netdev - Re: [PATCH v1] Bluetooth: Enforce key size of 16 bytes on FIPS level

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Message-Id: <4819769E-04AD-42A7-BC2C-9C628EEDE3F3@holtmann.org>
Date:   Fri, 25 Sep 2020 18:25:48 +0200
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Archie Pusaka <apusaka@...gle.com>
Cc:     linux-bluetooth <linux-bluetooth@...r.kernel.org>,
        CrosBT Upstreaming <chromeos-bluetooth-upstreaming@...omium.org>,
        Archie Pusaka <apusaka@...omium.org>,
        Alain Michaud <alainm@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v1] Bluetooth: Enforce key size of 16 bytes on FIPS level

Hi Archie,

> According to the spec Ver 5.2, Vol 3, Part C, Sec 5.2.2.8:
> Device in security mode 4 level 4 shall enforce:
> 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)
> 
> This patch rejects connection with key size below 16 for FIPS level
> services.
> 
> Signed-off-by: Archie Pusaka <apusaka@...omium.org>
> Reviewed-by: Alain Michaud <alainm@...omium.org>
> 
> ---
> 
> net/bluetooth/l2cap_core.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> index ade83e224567..306616ec26e6 100644
> --- a/net/bluetooth/l2cap_core.c
> +++ b/net/bluetooth/l2cap_core.c
> @@ -1515,8 +1515,13 @@ static bool l2cap_check_enc_key_size(struct hci_conn *hcon)
> 	 * that have no key size requirements. Ensure that the link is
> 	 * actually encrypted before enforcing a key size.
> 	 */
> +	int min_key_size = hcon->hdev->min_enc_key_size;
> +
> +	if (hcon->sec_level == BT_SECURITY_FIPS)
> +		min_key_size = 16;
> +
> 	return (!test_bit(HCI_CONN_ENCRYPT, &hcon->flags) ||
> -		hcon->enc_key_size >= hcon->hdev->min_enc_key_size);
> +		hcon->enc_key_size >= min_key_size);
> }

I think this is fine at this position. It is a L2CAP socket requirement to be in FIPS mode since you will set it via socket option. However I would extend the comment above to describe what is going on. And generally the variable declaration might be better placed before the comment.

Regards

Marcel