linux-kernel - Re: [PATCH v7 7/8] ima: check against blacklisted hashes for files with modsig

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Message-ID: <b482896c-6d40-ad77-fc61-e66c21b83103@linux.vnet.ibm.com>
Date:   Sat, 19 Oct 2019 14:30:33 -0400
From:   Nayna <nayna@...ux.vnet.ibm.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>, Nayna Jain <nayna@...ux.ibm.com>,
        linuxppc-dev@...abs.org, linux-efi@...r.kernel.org,
        linux-integrity@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Jeremy Kerr <jk@...abs.org>,
        Matthew Garret <matthew.garret@...ula.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Claudio Carvalho <cclaudio@...ux.ibm.com>,
        George Wilson <gcwilson@...ux.ibm.com>,
        Elaine Palmer <erpalmer@...ibm.com>,
        Eric Ricther <erichte@...ux.ibm.com>,
        "Oliver O'Halloran" <oohall@...il.com>
Subject: Re: [PATCH v7 7/8] ima: check against blacklisted hashes for files
 with modsig

Hi Mimi,


On 10/11/2019 09:19 AM, Mimi Zohar wrote:
> On Mon, 2019-10-07 at 21:14 -0400, Nayna Jain wrote:
>> Asymmetric private keys are used to sign multiple files. The kernel
>> currently support checking against the blacklisted keys. However, if the
>> public key is blacklisted, any file signed by the blacklisted key will
>> automatically fail signature verification. We might not want to blacklist
>> all the files signed by a particular key, but just a single file.
>> Blacklisting the public key is not fine enough granularity.
>>
>> This patch adds support for blacklisting binaries with appended signatures,
>> based on the IMA policy.  Defined is a new policy option
>> "appraise_flag=check_blacklist".
> The blacklisted hash is not the same as the file hash, but is the file
> hash without the appended signature.  Are there tools for calculating
> the blacklisted hash?  Can you provide an example?

I have updated the patch description to specify that the blacklisted 
hash is the file hash without the appended signature. I hope that makes 
it clear now.

Thanks & Regards,
     - Nayna