From: Alex Lu <[email protected]>
When we are slave role and receives l2cap conn req when encryption has
started, we should check the enc key size to avoid KNOB attack or BLUFFS
attack.
From SIG recommendation, implementations are advised to reject
service-level connections on an encrypted baseband link with key
strengths below 7 octets.
The btmon log below shows the case that lacks enc key size check.
> HCI Event: Connect Request (0x04) plen 10
Address: BB:22:33:44:55:99 (OUI BB-22-33)
Class: 0x480104
Major class: Computer (desktop, notebook, PDA, organizers)
Minor class: Desktop workstation
Capturing (Scanner, Microphone)
Telephony (Cordless telephony, Modem, Headset)
Link type: ACL (0x01)
< HCI Command: Accept Connection Request (0x01|0x0009) plen 7
Address: BB:22:33:44:55:99 (OUI BB-22-33)
Role: Peripheral (0x01)
> HCI Event: Command Status (0x0f) plen 4
Accept Connection Request (0x01|0x0009) ncmd 2
Status: Success (0x00)
> HCI Event: Connect Complete (0x03) plen 11
Status: Success (0x00)
Handle: 1
Address: BB:22:33:44:55:99 (OUI BB-22-33)
Link type: ACL (0x01)
Encryption: Disabled (0x00)
...
> HCI Event: Encryption Change (0x08) plen 4
Status: Success (0x00)
Handle: 1 Address: BB:22:33:44:55:99 (OUI BB-22-33)
Encryption: Enabled with E0 (0x01)
< HCI Command: Read Encryption Key Size (0x05|0x0008) plen 2
Handle: 1 Address: BB:22:33:44:55:99 (OUI BB-22-33)
> HCI Event: Command Complete (0x0e) plen 7
Read Encryption Key Size (0x05|0x0008) ncmd 2
Status: Success (0x00)
Handle: 1 Address: BB:22:33:44:55:99 (OUI BB-22-33)
Key size: 6
...
// We should check the enc key size
> ACL Data RX: Handle 1 flags 0x02 dlen 12
L2CAP: Connection Request (0x02) ident 3 len 4
PSM: 25 (0x0019)
Source CID: 64
< ACL Data TX: Handle 1 flags 0x00 dlen 16
L2CAP: Connection Response (0x03) ident 3 len 8
Destination CID: 64
Source CID: 64
Result: Connection pending (0x0001)
Status: Authorization pending (0x0002)
> HCI Event: Number of Completed Packets (0x13) plen 5
Num handles: 1
Handle: 1 Address: BB:22:33:44:55:99 (OUI BB-22-33)
Count: 1
#35: len 16 (25 Kb/s)
Latency: 5 msec (2-7 msec ~4 msec)
< ACL Data TX: Handle 1 flags 0x00 dlen 16
L2CAP: Connection Response (0x03) ident 3 len 8
Destination CID: 64
Source CID: 64
Result: Connection successful (0x0000)
Status: No further information available (0x0000)
Signed-off-by: Alex Lu <[email protected]>
Signed-off-by: Max Chou <[email protected]>
---
Changes in v2:
- Fix compiling issue reported by sparse
net/bluetooth/l2cap_core.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 17ca13e8c044..a9809fbe6b00 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -1669,7 +1669,13 @@ static void l2cap_conn_start(struct l2cap_conn *conn)
rsp.dcid = cpu_to_le16(chan->scid);
if (l2cap_chan_check_security(chan, false)) {
- if (test_bit(FLAG_DEFER_SETUP, &chan->flags)) {
+ if (!l2cap_check_enc_key_size(conn->hcon)) {
+ l2cap_state_change(chan, BT_DISCONN);
+ __set_chan_timer(chan,
+ L2CAP_DISC_TIMEOUT);
+ rsp.result = cpu_to_le16(L2CAP_CR_SEC_BLOCK);
+ rsp.status = cpu_to_le16(L2CAP_CS_NO_INFO);
+ } else if (test_bit(FLAG_DEFER_SETUP, &chan->flags)) {
rsp.result = cpu_to_le16(L2CAP_CR_PEND);
rsp.status = cpu_to_le16(L2CAP_CS_AUTHOR_PEND);
chan->ops->defer(chan);
@@ -4202,7 +4208,15 @@ static struct l2cap_chan *l2cap_connect(struct l2cap_conn *conn,
if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_DONE) {
if (l2cap_chan_check_security(chan, false)) {
- if (test_bit(FLAG_DEFER_SETUP, &chan->flags)) {
+ /* As slave role, we should check the enc key size when
+ * l2cap conn req is received.
+ */
+ if (!l2cap_check_enc_key_size(conn->hcon)) {
+ l2cap_state_change(chan, BT_DISCONN);
+ __set_chan_timer(chan, L2CAP_DISC_TIMEOUT);
+ result = L2CAP_CR_SEC_BLOCK;
+ status = L2CAP_CS_NO_INFO;
+ } else if (test_bit(FLAG_DEFER_SETUP, &chan->flags)) {
l2cap_state_change(chan, BT_CONNECT2);
result = L2CAP_CR_PEND;
status = L2CAP_CS_AUTHOR_PEND;
--
2.39.2
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=808718
---Test result---
Test Summary:
CheckPatch PASS 0.48 seconds
GitLint PASS 0.21 seconds
SubjectPrefix PASS 0.07 seconds
BuildKernel PASS 27.52 seconds
CheckAllWarning PASS 30.74 seconds
CheckSparse PASS 36.91 seconds
CheckSmatch PASS 99.35 seconds
BuildKernel32 PASS 27.19 seconds
TestRunnerSetup PASS 430.58 seconds
TestRunner_l2cap-tester PASS 24.23 seconds
TestRunner_iso-tester PASS 45.04 seconds
TestRunner_bnep-tester PASS 7.09 seconds
TestRunner_mgmt-tester PASS 160.98 seconds
TestRunner_rfcomm-tester PASS 11.03 seconds
TestRunner_sco-tester PASS 14.59 seconds
TestRunner_ioctl-tester PASS 12.19 seconds
TestRunner_mesh-tester PASS 8.72 seconds
TestRunner_smp-tester PASS 9.77 seconds
TestRunner_userchan-tester PASS 7.32 seconds
IncrementalBuild PASS 25.72 seconds
---
Regards,
Linux Bluetooth
Hi Alex,
On Mon, Dec 11, 2023 at 4:57 AM <[email protected]> wrote:
>
> 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=808718
>
> ---Test result---
>
> Test Summary:
> CheckPatch PASS 0.48 seconds
> GitLint PASS 0.21 seconds
> SubjectPrefix PASS 0.07 seconds
> BuildKernel PASS 27.52 seconds
> CheckAllWarning PASS 30.74 seconds
> CheckSparse PASS 36.91 seconds
> CheckSmatch PASS 99.35 seconds
> BuildKernel32 PASS 27.19 seconds
> TestRunnerSetup PASS 430.58 seconds
> TestRunner_l2cap-tester PASS 24.23 seconds
> TestRunner_iso-tester PASS 45.04 seconds
> TestRunner_bnep-tester PASS 7.09 seconds
> TestRunner_mgmt-tester PASS 160.98 seconds
> TestRunner_rfcomm-tester PASS 11.03 seconds
> TestRunner_sco-tester PASS 14.59 seconds
> TestRunner_ioctl-tester PASS 12.19 seconds
> TestRunner_mesh-tester PASS 8.72 seconds
> TestRunner_smp-tester PASS 9.77 seconds
> TestRunner_userchan-tester PASS 7.32 seconds
> IncrementalBuild PASS 25.72 seconds
>
How about doing the following:
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 2ad7b9f86f74..f9a8fb9fcce2 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -750,9 +750,12 @@ static u8 hci_cc_read_enc_key_size(struct hci_dev
*hdev, void *data,
} else {
conn->enc_key_size = rp->key_size;
status = 0;
+
+ if (conn->enc_key_size < hdev->min_enc_key_size)
+ status = HCI_ERROR_AUTH_FAILURE;
}
- hci_encrypt_cfm(conn, 0);
+ hci_encrypt_cfm(conn, status);
done:
hci_dev_unlock(hdev);
That way we don't have to proliferate the checks over to L2CAP, etc,
so we consider that the encryption itself fails if the
conn->enc_key_size < hdev->min_enc_key_size.
>
> ---
> Regards,
> Linux Bluetooth
>
--
Luiz Augusto von Dentz