[PATCH 3.13 14/32] Bluetooth: Fix removing Long Term Key

Greg Kroah-Hartman
2014-04-21T04:37:31Z

From: Claudio Takahasi <claudio.takahasi@openbossa.org>

commit 5981a8821b774ada0be512fd9bad7c241e17657e upstream.

This patch fixes authentication failure on LE link re-connection when
BlueZ acts as slave (peripheral). LTK is removed from the internal list
after its first use causing PIN or Key missing reply when re-connecting
the link. The LE Long Term Key Request event indicates that the master
is attempting to encrypt or re-encrypt the link.

Pre-condition: BlueZ host paired and running as slave.
How to reproduce(master):

1) Establish an ACL LE encrypted link
2) Disconnect the link
3) Try to re-establish the ACL LE encrypted link (fails)

> HCI Event: LE Meta Event (0x3e) plen 19
LE Connection Complete (0x01)
Status: Success (0x00)
Handle: 64
Role: Slave (0x01)
...
@ Device Connected: 00:02:72:DC:29:C9 (1) flags 0x0000
> HCI Event: LE Meta Event (0x3e) plen 13
LE Long Term Key Request (0x05)
Handle: 64
Random number: 875be18439d9aa37
Encryption diversifier: 0x76ed
< HCI Command: LE Long Term Key Request Reply (0x08|0x001a) plen 18
Handle: 64
Long term key: 2aa531db2fce9f00a0569c7d23d17409
> HCI Event: Command Complete (0x0e) plen 6
LE Long Term Key Request Reply (0x08|0x001a) ncmd 1
Status: Success (0x00)
Handle: 64
> HCI Event: Encryption Change (0x08) plen 4
Status: Success (0x00)
Handle: 64
Encryption: Enabled with AES-CCM (0x01)
...
@ Device Disconnected: 00:02:72:DC:29:C9 (1) reason 3
< HCI Command: LE Set Advertise Enable (0x08|0x000a) plen 1
Advertising: Enabled (0x01)
> HCI Event: Command Complete (0x0e) plen 4
LE Set Advertise Enable (0x08|0x000a) ncmd 1
Status: Success (0x00)
> HCI Event: LE Meta Event (0x3e) plen 19
LE Connection Complete (0x01)
Status: Success (0x00)
Handle: 64
Role: Slave (0x01)
...
@ Device Connected: 00:02:72:DC:29:C9 (1) flags 0x0000
> HCI Event: LE Meta Event (0x3e) plen 13
LE Long Term Key Request (0x05)
Handle: 64
Random number: 875be18439d9aa37
Encryption diversifier: 0x76ed
< HCI Command: LE Long Term Key Request Neg Reply (0x08|0x001b) plen 2
Handle: 64
> HCI Event: Command Complete (0x0e) plen 6
LE Long Term Key Request Neg Reply (0x08|0x001b) ncmd 1
Status: Success (0x00)
Handle: 64
> HCI Event: Disconnect Complete (0x05) plen 4
Status: Success (0x00)
Handle: 64
Reason: Authentication Failure (0x05)
@ Device Disconnected: 00:02:72:DC:29:C9 (1) reason 0

Signed-off-by: Claudio Takahasi <claudio.takahasi@openbossa.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/bluetooth/hci_event.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -3596,7 +3596,13 @@ static void hci_le_ltk_request_evt(struc

hci_send_cmd(hdev, HCI_OP_LE_LTK_REPLY, sizeof(cp), &cp);

- if (ltk->type & HCI_SMP_STK) {
+ /* Ref. Bluetooth Core SPEC pages 1975 and 2004. STK is a
+ * temporary key used to encrypt a connection following
+ * pairing. It is used during the Encrypted Session Setup to
+ * distribute the keys. Later, security can be re-established
+ * using a distributed LTK.
+ */
+ if (ltk->type == HCI_SMP_STK_SLAVE) {
list_del(&ltk->list);
kfree(ltk);
}