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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 
     22 import java.io.File;
     23 import java.io.FileOutputStream;
     24 import java.io.IOException;
     25 import java.security.NoSuchAlgorithmException;
     26 import java.security.SecureRandom;
     27 
     28 import javax.crypto.KeyGenerator;
     29 import javax.crypto.SecretKey;
     30 
     31 import libcore.io.IoUtils;
     32 
     33 /**
     34  *@hide
     35  */
     36 public class SystemKeyStore {
     37 
     38     private static final String SYSTEM_KEYSTORE_DIRECTORY = "misc/systemkeys";
     39     private static final String KEY_FILE_EXTENSION = ".sks";
     40     private static SystemKeyStore mInstance = new SystemKeyStore();
     41 
     42     private SystemKeyStore() { }
     43 
     44     public static SystemKeyStore getInstance() {
     45         return mInstance;
     46     }
     47 
     48     public static String toHexString(byte[] keyData) {
     49         if (keyData == null) {
     50             return null;
     51         }
     52         int keyLen = keyData.length;
     53         int expectedStringLen = keyData.length * 2;
     54         StringBuilder sb = new StringBuilder(expectedStringLen);
     55         for (int i = 0; i < keyData.length; i++) {
     56             String hexStr = Integer.toString(keyData[i] & 0x00FF, 16);
     57             if (hexStr.length() == 1) {
     58                 hexStr = "0" + hexStr;
     59             }
     60             sb.append(hexStr);
     61         }
     62         return sb.toString();
     63     }
     64 
     65     public String generateNewKeyHexString(int numBits, String algName, String keyName)
     66             throws NoSuchAlgorithmException {
     67         return toHexString(generateNewKey(numBits, algName, keyName));
     68     }
     69 
     70     public byte[] generateNewKey(int numBits, String algName, String keyName)
     71             throws NoSuchAlgorithmException {
     72 
     73         // Check if key with similar name exists. If so, return null.
     74         File keyFile = getKeyFile(keyName);
     75         if (keyFile.exists()) {
     76             throw new IllegalArgumentException();
     77         }
     78 
     79         KeyGenerator skg = KeyGenerator.getInstance(algName);
     80         SecureRandom srng = SecureRandom.getInstance("SHA1PRNG");
     81         skg.init(numBits, srng);
     82 
     83         SecretKey sk = skg.generateKey();
     84         byte[] retKey = sk.getEncoded();
     85 
     86         try {
     87             // Store the key
     88             if (!keyFile.createNewFile()) {
     89                 throw new IllegalArgumentException();
     90             }
     91 
     92             FileOutputStream fos = new FileOutputStream(keyFile);
     93             fos.write(retKey);
     94             fos.flush();
     95             FileUtils.sync(fos);
     96             fos.close();
     97             FileUtils.setPermissions(keyFile.getName(), (FileUtils.S_IRUSR | FileUtils.S_IWUSR),
     98                 -1, -1);
     99         } catch (IOException ioe) {
    100             return null;
    101         }
    102         return retKey;
    103     }
    104 
    105     private File getKeyFile(String keyName) {
    106         File sysKeystoreDir = new File(Environment.getDataDirectory(),
    107                 SYSTEM_KEYSTORE_DIRECTORY);
    108         File keyFile = new File(sysKeystoreDir, keyName + KEY_FILE_EXTENSION);
    109         return keyFile;
    110     }
    111 
    112     public String retrieveKeyHexString(String keyName) throws IOException {
    113         return toHexString(retrieveKey(keyName));
    114     }
    115 
    116     public byte[] retrieveKey(String keyName) throws IOException {
    117         File keyFile = getKeyFile(keyName);
    118         if (!keyFile.exists()) {
    119             return null;
    120         }
    121         return IoUtils.readFileAsByteArray(keyFile.toString());
    122     }
    123 
    124     public void deleteKey(String keyName) {
    125 
    126         // Get the file first.
    127         File keyFile = getKeyFile(keyName);
    128         if (!keyFile.exists()) {
    129             throw new IllegalArgumentException();
    130         }
    131 
    132         keyFile.delete();
    133     }
    134 }
    135