#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") \
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;
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))
+ {
+ /*
+ * 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
{
+ /*
+ * 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
- {
- sa->seq_hi = th + 1;
- 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;
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