    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}