linux-kernel - Re: [RFC PATCH v5 4/4] KEYS: define an owner trusted keyring

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Date:	Mon, 9 Jun 2014 17:06:02 +0300
From:	Dmitry Kasatkin <dmitry.kasatkin@...il.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	Dmitry Kasatkin <d.kasatkin@...sung.com>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	David Howells <dhowells@...hat.com>,
	Josh Boyer <jwboyer@...hat.com>,
	keyrings <keyrings@...ux-nfs.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v5 4/4] KEYS: define an owner trusted keyring

On 9 June 2014 16:58, Dmitry Kasatkin <dmitry.kasatkin@...il.com> wrote:
> On 9 June 2014 16:48, Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:
>> On Mon, 2014-06-09 at 16:05 +0300, Dmitry Kasatkin wrote:
>>> On 09/06/14 15:51, Mimi Zohar wrote:
>>> > On Mon, 2014-06-09 at 15:13 +0300, Dmitry Kasatkin wrote:
>>> >> On 03/06/14 20:58, Mimi Zohar wrote:
>>> >>> Instead of allowing public keys, with certificates signed by any
>>> >>> key on the system trusted keyring, to be added to a trusted
>>> >>> keyring, this patch further restricts the certificates to those
>>> >>> signed by a particular key on the system keyring.
>>> >>>
>>> >>> When the UEFI secure boot keys are added to the system keyring, the
>>> >>> platform owner will be able to load their key in one of the UEFI DBs
>>> >>> (eg. Machine Owner Key(MOK) list) and select their key, without
>>> >>> having to rebuild the kernel.
>>> >>>
>>> >>> This patch defines an owner trusted keyring, a new boot command
>>> >>> line option 'keys_ownerid=', and defines a new function
>>> >>> get_system_or_owner_trusted_keyring().
>>> >> Hello,
>>> >>
>>> >> The functionality of this entire patch can be replaced by only ~2 lines
>>> >> of code in x509_request_asymmetric_key()
>>> >>
>>> >> if (keys_ownerid || strcmp(keys_ownerid, id))
>>> >>      return -EPERM;
>>> >>
>>> >> Right?
>>> > Are you suggesting only add the one matching key to the system keyring?
>>>
>>> No. I am not suggesting this.
>>>
>>> All built in keys are allocated with KEY_ALLOC_TRUSTED flag and
>>> prep.trusted is set to "true".
>>>
>>> So  the following statement has no effect.
>>
>> Ok, so it has no affect on adding builtin keys to the system keyring.
>>
>>>
>>> #ifdef CONFIG_SYSTEM_TRUSTED_KEYRING
>>>         ret = x509_validate_trust(cert, system_trusted_keyring);
>>>         if (!ret)
>>>             prep->trusted = 1;
>>> #endif
>>
>> The last patch set changes the test to:
>>      ret = x509_validate_trust(cert, get_system_or_owner_trusted_keyring());
>>
>
> It does not really mater. I just copied original code to my response.
>
>>> Keys which come from user-space will check for
>>>
>>> if (keys_ownerid && strcmp(keys_ownerid, id))
>>>      return -EPERM;
>>>
>>>
>>> So 2 lines patch works fine..
>>
>> It works based on the assumption, that you would ever only want a single
>> key on the 'owner' keyring, which is probably not the case.
>>
>
> There is no any assumption here. I am discussing functionality of this patch.
> That is exactly what this patch does - loads single key on the owners keyring.
>
> There is no need for additional keyring for a single key. That is just
> enough to limit verification to the owners key id.
>
> - Dmitry
>
>

There is no reason to have advanced bloated implementation for unsure,
may be never coming use-cases.

It is always very easy to make new patches for the future cases.

- Dmitry

>> Mimi
>>
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