* [PATCH v2] Bluetooth: Fix reporting incorrect EIR in device found mgmt event
@ 2015-05-14 10:48 Szymon Janc
2015-05-19 19:17 ` Marcel Holtmann
0 siblings, 1 reply; 4+ messages in thread
From: Szymon Janc @ 2015-05-14 10:48 UTC (permalink / raw)
To: linux-bluetooth; +Cc: Szymon Janc
Some remote devices (ie Gigaset G-Tag) misbehave with ADV data length.
This can lead to incorrect EIR format in device found event when
ADV_DATA and SCAN_RSP are merged (terminator field before SCAN_RSP
part).
Fix this by inspecting ADV_DATA and correct its length if terminator
is found.
> HCI Event: LE Meta Event (0x3e) plen 42 [hci0] 32.172182
LE Advertising Report (0x02)
Num reports: 1
Event type: Connectable undirected - ADV_IND (0x00)
Address type: Public (0x00)
Address: 7C:2F:80:94:97:5A (Gigaset Communications GmbH)
Data length: 30
Flags: 0x06
LE General Discoverable Mode
BR/EDR Not Supported
Company: Gigaset Communications GmbH (384)
Data: 021512348094975abbc5
16-bit Service UUIDs (partial): 1 entry
Battery Service (0x180f)
RSSI: -65 dBm (0xbf)
> HCI Event: LE Meta Event (0x3e) plen 27 [hci0] 32.172191
LE Advertising Report (0x02)
Num reports: 1
Event type: Scan response - SCAN_RSP (0x04)
Address type: Public (0x00)
Address: 7C:2F:80:94:97:5A (Gigaset Communications GmbH)
Data length: 15
Name (complete): Gigaset G-tag
RSSI: -59 dBm (0xc5)
Note "Data length: 30" in ADV_DATA which results in 9 extra zero bytes
after Battery Service UUID. Terminator field present in the middle of
EIR in Device Found event resulted in userspace stop parsing EIR and
skipping device name.
@ Device Found: 7C:2F:80:94:97:5A (1) rssi -59 flags 0x0000
02 01 06 0d ff 80 01 02 15 12 34 80 94 97 5a bb ..........4...Z.
c5 03 02 0f 18 00 00 00 00 00 00 00 00 00 0e 09 ................
47 69 67 61 73 65 74 20 47 2d 74 61 67 Gigaset G-tag
With this fix EIR with merged ADV_DATA and SCAN_RSP in device found
event is properly formatted:
@ Device Found: 7C:2F:80:94:97:5A (1) rssi -59 flags 0x0000
02 01 06 0d ff 80 01 02 15 12 34 80 94 97 5a bb ..........4...Z.
c5 03 02 0f 18 0e 09 47 69 67 61 73 65 74 20 47 .......Gigaset G
2d 74 61 67 -tag
Signed-off-by: Szymon Janc <szymon.janc@tieto.com>
---
v2: fixed build error due to use of non-upstream BT_ERR_RATELIMITED
net/bluetooth/hci_event.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 7b61be7..0407324 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4711,6 +4711,23 @@ static void process_adv_report(struct hci_dev *hdev, u8 type, bdaddr_t *bdaddr,
struct hci_conn *conn;
bool match;
u32 flags;
+ u8 *ptr, real_len;
+
+ /* Find the 'real' end of the data in case remote incorrectly
+ * set significant part length.
+ */
+ for (ptr = data; ptr < data + len && *ptr; ptr += *ptr + 1) {
+ if (ptr + 1 + *ptr > data + len)
+ break;
+ }
+
+ real_len = ptr - data;
+
+ /* Adjust for actual length */
+ if (len != real_len) {
+ BT_ERR("Corrected invalid ADV_DATA length");
+ len = real_len;
+ }
/* If the direct address is present, then this report is from
* a LE Direct Advertising Report event. In that case it is
--
1.9.3
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH v2] Bluetooth: Fix reporting incorrect EIR in device found mgmt event
2015-05-14 10:48 [PATCH v2] Bluetooth: Fix reporting incorrect EIR in device found mgmt event Szymon Janc
@ 2015-05-19 19:17 ` Marcel Holtmann
2015-05-20 19:55 ` Szymon Janc
0 siblings, 1 reply; 4+ messages in thread
From: Marcel Holtmann @ 2015-05-19 19:17 UTC (permalink / raw)
To: Szymon Janc; +Cc: linux-bluetooth
Hi Szymon,
> Some remote devices (ie Gigaset G-Tag) misbehave with ADV data length.
> This can lead to incorrect EIR format in device found event when
> ADV_DATA and SCAN_RSP are merged (terminator field before SCAN_RSP
> part).
>
> Fix this by inspecting ADV_DATA and correct its length if terminator
> is found.
>
>> HCI Event: LE Meta Event (0x3e) plen 42 [hci0] 32.172182
> LE Advertising Report (0x02)
> Num reports: 1
> Event type: Connectable undirected - ADV_IND (0x00)
> Address type: Public (0x00)
> Address: 7C:2F:80:94:97:5A (Gigaset Communications GmbH)
> Data length: 30
> Flags: 0x06
> LE General Discoverable Mode
> BR/EDR Not Supported
> Company: Gigaset Communications GmbH (384)
> Data: 021512348094975abbc5
> 16-bit Service UUIDs (partial): 1 entry
> Battery Service (0x180f)
> RSSI: -65 dBm (0xbf)
>> HCI Event: LE Meta Event (0x3e) plen 27 [hci0] 32.172191
> LE Advertising Report (0x02)
> Num reports: 1
> Event type: Scan response - SCAN_RSP (0x04)
> Address type: Public (0x00)
> Address: 7C:2F:80:94:97:5A (Gigaset Communications GmbH)
> Data length: 15
> Name (complete): Gigaset G-tag
> RSSI: -59 dBm (0xc5)
>
> Note "Data length: 30" in ADV_DATA which results in 9 extra zero bytes
> after Battery Service UUID. Terminator field present in the middle of
> EIR in Device Found event resulted in userspace stop parsing EIR and
> skipping device name.
>
> @ Device Found: 7C:2F:80:94:97:5A (1) rssi -59 flags 0x0000
> 02 01 06 0d ff 80 01 02 15 12 34 80 94 97 5a bb ..........4...Z.
> c5 03 02 0f 18 00 00 00 00 00 00 00 00 00 0e 09 ................
> 47 69 67 61 73 65 74 20 47 2d 74 61 67 Gigaset G-tag
>
> With this fix EIR with merged ADV_DATA and SCAN_RSP in device found
> event is properly formatted:
>
> @ Device Found: 7C:2F:80:94:97:5A (1) rssi -59 flags 0x0000
> 02 01 06 0d ff 80 01 02 15 12 34 80 94 97 5a bb ..........4...Z.
> c5 03 02 0f 18 0e 09 47 69 67 61 73 65 74 20 47 .......Gigaset G
> 2d 74 61 67 -tag
>
> Signed-off-by: Szymon Janc <szymon.janc@tieto.com>
> ---
> v2: fixed build error due to use of non-upstream BT_ERR_RATELIMITED
>
> net/bluetooth/hci_event.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index 7b61be7..0407324 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -4711,6 +4711,23 @@ static void process_adv_report(struct hci_dev *hdev, u8 type, bdaddr_t *bdaddr,
> struct hci_conn *conn;
> bool match;
> u32 flags;
> + u8 *ptr, real_len;
> +
> + /* Find the 'real' end of the data in case remote incorrectly
> + * set significant part length.
I do not understand this sentence. I assume what you want to say find the end of the data in case the report contains padded zero bytes at the end causing an invalid length value.
> + */
> + for (ptr = data; ptr < data + len && *ptr; ptr += *ptr + 1) {
> + if (ptr + 1 + *ptr > data + len)
> + break;
> + }
I am worried about the unchecked usage of *ptr here. That might let you jump into some memory area. How are we protecting this against malicious advertising data. And we should have mgnt-tester test cases for malicious fields that are not valid data and would make you jump outside of the 31 bytes.
> +
> + real_len = ptr - data;
> +
> + /* Adjust for actual length */
> + if (len != real_len) {
> + BT_ERR("Corrected invalid ADV_DATA length”);
I would spell advertising report data length here. There really is no ADV_DATA anywhere in the specification or used in BlueZ like that.
Regards
Marcel
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] Bluetooth: Fix reporting incorrect EIR in device found mgmt event
2015-05-19 19:17 ` Marcel Holtmann
@ 2015-05-20 19:55 ` Szymon Janc
2015-05-25 19:32 ` Marcel Holtmann
0 siblings, 1 reply; 4+ messages in thread
From: Szymon Janc @ 2015-05-20 19:55 UTC (permalink / raw)
To: Marcel Holtmann; +Cc: Szymon Janc, linux-bluetooth
Hi Marcel,
On Tuesday 19 May 2015 21:17:40 Marcel Holtmann wrote:
> Hi Szymon,
>=20
> > Some remote devices (ie Gigaset G-Tag) misbehave with ADV data leng=
th.
> > This can lead to incorrect EIR format in device found event when
> > ADV_DATA and SCAN_RSP are merged (terminator field before SCAN_RSP
> > part).
> >=20
> > Fix this by inspecting ADV_DATA and correct its length if terminato=
r
> > is found.
> >=20
> >> HCI Event: LE Meta Event (0x3e) plen 42 [hci0] 32.172=
182
> >>=20
> > LE Advertising Report (0x02)
> > =20
> > Num reports: 1
> > Event type: Connectable undirected - ADV_IND (0x00)
> > Address type: Public (0x00)
> > Address: 7C:2F:80:94:97:5A (Gigaset Communications GmbH)
> > Data length: 30
> > Flags: 0x06
> > =20
> > LE General Discoverable Mode
> > BR/EDR Not Supported
> > =20
> > Company: Gigaset Communications GmbH (384)
> > =20
> > Data: 021512348094975abbc5
> > =20
> > 16-bit Service UUIDs (partial): 1 entry
> > =20
> > Battery Service (0x180f)
> > =20
> > RSSI: -65 dBm (0xbf)
> >>=20
> >> HCI Event: LE Meta Event (0x3e) plen 27 [hci0] 32.172=
191
> >>=20
> > LE Advertising Report (0x02)
> > =20
> > Num reports: 1
> > Event type: Scan response - SCAN_RSP (0x04)
> > Address type: Public (0x00)
> > Address: 7C:2F:80:94:97:5A (Gigaset Communications GmbH)
> > Data length: 15
> > Name (complete): Gigaset G-tag
> > RSSI: -59 dBm (0xc5)
> >=20
> > Note "Data length: 30" in ADV_DATA which results in 9 extra zero by=
tes
> > after Battery Service UUID. Terminator field present in the middle =
of
> > EIR in Device Found event resulted in userspace stop parsing EIR an=
d
> > skipping device name.
> >=20
> > @ Device Found: 7C:2F:80:94:97:5A (1) rssi -59 flags 0x0000
> >=20
> > 02 01 06 0d ff 80 01 02 15 12 34 80 94 97 5a bb ..........4..=
.Z.
> > c5 03 02 0f 18 00 00 00 00 00 00 00 00 00 0e 09 .............=
...
> > 47 69 67 61 73 65 74 20 47 2d 74 61 67 Gigaset G-tag=
> >=20
> > With this fix EIR with merged ADV_DATA and SCAN_RSP in device found=
> > event is properly formatted:
> >=20
> > @ Device Found: 7C:2F:80:94:97:5A (1) rssi -59 flags 0x0000
> >=20
> > 02 01 06 0d ff 80 01 02 15 12 34 80 94 97 5a bb ..........4..=
.Z.
> > c5 03 02 0f 18 0e 09 47 69 67 61 73 65 74 20 47 .......Gigase=
t G
> > 2d 74 61 67 -tag
> >=20
> > Signed-off-by: Szymon Janc <szymon.janc@tieto.com>
> > ---
> > v2: fixed build error due to use of non-upstream BT_ERR_RATELIMITED=
> >=20
> > net/bluetooth/hci_event.c | 17 +++++++++++++++++
> > 1 file changed, 17 insertions(+)
> >=20
> > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> > index 7b61be7..0407324 100644
> > --- a/net/bluetooth/hci_event.c
> > +++ b/net/bluetooth/hci_event.c
> > @@ -4711,6 +4711,23 @@ static void process_adv_report(struct hci_de=
v
> > *hdev, u8 type, bdaddr_t *bdaddr,>=20
> > =09struct hci_conn *conn;
> > =09bool match;
> > =09u32 flags;
> >=20
> > +=09u8 *ptr, real_len;
> > +
> > +=09/* Find the 'real' end of the data in case remote incorrectly
> > +=09 * set significant part length.
>=20
> I do not understand this sentence. I assume what you want to say find=
the
> end of the data in case the report contains padded zero bytes at the =
end
> causing an invalid length value.
Spec is says about significant and non-significant part of advertising =
(where=20
length is length of significant part) but I can rephrase that.
> > +=09 */
> > +=09for (ptr =3D data; ptr < data + len && *ptr; ptr +=3D *ptr + 1)=
{
> > +=09=09if (ptr + 1 + *ptr > data + len)
> > +=09=09=09break;
> > +=09}
>=20
> I am worried about the unchecked usage of *ptr here. That might let y=
ou jump
> into some memory area. How are we protecting this against malicious
> advertising data. And we should have mgnt-tester test cases for malic=
ious
> fields that are not valid data and would make you jump outside of the=
31
> bytes.
OK, I see now that data can be NULL in case of direct advertising repor=
t. I'll=20
add check for that and provide mgmt-tester cases for this and for bogus=
=20
advertising data as well.
> > +
> > +=09real_len =3D ptr - data;
> > +
> > +=09/* Adjust for actual length */
> > +=09if (len !=3D real_len) {
> > +=09=09BT_ERR("Corrected invalid ADV_DATA length=E2=80=9D);
>=20
> I would spell advertising report data length here. There really is no=
> ADV_DATA anywhere in the specification or used in BlueZ like that.
OK. Yet, I still wonder about ratelimit here. With 10 or more G-Tags ar=
ound=20
this can become quite spammy...
--=20
Szymon K. Janc
szymon.janc@gmail.com
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] Bluetooth: Fix reporting incorrect EIR in device found mgmt event
2015-05-20 19:55 ` Szymon Janc
@ 2015-05-25 19:32 ` Marcel Holtmann
0 siblings, 0 replies; 4+ messages in thread
From: Marcel Holtmann @ 2015-05-25 19:32 UTC (permalink / raw)
To: Szymon Janc; +Cc: Szymon Janc, linux-bluetooth
Hi Szymon,
>>> Some remote devices (ie Gigaset G-Tag) misbehave with ADV data length.
>>> This can lead to incorrect EIR format in device found event when
>>> ADV_DATA and SCAN_RSP are merged (terminator field before SCAN_RSP
>>> part).
>>>
>>> Fix this by inspecting ADV_DATA and correct its length if terminator
>>> is found.
>>>
>>>> HCI Event: LE Meta Event (0x3e) plen 42 [hci0] 32.172182
>>>>
>>> LE Advertising Report (0x02)
>>>
>>> Num reports: 1
>>> Event type: Connectable undirected - ADV_IND (0x00)
>>> Address type: Public (0x00)
>>> Address: 7C:2F:80:94:97:5A (Gigaset Communications GmbH)
>>> Data length: 30
>>> Flags: 0x06
>>>
>>> LE General Discoverable Mode
>>> BR/EDR Not Supported
>>>
>>> Company: Gigaset Communications GmbH (384)
>>>
>>> Data: 021512348094975abbc5
>>>
>>> 16-bit Service UUIDs (partial): 1 entry
>>>
>>> Battery Service (0x180f)
>>>
>>> RSSI: -65 dBm (0xbf)
>>>>
>>>> HCI Event: LE Meta Event (0x3e) plen 27 [hci0] 32.172191
>>>>
>>> LE Advertising Report (0x02)
>>>
>>> Num reports: 1
>>> Event type: Scan response - SCAN_RSP (0x04)
>>> Address type: Public (0x00)
>>> Address: 7C:2F:80:94:97:5A (Gigaset Communications GmbH)
>>> Data length: 15
>>> Name (complete): Gigaset G-tag
>>> RSSI: -59 dBm (0xc5)
>>>
>>> Note "Data length: 30" in ADV_DATA which results in 9 extra zero bytes
>>> after Battery Service UUID. Terminator field present in the middle of
>>> EIR in Device Found event resulted in userspace stop parsing EIR and
>>> skipping device name.
>>>
>>> @ Device Found: 7C:2F:80:94:97:5A (1) rssi -59 flags 0x0000
>>>
>>> 02 01 06 0d ff 80 01 02 15 12 34 80 94 97 5a bb ..........4...Z.
>>> c5 03 02 0f 18 00 00 00 00 00 00 00 00 00 0e 09 ................
>>> 47 69 67 61 73 65 74 20 47 2d 74 61 67 Gigaset G-tag
>>>
>>> With this fix EIR with merged ADV_DATA and SCAN_RSP in device found
>>> event is properly formatted:
>>>
>>> @ Device Found: 7C:2F:80:94:97:5A (1) rssi -59 flags 0x0000
>>>
>>> 02 01 06 0d ff 80 01 02 15 12 34 80 94 97 5a bb ..........4...Z.
>>> c5 03 02 0f 18 0e 09 47 69 67 61 73 65 74 20 47 .......Gigaset G
>>> 2d 74 61 67 -tag
>>>
>>> Signed-off-by: Szymon Janc <szymon.janc@tieto.com>
>>> ---
>>> v2: fixed build error due to use of non-upstream BT_ERR_RATELIMITED
>>>
>>> net/bluetooth/hci_event.c | 17 +++++++++++++++++
>>> 1 file changed, 17 insertions(+)
>>>
>>> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
>>> index 7b61be7..0407324 100644
>>> --- a/net/bluetooth/hci_event.c
>>> +++ b/net/bluetooth/hci_event.c
>>> @@ -4711,6 +4711,23 @@ static void process_adv_report(struct hci_dev
>>> *hdev, u8 type, bdaddr_t *bdaddr,>
>>> struct hci_conn *conn;
>>> bool match;
>>> u32 flags;
>>>
>>> + u8 *ptr, real_len;
>>> +
>>> + /* Find the 'real' end of the data in case remote incorrectly
>>> + * set significant part length.
>>
>> I do not understand this sentence. I assume what you want to say find the
>> end of the data in case the report contains padded zero bytes at the end
>> causing an invalid length value.
>
> Spec is says about significant and non-significant part of advertising (where
> length is length of significant part) but I can rephrase that.
>
>>> + */
>>> + for (ptr = data; ptr < data + len && *ptr; ptr += *ptr + 1) {
>>> + if (ptr + 1 + *ptr > data + len)
>>> + break;
>>> + }
>>
>> I am worried about the unchecked usage of *ptr here. That might let you jump
>> into some memory area. How are we protecting this against malicious
>> advertising data. And we should have mgnt-tester test cases for malicious
>> fields that are not valid data and would make you jump outside of the 31
>> bytes.
>
> OK, I see now that data can be NULL in case of direct advertising report. I'll
> add check for that and provide mgmt-tester cases for this and for bogus
> advertising data as well.
I am missing an updated patch for this.
Regards
Marcel
^ permalink raw reply [flat|nested] 4+ messages in thread
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2015-05-14 10:48 [PATCH v2] Bluetooth: Fix reporting incorrect EIR in device found mgmt event Szymon Janc
2015-05-19 19:17 ` Marcel Holtmann
2015-05-20 19:55 ` Szymon Janc
2015-05-25 19:32 ` Marcel Holtmann
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