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authorJakub Kicinski <jakub.kicinski@netronome.com>2019-08-07 17:03:59 -0700
committerDavid S. Miller <davem@davemloft.net>2019-08-08 22:39:35 -0700
commit414776621d1006e57e80e6db7fdc3837897aaa64 (patch)
treed5b3ce46bcc809eb5ccdb2728df85192c1d6485d /net/core
parent0de94de18027540200f2f193be6a2fa749cb7ebe (diff)
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net/tls: prevent skb_orphan() from leaking TLS plain text with offload
sk_validate_xmit_skb() and drivers depend on the sk member of struct sk_buff to identify segments requiring encryption. Any operation which removes or does not preserve the original TLS socket such as skb_orphan() or skb_clone() will cause clear text leaks. Make the TCP socket underlying an offloaded TLS connection mark all skbs as decrypted, if TLS TX is in offload mode. Then in sk_validate_xmit_skb() catch skbs which have no socket (or a socket with no validation) and decrypted flag set. Note that CONFIG_SOCK_VALIDATE_XMIT, CONFIG_TLS_DEVICE and sk->sk_validate_xmit_skb are slightly interchangeable right now, they all imply TLS offload. The new checks are guarded by CONFIG_TLS_DEVICE because that's the option guarding the sk_buff->decrypted member. Second, smaller issue with orphaning is that it breaks the guarantee that packets will be delivered to device queues in-order. All TLS offload drivers depend on that scheduling property. This means skb_orphan_partial()'s trick of preserving partial socket references will cause issues in the drivers. We need a full orphan, and as a result netem delay/throttling will cause all TLS offload skbs to be dropped. Reusing the sk_buff->decrypted flag also protects from leaking clear text when incoming, decrypted skb is redirected (e.g. by TC). See commit 0608c69c9a80 ("bpf: sk_msg, sock{map|hash} redirect through ULP") for justification why the internal flag is safe. The only location which could leak the flag in is tcp_bpf_sendmsg(), which is taken care of by clearing the previously unused bit. v2: - remove superfluous decrypted mark copy (Willem); - remove the stale doc entry (Boris); - rely entirely on EOR marking to prevent coalescing (Boris); - use an internal sendpages flag instead of marking the socket (Boris). v3 (Willem): - reorganize the can_skb_orphan_partial() condition; - fix the flag leak-in through tcp_bpf_sendmsg. Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> Acked-by: Willem de Bruijn <willemb@google.com> Reviewed-by: Boris Pismenny <borisp@mellanox.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/sock.c19
1 files changed, 14 insertions, 5 deletions
diff --git a/net/core/sock.c b/net/core/sock.c
index d57b0cc995a0..6d08553f885c 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1992,6 +1992,19 @@ void skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
}
EXPORT_SYMBOL(skb_set_owner_w);
+static bool can_skb_orphan_partial(const struct sk_buff *skb)
+{
+#ifdef CONFIG_TLS_DEVICE
+ /* Drivers depend on in-order delivery for crypto offload,
+ * partial orphan breaks out-of-order-OK logic.
+ */
+ if (skb->decrypted)
+ return false;
+#endif
+ return (skb->destructor == sock_wfree ||
+ (IS_ENABLED(CONFIG_INET) && skb->destructor == tcp_wfree));
+}
+
/* This helper is used by netem, as it can hold packets in its
* delay queue. We want to allow the owner socket to send more
* packets, as if they were already TX completed by a typical driver.
@@ -2003,11 +2016,7 @@ void skb_orphan_partial(struct sk_buff *skb)
if (skb_is_tcp_pure_ack(skb))
return;
- if (skb->destructor == sock_wfree
-#ifdef CONFIG_INET
- || skb->destructor == tcp_wfree
-#endif
- ) {
+ if (can_skb_orphan_partial(skb)) {
struct sock *sk = skb->sk;
if (refcount_inc_not_zero(&sk->sk_refcnt)) {