/*
 * Copyright (C) 2022 Paranoid Android
 *
 * 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.internal.util;

import android.app.Application;
import android.content.Context;
import android.content.res.Resources;
import android.os.Build;
import android.text.TextUtils;
import android.util.Log;

import com.android.internal.R;

import java.lang.reflect.Field;
import java.util.Arrays;

public class PropImitationHooks {

    private static final String TAG = "PropImitationHooks";
    private static final boolean DEBUG = false;

    private static final String[] sCertifiedProps =
            Resources.getSystem().getStringArray(R.array.config_certifiedBuildProperties);

    private static final String sStockFp =
            Resources.getSystem().getString(R.string.config_stockFingerprint);

    private static final Boolean sEnablePropImitation =
            Resources.getSystem().getBoolean(R.bool.config_enablePropImitation);

    private static final String PACKAGE_ARCORE = "com.google.ar.core";
    private static final String PACKAGE_FINSKY = "com.android.vending";
    private static final String PACKAGE_GMS = "com.google.android.gms";
    private static final String PROCESS_GMS_UNSTABLE = PACKAGE_GMS + ".unstable";

    private static volatile boolean sIsGms = false;
    private static volatile boolean sIsFinsky = false;

    public static void setProps(Context context) {
        if (!sEnablePropImitation) {
            dlog("Prop imitation is disabled by config");
            return;
        }

        final String packageName = context.getPackageName();
        final String processName = Application.getProcessName();

        if (TextUtils.isEmpty(packageName) || processName == null) {
            return;
        }

        sIsGms = packageName.equals(PACKAGE_GMS) && processName.equals(PROCESS_GMS_UNSTABLE);
        sIsFinsky = packageName.equals(PACKAGE_FINSKY);

        /* Set Certified Properties for GMSCore
         * Set Stock Fingerprint for ARCore
         */
        if (sCertifiedProps.length == 4 && sIsGms) {
            dlog("Spoofing build for GMS");
            setPropValue("DEVICE", sCertifiedProps[0]);
            setPropValue("PRODUCT", sCertifiedProps[1]);
            setPropValue("MODEL", sCertifiedProps[2]);
            setPropValue("FINGERPRINT", sCertifiedProps[3]);
        } else if (!sStockFp.isEmpty() && packageName.equals(PACKAGE_ARCORE)) {
            dlog("Setting stock fingerprint for: " + packageName);
            setPropValue("FINGERPRINT", sStockFp);
        }
    }

    private static void setPropValue(String key, Object value){
        try {
            dlog("Setting prop " + key + " to " + value.toString());
            Field field = Build.class.getDeclaredField(key);
            field.setAccessible(true);
            field.set(null, value);
            field.setAccessible(false);
        } catch (NoSuchFieldException | IllegalAccessException e) {
            Log.e(TAG, "Failed to set prop " + key, e);
        }
    }

    private static boolean isCallerSafetyNet() {
        return sIsGms && Arrays.stream(Thread.currentThread().getStackTrace())
                .anyMatch(elem -> elem.getClassName().contains("DroidGuard"));
    }

    public static void onEngineGetCertificateChain() {
        // Check stack for SafetyNet or Play Integrity
        if (isCallerSafetyNet() || sIsFinsky) {
            dlog("Blocked key attestation sIsGms=" + sIsGms + " sIsFinsky=" + sIsFinsky);
            throw new UnsupportedOperationException();
        }
    }

    public static void dlog(String msg) {
      if (DEBUG) Log.d(TAG, msg);
    }
}