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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
parentMerge branch 'skbedit-batch-fixes' (diff)
downloadlinux-dev-414776621d1006e57e80e6db7fdc3837897aaa64.tar.xz
linux-dev-414776621d1006e57e80e6db7fdc3837897aaa64.zip
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')
-rw-r--r--net/core/sock.c19
-rw-r--r--net/ipv4/tcp.c3
-rw-r--r--net/ipv4/tcp_bpf.c6
-rw-r--r--net/ipv4/tcp_output.c3
-rw-r--r--net/tls/tls_device.c9
5 files changed, 32 insertions, 8 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)) {
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 776905899ac0..77b485d60b9d 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -984,6 +984,9 @@ new_segment:
if (!skb)
goto wait_for_memory;
+#ifdef CONFIG_TLS_DEVICE
+ skb->decrypted = !!(flags & MSG_SENDPAGE_DECRYPTED);
+#endif
skb_entail(sk, skb);
copy = size_goal;
}
diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index 3d1e15401384..8a56e09cfb0e 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -398,10 +398,14 @@ more_data:
static int tcp_bpf_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
{
struct sk_msg tmp, *msg_tx = NULL;
- int flags = msg->msg_flags | MSG_NO_SHARED_FRAGS;
int copied = 0, err = 0;
struct sk_psock *psock;
long timeo;
+ int flags;
+
+ /* Don't let internal do_tcp_sendpages() flags through */
+ flags = (msg->msg_flags & ~MSG_SENDPAGE_DECRYPTED);
+ flags |= MSG_NO_SHARED_FRAGS;
psock = sk_psock_get(sk);
if (unlikely(!psock))
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 6e4afc48d7bb..979520e46e33 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1320,6 +1320,7 @@ int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
if (!buff)
return -ENOMEM; /* We'll just try again later. */
+ skb_copy_decrypted(buff, skb);
sk->sk_wmem_queued += buff->truesize;
sk_mem_charge(sk, buff->truesize);
@@ -1874,6 +1875,7 @@ static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
buff = sk_stream_alloc_skb(sk, 0, gfp, true);
if (unlikely(!buff))
return -ENOMEM;
+ skb_copy_decrypted(buff, skb);
sk->sk_wmem_queued += buff->truesize;
sk_mem_charge(sk, buff->truesize);
@@ -2143,6 +2145,7 @@ static int tcp_mtu_probe(struct sock *sk)
sk_mem_charge(sk, nskb->truesize);
skb = tcp_send_head(sk);
+ skb_copy_decrypted(nskb, skb);
TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
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;
}
}