linux-kernel - [PATCH 3.16 054/132] Bluetooth: Align minimum encryption key size for LE and BR/EDR connections

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Message-ID: <lsq.1568989415.203002686@decadent.org.uk>
Date:   Fri, 20 Sep 2019 15:23:35 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Johan Hedberg" <johan.hedberg@...el.com>,
        "Marcel Holtmann" <marcel@...tmann.org>
Subject: [PATCH 3.16 054/132] Bluetooth: Align minimum encryption key size
 for LE and BR/EDR connections

3.16.74-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Marcel Holtmann <marcel@...tmann.org>

commit d5bb334a8e171b262e48f378bd2096c0ea458265 upstream.

The minimum encryption key size for LE connections is 56 bits and to
align LE with BR/EDR, enforce 56 bits of minimum encryption key size for
BR/EDR connections as well.

Signed-off-by: Marcel Holtmann <marcel@...tmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@...el.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 include/net/bluetooth/hci_core.h | 3 +++
 net/bluetooth/hci_conn.c         | 8 ++++++++
 2 files changed, 11 insertions(+)

--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -142,6 +142,9 @@ struct oob_data {
 
 #define HCI_MAX_SHORT_NAME_LENGTH	10
 
+/* Min encryption key size to match with SMP */
+#define HCI_MIN_ENC_KEY_SIZE		7
+
 /* Default LE RPA expiry time, 15 minutes */
 #define HCI_DEFAULT_RPA_TIMEOUT		(15 * 60)
 
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -868,6 +868,14 @@ int hci_conn_check_link_mode(struct hci_
 	if (hci_conn_ssp_enabled(conn) && !(conn->link_mode & HCI_LM_ENCRYPT))
 		return 0;
 
+	/* The minimum encryption key size needs to be enforced by the
+	 * host stack before establishing any L2CAP connections. The
+	 * specification in theory allows a minimum of 1, but to align
+	 * BR/EDR and LE transports, a minimum of 7 is chosen.
+	 */
+	if (conn->enc_key_size < HCI_MIN_ENC_KEY_SIZE)
+		return 0;
+
 	return 1;
 }