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/*
* Copyright (C) 2021 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.security.dice;
import android.hardware.security.dice.Bcc;
import android.hardware.security.dice.BccHandover;
import android.hardware.security.dice.InputValues;
import android.hardware.security.dice.Signature;
/**
* An implementation of IDiceNode provides access to DICE secrets to its clients. It
* uses binder's caller UID and security context to identify its callers and assures
* That clients can only access their specific DICE secrets.
* It may operate in two different modes, resident mode and proxy mode.
*
* ## Resident mode.
* In resident mode, the node is in possession of the secrets corresponding to its level in
* the dice tree. It can act as root of the sub tree that it serves. The secrets are memory
* resident in the node. It identifies its callers and prepends the caller's identity to the
* request's vector of input values. It then derives the required secrets by iterating through
* the request's vector of input values in ascending order.
*
* ## Proxy mode.
* In proxy mode, the node has a connection to a parent node. It serves its callers by verifying
* their identity, by prefixing the client's vector of input values with client's identity, and
* forwarding the request to the next level up.
*
* The modes are implementation details that are completely transparent to the clients.
*
* Privacy: Unprivileged apps may not use this service ever because it may provide access to a
* device specific id that is stable across reinstalls, reboots, and applications.
*
* @hide
*/
@SensitiveData
interface IDiceNode {
/**
* Uses the a key derived from the caller's attestation secret to sign the payload using
* RFC 8032 PureEd25519 and returns the signature. The payload is limited to 1024 bytes.
*
* ## Error as service specific exception:
* ResponseCode::PERMISSION_DENIED if the caller does not have the use_sign permission.
*/
Signature sign(in InputValues[] id, in byte[] payload);
/**
* Returns the attestation certificate chain of the caller if `inputValues` is empty or the
* chain to the given child of the caller identified by the `inputValues` vector.
*
* ## Error as service specific exception:
* ResponseCode::PERMISSION_DENIED if the caller does not have the get_attestation_chain
* permission.
*/
Bcc getAttestationChain(in InputValues[] inputValues);
/**
* This function allows a client to become a resident node. Called with empty InputValues
* vectors, an implementation returns the client's DICE secrets. If inputValues is
* not empty, the appropriate derivations are performed starting from the client's level.
* The function must never return secrets pertaining to the implementation or a parent
* thereof in the DICE hierarchy.
*
* ## Error as service specific exception:
* ResponseCode::PERMISSION_DENIED if the implementation does not allow resident nodes
* at the client's level.
*/
BccHandover derive(in InputValues[] inputValues);
/**
* The client demotes itself to the given identity. When serving the calling client,
* the implementation must append the given identities. Essentially, the client assumes
* the identity of one of its children. This operation is not reversible, i.e., there
* is no promotion. Further demotion is possible.
*
* If the operation fails for any reason. No further services must be provided. Ideally,
* a device shutdown/reboot is triggered.
*
* ## Error as service specific exception:
* ResponseCode::PERMISSION_DENIED if the caller does not have the demote permission.
*/
void demote(in InputValues[] inputValues);
}
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