This change is used to relieve CVE-2020-26555. The description of the
CVE:
Bluetooth legacy BR/EDR PIN code pairing in Bluetooth Core Specification
1.0B through 5.2 may permit an unauthenticated nearby device to spoof
the BD_ADDR of the peer device to complete pairing without knowledge
of the PIN. [1]
The detail of this attack is in IEEE paper:
BlueMirror: Reflections on Bluetooth Pairing and Provisioning Protocols
[2]
It's a reflection attack. The paper mentioned that attacker can induce
the attacked target to generate null link key (zero key) without PIN
code. In BR/EDR, the key generation is actually handled in the controller
which is below HCI.
Thus, we can ignore null link key in the handler of "Link Key Notification
event" to relieve the attack. A similar implementation also shows in
btstack project. [3]
v3: Drop the connection when null link key be detected.
v2:
- Used Link: tag instead of Closes:
- Used bt_dev_dbg instead of BT_DBG
- Added Fixes: tag
Fixes: 55ed8ca10f35 ("Bluetooth: Implement link key handling for the management interface")
Link: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-26555 [1]
Link: https://ieeexplore.ieee.org/abstract/document/9474325/authors#authors [2]
Link: https://github.com/bluekitchen/btstack/blob/master/src/hci.c#L3722 [3]
Signed-off-by: Lee, Chun-Yi <[email protected]>
---
net/bluetooth/hci_event.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 95816a938cea..a20a94e85b1a 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4692,6 +4692,14 @@ static void hci_link_key_notify_evt(struct hci_dev *hdev, void *data,
if (!conn)
goto unlock;
+ /* Ignore NULL link key against CVE-2020-26555 */
+ if (!memcmp(ev->link_key, ZERO_KEY, HCI_LINK_KEY_SIZE)) {
+ bt_dev_dbg(hdev, "Ignore NULL link key (ZERO KEY) for %pMR", &ev->bdaddr);
+ hci_disconnect(conn, HCI_ERROR_AUTH_FAILURE);
+ hci_conn_drop(conn);
+ goto unlock;
+ }
+
hci_conn_hold(conn);
conn->disc_timeout = HCI_DISCONN_TIMEOUT;
hci_conn_drop(conn);
--
2.35.3
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=789096
---Test result---
Test Summary:
CheckPatch PASS 0.77 seconds
GitLint PASS 0.32 seconds
SubjectPrefix PASS 0.10 seconds
BuildKernel PASS 43.13 seconds
CheckAllWarning PASS 46.91 seconds
CheckSparse WARNING 53.60 seconds
CheckSmatch WARNING 140.37 seconds
BuildKernel32 PASS 41.66 seconds
TestRunnerSetup PASS 622.54 seconds
TestRunner_l2cap-tester PASS 38.78 seconds
TestRunner_iso-tester PASS 82.16 seconds
TestRunner_bnep-tester PASS 13.74 seconds
TestRunner_mgmt-tester FAIL 251.73 seconds
TestRunner_rfcomm-tester PASS 21.30 seconds
TestRunner_sco-tester PASS 24.23 seconds
TestRunner_ioctl-tester PASS 23.16 seconds
TestRunner_mesh-tester PASS 16.89 seconds
TestRunner_smp-tester PASS 20.09 seconds
TestRunner_userchan-tester PASS 15.21 seconds
IncrementalBuild PASS 40.23 seconds
Details
##############################
Test: CheckSparse - WARNING
Desc: Run sparse tool with linux kernel
Output:
net/bluetooth/hci_event.c: note: in included file (through include/net/bluetooth/hci_core.h):
##############################
Test: CheckSmatch - WARNING
Desc: Run smatch tool with source
Output:
net/bluetooth/hci_event.c: note: in included file (through include/net/bluetooth/hci_core.h):
##############################
Test: TestRunner_mgmt-tester - FAIL
Desc: Run mgmt-tester with test-runner
Output:
Total: 497, Passed: 496 (99.8%), Failed: 1, Not Run: 0
Failed Test Cases
LL Privacy - Unpair 1 Timed out 2.016 seconds
---
Regards,
Linux Bluetooth