Re: [PATCH 4/5] android/gatt: Always connect with BT_SEC_LOW security

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Hi Lukasz,

On Wed, Jul 30, 2014 at 2:37 PM, Lukasz Rymanowski
<lukasz.rymanowski@xxxxxxxxx> wrote:
> Hi Luiz,
>
> On Wed, Jul 30, 2014 at 12:41 PM, Luiz Augusto von Dentz
> <luiz.dentz@xxxxxxxxx> wrote:
>> Hi Marcin,
>>
>> On Wed, Jul 30, 2014 at 12:38 PM, Marcin Kraglak
>> <marcin.kraglak@xxxxxxxxx> wrote:
>>> Set BT_SEC_LOW for all LE connections. Only specific profiles need
>>> higher security, now it is possible to elevate security with public
>>> GATT API.
>>> ---
>>>  android/gatt.c | 6 +-----
>>>  1 file changed, 1 insertion(+), 5 deletions(-)
>>>
>>> diff --git a/android/gatt.c b/android/gatt.c
>>> index 49ca2b6..11d7a2c 100644
>>> --- a/android/gatt.c
>>> +++ b/android/gatt.c
>>> @@ -1433,7 +1433,6 @@ reply:
>>>
>>>  static int connect_le(struct gatt_device *dev)
>>>  {
>>> -       BtIOSecLevel sec_level;
>>>         GIOChannel *io;
>>>         GError *gerr = NULL;
>>>         char addr[18];
>>> @@ -1450,9 +1449,6 @@ static int connect_le(struct gatt_device *dev)
>>>
>>>         DBG("Connection attempt to: %s", addr);
>>>
>>> -       sec_level = bt_device_is_bonded(&dev->bdaddr) ? BT_IO_SEC_MEDIUM :
>>> -                                                               BT_IO_SEC_LOW;
>>> -
>>>         /*
>>>          * If address type is random it might be that IRK was received and
>>>          * random is just for faking Android Framework. ID address should be
>>> @@ -1478,7 +1474,7 @@ static int connect_le(struct gatt_device *dev)
>>>                         BT_IO_OPT_DEST_BDADDR, bdaddr,
>>>                         BT_IO_OPT_DEST_TYPE, bdaddr_type,
>>>                         BT_IO_OPT_CID, ATT_CID,
>>> -                       BT_IO_OPT_SEC_LEVEL, sec_level,
>>> +                       BT_IO_OPT_SEC_LEVEL, BT_IO_SEC_LOW,
>>>                         BT_IO_OPT_INVALID);
>>>         if (!io) {
>>>                 error("gatt: Failed bt_io_connect(%s): %s", addr,
>>> --
>>> 1.9.3
>>
>> This does not work for HoG:
>>
>> "If the HID Host receives the L2CAP Connection Parameter Update
>> request but has not
>> yet completed service discovery or has not completed encryption, the
>> HID Host may
>> send the L2CAP Connection Parameter Update Response with the Result field
>> indicating that the request has been rejected."
>>
>
> I think that with "[PATCH 3/5] anroid/hidhost: Set security to MEDUIM
> after connect"  there is no issue with HOG.
> That patch basically triggers pairing or enable encryption (if device
> are bonded) just after LE link is created.

It depends when the connection parameter update is sent, if it is
before the userspace can upgrade the security requirement and the
remote device rejects it then it might never update. Anyway, the
argument bellow still stand, why would you have LTK distributed and
not encrypt?

Id say the very purpose of signed writes is meant for when you don't
have LTK, but perhaps Im missing something.

>> IMO what we should do instead is pass what security level we want
>> based on the profiles that has requested the connection, in case of
>> HoG then we can set medium security and other might set it to low,
>> note that elevating security later is less secure then having it from
>> the start so I hope this is not just to fulfill some stupid PTS test
>> that does bonding but requires not to encrypt.
>>
>>
>> --
>> Luiz Augusto von Dentz
>> --
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>
> BR
> Lukasz



-- 
Luiz Augusto von Dentz
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