ipsec: fix AES CBC IV generation (CVE-2022-46397)
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>
diff --git a/src/vnet/ipsec/esp_encrypt.c b/src/vnet/ipsec/esp_encrypt.c
index 4d312be..aa0fb0a 100644
--- a/src/vnet/ipsec/esp_encrypt.c
+++ b/src/vnet/ipsec/esp_encrypt.c
@@ -215,6 +215,24 @@
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_chained_ops (vlib_main_t * vm, vlib_node_runtime_t * node,
vnet_crypto_op_t * ops, vlib_buffer_t * b[],
@@ -368,27 +386,29 @@
vnet_crypto_op_t *op;
vec_add2_aligned (crypto_ops[0], op, 1, CLIB_CACHE_LINE_BYTES);
vnet_crypto_op_init (op, sa0->crypto_enc_op_id);
+ u8 *crypto_start = payload;
+ /* esp_add_footer_and_icv() in esp_encrypt_inline() makes sure we always
+ * have enough space for ESP header and footer which includes ICV */
+ ASSERT (payload_len > icv_sz);
+ u16 crypto_len = payload_len - icv_sz;
- op->src = op->dst = payload;
+ /* generate the IV in front of the payload */
+ void *pkt_iv = esp_generate_iv (sa0, payload, iv_sz);
+
op->key_index = sa0->crypto_key_index;
- op->len = payload_len - icv_sz;
op->user_data = bi;
if (ipsec_sa_is_set_IS_CTR (sa0))
{
- ASSERT (sizeof (u64) == iv_sz);
/* construct nonce in a scratch space in front of the IP header */
esp_ctr_nonce_t *nonce =
- (esp_ctr_nonce_t *) (payload - sizeof (u64) - hdr_len -
- sizeof (*nonce));
- u64 *pkt_iv = (u64 *) (payload - sizeof (u64));
-
+ (esp_ctr_nonce_t *) (pkt_iv - hdr_len - sizeof (*nonce));
if (ipsec_sa_is_set_IS_AEAD (sa0))
{
/* constuct aad in a scratch space in front of the nonce */
op->aad = (u8 *) nonce - sizeof (esp_aead_t);
op->aad_len = esp_aad_fill (op->aad, esp, sa0, seq_hi);
- op->tag = payload + op->len;
+ op->tag = payload + crypto_len;
op->tag_len = 16;
}
else
@@ -397,13 +417,17 @@
}
nonce->salt = sa0->salt;
- nonce->iv = *pkt_iv = clib_host_to_net_u64 (sa0->ctr_iv_counter++);
+ nonce->iv = *(u64 *) pkt_iv;
op->iv = (u8 *) 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 */
+ crypto_start -= iv_sz;
+ crypto_len += iv_sz;
}
if (lb != b[0])
@@ -412,8 +436,15 @@
op->flags |= VNET_CRYPTO_OP_FLAG_CHAINED_BUFFERS;
op->chunk_index = vec_len (ptd->chunks);
op->tag = vlib_buffer_get_tail (lb) - icv_sz;
- esp_encrypt_chain_crypto (vm, ptd, sa0, b[0], lb, icv_sz, payload,
- payload_len, &op->n_chunks);
+ esp_encrypt_chain_crypto (vm, ptd, sa0, b[0], lb, icv_sz,
+ crypto_start, crypto_len + icv_sz,
+ &op->n_chunks);
+ }
+ else
+ {
+ /* not chained */
+ op->src = op->dst = crypto_start;
+ op->len = crypto_len;
}
}
@@ -463,26 +494,26 @@
u8 *tag, *iv, *aad = 0;
u8 flag = 0;
u32 key_index;
- i16 crypto_start_offset, integ_start_offset = 0;
+ i16 crypto_start_offset, integ_start_offset;
u16 crypto_total_len, integ_total_len;
post->next_index = next;
/* crypto */
- crypto_start_offset = payload - b->data;
+ crypto_start_offset = integ_start_offset = payload - b->data;
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);
+
if (ipsec_sa_is_set_IS_CTR (sa))
{
- ASSERT (sizeof (u64) == iv_sz);
/* construct nonce in a scratch space in front of the IP header */
- esp_ctr_nonce_t *nonce = (esp_ctr_nonce_t *) (payload - sizeof (u64) -
- hdr_len - sizeof (*nonce));
- u64 *pkt_iv = (u64 *) (payload - sizeof (u64));
-
+ esp_ctr_nonce_t *nonce =
+ (esp_ctr_nonce_t *) (pkt_iv - hdr_len - sizeof (*nonce));
if (ipsec_sa_is_set_IS_AEAD (sa))
{
/* constuct aad in a scratch space in front of the nonce */
@@ -496,13 +527,17 @@
}
nonce->salt = sa->salt;
- nonce->iv = *pkt_iv = clib_host_to_net_u64 (sa->ctr_iv_counter++);
+ nonce->iv = *(u64 *) pkt_iv;
iv = (u8 *) nonce;
}
else
{
- iv = payload - iv_sz;
- flag |= VNET_CRYPTO_OP_FLAG_INIT_IV;
+ /* construct zero iv in front of the IP header */
+ iv = pkt_iv - hdr_len - iv_sz;
+ clib_memset_u8 (iv, 0, iv_sz);
+ /* include iv field in crypto */
+ crypto_start_offset -= iv_sz;
+ crypto_total_len += iv_sz;
}
if (lb != b)
@@ -510,13 +545,14 @@
/* chain */
flag |= VNET_CRYPTO_OP_FLAG_CHAINED_BUFFERS;
tag = vlib_buffer_get_tail (lb) - icv_sz;
- crypto_total_len = esp_encrypt_chain_crypto (vm, ptd, sa, b, lb, icv_sz,
- payload, payload_len, 0);
+ crypto_total_len = esp_encrypt_chain_crypto (
+ vm, ptd, sa, b, lb, icv_sz, b->data + crypto_start_offset,
+ crypto_total_len + icv_sz, 0);
}
if (sa->integ_op_id)
{
- integ_start_offset = crypto_start_offset - iv_sz - sizeof (esp_header_t);
+ integ_start_offset -= iv_sz + sizeof (esp_header_t);
integ_total_len += iv_sz + sizeof (esp_header_t);
if (b != lb)
diff --git a/src/vnet/ipsec/ipsec_sa.h b/src/vnet/ipsec/ipsec_sa.h
index df079b1..88d5c42 100644
--- a/src/vnet/ipsec/ipsec_sa.h
+++ b/src/vnet/ipsec/ipsec_sa.h
@@ -137,7 +137,7 @@
u32 seq;
u32 seq_hi;
u64 replay_window;
- u64 ctr_iv_counter;
+ u64 iv_counter;
dpo_id_t dpo;
vnet_crypto_key_index_t crypto_key_index;