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Subject: Re: [PATCH 2/3] crypto: ccp - return an actual key size from RSA
 max_size callback
To:     "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>,
        Herbert Xu <herbert@gondor.apana.org.au>
Cc:     "David S. Miller" <davem@davemloft.net>,
        David Howells <dhowells@redhat.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Gary Hook <gary.hook@amd.com>, keyrings@vger.kernel.org,
        linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org
References: <51c265e4-6153-3e5e-316a-ebef059ac36a@maciej.szmigiero.name>
 <20180302164451.GJ21579@gondor.apana.org.au>
 <087e7b27-f839-8d4b-8da8-5d0fa2f8caf1@maciej.szmigiero.name>
From:   "Hook, Gary" <ghook@amd.com>
Message-ID: <bcf42353-4b07-a14a-e76f-6c520b7b0ba1@amd.com>
Date:   Fri, 2 Mar 2018 17:49:07 -0600
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On 3/2/2018 5:15 PM, Maciej S. Szmigiero wrote:
> On 02.03.2018 17:44, Herbert Xu wrote:
>> On Sat, Feb 24, 2018 at 05:03:21PM +0100, Maciej S. Szmigiero wrote:
>>> rsa-pkcs1pad uses a value returned from a RSA implementation max_size
>>> callback as a size of an input buffer passed to the RSA implementation for
>>> encrypt and sign operations.
>>>
>>> CCP RSA implementation uses a hardware input buffer which size depends only
>>> on the current RSA key length, so it should return this key length in
>>> the max_size callback, too.
>>> This also matches what the kernel software RSA implementation does.
>>>
>>> Previously, the value returned from this callback was always the maximum
>>> RSA key size the CCP hardware supports.
>>> This resulted in this huge buffer being passed by rsa-pkcs1pad to CCP even
>>> for smaller key sizes and then in a buffer overflow when ccp_run_rsa_cmd()
>>> tried to copy this large input buffer into a RSA key length-sized hardware
>>> input buffer.
>>>
>>> Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
>>> Fixes: ceeec0afd684 ("crypto: ccp - Add support for RSA on the CCP")
>>> Cc: stable@vger.kernel.org
>>
>> Patch applied.  Thanks.
> 
> Thanks.
> 
> However, what about the first patch from this series?
> Without it, while it no longer should cause a buffer overflow, in-kernel
> X.509 certificate verification will still fail with CCP driver loaded
> (since CCP RSA implementation has a higher priority than the software
> RSA implementation).
> 
> Maciej
> 


I commented on that one here:
https://marc.info/?l=linux-crypto-vger&m=151986452422791&w=2

Effectively a NACK. We are a reviewing a proposed patch right now.