[PATCH] Bluetooth: Limit OOB to P-256 values for Secure Connection Only mode

[Marcel Holtmann <marcel@holtmann.org>]

When using Secure Connection Only mode, the P-192 hash and rand values
for BR/EDR and the TK value for LE are not valid. The Secure Connections
Only mode limits the encryption keys to P-256 derived values for both
transports. To avoid accidentally loading weak values for pairing just
restrict it to P-256 values.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
---
 net/bluetooth/mgmt.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
index 8417ab387d1a..5c7340b1cd66 100644
--- a/net/bluetooth/mgmt.c
+++ b/net/bluetooth/mgmt.c
@@ -3660,6 +3660,21 @@ static int add_remote_oob_data(struct sock *sk, struct hci_dev *hdev,
 			goto unlock;
 		}
 
+		/* In case Secure Connections Only made has been enabled,
+		 * do not allow providing P-192 hash and rand values.
+		 *
+		 * This actually means that in Secure Connections Only
+		 * mode this command with the legacy parameter list
+		 * is not supported at all.
+		 */
+		if (test_bit(HCI_SC_ONLY, &hdev->dev_flags)) {
+			err = cmd_complete(sk, hdev->id,
+					   MGMT_OP_ADD_REMOTE_OOB_DATA,
+					   MGMT_STATUS_INVALID_PARAMS,
+					   addr, sizeof(*addr));
+			goto unlock;
+		}
+
 		err = hci_add_remote_oob_data(hdev, &cp->addr.bdaddr,
 					      cp->addr.type, cp->hash,
 					      cp->rand, NULL, NULL);
@@ -3675,10 +3690,17 @@ static int add_remote_oob_data(struct sock *sk, struct hci_dev *hdev,
 		u8 *rand192, *hash192;
 		u8 status;
 
-		if (bdaddr_type_is_le(cp->addr.type)) {
-			/* Enforce zero-valued 192-bit parameters as
-			 * long as legacy SMP OOB isn't implemented.
-			 */
+		/* For Bluetooth LE, currently only P-256 hash and rand
+		 * values are allowed. The P-192 hash and rand values
+		 * are required to be zero. This is required since Legacy
+		 * Pairing for LE with OOB is not implemented yet.
+		 *
+		 * In case Secure Connections Only made has been enabled,
+		 * do not allow providing P-192 hash and rand values. It
+		 * is required that the values are zero here as well.
+		 */
+		if (bdaddr_type_is_le(cp->addr.type) ||
+		    test_bit(HCI_SC_ONLY, &hdev->dev_flags)) {
 			if (memcmp(cp->rand192, ZERO_KEY, 16) ||
 			    memcmp(cp->hash192, ZERO_KEY, 16)) {
 				err = cmd_complete(sk, hdev->id,
-- 
2.1.0