LinuxLists.cc - [PATCH] Bluetooth: Fix removing Long Term Key

2013-07-25 18:14:17

Subject: [PATCH] Bluetooth: Fix removing Long Term Key

2013-07-25 20:27:17

Subject: Re: [PATCH] Bluetooth: Fix removing Long Term Key

Hi Vinicius:

On Thu, Jul 25, 2013 at 4:34 PM, Claudio Takahasi
<[email protected]> wrote:
> 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 <[email protected]>
> ---
> net/bluetooth/hci_event.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index ae78738..124a5e2 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -3558,7 +3558,13 @@ static void hci_le_ltk_request_evt(struct hci_dev *hdev, struct sk_buff *skb)
>
> 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);
> }
> --
> 1.7.11.7
>

Do you see another alternative?
Is it feasible to avoid adding the STK in the list without adding a
complex logic?

Regards,
Claudio

2013-07-25 19:34:24

by Claudio Takahasi

[permalink] [raw]

Subject: [PATCH] Bluetooth: Fix removing Long Term Key

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 <[email protected]>
---
net/bluetooth/hci_event.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index ae78738..124a5e2 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -3558,7 +3558,13 @@ static void hci_le_ltk_request_evt(struct hci_dev *hdev, struct sk_buff *skb)

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);
}
--
1.7.11.7

2013-07-25 18:25:33

by Marcel Holtmann

[permalink] [raw]

Subject: Re: [PATCH] Bluetooth: Fix removing Long Term Key

Hi Claudio,

> 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

please include a btmon or hcidump trace in the commit message.

> Signed-off-by: Claudio Takahasi <[email protected]>
> ---
> net/bluetooth/hci_event.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index ae78738..ccb93dd 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -3558,7 +3558,8 @@ static void hci_le_ltk_request_evt(struct hci_dev *hdev, struct sk_buff *skb)
>
> hci_send_cmd(hdev, HCI_OP_LE_LTK_REPLY, sizeof(cp), &cp);
>
> - if (ltk->type & HCI_SMP_STK) {
> + /* Use short term key only once */

I think this comment needs to be a bit verbose and explain why. Also reference the spec if possible.

> + if (ltk->type == HCI_SMP_STK_SLAVE) {
> list_del(&ltk->list);
> kfree(ltk);
> }

Regards

Marcel

2013-08-16 03:29:31

by Vinicius Costa Gomes

[permalink] [raw]

Subject: Re: [PATCH] Bluetooth: Fix removing Long Term Key

Hi Claudio,

On 17:27 Thu 25 Jul, Claudio Takahasi wrote:
> Hi Vinicius:
>
> On Thu, Jul 25, 2013 at 4:34 PM, Claudio Takahasi
> <[email protected]> wrote:
> > 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 <[email protected]>
> > ---
> > net/bluetooth/hci_event.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> > index ae78738..124a5e2 100644
> > --- a/net/bluetooth/hci_event.c
> > +++ b/net/bluetooth/hci_event.c
> > @@ -3558,7 +3558,13 @@ static void hci_le_ltk_request_evt(struct hci_dev *hdev, struct sk_buff *skb)
> >
> > 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) {

The correct one should be something like this (not tested):

if (ltk->type == HCI_SMP_STK || ltk->type == HCI_SMP_STK_SLAVE) {

> > list_del(&ltk->list);
> > kfree(ltk);
> > }
> > --
> > 1.7.11.7
> >
>
> Do you see another alternative?
> Is it feasible to avoid adding the STK in the list without adding a
> complex logic?

At least I couldn't find a way. This question made me think about another
problem, if the connection drops between the STK generation and its use to
encrypt the link, it's going to stay there forever.

>
> Regards,
> Claudio

Cheers,
--
Vinicius

2014-03-05 18:58:13

by Johan Hedberg

[permalink] [raw]

Subject: Re: [PATCH] Bluetooth: Fix removing Long Term Key

Hi Claudio,

On Thu, Jul 25, 2013, Claudio Takahasi wrote:
> 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 <[email protected]>
> ---
> net/bluetooth/hci_event.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)

The patch has now (finally) been applied to the bluetooth-next tree.
I also added a Cc: stable flag to it since this is a fairly severe issue
at least for any kernel with the advertising mgmt setting.

Johan