app/src/main/java/com/android/car/debuggingrestrictioncontroller/ui/token/TokenViewModel.java

/*
 * 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 com.android.car.debuggingrestrictioncontroller.ui.token;

import android.util.Base64;
import androidx.annotation.NonNull;
import androidx.lifecycle.LiveData;
import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.ViewModel;
import com.android.car.debuggingrestrictioncontroller.BuildConfig;
import com.android.car.debuggingrestrictioncontroller.auth.TokenPayload;
import com.android.car.debuggingrestrictioncontroller.auth.TokenValidator;
import com.google.firebase.functions.FirebaseFunctions;
import java.security.GeneralSecurityException;
import java.security.SecureRandom;
import java.util.HashMap;
import java.util.Map;

public class TokenViewModel extends ViewModel {

  private static final String TAG = TokenViewModel.class.getSimpleName();
  private static final String TOKEN_ISSUER_API_NAME = BuildConfig.TOKEN_ISSUER_API_NAME;

  private static final String FIELD_NONCE = "nonce";
  private static final String FIELD_TOKEN = "token";

  private static final SecureRandom SECURE_RANDOM = new SecureRandom();
  private final FirebaseFunctions firebaseFunctions = FirebaseFunctions.getInstance();
  private final MutableLiveData<TokenResult> tokenResult = new MutableLiveData<>();

  LiveData<TokenResult> getTokenResult() {
    return tokenResult;
  }

  public void requestAccessToken(@NonNull Map<String, Object> query) {
    byte[] nonceBytes = new byte[16];
    SECURE_RANDOM.nextBytes(nonceBytes);
    final String nonce = Base64.encodeToString(nonceBytes, Base64.DEFAULT);
    query.put(FIELD_NONCE, nonce);

    firebaseFunctions
        .getHttpsCallable(TOKEN_ISSUER_API_NAME)
        .call(query)
        .continueWith(
            task -> {
              @SuppressWarnings("unchecked")
              Map<String, Object> result = (Map<String, Object>) task.getResult().getData();
              return (String) result.get(FIELD_TOKEN);
            })
        .addOnCompleteListener(
            task -> {
              if (task.isSuccessful()) {
                try {
                  TokenPayload validatedPayload =
                      TokenValidator.parseAndVerify(task.getResult(), nonce);
                  HashMap<String, Boolean> approvedRestrictions =
                      validatedPayload.getRestrictions();
                  tokenResult.postValue(new TokenResult(new TokenView("OK", approvedRestrictions)));
                } catch (GeneralSecurityException e) {
                  tokenResult.postValue(new TokenResult("Invalid access token"));
                }
              } else {
                tokenResult.postValue(new TokenResult(task.getException().getMessage()));
              }
            });
  }
}