From: "Jason A. Donenfeld" Jason@zx2c4.com
[ Upstream commit c78a0b4a78839d572d8a80f6a62221c0d7843135 ]
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/wireguard/messages.h | 2 +- drivers/net/wireguard/queueing.h | 10 +++++++++- drivers/net/wireguard/receive.c | 2 +- drivers/net/wireguard/send.c | 7 ++++++- 4 files changed, 17 insertions(+), 4 deletions(-)
--- 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 }; --- a/drivers/net/wireguard/queueing.h +++ b/drivers/net/wireguard/queueing.h @@ -87,12 +87,20 @@ static inline bool wg_check_packet_proto 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; --- a/drivers/net/wireguard/receive.c +++ b/drivers/net/wireguard/receive.c @@ -485,7 +485,7 @@ int wg_packet_rx_poll(struct napi_struct 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;
--- a/drivers/net/wireguard/send.c +++ b/drivers/net/wireguard/send.c @@ -170,6 +170,11 @@ static bool encrypt_packet(struct sk_buf 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); @@ -298,7 +303,7 @@ void wg_packet_encrypt_worker(struct wor 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;