linux-kernel - Re: [PATCH 2/2] crypto: caam - support tagged keys for skcipher algorithms

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Date:   Thu, 16 Jul 2020 13:35:51 +0300
From:   Horia Geantă <horia.geanta@....com>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        Iuliana Prodan <iuliana.prodan@....com>
Cc:     Aymen Sghaier <aymen.sghaier@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Silvano Di Ninno <silvano.dininno@....com>,
        Franck Lenormand <franck.lenormand@....com>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH 2/2] crypto: caam - support tagged keys for skcipher
 algorithms

On 7/16/2020 10:36 AM, Herbert Xu wrote:
> On Mon, Jul 13, 2020 at 01:05:36AM +0300, Iuliana Prodan wrote:
>> Tagged keys are keys that contain metadata indicating what
>> they are and how to handle them using tag_object API.
>>
>> Add support, for tagged keys, to skcipher algorithms by
>> adding new transformations, with _tk_ prefix to distinguish
>> between plaintext and tagged keys.
>>
>> For job descriptors a new option (key_cmd_opt) was added for KEY command.
>> Tagged keys can be loaded using only a KEY command with ENC=1
>> and the proper setting of the EKT bit. The EKT bit in the
>> KEY command indicates which encryption algorithm (AES-ECB or
>> AES-CCM) should be used to decrypt the key. These options will be kept in
>> key_cmd_opt.
>>
>> The tk_ transformations can be used directly by their name:
>> struct sockaddr_alg sa = {
>>     .salg_family = AF_ALG,
>>     .salg_type = "skcipher", /* this selects the symmetric cipher */
>>     .salg_name = "tk(cbc(aes))" /* this is the cipher name */
>> };
>> or for dm-crypt, e.g. using dmsetup:
>> dmsetup -v create encrypted --table "0 $(blockdev --getsz /dev/mmcblk2p10)
>> crypt capi:tk(cbc(aes))-plain :32:logon:seckey 0 /dev/mmcblk2p10 0 1
>> sector_size:512".
>>
>> Signed-off-by: Franck LENORMAND <franck.lenormand@....com>
>> Signed-off-by: Iuliana Prodan <iuliana.prodan@....com>
> 
> Can this use the existing paes name instead of tk as done in
> other drivers?
> 
This patch set adds support only for some AES-based algorithms.
However, going further the plan is to add all keyed algorithms
supported by caam.

Thus I wouldn't tie the name to AES.

Possible alternatives would be:
pk - protected keys
tk - with "t" standing for "trusted" instead of "tagged"

Wrt. "trusted", I am not sure this term should strictly be tied
to a TPM or not.

Thanks,
Horia