From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0F3AFC3F2C6 for ; Tue, 3 Mar 2020 21:32:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D304020870 for ; Tue, 3 Mar 2020 21:32:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732176AbgCCVcw (ORCPT ); Tue, 3 Mar 2020 16:32:52 -0500 Received: from mga09.intel.com ([134.134.136.24]:3053 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731770AbgCCVcw (ORCPT ); Tue, 3 Mar 2020 16:32:52 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Mar 2020 13:32:43 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,511,1574150400"; d="scan'208";a="243731878" Received: from fkuchars-mobl1.ger.corp.intel.com (HELO localhost) ([10.252.4.236]) by orsmga006.jf.intel.com with ESMTP; 03 Mar 2020 13:32:40 -0800 Date: Tue, 3 Mar 2020 23:32:38 +0200 From: Jarkko Sakkinen To: James Bottomley Cc: linux-integrity@vger.kernel.org, Mimi Zohar , David Woodhouse , keyrings@vger.kernel.org Subject: Re: [PATCH v6 3/6] security: keys: trusted: fix TPM2 authorizations Message-ID: <20200303213238.GD110353@linux.intel.com> References: <20200302122759.5204-1-James.Bottomley@HansenPartnership.com> <20200302122759.5204-4-James.Bottomley@HansenPartnership.com> <20200303193302.GC5775@linux.intel.com> <1583267948.3638.7.camel@HansenPartnership.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1583267948.3638.7.camel@HansenPartnership.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Tue, Mar 03, 2020 at 03:39:08PM -0500, James Bottomley wrote: > On Tue, 2020-03-03 at 21:33 +0200, Jarkko Sakkinen wrote: > > On Mon, Mar 02, 2020 at 07:27:56AM -0500, James Bottomley wrote: > > > In TPM 1.2 an authorization was a 20 byte number. The spec > > > actually recommended you to hash variable length passwords and use > > > the sha1 hash as the authorization. Because the spec doesn't > > > require this hashing, the current authorization for trusted keys is > > > a 40 digit hex number. For TPM 2.0 the spec allows the passing in > > > of variable length passwords and passphrases directly, so we should > > > allow that in trusted keys for ease of use. Update the 'blobauth' > > > parameter to take this into account, so we can now use plain text > > > passwords for the keys. > > > > > > so before > > > > > > keyctl add trusted kmk "new 32 > > > blobauth=f572d396fae9206628714fb2ce00f72e94f2258f" > > > > > > after we will accept both the old hex sha1 form as well as a new > > > directly supplied password: > > > > > > keyctl add trusted kmk "new 32 blobauth=hello keyhandle=81000001" > > > > > > Since a sha1 hex code must be exactly 40 bytes long and a direct > > > password must be 20 or less, we use the length as the discriminator > > > for which form is input. > > > > > > Note this is both and enhancement and a potential bug fix. The TPM > > > 2.0 spec requires us to strip leading zeros, meaning empyty > > > authorization is a zero length HMAC whereas we're currently passing > > > in > > > 20 bytes of zeros. A lot of TPMs simply accept this as OK, but the > > > Microsoft TPM emulator rejects it with TPM_RC_BAD_AUTH, so this > > > patch > > > makes the Microsoft TPM emulator work with trusted keys. > > > > The commit message does not mention it but there limitation that you > > cannot have this as a *password*: > > > > f572d396fae9206628714fb2ce00f72e94f2258f > > > > The commit message should explicitly state this. > > Well, that's impossible anyway: the password can be at most > TPM_DIGEST_SIZE characters and the above is twice that, so the > discriminator is fairly simple: if the string size is less than or > equal to TPM_DIGEST_SIZE, then it's a plain password, if it's exactly > 2xTPM_DIGEST_SIZE it must be a hex value and if it's anything else, > it's illegal. I thought the sentence > > Since a sha1 hex code must be exactly 40 bytes long and a direct > password must be 20 or less, we use the length as the discriminator > for which form is input. > > Was the explanation for this, but I can update it. Thanks! No need to update. I missed that part somehow. /Jarkko