linux-kernel - Re: [PATCH] certs: Reference revocation list for all keyrings

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Message-ID: <Y8taCkDpji8AGCUc@kernel.org>
Date:   Sat, 21 Jan 2023 03:20:42 +0000
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Eric Snowberg <eric.snowberg@...cle.com>
Cc:     dhowells@...hat.com, dwmw2@...radead.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org, kanth.ghatraju@...cle.com,
        konrad.wilk@...cle.com
Subject: Re: [PATCH] certs: Reference revocation list for all keyrings

On Tue, Jan 17, 2023 at 12:15:06PM -0500, Eric Snowberg wrote:
> Systems booted with shim have a Forbidden Signature Database called mokx.
> During boot, hashes and certs contained within the mokx are loaded into the
> blacklist keyring.  When calling verify_pkcs7_message_sig the contents of
> the blacklist keyring (or revocation list) are referenced when validating
> keys on the platform keyring. Currently, when validating against the
> secondary or builtin keyrings, the revocation list is not referenced.  Move
> up the check to allow the revocation list to be used with all keyrings,
> including the secondary and builtin, allowing the system owner to take
> corrective action should a vulnerability be found within keys contained
> within either keyring.
> 
> Signed-off-by: Eric Snowberg <eric.snowberg@...cle.com>
> ---
>  certs/system_keyring.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/certs/system_keyring.c b/certs/system_keyring.c
> index 5042cc54fa5e..865a0510fdeb 100644
> --- a/certs/system_keyring.c
> +++ b/certs/system_keyring.c
> @@ -243,6 +243,12 @@ int verify_pkcs7_message_sig(const void *data, size_t len,
>  	if (ret < 0)
>  		goto error;
>  
> +	ret = is_key_on_revocation_list(pkcs7);
> +	if (ret != -ENOKEY) {
> +		pr_devel("PKCS#7 key is on revocation list\n");
> +		goto error;
> +	}
> +
>  	if (!trusted_keys) {
>  		trusted_keys = builtin_trusted_keys;
>  	} else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
> @@ -262,12 +268,6 @@ int verify_pkcs7_message_sig(const void *data, size_t len,
>  			pr_devel("PKCS#7 platform keyring is not available\n");
>  			goto error;
>  		}
> -
> -		ret = is_key_on_revocation_list(pkcs7);
> -		if (ret != -ENOKEY) {
> -			pr_devel("PKCS#7 platform key is on revocation list\n");
> -			goto error;
> -		}
>  	}
>  	ret = pkcs7_validate_trust(pkcs7, trusted_keys);
>  	if (ret < 0) {
> -- 
> 2.27.0
> 

Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>

BR, Jarkko