Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 1be573a2 authored by Andrew Scull's avatar Andrew Scull Committed by Automerger Merge Worker
Browse files

Reference definition of the Android Profile for DICE am: 2332583a 

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2717193



Change-Id: Ie8c31c4ccbbbcb5febd74af1dfb857a3cdd93521
Signed-off-by: default avatarAutomerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
parents 602cd075 2332583a

security/rkp/README.md

+4 −63
Original line number Diff line number Diff line
@@ -42,7 +42,9 @@ Note that in the full elaboration of this plan, UDS\_pub is not the key used to 
sign certificate requests. Instead, UDS\_pub is just the first public key in a

chain of public keys that end the KeyMint public key. All keys in the chain are

transitively derived from the UDS and joined in a certificate chain following

the specification of the [Android Profile for DICE](#android-profile-for-dice).

the specification of the [Android Profile for DICE](android-profile-for-dice).



[android-profile-for-dice]: https://pigweed.googlesource.com/open-dice/+/refs/heads/main/docs/android.md



### Phases
@@ -53,7 +55,7 @@ binding between the device and the backend. To briefly describe them: 
  certificate requests; a single self-signed certificate signifies this phase.

* DICE (Phase 2): A hardware root of trust key pair is only accessible to ROM

  or ROM extension code; the boot process follows the [Android Profile for

  DICE](#android-profile-for-dice).

  DICE](android-profile-for-dice).

* SoC vendor certified DICE (Phase 3): This is identical to Phase 2, except the

  SoC vendor also does the UDS\_pub extraction or certification in their

  facilities, along with the OEM doing it in the factory. This tightens up the
@@ -163,67 +165,6 @@ The actors in the above diagram are: 
*   **KeyMint** is the secure area component that manages cryptographic keys and

    performs attestations (or perhaps some other secure area component).



### Android Profile for DICE



The Android Profile for DICE is based on the [Open Profile for

DICE](https://pigweed.googlesource.com/open-dice/+/refs/heads/main/docs/specification.md),

with additional constraints for details that the Open Profile for DICE leaves

intentionally underspecified. This section describes the differences from the

Open Profile for DICE.



#### Algorithms



The choice of algorithm must remain consistent with a given certificate e.g. if

SHA-256 is used for the code hash then the authority hash, config hash, etc.

must also use SHA-256.



* UDS and CDI key pairs:

  * Ed25519 / P-256 / P-384

* Hash algorithms (digests can be encoded with their natural size and do not

  need to be the 64-bytes specified by the Open Profile for DICE):

  * SHA-256 / SHA-384 / SHA-512

* HKDF with a supported message digest for all key derivation



#### Mode



A certificate must only set the mode to `normal` when all of the following

conditions are met when loading and verifying the software component that is

being described by the certificate:



* verified boot with anti-rollback protection is enabled

* only the verified boot authorities for production images are enabled

* debug ports, fuses, or other debug facilities are disabled

* device booted software from the normal primary source e.g. internal flash



The mode should never be `not configured`.



Every certificate in the DICE chain will need to be have the `normal` mode in

order to be provisioned with production certificates by RKP.



#### Configuration descriptor



The configuration descriptor is a CBOR map with the following optional fields.

If no fields are relevant, an empty map should be encoded. The key value range

\[-70000, -70999\] is reserved for the Android Profile for DICE.

Implementation-specific fields may be added using key values outside of the

reserved range.



```

| Name              | Key    | Value type | Meaning                           |

| ----------------- | ------ | ---------- | ----------------------------------|

| Component name    | -70002 | tstr       | Name of firmware component / boot |

:                   :        :            : stage                             :

| Component version | -70003 | int / tstr | Version of firmware component /   |

:                   :        :            : boot stage                        :

| Resettable        | -70004 | null       | If present, key changes on factory|

:                   :        :            : reset                             :

| Security version  | -70005 | uint       | Machine-comparable, monotonically |

:                   :        :            : increasing version of the firmware:

:                   :        :            : component / boot stage where a    :

:                   :        :            : greater value indicates a newer   :

:                   :        :            : version                           :

```



### HAL



The remote provisioning HAL provides a simple interface that can be implemented