[PATCH v1] hog: Check security level before setting

[PATCH v1] hog: Check security level before setting

[Jiayang Mao]

bt_gatt_client_set_security could fail if the security level is
already BT_ATT_SECURITY_MEDIUM. So, get and check the security
level before setting it.

Signed-off-by: Jiayang Mao <quic_jiaymao@quicinc.com>
---
 profiles/input/hog.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/profiles/input/hog.c b/profiles/input/hog.c
index 017e320f0..011cc0a88 100644
--- a/profiles/input/hog.c
+++ b/profiles/input/hog.c
@@ -191,8 +191,10 @@ static int hog_accept(struct btd_service *service)
 			return -ECONNREFUSED;
 
 		client = btd_device_get_gatt_client(device);
-		if (!bt_gatt_client_set_security(client,
-						BT_ATT_SECURITY_MEDIUM))
+		if (BT_ATT_SECURITY_MEDIUM !=
+			bt_gatt_client_get_security(client) &&
+		    !bt_gatt_client_set_security(client,
+						 BT_ATT_SECURITY_MEDIUM))
 			return -ECONNREFUSED;
 	}
 
-- 
2.25.1

RE: [v1] hog: Check security level before setting

[bluez.test.bot]

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This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=910561

---Test result---

Test Summary:
CheckPatch                    PENDING   0.23 seconds
GitLint                       PENDING   0.18 seconds
BuildEll                      PASS      20.45 seconds
BluezMake                     PASS      1523.29 seconds
MakeCheck                     PASS      13.00 seconds
MakeDistcheck                 PASS      159.15 seconds
CheckValgrind                 PASS      213.41 seconds
CheckSmatch                   PASS      272.24 seconds
bluezmakeextell               PASS      98.55 seconds
IncrementalBuild              PENDING   0.29 seconds
ScanBuild                     PASS      839.87 seconds

Details
##############################
Test: CheckPatch - PENDING
Desc: Run checkpatch.pl script
Output:

##############################
Test: GitLint - PENDING
Desc: Run gitlint
Output:

##############################
Test: IncrementalBuild - PENDING
Desc: Incremental build with the patches in the series
Output:



---
Regards,
Linux Bluetooth

Re: [PATCH v1] hog: Check security level before setting

[Luiz Augusto von Dentz]

Hi Jiayang,

On Mon, Nov 18, 2024 at 4:49 AM Jiayang Mao <quic_jiaymao@quicinc.com> wrote:
>
> bt_gatt_client_set_security could fail if the security level is
> already BT_ATT_SECURITY_MEDIUM. So, get and check the security
> level before setting it.

Seems a bit strange that this is not handled by the kernel, can you
elaborate on the conditions to trigger it?

> Signed-off-by: Jiayang Mao <quic_jiaymao@quicinc.com>
> ---
>  profiles/input/hog.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/profiles/input/hog.c b/profiles/input/hog.c
> index 017e320f0..011cc0a88 100644
> --- a/profiles/input/hog.c
> +++ b/profiles/input/hog.c
> @@ -191,8 +191,10 @@ static int hog_accept(struct btd_service *service)
>                         return -ECONNREFUSED;
>
>                 client = btd_device_get_gatt_client(device);
> -               if (!bt_gatt_client_set_security(client,
> -                                               BT_ATT_SECURITY_MEDIUM))
> +               if (BT_ATT_SECURITY_MEDIUM !=
> +                       bt_gatt_client_get_security(client) &&
> +                   !bt_gatt_client_set_security(client,
> +                                                BT_ATT_SECURITY_MEDIUM))
>                         return -ECONNREFUSED;


Definitely not the right way to fix this since there might be other
places that do attempt to set the security, so Id got with something
like the following:

diff --git a/src/shared/att.c b/src/shared/att.c
index 4a406f4b91a4..dabbdb4315eb 100644
--- a/src/shared/att.c
+++ b/src/shared/att.c
@@ -727,6 +727,9 @@ static bool bt_att_chan_set_security(struct
bt_att_chan *chan, int level)
 {
        struct bt_security sec;

+       if (level == bt_att_chan_get_security(chan))
+               return true;
+
        if (chan->type == BT_ATT_LOCAL) {
                chan->sec_level = level;
                return true;

>         }
>
> --
> 2.25.1
>
>


-- 
Luiz Augusto von Dentz

Re: [PATCH v1] hog: Check security level before setting

[Jiayang Mao]

Hi Luiz,

On 2024/11/18 23:13, Luiz Augusto von Dentz wrote:
> Hi Jiayang,
> 
> On Mon, Nov 18, 2024 at 4:49 AM Jiayang Mao <quic_jiaymao@quicinc.com> wrote:
>>
>> bt_gatt_client_set_security could fail if the security level is
>> already BT_ATT_SECURITY_MEDIUM. So, get and check the security
>> level before setting it.
> 
> Seems a bit strange that this is not handled by the kernel, can you
> elaborate on the conditions to trigger it?
> 

In the kernel, the failure happens when smp_sufficient_security() in
'net/bluetooth/smp.c' returns true. In some cases, when security level
is already MEDIUM but long term key is not ready, setting security level
will fail. Checking security level before setting it can prevent this
failure.

>> Signed-off-by: Jiayang Mao <quic_jiaymao@quicinc.com>
>> ---
>>   profiles/input/hog.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/profiles/input/hog.c b/profiles/input/hog.c
>> index 017e320f0..011cc0a88 100644
>> --- a/profiles/input/hog.c
>> +++ b/profiles/input/hog.c
>> @@ -191,8 +191,10 @@ static int hog_accept(struct btd_service *service)
>>                          return -ECONNREFUSED;
>>
>>                  client = btd_device_get_gatt_client(device);
>> -               if (!bt_gatt_client_set_security(client,
>> -                                               BT_ATT_SECURITY_MEDIUM))
>> +               if (BT_ATT_SECURITY_MEDIUM !=
>> +                       bt_gatt_client_get_security(client) &&
>> +                   !bt_gatt_client_set_security(client,
>> +                                                BT_ATT_SECURITY_MEDIUM))
>>                          return -ECONNREFUSED;
> 
> 
> Definitely not the right way to fix this since there might be other
> places that do attempt to set the security, so Id got with something
> like the following:
> 
> diff --git a/src/shared/att.c b/src/shared/att.c
> index 4a406f4b91a4..dabbdb4315eb 100644
> --- a/src/shared/att.c
> +++ b/src/shared/att.c
> @@ -727,6 +727,9 @@ static bool bt_att_chan_set_security(struct
> bt_att_chan *chan, int level)
>   {
>          struct bt_security sec;
> 
> +       if (level == bt_att_chan_get_security(chan))
> +               return true;
> +
>          if (chan->type == BT_ATT_LOCAL) {
>                  chan->sec_level = level;
>                  return true;
> 
>>          }
>>
>> --
>> 2.25.1
>>
>>
> 
> 

Re: [PATCH v1] hog: Check security level before setting

[Luiz Augusto von Dentz]

Hi Jiayang,

On Mon, Nov 18, 2024 at 10:23 PM Jiayang Mao <quic_jiaymao@quicinc.com> wrote:
>
> Hi Luiz,
>
> On 2024/11/18 23:13, Luiz Augusto von Dentz wrote:
> > Hi Jiayang,
> >
> > On Mon, Nov 18, 2024 at 4:49 AM Jiayang Mao <quic_jiaymao@quicinc.com> wrote:
> >>
> >> bt_gatt_client_set_security could fail if the security level is
> >> already BT_ATT_SECURITY_MEDIUM. So, get and check the security
> >> level before setting it.
> >
> > Seems a bit strange that this is not handled by the kernel, can you
> > elaborate on the conditions to trigger it?
> >
>
> In the kernel, the failure happens when smp_sufficient_security() in
> 'net/bluetooth/smp.c' returns true. In some cases, when security level
> is already MEDIUM but long term key is not ready, setting security level
> will fail. Checking security level before setting it can prevent this
> failure.

Hmm, is this about encryption change happening before the LTK is
distributed? Ive seen that sometimes remote devices also have this
problem e.g. GATT read return encryption required error but the link
is already encrypted.

Btw, I assume the problem is in this following code:

https://github.com/torvalds/linux/blob/master/net/bluetooth/l2cap_sock.c#L931

That would fail with 1 because smp_sufficient_security would return
true but we assume that to be an error, well it is an error but I
guess it should have been -EALREADY that way one does not need to
check the error again:

diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index 18e89e764f3b..ada0915c7421 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -919,6 +919,11 @@ static int l2cap_sock_setsockopt(struct socket
*sock, int level, int optname,
                        break;
                }

+               if (chan->sec_level == sec.level) {
+                       err = -EALREADY;
+                       break;
+               }
+
                chan->sec_level = sec.level;

                if (!chan->conn)

Anyway I think it is safer to do that on userspace first so it acts
properly with older kernels.

> >> Signed-off-by: Jiayang Mao <quic_jiaymao@quicinc.com>
> >> ---
> >>   profiles/input/hog.c | 6 ++++--
> >>   1 file changed, 4 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/profiles/input/hog.c b/profiles/input/hog.c
> >> index 017e320f0..011cc0a88 100644
> >> --- a/profiles/input/hog.c
> >> +++ b/profiles/input/hog.c
> >> @@ -191,8 +191,10 @@ static int hog_accept(struct btd_service *service)
> >>                          return -ECONNREFUSED;
> >>
> >>                  client = btd_device_get_gatt_client(device);
> >> -               if (!bt_gatt_client_set_security(client,
> >> -                                               BT_ATT_SECURITY_MEDIUM))
> >> +               if (BT_ATT_SECURITY_MEDIUM !=
> >> +                       bt_gatt_client_get_security(client) &&
> >> +                   !bt_gatt_client_set_security(client,
> >> +                                                BT_ATT_SECURITY_MEDIUM))
> >>                          return -ECONNREFUSED;
> >
> >
> > Definitely not the right way to fix this since there might be other
> > places that do attempt to set the security, so Id got with something
> > like the following:
> >
> > diff --git a/src/shared/att.c b/src/shared/att.c
> > index 4a406f4b91a4..dabbdb4315eb 100644
> > --- a/src/shared/att.c
> > +++ b/src/shared/att.c
> > @@ -727,6 +727,9 @@ static bool bt_att_chan_set_security(struct
> > bt_att_chan *chan, int level)
> >   {
> >          struct bt_security sec;
> >
> > +       if (level == bt_att_chan_get_security(chan))
> > +               return true;
> > +
> >          if (chan->type == BT_ATT_LOCAL) {
> >                  chan->sec_level = level;
> >                  return true;
> >
> >>          }
> >>
> >> --
> >> 2.25.1
> >>
> >>
> >
> >
>


-- 
Luiz Augusto von Dentz

Re: [PATCH v1] hog: Check security level before setting

[Jiayang Mao]

Hi Luiz,

On 2024/11/20 0:23, Luiz Augusto von Dentz wrote:
> Hi Jiayang,
> 
> On Mon, Nov 18, 2024 at 10:23 PM Jiayang Mao <quic_jiaymao@quicinc.com> wrote:
>>
>> Hi Luiz,
>>
>> On 2024/11/18 23:13, Luiz Augusto von Dentz wrote:
>>> Hi Jiayang,
>>>
>>> On Mon, Nov 18, 2024 at 4:49 AM Jiayang Mao <quic_jiaymao@quicinc.com> wrote:
>>>>
>>>> bt_gatt_client_set_security could fail if the security level is
>>>> already BT_ATT_SECURITY_MEDIUM. So, get and check the security
>>>> level before setting it.
>>>
>>> Seems a bit strange that this is not handled by the kernel, can you
>>> elaborate on the conditions to trigger it?
>>>
>>
>> In the kernel, the failure happens when smp_sufficient_security() in
>> 'net/bluetooth/smp.c' returns true. In some cases, when security level
>> is already MEDIUM but long term key is not ready, setting security level
>> will fail. Checking security level before setting it can prevent this
>> failure.
> 
> Hmm, is this about encryption change happening before the LTK is
> distributed? Ive seen that sometimes remote devices also have this
> problem e.g. GATT read return encryption required error but the link
> is already encrypted.
> 
> Btw, I assume the problem is in this following code:
> 
> https://github.com/torvalds/linux/blob/master/net/bluetooth/l2cap_sock.c#L931
> 
> That would fail with 1 because smp_sufficient_security would return
> true but we assume that to be an error, well it is an error but I
> guess it should have been -EALREADY that way one does not need to
> check the error again:
> 
> diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
> index 18e89e764f3b..ada0915c7421 100644
> --- a/net/bluetooth/l2cap_sock.c
> +++ b/net/bluetooth/l2cap_sock.c
> @@ -919,6 +919,11 @@ static int l2cap_sock_setsockopt(struct socket
> *sock, int level, int optname,
>                          break;
>                  }
> 
> +               if (chan->sec_level == sec.level) {
> +                       err = -EALREADY;
> +                       break;
> +               }
> +
>                  chan->sec_level = sec.level;
> 
>                  if (!chan->conn)
> 
> Anyway I think it is safer to do that on userspace first so it acts
> properly with older kernels.
> 

Thanks. Following your previous suggestion, I updated another patch to
move the change to att.c:
[v1] att: Check security level before setting

>>>> Signed-off-by: Jiayang Mao <quic_jiaymao@quicinc.com>
>>>> ---
>>>>    profiles/input/hog.c | 6 ++++--
>>>>    1 file changed, 4 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/profiles/input/hog.c b/profiles/input/hog.c
>>>> index 017e320f0..011cc0a88 100644
>>>> --- a/profiles/input/hog.c
>>>> +++ b/profiles/input/hog.c
>>>> @@ -191,8 +191,10 @@ static int hog_accept(struct btd_service *service)
>>>>                           return -ECONNREFUSED;
>>>>
>>>>                   client = btd_device_get_gatt_client(device);
>>>> -               if (!bt_gatt_client_set_security(client,
>>>> -                                               BT_ATT_SECURITY_MEDIUM))
>>>> +               if (BT_ATT_SECURITY_MEDIUM !=
>>>> +                       bt_gatt_client_get_security(client) &&
>>>> +                   !bt_gatt_client_set_security(client,
>>>> +                                                BT_ATT_SECURITY_MEDIUM))
>>>>                           return -ECONNREFUSED;
>>>
>>>
>>> Definitely not the right way to fix this since there might be other
>>> places that do attempt to set the security, so Id got with something
>>> like the following:
>>>
>>> diff --git a/src/shared/att.c b/src/shared/att.c
>>> index 4a406f4b91a4..dabbdb4315eb 100644
>>> --- a/src/shared/att.c
>>> +++ b/src/shared/att.c
>>> @@ -727,6 +727,9 @@ static bool bt_att_chan_set_security(struct
>>> bt_att_chan *chan, int level)
>>>    {
>>>           struct bt_security sec;
>>>
>>> +       if (level == bt_att_chan_get_security(chan))
>>> +               return true;
>>> +
>>>           if (chan->type == BT_ATT_LOCAL) {
>>>                   chan->sec_level = level;
>>>                   return true;
>>>
>>>>           }
>>>>
>>>> --
>>>> 2.25.1
>>>>
>>>>
>>>
>>>
>>
> 
>