DeviceIdProvider.java

/*
 Swisscom Safe Connect
 Copyright (C) 2014 Swisscom

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/
package com.swisscom.safeconnect.utils;

import android.content.Context;
import android.database.Cursor;
import android.net.Uri;

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

/**
 * Created by vadim on 19.08.14.
 */
public class DeviceIdProvider {

    private static String deviceId = "";
    final protected static char[] hexArray = "0123456789abcdef".toCharArray();

    private static String bytesToHex(byte[] bytes) {
        char[] hexChars = new char[bytes.length * 2];
        for ( int j = 0; j < bytes.length; j++ ) {
            int v = bytes[j] & 0xFF;
            hexChars[j * 2] = hexArray[v >>> 4];
            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
        }
        return new String(hexChars);
    }


    public static String init(Context context) {
        String[] params = { "android_id" };
        Cursor c = context.getContentResolver()
                .query(Uri.parse("content://com.google.android.gsf.gservices"), null, null,
                        params, null);
        // this happens when no google apps are present on the device
        if (c == null) {
            throw new IllegalStateException("Cannot retrieve android id");
        }

        if (!c.moveToFirst() || c.getColumnCount() < 2) {
            throw new IllegalStateException("Cannot retrieve android id");
        }

        try {
            deviceId = Long.toHexString(Long.parseLong(c.getString(1)));
        } catch (NumberFormatException e) {
            throw new IllegalStateException("Cannot retrieve android id");
        }

        c.close();

        // hash the value to get the key
        try {
            MessageDigest messageDigest = MessageDigest.getInstance("SHA-256");
            messageDigest.update(deviceId.getBytes());
            deviceId = bytesToHex(messageDigest.digest());
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalStateException("Cannot retrieve android id");
        }

        return deviceId;
    }

    public static String getDeviceId() {
        return deviceId;
    }
}