From: Alex Lu alex_lu@realsil.com.cn
[ Upstream commit 04a342cc49a8522e99c9b3346371c329d841dcd2 ]
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@vger.kernel.org Signed-off-by: Alex Lu alex_lu@realsil.com.cn Signed-off-by: Max Chou max.chou@realtek.com Signed-off-by: Luiz Augusto von Dentz luiz.von.dentz@intel.com [ Nazar Kalashnikov: change status to rp_status due to function parameter conflict ] Signed-off-by: Nazar Kalashnikov sivartiwe@gmail.com --- Backport fix for CVE-2023-24023 net/bluetooth/hci_event.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c index c6dbb4aebfbc..6310f4f9890e 100644 --- a/net/bluetooth/hci_event.c +++ b/net/bluetooth/hci_event.c @@ -3043,6 +3043,7 @@ static void read_enc_key_size_complete(struct hci_dev *hdev, u8 status, const struct hci_rp_read_enc_key_size *rp; struct hci_conn *conn; u16 handle; + u8 rp_status;
BT_DBG("%s status 0x%02x", hdev->name, status);
@@ -3052,6 +3053,7 @@ static void read_enc_key_size_complete(struct hci_dev *hdev, u8 status, }
rp = (void *)skb->data; + rp_status = rp->status; handle = le16_to_cpu(rp->handle);
hci_dev_lock(hdev); @@ -3064,15 +3066,30 @@ static void read_enc_key_size_complete(struct hci_dev *hdev, u8 status, * secure approach is to then assume the key size is 0 to force a * disconnection. */ - if (rp->status) { + if (rp_status) { bt_dev_err(hdev, "failed to read key size for handle %u", handle); conn->enc_key_size = 0; } else { conn->enc_key_size = rp->key_size; + rp_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. + */ + rp_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, rp_status);
unlock: hci_dev_unlock(hdev);