On Wed, 31 Jul 2019 11:57:10 -0400, Willem de Bruijn wrote: > On Tue, Jul 30, 2019 at 5:13 PM Jakub Kicinski wrote: > > 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). > > > > Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.com>
> > diff --git a/net/core/sock.c b/net/core/sock.c > > index d57b0cc995a0..b0c10b518e65 100644 > > --- a/net/core/sock.c > > +++ b/net/core/sock.c > > @@ -1992,6 +1992,22 @@ 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 > > +#ifdef CONFIG_INET > > + if (skb->destructor == tcp_wfree) > > + return true; > > +#endif > > + return skb->destructor == sock_wfree; > > +} > > + > > Just insert the skb->decrypted check into skb_orphan_partial for less > code churn? Okie.. skb_orphan_partial() is a little ugly but will do. > I also think that this is an independent concern from leaking plain > text, so perhaps could be a separate patch. Do you mean the out-of-order stuff is a separate concern? It is, I had them separate at the first try, but GSO code looks at the destructor and IIRC only copies the socket if its still tcp_wfree. If we let partial orphan be we have to do temporary hairy stuff in tcp_gso_segment(). It's easier to just deal with partial orphan here.