linux-kernel - [PATCH 4.4 154/266] Bluetooth: Align minimum encryption key size for LE and BR/EDR connections

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Message-Id: <20190515090728.123038312@linuxfoundation.org>
Date:   Wed, 15 May 2019 12:54:21 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...el.com>
Subject: [PATCH 4.4 154/266] Bluetooth: Align minimum encryption key size for LE and BR/EDR connections

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>
Cc: stable@...r.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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
@@ -174,6 +174,9 @@ struct adv_info {
 
 #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
@@ -1177,6 +1177,14 @@ int hci_conn_check_link_mode(struct hci_
 	    !test_bit(HCI_CONN_ENCRYPT, &conn->flags))
 		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;
 }