1 /*
2 * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package javax.crypto;
27
28 import java.io;
29
30 /**
31 * A CipherInputStream is composed of an InputStream and a Cipher so
32 * that read() methods return data that are read in from the
33 * underlying InputStream but have been additionally processed by the
34 * Cipher. The Cipher must be fully initialized before being used by
35 * a CipherInputStream.
36 *
37 * <p> For example, if the Cipher is initialized for decryption, the
38 * CipherInputStream will attempt to read in data and decrypt them,
39 * before returning the decrypted data.
40 *
41 * <p> This class adheres strictly to the semantics, especially the
42 * failure semantics, of its ancestor classes
43 * java.io.FilterInputStream and java.io.InputStream. This class has
44 * exactly those methods specified in its ancestor classes, and
45 * overrides them all. Moreover, this class catches all exceptions
46 * that are not thrown by its ancestor classes. In particular, the
47 * <code>skip</code> method skips, and the <code>available</code>
48 * method counts only data that have been processed by the encapsulated Cipher.
49 *
50 * <p> It is crucial for a programmer using this class not to use
51 * methods that are not defined or overriden in this class (such as a
52 * new method or constructor that is later added to one of the super
53 * classes), because the design and implementation of those methods
54 * are unlikely to have considered security impact with regard to
55 * CipherInputStream.
56 *
57 * @author Li Gong
58 * @see java.io.InputStream
59 * @see java.io.FilterInputStream
60 * @see javax.crypto.Cipher
61 * @see javax.crypto.CipherOutputStream
62 *
63 * @since 1.4
64 */
65
66 public class CipherInputStream extends FilterInputStream {
67
68 // the cipher engine to use to process stream data
69 private Cipher cipher;
70
71 // the underlying input stream
72 private InputStream input;
73
74 /* the buffer holding data that have been read in from the
75 underlying stream, but have not been processed by the cipher
76 engine. the size 512 bytes is somewhat randomly chosen */
77 private byte[] ibuffer = new byte[512];
78
79 // having reached the end of the underlying input stream
80 private boolean done = false;
81
82 /* the buffer holding data that have been processed by the cipher
83 engine, but have not been read out */
84 private byte[] obuffer;
85 // the offset pointing to the next "new" byte
86 private int ostart = 0;
87 // the offset pointing to the last "new" byte
88 private int ofinish = 0;
89
90 /**
91 * private convenience function.
92 *
93 * Entry condition: ostart = ofinish
94 *
95 * Exit condition: ostart <= ofinish
96 *
97 * return (ofinish-ostart) (we have this many bytes for you)
98 * return 0 (no data now, but could have more later)
99 * return -1 (absolutely no more data)
100 */
101 private int getMoreData() throws IOException {
102 if (done) return -1;
103 int readin = input.read(ibuffer);
104 if (readin == -1) {
105 done = true;
106 try {
107 obuffer = cipher.doFinal();
108 }
109 catch (IllegalBlockSizeException e) {obuffer = null;}
110 catch (BadPaddingException e) {obuffer = null;}
111 if (obuffer == null)
112 return -1;
113 else {
114 ostart = 0;
115 ofinish = obuffer.length;
116 return ofinish;
117 }
118 }
119 try {
120 obuffer = cipher.update(ibuffer, 0, readin);
121 } catch (IllegalStateException e) {obuffer = null;};
122 ostart = 0;
123 if (obuffer == null)
124 ofinish = 0;
125 else ofinish = obuffer.length;
126 return ofinish;
127 }
128
129 /**
130 * Constructs a CipherInputStream from an InputStream and a
131 * Cipher.
132 * <br>Note: if the specified input stream or cipher is
133 * null, a NullPointerException may be thrown later when
134 * they are used.
135 * @param is the to-be-processed input stream
136 * @param c an initialized Cipher object
137 */
138 public CipherInputStream(InputStream is, Cipher c) {
139 super(is);
140 input = is;
141 cipher = c;
142 }
143
144 /**
145 * Constructs a CipherInputStream from an InputStream without
146 * specifying a Cipher. This has the effect of constructing a
147 * CipherInputStream using a NullCipher.
148 * <br>Note: if the specified input stream is null, a
149 * NullPointerException may be thrown later when it is used.
150 * @param is the to-be-processed input stream
151 */
152 protected CipherInputStream(InputStream is) {
153 super(is);
154 input = is;
155 cipher = new NullCipher();
156 }
157
158 /**
159 * Reads the next byte of data from this input stream. The value
160 * byte is returned as an <code>int</code> in the range
161 * <code>0</code> to <code>255</code>. If no byte is available
162 * because the end of the stream has been reached, the value
163 * <code>-1</code> is returned. This method blocks until input data
164 * is available, the end of the stream is detected, or an exception
165 * is thrown.
166 * <p>
167 *
168 * @return the next byte of data, or <code>-1</code> if the end of the
169 * stream is reached.
170 * @exception IOException if an I/O error occurs.
171 * @since JCE1.2
172 */
173 public int read() throws IOException {
174 if (ostart >= ofinish) {
175 // we loop for new data as the spec says we are blocking
176 int i = 0;
177 while (i == 0) i = getMoreData();
178 if (i == -1) return -1;
179 }
180 return ((int) obuffer[ostart++] & 0xff);
181 };
182
183 /**
184 * Reads up to <code>b.length</code> bytes of data from this input
185 * stream into an array of bytes.
186 * <p>
187 * The <code>read</code> method of <code>InputStream</code> calls
188 * the <code>read</code> method of three arguments with the arguments
189 * <code>b</code>, <code>0</code>, and <code>b.length</code>.
190 *
191 * @param b the buffer into which the data is read.
192 * @return the total number of bytes read into the buffer, or
193 * <code>-1</code> is there is no more data because the end of
194 * the stream has been reached.
195 * @exception IOException if an I/O error occurs.
196 * @see java.io.InputStream#read(byte[], int, int)
197 * @since JCE1.2
198 */
199 public int read(byte b[]) throws IOException {
200 return read(b, 0, b.length);
201 }
202
203 /**
204 * Reads up to <code>len</code> bytes of data from this input stream
205 * into an array of bytes. This method blocks until some input is
206 * available. If the first argument is <code>null,</code> up to
207 * <code>len</code> bytes are read and discarded.
208 *
209 * @param b the buffer into which the data is read.
210 * @param off the start offset in the destination array
211 * <code>buf</code>
212 * @param len the maximum number of bytes read.
213 * @return the total number of bytes read into the buffer, or
214 * <code>-1</code> if there is no more data because the end of
215 * the stream has been reached.
216 * @exception IOException if an I/O error occurs.
217 * @see java.io.InputStream#read()
218 * @since JCE1.2
219 */
220 public int read(byte b[], int off, int len) throws IOException {
221 if (ostart >= ofinish) {
222 // we loop for new data as the spec says we are blocking
223 int i = 0;
224 while (i == 0) i = getMoreData();
225 if (i == -1) return -1;
226 }
227 if (len <= 0) {
228 return 0;
229 }
230 int available = ofinish - ostart;
231 if (len < available) available = len;
232 if (b != null) {
233 System.arraycopy(obuffer, ostart, b, off, available);
234 }
235 ostart = ostart + available;
236 return available;
237 }
238
239 /**
240 * Skips <code>n</code> bytes of input from the bytes that can be read
241 * from this input stream without blocking.
242 *
243 * <p>Fewer bytes than requested might be skipped.
244 * The actual number of bytes skipped is equal to <code>n</code> or
245 * the result of a call to
246 * {@link #available() <code>available</code>},
247 * whichever is smaller.
248 * If <code>n</code> is less than zero, no bytes are skipped.
249 *
250 * <p>The actual number of bytes skipped is returned.
251 *
252 * @param n the number of bytes to be skipped.
253 * @return the actual number of bytes skipped.
254 * @exception IOException if an I/O error occurs.
255 * @since JCE1.2
256 */
257 public long skip(long n) throws IOException {
258 int available = ofinish - ostart;
259 if (n > available) {
260 n = available;
261 }
262 if (n < 0) {
263 return 0;
264 }
265 ostart += n;
266 return n;
267 }
268
269 /**
270 * Returns the number of bytes that can be read from this input
271 * stream without blocking. The <code>available</code> method of
272 * <code>InputStream</code> returns <code>0</code>. This method
273 * <B>should</B> be overridden by subclasses.
274 *
275 * @return the number of bytes that can be read from this input stream
276 * without blocking.
277 * @exception IOException if an I/O error occurs.
278 * @since JCE1.2
279 */
280 public int available() throws IOException {
281 return (ofinish - ostart);
282 }
283
284 /**
285 * Closes this input stream and releases any system resources
286 * associated with the stream.
287 * <p>
288 * The <code>close</code> method of <code>CipherInputStream</code>
289 * calls the <code>close</code> method of its underlying input
290 * stream.
291 *
292 * @exception IOException if an I/O error occurs.
293 * @since JCE1.2
294 */
295 public void close() throws IOException {
296 input.close();
297 try {
298 // throw away the unprocessed data
299 cipher.doFinal();
300 }
301 catch (BadPaddingException ex) {
302 }
303 catch (IllegalBlockSizeException ex) {
304 }
305 ostart = 0;
306 ofinish = 0;
307 }
308
309 /**
310 * Tests if this input stream supports the <code>mark</code>
311 * and <code>reset</code> methods, which it does not.
312 *
313 * @return <code>false</code>, since this class does not support the
314 * <code>mark</code> and <code>reset</code> methods.
315 * @see java.io.InputStream#mark(int)
316 * @see java.io.InputStream#reset()
317 * @since JCE1.2
318 */
319 public boolean markSupported() {
320 return false;
321 }
322 }
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