame_t * from_frame)
+{
+  return esp_no_crypto_inline (vm, node, from_frame);
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (esp4_no_crypto_tun_node) =
+{
+  .name = "esp4-no-crypto",
+  .vector_size = sizeof (u32),
+  .format_trace = format_esp_no_crypto_trace,
+  .n_errors = ARRAY_LEN(esp_no_crypto_error_strings),
+  .error_strings = esp_no_crypto_error_strings,
+  .n_next_nodes = ESP_NO_CRYPTO_N_NEXT,
+  .next_nodes = {
+    [ESP_NO_CRYPTO_NEXT_DROP] = "ip4-drop",
+  },
+};
+
+VNET_FEATURE_INIT (esp4_no_crypto_tun_feat_node, static) =
+{
+  .arc_name = "ip4-output",
+  .node_name = "esp4-no-crypto",
+  .runs_before = VNET_FEATURES ("adj-midchain-tx"),
+};
+
+VLIB_NODE_FN (esp6_no_crypto_tun_node) (vlib_main_t * vm,
+					vlib_node_runtime_t * node,
+					vlib_frame_t * from_frame)
+{
+  return esp_no_crypto_inline (vm, node, from_frame);
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (esp6_no_crypto_tun_node) =
+{
+  .name = "esp6-no-crypto",
+  .vector_size = sizeof (u32),
+  .format_trace = format_esp_no_crypto_trace,
+  .n_errors = ARRAY_LEN(esp_no_crypto_error_strings),
+  .error_strings = esp_no_crypto_error_strings,
+  .n_next_nodes = ESP_NO_CRYPTO_N_NEXT,
+  .next_nodes = {
+    [ESP_NO_CRYPTO_NEXT_DROP] = "ip6-drop",
+  },
+};
+
+VNET_FEATURE_INIT (esp6_no_crypto_tun_feat_node, static) =
+{
+  .arc_name = "ip6-output",
+  .node_name = "esp6-no-crypto",
+  .runs_before = VNET_FEATURES ("adj-midchain-tx"),
+};
+/* *INDENT-ON* */
+
 /*
  * fd.io coding-style-patch-verification: ON
  *
diff --git a/src/vnet/ipsec/ipsec.c b/src/vnet/ipsec/ipsec.c
index 4caae4840fb..21e1d5ec43f 100644
--- a/src/vnet/ipsec/ipsec.c
+++ b/src/vnet/ipsec/ipsec.c
@@ -122,7 +122,7 @@ ipsec_add_node (vlib_main_t * vm, const char *node_name,
   *out_next_index = vlib_node_add_next (vm, prev_node->index, node->index);
 }
 
-static void
+void
 ipsec_add_feature (const char *arc_name,
 		   const char *node_name, u32 * out_feature_index)
 {
diff --git a/src/vnet/ipsec/ipsec.h b/src/vnet/ipsec/ipsec.h
index c77d0fe7dd8..ccbe7d7aa5c 100644
--- a/src/vnet/ipsec/ipsec.h
+++ b/src/vnet/ipsec/ipsec.h
@@ -142,6 +142,10 @@ typedef struct
   u32 esp4_encrypt_tun_feature_index;
   u32 esp6_encrypt_tun_feature_index;
 
+  /* tun nodes to drop packets when no crypto alg set on outbound SA */
+  u32 esp4_no_crypto_tun_feature_index;
+  u32 esp6_no_crypto_tun_feature_index;
+
   /* pool of ah backends */
   ipsec_ah_backend_t *ah_backends;
   /* pool of esp backends */
@@ -241,6 +245,9 @@ ipsec_sa_get (u32 sa_index)
   return (pool_elt_at_index (ipsec_main.sad, sa_index));
 }
 
+void ipsec_add_feature (const char *arc_name, const char *node_name,
+			u32 * out_feature_index);
+
 #endif /* __IPSEC_H__ */
 
 /*
diff --git a/src/vnet/ipsec/ipsec_if.c b/src/vnet/ipsec/ipsec_if.c
index 5fc49e1af4e..562f40ec9ab 100644
--- a/src/vnet/ipsec/ipsec_if.c
+++ b/src/vnet/ipsec/ipsec_if.c
@@ -234,19 +234,31 @@ static void
 ipsec_tunnel_feature_set (ipsec_main_t * im, ipsec_tunnel_if_t * t, u8 enable)
 {
   u8 arc;
+  u32 esp4_feature_index, esp6_feature_index;
+  ipsec_sa_t *sa;
+
+  sa = ipsec_sa_get (t->output_sa_index);
+  if (sa->crypto_alg == IPSEC_CRYPTO_ALG_NONE)
+    {
+      esp4_feature_index = im->esp4_no_crypto_tun_feature_index;
+      esp6_feature_index = im->esp6_no_crypto_tun_feature_index;
+    }
+  else
+    {
+      esp4_feature_index = im->esp4_encrypt_tun_feature_index;
+      esp6_feature_index = im->esp6_encrypt_tun_feature_index;
+    }
 
   arc = vnet_get_feature_arc_index ("ip4-output");
 
-  vnet_feature_enable_disable_with_index (arc,
-					  im->esp4_encrypt_tun_feature_index,
+  vnet_feature_enable_disable_with_index (arc, esp4_feature_index,
 					  t->sw_if_index, enable,
 					  &t->output_sa_index,
 					  sizeof (t->output_sa_index));
 
   arc = vnet_get_feature_arc_index ("ip6-output");
 
-  vnet_feature_enable_disable_with_index (arc,
-					  im->esp6_encrypt_tun_feature_index,
+  vnet_feature_enable_disable_with_index (arc, esp6_feature_index,
 					  t->sw_if_index, enable,
 					  &t->output_sa_index,
 					  sizeof (t->output_sa_index));
@@ -562,6 +574,13 @@ ipsec_tunnel_if_init (vlib_main_t * vm)
 
   udp_register_dst_port (vm, UDP_DST_PORT_ipsec, ipsec4_if_input_node.index,
 			 1);
+
+  /* set up feature nodes to drop outbound packets with no crypto alg set */
+  ipsec_add_feature ("ip4-output", "esp4-no-crypto",
+		     &im->esp4_no_crypto_tun_feature_index);
+  ipsec_add_feature ("ip6-output", "esp6-no-crypto",
+		     &im->esp6_no_crypto_tun_feature_index);
+
   return 0;
 }