S/MIME encryption proof of concept

app/src/main/java/eu/faircode/email/FragmentCompose.java

@@ -1969,8 +1969,6 @@ public class FragmentCompose extends FragmentBase {
 
                     db.attachment().setDownloaded(sattachment.id, file.length());
                 } else if (EntityMessage.SMIME_SIGNENCRYPT.equals(draft.encrypt)) {
-                    if (true)
-                        throw new UnsupportedOperationException("Not implemented yet");
                     // TODO: sign
                     if (draft.to == null || draft.to.length != 1)
                         throw new IllegalArgumentException(getString(R.string.title_to_missing));
@@ -1992,12 +1990,12 @@ public class FragmentCompose extends FragmentBase {
                     bpContent.writeTo(bos);
                     CMSTypedData msg = new CMSProcessableByteArray(bos.toByteArray());
 
-                    OutputEncryptor encryptor = new JceCMSContentEncryptorBuilder(CMSAlgorithm.AES256_CBC)
+                    OutputEncryptor encryptor = new JceCMSContentEncryptorBuilder(CMSAlgorithm.AES128_CBC)
                             .build();
                     CMSEnvelopedData cmsEnvelopedData = cmsEnvelopedDataGenerator
                             .generate(msg, encryptor);
 
-                    byte[] encryptedData = cmsEnvelopedData.toASN1Structure().getEncoded();
+                    byte[] encryptedData = cmsEnvelopedData/*.toASN1Structure()*/.getEncoded();
 
                     EntityAttachment attachment = new EntityAttachment();
                     attachment.message = draft.id;

app/src/main/java/eu/faircode/email/FragmentMessages.java

@@ -124,7 +124,6 @@ import org.bouncycastle.cms.SignerInformationStore;
 import org.bouncycastle.cms.jcajce.JcaSimpleSignerInfoVerifierBuilder;
 import org.bouncycastle.cms.jcajce.JceKeyTransEnvelopedRecipient;
 import org.bouncycastle.cms.jcajce.JceKeyTransRecipient;
-import org.bouncycastle.jce.provider.BouncyCastleProvider;
 import org.bouncycastle.util.Store;
 import org.jsoup.nodes.Document;
 import org.jsoup.nodes.Element;
@@ -4436,8 +4435,10 @@ public class FragmentMessages extends FragmentBase implements SharedPreferences.
                         throw new IllegalArgumentException("Encrypted message missing");
 
                     // Build enveloped data
-                    FileInputStream fis = new FileInputStream(input);
-                    CMSEnvelopedData envelopedData = new CMSEnvelopedData(fis);
+                    CMSEnvelopedData envelopedData;
+                    try (FileInputStream fis = new FileInputStream(input)) {
+                        envelopedData = new CMSEnvelopedData(fis);
+                    }
 
                     // Decrypt message
                     Collection<RecipientInformation> recipients = envelopedData.getRecipientInfos().getRecipients();

app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -23,7 +23,6 @@ import android.content.Context;
 import android.net.MailTo;
 import android.net.Uri;
 import android.text.TextUtils;
-import android.util.Base64;
 
 import com.sun.mail.util.FolderClosedIOException;
 import com.sun.mail.util.MessageRemovedIOException;
@@ -33,6 +32,7 @@ import org.jsoup.nodes.Document;
 import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
 import java.io.BufferedReader;
+import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
 import java.io.FileInputStream;
@@ -58,6 +58,7 @@ import java.util.TimeZone;
 import java.util.regex.Pattern;
 
 import javax.activation.DataHandler;
+import javax.activation.DataSource;
 import javax.activation.FileDataSource;
 import javax.activation.FileTypeMap;
 import javax.mail.Address;
@@ -392,7 +393,27 @@ public class MessageHelper {
                 ct.setParameter("smime-type", "enveloped-data");
                 imessage.setDisposition(Part.ATTACHMENT);
                 imessage.setFileName(attachment.name);
-                imessage.setContent(Base64.encodeToString(encryptedData, Base64.DEFAULT), ct.toString());
+                imessage.setDataHandler(new DataHandler(new DataSource() {
+                    @Override
+                    public InputStream getInputStream() throws IOException {
+                        return new ByteArrayInputStream(encryptedData);
+                    }
+
+                    @Override
+                    public OutputStream getOutputStream() throws IOException {
+                        return null;
+                    }
+
+                    @Override
+                    public String getContentType() {
+                        return ct.toString();
+                    }
+
+                    @Override
+                    public String getName() {
+                        return null;
+                    }
+                }));
 
                 return imessage;
             }

gradle.properties

@@ -11,7 +11,7 @@
 # This option should only be used with decoupled projects. More details, visit
 # http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
 # org.gradle.parallel=true
-org.gradle.jvmargs=-Xmx512m
+org.gradle.jvmargs=-Xmx1024m
 org.gradle.warning.mode=all
 
 android.useAndroidX=true