common/device-side/util/src/com/android/compatibility/common/util/PackageUtil.java

/*
 * Copyright (C) 2017 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.compatibility.common.util;

import android.content.pm.ApplicationInfo;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.os.Build;
import android.support.test.InstrumentationRegistry;
import android.util.Log;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * Device-side utility class for PackageManager-related operations
 */
public class PackageUtil {

    private static final int SYSTEM_APP_MASK =
            ApplicationInfo.FLAG_SYSTEM | ApplicationInfo.FLAG_UPDATED_SYSTEM_APP;
    private static final char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();

    /** Returns true if a package with the given name exists on the device */
    public static boolean exists(String packageName) {
        try {
            return (getPackageManager().getApplicationInfo(packageName,
                    PackageManager.GET_META_DATA) != null);
        } catch(PackageManager.NameNotFoundException e) {
            return false;
        }
    }

    /** Returns true if a package with the given name AND SHA digest exists on the device */
    public static boolean exists(String packageName, String sha) {
        try {
            if (getPackageManager().getApplicationInfo(
                    packageName, PackageManager.GET_META_DATA) == null) {
                return false;
            }
            return sha.equals(computePackageSignatureDigest(packageName));
        } catch (NoSuchAlgorithmException | PackageManager.NameNotFoundException e) {
            return false;
        }
    }

    /** Returns true if the app for the given package name is a system app for this device */
    public static boolean isSystemApp(String packageName) {
        try {
            ApplicationInfo ai = getPackageManager().getApplicationInfo(packageName,
                    PackageManager.GET_META_DATA);
            return ai != null && ((ai.flags & SYSTEM_APP_MASK) != 0);
        } catch(PackageManager.NameNotFoundException e) {
            return false;
        }
    }

    /**
     * Compute the signature SHA digest for a package.
     * @param package the name of the package for which the signature SHA digest is requested
     * @return the signature SHA digest
     */
    public static String computePackageSignatureDigest(String packageName)
            throws NoSuchAlgorithmException, PackageManager.NameNotFoundException {
        PackageInfo packageInfo = getPackageManager()
                .getPackageInfo(packageName, PackageManager.GET_SIGNATURES);
        MessageDigest messageDigest = MessageDigest.getInstance("SHA256");
        messageDigest.update(packageInfo.signatures[0].toByteArray());

        final byte[] digest = messageDigest.digest();
        final int digestLength = digest.length;
        final int charCount = 3 * digestLength - 1;

        final char[] chars = new char[charCount];
        for (int i = 0; i < digestLength; i++) {
            final int byteHex = digest[i] & 0xFF;
            chars[i * 3] = HEX_ARRAY[byteHex >>> 4];
            chars[i * 3 + 1] = HEX_ARRAY[byteHex & 0x0F];
            if (i < digestLength - 1) {
                chars[i * 3 + 2] = ':';
            }
        }
        return new String(chars);
    }

    private static PackageManager getPackageManager() {
        return InstrumentationRegistry.getInstrumentation().getTargetContext().getPackageManager();
    }
}