ipsec: make pre-shared keys harder to misuse

Using pre-shared keys is usually a bad idea, one should use eg. IKEv2
instead, but one does not always have the choice.

For AES-CBC, the IV must be unpredictable (see NIST SP800-38a Appendix
C) whereas for AES-CTR or AES-GCM, the IV should never be reused with
the same key material (see NIST SP800-38a Appendix B and NIST SP800-38d
section 8).
If one uses pre-shared keys and VPP is restarted, the IV counter
restarts at 0 and the same IVs are generated with the same pre-shared
keys materials.

To fix those issues we follow the recommendation from NIST SP800-38a
and NIST SP800-38d:
 - we use a PRNG (not cryptographically secured) to generate IVs to
avoid generating the same IV sequence between VPP restarts. The PRNG is
chosen so that there is a low chance of generating the same sequence
 - for AES-CBC, the generated IV is encrypted as part of the message.
This makes the (predictable) PRNG-generated IV unpredictable as it is
encrypted with the secret key
 - for AES-CTR and GCM, we use the IV as-is as predictable IVs are fine

Most of the changes in this patch are caused by the need to shoehorn an
additional state of 2 u64 for the PRNG in the 1st cacheline of the SA
object.

Type: improvement

Change-Id: I2af89c21ae4b2c4c33dd21aeffcfb79c13c9d84c
Signed-off-by: Benoît Ganne <bganne@cisco.com>

8 files changed, 122 insertions, 137 deletions

diff --git a/src/vnet/ipsec/ah_decrypt.c b/src/vnet/ipsec/ah_decrypt.c
index ce4610dae6e..f20f620eb3c 100644
--- a/src/vnet/ipsec/ah_decrypt.c
+++ b/src/vnet/ipsec/ah_decrypt.c
@@ -155,7 +155,7 @@ ah_decrypt_inline (vlib_main_t * vm,
 					  thread_index, current_sa_index);
 	}
 
-      if (PREDICT_FALSE (~0 == sa0->thread_index))
+      if (PREDICT_FALSE ((u16) ~0 == sa0->thread_index))
 	{
 	  /* this is the first packet to use this SA, claim the SA
 	   * for this thread. this could happen simultaneously on
diff --git a/src/vnet/ipsec/ah_encrypt.c b/src/vnet/ipsec/ah_encrypt.c
index e2d17d48ccf..03e04880161 100644
--- a/src/vnet/ipsec/ah_encrypt.c
+++ b/src/vnet/ipsec/ah_encrypt.c
@@ -168,7 +168,7 @@ ah_encrypt_inline (vlib_main_t * vm,
       pd->sa_index = current_sa_index;
       next[0] = AH_ENCRYPT_NEXT_DROP;
 
-      if (PREDICT_FALSE (~0 == sa0->thread_index))
+      if (PREDICT_FALSE ((u16) ~0 == sa0->thread_index))
 	{
 	  /* this is the first packet to use this SA, claim the SA
 	   * for this thread. this could happen simultaneously on
diff --git a/src/vnet/ipsec/esp.h b/src/vnet/ipsec/esp.h
index 05773a2a328..311882af08e 100644
--- a/src/vnet/ipsec/esp.h
+++ b/src/vnet/ipsec/esp.h
@@ -86,9 +86,6 @@ typedef struct esp_aead_t_
 } __clib_packed esp_aead_t;
 
 #define ESP_SEQ_MAX		(4294967295UL)
-#define ESP_MAX_BLOCK_SIZE	(16)
-#define ESP_MAX_IV_SIZE		(16)
-#define ESP_MAX_ICV_SIZE	(32)
 
 u8 *format_esp_header (u8 * s, va_list * args);
 
diff --git a/src/vnet/ipsec/esp_decrypt.c b/src/vnet/ipsec/esp_decrypt.c
index 1bcc65ca972..827d168f98a 100644
--- a/src/vnet/ipsec/esp_decrypt.c
+++ b/src/vnet/ipsec/esp_decrypt.c
@@ -603,7 +603,7 @@ esp_decrypt_prepare_async_frame (vlib_main_t *vm, vlib_node_runtime_t *node,
   esp_decrypt_packet_data_t *async_pd = &(esp_post_data (b))->decrypt_data;
   esp_decrypt_packet_data2_t *async_pd2 = esp_post_data2 (b);
   u8 *tag = payload + len, *iv = payload + esp_sz, *aad = 0;
-  u32 key_index;
+  const u32 key_index = sa0->crypto_key_index;
   u32 crypto_len, integ_len = 0;
   i16 crypto_start_offset, integ_start_offset = 0;
   u8 flags = 0;
@@ -611,7 +611,6 @@ esp_decrypt_prepare_async_frame (vlib_main_t *vm, vlib_node_runtime_t *node,
   if (!ipsec_sa_is_set_IS_AEAD (sa0))
     {
       /* linked algs */
-      key_index = sa0->linked_key_index;
       integ_start_offset = payload - b->data;
       integ_len = len;
       if (PREDICT_TRUE (sa0->integ_op_id != VNET_CRYPTO_OP_NONE))
@@ -664,8 +663,6 @@ esp_decrypt_prepare_async_frame (vlib_main_t *vm, vlib_node_runtime_t *node,
       else
 	esp_insert_esn (vm, sa0, pd, pd2, &integ_len, &tag, &len, b, payload);
     }
-  else
-    key_index = sa0->crypto_key_index;
 
 out:
   /* crypto */
@@ -1103,7 +1100,7 @@ esp_decrypt_inline (vlib_main_t *vm, vlib_node_runtime_t *node,
 	  is_async = im->async_mode | ipsec_sa_is_set_IS_ASYNC (sa0);
 	}
 
-      if (PREDICT_FALSE (~0 == sa0->thread_index))
+      if (PREDICT_FALSE ((u16) ~0 == sa0->thread_index))
 	{
 	  /* this is the first packet to use this SA, claim the SA
 	   * for this thread. this could happen simultaneously on
diff --git a/src/vnet/ipsec/esp_encrypt.c b/src/vnet/ipsec/esp_encrypt.c
index 88e93b9b2d4..861b3e98650 100644
--- a/src/vnet/ipsec/esp_encrypt.c
+++ b/src/vnet/ipsec/esp_encrypt.c
@@ -219,17 +219,18 @@ esp_get_ip6_hdr_len (ip6_header_t * ip6, ip6_ext_header_t ** ext_hdr)
  * encryption mode: IVs must be unpredictable for AES-CBC whereas it can
  * be predictable but should never be reused with the same key material
  * for CTR and GCM.
- * We use a packet counter as the IV for CTR and GCM, and to ensure the
- * IV is unpredictable for CBC, it is then encrypted using the same key
- * as the message. You can refer to NIST SP800-38a and NIST SP800-38d
- * for more details. */
+ * To avoid reusing the same IVs between multiple VPP instances and between
+ * restarts, we use a properly chosen PRNG to generate IVs. To ensure the IV is
+ * unpredictable for CBC, it is then encrypted using the same key as the
+ * message. You can refer to NIST SP800-38a and NIST SP800-38d for more
+ * details. */
 static_always_inline void *
 esp_generate_iv (ipsec_sa_t *sa, void *payload, int iv_sz)
 {
   ASSERT (iv_sz >= sizeof (u64));
   u64 *iv = (u64 *) (payload - iv_sz);
   clib_memset_u8 (iv, 0, iv_sz);
-  *iv = sa->iv_counter++;
+  *iv = clib_pcg64i_random_r (&sa->iv_prng);
   return iv;
 }
 
@@ -434,7 +435,7 @@ esp_prepare_sync_op (vlib_main_t *vm, ipsec_per_thread_data_t *ptd,
 	  crypto_len += iv_sz;
 	}
 
-      if (lb != b[0])
+      if (PREDICT_FALSE (lb != b[0]))
 	{
 	  /* is chained */
 	  op->flags |= VNET_CRYPTO_OP_FLAG_CHAINED_BUFFERS;
@@ -497,7 +498,7 @@ esp_prepare_async_frame (vlib_main_t *vm, ipsec_per_thread_data_t *ptd,
   esp_post_data_t *post = esp_post_data (b);
   u8 *tag, *iv, *aad = 0;
   u8 flag = 0;
-  u32 key_index;
+  const u32 key_index = sa->crypto_key_index;
   i16 crypto_start_offset, integ_start_offset;
   u16 crypto_total_len, integ_total_len;
 
@@ -508,8 +509,6 @@ esp_prepare_async_frame (vlib_main_t *vm, ipsec_per_thread_data_t *ptd,
   crypto_total_len = integ_total_len = payload_len - icv_sz;
   tag = payload + crypto_total_len;
 
-  key_index = sa->linked_key_index;
-
   /* generate the IV in front of the payload */
   void *pkt_iv = esp_generate_iv (sa, payload, iv_sz);
 
@@ -523,7 +522,6 @@ esp_prepare_async_frame (vlib_main_t *vm, ipsec_per_thread_data_t *ptd,
 	  /* constuct aad in a scratch space in front of the nonce */
 	  aad = (u8 *) nonce - sizeof (esp_aead_t);
 	  esp_aad_fill (aad, esp, sa, sa->seq_hi);
-	  key_index = sa->crypto_key_index;
 	}
       else
 	{
@@ -705,7 +703,7 @@ esp_encrypt_inline (vlib_main_t *vm, vlib_node_runtime_t *node,
 	  is_async = im->async_mode | ipsec_sa_is_set_IS_ASYNC (sa0);
 	}
 
-      if (PREDICT_FALSE (~0 == sa0->thread_index))
+      if (PREDICT_FALSE ((u16) ~0 == sa0->thread_index))
 	{
 	  /* this is the first packet to use this SA, claim the SA
 	   * for this thread. this could happen simultaneously on
diff --git a/src/vnet/ipsec/ipsec.c b/src/vnet/ipsec/ipsec.c
index 3ea2e4d62df..86cb8982d07 100644
--- a/src/vnet/ipsec/ipsec.c
+++ b/src/vnet/ipsec/ipsec.c
@@ -408,10 +408,7 @@ ipsec_set_async_mode (u32 is_enabled)
 
   /* change SA crypto op data */
   pool_foreach (sa, ipsec_sa_pool)
-    {
-      sa->crypto_op_data =
-	(is_enabled ? sa->async_op_data.data : sa->sync_op_data.data);
-    }
+    ipsec_sa_set_async_mode (sa, is_enabled);
 }
 
 static void
diff --git a/src/vnet/ipsec/ipsec_sa.c b/src/vnet/ipsec/ipsec_sa.c
index eed71a48500..95db17e7fb1 100644
--- a/src/vnet/ipsec/ipsec_sa.c
+++ b/src/vnet/ipsec/ipsec_sa.c
@@ -13,6 +13,7 @@
  * limitations under the License.
  */
 
+#include <sys/random.h>
 #include <vnet/ipsec/ipsec.h>
 #include <vnet/ipsec/esp.h>
 #include <vnet/udp/udp_local.h>
@@ -92,14 +93,35 @@ ipsec_sa_stack (ipsec_sa_t * sa)
 }
 
 void
+ipsec_sa_set_async_mode (ipsec_sa_t *sa, int is_enabled)
+{
+  if (is_enabled)
+    {
+      sa->crypto_key_index = sa->crypto_async_key_index;
+      sa->crypto_enc_op_id = sa->crypto_async_enc_op_id;
+      sa->crypto_dec_op_id = sa->crypto_async_dec_op_id;
+      sa->integ_key_index = ~0;
+      sa->integ_op_id = ~0;
+    }
+  else
+    {
+      sa->crypto_key_index = sa->crypto_sync_key_index;
+      sa->crypto_enc_op_id = sa->crypto_sync_enc_op_id;
+      sa->crypto_dec_op_id = sa->crypto_sync_dec_op_id;
+      sa->integ_key_index = sa->integ_sync_key_index;
+      sa->integ_op_id = sa->integ_sync_op_id;
+    }
+}
+
+void
 ipsec_sa_set_crypto_alg (ipsec_sa_t * sa, ipsec_crypto_alg_t crypto_alg)
 {
   ipsec_main_t *im = &ipsec_main;
   sa->crypto_alg = crypto_alg;
   sa->crypto_iv_size = im->crypto_algs[crypto_alg].iv_size;
   sa->esp_block_align = clib_max (4, im->crypto_algs[crypto_alg].block_align);
-  sa->sync_op_data.crypto_enc_op_id = im->crypto_algs[crypto_alg].enc_op_id;
-  sa->sync_op_data.crypto_dec_op_id = im->crypto_algs[crypto_alg].dec_op_id;
+  sa->crypto_sync_enc_op_id = im->crypto_algs[crypto_alg].enc_op_id;
+  sa->crypto_sync_dec_op_id = im->crypto_algs[crypto_alg].dec_op_id;
   sa->crypto_calg = im->crypto_algs[crypto_alg].alg;
   ASSERT (sa->crypto_iv_size <= ESP_MAX_IV_SIZE);
   ASSERT (sa->esp_block_align <= ESP_MAX_BLOCK_SIZE);
@@ -122,7 +144,7 @@ ipsec_sa_set_integ_alg (ipsec_sa_t * sa, ipsec_integ_alg_t integ_alg)
   ipsec_main_t *im = &ipsec_main;
   sa->integ_alg = integ_alg;
   sa->integ_icv_size = im->integ_algs[integ_alg].icv_size;
-  sa->sync_op_data.integ_op_id = im->integ_algs[integ_alg].op_id;
+  sa->integ_sync_op_id = im->integ_algs[integ_alg].op_id;
   sa->integ_calg = im->integ_algs[integ_alg].alg;
   ASSERT (sa->integ_icv_size <= ESP_MAX_ICV_SIZE);
 }
@@ -133,38 +155,32 @@ ipsec_sa_set_async_op_ids (ipsec_sa_t * sa)
   /* *INDENT-OFF* */
   if (ipsec_sa_is_set_USE_ESN (sa))
     {
-#define _(n, s, k) \
-  if( sa->sync_op_data.crypto_enc_op_id == VNET_CRYPTO_OP_##n##_ENC ) \
-    sa->async_op_data.crypto_async_enc_op_id = \
-      VNET_CRYPTO_OP_##n##_TAG16_AAD12_ENC; \
-  if( sa->sync_op_data.crypto_dec_op_id == VNET_CRYPTO_OP_##n##_DEC ) \
-    sa->async_op_data.crypto_async_dec_op_id = \
-      VNET_CRYPTO_OP_##n##_TAG16_AAD12_DEC;
-    foreach_crypto_aead_alg
+#define _(n, s, k)                                                            \
+  if (sa->crypto_sync_enc_op_id == VNET_CRYPTO_OP_##n##_ENC)                  \
+    sa->crypto_async_enc_op_id = VNET_CRYPTO_OP_##n##_TAG16_AAD12_ENC;        \
+  if (sa->crypto_sync_dec_op_id == VNET_CRYPTO_OP_##n##_DEC)                  \
+    sa->crypto_async_dec_op_id = VNET_CRYPTO_OP_##n##_TAG16_AAD12_DEC;
+      foreach_crypto_aead_alg
 #undef _
     }
   else
     {
-#define _(n, s, k) \
-  if( sa->sync_op_data.crypto_enc_op_id == VNET_CRYPTO_OP_##n##_ENC ) \
-    sa->async_op_data.crypto_async_enc_op_id = \
-      VNET_CRYPTO_OP_##n##_TAG16_AAD8_ENC; \
-  if( sa->sync_op_data.crypto_dec_op_id == VNET_CRYPTO_OP_##n##_DEC ) \
-    sa->async_op_data.crypto_async_dec_op_id = \
-      VNET_CRYPTO_OP_##n##_TAG16_AAD8_DEC;
-    foreach_crypto_aead_alg
+#define _(n, s, k)                                                            \
+  if (sa->crypto_sync_enc_op_id == VNET_CRYPTO_OP_##n##_ENC)                  \
+    sa->crypto_async_enc_op_id = VNET_CRYPTO_OP_##n##_TAG16_AAD8_ENC;         \
+  if (sa->crypto_sync_dec_op_id == VNET_CRYPTO_OP_##n##_DEC)                  \
+    sa->crypto_async_dec_op_id = VNET_CRYPTO_OP_##n##_TAG16_AAD8_DEC;
+      foreach_crypto_aead_alg
 #undef _
     }
 
-#define _(c, h, s, k ,d) \
-  if( sa->sync_op_data.crypto_enc_op_id == VNET_CRYPTO_OP_##c##_ENC && \
-      sa->sync_op_data.integ_op_id == VNET_CRYPTO_OP_##h##_HMAC) \
-    sa->async_op_data.crypto_async_enc_op_id = \
-      VNET_CRYPTO_OP_##c##_##h##_TAG##d##_ENC; \
-  if( sa->sync_op_data.crypto_dec_op_id == VNET_CRYPTO_OP_##c##_DEC && \
-      sa->sync_op_data.integ_op_id == VNET_CRYPTO_OP_##h##_HMAC) \
-    sa->async_op_data.crypto_async_dec_op_id = \
-      VNET_CRYPTO_OP_##c##_##h##_TAG##d##_DEC;
+#define _(c, h, s, k, d)                                                      \
+  if (sa->crypto_sync_enc_op_id == VNET_CRYPTO_OP_##c##_ENC &&                \
+      sa->integ_sync_op_id == VNET_CRYPTO_OP_##h##_HMAC)                      \
+    sa->crypto_async_enc_op_id = VNET_CRYPTO_OP_##c##_##h##_TAG##d##_ENC;     \
+  if (sa->crypto_sync_dec_op_id == VNET_CRYPTO_OP_##c##_DEC &&                \
+      sa->integ_sync_op_id == VNET_CRYPTO_OP_##h##_HMAC)                      \
+    sa->crypto_async_dec_op_id = VNET_CRYPTO_OP_##c##_##h##_TAG##d##_DEC;
   foreach_crypto_link_async_alg
 #undef _
   /* *INDENT-ON* */
@@ -313,6 +329,7 @@ ipsec_sa_add_and_lock (u32 id, u32 spi, ipsec_protocol_t proto,
   clib_error_t *err;
   ipsec_sa_t *sa;
   u32 sa_index;
+  u64 rand[2];
   uword *p;
   int rv;
 
@@ -320,8 +337,13 @@ ipsec_sa_add_and_lock (u32 id, u32 spi, ipsec_protocol_t proto,
   if (p)
     return VNET_API_ERROR_ENTRY_ALREADY_EXISTS;
 
+  if (getrandom (rand, sizeof (rand), 0) != sizeof (rand))
+    return VNET_API_ERROR_INIT_FAILED;
+
   pool_get_aligned_zero (ipsec_sa_pool, sa, CLIB_CACHE_LINE_BYTES);
 
+  clib_pcg64i_srandom_r (&sa->iv_prng, rand[0], rand[1]);
+
   fib_node_init (&sa->node, FIB_NODE_TYPE_IPSEC_SA);
   fib_node_lock (&sa->node);
   sa_index = sa - ipsec_sa_pool;
@@ -352,10 +374,9 @@ ipsec_sa_add_and_lock (u32 id, u32 spi, ipsec_protocol_t proto,
 
   clib_memcpy (&sa->crypto_key, ck, sizeof (sa->crypto_key));
 
-  sa->crypto_key_index = vnet_crypto_key_add (vm,
-					      im->crypto_algs[crypto_alg].alg,
-					      (u8 *) ck->data, ck->len);
-  if (~0 == sa->crypto_key_index)
+  sa->crypto_sync_key_index = vnet_crypto_key_add (
+    vm, im->crypto_algs[crypto_alg].alg, (u8 *) ck->data, ck->len);
+  if (~0 == sa->crypto_sync_key_index)
     {
       pool_put (ipsec_sa_pool, sa);
       return VNET_API_ERROR_KEY_LENGTH;
@@ -363,36 +384,34 @@ ipsec_sa_add_and_lock (u32 id, u32 spi, ipsec_protocol_t proto,
 
   if (integ_alg != IPSEC_INTEG_ALG_NONE)
     {
-      sa->integ_key_index = vnet_crypto_key_add (vm,
-						 im->
-						 integ_algs[integ_alg].alg,
-						 (u8 *) ik->data, ik->len);
-      if (~0 == sa->integ_key_index)
+      sa->integ_sync_key_index = vnet_crypto_key_add (
+	vm, im->integ_algs[integ_alg].alg, (u8 *) ik->data, ik->len);
+      if (~0 == sa->integ_sync_key_index)
 	{
 	  pool_put (ipsec_sa_pool, sa);
 	  return VNET_API_ERROR_KEY_LENGTH;
 	}
     }
 
-  if (sa->async_op_data.crypto_async_enc_op_id &&
-      !ipsec_sa_is_set_IS_AEAD (sa))
-    {				//AES-CBC & HMAC
-      sa->async_op_data.linked_key_index =
-	vnet_crypto_key_add_linked (vm, sa->crypto_key_index,
-				    sa->integ_key_index);
-    }
+  if (sa->crypto_async_enc_op_id && !ipsec_sa_is_set_IS_AEAD (sa))
+    sa->crypto_async_key_index =
+      vnet_crypto_key_add_linked (vm, sa->crypto_sync_key_index,
+				  sa->integ_sync_key_index); // AES-CBC & HMAC
+  else
+    sa->crypto_async_key_index = sa->crypto_sync_key_index;
 
   if (im->async_mode)
-    sa->crypto_op_data = sa->async_op_data.data;
+    {
+      ipsec_sa_set_async_mode (sa, 1);
+    }
+  else if (ipsec_sa_is_set_IS_ASYNC (sa))
+    {
+      vnet_crypto_request_async_mode (1);
+      ipsec_sa_set_async_mode (sa, 1 /* is_enabled */);
+    }
   else
     {
-      if (ipsec_sa_is_set_IS_ASYNC (sa))
-	{
-	  vnet_crypto_request_async_mode (1);
-	  sa->crypto_op_data = sa->async_op_data.data;
-	}
-      else
-	sa->crypto_op_data = sa->sync_op_data.data;
+      ipsec_sa_set_async_mode (sa, 0 /* is_enabled */);
     }
 
   err = ipsec_check_support_cb (im, sa);
@@ -489,7 +508,7 @@ ipsec_sa_del (ipsec_sa_t * sa)
     {
       vnet_crypto_request_async_mode (0);
       if (!ipsec_sa_is_set_IS_AEAD (sa))
-	vnet_crypto_key_del (vm, sa->async_op_data.linked_key_index);
+	vnet_crypto_key_del (vm, sa->crypto_async_key_index);
     }
 
   if (ipsec_sa_is_set_UDP_ENCAP (sa) && ipsec_sa_is_set_IS_INBOUND (sa))
@@ -498,9 +517,9 @@ ipsec_sa_del (ipsec_sa_t * sa)
 
   if (ipsec_sa_is_set_IS_TUNNEL (sa) && !ipsec_sa_is_set_IS_INBOUND (sa))
     dpo_reset (&sa->dpo);
-  vnet_crypto_key_del (vm, sa->crypto_key_index);
+  vnet_crypto_key_del (vm, sa->crypto_sync_key_index);
   if (sa->integ_alg != IPSEC_INTEG_ALG_NONE)
-    vnet_crypto_key_del (vm, sa->integ_key_index);
+    vnet_crypto_key_del (vm, sa->integ_sync_key_index);
   pool_put (ipsec_sa_pool, sa);
 }
 
diff --git a/src/vnet/ipsec/ipsec_sa.h b/src/vnet/ipsec/ipsec_sa.h
index 4ef8f87dbef..ab1e3cdb1f9 100644
--- a/src/vnet/ipsec/ipsec_sa.h
+++ b/src/vnet/ipsec/ipsec_sa.h
@@ -16,11 +16,16 @@
 #define __IPSEC_SPD_SA_H__
 
 #include <vlib/vlib.h>
+#include <vppinfra/pcg.h>
 #include <vnet/crypto/crypto.h>
 #include <vnet/ip/ip.h>
 #include <vnet/fib/fib_node.h>
 #include <vnet/tunnel/tunnel.h>
 
+#define ESP_MAX_ICV_SIZE   (32)
+#define ESP_MAX_IV_SIZE	   (16)
+#define ESP_MAX_BLOCK_SIZE (16)
+
 #define foreach_ipsec_crypto_alg                                              \
   _ (0, NONE, "none")                                                         \
   _ (1, AES_CBC_128, "aes-cbc-128")                                           \
@@ -151,47 +156,27 @@ typedef struct
 {
   CLIB_CACHE_LINE_ALIGN_MARK (cacheline0);
 
-  /* flags */
-  ipsec_sa_flags_t flags;
-
-  u8 crypto_iv_size;
-  u8 esp_block_align;
-  u8 integ_icv_size;
-
-  u8 __pad1[3];
+  clib_pcg64i_random_t iv_prng;
 
-  u32 thread_index;
-
-  u32 spi;
-  u32 seq;
-  u32 seq_hi;
   u64 replay_window;
-  u64 iv_counter;
   dpo_id_t dpo;
 
   vnet_crypto_key_index_t crypto_key_index;
   vnet_crypto_key_index_t integ_key_index;
 
-  /* Union data shared by sync and async ops, updated when mode is
-   * changed. */
-  union
-  {
-    struct
-    {
-      vnet_crypto_op_id_t crypto_enc_op_id:16;
-      vnet_crypto_op_id_t crypto_dec_op_id:16;
-      vnet_crypto_op_id_t integ_op_id:16;
-    };
+  u32 spi;
+  u32 seq;
+  u32 seq_hi;
 
-    struct
-    {
-      vnet_crypto_async_op_id_t crypto_async_enc_op_id:16;
-      vnet_crypto_async_op_id_t crypto_async_dec_op_id:16;
-      vnet_crypto_key_index_t linked_key_index;
-    };
+  u16 crypto_enc_op_id;
+  u16 crypto_dec_op_id;
+  u16 integ_op_id;
+  ipsec_sa_flags_t flags;
+  u16 thread_index;
 
-    u64 crypto_op_data;
-  };
+  u16 integ_icv_size : 6;
+  u16 crypto_iv_size : 5;
+  u16 esp_block_align : 5;
 
   CLIB_CACHE_LINE_ALIGN_MARK (cacheline1);
 
@@ -213,30 +198,7 @@ typedef struct
     CLIB_CACHE_LINE_ALIGN_MARK (cacheline2);
 
   /* Elements with u64 size multiples */
-  union
-  {
-    struct
-    {
-      vnet_crypto_op_id_t crypto_enc_op_id:16;
-      vnet_crypto_op_id_t crypto_dec_op_id:16;
-      vnet_crypto_op_id_t integ_op_id:16;
-    };
-    u64 data;
-  } sync_op_data;
-
-  union
-  {
-    struct
-    {
-      vnet_crypto_async_op_id_t crypto_async_enc_op_id:16;
-      vnet_crypto_async_op_id_t crypto_async_dec_op_id:16;
-      vnet_crypto_key_index_t linked_key_index;
-    };
-    u64 data;
-  } async_op_data;
-
   tunnel_t tunnel;
-
   fib_node_t node;
 
   /* elements with u32 size */
@@ -244,6 +206,16 @@ typedef struct
   u32 stat_index;
   vnet_crypto_alg_t integ_calg;
   vnet_crypto_alg_t crypto_calg;
+  u32 crypto_sync_key_index;
+  u32 integ_sync_key_index;
+  u32 crypto_async_key_index;
+
+  /* elements with u16 size */
+  u16 crypto_sync_enc_op_id;
+  u16 crypto_sync_dec_op_id;
+  u16 integ_sync_op_id;
+  u16 crypto_async_enc_op_id;
+  u16 crypto_async_dec_op_id;
 
   /* else u8 packed */
   ipsec_crypto_alg_t crypto_alg;
@@ -253,6 +225,10 @@ typedef struct
   ipsec_key_t crypto_key;
 } ipsec_sa_t;
 
+STATIC_ASSERT (VNET_CRYPTO_N_OP_IDS < (1 << 16), "crypto ops overflow");
+STATIC_ASSERT (ESP_MAX_ICV_SIZE < (1 << 6), "integer icv overflow");
+STATIC_ASSERT (ESP_MAX_IV_SIZE < (1 << 5), "esp iv overflow");
+STATIC_ASSERT (ESP_MAX_BLOCK_SIZE < (1 << 5), "esp alignment overflow");
 STATIC_ASSERT_OFFSET_OF (ipsec_sa_t, cacheline1, CLIB_CACHE_LINE_BYTES);
 STATIC_ASSERT_OFFSET_OF (ipsec_sa_t, cacheline2, 2 * CLIB_CACHE_LINE_BYTES);
 
@@ -316,6 +292,7 @@ extern void ipsec_sa_set_crypto_alg (ipsec_sa_t * sa,
 				     ipsec_crypto_alg_t crypto_alg);
 extern void ipsec_sa_set_integ_alg (ipsec_sa_t * sa,
 				    ipsec_integ_alg_t integ_alg);
+extern void ipsec_sa_set_async_mode (ipsec_sa_t *sa, int is_enabled);
 
 typedef walk_rc_t (*ipsec_sa_walk_cb_t) (ipsec_sa_t * sa, void *ctx);
 extern void ipsec_sa_walk (ipsec_sa_walk_cb_t cd, void *ctx);
@@ -668,8 +645,8 @@ ipsec_sa_anti_replay_advance (ipsec_sa_t *sa, u32 thread_index, u32 seq,
  * Makes choice for thread_id should be assigned.
  *  if input ~0, gets random worker_id based on unix_time_now_nsec
 */
-always_inline u32
-ipsec_sa_assign_thread (u32 thread_id)
+always_inline u16
+ipsec_sa_assign_thread (u16 thread_id)
 {
   return ((thread_id) ? thread_id
 	  : (unix_time_now_nsec () % vlib_num_workers ()) + 1);