ipsec: GCM, Anti-replay and ESN fixess
Type: fix
Several Fixes:
1 - Anti-replay did not work with GCM becuase it overwrote the sequence
number in the ESP header. To fix i added the seq num to the per-packet
data so it is preserved
2 - The high sequence number was not byte swapped during ESP encrypt.
3 - openssl engine was the only one to return FAIL_DECRYPT for bad GCM
the others return BAD_HMAC. removed the former
4 - improved tracing to show the low and high seq numbers
5 - documented the anti-replay window checks
6 - fixed scapy patch for ESN support for GCM
7 - tests for anti-reply (w/ and w/o ESN) for each crypto algo
Change-Id: Id65d96b6d1d4dd821b2ab557e87468fff6d70e5b
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/src/vnet/ipsec/ah_decrypt.c b/src/vnet/ipsec/ah_decrypt.c
index 741fa91..bc6b5c4 100644
--- a/src/vnet/ipsec/ah_decrypt.c
+++ b/src/vnet/ipsec/ah_decrypt.c
@@ -203,7 +203,7 @@
pd->seq = clib_host_to_net_u32 (ah0->seq_no);
/* anti-replay check */
- if (ipsec_sa_anti_replay_check (sa0, &ah0->seq_no))
+ if (ipsec_sa_anti_replay_check (sa0, pd->seq))
{
b[0]->error = node->errors[AH_DECRYPT_ERROR_REPLAY];
next[0] = AH_DECRYPT_NEXT_DROP;
@@ -303,7 +303,7 @@
if (PREDICT_TRUE (sa0->integ_alg != IPSEC_INTEG_ALG_NONE))
{
- ipsec_sa_anti_replay_advance (sa0, clib_host_to_net_u32 (pd->seq));
+ ipsec_sa_anti_replay_advance (sa0, pd->seq);
}
u16 ah_hdr_len = sizeof (ah_header_t) + pd->icv_size
diff --git a/src/vnet/ipsec/esp_decrypt.c b/src/vnet/ipsec/esp_decrypt.c
index 48f08f4..c2b9bf4 100644
--- a/src/vnet/ipsec/esp_decrypt.c
+++ b/src/vnet/ipsec/esp_decrypt.c
@@ -67,6 +67,8 @@
typedef struct
{
u32 seq;
+ u32 sa_seq;
+ u32 sa_seq_hi;
ipsec_crypto_alg_t crypto_alg;
ipsec_integ_alg_t integ_alg;
} esp_decrypt_trace_t;
@@ -79,9 +81,11 @@
CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
esp_decrypt_trace_t *t = va_arg (*args, esp_decrypt_trace_t *);
- s = format (s, "esp: crypto %U integrity %U seq %u",
- format_ipsec_crypto_alg, t->crypto_alg,
- format_ipsec_integ_alg, t->integ_alg, t->seq);
+ s =
+ format (s,
+ "esp: crypto %U integrity %U pkt-seq %d sa-seq %u sa-seq-hi %u",
+ format_ipsec_crypto_alg, t->crypto_alg, format_ipsec_integ_alg,
+ t->integ_alg, t->seq, t->sa_seq, t->sa_seq_hi);
return s;
}
@@ -99,12 +103,13 @@
u64 sa_data;
};
+ u32 seq;
i16 current_data;
i16 current_length;
u16 hdr_sz;
} esp_decrypt_packet_data_t;
-STATIC_ASSERT_SIZEOF (esp_decrypt_packet_data_t, 2 * sizeof (u64));
+STATIC_ASSERT_SIZEOF (esp_decrypt_packet_data_t, 3 * sizeof (u64));
#define ESP_ENCRYPT_PD_F_FD_TRANSPORT (1 << 2)
@@ -177,6 +182,7 @@
pd->current_length = b[0]->current_length;
pd->hdr_sz = pd->current_data - vnet_buffer (b[0])->l3_hdr_offset;
payload = b[0]->data + pd->current_data;
+ pd->seq = clib_host_to_net_u32 (((esp_header_t *) payload)->seq);
/* we need 4 extra bytes for HMAC calculation when ESN are used */
if (ipsec_sa_is_set_USE_ESN (sa0) && pd->icv_sz &&
@@ -188,7 +194,7 @@
}
/* anti-reply check */
- if (ipsec_sa_anti_replay_check (sa0, &((esp_header_t *) payload)->seq))
+ if (ipsec_sa_anti_replay_check (sa0, pd->seq))
{
b[0]->error = node->errors[ESP_DECRYPT_ERROR_REPLAY];
next[0] = ESP_DECRYPT_NEXT_DROP;
@@ -221,10 +227,11 @@
op->len = len;
if (ipsec_sa_is_set_USE_ESN (sa0))
{
- /* shift ICV for 4 bytes to insert ESN */
+ /* shift ICV by 4 bytes to insert ESN */
+ u32 seq_hi = clib_host_to_net_u32 (sa0->seq_hi);
u8 tmp[ESP_MAX_ICV_SIZE], sz = sizeof (sa0->seq_hi);
clib_memcpy_fast (tmp, payload + len, ESP_MAX_ICV_SIZE);
- clib_memcpy_fast (payload + len, &sa0->seq_hi, sz);
+ clib_memcpy_fast (payload + len, &seq_hi, sz);
clib_memcpy_fast (payload + len + sz, tmp, ESP_MAX_ICV_SIZE);
op->len += sz;
op->digest += sz;
@@ -368,9 +375,8 @@
goto trace;
sa0 = vec_elt_at_index (im->sad, pd->sa_index);
- u8 *payload = b[0]->data + pd->current_data;
- ipsec_sa_anti_replay_advance (sa0, ((esp_header_t *) payload)->seq);
+ ipsec_sa_anti_replay_advance (sa0, pd->seq);
esp_footer_t *f = (esp_footer_t *) (b[0]->data + pd->current_data +
pd->current_length - sizeof (*f) -
@@ -485,13 +491,14 @@
if (PREDICT_FALSE (b[0]->flags & VLIB_BUFFER_IS_TRACED))
{
esp_decrypt_trace_t *tr;
- u8 *payload = b[0]->data + pd->current_data;
tr = vlib_add_trace (vm, node, b[0], sizeof (*tr));
sa0 = pool_elt_at_index (im->sad,
vnet_buffer (b[0])->ipsec.sad_index);
tr->crypto_alg = sa0->crypto_alg;
tr->integ_alg = sa0->integ_alg;
- tr->seq = clib_host_to_net_u32 (((esp_header_t *) payload)->seq);
+ tr->seq = pd->seq;
+ tr->sa_seq = sa0->last_seq;
+ tr->sa_seq_hi = sa0->seq_hi;
}
/* next */
diff --git a/src/vnet/ipsec/esp_encrypt.c b/src/vnet/ipsec/esp_encrypt.c
index 041b268..47c079d 100644
--- a/src/vnet/ipsec/esp_encrypt.c
+++ b/src/vnet/ipsec/esp_encrypt.c
@@ -65,6 +65,7 @@
u32 sa_index;
u32 spi;
u32 seq;
+ u32 sa_seq_hi;
u8 udp_encap;
ipsec_crypto_alg_t crypto_alg;
ipsec_integ_alg_t integ_alg;
@@ -80,8 +81,9 @@
s =
format (s,
- "esp: sa-index %d spi %u (0x%08x) seq %u crypto %U integrity %U%s",
- t->sa_index, t->spi, t->spi, t->seq, format_ipsec_crypto_alg,
+ "esp: sa-index %d spi %u (0x%08x) seq %u sa-seq-hi %u crypto %U integrity %U%s",
+ t->sa_index, t->spi, t->spi, t->seq, t->sa_seq_hi,
+ format_ipsec_crypto_alg,
t->crypto_alg, format_ipsec_integ_alg, t->integ_alg,
t->udp_encap ? " udp-encap-enabled" : "");
return s;
@@ -521,7 +523,8 @@
sizeof (*tr));
tr->sa_index = sa_index0;
tr->spi = sa0->spi;
- tr->seq = sa0->seq - 1;
+ tr->seq = sa0->seq;
+ tr->sa_seq_hi = sa0->seq_hi;
tr->udp_encap = ipsec_sa_is_set_UDP_ENCAP (sa0);
tr->crypto_alg = sa0->crypto_alg;
tr->integ_alg = sa0->integ_alg;
diff --git a/src/vnet/ipsec/ipsec_sa.h b/src/vnet/ipsec/ipsec_sa.h
index 811f4ca..86d76b3 100644
--- a/src/vnet/ipsec/ipsec_sa.h
+++ b/src/vnet/ipsec/ipsec_sa.h
@@ -19,8 +19,6 @@
#include <vnet/ip/ip.h>
#include <vnet/fib/fib_node.h>
-#define IPSEC_SA_ANTI_REPLAY_WINDOW_SIZE (64)
-
#define foreach_ipsec_crypto_alg \
_ (0, NONE, "none") \
_ (1, AES_CBC_128, "aes-cbc-128") \
@@ -232,18 +230,34 @@
va_list * args);
extern uword unformat_ipsec_key (unformat_input_t * input, va_list * args);
+/*
+ * Anti Replay definitions
+ */
+
+#define IPSEC_SA_ANTI_REPLAY_WINDOW_SIZE (64)
+#define IPSEC_SA_ANTI_REPLAY_WINDOW_MAX_INDEX (IPSEC_SA_ANTI_REPLAY_WINDOW_SIZE-1)
+
+/*
+ * sequence number less than the lower bound are outside of the window
+ * From RFC4303 Appendix A:
+ * Bl = Tl - W + 1
+ */
+#define IPSEC_SA_ANTI_REPLAY_WINDOW_LOWER_BOUND(_tl) (_tl - IPSEC_SA_ANTI_REPLAY_WINDOW_SIZE + 1)
+
+/*
+ * Anti replay check.
+ * inputs need to be in host byte order.
+ */
always_inline int
-ipsec_sa_anti_replay_check (ipsec_sa_t * sa, u32 * seqp)
+ipsec_sa_anti_replay_check (ipsec_sa_t * sa, u32 seq)
{
- u32 seq, diff, tl, th;
+ u32 diff, tl, th;
+
if ((sa->flags & IPSEC_SA_FLAG_USE_ANTI_REPLAY) == 0)
return 0;
- seq = clib_net_to_host_u32 (*seqp);
-
- if ((sa->flags & IPSEC_SA_FLAG_USE_ESN) == 0)
+ if (!ipsec_sa_is_set_USE_ESN (sa))
{
-
if (PREDICT_TRUE (seq > sa->last_seq))
return 0;
@@ -261,50 +275,113 @@
th = sa->last_seq_hi;
diff = tl - seq;
- if (PREDICT_TRUE (tl >= (IPSEC_SA_ANTI_REPLAY_WINDOW_SIZE - 1)))
+ if (PREDICT_TRUE (tl >= (IPSEC_SA_ANTI_REPLAY_WINDOW_MAX_INDEX)))
{
- if (seq >= (tl - IPSEC_SA_ANTI_REPLAY_WINDOW_SIZE + 1))
+ /*
+ * the last sequence number VPP recieved is more than one
+ * window size greater than zero.
+ * Case A from RFC4303 Appendix A.
+ */
+ if (seq < IPSEC_SA_ANTI_REPLAY_WINDOW_LOWER_BOUND (tl))
{
- sa->seq_hi = th;
- if (seq <= tl)
- return (sa->replay_window & (1ULL << diff)) ? 1 : 0;
- else
- return 0;
+ /*
+ * the received sequence number is lower than the lower bound
+ * of the window, this could mean either a replay packet or that
+ * the high sequence number has wrapped. if it decrypts corrently
+ * then it's the latter.
+ */
+ sa->seq_hi = th + 1;
+ return 0;
}
else
{
- sa->seq_hi = th + 1;
- return 0;
+ /*
+ * the recieved sequence number greater than the low
+ * end of the window.
+ */
+ sa->seq_hi = th;
+ if (seq <= tl)
+ /*
+ * The recieved seq number is within bounds of the window
+ * check if it's a duplicate
+ */
+ return (sa->replay_window & (1ULL << diff)) ? 1 : 0;
+ else
+ /*
+ * The received sequence number is greater than the window
+ * upper bound. this packet will move the window along, assuming
+ * it decrypts correctly.
+ */
+ return 0;
}
}
else
{
- if (seq >= (tl - IPSEC_SA_ANTI_REPLAY_WINDOW_SIZE + 1))
+ /*
+ * the last sequence number VPP recieved is within one window
+ * size of zero, i.e. 0 < TL < WINDOW_SIZE, the lower bound is thus a
+ * large sequence number.
+ * Note that the check below uses unsiged integer arthimetic, so the
+ * RHS will be a larger number.
+ * Case B from RFC4303 Appendix A.
+ */
+ if (seq < IPSEC_SA_ANTI_REPLAY_WINDOW_LOWER_BOUND (tl))
{
- sa->seq_hi = th - 1;
- return (sa->replay_window & (1ULL << diff)) ? 1 : 0;
+ /*
+ * the sequence number is less than the lower bound.
+ */
+ if (seq <= tl)
+ {
+ /*
+ * the packet is within the window upper bound.
+ * check for duplicates.
+ */
+ sa->seq_hi = th;
+ return (sa->replay_window & (1ULL << diff)) ? 1 : 0;
+ }
+ else
+ {
+ /*
+ * the packet is less the window lower bound or greater than
+ * the higher bound, depending on how you look at it...
+ * We're assuming, given that the last sequence number received,
+ * TL < WINDOW_SIZE, that a largeer seq num is more likely to be
+ * a packet that moves the window forward, than a packet that has
+ * wrapped the high sequence again. If it were the latter then
+ * we've lost close to 2^32 packets.
+ */
+ sa->seq_hi = th;
+ return 0;
+ }
}
else
{
- sa->seq_hi = th;
- if (seq <= tl)
- return (sa->replay_window & (1ULL << diff)) ? 1 : 0;
- else
- return 0;
+ /*
+ * the packet seq number is between the lower bound (a large nubmer)
+ * and MAX_SEQ_NUM. This is in the window since the window upper bound
+ * tl > 0.
+ * However, since TL is the other side of 0 to the received
+ * packet, the SA has moved on to a higher sequence number.
+ */
+ sa->seq_hi = th - 1;
+ return (sa->replay_window & (1ULL << diff)) ? 1 : 0;
}
}
return 0;
}
+/*
+ * Anti replay window advance
+ * inputs need to be in host byte order.
+ */
always_inline void
-ipsec_sa_anti_replay_advance (ipsec_sa_t * sa, u32 seqp)
+ipsec_sa_anti_replay_advance (ipsec_sa_t * sa, u32 seq)
{
- u32 pos, seq;
+ u32 pos;
if (PREDICT_TRUE (sa->flags & IPSEC_SA_FLAG_USE_ANTI_REPLAY) == 0)
return;
- seq = clib_host_to_net_u32 (seqp);
if (PREDICT_TRUE (sa->flags & IPSEC_SA_FLAG_USE_ESN))
{
int wrap = sa->seq_hi - sa->last_seq_hi;