VPP-1522: harden reassembly code

Change-Id: Ib5a20bff7d8a340ecf50bcd4a023d6bf36382ba3
Signed-off-by: Klement Sekera <ksekera@cisco.com>

5 files changed, 85 insertions, 43 deletions

diff --git a/src/vnet/ip/ip4_error.h b/src/vnet/ip/ip4_error.h
index 52c43adb12c..15828e39ac5 100644
--- a/src/vnet/ip/ip4_error.h
+++ b/src/vnet/ip/ip4_error.h
@@ -86,7 +86,8 @@
   /* Errors signalled by ip4-reassembly */                              \
   _ (REASS_DUPLICATE_FRAGMENT, "duplicate/overlapping fragments")       \
   _ (REASS_LIMIT_REACHED, "drops due to concurrent reassemblies limit") \
-  _ (REASS_TIMEOUT, "fragments dropped due to reassembly timeout")
+  _ (REASS_TIMEOUT, "fragments dropped due to reassembly timeout")      \
+  _ (REASS_MALFORMED_PACKET, "malformed packets")
 
 typedef enum
 {
diff --git a/src/vnet/ip/ip4_reassembly.c b/src/vnet/ip/ip4_reassembly.c
index bd33026db85..9bcc20a2285 100644
--- a/src/vnet/ip/ip4_reassembly.c
+++ b/src/vnet/ip/ip4_reassembly.c
@@ -654,12 +654,12 @@ ip4_reass_update (vlib_main_t * vm, vlib_node_runtime_t * node,
   ASSERT (fb->current_length >= sizeof (*fip));
   vnet_buffer_opaque_t *fvnb = vnet_buffer (fb);
   reass->next_index = fvnb->ip.reass.next_index;	// store next_index before it's overwritten
-  u32 fragment_first = fvnb->ip.reass.fragment_first =
-    ip4_get_fragment_offset_bytes (fip);
-  u32 fragment_length =
+  const u32 fragment_first = ip4_get_fragment_offset_bytes (fip);
+  const u32 fragment_length =
     clib_net_to_host_u16 (fip->length) - ip4_header_bytes (fip);
-  u32 fragment_last = fvnb->ip.reass.fragment_last =
-    fragment_first + fragment_length - 1;
+  const u32 fragment_last = fragment_first + fragment_length - 1;
+  fvnb->ip.reass.fragment_first = fragment_first;
+  fvnb->ip.reass.fragment_last = fragment_last;
   int more_fragments = ip4_get_fragment_more (fip);
   u32 candidate_range_bi = reass->first_bi;
   u32 prev_range_bi = ~0;
@@ -927,28 +927,43 @@ ip4_reassembly_inline (vlib_main_t * vm,
 	    }
 	  else
 	    {
-	      ip4_reass_key_t k;
-	      k.as_u64[0] =
-		(u64) vnet_buffer (b0)->sw_if_index[VLIB_RX] << 32 | (u64)
-		ip0->src_address.as_u32;
-	      k.as_u64[1] =
-		(u64) ip0->dst_address.
-		as_u32 << 32 | (u64) ip0->fragment_id << 16 | (u64) ip0->
-		protocol << 8;
-
-	      ip4_reass_t *reass =
-		ip4_reass_find_or_create (vm, rm, rt, &k, &vec_drop_timeout);
-
-	      if (reass)
+	      ip4_header_t *fip = vlib_buffer_get_current (b0);
+	      const u32 fragment_first = ip4_get_fragment_offset_bytes (fip);
+	      const u32 fragment_length =
+		clib_net_to_host_u16 (fip->length) - ip4_header_bytes (fip);
+	      const u32 fragment_last = fragment_first + fragment_length - 1;
+	      if (fragment_first > fragment_last
+		  || fragment_first + fragment_length > UINT16_MAX - 20)
 		{
-		  ip4_reass_update (vm, node, rm, rt, reass, &bi0, &next0,
-				    &error0, &vec_drop_overlap,
-				    &vec_drop_compress, is_feature);
+		  next0 = IP4_REASSEMBLY_NEXT_DROP;
+		  error0 = IP4_ERROR_REASS_MALFORMED_PACKET;
 		}
 	      else
 		{
-		  next0 = IP4_REASSEMBLY_NEXT_DROP;
-		  error0 = IP4_ERROR_REASS_LIMIT_REACHED;
+		  ip4_reass_key_t k;
+		  k.as_u64[0] =
+		    (u64) vnet_buffer (b0)->sw_if_index[VLIB_RX] << 32 | (u64)
+		    ip0->src_address.as_u32;
+		  k.as_u64[1] =
+		    (u64) ip0->dst_address.
+		    as_u32 << 32 | (u64) ip0->fragment_id << 16 | (u64) ip0->
+		    protocol << 8;
+
+		  ip4_reass_t *reass =
+		    ip4_reass_find_or_create (vm, rm, rt, &k,
+					      &vec_drop_timeout);
+
+		  if (reass)
+		    {
+		      ip4_reass_update (vm, node, rm, rt, reass, &bi0, &next0,
+					&error0, &vec_drop_overlap,
+					&vec_drop_compress, is_feature);
+		    }
+		  else
+		    {
+		      next0 = IP4_REASSEMBLY_NEXT_DROP;
+		      error0 = IP4_ERROR_REASS_LIMIT_REACHED;
+		    }
 		}
 
 	      b0->error = node->errors[error0];
diff --git a/test/framework.py b/test/framework.py
index f82f0750387..859010cf325 100644
--- a/test/framework.py
+++ b/test/framework.py
@@ -916,15 +916,18 @@ class VppTestCase(unittest.TestCase):
             self.assert_checksum_valid(pkt, 'ICMPv6EchoReply', 'cksum')
 
     def assert_packet_counter_equal(self, counter, expected_value):
-        counters = self.vapi.cli("sh errors").split('\n')
-        counter_value = -1
-        for i in range(1, len(counters)):
-            results = counters[i].split()
-            if results[1] == counter:
-                counter_value = int(results[0])
-                break
-        self.assert_equal(counter_value, expected_value,
-                          "packet counter `%s'" % counter)
+        if counter.startswith("/"):
+            counter_value = self.statistics.get_counter(counter)
+            self.assert_equal(counter_value, expected_value,
+                              "packet counter `%s'" % counter)
+        else:
+            counters = self.vapi.cli("sh errors").split('\n')
+            counter_value = -1
+            for i in range(1, len(counters) - 1):
+                results = counters[i].split()
+                if results[1] == counter:
+                    counter_value = int(results[0])
+                    break
 
     @classmethod
     def sleep(cls, timeout, remark=None):
diff --git a/test/template_ipsec.py b/test/template_ipsec.py
index 961f63aa59c..d35cf420d37 100644
--- a/test/template_ipsec.py
+++ b/test/template_ipsec.py
@@ -233,9 +233,8 @@ class IpsecTraTests(object):
                                       seq_num=17))
         self.send_and_assert_no_replies(self.tra_if, pkt * 17)
 
-        err = self.statistics.get_counter(
-            '/err/%s/SA replayed packet' % self.tra4_decrypt_node_name)
-        self.assertEqual(err, 17)
+        self.assert_packet_counter_equal(
+            '/err/%s/SA replayed packet' % self.tra4_decrypt_node_name, 17)
 
         # a packet that does not decrypt does not move the window forward
         bogus_sa = SecurityAssociation(self.encryption_type,
@@ -248,9 +247,8 @@ class IpsecTraTests(object):
                                 seq_num=350))
         self.send_and_assert_no_replies(self.tra_if, pkt * 17)
 
-        err = self.statistics.get_counter(
-            '/err/%s/Integrity check failed' % self.tra4_decrypt_node_name)
-        self.assertEqual(err, 17)
+        self.assert_packet_counter_equal(
+            '/err/%s/Integrity check failed' % self.tra4_decrypt_node_name, 17)
 
         # which we can determine since this packet is still in the window
         pkt = (Ether(src=self.tra_if.remote_mac,
@@ -259,7 +257,7 @@ class IpsecTraTests(object):
                                          dst=self.tra_if.local_ip4) /
                                       ICMP(),
                                       seq_num=234))
-        recv_pkts = self.send_and_expect(self.tra_if, [pkt], self.tra_if)
+        self.send_and_expect(self.tra_if, [pkt], self.tra_if)
 
         # move the security-associations seq number on to the last we used
         p.scapy_tra_sa.seq_num = 351
diff --git a/test/test_reassembly.py b/test/test_reassembly.py
index 0c11d9b3ce8..65a5eb0914d 100644
--- a/test/test_reassembly.py
+++ b/test/test_reassembly.py
@@ -178,6 +178,31 @@ class TestIPv4Reassembly(VppTestCase):
         self.verify_capture(packets)
         self.src_if.assert_nothing_captured()
 
+    def test_5737(self):
+        """ fragment length + ip header size > 65535 """
+        raw = ('E\x00\x00\x88,\xf8\x1f\xfe@\x01\x98\x00\xc0\xa8\n-\xc0\xa8\n'
+               '\x01\x08\x00\xf0J\xed\xcb\xf1\xf5Test-group: IPv4.IPv4.ipv4-'
+               'message.Ethernet-Payload.IPv4-Packet.IPv4-Header.Fragment-Of'
+               'fset; Test-case: 5737')
+
+        malformed_packet = (Ether(dst=self.src_if.local_mac,
+                                  src=self.src_if.remote_mac) /
+                            IP(raw))
+        p = (Ether(dst=self.src_if.local_mac, src=self.src_if.remote_mac) /
+             IP(id=1000, src=self.src_if.remote_ip4,
+                dst=self.dst_if.remote_ip4) /
+             UDP(sport=1234, dport=5678) /
+             Raw("X" * 1000))
+        valid_fragments = fragment_rfc791(p, 400)
+
+        self.pg_enable_capture()
+        self.src_if.add_stream([malformed_packet] + valid_fragments)
+        self.pg_start()
+
+        self.dst_if.get_capture(1)
+        self.assert_packet_counter_equal(
+            "/err/ip4-reassembly-feature/malformed packets", 1)
+
     @unittest.skipIf(is_skip_aarch64_set() and is_platform_aarch64(),
                      "test doesn't work on aarch64")
     def test_random(self):
@@ -838,7 +863,7 @@ class TestIPv4ReassemblyLocalNode(VppTestCase):
                 seen.add(packet_index)
                 self.assertEqual(payload_info.dst, self.src_dst_if.sw_if_index)
                 info = self._packet_infos[packet_index]
-                self.assertTrue(info is not None)
+                self.assertIsNotNone(info)
                 self.assertEqual(packet_index, info.index)
                 saved_packet = info.data
                 self.assertEqual(ip.src, saved_packet[IP].dst)
@@ -850,8 +875,8 @@ class TestIPv4ReassemblyLocalNode(VppTestCase):
                 self.logger.error(ppp("Unexpected or invalid packet:", packet))
                 raise
         for index in self._packet_infos:
-            self.assertTrue(index in seen or index in dropped_packet_indexes,
-                            "Packet with packet_index %d not received" % index)
+            self.assertIn(index, seen,
+                          "Packet with packet_index %d not received" % index)
 
     def test_reassembly(self):
         """ basic reassembly """