Support AuthEnvelopedData in mail SMIME

[bukka]

This adds SMIMEAuthEnveloped classes that work in a similar way as SMIMEEnveloped but are meant for AuthEnvelopedData. That allows using AES GCM and improves S/MIME 4.0 support where this is required.

[rde-infologic]

Hello,

Can someone in bc-java team can merge this ?

That's could be cool to add something like SMIMEEnvelopedUtil in order to crypt or decrypt with good container.

package org.bouncycastle.mail.smime;

import java.util.Arrays;
import java.util.List;

import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.cms.CMSException;
import org.bouncycastle.cms.CMSAuthEnvelopedGenerator;
import org.bouncycastle.cms.RecipientInformationStore;
import org.bouncycastle.mail.smime.SMIMEAuthEnveloped;
import org.bouncycastle.mail.smime.SMIMEAuthEnvelopedGenerator;
import org.bouncycastle.mail.smime.SMIMEEnvelopedGenerator;
import org.bouncycastle.mail.smime.SMIMEEnveloped;

import jakarta.mail.MessagingException;
import jakarta.mail.internet.MimeBodyPart;

public class SMIMEEnvelopedUtil
{
    public static RecipientInformationStore getRecipientInfos(MimeBodyPart message) throws MessagingException, CMSException
    {
        if(message.getContentType().equals(SMIMEAuthEnvelopedGenerator.AUTH_ENCRYPTED_CONTENT_TYPE))
        {
            return new SMIMEAuthEnveloped(message).getRecipientInfos();
        }
        return new SMIMEEnveloped(message).getRecipientInfos();
    }
    
    
    public static SMIMEEnvelopedGenerator getGenerator(ASN1ObjectIdentifier algorithm)
    {        
        List<String> authEnvelopedAlgo = Arrays.asList(
            CMSAuthEnvelopedGenerator.AES128_GCM, 
            CMSAuthEnvelopedGenerator.AES192_GCM, 
            CMSAuthEnvelopedGenerator.AES256_GCM);
        if(authEnvelopedAlgo.contains(algorithm.getId()))
        {
            return new SMIMEAuthEnvelopedGenerator();
        }
        return new SMIMEEnvelopedGenerator();
    }
}

for exemple :

/**
 * Encrypte le message
 */
public SMimeMessage crypter(X509Certificate cert) throws SMimeException
{
    try
    {
        try
        {
            if (cert == null)
            {
                throw new SMimeException(null, E.t("Certificat obligatoire pour l'encryption du message"));
            }

            setDefaults();

            /* Create the encrypter */
            SMIMEEnvelopedGenerator encrypter  = SMIMEEnvelopedUtil.getGenerator(getChiffrementAlgorithm());
            encrypter.setContentTransferEncoding(getContentTransferEncoding());
            encrypter.addRecipientInfoGenerator(
                new JceKeyTransRecipientInfoGenerator(cert).setProvider(SECURITY_PROVIDER));

            /* Encrypt the body part */
            MimeBodyPart encryptedPart = encrypter.generate(bodyPart,
                new JceCMSContentEncryptorBuilder(getChiffrementAlgorithm()).setProvider(SECURITY_PROVIDER).build());

            return new SMimeMessage(encryptedPart, this);
        }
        catch (org.bouncycastle.mail.smime.SMIMEException ex)
        {
            throw new SMimeException(null, E.t(ex.getMessage()), ex);
        }
    }
    catch (Exception e)
    {
        throw new SMimeException(null, E.t("Impossible d'encrypter le message"), e);
    }
}

/**
 * Décrypter le message
 */
public SMimeMessage decrypter(PrivateKey privateKey) throws SMimeException
{
    if (privateKey == null)
    {
        throw new SMimeException(null, E.t("Clé privé obligatoire pour décrypter le message"));
    }

    try
    {
        setDefaults();

        RecipientId recId = new JceKeyTransRecipientId(cert);

        RecipientInformationStore recipientsInfo = SMIMEEnvelopedUtil.getRecipientInfos(bodyPart);
        RecipientInformation recipientInfo = recipientsInfo.get(recId);

        if (recipientInfo == null)
        {
            throw new SMimeException(null, E.t("Contenu encrypté invalide"));
        }

        JceKeyTransRecipient recipient = new JceKeyTransEnvelopedRecipient(privateKey).setProvider(SECURITY_PROVIDER);

        ByteArrayInputStream ins = new ByteArrayInputStream(recipientInfo.getContent(recipient));
        MimeBodyPart decryptedPart = new MimeBodyPart(ins);
        return new SMimeMessage(decryptedPart, this);
    }
    catch (Exception e)
    {
        throw new SMimeException(null, E.t("Impossible de décrypter le message"), e);
    }
}

[dghgit]

Thanks for the PR. This is now merged with minor changes and also available on https://www.bouncycastle.org/betas

[bukka]

Thanks @dghgit ! I will remember to update the code style in my IDE for the future contributions. Isn't there by any chance any code style scheme available? I use IntelliJ so it can use either IntelliJ IDEA code style XML or Eclipse XML Profile format. Alternatively I will just update it to match your changes.