org.bouncycastle.mail.smime.SMIMEGenerator Maven / Gradle / Ivy

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The Bouncy Castle Java APIs for doing S/MIME with the Jakarta Mail APIs. The APIs are designed primarily to be used in conjunction with the BC FIPS provider. The APIs may also be used with other providers although if being used in a FIPS context it is the responsibility of the user to ensure that any other providers used are FIPS certified and used appropriately.
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package org.bouncycastle.mail.smime;

import java.io.IOException;
import java.security.NoSuchAlgorithmException;
import java.security.Provider;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.KeyGenerator;
import jakarta.mail.Header;
import jakarta.mail.MessagingException;
import jakarta.mail.Multipart;
import jakarta.mail.Session;
import jakarta.mail.internet.MimeBodyPart;
import jakarta.mail.internet.MimeMessage;

import org.bouncycastle.cms.CMSEnvelopedGenerator;
import org.bouncycastle.util.Strings;

/**
 * super class of the various generators.
 */
public class SMIMEGenerator
{
    private static Map BASE_CIPHER_NAMES = new HashMap();

    static
    {
        BASE_CIPHER_NAMES.put(CMSEnvelopedGenerator.DES_EDE3_CBC, "DESEDE");
        BASE_CIPHER_NAMES.put(CMSEnvelopedGenerator.AES128_CBC, "AES");
        BASE_CIPHER_NAMES.put(CMSEnvelopedGenerator.AES192_CBC, "AES");
        BASE_CIPHER_NAMES.put(CMSEnvelopedGenerator.AES256_CBC, "AES");
    }

    protected boolean useBase64 = true;
    protected String encoding = "base64";  // default sets base64

    /**
     * base constructor
     */
    protected SMIMEGenerator()
    {
    }

    /**
     * set the content-transfer-encoding for the CMS block (enveloped data, signature, etc...)  in the message.
     *
     * @param encoding the encoding to use, default "base64", use "binary" for a binary encoding.
     */
    public void setContentTransferEncoding(
        String encoding)
    {
        this.encoding = encoding;
        this.useBase64 = Strings.toLowerCase(encoding).equals("base64");
    }

    /**
     * Make sure we have a valid content body part - setting the headers
     * with defaults if neccessary.
     */
    protected MimeBodyPart makeContentBodyPart(
        MimeBodyPart content)
        throws SMIMEException
    {
        //
        // add the headers to the body part - if they are missing, in
        // the event they have already been set the content settings override
        // any defaults that might be set.
        //
        try
        {
            MimeMessage msg = new MimeMessage((Session)null)
            {
                // avoid the call of updateMessageID to prevent
                // DNS issues when trying to evaluate the local host's name
                protected void updateMessageID()
                    throws MessagingException
                {
                    // do nothing
                }
            };

            Enumeration e = content.getAllHeaders();

            msg.setDataHandler(content.getDataHandler());

            while (e.hasMoreElements())
            {
                Header hdr = (Header)e.nextElement();

                msg.setHeader(hdr.getName(), hdr.getValue());
            }

            msg.saveChanges();

            //
            // we do this to make sure at least the default headers are
            // set in the body part.
            //
            e = msg.getAllHeaders();

            while (e.hasMoreElements())
            {
                Header hdr = (Header)e.nextElement();

                if (Strings.toLowerCase(hdr.getName()).startsWith("content-"))
                {
                    content.setHeader(hdr.getName(), hdr.getValue());
                }
            }
        }
        catch (MessagingException e)
        {
            throw new SMIMEException("exception saving message state.", e);
        }

        return content;
    }

    /**
     * extract an appropriate body part from the passed in MimeMessage
     */
    protected MimeBodyPart makeContentBodyPart(
        MimeMessage message)
        throws SMIMEException
    {
        MimeBodyPart content = new MimeBodyPart();

        //
        // add the headers to the body part.
        //
        try
        {
            message.removeHeader("Message-Id");
            message.removeHeader("Mime-Version");

            // JavaMail has a habit of reparsing some content types, if the bodypart is
            // a multipart it might be signed, we rebuild the body part using the raw input stream for the message.
            try
            {
                if (message.getContent() instanceof Multipart)
                {
                    content.setContent(message.getRawInputStream(), message.getContentType());

                    extractHeaders(content, message);

                    return content;
                }
            }
            catch (MessagingException e)
            {
                // fall back to usual method below
            }

            content.setContent(message.getContent(), message.getContentType());

            content.setDataHandler(message.getDataHandler());

            extractHeaders(content, message);
        }
        catch (MessagingException e)
        {
            throw new SMIMEException("exception saving message state.", e);
        }
        catch (IOException e)
        {
            throw new SMIMEException("exception getting message content.", e);
        }

        return content;
    }

    private void extractHeaders(MimeBodyPart content, MimeMessage message)
        throws MessagingException
    {
        Enumeration e = message.getAllHeaders();

        while (e.hasMoreElements())
        {
            Header hdr = (Header)e.nextElement();

            content.addHeader(hdr.getName(), hdr.getValue());
        }
    }

    protected KeyGenerator createSymmetricKeyGenerator(
        String encryptionOID,
        Provider provider)
        throws NoSuchAlgorithmException
    {
        try
        {
            return createKeyGenerator(encryptionOID, provider);
        }
        catch (NoSuchAlgorithmException e)
        {
            try
            {
                String algName = (String)BASE_CIPHER_NAMES.get(encryptionOID);
                if (algName != null)
                {
                    return createKeyGenerator(algName, provider);
                }
            }
            catch (NoSuchAlgorithmException ex)
            {
                // ignore
            }
            if (provider != null)
            {
                return createSymmetricKeyGenerator(encryptionOID, null);
            }
            throw e;
        }
    }

    private KeyGenerator createKeyGenerator(
        String algName,
        Provider provider)
        throws NoSuchAlgorithmException
    {
        if (provider != null)
        {
            return KeyGenerator.getInstance(algName, provider);
        }
        else
        {
            return KeyGenerator.getInstance(algName);
        }
    }
}