lib.ipsec.esp: More thourough testing of the anti-replay facilities

src/lib/ipsec/esp.lua

@@ -193,9 +193,6 @@ ABCDEFGHIJKLMNOPQRSTUVWXYZ
    assert(packet.length(p2) == packet.length(p)
           and C.memcmp(p, p2, packet.length(p)) == 0,
           "integrity check failed")
-   -- Check replayed packet XXX do this a lot more thoroughly
-   p2 = packet.clone(p_enc)
-   assert(not dec:decapsulate(p2), "replayed decapsulation succeeded")
    -- Check invalid packets.
    local p_invalid = packet.from_string("invalid")
    assert(not enc:encapsulate(p_invalid), "encapsulated invalid packet")
@@ -218,27 +215,66 @@ ABCDEFGHIJKLMNOPQRSTUVWXYZ
           and C.memcmp(p_min, e_min, packet.length(p_min)) == 0,
           "integrity check failed")
    -- Check transmitted Sequence Number wrap around
-   enc.seq:low(0)
-   enc.seq:high(1)
-   dec.seq:low(2^32 - dec.window_size)
-   dec.seq:high(0)
-   C.track_seq_no(dec.seq:high(), dec.seq:low(), dec.seq.no, dec.window, dec.window_size)
-   local p3 = packet.clone(p)
-   enc:encapsulate(p3)
-   assert(dec:decapsulate(p3),
+   C.memset(dec.window, 0, dec.window_size / 8); -- clear window
+   enc.seq.no = 2^32 - 1 -- so next encapsulated will be seq 2^32
+   dec.seq.no = 2^32 - 1 -- pretend to have seen 2^32-1
+   local px = packet.clone(p)
+   enc:encapsulate(px)
+   assert(dec:decapsulate(px),
           "Transmitted Sequence Number wrap around failed.")
-   assert(dec.seq:high() == 1 and dec.seq:low() == 1,
+   assert(dec.seq:high() == 1 and dec.seq:low() == 0,
           "Lost Sequence Number synchronization.")
    -- Check Sequence Number exceeding window
-   enc.seq:low(0)
-   enc.seq:high(1)
-   dec.seq:low(dec.window_size+1)
-   dec.seq:high(1)
-   C.track_seq_no(dec.seq:high(), dec.seq:low(), dec.seq.no, dec.window, dec.window_size)
-   local p4 = packet.clone(p)
-   enc:encapsulate(p4)
-   assert(not dec:decapsulate(p4),
+   C.memset(dec.window, 0, dec.window_size / 8); -- clear window
+   enc.seq.no = 2^32
+   dec.seq.no = 2^32 + dec.window_size + 1
+   px = packet.clone(p)
+   enc:encapsulate(px)
+   assert(not dec:decapsulate(px),
           "Accepted out of window Sequence Number.")
    assert(dec.seq:high() == 1 and dec.seq:low() == dec.window_size+1,
           "Corrupted Sequence Number.")
+   -- Test anti-replay: From a set of 15 packets, first send all those
+   -- that have an even sequence number.  Then, send all 15.  Verify that
+   -- in the 2nd run, packets with even sequence numbers are rejected while
+   -- the others are not.
+   -- Then do the same thing again, but with offset sequence numbers so that
+   -- we have a 32bit wraparound in the middle.
+   local offset = 0 -- close to 2^32 in the 2nd iteration
+   for offset = 0, 2^32-7, 2^32-7 do -- duh
+      C.memset(dec.window, 0, dec.window_size / 8); -- clear window
+      dec.seq.no = offset
+      for i = 1+offset, 15+offset do
+         if (i % 2 == 0) then
+            enc.seq.no = i-1 -- so next seq will be i
+            px = packet.clone(p)
+            enc:encapsulate(px);
+            assert(dec:decapsulate(px), "rejected legitimate packet seq=" .. i)
+            assert(dec.seq.no == i, "Lost sequence number synchronization")
+         end
+      end
+      for i = 1+offset, 15+offset do
+         enc.seq.no = i-1
+         px = packet.clone(p)
+         enc:encapsulate(px);
+         if (i % 2 == 0) then
+            assert(not dec:decapsulate(px), "accepted replayed packet seq=" .. i)
+         else
+            assert(dec:decapsulate(px), "rejected legitimate packet seq=" .. i)
+         end
+      end
+   end
+   -- Check that packets from way in the past/way in the future
+   -- (further than the biggest allowable window size) are rejected
+   -- This is where we ultimately want resynchronation (wrt. future packets)
+   C.memset(dec.window, 0, dec.window_size / 8); -- clear window
+   dec.seq.no = 2^34 + 42;
+   enc.seq.no = 2^36 + 42;
+   px = packet.clone(p)
+   enc:encapsulate(px);
+   assert(not dec:decapsulate(px), "accepted packet from way into the future")
+   enc.seq.no = 2^32 + 42;
+   px = packet.clone(p)
+   enc:encapsulate(px);
+   assert(not dec:decapsulate(px), "accepted packet from way into the past")
 end