This is a note to let you know that I've just added the patch titled
Bluetooth: Add more enc key size check
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bluetooth-add-more-enc-key-size-check.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 04a342cc49a8522e99c9b3346371c329d841dcd2 Mon Sep 17 00:00:00 2001
From: Alex Lu <alex_lu@xxxxxxxxxxxxxx>
Date: Tue, 12 Dec 2023 10:30:34 +0800
Subject: Bluetooth: Add more enc key size check
From: Alex Lu <alex_lu@xxxxxxxxxxxxxx>
commit 04a342cc49a8522e99c9b3346371c329d841dcd2 upstream.
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.
A simple and clear way to achieve this is to place the enc key size
check in hci_cc_read_enc_key_size()
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)
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Alex Lu <alex_lu@xxxxxxxxxxxxxx>
Signed-off-by: Max Chou <max.chou@xxxxxxxxxxx>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/bluetooth/hci_event.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -750,9 +750,23 @@ static u8 hci_cc_read_enc_key_size(struc
} else {
conn->enc_key_size = rp->key_size;
status = 0;
+
+ if (conn->enc_key_size < hdev->min_enc_key_size) {
+ /* As slave role, the conn->state has been set to
+ * BT_CONNECTED and l2cap conn req might not be received
+ * yet, at this moment the l2cap layer almost does
+ * nothing with the non-zero status.
+ * So we also clear encrypt related bits, and then the
+ * handler of l2cap conn req will get the right secure
+ * state at a later time.
+ */
+ status = HCI_ERROR_AUTH_FAILURE;
+ clear_bit(HCI_CONN_ENCRYPT, &conn->flags);
+ clear_bit(HCI_CONN_AES_CCM, &conn->flags);
+ }
}
- hci_encrypt_cfm(conn, 0);
+ hci_encrypt_cfm(conn, status);
done:
hci_dev_unlock(hdev);
Patches currently in stable-queue which might be from alex_lu@xxxxxxxxxxxxxx are
queue-6.6/bluetooth-add-more-enc-key-size-check.patch
