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1
16
22
23 package org.mortbay.j2ee.session;
24
25
29 import java.security.MessageDigest  ;
30 import java.security.NoSuchAlgorithmException ;
31 import java.security.SecureRandom ;
32 import java.util.Random ;
33
34 import javax.servlet.http.HttpServletRequest ;
35
36 import org.jfox.ioc.logger.Logger;
37
38 public class
39 GUIDGenerator
40 implements IdGenerator
41 {
42 protected static final Logger _log=Logger.getLogger(GUIDGenerator.class);
43
44 protected final static int SESSION_ID_BYTES = 16; protected final static String SESSION_ID_HASH_ALGORITHM = "MD5";
46 protected final static String SESSION_ID_RANDOM_ALGORITHM = "SHA1PRNG";
47 protected final static String SESSION_ID_RANDOM_ALGORITHM_ALT = "IBMSecureRandom";
48
49 protected MessageDigest _digest=null;
50 protected Random _random=null;
51
52
56 public synchronized String nextId(HttpServletRequest request)
57 {
58 if (_digest==null) {
59 _digest=getDigest();
60 }
61
62 if (_random==null) {
63 _random=getRandom();
64 }
65
66 byte[] bytes=new byte[SESSION_ID_BYTES];
67
68 _random.nextBytes(bytes);
70
71 bytes=_digest.digest(bytes);
73
74 return encode(bytes);
76 }
77
78
85 protected String encode(byte[] data)
86 {
87 char[] out = new char[((data.length + 2) / 3) * 4];
88 char[] alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+-*".toCharArray();
89
90 for (int i=0, index=0; i<data.length; i+=3, index+=4) {
95 boolean quad = false;
96 boolean trip = false;
97
98 int val = (0xFF & (int) data[i]);
99 val <<= 8;
100 if ((i+1) < data.length) {
101 val |= (0xFF & (int) data[i+1]);
102 trip = true;
103 }
104 val <<= 8;
105 if ((i+2) < data.length) {
106 val |= (0xFF & (int) data[i+2]);
107 quad = true;
108 }
109 out[index+3] = alphabet[(quad? (val & 0x3F): 64)];
110 val >>= 6;
111 out[index+2] = alphabet[(trip? (val & 0x3F): 64)];
112 val >>= 6;
113 out[index+1] = alphabet[val & 0x3F];
114 val >>= 6;
115 out[index+0] = alphabet[val & 0x3F];
116 }
117 return new String (out);
118 }
119
120
124 protected synchronized Random getRandom()
125 {
126 long seed;
127 Random random=null;
128
129 seed=System.currentTimeMillis();
131 seed^=Runtime.getRuntime().freeMemory();
132
133 try {
134 random=SecureRandom.getInstance(SESSION_ID_RANDOM_ALGORITHM);
135 }
136 catch (NoSuchAlgorithmException e)
137 {
138 try
139 {
140 random=SecureRandom.getInstance(SESSION_ID_RANDOM_ALGORITHM_ALT);
141 }
142 catch (NoSuchAlgorithmException e_alt)
143 {
144 _log.error("Could not generate SecureRandom for session-id randomness",e);
145 _log.error("Could not generate SecureRandom for session-id randomness",e_alt);
146 return null;
147 }
148 }
149
150 random.setSeed(seed);
152
153 return random;
154 }
155
156
160 protected synchronized MessageDigest getDigest()
161 {
162 MessageDigest digest=null;
163
164 try {
165 digest=MessageDigest.getInstance(SESSION_ID_HASH_ALGORITHM);
166 } catch (NoSuchAlgorithmException e) {
167 _log.error("Could not generate MessageDigest for session-id hashing",e);
168 return null;
169 }
170
171 return digest;
172 }
173
174 public synchronized Object
175 clone()
176 {
177 try
178 {
179 return super.clone();
180 }
181 catch (CloneNotSupportedException e)
182 {
183 _log.warn("could not clone IdGenerator",e);
184 return null;
185 }
186 }
187 }
188 |
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