Re: [Question] AEAD crypto api for userspace can't deal with a PTlen=0 vector

[Yao Dongdong <yaodongdong@huawei.com>]

On 2015/5/11 14:35, Herbert Xu wrote:
> On Thu, May 07, 2015 at 05:44:53PM +0800, Yao Dongdong wrote:
>> while we use crypto api for userspace to do vectors test for AEAD(aes-gcm),
>> we encounter a problem. There are some test vector's PTlen is 0,for example:
>> [Keylen = 128]
>> [IVlen = 96]
>> [PTlen = 0]
>> [AADlen = 0]
>> [Taglen = 128]
>>
>> Count = 0
>> Key = 7e93936b2e2188cfa9c9882ad901312f
>> IV = b6879804163b9eaf5bfe5218
>> CT =
>> AAD =
>> Tag = aa77daf382d0d63480ff8c8a2dee149e
>>
>> In testing vectors like that, we will get an error result that the decrypt
>> return is success but the right return is a ghash verify fail.
>> After digging into the kernel(3.10) code, we find the function sock_aio_read
>> in net/socket.c has a judgement of iocb->ki_left which will be 0 when we
>> do an aes-gcm decrypt decribed above.
>>
>> static ssize_t sock_aio_read(struct kiocb *iocb, const struct iovec *iov,
>>                 unsigned long nr_segs, loff_t pos)
>> {
>>     struct sock_iocb siocb, *x;
>>
>>     if (pos != 0)
>>         return -ESPIPE;
>>
>>     if (iocb->ki_left == 0) /* Match SYS5 behaviour */
>>         return 0;
>>
>>     x = alloc_sock_iocb(iocb, &siocb);
>>     if (!x)
>>         return -ENOMEM;
>>     return do_sock_read(&x->async_msg, iocb, iocb->ki_filp, iov, nr_segs);
>> }
>>
>> So it directly return before calling aes-gcm decrypt.
>>
>> How can we deal with that?
> Does this still happen if you use recvmsg?
Yes, it works.

> Cheers,


-- 
Kind regards,
Yao Dongdong