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Subject: Re: [PATCH 1/2] Bluetooth: Add support for reading security
 information
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <CALWDO_X-cN4pba3BiSKD7BP5KokaTcDefgyTZeXv0hbxz+LECA@mail.gmail.com>
Date:   Fri, 3 Apr 2020 19:00:18 +0200
Cc:     BlueZ <linux-bluetooth@vger.kernel.org>
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Message-Id: <1D4E9B3D-5BB6-4153-9982-B16E5E588C06@holtmann.org>
References: <20200402132956.642267-1-marcel@holtmann.org>
 <CALWDO_X-cN4pba3BiSKD7BP5KokaTcDefgyTZeXv0hbxz+LECA@mail.gmail.com>
To:     Alain Michaud <alainmichaud@google.com>
Sender: linux-bluetooth-owner@vger.kernel.org
Precedence: bulk

Hi Alain,

>> To allow userspace to make correcty security policy decision, the kernel
>> needs to export a few details of the supported security features and
>> encryption key size information. This command exports this information
>> and also allows future extensions if needed.
>> 
>> Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
>> ---
>> include/net/bluetooth/mgmt.h |  7 +++++
>> net/bluetooth/mgmt.c         | 53 ++++++++++++++++++++++++++++++++++++
>> 2 files changed, 60 insertions(+)
>> 
>> diff --git a/include/net/bluetooth/mgmt.h b/include/net/bluetooth/mgmt.h
>> index f41cd87550dc..65dd6fd1fff3 100644
>> --- a/include/net/bluetooth/mgmt.h
>> +++ b/include/net/bluetooth/mgmt.h
>> @@ -674,6 +674,13 @@ struct mgmt_cp_set_blocked_keys {
>> 
>> #define MGMT_OP_SET_WIDEBAND_SPEECH    0x0047
>> 
>> +#define MGMT_OP_READ_SECURITY_INFO     0x0048
>> +#define MGMT_READ_SECURITY_INFO_SIZE   0
>> +struct mgmt_rp_read_security_info {
>> +       __le16   sec_len;
>> +       __u8     sec[0];
>> +} __packed;
>> +
>> #define MGMT_EV_CMD_COMPLETE           0x0001
>> struct mgmt_ev_cmd_complete {
>>        __le16  opcode;
>> diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
>> index 6552003a170e..7b9eac339c87 100644
>> --- a/net/bluetooth/mgmt.c
>> +++ b/net/bluetooth/mgmt.c
>> @@ -108,6 +108,7 @@ static const u16 mgmt_commands[] = {
>>        MGMT_OP_SET_APPEARANCE,
>>        MGMT_OP_SET_BLOCKED_KEYS,
>>        MGMT_OP_SET_WIDEBAND_SPEECH,
>> +       MGMT_OP_READ_SECURITY_INFO,
>> };
>> 
>> static const u16 mgmt_events[] = {
>> @@ -155,6 +156,7 @@ static const u16 mgmt_untrusted_commands[] = {
>>        MGMT_OP_READ_CONFIG_INFO,
>>        MGMT_OP_READ_EXT_INDEX_LIST,
>>        MGMT_OP_READ_EXT_INFO,
>> +       MGMT_OP_READ_SECURITY_INFO,
>> };
>> 
>> static const u16 mgmt_untrusted_events[] = {
>> @@ -3659,6 +3661,55 @@ static int set_wideband_speech(struct sock *sk, struct hci_dev *hdev,
>>        return err;
>> }
>> 
>> +static int read_security_info(struct sock *sk, struct hci_dev *hdev,
>> +                             void *data, u16 data_len)
>> +{
>> +       char buf[16];
>> +       struct mgmt_rp_read_security_info *rp = (void *)buf;
>> +       u16 sec_len = 0;
>> +       u8 flags = 0;
>> +
>> +       bt_dev_dbg(hdev, "sock %p", sk);
>> +
>> +       memset(&buf, 0, sizeof(buf));
>> +
>> +       hci_dev_lock(hdev);
>> +
>> +       /* When the Read Simple Pairing Options command is supported, then
>> +        * the remote public key validation is supported.
>> +        */
>> +       if (hdev->commands[41] & 0x08)
>> +               flags |= 0x01;  /* Remote public key validation (BR/EDR) */
>> +
>> +       flags |= 0x02;          /* Remote public key validation (LE) */
>> +
>> +       /* When the Read Encryption Key Size command is supported, then the
>> +        * encryption key size is enforced.
>> +        */
>> +       if (hdev->commands[20] & 0x10)
>> +               flags |= 0x04;  /* Encryption key size enforcement (BR/EDR) */
>> +
>> +       flags |= 0x08;          /* Encryption key size enforcement (LE) */
>> +
>> +       sec_len = eir_append_data(rp->sec, sec_len, 0x01, &flags, 1);
>> +
>> +       /* When the Read Simple Pairing Options command is supported, then
>> +        * also max encryption key size information is provided.
>> +        */
>> +       if (hdev->commands[41] & 0x08)
>> +               sec_len = eir_append_le16(rp->sec, sec_len, 0x02,
>> +                                         hdev->max_enc_key_size);
>> +
>> +       sec_len = eir_append_le16(rp->sec, sec_len, 0x03, SMP_MAX_ENC_KEY_SIZE);
>> +
>> +       rp->sec_len = cpu_to_le16(sec_len);
>> +
>> +       hci_dev_unlock(hdev);
>> +
>> +       return mgmt_cmd_complete(sk, hdev->id, MGMT_OP_READ_SECURITY_INFO, 0,
>> +                                rp, sizeof(*rp) + sec_len);
>> +}
>> +
>> static void read_local_oob_data_complete(struct hci_dev *hdev, u8 status,
>>                                         u16 opcode, struct sk_buff *skb)
>> {
>> @@ -7099,6 +7150,8 @@ static const struct hci_mgmt_handler mgmt_handlers[] = {
>>        { set_blocked_keys,        MGMT_OP_SET_BLOCKED_KEYS_SIZE,
>>                                                HCI_MGMT_VAR_LEN },
>>        { set_wideband_speech,     MGMT_SETTING_SIZE },
>> +       { read_security_info,      MGMT_READ_SECURITY_INFO_SIZE,
>> +                                               HCI_MGMT_UNTRUSTED },
>> };
>> 
>> void mgmt_index_added(struct hci_dev *hdev)
>> --
>> 2.25.1
>> 
> LGTM.

Can I treat these as Reviewed-by: Alain Michaud <alainmichaud@google.com> ?

Regards

Marcel