linux-kernel - Re: [PATCH v2] KEYS: trusted: tpm2: Fix migratable logic

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Message-ID: <YqA3+vfte7RbbGBa@iki.fi>
Date:   Wed, 8 Jun 2022 08:47:38 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     david.safford@...il.com
Cc:     Ahmad Fatoum <a.fatoum@...gutronix.de>,
        James Bottomley <jejb@...ux.ibm.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>,
        James Morris <jmorris@...ei.org>,
        "SergeE.Hallyn" <serge@...lyn.com>,
        linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] KEYS: trusted: tpm2: Fix migratable logic

On Tue, Jun 07, 2022 at 02:07:57PM -0400, david.safford@...il.com wrote:
> When creating (sealing) a new trusted key, migratable
> trusted keys have the FIXED_TPM and FIXED_PARENT attributes
> set, and non-migratable keys don't. This is backwards, and
> also causes creation to fail when creating a migratable key
> under a migratable parent. (The TPM thinks you are trying to
> seal a non-migratable blob under a migratable parent.)
> 
> The following simple patch fixes the logic, and has been
> tested for all four combinations of migratable and non-migratable
> trusted keys and parent storage keys. With this logic, you will
> get a proper failure if you try to create a non-migratable
> trusted key under a migratable parent storage key, and all other
> combinations work correctly.
> 
> Fixes: e5fb5d2c5a03 ("security: keys: trusted: Make sealed key properly interoperable")
> Signed-off-by: David Safford <david.safford@...il.com>
> ---
> Changelog:
>  * v2:
>    * added Signed-off-by, Fixes, proper Subject and distribution
> .
>  security/keys/trusted-keys/trusted_tpm2.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
> index 0165da386289..2b2c8eb258d5 100644
> --- a/security/keys/trusted-keys/trusted_tpm2.c
> +++ b/security/keys/trusted-keys/trusted_tpm2.c
> @@ -283,8 +283,8 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
>  	/* key properties */
>  	flags = 0;
>  	flags |= options->policydigest_len ? 0 : TPM2_OA_USER_WITH_AUTH;
> -	flags |= payload->migratable ? (TPM2_OA_FIXED_TPM |
> -					TPM2_OA_FIXED_PARENT) : 0;
> +	flags |= payload->migratable ? 0 : (TPM2_OA_FIXED_TPM |
> +					    TPM2_OA_FIXED_PARENT);
>  	tpm_buf_append_u32(&buf, flags);
> 
>  	/* policy */
> --
> 2.36.1

David, thanks a lot for fixing this (what an embarrassing bug)!

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

BR, Jarkko