Bluetooth: Make LTK and CSRK only persisent when bonding

In case the pairable option has been disabled, the pairing procedure
does not create keys for bonding. This means that these generated keys
should not be stored persistently.

For LTK and CSRK this is important to tell userspace to not store these
new keys. They will be available for the lifetime of the device, but
after the next power cycle they should not be used anymore.

Inform userspace to actually store the keys persistently only if both
sides request bonding.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>

include/net/bluetooth/hci_core.h

@@ -1270,9 +1270,10 @@ void mgmt_remote_name(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 link_type,
 void mgmt_discovering(struct hci_dev *hdev, u8 discovering);
 int mgmt_device_blocked(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 type);
 int mgmt_device_unblocked(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 type);
-void mgmt_new_ltk(struct hci_dev *hdev, struct smp_ltk *key);
+void mgmt_new_ltk(struct hci_dev *hdev, struct smp_ltk *key, bool persistent);
 void mgmt_new_irk(struct hci_dev *hdev, struct smp_irk *irk);
-void mgmt_new_csrk(struct hci_dev *hdev, struct smp_csrk *csrk);
+void mgmt_new_csrk(struct hci_dev *hdev, struct smp_csrk *csrk,
+		   bool persistent);
 void mgmt_reenable_advertising(struct hci_dev *hdev);
 void mgmt_smp_complete(struct hci_conn *conn, bool complete);
 

net/bluetooth/mgmt.c

@@ -5005,7 +5005,7 @@ void mgmt_new_link_key(struct hci_dev *hdev, struct link_key *key,
 	mgmt_event(MGMT_EV_NEW_LINK_KEY, hdev, &ev, sizeof(ev), NULL);
 }
 
-void mgmt_new_ltk(struct hci_dev *hdev, struct smp_ltk *key)
+void mgmt_new_ltk(struct hci_dev *hdev, struct smp_ltk *key, bool persistent)
 {
 	struct mgmt_ev_new_long_term_key ev;
 
@@ -5026,7 +5026,7 @@ void mgmt_new_ltk(struct hci_dev *hdev, struct smp_ltk *key)
 	    (key->bdaddr.b[5] & 0xc0) != 0xc0)
 		ev.store_hint = 0x00;
 	else
-		ev.store_hint = 0x01;
+		ev.store_hint = persistent;
 
 	bacpy(&ev.key.addr.bdaddr, &key->bdaddr);
 	ev.key.addr.type = link_to_bdaddr(LE_LINK, key->bdaddr_type);
@@ -5073,7 +5073,8 @@ void mgmt_new_irk(struct hci_dev *hdev, struct smp_irk *irk)
 	mgmt_event(MGMT_EV_NEW_IRK, hdev, &ev, sizeof(ev), NULL);
 }
 
-void mgmt_new_csrk(struct hci_dev *hdev, struct smp_csrk *csrk)
+void mgmt_new_csrk(struct hci_dev *hdev, struct smp_csrk *csrk,
+		   bool persistent)
 {
 	struct mgmt_ev_new_csrk ev;
 
@@ -5092,7 +5093,7 @@ void mgmt_new_csrk(struct hci_dev *hdev, struct smp_csrk *csrk)
 	    (csrk->bdaddr.b[5] & 0xc0) != 0xc0)
 		ev.store_hint = 0x00;
 	else
-		ev.store_hint = 0x01;
+		ev.store_hint = persistent;
 
 	bacpy(&ev.key.addr.bdaddr, &csrk->bdaddr);
 	ev.key.addr.type = link_to_bdaddr(LE_LINK, csrk->bdaddr_type);

net/bluetooth/smp.c

@@ -1209,32 +1209,40 @@ static void smp_notify_keys(struct l2cap_conn *conn)
 	struct smp_chan *smp = conn->smp_chan;
 	struct hci_conn *hcon = conn->hcon;
 	struct hci_dev *hdev = hcon->hdev;
+	struct smp_cmd_pairing *req = (void *) &smp->preq[1];
+	struct smp_cmd_pairing *rsp = (void *) &smp->prsp[1];
+	bool persistent;
 
 	if (smp->remote_irk)
 		mgmt_new_irk(hdev, smp->remote_irk);
 
+	/* The LTKs and CSRKs should be persistent only if both sides
+	 * had the bonding bit set in their authentication requests.
+	 */
+	persistent = !!((req->auth_req & rsp->auth_req) & SMP_AUTH_BONDING);
+
 	if (smp->csrk) {
 		smp->csrk->bdaddr_type = hcon->dst_type;
 		bacpy(&smp->csrk->bdaddr, &hcon->dst);
-		mgmt_new_csrk(hdev, smp->csrk);
+		mgmt_new_csrk(hdev, smp->csrk, persistent);
 	}
 
 	if (smp->slave_csrk) {
 		smp->slave_csrk->bdaddr_type = hcon->dst_type;
 		bacpy(&smp->slave_csrk->bdaddr, &hcon->dst);
-		mgmt_new_csrk(hdev, smp->slave_csrk);
+		mgmt_new_csrk(hdev, smp->slave_csrk, persistent);
 	}
 
 	if (smp->ltk) {
 		smp->ltk->bdaddr_type = hcon->dst_type;
 		bacpy(&smp->ltk->bdaddr, &hcon->dst);
-		mgmt_new_ltk(hdev, smp->ltk);
+		mgmt_new_ltk(hdev, smp->ltk, persistent);
 	}
 
 	if (smp->slave_ltk) {
 		smp->slave_ltk->bdaddr_type = hcon->dst_type;
 		bacpy(&smp->slave_ltk->bdaddr, &hcon->dst);
-		mgmt_new_ltk(hdev, smp->slave_ltk);
+		mgmt_new_ltk(hdev, smp->slave_ltk, persistent);
 	}
 }