From: Tadeusz Struk <tadeusz.struk@intel.com>
Subject: Re: [PATCH v8 6/6] crypto: AF_ALG - add support for key_id
Date: Tue, 5 Jul 2016 13:27:04 -0700
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Cc: dhowells@redhat.com, herbert@gondor.apana.org.au,
	smueller@chronox.de, linux-api@vger.kernel.org,
	marcel@holtmann.org, linux-kernel@vger.kernel.org,
	keyrings@vger.kernel.org, linux-crypto@vger.kernel.org,
	dwmw2@infradead.org, davem@davemloft.net
To: Mat Martineau <mathew.j.martineau@linux.intel.com>
In-Reply-To: <alpine.OSX.2.20.1606291104130.37168@mjmartin-mac01.local>
Sender: linux-crypto-owner@vger.kernel.org

Hi Mat,
On 06/29/2016 11:43 AM, Mat Martineau wrote:
>> +    ret = verify_signature(key, &sig);
>> +    if (!ret) {
>> +        req->dst_len = sizeof(digest);
> 
> I think you fixed the BUG_ON() problem but there's still an issue with
> the handling of the digest. Check the use of sig->digest in
> public_key_verify_signature(), it's an input not an output. Right now it
> looks like 20 uninitialized bytes are compared with the computed digest
> within verify_signature, and then the unintialized bytes are copied to
> req->dst here.
> 
> With some modifications to public_key_verify_signature you could get the
> digest you need, but I'm not sure if verification with a hardware key
> (like a key in a TPM) can or can not provide the digest needed. Maybe
> this is why the verify_signature hook in struct asymmetric_key_subtype
> is optional.
> 
>> +        scatterwalk_map_and_copy(digest, req->dst, 0, req->dst_len, 1);
>> +    } 

So it looks like the only thing that we need to return to the user in
this case is the return code. Do you agree?
Thanks,
-- 
TS