linux-kernel - Re: [PATCH 2/3] crypto: ccp - return an actual key size from RSA max

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Date:   Fri, 2 Mar 2018 17:49:07 -0600
From:   "Hook, Gary" <ghook@....com>
To:     "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>,
        Herbert Xu <herbert@...dor.apana.org.au>
Cc:     "David S. Miller" <davem@...emloft.net>,
        David Howells <dhowells@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Gary Hook <gary.hook@....com>, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] crypto: ccp - return an actual key size from RSA
 max_size callback

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@...iej.szmigiero.name>
>>> Fixes: ceeec0afd684 ("crypto: ccp - Add support for RSA on the CCP")
>>> Cc: stable@...r.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.