Bluetooth: SMP: Fix not generating mackey and ltk when repairing

[ Upstream commit 545d7827b2cd5de5eb85580cebeda6b35b3ff443 ]

The change eed467b517e8 ("Bluetooth: fix passkey uninitialized when used")
introduced a goto that bypasses the creation of temporary mackey and ltk
which are later used by the likes of DHKey Check step.

Later ffee202a78c2 ("Bluetooth: Always request for user confirmation for
Just Works (LE SC)") which means confirm_hint is always set in case
JUST_WORKS so the branch checking for an existing LTK becomes pointless
as confirm_hint will always be set, so this just merge both cases of
malicious or legitimate devices to be confirmed before continuing with the
pairing procedure.

Link: https://github.com/bluez/bluez/issues/1622
Fixes: eed467b517e8 ("Bluetooth: fix passkey uninitialized when used")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

1 files changed, 7 insertions, 24 deletions

diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index 697ec98b0798..d1ba41153b66 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -2130,7 +2130,7 @@ static u8 smp_cmd_pairing_random(struct l2cap_conn *conn, struct sk_buff *skb)
 	struct smp_chan *smp = chan->data;
 	struct hci_conn *hcon = conn->hcon;
 	u8 *pkax, *pkbx, *na, *nb, confirm_hint;
-	u32 passkey;
+	u32 passkey = 0;
 	int err;
 
 	bt_dev_dbg(hcon->hdev, "conn %p", conn);
@@ -2182,24 +2182,6 @@ static u8 smp_cmd_pairing_random(struct l2cap_conn *conn, struct sk_buff *skb)
 		smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM, sizeof(smp->prnd),
 			     smp->prnd);
 		SMP_ALLOW_CMD(smp, SMP_CMD_DHKEY_CHECK);
-
-		/* Only Just-Works pairing requires extra checks */
-		if (smp->method != JUST_WORKS)
-			goto mackey_and_ltk;
-
-		/* If there already exists long term key in local host, leave
-		 * the decision to user space since the remote device could
-		 * be legitimate or malicious.
-		 */
-		if (hci_find_ltk(hcon->hdev, &hcon->dst, hcon->dst_type,
-				 hcon->role)) {
-			/* Set passkey to 0. The value can be any number since
-			 * it'll be ignored anyway.
-			 */
-			passkey = 0;
-			confirm_hint = 1;
-			goto confirm;
-		}
 	}
 
 mackey_and_ltk:
@@ -2220,11 +2202,12 @@ mackey_and_ltk:
 	if (err)
 		return SMP_UNSPECIFIED;
 
-	confirm_hint = 0;
-
-confirm:
-	if (smp->method == JUST_WORKS)
-		confirm_hint = 1;
+	/* Always require user confirmation for Just-Works pairing to prevent
+	 * impersonation attacks, or in case of a legitimate device that is
+	 * repairing use the confirmation as acknowledgment to proceed with the
+	 * creation of new keys.
+	 */
+	confirm_hint = smp->method == JUST_WORKS ? 1 : 0;
 
 	err = mgmt_user_confirm_request(hcon->hdev, &hcon->dst, hcon->type,
 					hcon->dst_type, passkey, confirm_hint);