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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Thu, 18 Jun 2020 10:37:20 -0700
Message-ID: <CABBYNZKBcpV4CNhLKkzApnEq0FWX+wbY7o4P-6sWr85j9qWhMg@mail.gmail.com>
Subject: Re: [PATCH v2 1/2] Bluetooth: Disconnect if E0 is used for Level 4
To:     "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
Cc:     Marcel Holtmann <marcel@holtmann.org>
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Sender: linux-bluetooth-owner@vger.kernel.org
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Hi Marcel,

On Wed, May 20, 2020 at 2:20 PM Luiz Augusto von Dentz
<luiz.dentz@gmail.com> wrote:
>
> From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
>
> E0 is not allowed with Level 4:
>
> BLUETOOTH CORE SPECIFICATION Version 5.2 | Vol 3, Part C page 1319:
>
>   '128-bit equivalent strength for link and encryption keys
>    required using FIPS approved algorithms (E0 not allowed,
>    SAFER+ not allowed, and P-192 not allowed; encryption key
>    not shortened'
>
> SC enabled:
>
> > HCI Event: Read Remote Extended Features (0x23) plen 13
>         Status: Success (0x00)
>         Handle: 256
>         Page: 1/2
>         Features: 0x0b 0x00 0x00 0x00 0x00 0x00 0x00 0x00
>           Secure Simple Pairing (Host Support)
>           LE Supported (Host)
>           Secure Connections (Host Support)
> > HCI Event: Encryption Change (0x08) plen 4
>         Status: Success (0x00)
>         Handle: 256
>         Encryption: Enabled with AES-CCM (0x02)
>
> SC disabled:
>
> > HCI Event: Read Remote Extended Features (0x23) plen 13
>         Status: Success (0x00)
>         Handle: 256
>         Page: 1/2
>         Features: 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00
>           Secure Simple Pairing (Host Support)
>           LE Supported (Host)
> > HCI Event: Encryption Change (0x08) plen 4
>         Status: Success (0x00)
>         Handle: 256
>         Encryption: Enabled with E0 (0x01)
> [May 8 20:23] Bluetooth: hci0: Invalid security: expect AES but E0 was used
> < HCI Command: Disconnect (0x01|0x0006) plen 3
>         Handle: 256
>         Reason: Authentication Failure (0x05)
>
> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> ---
>  include/net/bluetooth/hci_core.h | 10 ++++++----
>  net/bluetooth/hci_conn.c         | 17 +++++++++++++++++
>  net/bluetooth/hci_event.c        | 20 ++++++++------------
>  3 files changed, 31 insertions(+), 16 deletions(-)
>
> diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
> index cdd4f1db8670..c69309ffd40a 100644
> --- a/include/net/bluetooth/hci_core.h
> +++ b/include/net/bluetooth/hci_core.h
> @@ -1402,11 +1402,13 @@ static inline void hci_encrypt_cfm(struct hci_conn *conn, __u8 status)
>         else
>                 encrypt = 0x01;
>
> -       if (conn->sec_level == BT_SECURITY_SDP)
> -               conn->sec_level = BT_SECURITY_LOW;
> +       if (!status) {
> +               if (conn->sec_level == BT_SECURITY_SDP)
> +                       conn->sec_level = BT_SECURITY_LOW;
>
> -       if (conn->pending_sec_level > conn->sec_level)
> -               conn->sec_level = conn->pending_sec_level;
> +               if (conn->pending_sec_level > conn->sec_level)
> +                       conn->sec_level = conn->pending_sec_level;
> +       }
>
>         mutex_lock(&hci_cb_list_lock);
>         list_for_each_entry(cb, &hci_cb_list, list) {
> diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> index 307800fd18e6..b99b5c6de55a 100644
> --- a/net/bluetooth/hci_conn.c
> +++ b/net/bluetooth/hci_conn.c
> @@ -1323,6 +1323,23 @@ int hci_conn_check_link_mode(struct hci_conn *conn)
>                         return 0;
>         }
>
> +        /* AES encryption is required for Level 4:
> +         *
> +         * BLUETOOTH CORE SPECIFICATION Version 5.2 | Vol 3, Part C
> +         * page 1319:
> +         *
> +         * 128-bit equivalent strength for link and encryption keys
> +         * required using FIPS approved algorithms (E0 not allowed,
> +         * SAFER+ not allowed, and P-192 not allowed; encryption key
> +         * not shortened)
> +         */
> +       if (conn->sec_level == BT_SECURITY_FIPS &&
> +           !test_bit(HCI_CONN_AES_CCM, &conn->flags)) {
> +               bt_dev_err(conn->hdev,
> +                          "Invalid security: Missing AES-CCM usage");
> +               return 0;
> +       }
> +
>         if (hci_conn_ssp_enabled(conn) &&
>             !test_bit(HCI_CONN_ENCRYPT, &conn->flags))
>                 return 0;
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index cfeaee347db3..d6a1e2450696 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -3065,27 +3065,23 @@ static void hci_encrypt_change_evt(struct hci_dev *hdev, struct sk_buff *skb)
>
>         clear_bit(HCI_CONN_ENCRYPT_PEND, &conn->flags);
>
> +       /* Check link security requirements are met */
> +       if (!hci_conn_check_link_mode(conn))
> +               ev->status = HCI_ERROR_AUTH_FAILURE;
> +
>         if (ev->status && conn->state == BT_CONNECTED) {
>                 if (ev->status == HCI_ERROR_PIN_OR_KEY_MISSING)
>                         set_bit(HCI_CONN_AUTH_FAILURE, &conn->flags);
>
> +               /* Notify upper layers so they can cleanup before
> +                * disconnecting.
> +                */
> +               hci_encrypt_cfm(conn, ev->status);
>                 hci_disconnect(conn, HCI_ERROR_AUTH_FAILURE);
>                 hci_conn_drop(conn);
>                 goto unlock;
>         }
>
> -       /* In Secure Connections Only mode, do not allow any connections
> -        * that are not encrypted with AES-CCM using a P-256 authenticated
> -        * combination key.
> -        */
> -       if (hci_dev_test_flag(hdev, HCI_SC_ONLY) &&
> -           (!test_bit(HCI_CONN_AES_CCM, &conn->flags) ||
> -            conn->key_type != HCI_LK_AUTH_COMBINATION_P256)) {
> -               hci_connect_cfm(conn, HCI_ERROR_AUTH_FAILURE);
> -               hci_conn_drop(conn);
> -               goto unlock;
> -       }
> -
>         /* Try reading the encryption key size for encrypted ACL links */
>         if (!ev->status && ev->encrypt && conn->type == ACL_LINK) {
>                 struct hci_cp_read_enc_key_size cp;
> --
> 2.25.3

Looks like we had left this behind.

-- 
Luiz Augusto von Dentz