[PATCH 5.4 135/215] Bluetooth: hci_event: set the conn encrypted before conn establishes

Greg Kroah-Hartman
2024-04-11T10:20:41Z

From: Hui Wang <hui.wang@canonical.com>

commit c569242cd49287d53b73a94233db40097d838535 upstream.

We have a BT headset (Lenovo Thinkplus XT99), the pairing and
connecting has no problem, once this headset is paired, bluez will
remember this device and will auto re-connect it whenever the device
is powered on. The auto re-connecting works well with Windows and
Android, but with Linux, it always fails. Through debugging, we found
at the rfcomm connection stage, the bluetooth stack reports
"Connection refused - security block (0x0003)".

For this device, the re-connecting negotiation process is different
from other BT headsets, it sends the Link_KEY_REQUEST command before
the CONNECT_REQUEST completes, and it doesn't send ENCRYPT_CHANGE
command during the negotiation. When the device sends the "connect
complete" to hci, the ev->encr_mode is 1.

So here in the conn_complete_evt(), if ev->encr_mode is 1, link type
is ACL and HCI_CONN_ENCRYPT is not set, we set HCI_CONN_ENCRYPT to
this conn, and update conn->enc_key_size accordingly.

After this change, this BT headset could re-connect with Linux
successfully. This is the btmon log after applying the patch, after
receiving the "Connect Complete" with "Encryption: Enabled", will send
the command to read encryption key size:
> HCI Event: Connect Request (0x04) plen 10
Address: 8C:3C:AA:D8:11:67 (OUI 8C-3C-AA)
Class: 0x240404
Major class: Audio/Video (headset, speaker, stereo, video, vcr)
Minor class: Wearable Headset Device
Rendering (Printing, Speaker)
Audio (Speaker, Microphone, Headset)
Link type: ACL (0x01)
...
> HCI Event: Link Key Request (0x17) plen 6
Address: 8C:3C:AA:D8:11:67 (OUI 8C-3C-AA)
< HCI Command: Link Key Request Reply (0x01|0x000b) plen 22
Address: 8C:3C:AA:D8:11:67 (OUI 8C-3C-AA)
Link key: ${32-hex-digits-key}
...
> HCI Event: Connect Complete (0x03) plen 11
Status: Success (0x00)
Handle: 256
Address: 8C:3C:AA:D8:11:67 (OUI 8C-3C-AA)
Link type: ACL (0x01)
Encryption: Enabled (0x01)
< HCI Command: Read Encryption Key... (0x05|0x0008) plen 2
Handle: 256
< ACL Data TX: Handle 256 flags 0x00 dlen 10
L2CAP: Information Request (0x0a) ident 1 len 2
Type: Extended features supported (0x0002)
> HCI Event: Command Complete (0x0e) plen 7
Read Encryption Key Size (0x05|0x0008) ncmd 1
Status: Success (0x00)
Handle: 256
Key size: 16

Cc: stable@vger.kernel.org
Link: https://github.com/bluez/bluez/issues/704
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-by: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/bluetooth/hci_event.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -2537,6 +2537,31 @@ static void hci_conn_complete_evt(struct
if (test_bit(HCI_ENCRYPT, &hdev->flags))
set_bit(HCI_CONN_ENCRYPT, &conn->flags);

+ /* "Link key request" completed ahead of "connect request" completes */
+ if (ev->encr_mode == 1 && !test_bit(HCI_CONN_ENCRYPT, &conn->flags) &&
+ ev->link_type == ACL_LINK) {
+ struct link_key *key;
+ struct hci_cp_read_enc_key_size cp;
+
+ key = hci_find_link_key(hdev, &ev->bdaddr);
+ if (key) {
+ set_bit(HCI_CONN_ENCRYPT, &conn->flags);
+
+ if (!(hdev->commands[20] & 0x10)) {
+ conn->enc_key_size = HCI_LINK_KEY_SIZE;
+ } else {
+ cp.handle = cpu_to_le16(conn->handle);
+ if (hci_send_cmd(hdev, HCI_OP_READ_ENC_KEY_SIZE,
+ sizeof(cp), &cp)) {
+ bt_dev_err(hdev, "sending read key size failed");
+ conn->enc_key_size = HCI_LINK_KEY_SIZE;
+ }
+ }
+
+ hci_encrypt_cfm(conn, ev->status);
+ }
+ }
+
/* Get remote features */
if (conn->type == ACL_LINK) {
struct hci_cp_read_remote_features cp;