linux-kernel - Re: [PATCH v3 10/14] KEYS: change link restriction for secondary to also trust mok

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Message-ID: <0b178f91b33d1aed7ab90669ef059185e3b38bcc.camel@linux.ibm.com>
Date:   Thu, 12 Aug 2021 18:14:49 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Eric Snowberg <eric.snowberg@...cle.com>
Cc:     keyrings@...r.kernel.org,
        linux-integrity <linux-integrity@...r.kernel.org>,
        David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        James Morris <jmorris@...ei.org>,
        "Serge E . Hallyn" <serge@...lyn.com>, keescook@...omium.org,
        gregkh@...uxfoundation.org, torvalds@...ux-foundation.org,
        scott.branden@...adcom.com, weiyongjun1@...wei.com,
        nayna@...ux.ibm.com, ebiggers@...gle.com, ardb@...nel.org,
        nramas@...ux.microsoft.com, lszubowi@...hat.com,
        linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        James.Bottomley@...senPartnership.com, pjones@...hat.com,
        glin@...e.com, "konrad.wilk@...cle.com" <konrad.wilk@...cle.com>
Subject: Re: [PATCH v3 10/14] KEYS: change link restriction for secondary to
 also trust mok

On Thu, 2021-08-12 at 16:10 -0600, Eric Snowberg wrote:
> > On Aug 12, 2021, at 1:46 PM, Mimi Zohar <zohar@...ux.ibm.com> wrote:
> > 
> > On Wed, 2021-08-11 at 22:18 -0400, Eric Snowberg wrote:
> >> With the introduction of the mok keyring, the end-user may choose to
> >> trust Machine Owner Keys (MOK) within the kernel. If they have chosen to
> >> trust them, the .mok keyring will contain these keys.  If not, the mok
> >> keyring will always be empty.  Update the restriction check to allow the
> >> secondary trusted keyring to also trust mok keys.
> >> 
> >> Signed-off-by: Eric Snowberg <eric.snowberg@...cle.com>
> >> ---
> >> v3: Initial version
> >> ---
> >> certs/system_keyring.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >> 
> >> diff --git a/certs/system_keyring.c b/certs/system_keyring.c
> >> index cb773e09ea67..8cc19a1ff051 100644
> >> --- a/certs/system_keyring.c
> >> +++ b/certs/system_keyring.c
> >> @@ -110,7 +110,7 @@ static __init struct key_restriction *get_builtin_and_secondary_restriction(void
> >> 	if (!restriction)
> >> 		panic("Can't allocate secondary trusted keyring restriction\n");
> >> 
> >> -	restriction->check = restrict_link_by_builtin_and_secondary_trusted;
> >> +	restriction->check = restrict_link_by_builtin_secondary_and_ca_trusted;
> >> 
> >> 	return restriction;
> >> }
> > 
> > Not everyone needs to build a generic kernel, like the distros.  As
> > previously discussed, not everyone is willing to trust the new MOK
> > keyring nor the UEFI variable for enabling it.  For those environments,
> > they should be able to totally disable the MOK keyring.
> > 
> > Please define a Kconfig similar to "CONFIG_SECONDARY_TRUSTED_KEYRING"
> > for MOK.  The "restriction" would be based on the new Kconfig being
> > enabled.
> 
> Yes, I can add that.  Currently there is a Kconfig to enable the secondary 
> and another for IMA to trust the secondary.  Would you like to see two new 
> Kconfig options added?  One that allows the secondary to use the mok as a new 
> trust  source and another for IMA to trust the mok keyring.  Or a single Kconfig 
> that handles both?  Thanks.

A single Kconfig option for enabling the new keyring should be fine.

thanks,

Mimi