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Viewing changes to storage/src/main/java/org/apache/james/mime4j/storage/CipherStorageProvider.java

  • Committer: Package Import Robot
  • Author(s): David Paleino
  • Date: 2013-11-03 11:13:27 UTC
  • mfrom: (2.1.2 experimental)
  • Revision ID: package-import@ubuntu.com-20131103111327-09huep00ex05z113
Tags: 0.7.2-2
* Upload to unstable
* Fixed Vcs-* fields in debian/control
* Updated debian/watch
* Standards-Version bump to 3.9.5, no changes needed

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storage/src/main/java/org/apache/james/mime4j/storage/CipherStorageProvider.java
 
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/****************************************************************
 
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 * Licensed to the Apache Software Foundation (ASF) under one   *
 
3
 * or more contributor license agreements.  See the NOTICE file *
 
4
 * distributed with this work for additional information        *
 
5
 * regarding copyright ownership.  The ASF licenses this file   *
 
6
 * to you under the Apache License, Version 2.0 (the            *
 
7
 * "License"); you may not use this file except in compliance   *
 
8
 * with the License.  You may obtain a copy of the License at   *
 
9
 *                                                              *
 
10
 *   http://www.apache.org/licenses/LICENSE-2.0                 *
 
11
 *                                                              *
 
12
 * Unless required by applicable law or agreed to in writing,   *
 
13
 * software distributed under the License is distributed on an  *
 
14
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
 
15
 * KIND, either express or implied.  See the License for the    *
 
16
 * specific language governing permissions and limitations      *
 
17
 * under the License.                                           *
 
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 ****************************************************************/
 
19
 
 
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package org.apache.james.mime4j.storage;
 
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import java.io.IOException;
 
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import java.io.InputStream;
 
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import java.security.GeneralSecurityException;
 
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import java.security.NoSuchAlgorithmException;
 
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import javax.crypto.Cipher;
 
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import javax.crypto.CipherInputStream;
 
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import javax.crypto.CipherOutputStream;
 
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import javax.crypto.KeyGenerator;
 
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import javax.crypto.spec.SecretKeySpec;
 
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/**
 
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 * A {@link StorageProvider} that transparently scrambles and unscrambles the
 
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 * data stored by another <code>StorageProvider</code>.
 
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 *
 
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 * <p>
 
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 * Example usage:
 
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 *
 
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 * <pre>
 
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 * StorageProvider mistrusted = new TempFileStorageProvider();
 
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 * StorageProvider enciphered = new CipherStorageProvider(mistrusted);
 
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 * StorageProvider provider = new ThresholdStorageProvider(enciphered);
 
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 * DefaultStorageProvider.setInstance(provider);
 
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 * </pre>
 
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 */
 
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public class CipherStorageProvider extends AbstractStorageProvider {
 
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    private final StorageProvider backend;
 
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    private final String algorithm;
 
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    private final KeyGenerator keygen;
 
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    /**
 
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     * Creates a new <code>CipherStorageProvider</code> for the given back-end
 
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     * using the Blowfish cipher algorithm.
 
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     *
 
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     * @param backend
 
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     *            back-end storage strategy to encrypt.
 
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     */
 
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    public CipherStorageProvider(StorageProvider backend) {
 
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        this(backend, "Blowfish");
 
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    }
 
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    /**
 
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     * Creates a new <code>CipherStorageProvider</code> for the given back-end
 
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     * and cipher algorithm.
 
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     *
 
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     * @param backend
 
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     *            back-end storage strategy to encrypt.
 
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     * @param algorithm
 
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     *            the name of the symmetric block cipher algorithm such as
 
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     *            "Blowfish", "AES" or "RC2".
 
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     */
 
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    public CipherStorageProvider(StorageProvider backend, String algorithm) {
 
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        if (backend == null)
 
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            throw new IllegalArgumentException();
 
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        try {
 
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            this.backend = backend;
 
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            this.algorithm = algorithm;
 
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            this.keygen = KeyGenerator.getInstance(algorithm);
 
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        } catch (NoSuchAlgorithmException e) {
 
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            throw new IllegalArgumentException(e);
 
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        }
 
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    }
 
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    public StorageOutputStream createStorageOutputStream() throws IOException {
 
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        SecretKeySpec skeySpec = getSecretKeySpec();
 
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        return new CipherStorageOutputStream(backend
 
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                .createStorageOutputStream(), algorithm, skeySpec);
 
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    }
 
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    private SecretKeySpec getSecretKeySpec() {
 
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        byte[] raw = keygen.generateKey().getEncoded();
 
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        return new SecretKeySpec(raw, algorithm);
 
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    }
 
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    private static final class CipherStorageOutputStream extends
 
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            StorageOutputStream {
 
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        private final StorageOutputStream storageOut;
 
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        private final String algorithm;
 
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        private final SecretKeySpec skeySpec;
 
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        private final CipherOutputStream cipherOut;
 
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        public CipherStorageOutputStream(StorageOutputStream out,
 
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                String algorithm, SecretKeySpec skeySpec) throws IOException {
 
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            try {
 
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                this.storageOut = out;
 
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                this.algorithm = algorithm;
 
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                this.skeySpec = skeySpec;
 
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                Cipher cipher = Cipher.getInstance(algorithm);
 
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                cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
 
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                this.cipherOut = new CipherOutputStream(out, cipher);
 
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            } catch (GeneralSecurityException e) {
 
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                throw (IOException) new IOException().initCause(e);
 
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            }
 
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        }
 
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        @Override
 
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        public void close() throws IOException {
 
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            super.close();
 
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            cipherOut.close();
 
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        }
 
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        @Override
 
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        protected void write0(byte[] buffer, int offset, int length)
 
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                throws IOException {
 
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            cipherOut.write(buffer, offset, length);
 
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        }
 
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        @Override
 
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        protected Storage toStorage0() throws IOException {
 
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            // cipherOut has already been closed because toStorage calls close
 
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            Storage encrypted = storageOut.toStorage();
 
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            return new CipherStorage(encrypted, algorithm, skeySpec);
 
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        }
 
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    }
 
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    private static final class CipherStorage implements Storage {
 
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        private Storage encrypted;
 
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        private final String algorithm;
 
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        private final SecretKeySpec skeySpec;
 
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        public CipherStorage(Storage encrypted, String algorithm,
 
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                SecretKeySpec skeySpec) {
 
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            this.encrypted = encrypted;
 
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            this.algorithm = algorithm;
 
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            this.skeySpec = skeySpec;
 
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        }
 
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        public void delete() {
 
155
            if (encrypted != null) {
 
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                encrypted.delete();
 
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                encrypted = null;
 
158
            }
 
159
        }
 
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        public InputStream getInputStream() throws IOException {
 
162
            if (encrypted == null)
 
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                throw new IllegalStateException("storage has been deleted");
 
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165
            try {
 
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                Cipher cipher = Cipher.getInstance(algorithm);
 
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                cipher.init(Cipher.DECRYPT_MODE, skeySpec);
 
168
 
 
169
                InputStream in = encrypted.getInputStream();
 
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                return new CipherInputStream(in, cipher);
 
171
            } catch (GeneralSecurityException e) {
 
172
                throw (IOException) new IOException().initCause(e);
 
173
            }
 
174
        }
 
175
    }
 
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}