summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorJason A. Donenfeld <Jason@zx2c4.com>2020-05-20 07:49:29 +0300
committerDavid S. Miller <davem@davemloft.net>2020-05-21 06:55:09 +0300
commitc78a0b4a78839d572d8a80f6a62221c0d7843135 (patch)
tree672c5f0eeb8812ba47c3fdcd2672d56b415a6528
parentbc67d371256f5c47d824e2eec51e46c8d62d022e (diff)
downloadlinux-c78a0b4a78839d572d8a80f6a62221c0d7843135.tar.xz
wireguard: queueing: preserve flow hash across packet scrubbing
It's important that we clear most header fields during encapsulation and decapsulation, because the packet is substantially changed, and we don't want any info leak or logic bug due to an accidental correlation. But, for encapsulation, it's wrong to clear skb->hash, since it's used by fq_codel and flow dissection in general. Without it, classification does not proceed as usual. This change might make it easier to estimate the number of innerflows by examining clustering of out of order packets, but this shouldn't open up anything that can't already be inferred otherwise (e.g. syn packet size inference), and fq_codel can be disabled anyway. Furthermore, it might be the case that the hash isn't used or queried at all until after wireguard transmits the encrypted UDP packet, which means skb->hash might still be zero at this point, and thus no hash taken over the inner packet data. In order to address this situation, we force a calculation of skb->hash before encrypting packet data. Of course this means that fq_codel might transmit packets slightly more out of order than usual. Toke did some testing on beefy machines with high quantities of parallel flows and found that increasing the reply-attack counter to 8192 takes care of the most pathological cases pretty well. Reported-by: Dave Taht <dave.taht@gmail.com> Reviewed-and-tested-by: Toke Høiland-Jørgensen <toke@toke.dk> Fixes: e7096c131e51 ("net: WireGuard secure network tunnel") Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/wireguard/messages.h2
-rw-r--r--drivers/net/wireguard/queueing.h10
-rw-r--r--drivers/net/wireguard/receive.c2
-rw-r--r--drivers/net/wireguard/send.c7
4 files changed, 17 insertions, 4 deletions
diff --git a/drivers/net/wireguard/messages.h b/drivers/net/wireguard/messages.h
index b8a7b9ce32ba..208da72673fc 100644
--- a/drivers/net/wireguard/messages.h
+++ b/drivers/net/wireguard/messages.h
@@ -32,7 +32,7 @@ enum cookie_values {
};
enum counter_values {
- COUNTER_BITS_TOTAL = 2048,
+ COUNTER_BITS_TOTAL = 8192,
COUNTER_REDUNDANT_BITS = BITS_PER_LONG,
COUNTER_WINDOW_SIZE = COUNTER_BITS_TOTAL - COUNTER_REDUNDANT_BITS
};
diff --git a/drivers/net/wireguard/queueing.h b/drivers/net/wireguard/queueing.h
index 3432232afe06..c58df439dbbe 100644
--- a/drivers/net/wireguard/queueing.h
+++ b/drivers/net/wireguard/queueing.h
@@ -87,12 +87,20 @@ static inline bool wg_check_packet_protocol(struct sk_buff *skb)
return real_protocol && skb->protocol == real_protocol;
}
-static inline void wg_reset_packet(struct sk_buff *skb)
+static inline void wg_reset_packet(struct sk_buff *skb, bool encapsulating)
{
+ u8 l4_hash = skb->l4_hash;
+ u8 sw_hash = skb->sw_hash;
+ u32 hash = skb->hash;
skb_scrub_packet(skb, true);
memset(&skb->headers_start, 0,
offsetof(struct sk_buff, headers_end) -
offsetof(struct sk_buff, headers_start));
+ if (encapsulating) {
+ skb->l4_hash = l4_hash;
+ skb->sw_hash = sw_hash;
+ skb->hash = hash;
+ }
skb->queue_mapping = 0;
skb->nohdr = 0;
skb->peeked = 0;
diff --git a/drivers/net/wireguard/receive.c b/drivers/net/wireguard/receive.c
index 3bb5b9ae7cd1..d0eebd90c9d5 100644
--- a/drivers/net/wireguard/receive.c
+++ b/drivers/net/wireguard/receive.c
@@ -484,7 +484,7 @@ int wg_packet_rx_poll(struct napi_struct *napi, int budget)
if (unlikely(wg_socket_endpoint_from_skb(&endpoint, skb)))
goto next;
- wg_reset_packet(skb);
+ wg_reset_packet(skb, false);
wg_packet_consume_data_done(peer, skb, &endpoint);
free = false;
diff --git a/drivers/net/wireguard/send.c b/drivers/net/wireguard/send.c
index 6687db699803..2f5119ff93d8 100644
--- a/drivers/net/wireguard/send.c
+++ b/drivers/net/wireguard/send.c
@@ -167,6 +167,11 @@ static bool encrypt_packet(struct sk_buff *skb, struct noise_keypair *keypair)
struct sk_buff *trailer;
int num_frags;
+ /* Force hash calculation before encryption so that flow analysis is
+ * consistent over the inner packet.
+ */
+ skb_get_hash(skb);
+
/* Calculate lengths. */
padding_len = calculate_skb_padding(skb);
trailer_len = padding_len + noise_encrypted_len(0);
@@ -295,7 +300,7 @@ void wg_packet_encrypt_worker(struct work_struct *work)
skb_list_walk_safe(first, skb, next) {
if (likely(encrypt_packet(skb,
PACKET_CB(first)->keypair))) {
- wg_reset_packet(skb);
+ wg_reset_packet(skb, true);
} else {
state = PACKET_STATE_DEAD;
break;