Re: [PATCH] crypto: ccp/gcm - use const time tag comparison.

[Gary R Hook]

On 7/1/19 7:25 PM, Eric Biggers wrote:
> On Mon, Jul 01, 2019 at 05:01:32PM -0700, Cfir Cohen wrote:
>> Avoid leaking GCM tag through timing side channel.
>>
>> Signed-off-by: Cfir Cohen <cfir@xxxxxxxxxx>
>> ---
>>   drivers/crypto/ccp/ccp-ops.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/crypto/ccp/ccp-ops.c b/drivers/crypto/ccp/ccp-ops.c
>> index db8de89d990f..633670220f6c 100644
>> --- a/drivers/crypto/ccp/ccp-ops.c
>> +++ b/drivers/crypto/ccp/ccp-ops.c
>> @@ -840,7 +840,8 @@ static int ccp_run_aes_gcm_cmd(struct ccp_cmd_queue *cmd_q,
>>   		if (ret)
>>   			goto e_tag;
>>   
>> -		ret = memcmp(tag.address, final_wa.address, AES_BLOCK_SIZE);
>> +		ret = crypto_memneq(tag.address, final_wa.address,
>> +				    AES_BLOCK_SIZE) ? -EBADMSG : 0;
>>   		ccp_dm_free(&tag);
>>   	}
>>   
>> -- 
>> 2.22.0.410.gd8fdbe21b5-goog
>>
> 
> Looks like this needs:
> 
> 	Fixes: 36cf515b9bbe ("crypto: ccp - Enable support for AES GCM on v5 CCPs")
> 	Cc: <stable@xxxxxxxxxxxxxxx> # v4.12+


Yes, it does. For clarity, does that mean you've taken care of this?