commons-net.jar is the bytecode of Apache Commons Net library, which implements the client side of many basic Internet protocols.

Apache Commons Net Source Code files are provided in the binary packge (commons-net-3.8.0-bin.zip). You can download it at Apache Commons Net Website.

The source code of commons-net-3.8.0.jar is provided below:

⏎ org/apache/commons/net/smtp/AuthenticatingSMTPClient.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.net.smtp;

import java.io.IOException;
import java.net.InetAddress;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import javax.net.ssl.SSLContext;

import org.apache.commons.net.util.Base64;


/**
 * An SMTP Client class with authentication support (RFC4954).
 *
 * @see SMTPClient
 * @since 3.0
 */
public class AuthenticatingSMTPClient extends SMTPSClient
{
    /**
     * The default AuthenticatingSMTPClient constructor.
     * Creates a new Authenticating SMTP Client.
     */
    public AuthenticatingSMTPClient()
    {
    }

    /**
     * Overloaded constructor that takes a protocol specification
     * @param protocol The protocol to use
     */
    public AuthenticatingSMTPClient(final String protocol) {
        super(protocol);
    }

    /**
     * Overloaded constructor that takes a protocol specification and the implicit argument
     * @param proto the protocol.
     * @param implicit The security mode, {@code true} for implicit, {@code false} for explicit
     * @since 3.3
     */
    public AuthenticatingSMTPClient(final String proto, final boolean implicit)
    {
      super(proto, implicit);
    }

    /**
     * Overloaded constructor that takes the protocol specification, the implicit argument and encoding
     * @param proto the protocol.
     * @param implicit The security mode, {@code true} for implicit, {@code false} for explicit
     * @param encoding the encoding
     * @since 3.3
     */
    public AuthenticatingSMTPClient(final String proto, final boolean implicit, final String encoding)
    {
      super(proto, implicit, encoding);
    }

    /**
     * Overloaded constructor that takes the implicit argument, and using {@link #DEFAULT_PROTOCOL} i.e. TLS
     * @param implicit The security mode, {@code true} for implicit, {@code false} for explicit
     * @param ctx A pre-configured SSL Context.
     * @since 3.3
     */
    public AuthenticatingSMTPClient(final boolean implicit, final SSLContext ctx)
    {
      super(implicit, ctx);
    }

    /**
     * Overloaded constructor that takes a protocol specification and encoding
     * @param protocol The protocol to use
     * @param encoding The encoding to use
     * @since 3.3
     */
    public AuthenticatingSMTPClient(final String protocol, final String encoding) {
        super(protocol, false, encoding);
    }

    /**
     * A convenience method to send the ESMTP EHLO command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param hostname The hostname of the sender.
     * @return The reply code received from the server.
     * @throws SMTPConnectionClosedException
     *      If the SMTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send SMTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @throws IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     */
    public int ehlo(final String hostname) throws IOException
    {
        return sendCommand(SMTPCommand.EHLO, hostname);
    }

    /**
     * Login to the ESMTP server by sending the EHLO command with the
     * given hostname as an argument.  Before performing any mail commands,
     * you must first login.
     * <p>
     * @param hostname  The hostname with which to greet the SMTP server.
     * @return True if successfully completed, false if not.
     * @throws SMTPConnectionClosedException
     *      If the SMTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send SMTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @throws IOException  If an I/O error occurs while either sending a
     *      command to the server or receiving a reply from the server.
     */
    public boolean elogin(final String hostname) throws IOException
    {
        return SMTPReply.isPositiveCompletion(ehlo(hostname));
    }


    /**
     * Login to the ESMTP server by sending the EHLO command with the
     * client hostname as an argument.  Before performing any mail commands,
     * you must first login.
     * <p>
     * @return True if successfully completed, false if not.
     * @throws SMTPConnectionClosedException
     *      If the SMTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send SMTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @throws IOException  If an I/O error occurs while either sending a
     *      command to the server or receiving a reply from the server.
     */
    public boolean elogin() throws IOException
    {
        final String name;
        final InetAddress host;

        host = getLocalAddress();
        name = host.getHostName();

        if (name == null) {
            return false;
        }

        return SMTPReply.isPositiveCompletion(ehlo(name));
    }

    /**
     * Returns the integer values of the enhanced reply code of the last SMTP reply.
     * @return The integer values of the enhanced reply code of the last SMTP reply.
     *  First digit is in the first array element.
     */
    public int[] getEnhancedReplyCode()
    {
        final String reply = getReplyString().substring(4);
        final String[] parts = reply.substring(0, reply.indexOf(' ')).split ("\\.");
        final int[] res = new int[parts.length];
        for (int i = 0; i < parts.length; i++)
        {
            res[i] = Integer.parseInt (parts[i]);
        }
        return res;
    }

    /**
     * Authenticate to the SMTP server by sending the AUTH command with the
     * selected mechanism, using the given username and the given password.
     *
     * @param method the method to use, one of the {@link AuthenticatingSMTPClient.AUTH_METHOD} enum values
     * @param username the user name.
     *        If the method is XOAUTH/XOAUTH2, then this is used as the plain text oauth protocol parameter string
     *        which is Base64-encoded for transmission.
     * @param password the password for the username.
     *        Ignored for XOAUTH/XOAUTH2.
     *
     * @return True if successfully completed, false if not.
     * @throws SMTPConnectionClosedException
     *      If the SMTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send SMTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @throws IOException  If an I/O error occurs while either sending a
     *      command to the server or receiving a reply from the server.
     * @throws NoSuchAlgorithmException If the CRAM hash algorithm
     *      cannot be instantiated by the Java runtime system.
     * @throws InvalidKeyException If the CRAM hash algorithm
     *      failed to use the given password.
     * @throws InvalidKeySpecException If the CRAM hash algorithm
     *      failed to use the given password.
     */
    public boolean auth(final AuthenticatingSMTPClient.AUTH_METHOD method,
                        final String username, final String password)
                        throws IOException, NoSuchAlgorithmException,
                        InvalidKeyException, InvalidKeySpecException
    {
        if (!SMTPReply.isPositiveIntermediate(sendCommand(SMTPCommand.AUTH,
                AUTH_METHOD.getAuthName(method)))) {
            return false;
        }

        if (method.equals(AUTH_METHOD.PLAIN))
        {
            // the server sends an empty response ("334 "), so we don't have to read it.
            return SMTPReply.isPositiveCompletion(sendCommand(
                    Base64.encodeBase64StringUnChunked(("\000" + username + "\000" + password).getBytes(getCharset()))
                ));
        }
        else if (method.equals(AUTH_METHOD.CRAM_MD5))
        {
            // get the CRAM challenge
            final byte[] serverChallenge = Base64.decodeBase64(getReplyString().substring(4).trim());
            // get the Mac instance
            final Mac hmac_md5 = Mac.getInstance("HmacMD5");
            hmac_md5.init(new SecretKeySpec(password.getBytes(getCharset()), "HmacMD5"));
            // compute the result:
            final byte[] hmacResult = convertToHexString(hmac_md5.doFinal(serverChallenge)).getBytes(getCharset());
            // join the byte arrays to form the reply
            final byte[] usernameBytes = username.getBytes(getCharset());
            final byte[] toEncode = new byte[usernameBytes.length + 1 /* the space */ + hmacResult.length];
            System.arraycopy(usernameBytes, 0, toEncode, 0, usernameBytes.length);
            toEncode[usernameBytes.length] = ' ';
            System.arraycopy(hmacResult, 0, toEncode, usernameBytes.length + 1, hmacResult.length);
            // send the reply and read the server code:
            return SMTPReply.isPositiveCompletion(sendCommand(
                Base64.encodeBase64StringUnChunked(toEncode)));
        }
        else if (method.equals(AUTH_METHOD.LOGIN))
        {
            // the server sends fixed responses (base64("Username") and
            // base64("Password")), so we don't have to read them.
            if (!SMTPReply.isPositiveIntermediate(sendCommand(
                Base64.encodeBase64StringUnChunked(username.getBytes(getCharset()))))) {
                return false;
            }
            return SMTPReply.isPositiveCompletion(sendCommand(
                Base64.encodeBase64StringUnChunked(password.getBytes(getCharset()))));
        }
        else if (method.equals(AUTH_METHOD.XOAUTH) || method.equals(AUTH_METHOD.XOAUTH2))
        {
            return SMTPReply.isPositiveIntermediate(sendCommand(
                    Base64.encodeBase64StringUnChunked(username.getBytes(getCharset()))
            ));
        } else {
            return false; // safety check
        }
    }

    /**
     * Converts the given byte array to a String containing the hex values of the bytes.
     * For example, the byte 'A' will be converted to '41', because this is the ASCII code
     * (and the byte value) of the capital letter 'A'.
     * @param a The byte array to convert.
     * @return The resulting String of hex codes.
     */
    private String convertToHexString(final byte[] a)
    {
        final StringBuilder result = new StringBuilder(a.length*2);
        for (final byte element : a)
        {
            if ( (element & 0x0FF) <= 15 ) {
                result.append("0");
            }
            result.append(Integer.toHexString(element & 0x0FF));
        }
        return result.toString();
    }

    /**
     * The enumeration of currently-supported authentication methods.
     */
    public enum AUTH_METHOD
    {
        /** The standarised (RFC4616) PLAIN method, which sends the password unencrypted (insecure). */
        PLAIN,
        /** The standarised (RFC2195) CRAM-MD5 method, which doesn't send the password (secure). */
        CRAM_MD5,
        /** The unstandarised Microsoft LOGIN method, which sends the password unencrypted (insecure). */
        LOGIN,
        /** XOAuth method which accepts a signed and base64ed OAuth URL. */
        XOAUTH,
        /** XOAuth 2 method which accepts a signed and base64ed OAuth JSON. */
        XOAUTH2;

        /**
         * Gets the name of the given authentication method suitable for the server.
         * @param method The authentication method to get the name for.
         * @return The name of the given authentication method suitable for the server.
         */
        public static final String getAuthName(final AUTH_METHOD method)
        {
            if (method.equals(AUTH_METHOD.PLAIN)) {
                return "PLAIN";
            } else if (method.equals(AUTH_METHOD.CRAM_MD5)) {
                return "CRAM-MD5";
            } else if (method.equals(AUTH_METHOD.LOGIN)) {
                return "LOGIN";
            } else if (method.equals(AUTH_METHOD.XOAUTH)) {
                return "XOAUTH";
            } else if (method.equals(AUTH_METHOD.XOAUTH2)) {
                return "XOAUTH2";
            } else {
                return null;
            }
        }
    }
}

/* kate: indent-width 4; replace-tabs on; */

⏎ org/apache/commons/net/smtp/AuthenticatingSMTPClient.java

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Release date: 2020-01-22
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