trusted-keys-fix-migratable-logic

Commit Message

[e-mail] June 3, 2022, 1:28 p.m. UTC

When creating (sealing) a new trusted key, migratable
trusted keys have the FIXED_TPM and FIXED_PERM 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.

david safford
---
 security/keys/trusted-keys/trusted_tpm2.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Ahmad Fatoum June 7, 2022, 6:15 a.m. UTC | #1

Hello David,

On 03.06.22 15:28, [e-mail] wrote:
> When creating (sealing) a new trusted key, migratable
> trusted keys have the FIXED_TPM and FIXED_PERM 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.
> 
> david safford

Thanks for your patch. It looks sensible, but needs some work to
be aligned to the kernel patch guidelines, documented here:
Documentation/process/submitting-patches.rst

What I noticed in particular:

  - Your Signed-off-by is missing
  - Your patch title needs alignment to others in the revision history,
    you could change it e.g. "KEYS: trusted: tpm2: Fix migratable logic"
  - The To:/Cc: list is incomplete. Patches to this file are normally
    merged via Jarkko's tree. get_maintainers.pl will produce a full list
    of people and mailing lists to copy.

Looking forward to your v2.

Cheers,
Ahmad

> ---
>  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 */

Jarkko Sakkinen June 7, 2022, 9:48 a.m. UTC | #2

On Tue, Jun 07, 2022 at 08:15:49AM +0200, Ahmad Fatoum wrote:
> Hello David,
> 
> On 03.06.22 15:28, [e-mail] wrote:
> > When creating (sealing) a new trusted key, migratable
> > trusted keys have the FIXED_TPM and FIXED_PERM 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.
> > 
> > david safford
> 
> Thanks for your patch. It looks sensible, but needs some work to
> be aligned to the kernel patch guidelines, documented here:
> Documentation/process/submitting-patches.rst
> 
> What I noticed in particular:
> 
>   - Your Signed-off-by is missing
>   - Your patch title needs alignment to others in the revision history,
>     you could change it e.g. "KEYS: trusted: tpm2: Fix migratable logic"
>   - The To:/Cc: list is incomplete. Patches to this file are normally
>     merged via Jarkko's tree. get_maintainers.pl will produce a full list
>     of people and mailing lists to copy.
> 
> Looking forward to your v2.

The code change looks legit but it also needs to have this:

Fixes: e5fb5d2c5a03 ("security: keys: trusted: Make sealed key properly interoperable")


> Cheers,
> Ahmad

BR, Jarkko

Patch

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 */