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authorJakub Kicinski <jakub.kicinski@netronome.com>2019-08-08 03:03:59 +0300
committerDavid S. Miller <davem@davemloft.net>2019-08-09 08:39:35 +0300
commit414776621d1006e57e80e6db7fdc3837897aaa64 (patch)
treed5b3ce46bcc809eb5ccdb2728df85192c1d6485d /net/tls
parent0de94de18027540200f2f193be6a2fa749cb7ebe (diff)
downloadlinux-414776621d1006e57e80e6db7fdc3837897aaa64.tar.xz
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/tls')
-rw-r--r--net/tls/tls_device.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index 7c0b2b778703..43922d86e510 100644
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c
@@ -373,9 +373,9 @@ static int tls_push_data(struct sock *sk,
struct tls_context *tls_ctx = tls_get_ctx(sk);
struct tls_prot_info *prot = &tls_ctx->prot_info;
struct tls_offload_context_tx *ctx = tls_offload_ctx_tx(tls_ctx);
- int tls_push_record_flags = flags | MSG_SENDPAGE_NOTLAST;
int more = flags & (MSG_SENDPAGE_NOTLAST | MSG_MORE);
struct tls_record_info *record = ctx->open_record;
+ int tls_push_record_flags;
struct page_frag *pfrag;
size_t orig_size = size;
u32 max_open_record_len;
@@ -390,6 +390,9 @@ static int tls_push_data(struct sock *sk,
if (sk->sk_err)
return -sk->sk_err;
+ flags |= MSG_SENDPAGE_DECRYPTED;
+ tls_push_record_flags = flags | MSG_SENDPAGE_NOTLAST;
+
timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
if (tls_is_partially_sent_record(tls_ctx)) {
rc = tls_push_partial_record(sk, tls_ctx, flags);
@@ -576,7 +579,9 @@ void tls_device_write_space(struct sock *sk, struct tls_context *ctx)
gfp_t sk_allocation = sk->sk_allocation;
sk->sk_allocation = GFP_ATOMIC;
- tls_push_partial_record(sk, ctx, MSG_DONTWAIT | MSG_NOSIGNAL);
+ tls_push_partial_record(sk, ctx,
+ MSG_DONTWAIT | MSG_NOSIGNAL |
+ MSG_SENDPAGE_DECRYPTED);
sk->sk_allocation = sk_allocation;
}
}