Bluetooth: MGMT: Add management security level changed event

Add an event on device security level or encryption type change to let user space know which level is currently in use. Reset security level to 0 on disconnection so further connections will correctly report security level changes.

This will be used for BlueZ qualification automation.

Assisted-by GPT:GPT-5.3-Codex

Signed-off-by Frédéric Danis <[email protected]>

---
v1->v2:
- Add encryption type to the mgmt event
- Send event on security level or encryption type change
v2->v3:
- Replace fixed security level and ancryption type parameters by TLV array to allow later enhancement.
v3->v4:
- Change MGMT_EV_SECURITY_LEVEL_CHANGED to 0x0034
- Add __counted_by for the tlv_data
- dynamically allow the mgmt_ev_security_level_changed structure
v4->v5: Address Sashiko comments:
- stop overwriting tlv_count and replace it by tlv_length as kzalloc_flex() should already set it to the byte length. This depends on compiler supporting __builtin_counted_by_ref(), so explicitly set it too.
- filter on link type to prevent to send event for child connection
- remove premature calls to mgmt_security_level_changed()
- send events only on security level changes

 include/net/bluetooth/hci_core.h | 15 ++++++++--
 include/net/bluetooth/mgmt.h     | 14 +++++++++
 net/bluetooth/hci_conn.c         | 10 +++++++
 net/bluetooth/hci_event.c        | 28 ++++++++++++++++--
 net/bluetooth/mgmt.c             | 49 ++++++++++++++++++++++++++++++++
 5 files changed, 112 insertions(+), 4 deletions(-)

include/net/bluetooth/hci_core.h +13 -2

index fb85a0ccb250..0f4a345f492c 100644
@@ -2255,6 +2255,8 @@ static inline void hci_auth_cfm(struct hci_conn *conn, __u8 status)
                conn->security_cfm_cb(conn, status);
 }
 
+void mgmt_security_level_changed(struct hci_conn *conn);
+
 static inline void hci_encrypt_cfm(struct hci_conn *conn, __u8 status)
 {
        struct hci_cb *cb;

@@ -2277,11 +2279,20 @@ static inline void hci_encrypt_cfm(struct hci_conn *conn, __u8 status)
                encrypt = 0x01;
 
        if (!status) {
-               if (conn->sec_level == BT_SECURITY_SDP)
+               bool sec_level_changed  = false;
+
+               if (conn->sec_level == BT_SECURITY_SDP) {
                        conn->sec_level = BT_SECURITY_LOW;
+                       sec_level_changed = true;
+               }
 
-               if (conn->pending_sec_level > conn->sec_level)
+               if (conn->pending_sec_level > conn->sec_level) {
                        conn->sec_level = conn->pending_sec_level;
+                       sec_level_changed = true;
+               }
+
+               if (sec_level_changed)
+                       mgmt_security_level_changed(conn);
        }
 
        mutex_lock(&hci_cb_list_lock);

include/net/bluetooth/mgmt.h +14 -0

index 1e22eab1081c..b02e915bb44c 100644
@@ -1221,3 +1221,17 @@ struct mgmt_ev_conn_subrate {
        __le16  cont_num;
        __le16  supv_timeout;
 } __packed;
+
+#define MGMT_CONN_SEC_ENCRYPT_NONE             0x00
+#define MGMT_CONN_SEC_ENCRYPT_E0               0x01
+#define MGMT_CONN_SEC_ENCRYPT_AES_CCM          0x02
+
+#define MGMT_SEC_LEVEL_CHANGED_PARAM_LEVEL     0x0000
+#define MGMT_SEC_LEVEL_CHANGED_PARAM_ENC_TYPE  0x0001
+
+#define MGMT_EV_SECURITY_LEVEL_CHANGED         0x0034
+struct mgmt_ev_security_level_changed {
+       struct mgmt_addr_info addr;
+       __u8    tlv_length;
+       __u8    tlv_data[] __counted_by(tlv_length);
+} __packed;

net/bluetooth/hci_conn.c +10 -0

index cf44452e0766..5191fd72ac9e 100644
@@ -1233,6 +1233,11 @@ static void hci_conn_unlink(struct hci_conn *conn)
        if (!conn->parent) {
                struct hci_link *link, *t;
 
+               conn->sec_level = BT_SECURITY_SDP;
+               clear_bit(HCI_CONN_ENCRYPT, &conn->flags);
+               clear_bit(HCI_CONN_AES_CCM, &conn->flags);
+               mgmt_security_level_changed(conn);
+
                list_for_each_entry_safe(link, t, &conn->link_list, list) {
                        struct hci_conn *child = link->conn;
 

@@ -1543,6 +1548,11 @@ struct hci_conn *hci_connect_le(struct hci_dev *hdev, bdaddr_t *dst,
                conn->pending_sec_level = sec_level;
        }
 
+       /* Do not report the security level here: conn->dst may still hold
+        * the peer's RPA instead of its identity address, and the connection
+        * is not established yet. le_conn_complete_evt() reports it once the
+        * connection completes and the identity address has been resolved.
+        */
        conn->sec_level = BT_SECURITY_LOW;
        conn->conn_timeout = conn_timeout;
        conn->le_adv_phy = phy;

net/bluetooth/hci_event.c +26 -2

index 5ac2357e92c9..e2961e1837aa 100644
@@ -755,6 +755,7 @@ static u8 hci_cc_read_enc_key_size(struct hci_dev *hdev, void *data,
                        status = HCI_ERROR_AUTH_FAILURE;
                        clear_bit(HCI_CONN_ENCRYPT, &conn->flags);
                        clear_bit(HCI_CONN_AES_CCM, &conn->flags);
+                       mgmt_security_level_changed(conn);
                }
 
                /* Update the key encryption size with the connection one */

@@ -3210,6 +3211,8 @@ static void hci_conn_complete_evt(struct hci_dev *hdev, void *data,
        }
 
        if (!status) {
+               bool encrypt_change = false;
+
                status = hci_conn_set_handle(conn, __le16_to_cpu(ev->handle));
                if (status)
                        goto done;

@@ -3232,8 +3235,10 @@ static void hci_conn_complete_evt(struct hci_dev *hdev, void *data,
                if (test_bit(HCI_AUTH, &hdev->flags))
                        set_bit(HCI_CONN_AUTH, &conn->flags);
 
-               if (test_bit(HCI_ENCRYPT, &hdev->flags))
+               if (test_bit(HCI_ENCRYPT, &hdev->flags)) {
                        set_bit(HCI_CONN_ENCRYPT, &conn->flags);
+                       encrypt_change = true;
+               }
 
                /* "Link key request" completed ahead of "connect request" completes */
                if (ev->encr_mode == 1 && !test_bit(HCI_CONN_ENCRYPT, &conn->flags) &&

@@ -3243,11 +3248,15 @@ static void hci_conn_complete_evt(struct hci_dev *hdev, void *data,
                        key = hci_find_link_key(hdev, &ev->bdaddr);
                        if (key) {
                                set_bit(HCI_CONN_ENCRYPT, &conn->flags);
+                               encrypt_change = true;
                                hci_read_enc_key_size(hdev, conn);
                                hci_encrypt_cfm(conn, ev->status);
                        }
                }
 
+               if (encrypt_change)
+                       mgmt_security_level_changed(conn);
+
                /* Get remote features */
                if (conn->type == ACL_LINK) {
                        struct hci_cp_read_remote_features cp;

@@ -3514,9 +3523,14 @@ static void hci_auth_complete_evt(struct hci_dev *hdev, void *data,
                goto unlock;
 
        if (!ev->status) {
+               bool sec_level_changed =
+                               conn->sec_level != conn->pending_sec_level;
+
                clear_bit(HCI_CONN_AUTH_FAILURE, &conn->flags);
                set_bit(HCI_CONN_AUTH, &conn->flags);
                conn->sec_level = conn->pending_sec_level;
+               if (sec_level_changed)
+                       mgmt_security_level_changed(conn);
        } else {
                if (ev->status == HCI_ERROR_PIN_OR_KEY_MISSING)
                        set_bit(HCI_CONN_AUTH_FAILURE, &conn->flags);

@@ -3632,9 +3646,12 @@ static void hci_encrypt_change_evt(struct hci_dev *hdev, void *data,
                        if ((conn->type == ACL_LINK && ev->encrypt == 0x02) ||
                            conn->type == LE_LINK)
                                set_bit(HCI_CONN_AES_CCM, &conn->flags);
+
+                       mgmt_security_level_changed(conn);
                } else {
                        clear_bit(HCI_CONN_ENCRYPT, &conn->flags);
                        clear_bit(HCI_CONN_AES_CCM, &conn->flags);
+                       mgmt_security_level_changed(conn);
                }
        }
 

@@ -5228,8 +5245,14 @@ static void hci_key_refresh_complete_evt(struct hci_dev *hdev, void *data,
        if (conn->type != LE_LINK)
                goto unlock;
 
-       if (!ev->status)
+       if (!ev->status) {
+               bool sec_level_changed =
+                               conn->sec_level != conn->pending_sec_level;
+
                conn->sec_level = conn->pending_sec_level;
+               if (sec_level_changed)
+                       mgmt_security_level_changed(conn);
+       }
 
        clear_bit(HCI_CONN_ENCRYPT_PEND, &conn->flags);
 

@@ -5861,6 +5884,7 @@ static void le_conn_complete_evt(struct hci_dev *hdev, u8 status,
        mgmt_device_connected(hdev, conn, NULL, 0);
 
        conn->sec_level = BT_SECURITY_LOW;
+       mgmt_security_level_changed(conn);
        conn->state = BT_CONFIG;
 
        /* Store current advertising instance as connection advertising instance

net/bluetooth/mgmt.c +49 -1

index 9d3de5a0b8ee..77c958322496 100644
@@ -177,6 +177,7 @@ static const u16 mgmt_events[] = {
        MGMT_EV_CONTROLLER_RESUME,
        MGMT_EV_ADV_MONITOR_DEVICE_FOUND,
        MGMT_EV_ADV_MONITOR_DEVICE_LOST,
+       MGMT_EV_SECURITY_LEVEL_CHANGED,
 };
 
 static const u16 mgmt_untrusted_commands[] = {

@@ -10822,6 +10823,54 @@ void mgmt_device_found(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 link_type,
        mgmt_adv_monitor_device_found(hdev, bdaddr, report_device, skb, NULL);
 }
 
+void mgmt_security_level_changed(struct hci_conn *conn)
+{
+       struct mgmt_ev_security_level_changed *ev;
+       struct mgmt_tlv *tlv;
+       u8 *tlv_data;
+       u8 tlv_len;
+
+       /* Only ACL, LE and BIS links are tracked as mgmt connections, so
+        * restrict the event to those link types. Other transports (SCO,
+        * CIS, PA sync, ...) share the parent's address and would otherwise
+        * report a spurious security level change for it.
+        */
+       if (conn->type != ACL_LINK && conn->type != LE_LINK &&
+           conn->type != BIS_LINK)
+               return;
+
+       tlv_len = 2 * (sizeof(*tlv) + sizeof(__u8));
+       ev = kzalloc_flex(*ev, tlv_data, tlv_len, GFP_KERNEL);
+       if (!ev)
+               return;
+
+       bacpy(&ev->addr.bdaddr, &conn->dst);
+       ev->addr.type = link_to_bdaddr(conn->type, conn->dst_type);
+       ev->tlv_length = tlv_len;
+
+       tlv_data = ev->tlv_data;
+       tlv = (void *)tlv_data;
+       tlv->type = cpu_to_le16(MGMT_SEC_LEVEL_CHANGED_PARAM_LEVEL);
+       tlv->length = sizeof(__u8);
+       tlv->value[0] = conn->sec_level;
+
+       tlv_data += sizeof(*tlv) + sizeof(__u8);
+       tlv = (void *)tlv_data;
+       tlv->type = cpu_to_le16(MGMT_SEC_LEVEL_CHANGED_PARAM_ENC_TYPE);
+       tlv->length = sizeof(__u8);
+       if (!test_bit(HCI_CONN_ENCRYPT, &conn->flags))
+               tlv->value[0] = MGMT_CONN_SEC_ENCRYPT_NONE;
+       else if (test_bit(HCI_CONN_AES_CCM, &conn->flags))
+               tlv->value[0] = MGMT_CONN_SEC_ENCRYPT_AES_CCM;
+       else
+               tlv->value[0] = MGMT_CONN_SEC_ENCRYPT_E0;
+
+       mgmt_event(MGMT_EV_SECURITY_LEVEL_CHANGED, conn->hdev, ev,
+                  struct_size(ev, tlv_data, tlv_len), NULL);
+
+       kfree(ev);
+}
+
 void mgmt_remote_name(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 link_type,
                      u8 addr_type, s8 rssi, u8 *name, u8 name_len)
 {
--

2.43.0