linux-kernel - Re: [PATCH 1/2] nvme-auth: use transformed key size to create resp

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Date:   Mon, 16 Oct 2023 08:54:57 +0000
From:   Mark O'Donovan <shiftee@...teo.net>
To:     Hannes Reinecke <hare@...e.de>, linux-kernel@...r.kernel.org
Cc:     linux-nvme@...ts.infradead.org, sagi@...mberg.me, hch@....de,
        axboe@...nel.dk, kbusch@...nel.org,
        Akash Appaiah <Akash.Appaiah@...l.com>
Subject: Re: [PATCH 1/2] nvme-auth: use transformed key size to create resp

On 14/10/2023 12:41, Hannes Reinecke wrote:
> On 10/13/23 22:28, Mark O'Donovan wrote:
>> This does not change current behaviour as the driver currently
>> verifies that the secret size is the same size as the length of
>> the transformation hash.
>>
>> Co-developed-by: Akash Appaiah <Akash.Appaiah@...l.com>
>> Signed-off-by: Akash Appaiah <Akash.Appaiah@...l.com>
>> Signed-off-by: Mark O'Donovan <shiftee@...teo.net>
>> ---
>>   drivers/nvme/host/auth.c | 11 ++++++++++-
>>   1 file changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/nvme/host/auth.c b/drivers/nvme/host/auth.c
>> index daf5d144a8ea..e7d478d17b06 100644
>> --- a/drivers/nvme/host/auth.c
>> +++ b/drivers/nvme/host/auth.c
>> @@ -418,6 +418,14 @@ static int nvme_auth_set_dhchap_failure2_data(struct nvme_ctrl *ctrl,
>>       return size;
>>   }
>> +static int nvme_auth_dhchap_transformed_key_len(struct nvme_dhchap_key *key)
>> +{
>> +    if (key->hash)
>> +        return nvme_auth_hmac_hash_len(key->hash);
>> +
>> +    return key->len;
>> +}
>> +
>>   static int nvme_auth_dhchap_setup_host_response(struct nvme_ctrl *ctrl,
>>           struct nvme_dhchap_queue_context *chap)
>>   {
>> @@ -442,7 +450,8 @@ static int nvme_auth_dhchap_setup_host_response(struct nvme_ctrl *ctrl,
>>       }
>>       ret = crypto_shash_setkey(chap->shash_tfm,
>> -            chap->host_response, ctrl->host_key->len);
>> +            chap->host_response,
>> +            nvme_auth_dhchap_transformed_key_len(ctrl->host_key));
>>       if (ret) {
>>           dev_warn(ctrl->device, "qid %d: failed to set key, error %d\n",
>>                chap->qid, ret);
> 
> Hmm. Yeah, hash size vs secret size always gets me.
> However, wouldn't it be better to return the key size from
> nvme_auth_transform_key and us that directly?
> (cf the attached patch)
> 
> Cheers,
> 
> Hannes

Hi Hannes,

I gave this a try and it ended up being easier to put it in struct nvme_dhchap_key.
V2 also does the nvme target code, and this means the length is stored in the same place.
Let me know if this works for you.

Thanks,
Mark