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

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Date:	Mon, 9 Jun 2014 16:58:46 +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 16:48, 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


> Mimi
>
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-- 
Thanks,
Dmitry
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