reassembly: prevent long chain attack
limit max # of fragments to 3 per packet by default
add API option to configure the limit at runtime
Change-Id: Ie4b9507bf5c6095b9a5925972b37fe0032f4f9e8
Signed-off-by: Klement Sekera <ksekera@cisco.com>
diff --git a/src/vnet/ip/ip6_reassembly.c b/src/vnet/ip/ip6_reassembly.c
index 9906250..45cd2b2 100644
--- a/src/vnet/ip/ip6_reassembly.c
+++ b/src/vnet/ip/ip6_reassembly.c
@@ -30,12 +30,14 @@
#define IP6_REASS_TIMEOUT_DEFAULT_MS 100
#define IP6_REASS_EXPIRE_WALK_INTERVAL_DEFAULT_MS 10000 // 10 seconds default
#define IP6_REASS_MAX_REASSEMBLIES_DEFAULT 1024
+#define IP6_REASS_MAX_REASSEMBLY_LENGTH_DEFAULT 3
#define IP6_REASS_HT_LOAD_FACTOR (0.75)
typedef enum
{
IP6_REASS_RC_OK,
IP6_REASS_RC_INTERNAL_ERROR,
+ IP6_REASS_RC_TOO_MANY_FRAGMENTS,
IP6_REASS_RC_NO_BUF,
} ip6_reass_rc_t;
@@ -112,6 +114,8 @@
u8 next_index;
// minimum fragment length for this reassembly - used to estimate MTU
u16 min_fragment_length;
+ // number of fragments for this reassembly
+ u32 fragments_n;
} ip6_reass_t;
typedef struct
@@ -128,6 +132,9 @@
u32 timeout_ms;
f64 timeout;
u32 expire_walk_interval_ms;
+ // maximum number of fragments in one reassembly
+ u32 max_reass_len;
+ // maximum number of reassemblies
u32 max_reass_n;
// IPv6 runtime
@@ -744,6 +751,7 @@
*bi0);
reass->min_fragment_length = clib_net_to_host_u16 (fip->payload_length);
consumed = 1;
+ reass->fragments_n = 1;
goto check_if_done_maybe;
}
reass->min_fragment_length =
@@ -797,6 +805,7 @@
}
break;
}
+ ++reass->fragments_n;
check_if_done_maybe:
if (consumed)
{
@@ -816,6 +825,10 @@
if (consumed)
{
*bi0 = ~0;
+ if (reass->fragments_n > rm->max_reass_len)
+ {
+ return IP6_REASS_RC_TOO_MANY_FRAGMENTS;
+ }
}
else
{
@@ -989,10 +1002,25 @@
case IP6_REASS_RC_OK:
/* nothing to do here */
break;
+ case IP6_REASS_RC_TOO_MANY_FRAGMENTS:
+ vlib_node_increment_counter (vm, node->node_index,
+ IP6_ERROR_REASS_FRAGMENT_CHAIN_TOO_LONG,
+ 1);
+ ip6_reass_drop_all (vm, rm, reass);
+ ip6_reass_free (rm, rt, reass);
+ goto next_packet;
+ break;
case IP6_REASS_RC_NO_BUF:
- /* fallthrough */
+ vlib_node_increment_counter (vm, node->node_index,
+ IP6_ERROR_REASS_NO_BUF, 1);
+ ip6_reass_drop_all (vm, rm, reass);
+ ip6_reass_free (rm, rt, reass);
+ goto next_packet;
+ break;
case IP6_REASS_RC_INTERNAL_ERROR:
- /* drop everything and start with a clean slate */
+ vlib_node_increment_counter (vm, node->node_index,
+ IP6_ERROR_REASS_INTERNAL_ERROR,
+ 1);
ip6_reass_drop_all (vm, rm, reass);
ip6_reass_free (rm, rt, reass);
goto next_packet;
@@ -1151,20 +1179,21 @@
static void
ip6_reass_set_params (u32 timeout_ms, u32 max_reassemblies,
- u32 expire_walk_interval_ms)
+ u32 max_reassembly_length, u32 expire_walk_interval_ms)
{
ip6_reass_main.timeout_ms = timeout_ms;
ip6_reass_main.timeout = (f64) timeout_ms / (f64) MSEC_PER_SEC;
ip6_reass_main.max_reass_n = max_reassemblies;
+ ip6_reass_main.max_reass_len = max_reassembly_length;
ip6_reass_main.expire_walk_interval_ms = expire_walk_interval_ms;
}
vnet_api_error_t
ip6_reass_set (u32 timeout_ms, u32 max_reassemblies,
- u32 expire_walk_interval_ms)
+ u32 max_reassembly_length, u32 expire_walk_interval_ms)
{
u32 old_nbuckets = ip6_reass_get_nbuckets ();
- ip6_reass_set_params (timeout_ms, max_reassemblies,
+ ip6_reass_set_params (timeout_ms, max_reassemblies, max_reassembly_length,
expire_walk_interval_ms);
vlib_process_signal_event (ip6_reass_main.vlib_main,
ip6_reass_main.ip6_reass_expire_node_idx,
@@ -1231,6 +1260,7 @@
ip6_reass_set_params (IP6_REASS_TIMEOUT_DEFAULT_MS,
IP6_REASS_MAX_REASSEMBLIES_DEFAULT,
+ IP6_REASS_MAX_REASSEMBLY_LENGTH_DEFAULT,
IP6_REASS_EXPIRE_WALK_INTERVAL_DEFAULT_MS);
nbuckets = ip6_reass_get_nbuckets ();