linux-kernel - Re: [PATCH v3 09/10] certs: Allow root user to append signed hashes to the blacklist keyring

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Date:   Wed, 20 Jan 2021 12:24:36 +0100
From:   Mickaël Salaün <mic@...ikod.net>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        "David S . Miller" <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        James Morris <jmorris@...ei.org>,
        Mickaël Salaün <mic@...ux.microsoft.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        "Serge E . Hallyn" <serge@...lyn.com>, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [PATCH v3 09/10] certs: Allow root user to append signed hashes
 to the blacklist keyring


On 20/01/2021 06:23, Jarkko Sakkinen wrote:
> On Thu, Jan 14, 2021 at 04:19:08PM +0100, Mickaël Salaün wrote:
>> From: Mickaël Salaün <mic@...ux.microsoft.com>
>>
>> Add a kernel option SYSTEM_BLACKLIST_AUTH_UPDATE to enable the root user
>> to dynamically add new keys to the blacklist keyring.  This enables to
>> invalidate new certificates, either from being loaded in a keyring, or
>> from being trusted in a PKCS#7 certificate chain.  This also enables to
>> add new file hashes to be denied by the integrity infrastructure.
>>
>> Being able to untrust a certificate which could have normaly been
>> trusted is a sensitive operation.  This is why adding new hashes to the
>> blacklist keyring is only allowed when these hashes are signed and
>> vouched by the builtin trusted keyring.  A blacklist hash is stored as a
>> key description.  The PKCS#7 signature of this description must be
>> provided as the key payload.
>>
>> Marking a certificate as untrusted should be enforced while the system
>> is running.  It is then forbiden to remove such blacklist keys.
>>
>> Update blacklist keyring and blacklist key access rights:
>> * allows the root user to search for a specific blacklisted hash, which
>>   make sense because the descriptions are already viewable;
>> * forbids key update;
>> * restricts kernel rights on the blacklist keyring to align with the
>>   root user rights.
>>
>> See the help in tools/certs/print-cert-tbs-hash.sh provided by a
>> following commit.
> 
> Please re-order patches in a way that print-cert-tbs-hash.sh is
> available before this. That way we get rid of this useless remark.

OK

> 
>> Cc: David Howells <dhowells@...hat.com>
>> Cc: David Woodhouse <dwmw2@...radead.org>
>> Signed-off-by: Mickaël Salaün <mic@...ux.microsoft.com>
> 
> /Jarkko
>