001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.io.input;
018
019import java.io.IOException;
020import java.io.InputStream;
021import java.security.MessageDigest;
022import java.security.NoSuchAlgorithmException;
023import java.util.Objects;
024
025import org.apache.commons.io.build.AbstractStreamBuilder;
026
027/**
028 * This class is an example for using an {@link ObservableInputStream}. It creates its own {@link org.apache.commons.io.input.ObservableInputStream.Observer},
029 * which calculates a checksum using a {@link MessageDigest}, for example, a SHA-512 sum.
030 * <p>
031 * To build an instance, use {@link Builder}.
032 * </p>
033 * <p>
034 * See the MessageDigest section in the <a href= "https://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#MessageDigest"> Java
035 * Cryptography Architecture Standard Algorithm Name Documentation</a> for information about standard algorithm names.
036 * </p>
037 * <p>
038 * You must specify a message digest algorithm name or instance.
039 * </p>
040 * <p>
041 * <em>Note</em>: Neither {@link ObservableInputStream}, nor {@link MessageDigest}, are thread safe, so is {@link MessageDigestInputStream}.
042 * </p>
043 *
044 * @see Builder
045 * @since 2.15.0
046 */
047public final class MessageDigestInputStream extends ObservableInputStream {
048
049    // @formatter:off
050    /**
051     * Builds new {@link MessageDigestInputStream}.
052     *
053     * <p>
054     * For example:
055     * </p>
056     * <pre>{@code
057     * MessageDigestInputStream s = MessageDigestInputStream.builder()
058     *   .setPath(path)
059     *   .setMessageDigest("SHA-512")
060     *   .get();}
061     * </pre>
062     * <p>
063     * You must specify a message digest algorithm name or instance.
064     * </p>
065     *
066     * @see #get()
067     */
068    // @formatter:on
069    public static class Builder extends AbstractStreamBuilder<MessageDigestInputStream, Builder> {
070
071        private MessageDigest messageDigest;
072
073        /**
074         * Constructs a new {@link Builder}.
075         */
076        public Builder() {
077            // empty
078        }
079
080        /**
081         * Builds new {@link MessageDigestInputStream}.
082         * <p>
083         * You must set input that supports {@link #getInputStream()}, otherwise, this method throws an exception.
084         * </p>
085         * <p>
086         * This builder use the following aspects:
087         * </p>
088         * <ul>
089         * <li>{@link #getPath()}</li>
090         * <li>{@link MessageDigest}</li>
091         * </ul>
092         *
093         * @return a new instance.
094         * @throws NullPointerException if messageDigest is null.
095         * @throws IllegalStateException         if the {@code origin} is {@code null}.
096         * @throws UnsupportedOperationException if the origin cannot be converted to an {@link InputStream}.
097         * @throws IOException                   if an I/O error occurs.
098         * @see #getInputStream()
099         */
100        @SuppressWarnings("resource")
101        @Override
102        public MessageDigestInputStream get() throws IOException {
103            return new MessageDigestInputStream(getInputStream(), messageDigest);
104        }
105
106        /**
107         * Sets the message digest.
108         * <p>
109         * The MD5 cryptographic algorithm is weak and should not be used.
110         * </p>
111         *
112         * @param messageDigest the message digest.
113         * @return this
114         */
115        public Builder setMessageDigest(final MessageDigest messageDigest) {
116            this.messageDigest = messageDigest;
117            return this;
118        }
119
120        /**
121         * Sets the name of the name of the message digest algorithm.
122         * <p>
123         * The MD5 cryptographic algorithm is weak and should not be used.
124         * </p>
125         *
126         * @param algorithm the name of the algorithm. See the MessageDigest section in the
127         *                  <a href= "https://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#MessageDigest"> Java Cryptography
128         *                  Architecture Standard Algorithm Name Documentation</a> for information about standard algorithm names.
129         * @return this
130         * @throws NoSuchAlgorithmException if no Provider supports a MessageDigestSpi implementation for the specified algorithm.
131         */
132        public Builder setMessageDigest(final String algorithm) throws NoSuchAlgorithmException {
133            this.messageDigest = MessageDigest.getInstance(algorithm);
134            return this;
135        }
136
137    }
138
139    /**
140     * Maintains the message digest.
141     */
142    public static class MessageDigestMaintainingObserver extends Observer {
143
144        private final MessageDigest messageDigest;
145
146        /**
147         * Constructs an MessageDigestMaintainingObserver for the given MessageDigest.
148         *
149         * @param messageDigest the message digest to use
150         * @throws NullPointerException if messageDigest is null.
151         */
152        public MessageDigestMaintainingObserver(final MessageDigest messageDigest) {
153            this.messageDigest = Objects.requireNonNull(messageDigest, "messageDigest");
154        }
155
156        @Override
157        public void data(final byte[] input, final int offset, final int length) throws IOException {
158            messageDigest.update(input, offset, length);
159        }
160
161        @Override
162        public void data(final int input) throws IOException {
163            messageDigest.update((byte) input);
164        }
165    }
166
167    /**
168     * Constructs a new {@link Builder}.
169     *
170     * @return a new {@link Builder}.
171     */
172    public static Builder builder() {
173        return new Builder();
174    }
175
176    private final MessageDigest messageDigest;
177
178    /**
179     * Constructs a new instance, which calculates a signature on the given stream, using the given {@link MessageDigest}.
180     * <p>
181     * The MD5 cryptographic algorithm is weak and should not be used.
182     * </p>
183     *
184     * @param inputStream   the stream to calculate the message digest for
185     * @param messageDigest the message digest to use
186     * @throws NullPointerException if messageDigest is null.
187     */
188    private MessageDigestInputStream(final InputStream inputStream, final MessageDigest messageDigest) {
189        super(inputStream, new MessageDigestMaintainingObserver(messageDigest));
190        this.messageDigest = messageDigest;
191    }
192
193    /**
194     * Gets the {@link MessageDigest}, which is being used for generating the checksum.
195     * <p>
196     * <em>Note</em>: The checksum will only reflect the data, which has been read so far. This is probably not, what you expect. Make sure, that the complete
197     * data has been read, if that is what you want. The easiest way to do so is by invoking {@link #consume()}.
198     * </p>
199     *
200     * @return the message digest used
201     */
202    public MessageDigest getMessageDigest() {
203        return messageDigest;
204    }
205}