linux-kernel - Re: [PATCH v8 6/6] crypto: AF_ALG

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Date:	Fri, 8 Jul 2016 08:21:58 -0700
From:	Tadeusz Struk <tadeusz.struk@...el.com>
To:	Mat Martineau <mathew.j.martineau@...ux.intel.com>
Cc:	dhowells@...hat.com, herbert@...dor.apana.org.au,
	smueller@...onox.de, linux-api@...r.kernel.org,
	marcel@...tmann.org, linux-kernel@...r.kernel.org,
	keyrings@...r.kernel.org, linux-crypto@...r.kernel.org,
	dwmw2@...radead.org, davem@...emloft.net
Subject: Re: [PATCH v8 6/6] crypto: AF_ALG - add support for key_id

Hi Mat,
On 07/06/2016 12:38 PM, Mat Martineau wrote:
>> 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?
> 
> The way verify_signature is implemented today, the only output is the
> return code. For verify, maybe no read is required (just sendmsg() and
> check the return code).
> 
> But this isn't the extent of the problem: verify_signature needs both
> the signature to be verified and the expected hash as inputs. How is the
> expected hash provided? Would you include it as a cmsg header?
> ALG_OP_VERIFY should have consistent inputs and outputs whether the key
> was set with ALG_SET_KEY_ID or ALG_SET_KEY.

The signature of verify_signature() is quite different from the other
new public key handlers, i.e. create_signature(), encrypt_blob(), and
decrypt_blob(). For verify_signature() we need the following parameters:
encrypted src, hash function to use, expected digest.
The expected digest could be optional if we would modify the
verify_signature() to return the decrypted buffer.
I think the best solution for now would be to just return -ENOPROTOOPT
for verify_signature in SET_KEY_ID mode.
All the four operations will be supported in the SET_KEY mode and
all but verify_signature() will be supported in the SET_KEY_ID mode.
This can added later if we will find a way to pass all parameters in a
consistent way. What do you think? If you are ok with that I will send a
new version soon.
Thanks,
-- 
TS