linux-kernel - Re: [PATCH v5 02/12] integrity: Do not allow machine keyring updates following init

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Date:   Thu, 09 Sep 2021 16:43:54 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Eric Snowberg <eric.snowberg@...cle.com>, keyrings@...r.kernel.org,
        linux-integrity@...r.kernel.org, zohar@...ux.ibm.com,
        dhowells@...hat.com, dwmw2@...radead.org,
        herbert@...dor.apana.org.au, davem@...emloft.net,
        jmorris@...ei.org, serge@...lyn.com
Cc:     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,
        konrad.wilk@...cle.com
Subject: Re: [PATCH v5 02/12] integrity: Do not allow machine keyring
 updates following init

On Tue, 2021-09-07 at 12:01 -0400, Eric Snowberg wrote:
> The machine keyring is setup during init.  No additional keys should be
> allowed to be added afterwards.  Leave the permission as read only.
> 
> Signed-off-by: Eric Snowberg <eric.snowberg@...cle.com>
> ---
> v2: Initial version
> v4: Unmodified from v2
> v5: Rename to machine keyring
> ---
>  security/integrity/digsig.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
> index 8c315be8ad99..5a75ac2c4dbe 100644
> --- a/security/integrity/digsig.c
> +++ b/security/integrity/digsig.c
> @@ -140,7 +140,8 @@ int __init integrity_init_keyring(const unsigned int id)
>  		return -ENOMEM;
>  
>  	restriction->check = restrict_link_to_ima;
> -	perm |= KEY_USR_WRITE;

I would add here inline comment to say mostly the same as the commit
message does.

> +	if (id != INTEGRITY_KEYRING_MACHINE)
> +		perm |= KEY_USR_WRITE;
>  
>  out:
>  	return __integrity_init_keyring(id, perm, restriction);

I checked patch 01 but I lost the email somewhere. The keyring definition
looks now sane.

/Jarkko