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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package android.security;
     18 
     19 import android.os.Environment;
     20 import android.os.FileUtils;
     21 import android.os.Process;
     22 
     23 import java.io.File;
     24 import java.io.FileInputStream;
     25 import java.io.FileOutputStream;
     26 import java.io.IOException;
     27 import java.security.NoSuchAlgorithmException;
     28 import java.security.SecureRandom;
     29 
     30 import javax.crypto.KeyGenerator;
     31 import javax.crypto.SecretKey;
     32 
     33 import libcore.io.IoUtils;
     34 
     35 /**
     36  *@hide
     37  */
     38 public class SystemKeyStore {
     39 
     40     private static final String SYSTEM_KEYSTORE_DIRECTORY = "misc/systemkeys";
     41     private static final String KEY_FILE_EXTENSION = ".sks";
     42     private static SystemKeyStore mInstance = new SystemKeyStore();
     43 
     44     private SystemKeyStore() { }
     45 
     46     public static SystemKeyStore getInstance() {
     47         return mInstance;
     48     }
     49 
     50     public static String toHexString(byte[] keyData) {
     51         if (keyData == null) {
     52             return null;
     53         }
     54         int keyLen = keyData.length;
     55         int expectedStringLen = keyData.length * 2;
     56         StringBuilder sb = new StringBuilder(expectedStringLen);
     57         for (int i = 0; i < keyData.length; i++) {
     58             String hexStr = Integer.toString(keyData[i] & 0x00FF, 16);
     59             if (hexStr.length() == 1) {
     60                 hexStr = "0" + hexStr;
     61             }
     62             sb.append(hexStr);
     63         }
     64         return sb.toString();
     65     }
     66 
     67     public String generateNewKeyHexString(int numBits, String algName, String keyName)
     68             throws NoSuchAlgorithmException {
     69         return toHexString(generateNewKey(numBits, algName, keyName));
     70     }
     71 
     72     public byte[] generateNewKey(int numBits, String algName, String keyName)
     73             throws NoSuchAlgorithmException {
     74 
     75         // Check if key with similar name exists. If so, return null.
     76         File keyFile = getKeyFile(keyName);
     77         if (keyFile.exists()) {
     78             throw new IllegalArgumentException();
     79         }
     80 
     81         KeyGenerator skg = KeyGenerator.getInstance(algName);
     82         SecureRandom srng = SecureRandom.getInstance("SHA1PRNG");
     83         skg.init(numBits, srng);
     84 
     85         SecretKey sk = skg.generateKey();
     86         byte[] retKey = sk.getEncoded();
     87 
     88         try {
     89             // Store the key
     90             if (!keyFile.createNewFile()) {
     91                 throw new IllegalArgumentException();
     92             }
     93 
     94             FileOutputStream fos = new FileOutputStream(keyFile);
     95             fos.write(retKey);
     96             fos.flush();
     97             FileUtils.sync(fos);
     98             fos.close();
     99             FileUtils.setPermissions(keyFile.getName(), (FileUtils.S_IRUSR | FileUtils.S_IWUSR),
    100                 -1, -1);
    101         } catch (IOException ioe) {
    102             return null;
    103         }
    104         return retKey;
    105     }
    106 
    107     private File getKeyFile(String keyName) {
    108         File sysKeystoreDir = new File(Environment.getDataDirectory(),
    109                 SYSTEM_KEYSTORE_DIRECTORY);
    110         File keyFile = new File(sysKeystoreDir, keyName + KEY_FILE_EXTENSION);
    111         return keyFile;
    112     }
    113 
    114     public String retrieveKeyHexString(String keyName) throws IOException {
    115         return toHexString(retrieveKey(keyName));
    116     }
    117 
    118     public byte[] retrieveKey(String keyName) throws IOException {
    119         File keyFile = getKeyFile(keyName);
    120         if (!keyFile.exists()) {
    121             return null;
    122         }
    123         return IoUtils.readFileAsByteArray(keyFile.toString());
    124     }
    125 
    126     public void deleteKey(String keyName) {
    127 
    128         // Get the file first.
    129         File keyFile = getKeyFile(keyName);
    130         if (!keyFile.exists()) {
    131             throw new IllegalArgumentException();
    132         }
    133 
    134         keyFile.delete();
    135     }
    136 }
    137