001/* CipherInputStream.java -- Filters input through a cipher.
002   Copyright (C) 2004  Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package javax.crypto;
040
041import gnu.classpath.Configuration;
042import gnu.classpath.debug.Component;
043import gnu.classpath.debug.SystemLogger;
044
045import java.io.FilterInputStream;
046import java.io.IOException;
047import java.io.InputStream;
048
049import java.util.logging.Logger;
050
051/**
052 * This is an {@link java.io.InputStream} that filters its data
053 * through a {@link Cipher} before returning it. The <code>Cipher</code>
054 * argument must have been initialized before it is passed to the
055 * constructor.
056 *
057 * @author Casey Marshall (csm@gnu.org)
058 */
059public class CipherInputStream extends FilterInputStream
060{
061
062  // Constants and variables.
063  // ------------------------------------------------------------------------
064
065  private static final Logger logger = SystemLogger.SYSTEM;
066
067  /**
068   * The underlying {@link Cipher} instance.
069   */
070  private final Cipher cipher;
071
072  /**
073   * Data that has been transformed but not read.
074   */
075  private byte[] outBuffer;
076
077  /**
078   * The offset into {@link #outBuffer} where valid data starts.
079   */
080  private int outOffset;
081
082  /**
083   * We set this when the cipher block size is 1, meaning that we can
084   * transform any amount of data.
085   */
086  private final boolean isStream;
087
088  /**
089   * Whether or not we've reached the end of the stream.
090   */
091  private boolean eof;
092
093  // Constructors.
094  // ------------------------------------------------------------------------
095
096  /**
097   * Creates a new input stream with a source input stream and cipher.
098   *
099   * @param in     The underlying input stream.
100   * @param cipher The cipher to filter data through.
101   */
102  public CipherInputStream(InputStream in, Cipher cipher)
103  {
104    super (in);
105    this.cipher = cipher;
106    isStream = cipher.getBlockSize () == 1;
107    eof = false;
108    if (Configuration.DEBUG)
109      logger.log (Component.CRYPTO, "I am born; cipher: {0}, stream? {1}",
110                  new Object[] { cipher.getAlgorithm (),
111                                 Boolean.valueOf (isStream) });
112  }
113
114  /**
115   * Creates a new input stream without a cipher. This constructor is
116   * <code>protected</code> because this class does not work without an
117   * underlying cipher.
118   *
119   * @param in The underlying input stream.
120   */
121  protected CipherInputStream(InputStream in)
122  {
123    this (in, new NullCipher ());
124  }
125
126  // Instance methods overriding java.io.FilterInputStream.
127  // ------------------------------------------------------------------------
128
129  /**
130   * Returns the number of bytes available without blocking. The value
131   * returned is the number of bytes that have been processed by the
132   * cipher, and which are currently buffered by this class.
133   *
134   * @return The number of bytes immediately available.
135   * @throws java.io.IOException If an I/O exception occurs.
136   */
137  public int available() throws IOException
138  {
139    if (isStream)
140      return super.available();
141    if (outBuffer == null || outOffset >= outBuffer.length)
142      nextBlock ();
143    return outBuffer.length - outOffset;
144  }
145
146  /**
147   * Close this input stream. This method merely calls the {@link
148   * java.io.InputStream#close()} method of the underlying input stream.
149   *
150   * @throws java.io.IOException If an I/O exception occurs.
151   */
152  public synchronized void close() throws IOException
153  {
154    super.close();
155  }
156
157  /**
158   * Read a single byte from this input stream; returns -1 on the
159   * end-of-file.
160   *
161   * @return The byte read, or -1 if there are no more bytes.
162   * @throws java.io.IOExcpetion If an I/O exception occurs.
163   */
164  public synchronized int read() throws IOException
165  {
166    if (isStream)
167      {
168        byte[] buf = new byte[1];
169        int in = super.read();
170        if (in == -1)
171          return -1;
172        buf[0] = (byte) in;
173        try
174          {
175            cipher.update(buf, 0, 1, buf, 0);
176          }
177        catch (ShortBufferException shouldNotHappen)
178          {
179            throw new IOException(shouldNotHappen.getMessage());
180          }
181        return buf[0] & 0xFF;
182      }
183
184    if (outBuffer == null || outOffset == outBuffer.length)
185      {
186        if (eof)
187          return -1;
188        nextBlock ();
189      }
190    return outBuffer [outOffset++] & 0xFF;
191  }
192
193  /**
194   * Read bytes into an array, returning the number of bytes read or -1
195   * on the end-of-file.
196   *
197   * @param buf The byte array to read into.
198   * @param off The offset in <code>buf</code> to start.
199   * @param len The maximum number of bytes to read.
200   * @return The number of bytes read, or -1 on the end-of-file.
201   * @throws java.io.IOException If an I/O exception occurs.
202   */
203  public synchronized int read(byte[] buf, int off, int len)
204    throws IOException
205  {
206    // CipherInputStream has this wierd implementation where if
207    // the buffer is null, this call is the same as `skip'.
208    if (buf == null)
209      return (int) skip (len);
210
211    if (isStream)
212      {
213        len = super.read(buf, off, len);
214        if (len > 0)
215          {
216            try
217              {
218                cipher.update(buf, off, len, buf, off);
219              }
220            catch (ShortBufferException shouldNotHappen)
221              {
222                IOException ioe = new IOException ("Short buffer for stream cipher -- this should not happen");
223                ioe.initCause (shouldNotHappen);
224                throw ioe;
225              }
226          }
227        return len;
228      }
229
230    int count = 0;
231    while (count < len)
232      {
233        if (outBuffer == null || outOffset >= outBuffer.length)
234          {
235            if (eof)
236              {
237                if (count == 0)
238                  count = -1;
239                break;
240              }
241            nextBlock();
242          }
243        int l = Math.min (outBuffer.length - outOffset, len - count);
244        System.arraycopy (outBuffer, outOffset, buf, count+off, l);
245        count += l;
246        outOffset += l;
247      }
248    return count;
249  }
250
251  /**
252   * Read bytes into an array, returning the number of bytes read or -1
253   * on the end-of-file.
254   *
255   * @param buf The byte arry to read into.
256   * @return The number of bytes read, or -1 on the end-of-file.
257   * @throws java.io.IOException If an I/O exception occurs.
258   */
259  public int read(byte[] buf) throws IOException
260  {
261    return read(buf, 0, buf.length);
262  }
263
264  /**
265   * Skip a number of bytes. This class only supports skipping as many
266   * bytes as are returned by {@link #available()}, which is the number
267   * of transformed bytes currently in this class's internal buffer.
268   *
269   * @param bytes The number of bytes to skip.
270   * @return The number of bytes skipped.
271   */
272  public long skip(long bytes) throws IOException
273  {
274    if (isStream)
275      {
276        return super.skip(bytes);
277      }
278    long ret = 0;
279    if (bytes > 0 && outBuffer != null && outOffset >= outBuffer.length)
280      {
281        ret = outBuffer.length - outOffset;
282        outOffset = outBuffer.length;
283      }
284    return ret;
285  }
286
287  /**
288   * Returns whether or not this input stream supports the {@link
289   * #mark(long)} and {@link #reset()} methods; this input stream does
290   * not, however, and invariably returns <code>false</code>.
291   *
292   * @return <code>false</code>
293   */
294  public boolean markSupported()
295  {
296    return false;
297  }
298
299  /**
300   * Set the mark. This method is unsupported and is empty.
301   *
302   * @param mark Is ignored.
303   */
304  public void mark(int mark)
305  {
306  }
307
308  /**
309   * Reset to the mark. This method is unsupported and is empty.
310   */
311  public void reset() throws IOException
312  {
313    throw new IOException("reset not supported");
314  }
315
316  // Own methods.
317  // -------------------------------------------------------------------------
318
319  // FIXME: I don't fully understand how this class is supposed to work.
320
321  private void nextBlock() throws IOException
322  {
323    byte[] buf = new byte[cipher.getBlockSize ()];
324    if (Configuration.DEBUG)
325      logger.log (Component.CRYPTO, "getting a new data block");
326
327    try
328      {
329        outBuffer = null;
330        outOffset = 0;
331        while (outBuffer == null)
332          {
333            int l = in.read (buf);
334            if (Configuration.DEBUG)
335              logger.log (Component.CRYPTO, "we read {0} bytes",
336                          Integer.valueOf (l));
337            if (l == -1)
338              {
339                outBuffer = cipher.doFinal ();
340                eof = true;
341                return;
342              }
343
344            outOffset = 0;
345            outBuffer = cipher.update (buf, 0, l);
346          }
347      }
348    catch (BadPaddingException bpe)
349      {
350        IOException ioe = new IOException ("bad padding");
351        ioe.initCause (bpe);
352        throw ioe;
353      }
354    catch (IllegalBlockSizeException ibse)
355      {
356        IOException ioe = new IOException ("illegal block size");
357        ioe.initCause (ibse);
358        throw ioe;
359      }
360    finally
361      {
362        if (Configuration.DEBUG)
363          logger.log (Component.CRYPTO,
364                      "decrypted {0} bytes for reading",
365                      Integer.valueOf (outBuffer.length));
366      }
367  }
368}