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
17package android.security;
18
19import android.os.Environment;
20import android.os.FileUtils;
21
22import java.io.File;
23import java.io.FileOutputStream;
24import java.io.IOException;
25import java.security.NoSuchAlgorithmException;
26import java.security.SecureRandom;
27
28import javax.crypto.KeyGenerator;
29import javax.crypto.SecretKey;
30
31import libcore.io.IoUtils;
32
33/**
34 *@hide
35 */
36public 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