Re: [PATCH] net/tls: support SM4 CCM algorithm

[Vadim Fedorenko]

On 30.09.2021 04:34, Tianjia Zhang wrote:
> Hi Vadim,
>
> On 9/29/21 5:24 AM, Vadim Fedorenko wrote:
> > On 28.09.2021 07:28, Tianjia Zhang wrote:
> > > The IV of CCM mode has special requirements, this patch supports CCM
> > > mode of SM4 algorithm.
> > Have you tried to connect this implementation to application with
> > user-space implementation of CCM mode? I wonder just because I have an
> > issue with AES-CCM Kernel TLS implementation when it's connected to
> > OpenSSL-driven server, but still have no time to fix it correctly.
>
> I did not encounter any issue when using KTLS with AES-CCM algorithm, but the 
> KTLS RX mode on the OpenSSL side does not seem to be supported.
>
> I encountered some problems when using the SM4-CCM algorithm of KTLS. Follow the 
> RFC8998 specification, the handshake has been successful, and the first data 
> transmission can be successful. After that, I will encounter the problem of MAC 
> verification failure, but this is issue on the OpenSSL side. because the problem 
> is still being investigated, I have not opened the code for the time being.
Are you sure that this is an issue on the OpenSSL side? Because absolutely the 
same problem is reported for AES-CCM algo and only when it's offloaded to 
kernel. Looks like encryption of CCM could be broken somehow.

I will try to investigate it a bit later from the AES-CCM side.