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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 
SystemKeyStore()44     private SystemKeyStore() { }
45 
getInstance()46     public static SystemKeyStore getInstance() {
47         return mInstance;
48     }
49 
toHexString(byte[] keyData)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 
generateNewKeyHexString(int numBits, String algName, String keyName)67     public String generateNewKeyHexString(int numBits, String algName, String keyName)
68             throws NoSuchAlgorithmException {
69         return toHexString(generateNewKey(numBits, algName, keyName));
70     }
71 
generateNewKey(int numBits, String algName, String keyName)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 
getKeyFile(String keyName)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 
retrieveKeyHexString(String keyName)114     public String retrieveKeyHexString(String keyName) throws IOException {
115         return toHexString(retrieveKey(keyName));
116     }
117 
retrieveKey(String keyName)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 
deleteKey(String keyName)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