From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from us-smtp-delivery-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.61])
 by mx.groups.io with SMTP id smtpd.web10.22390.1600263101990813432
 for <devel@edk2.groups.io>;
 Wed, 16 Sep 2020 06:31:42 -0700
Authentication-Results: mx.groups.io;
 dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=ETCZZtyD;
 spf=pass (domain: redhat.com, ip: 205.139.110.61, mailfrom: lersek@redhat.com)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;
	s=mimecast20190719; t=1600263101;
	h=from:from:reply-to:subject:subject:date:date:message-id:message-id:
	 to:to:cc:cc:mime-version:mime-version:content-type:content-type:
	 content-transfer-encoding:content-transfer-encoding:
	 in-reply-to:in-reply-to:references:references;
	bh=73sNH46j5TQM/wYjBkHDVStDmMdFey0WqFN1/Ugl/zs=;
	b=ETCZZtyDldA9+pM+hWbFQtvnrtT6w9SOVbpzJXoPO0v1rR9vp3xuiVyv9ENycITi6CL5R6
	GI12wUSNSv166qgiOKjQ5LtY1oDT1hLftuS5USJzU8RA6JAdJpApk3g9LUGA15iWENsYV7
	/duzClsCG7HkxLD8xXIpjoahECwMeK0=
Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com
 [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id
 us-mta-224-caF_mSZYO2iJRcGNHML6ZA-1; Wed, 16 Sep 2020 09:31:39 -0400
X-MC-Unique: caF_mSZYO2iJRcGNHML6ZA-1
Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14])
	(using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
	(No client certificate requested)
	by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 098361800D4A;
	Wed, 16 Sep 2020 13:31:38 +0000 (UTC)
Received: from lacos-laptop-7.usersys.redhat.com (ovpn-113-213.ams2.redhat.com [10.36.113.213])
	by smtp.corp.redhat.com (Postfix) with ESMTP id A20BC5DEC1;
	Wed, 16 Sep 2020 13:31:36 +0000 (UTC)
Subject: Re: [edk2-devel] [PATCH v3 1/3] CryptoPkg/BaseCryptLib: Add EVP (Envelope) Digest interface
From: "Laszlo Ersek" <lersek@redhat.com>
To: "Yao, Jiewen" <jiewen.yao@intel.com>,
 "devel@edk2.groups.io" <devel@edk2.groups.io>,
 "Zurcher, Christopher J" <christopher.j.zurcher@intel.com>
Cc: "Wang, Jian J" <jian.j.wang@intel.com>, "Lu, XiaoyuX"
 <xiaoyux.lu@intel.com>
References: <CY4PR11MB1288333636B3B9577D2B40E38C210@CY4PR11MB1288.namprd11.prod.outlook.com>
 <1096735a-182d-6ea1-99c2-d06e3caf4523@redhat.com>
Message-ID: <d64c2271-f868-494c-8956-a836578a260a@redhat.com>
Date: Wed, 16 Sep 2020 15:31:35 +0200
MIME-Version: 1.0
In-Reply-To: <1096735a-182d-6ea1-99c2-d06e3caf4523@redhat.com>
X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14
Authentication-Results: relay.mimecast.com;
	auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=lersek@redhat.com
X-Mimecast-Spam-Score: 0.001
X-Mimecast-Originator: redhat.com
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Content-Language: en-US

On 09/16/20 14:39, Laszlo Ersek wrote:
> On 09/16/20 14:07, Yao, Jiewen wrote:
>> I overlooked the behavior that NULL DigestValue will take side effect to free Context.
>>
>> Hi Christopher
>> May I understand why we need free the context?
>> This does not align with other existing HASH or HMAC functions.
> 
> I requested that.
> 
> It makes no sense to keep a finalized context.
> 
> In other words, it makes no sense to separate finalization from freeing.
> A context that has been finalized is unusable for anything except freeing.

To clarify my point about (DigestValue==NULL): the freeing of the
context is not tied to (DigestValue==NULL). When finalizing the context,
the context should *always* be freed. (DigestValue==NULL) only decides
whether we *only* free the context, or we store the computed digest *in
addition to* freeing the context.

So the unconditional part of the finalization is the freeing; the
conditional part is the storing of the digest.

Thanks
Laszlo