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Commit 2332583a authored by Andrew Scull's avatar Andrew Scull
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Reference definition of the Android Profile for DICE 

Remove the inline definition of the Android Profile for DICE and instead
reference the definition that exists alongside the Open Profile for DICE
and is now the source of truth for the profile.

Test: n/a
Change-Id: Ia71a674234be13542ad0ce4db0b764e8ee0c7a62
parent 3b3f7f06

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