[PATCH] Bluetooth: Fix removing Long Term Key

[PATCH] Bluetooth: Fix removing Long Term Key

[Claudio Takahasi]

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

Signed-off-by: Claudio Takahasi <claudio.takahasi@openbossa.org>
---
 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 */
+	if (ltk->type == HCI_SMP_STK_SLAVE) {
 		list_del(&ltk->list);
 		kfree(ltk);
 	}
-- 
1.7.11.7

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

[Marcel Holtmann]

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 <claudio.takahasi@openbossa.org>
> ---
> 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

[PATCH] Bluetooth: Fix removing Long Term Key

[Claudio Takahasi]

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>
---
 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

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

[Claudio Takahasi]

Hi Vinicius:

On Thu, Jul 25, 2013 at 4:34 PM, Claudio Takahasi
<claudio.takahasi@openbossa.org> 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 <claudio.takahasi@openbossa.org>
> ---
>  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

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

[Vinicius Costa Gomes]

Hi Claudio,

On 17:27 Thu 25 Jul, Claudio Takahasi wrote:
> Hi Vinicius:
> 
> On Thu, Jul 25, 2013 at 4:34 PM, Claudio Takahasi
> <claudio.takahasi@openbossa.org> 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 <claudio.takahasi@openbossa.org>
> > ---
> >  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

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

[Johan Hedberg]

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 <claudio.takahasi@openbossa.org>
> ---
>  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