001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.shiro.crypto;
020
021import org.apache.shiro.util.StringUtils;
022
023/**
024 * Base abstract class for block cipher algorithms.
025 *
026 * <h2>Usage</h2>
027 * Note that this class exists mostly to simplify algorithm-specific subclasses.  Unless you understand the concepts of
028 * cipher modes of operation, block sizes, and padding schemes, and you want direct control of these things, you should
029 * typically not uses instances of this class directly.  Instead, algorithm-specific subclasses, such as
030 * {@link AesCipherService}, {@link BlowfishCipherService}, and others are usually better suited for regular use.
031 * <p/>
032 * However, if you have the need to create a custom block cipher service where no sufficient algorithm-specific subclass
033 * exists in Shiro, this class would be very useful.
034 *
035 * <h2>Configuration</h2>
036 * Block ciphers can accept configuration parameters that direct how they operate.  These parameters concatenated
037 * together in a single String comprise what the JDK JCA documentation calls a
038 * <a href="http://java.sun.com/javase/6/docs/technotes/guides/security/crypto/CryptoSpec.html#trans">transformation
039 * string</a>.  We think that it is better for Shiro to construct this transformation string automatically based on its
040 * constituent parts instead of having the end-user construct the string manually, which may be error prone or
041 * confusing.  To that end, Shiro {@link DefaultBlockCipherService}s have attributes that can be set individually in
042 * a type-safe manner based on your configuration needs, and Shiro will build the transformation string for you.
043 * <p/>
044 * The following sections typically document the configuration options for block (byte array)
045 * {@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])} method invocations.  Streaming configuration
046 * for those same attributes are done via mirrored {@code streaming}* attributes, and their purpose is identical, but
047 * they're only used during streaming {@link #encrypt(java.io.InputStream, java.io.OutputStream, byte[])} and
048 * {@link #decrypt(java.io.InputStream, java.io.OutputStream, byte[])} methods.  See the &quot;Streaming&quot;
049 * section below for more.
050 *
051 * <h3>Block Size</h3>
052 * The block size specifies the number of bits (not bytes) that the cipher operates on when performing an operation.
053 * It can be specified explicitly via the {@link #setBlockSize blockSize} attribute.  If not set, the JCA Provider
054 * default will be used based on the cipher algorithm.  Block sizes are usually very algorithm specific, so set this
055 * value only if you know you don't want the JCA Provider's default for the desired algorithm.  For example, the
056 * AES algorithm's Rijndael implementation <em>only</em> supports a 128 bit block size and will not work with any other
057 * size.
058 * <p/>
059 * Also note that the {@link #setInitializationVectorSize initializationVectorSize} is usually the same as the
060 * {@link #setBlockSize blockSize} in block ciphers.  If you change either attribute, you should ensure that the other
061 * attribute is correct for the target cipher algorithm.
062 *
063 * <h3>Operation Mode</h3>
064 * You may set the block cipher's<a href="http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation">mode of
065 * operation</a> via the {@link #setMode(OperationMode) mode} attribute, which accepts a type-safe
066 * {@link OperationMode OperationMode} enum instance.  This type safety helps avoid typos when specifying the mode and
067 * guarantees that the mode name will be recognized by the underlying JCA Provider.
068 * <p/>
069 * <b>*</b>If no operation mode is specified, Shiro defaults all of its block {@code CipherService} instances to the
070 * {@link OperationMode#CBC CBC} mode, specifically to support auto-generation of initialization vectors during
071 * encryption.  This is different than the JDK's default {@link OperationMode#ECB ECB} mode because {@code ECB} does
072 * not support initialization vectors, which are necessary for strong encryption.  See  the
073 * {@link org.apache.shiro.crypto.JcaCipherService JcaCipherService parent class} class JavaDoc for an extensive
074 * explanation on why we do this and why we do not use the Sun {@code ECB} default.  You also might also want read
075 * the <a href="http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Electronic_codebook_.28ECB.29">Wikipedia
076 * section on ECB<a/> and look at the encrypted image to see an example of why {@code ECB} should not be used in
077 * security-sensitive environments.
078 * <p/>
079 * In the rare case that you need to override the default with a mode not represented
080 * by the {@link OperationMode} enum, you may specify the raw mode name string that will be recognized by your JCA
081 * provider via the {@link #setModeName modeName} attribute.  Because this is not type-safe, it is recommended only to
082 * use this attribute if the {@link OperationMode} enum does not represent your desired mode.
083 * <p/>
084 * <b>NOTE:</b> If you change the mode to one that does not support initialization vectors (such as
085 * {@link OperationMode#ECB ECB} or {@link OperationMode#NONE NONE}), you <em>must</em> turn off auto-generated
086 * initialization vectors by setting {@link #setGenerateInitializationVectors(boolean) generateInitializationVectors}
087 * to {@code false}.  Abandoning initialization vectors significantly weakens encryption, so think twice before
088 * disabling this feature.
089 *
090 * <h3>Padding Scheme</h3>
091 * Because block ciphers process messages in fixed-length blocks, if the final block in a message is not equal to the
092 * block length, <a href="http://en.wikipedia.org/wiki/Padding_(cryptography)">padding</a> is applied to match that
093 * size to maintain the total length of the message.  This is good because it protects data patterns from being
094 * identified  - when all chunks look the same length, it is much harder to infer what that data might be.
095 * <p/>
096 * You may set a padding scheme via the {@link #setPaddingScheme(PaddingScheme) paddingScheme} attribute, which
097 * accepts a type-safe {@link PaddingScheme PaddingScheme} enum instance.  Like the {@link OperationMode} enum,
098 * this enum offers type safety to help avoid typos and guarantees that the mode will be recongized by the underlying
099 * JCA provider.
100 * <p/>
101 * <b>*</b>If no padding scheme is specified, this class defaults to the {@link PaddingScheme#PKCS5} scheme, specifically
102 * to be compliant with the default behavior of auto-generating initialization vectors during encryption (see the
103 * {@link org.apache.shiro.crypto.JcaCipherService JcaCipherService parent class} class JavaDoc for why).
104 * <p/>
105 * In the rare case that you need to override the default with a scheme not represented by the {@link PaddingScheme}
106 * enum, you may specify the raw padding scheme name string that will be recognized by your JCA provider via the
107 * {@link #setPaddingScheme paddingSchemeName} attribute.  Because this is not type-safe, it is recommended only to
108 * use this attribute if the {@link PaddingScheme} enum does not represent your desired scheme.
109 *
110 * <h2>Streaming</h2>
111 * Most people don't think of using block ciphers as stream ciphers, since their name implies working
112 * with block data (i.e. byte arrays) only.  However, block ciphers can be turned into byte-oriented stream ciphers by
113 * using an appropriate {@link OperationMode operation mode} with a {@link #getStreamingBlockSize() streaming block size}
114 * of 8 bits.  This is why the {@link CipherService} interface provides both block and streaming operations.
115 * <p/>
116 * Because this streaming 8-bit block size rarely changes across block-cipher algorithms, default values have been set
117 * for all three streaming configuration parameters.  The defaults are:
118 * <ul>
119 * <li>{@link #setStreamingBlockSize(int) streamingBlockSize} = {@code 8} (bits)</li>
120 * <li>{@link #setStreamingMode streamingMode} = {@link OperationMode#CBC CBC}</li>
121 * <li>{@link #setStreamingPaddingScheme(PaddingScheme) streamingPaddingScheme} = {@link PaddingScheme#PKCS5 PKCS5}</li>
122 * </ul>
123 * <p/>
124 * These attributes have the same meaning as the {@code mode}, {@code blockSize}, and {@code paddingScheme} attributes
125 * described above, but they are applied during streaming method invocations only ({@link #encrypt(java.io.InputStream, java.io.OutputStream, byte[])}
126 * and {@link #decrypt(java.io.InputStream, java.io.OutputStream, byte[])}).
127 *
128 * @see BlowfishCipherService
129 * @see AesCipherService
130 * @see <a href="http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation">Wikipedia: Block Cipher Modes of Operation</a>
131 * @since 1.0
132 */
133public class DefaultBlockCipherService extends AbstractSymmetricCipherService {
134
135    private static final int DEFAULT_BLOCK_SIZE = 0;
136
137    private static final String TRANSFORMATION_STRING_DELIMITER = "/";
138    private static final int DEFAULT_STREAMING_BLOCK_SIZE = 8; //8 bits (1 byte)
139
140    private String modeName;
141    private int blockSize; //size in bits (not bytes) - i.e. a blockSize of 8 equals 1 byte. negative or zero value = use system default
142    private String paddingSchemeName;
143
144    private String streamingModeName;
145    private int streamingBlockSize;
146    private String streamingPaddingSchemeName;
147
148    private String transformationString; //cached value - rebuilt whenever any of its constituent parts change
149    private String streamingTransformationString; //cached value - rebuilt whenever any of its constituent parts change
150
151
152    /**
153     * Creates a new {@link DefaultBlockCipherService} using the specified block cipher {@code algorithmName}.  Per this
154     * class's JavaDoc, this constructor also sets the following defaults:
155     * <ul>
156     * <li>{@code streamingMode} = {@link OperationMode#CBC CBC}</li>
157     * <li>{@code streamingPaddingScheme} = {@link PaddingScheme#NONE none}</li>
158     * <li>{@code streamingBlockSize} = 8</li>
159     * </ul>
160     * All other attributes are null/unset, indicating the JCA Provider defaults will be used.
161     *
162     * @param algorithmName the block cipher algorithm to use when encrypting and decrypting
163     */
164    public DefaultBlockCipherService(String algorithmName) {
165        super(algorithmName);
166
167        this.modeName = OperationMode.CBC.name();
168        this.paddingSchemeName = PaddingScheme.PKCS5.getTransformationName();
169        this.blockSize = DEFAULT_BLOCK_SIZE; //0 = use the JCA provider's default
170
171        this.streamingModeName = OperationMode.CBC.name();
172        this.streamingPaddingSchemeName = PaddingScheme.PKCS5.getTransformationName();
173        this.streamingBlockSize = DEFAULT_STREAMING_BLOCK_SIZE;
174    }
175
176    /**
177     * Returns the cipher operation mode name (as a String) to be used when constructing
178     * {@link javax.crypto.Cipher Cipher} transformation string or {@code null} if the JCA Provider default mode for
179     * the specified {@link #getAlgorithmName() algorithm} should be used.
180     * <p/>
181     * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
182     * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
183     * {@link #getStreamingModeName() streamingModeName} attribute is used when the block cipher is used for
184     * streaming operations.
185     * <p/>
186     * The default value is {@code null} to retain the JCA Provider default.
187     *
188     * @return the cipher operation mode name (as a String) to be used when constructing the
189     *         {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA Provider default
190     *         mode for the specified {@link #getAlgorithmName() algorithm} should be used.
191     */
192    public String getModeName() {
193        return modeName;
194    }
195
196    /**
197     * Sets the cipher operation mode name to be used when constructing the
198     * {@link javax.crypto.Cipher Cipher} transformation string.  A {@code null} value indicates that the JCA Provider
199     * default mode for the specified {@link #getAlgorithmName() algorithm} should be used.
200     * <p/>
201     * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
202     * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
203     * {@link #getStreamingModeName() streamingModeName} attribute is used when the block cipher is used for
204     * streaming operations.
205     * <p/>
206     * The default value is {@code null} to retain the JCA Provider default.
207     * <p/>
208     * <b>NOTE:</b> most standard mode names are represented by the {@link OperationMode OperationMode} enum.  That enum
209     * should be used with the {@link #setMode mode} attribute when possible to retain type-safety and reduce the
210     * possibility of errors.  This method is better used if the {@link OperationMode} enum does not represent the
211     * necessary mode.
212     *
213     * @param modeName the cipher operation mode name to be used when constructing
214     *                 {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA Provider
215     *                 default mode for the specified {@link #getAlgorithmName() algorithm} should be used.
216     * @see #setMode
217     */
218    public void setModeName(String modeName) {
219        this.modeName = modeName;
220        //clear out the transformation string so the next invocation will rebuild it with the new mode:
221        this.transformationString = null;
222    }
223
224    /**
225     * Sets the cipher operation mode of operation to be used when constructing the
226     * {@link javax.crypto.Cipher Cipher} transformation string.  A {@code null} value indicates that the JCA Provider
227     * default mode for the specified {@link #getAlgorithmName() algorithm} should be used.
228     * <p/>
229     * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
230     * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
231     * {@link #setStreamingMode streamingMode} attribute is used when the block cipher is used for
232     * streaming operations.
233     * <p/>
234     * If the {@link OperationMode} enum cannot represent your desired mode, you can set the name explicitly
235     * via the {@link #setModeName modeName} attribute directly.  However, because {@link OperationMode} represents all
236     * standard JDK mode names already, ensure that your underlying JCA Provider supports the non-standard name first.
237     *
238     * @param mode the cipher operation mode to be used when constructing
239     *             {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA Provider
240     *             default mode for the specified {@link #getAlgorithmName() algorithm} should be used.
241     */
242    public void setMode(OperationMode mode) {
243        setModeName(mode.name());
244    }
245
246    /**
247     * Returns the cipher algorithm padding scheme name (as a String) to be used when constructing
248     * {@link javax.crypto.Cipher Cipher} transformation string or {@code null} if the JCA Provider default mode for
249     * the specified {@link #getAlgorithmName() algorithm} should be used.
250     * <p/>
251     * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
252     * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
253     * {@link #getStreamingPaddingSchemeName() streamingPaddingSchemeName} attribute is used when the block cipher is
254     * used for streaming operations.
255     * <p/>
256     * The default value is {@code null} to retain the JCA Provider default.
257     *
258     * @return the padding scheme name (as a String) to be used when constructing the
259     *         {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA Provider default
260     *         padding scheme for the specified {@link #getAlgorithmName() algorithm} should be used.
261     */
262    public String getPaddingSchemeName() {
263        return paddingSchemeName;
264    }
265
266    /**
267     * Sets the padding scheme name to be used when constructing the
268     * {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA Provider default mode for
269     * the specified {@link #getAlgorithmName() algorithm} should be used.
270     * <p/>
271     * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
272     * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
273     * {@link #getStreamingPaddingSchemeName() streamingPaddingSchemeName} attribute is used when the block cipher is
274     * used for streaming operations.
275     * <p/>
276     * The default value is {@code null} to retain the JCA Provider default.
277     * <p/>
278     * <b>NOTE:</b> most standard padding schemes are represented by the {@link PaddingScheme PaddingScheme} enum.
279     * That enum should be used with the {@link #setPaddingScheme paddingScheme} attribute when possible to retain
280     * type-safety and reduce the possibility of errors.  Calling this method however is suitable if the
281     * {@code PaddingScheme} enum does not represent the desired scheme.
282     *
283     * @param paddingSchemeName the padding scheme name to be used when constructing
284     *                          {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA
285     *                          Provider default padding scheme for the specified {@link #getAlgorithmName() algorithm}
286     *                          should be used.
287     * @see #setPaddingScheme
288     */
289    public void setPaddingSchemeName(String paddingSchemeName) {
290        this.paddingSchemeName = paddingSchemeName;
291        //clear out the transformation string so the next invocation will rebuild it with the new padding scheme:
292        this.transformationString = null;
293    }
294
295    /**
296     * Sets the padding scheme to be used when constructing the
297     * {@link javax.crypto.Cipher Cipher} transformation string. A {@code null} value indicates that the JCA Provider
298     * default padding scheme for the specified {@link #getAlgorithmName() algorithm} should be used.
299     * <p/>
300     * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
301     * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
302     * {@link #setStreamingPaddingScheme streamingPaddingScheme} attribute is used when the block cipher is used for
303     * streaming operations.
304     * <p/>
305     * If the {@link PaddingScheme PaddingScheme} enum does represent your desired scheme, you can set the name explicitly
306     * via the {@link #setPaddingSchemeName paddingSchemeName} attribute directly.  However, because
307     * {@code PaddingScheme} represents all standard JDK scheme names already, ensure that your underlying JCA Provider
308     * supports the non-standard name first.
309     *
310     * @param paddingScheme the padding scheme to be used when constructing
311     *                      {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA Provider
312     *                      default padding scheme for the specified {@link #getAlgorithmName() algorithm} should be used.
313     */
314    public void setPaddingScheme(PaddingScheme paddingScheme) {
315        setPaddingSchemeName(paddingScheme.getTransformationName());
316    }
317
318    /**
319     * Returns the block cipher's block size to be used when constructing
320     * {@link javax.crypto.Cipher Cipher} transformation string or {@code 0} if the JCA Provider default block size
321     * for the specified {@link #getAlgorithmName() algorithm} should be used.
322     * <p/>
323     * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
324     * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
325     * {@link #getStreamingBlockSize() streamingBlockSize} attribute is used when the block cipher is used for
326     * streaming operations.
327     * <p/>
328     * The default value is {@code 0} which retains the JCA Provider default.
329     *
330     * @return the block cipher block size to be used when constructing the
331     *         {@link javax.crypto.Cipher Cipher} transformation string, or {@code 0} if the JCA Provider default
332     *         block size for the specified {@link #getAlgorithmName() algorithm} should be used.
333     */
334    public int getBlockSize() {
335        return blockSize;
336    }
337
338    /**
339     * Sets the block cipher's block size to be used when constructing
340     * {@link javax.crypto.Cipher Cipher} transformation string.  {@code 0} indicates that the JCA Provider default
341     * block size for the specified {@link #getAlgorithmName() algorithm} should be used.
342     * <p/>
343     * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
344     * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
345     * {@link #getStreamingBlockSize() streamingBlockSize} attribute is used when the block cipher is used for
346     * streaming operations.
347     * <p/>
348     * The default value is {@code 0} which retains the JCA Provider default.
349     * <p/>
350     * <b>NOTE:</b> block cipher block sizes are very algorithm-specific.  If you change this value, ensure that it
351     * will work with the specified {@link #getAlgorithmName() algorithm}.
352     *
353     * @param blockSize the block cipher block size to be used when constructing the
354     *                  {@link javax.crypto.Cipher Cipher} transformation string, or {@code 0} if the JCA Provider
355     *                  default block size for the specified {@link #getAlgorithmName() algorithm} should be used.
356     */
357    public void setBlockSize(int blockSize) {
358        this.blockSize = Math.max(DEFAULT_BLOCK_SIZE, blockSize);
359        //clear out the transformation string so the next invocation will rebuild it with the new block size:
360        this.transformationString = null;
361    }
362
363    /**
364     * Same purpose as the {@link #getModeName modeName} attribute, but is used instead only for for streaming
365     * operations ({@link #encrypt(java.io.InputStream, java.io.OutputStream, byte[])} and
366     * {@link #decrypt(java.io.InputStream, java.io.OutputStream, byte[])}).
367     * <p/>
368     * Note that unlike the {@link #getModeName modeName} attribute, the default value of this attribute is not
369     * {@code null} - it is {@link OperationMode#CBC CBC} for reasons described in the class-level JavaDoc in the
370     * {@code Streaming} section.
371     *
372     * @return the transformation string mode name to be used for streaming operations only.
373     */
374    public String getStreamingModeName() {
375        return streamingModeName;
376    }
377
378    private boolean isModeStreamingCompatible(String modeName) {
379        return modeName != null &&
380                !modeName.equalsIgnoreCase(OperationMode.ECB.name()) &&
381                !modeName.equalsIgnoreCase(OperationMode.NONE.name());
382    }
383
384    /**
385     * Sets the transformation string mode name to be used for streaming operations only.  The default value is
386     * {@link OperationMode#CBC CBC} for reasons described in the class-level JavaDoc in the {@code Streaming} section.
387     *
388     * @param streamingModeName transformation string mode name to be used for streaming operations only
389     */
390    public void setStreamingModeName(String streamingModeName) {
391        if (!isModeStreamingCompatible(streamingModeName)) {
392            String msg = "mode [" + streamingModeName + "] is not a valid operation mode for block cipher streaming.";
393            throw new IllegalArgumentException(msg);
394        }
395        this.streamingModeName = streamingModeName;
396        //clear out the streaming transformation string so the next invocation will rebuild it with the new mode:
397        this.streamingTransformationString = null;
398    }
399
400    /**
401     * Sets the transformation string mode to be used for streaming operations only.  The default value is
402     * {@link OperationMode#CBC CBC} for reasons described in the class-level JavaDoc in the {@code Streaming} section.
403     *
404     * @param mode the transformation string mode to be used for streaming operations only
405     */
406    public void setStreamingMode(OperationMode mode) {
407        setStreamingModeName(mode.name());
408    }
409
410    public String getStreamingPaddingSchemeName() {
411        return streamingPaddingSchemeName;
412    }
413
414    public void setStreamingPaddingSchemeName(String streamingPaddingSchemeName) {
415        this.streamingPaddingSchemeName = streamingPaddingSchemeName;
416        //clear out the streaming transformation string so the next invocation will rebuild it with the new scheme:
417        this.streamingTransformationString = null;
418    }
419
420    public void setStreamingPaddingScheme(PaddingScheme scheme) {
421        setStreamingPaddingSchemeName(scheme.getTransformationName());
422    }
423
424    public int getStreamingBlockSize() {
425        return streamingBlockSize;
426    }
427
428    public void setStreamingBlockSize(int streamingBlockSize) {
429        this.streamingBlockSize = Math.max(DEFAULT_BLOCK_SIZE, streamingBlockSize);
430        //clear out the streaming transformation string so the next invocation will rebuild it with the new block size:
431        this.streamingTransformationString = null;
432    }
433
434    /**
435     * Returns the transformation string to use with the {@link javax.crypto.Cipher#getInstance} call.  If
436     * {@code streaming} is {@code true}, a block-cipher transformation string compatible with streaming operations will
437     * be constructed and cached for re-use later (see the class-level JavaDoc for more on using block ciphers
438     * for streaming).  If {@code streaming} is {@code false} a normal block-cipher transformation string will
439     * be constructed and cached for later re-use.
440     *
441     * @param streaming if the transformation string is going to be used for a Cipher performing stream-based encryption or not.
442     * @return the transformation string
443     */
444    protected String getTransformationString(boolean streaming) {
445        if (streaming) {
446            if (this.streamingTransformationString == null) {
447                this.streamingTransformationString = buildStreamingTransformationString();
448            }
449            return this.streamingTransformationString;
450        } else {
451            if (this.transformationString == null) {
452                this.transformationString = buildTransformationString();
453            }
454            return this.transformationString;
455        }
456    }
457
458    private String buildTransformationString() {
459        return buildTransformationString(getModeName(), getPaddingSchemeName(), getBlockSize());
460    }
461
462    private String buildStreamingTransformationString() {
463        return buildTransformationString(getStreamingModeName(), getStreamingPaddingSchemeName(), 0);
464    }
465
466    private String buildTransformationString(String modeName, String paddingSchemeName, int blockSize) {
467        StringBuilder sb = new StringBuilder(getAlgorithmName());
468        if (StringUtils.hasText(modeName)) {
469            sb.append(TRANSFORMATION_STRING_DELIMITER).append(modeName);
470        }
471        if (blockSize > 0) {
472            sb.append(blockSize);
473        }
474        if (StringUtils.hasText(paddingSchemeName)) {
475            sb.append(TRANSFORMATION_STRING_DELIMITER).append(paddingSchemeName);
476        }
477        return sb.toString();
478    }
479
480    /**
481     * Returns {@code true} if the specified cipher operation mode name supports initialization vectors,
482     * {@code false} otherwise.
483     *
484     * @param modeName the raw text name of the mode of operation
485     * @return {@code true} if the specified cipher operation mode name supports initialization vectors,
486     *         {@code false} otherwise.
487     */
488    private boolean isModeInitializationVectorCompatible(String modeName) {
489        return modeName != null &&
490                !modeName.equalsIgnoreCase(OperationMode.ECB.name()) &&
491                !modeName.equalsIgnoreCase(OperationMode.NONE.name());
492    }
493
494    /**
495     * Overrides the parent implementation to ensure initialization vectors are always generated if streaming is
496     * enabled (block ciphers <em>must</em> use initialization vectors if they are to be used as a stream cipher).  If
497     * not being used as a stream cipher, then the value is computed based on whether or not the currently configured
498     * {@link #getModeName modeName} is compatible with initialization vectors as well as the result of the configured
499     * {@link #setGenerateInitializationVectors(boolean) generateInitializationVectors} value.
500     *
501     * @param streaming whether or not streaming is being performed
502     * @return {@code true} if streaming or a value computed based on if the currently configured mode is compatible
503     *         with initialization vectors.
504     */
505    @Override
506    protected boolean isGenerateInitializationVectors(boolean streaming) {
507        return streaming || super.isGenerateInitializationVectors() && isModeInitializationVectorCompatible(getModeName());
508    }
509
510    @Override
511    protected byte[] generateInitializationVector(boolean streaming) {
512        if (streaming) {
513            String streamingModeName = getStreamingModeName();
514            if (!isModeInitializationVectorCompatible(streamingModeName)) {
515                String msg = "streamingMode attribute value [" + streamingModeName + "] does not support " +
516                        "Initialization Vectors.  Ensure the streamingMode value represents an operation mode " +
517                        "that is compatible with initialization vectors.";
518                throw new IllegalStateException(msg);
519            }
520        } else {
521            String modeName = getModeName();
522            if (!isModeInitializationVectorCompatible(modeName)) {
523                String msg = "mode attribute value [" + modeName + "] does not support " +
524                        "Initialization Vectors.  Ensure the mode value represents an operation mode " +
525                        "that is compatible with initialization vectors.";
526                throw new IllegalStateException(msg);
527            }
528        }
529        return super.generateInitializationVector(streaming);
530    }
531}