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authorBenoît Ganne <bganne@cisco.com>2022-01-18 15:56:41 +0100
committerBenoît Ganne <bganne@cisco.com>2023-02-06 17:03:39 +0100
commit752f6fe1b06e96f2c28bf846aadc79d8cdb0bdb1 (patch)
tree6cbfd63112e6e002ddd884cc4cf53a6a546cb1e0
parent3e0dafb74636671624a4168ea55c189c9e37929c (diff)
ipsec: fix AES CBC IV generation (CVE-2022-46397)stable/2001
For AES-CBC, the IV must be unpredictable (see NIST SP800-38a Appendix C). Chaining IVs like is done by ipsecmb and native backends for the VNET_CRYPTO_OP_FLAG_INIT_IV is fully predictable. Encrypt a counter as part of the message, making the (predictable) counter-generated IV unpredictable. Fixes: VPP-2037 Type: fix Change-Id: If4f192d62bf97dda553e7573331c75efa11822ae Signed-off-by: Benoît Ganne <bganne@cisco.com>
-rw-r--r--src/vnet/ipsec/esp_encrypt.c30
-rw-r--r--src/vnet/ipsec/ipsec_sa.h3
2 files changed, 28 insertions, 5 deletions
diff --git a/src/vnet/ipsec/esp_encrypt.c b/src/vnet/ipsec/esp_encrypt.c
index 3c2fdf4ec3c..8b3aac97a15 100644
--- a/src/vnet/ipsec/esp_encrypt.c
+++ b/src/vnet/ipsec/esp_encrypt.c
@@ -203,6 +203,24 @@ esp_get_ip6_hdr_len (ip6_header_t * ip6, ip6_ext_header_t ** ext_hdr)
return len;
}
+/* IPsec IV generation: IVs requirements differ depending of the
+ * 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. */
+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++;
+ return iv;
+}
+
static_always_inline void
esp_process_ops (vlib_main_t * vm, vlib_node_runtime_t * node,
vnet_crypto_op_t * ops, vlib_buffer_t * b[], u16 * nexts)
@@ -495,6 +513,7 @@ esp_encrypt_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
vnet_crypto_op_t *op;
vec_add2_aligned (ptd->crypto_ops, op, 1, CLIB_CACHE_LINE_BYTES);
vnet_crypto_op_init (op, sa0->crypto_enc_op_id);
+ void *pkt_iv = esp_generate_iv (sa0, payload, iv_sz);
op->src = op->dst = payload;
op->key_index = sa0->crypto_key_index;
op->len = payload_len - icv_sz;
@@ -513,16 +532,19 @@ esp_encrypt_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
op->tag = payload + op->len;
op->tag_len = 16;
- u64 *iv = (u64 *) (payload - iv_sz);
nonce->salt = sa0->salt;
- nonce->iv = *iv = clib_host_to_net_u64 (sa0->gcm_iv_counter++);
+ nonce->iv = *(u64 *) pkt_iv;
op->iv = (u8 *) nonce;
nonce++;
}
else
{
- op->iv = payload - iv_sz;
- op->flags = VNET_CRYPTO_OP_FLAG_INIT_IV;
+ /* construct zero iv in front of the IP header */
+ op->iv = pkt_iv - hdr_len - iv_sz;
+ clib_memset_u8 (op->iv, 0, iv_sz);
+ /* include iv field in crypto */
+ op->src -= iv_sz;
+ op->len += iv_sz;
}
}
diff --git a/src/vnet/ipsec/ipsec_sa.h b/src/vnet/ipsec/ipsec_sa.h
index e0d74e1309e..2468ea48998 100644
--- a/src/vnet/ipsec/ipsec_sa.h
+++ b/src/vnet/ipsec/ipsec_sa.h
@@ -133,6 +133,8 @@ typedef struct
/* data accessed by dataplane code should be above this comment */
CLIB_CACHE_LINE_ALIGN_MARK (cacheline1);
+ u64 iv_counter;
+
union
{
ip4_header_t ip4_hdr;
@@ -163,7 +165,6 @@ typedef struct
/* Salt used in GCM modes - stored in network byte order */
u32 salt;
- u64 gcm_iv_counter;
} ipsec_sa_t;
STATIC_ASSERT_OFFSET_OF (ipsec_sa_t, cacheline1, CLIB_CACHE_LINE_BYTES);