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Bluetooth: Add more enc key size check 

CVE: CVE-2023-24023

JIRA: https://issues.redhat.com/browse/RHEL-19668

commit 04a342cc49a8522e99c9b3346371c329d841dcd2
Author: Alex Lu <alex_lu@realsil.com.cn>
Date:   Tue Dec 12 10:30:34 2023 +0800

    Bluetooth: Add more enc key size check

    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>

Signed-off-by: Bastien Nocera <bnocera@redhat.com>
This commit is contained in:
Bastien Nocera 2024-02-08 10:15:15 +01:00
parent dbc78051c6
commit 37098d552c
1 changed files with 15 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
net/bluetooth/hci_event.c
View File

@ -747,9 +747,23 @@ 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) {
/* 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);