Re: [PATCH] net: tls: fix possible info leak in tls_set_device_offload()

[Hangyu Hua]

On 24/2/2023 15:57, Sabrina Dubroca wrote:
> 2023-02-24, 11:33:29 +0800, Hangyu Hua wrote:
> > On 24/2/2023 11:07, Hangyu Hua wrote:
> > > On 23/2/2023 19:15, Sabrina Dubroca wrote:
> > > > 2023-02-23, 17:05:08 +0800, Hangyu Hua wrote:
> > > > > After tls_set_device_offload() fails, we enter tls_set_sw_offload(). But
> > > > > tls_set_sw_offload can't set cctx->iv and cctx->rec_seq to NULL
> > > > > if it fails
> > > > > before kmalloc cctx->iv. This may cause info leak when we call
> > > > > do_tls_getsockopt_conf().
> > > >
> > > > Is there really an issue here?
> > > >
> > > > If both tls_set_device_offload and tls_set_sw_offload fail,
> > > > do_tls_setsockopt_conf will clear crypto_{send,recv} from the context.
> > > > Then the TLS_CRYPTO_INFO_READY in do_tls_getsockopt_conf will fail, so
> > > > we won't try to access iv or rec_seq.
> > >
> > > My bad. I forget memzero_explicit. Then this is harmless. But I still
> > > think it is better to set them to NULL like tls_set_sw_offload's error
> > > path because we don't know there are another way to do this(I will
> > > change the commit log). What do you think?
>
> Yes, I guess for consistency between functions it would be ok.
>
> > Like a rare case, there is a race condition between
> > do_tls_getsockopt_conf and do_tls_setsockopt_conf while the previous
> > condition is met. TLS_CRYPTO_INFO_READY(crypto_info) is not
> > protected by lock_sock in do_tls_getsockopt_conf. It's just too
> > difficult to satisfy both conditions at the same time.
>
> Ugh, thanks for noticing this. We should move the lock_sock in
> getsockopt before TLS_CRYPTO_INFO_READY. Do you want to write that
> patch?
>
> Thanks.

I see. I will make a new patch to fix the race and send v2 of this.

Thanks,
Hangyu