ktls: Ensure FIFO encryption order for TLS 1.0.

TLS 1.0 records are encrypted as one continuous CBC chain where the
last block of the previous record is used as the IV for the next
record.  As a result, TLS 1.0 records cannot be encrypted out of order
but must be encrypted as a FIFO.

If the later pages of a sendfile(2) request complete before the first
pages, then TLS records can be encrypted out of order.  For TLS 1.1
and later this is fine, but this can break for TLS 1.0.

To cope, add a queue in each TLS session to hold TLS records that
contain valid unencrypted data but are waiting for an earlier TLS
record to be encrypted first.

- In ktls_enqueue(), check if a TLS record being queued is the next
  record expected for a TLS 1.0 session.  If not, it is placed in
  sorted order in the pending_records queue in the TLS session.

  If it is the next expected record, queue it for SW encryption like
  normal.  In addition, check if this new record (really a potential
  batch of records) was holding up any previously queued records in
  the pending_records queue.  Any of those records that are now in
  order are also placed on the queue for SW encryption.

- In ktls_destroy(), free any TLS records on the pending_records
  queue.  These mbufs are marked M_NOTREADY so were not freed when the
  socket buffer was purged in sbdestroy().  Instead, they must be
  freed explicitly.

Reviewed by:	gallatin, markj
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D32381

1 files changed, 110 insertions, 3 deletions

diff --git a/sys/kern/uipc_ktls.c b/sys/kern/uipc_ktls.c
index 12bb02876083..1e778dbf113a 100644
--- a/sys/kern/uipc_ktls.c
+++ b/sys/kern/uipc_ktls.c
@@ -162,6 +162,11 @@ static COUNTER_U64_DEFINE_EARLY(ktls_tasks_active);
 SYSCTL_COUNTER_U64(_kern_ipc_tls, OID_AUTO, tasks_active, CTLFLAG_RD,
     &ktls_tasks_active, "Number of active tasks");
 
+static COUNTER_U64_DEFINE_EARLY(ktls_cnt_tx_pending);
+SYSCTL_COUNTER_U64(_kern_ipc_tls_stats, OID_AUTO, sw_tx_pending, CTLFLAG_RD,
+    &ktls_cnt_tx_pending,
+    "Number of TLS 1.0 records waiting for earlier TLS records");
+
 static COUNTER_U64_DEFINE_EARLY(ktls_cnt_tx_queued);
 SYSCTL_COUNTER_U64(_kern_ipc_tls_stats, OID_AUTO, sw_tx_inqueue, CTLFLAG_RD,
     &ktls_cnt_tx_queued,
@@ -612,6 +617,9 @@ ktls_create_session(struct socket *so, struct tls_enable *en,
 		case CRYPTO_SHA1_HMAC:
 			if (en->tls_vminor == TLS_MINOR_VER_ZERO) {
 				/* Implicit IV, no nonce. */
+				tls->sequential_records = true;
+				tls->next_seqno = be64dec(en->rec_seq);
+				STAILQ_INIT(&tls->pending_records);
 			} else {
 				tls->params.tls_hlen += AES_BLOCK_LEN;
 			}
@@ -1490,6 +1498,20 @@ void
 ktls_destroy(struct ktls_session *tls)
 {
 
+	if (tls->sequential_records) {
+		struct mbuf *m, *n;
+		int page_count;
+
+		STAILQ_FOREACH_SAFE(m, &tls->pending_records, m_epg_stailq, n) {
+			page_count = m->m_epg_enc_cnt;
+			while (page_count > 0) {
+				KASSERT(page_count >= m->m_epg_nrdy,
+				    ("%s: too few pages", __func__));
+				page_count -= m->m_epg_nrdy;
+				m = m_free(m);
+			}
+		}
+	}
 	ktls_cleanup(tls);
 	uma_zfree(ktls_session_zone, tls);
 }
@@ -2092,10 +2114,29 @@ ktls_encrypt_record(struct ktls_wq *wq, struct mbuf *m,
 	return (error);
 }
 
+/* Number of TLS records in a batch passed to ktls_enqueue(). */
+static u_int
+ktls_batched_records(struct mbuf *m)
+{
+	int page_count, records;
+
+	records = 0;
+	page_count = m->m_epg_enc_cnt;
+	while (page_count > 0) {
+		records++;
+		page_count -= m->m_epg_nrdy;
+		m = m->m_next;
+	}
+	KASSERT(page_count == 0, ("%s: mismatched page count", __func__));
+	return (records);
+}
+
 void
 ktls_enqueue(struct mbuf *m, struct socket *so, int page_count)
 {
+	struct ktls_session *tls;
 	struct ktls_wq *wq;
+	int queued;
 	bool running;
 
 	KASSERT(((m->m_flags & (M_EXTPG | M_NOTREADY)) ==
@@ -2113,14 +2154,80 @@ ktls_enqueue(struct mbuf *m, struct socket *so, int page_count)
 	 */
 	m->m_epg_so = so;
 
-	wq = &ktls_wq[m->m_epg_tls->wq_index];
+	queued = 1;
+	tls = m->m_epg_tls;
+	wq = &ktls_wq[tls->wq_index];
 	mtx_lock(&wq->mtx);
-	STAILQ_INSERT_TAIL(&wq->m_head, m, m_epg_stailq);
+	if (__predict_false(tls->sequential_records)) {
+		/*
+		 * For TLS 1.0, records must be encrypted
+		 * sequentially.  For a given connection, all records
+		 * queued to the associated work queue are processed
+		 * sequentially.  However, sendfile(2) might complete
+		 * I/O requests spanning multiple TLS records out of
+		 * order.  Here we ensure TLS records are enqueued to
+		 * the work queue in FIFO order.
+		 *
+		 * tls->next_seqno holds the sequence number of the
+		 * next TLS record that should be enqueued to the work
+		 * queue.  If this next record is not tls->next_seqno,
+		 * it must be a future record, so insert it, sorted by
+		 * TLS sequence number, into tls->pending_records and
+		 * return.
+		 *
+		 * If this TLS record matches tls->next_seqno, place
+		 * it in the work queue and then check
+		 * tls->pending_records to see if any
+		 * previously-queued records are now ready for
+		 * encryption.
+		 */
+		if (m->m_epg_seqno != tls->next_seqno) {
+			struct mbuf *n, *p;
+
+			p = NULL;
+			STAILQ_FOREACH(n, &tls->pending_records, m_epg_stailq) {
+				if (n->m_epg_seqno > m->m_epg_seqno)
+					break;
+				p = n;
+			}
+			if (n == NULL)
+				STAILQ_INSERT_TAIL(&tls->pending_records, m,
+				    m_epg_stailq);
+			else if (p == NULL)
+				STAILQ_INSERT_HEAD(&tls->pending_records, m,
+				    m_epg_stailq);
+			else
+				STAILQ_INSERT_AFTER(&tls->pending_records, p, m,
+				    m_epg_stailq);
+			mtx_unlock(&wq->mtx);
+			counter_u64_add(ktls_cnt_tx_pending, 1);
+			return;
+		}
+
+		tls->next_seqno += ktls_batched_records(m);
+		STAILQ_INSERT_TAIL(&wq->m_head, m, m_epg_stailq);
+
+		while (!STAILQ_EMPTY(&tls->pending_records)) {
+			struct mbuf *n;
+
+			n = STAILQ_FIRST(&tls->pending_records);
+			if (n->m_epg_seqno != tls->next_seqno)
+				break;
+
+			queued++;
+			STAILQ_REMOVE_HEAD(&tls->pending_records, m_epg_stailq);
+			tls->next_seqno += ktls_batched_records(n);
+			STAILQ_INSERT_TAIL(&wq->m_head, n, m_epg_stailq);
+		}
+		counter_u64_add(ktls_cnt_tx_pending, -(queued - 1));
+	} else
+		STAILQ_INSERT_TAIL(&wq->m_head, m, m_epg_stailq);
+
 	running = wq->running;
 	mtx_unlock(&wq->mtx);
 	if (!running)
 		wakeup(wq);
-	counter_u64_add(ktls_cnt_tx_queued, 1);
+	counter_u64_add(ktls_cnt_tx_queued, queued);
 }
 
 /*