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

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Date:	Mon, 09 Jun 2014 16:05:41 +0300
From:	Dmitry Kasatkin <d.kasatkin@...sung.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	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 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.

#ifdef CONFIG_SYSTEM_TRUSTED_KEYRING
        ret = x509_validate_trust(cert, system_trusted_keyring);
        if (!ret)
            prep->trusted = 1;
#endif

Keys which come from user-space will check for

if (keys_ownerid && strcmp(keys_ownerid, id))
     return -EPERM;


So 2 lines patch works fine..

- Dmitry

> The original patch compared the builtin key being loaded onto the system
> keyring and, if it matched the requested key, also added the key to the
> owner keyring.  This version waits for all the builtin keys to be loaded
> onto the system keyring, and in the future the UEFI DB keys, before
> adding the matched key to the owner keyring.  In this version, the keys
> are already on the system keyring.  So no, your two lines would not
> work.
>
> Mimi
>



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