Repo created

app/crypto-openpgp/build.gradle.kts

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+plugins {
+    id(ThunderbirdPlugins.Library.android)
+}
+
+dependencies {
+    implementation(projects.app.core)
+}
+
+android {
+    namespace = "com.fsck.k9.crypto.openpgp"
+}

app/crypto-openpgp/src/main/java/com/fsck/k9/crypto/openpgp/EncryptionDetector.java

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+package com.fsck.k9.crypto.openpgp;
+
+
+import androidx.annotation.NonNull;
+
+import com.fsck.k9.crypto.MessageCryptoStructureDetector;
+import com.fsck.k9.mail.Body;
+import com.fsck.k9.mail.BodyPart;
+import com.fsck.k9.mail.Message;
+import com.fsck.k9.mail.Multipart;
+import com.fsck.k9.mail.Part;
+import com.fsck.k9.message.extractors.TextPartFinder;
+
+import static com.fsck.k9.mail.internet.MimeUtility.isSameMimeType;
+
+
+//FIXME: Make this only detect OpenPGP messages. Move support for S/MIME messages to separate module.
+class EncryptionDetector {
+    private final TextPartFinder textPartFinder;
+
+
+    EncryptionDetector(TextPartFinder textPartFinder) {
+        this.textPartFinder = textPartFinder;
+    }
+
+    public boolean isEncrypted(@NonNull Message message) {
+        return isPgpMimeOrSMimeEncrypted(message) || containsInlinePgpEncryptedText(message);
+    }
+
+    private boolean isPgpMimeOrSMimeEncrypted(Message message) {
+        return containsPartWithMimeType(message, "multipart/encrypted", "application/pkcs7-mime");
+    }
+
+    private boolean containsInlinePgpEncryptedText(Message message) {
+        Part textPart = textPartFinder.findFirstTextPart(message);
+        return MessageCryptoStructureDetector.isPartPgpInlineEncrypted(textPart);
+    }
+
+    private boolean containsPartWithMimeType(Part part, String... wantedMimeTypes) {
+        String mimeType = part.getMimeType();
+        if (isMimeTypeAnyOf(mimeType, wantedMimeTypes)) {
+            return true;
+        }
+
+        Body body = part.getBody();
+        if (body instanceof Multipart) {
+            Multipart multipart = (Multipart) body;
+            for (BodyPart bodyPart : multipart.getBodyParts()) {
+                if (containsPartWithMimeType(bodyPart, wantedMimeTypes)) {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
+    private boolean isMimeTypeAnyOf(String mimeType, String... wantedMimeTypes) {
+        for (String wantedMimeType : wantedMimeTypes) {
+            if (isSameMimeType(mimeType, wantedMimeType)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}

app/crypto-openpgp/src/main/java/com/fsck/k9/crypto/openpgp/OpenPgpEncryptionExtractor.kt

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+package com.fsck.k9.crypto.openpgp
+
+import com.fsck.k9.crypto.EncryptionExtractor
+import com.fsck.k9.crypto.EncryptionResult
+import com.fsck.k9.mail.Message
+import com.fsck.k9.message.extractors.TextPartFinder
+
+class OpenPgpEncryptionExtractor internal constructor(
+    private val encryptionDetector: EncryptionDetector
+) : EncryptionExtractor {
+
+    override fun extractEncryption(message: Message): EncryptionResult? {
+        return if (encryptionDetector.isEncrypted(message)) {
+            EncryptionResult(ENCRYPTION_TYPE, 0)
+        } else {
+            null
+        }
+    }
+
+    companion object {
+        const val ENCRYPTION_TYPE = "openpgp"
+
+        @JvmStatic
+        fun newInstance(): OpenPgpEncryptionExtractor {
+            val textPartFinder = TextPartFinder()
+            val encryptionDetector = EncryptionDetector(textPartFinder)
+            return OpenPgpEncryptionExtractor(encryptionDetector)
+        }
+    }
+}

app/crypto-openpgp/src/test/java/com/fsck/k9/crypto/openpgp/EncryptionDetectorTest.java

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+package com.fsck.k9.crypto.openpgp;
+
+
+import com.fsck.k9.mail.Message;
+import com.fsck.k9.message.extractors.TextPartFinder;
+import org.junit.Before;
+import org.junit.Test;
+
+import static com.fsck.k9.crypto.openpgp.MessageCreationHelper.createMessage;
+import static com.fsck.k9.crypto.openpgp.MessageCreationHelper.createMultipartMessage;
+import static com.fsck.k9.crypto.openpgp.MessageCreationHelper.createPart;
+import static com.fsck.k9.crypto.openpgp.MessageCreationHelper.createTextMessage;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+
+public class EncryptionDetectorTest {
+    private static final String CRLF = "\r\n";
+
+
+    private EncryptionDetector encryptionDetector;
+
+
+    @Before
+    public void setUp() {
+        encryptionDetector = new EncryptionDetector(new TextPartFinder());
+    }
+
+    @Test
+    public void isEncrypted_withTextPlain_shouldReturnFalse() {
+        Message message = createTextMessage("text/plain", "plain text");
+
+        boolean encrypted = encryptionDetector.isEncrypted(message);
+
+        assertFalse(encrypted);
+    }
+
+    @Test
+    public void isEncrypted_withMultipartEncrypted_shouldReturnTrue() throws Exception {
+        Message message = createMultipartMessage("multipart/encrypted",
+                createPart("application/octet-stream"), createPart("application/octet-stream"));
+
+        boolean encrypted = encryptionDetector.isEncrypted(message);
+
+        assertTrue(encrypted);
+    }
+
+    @Test
+    public void isEncrypted_withSMimePart_shouldReturnTrue() {
+        Message message = createMessage("application/pkcs7-mime");
+
+        boolean encrypted = encryptionDetector.isEncrypted(message);
+
+        assertTrue(encrypted);
+    }
+
+    @Test
+    public void isEncrypted_withMultipartMixedContainingSMimePart_shouldReturnTrue() throws Exception {
+        Message message = createMultipartMessage("multipart/mixed",
+                createPart("application/pkcs7-mime"), createPart("text/plain"));
+
+        boolean encrypted = encryptionDetector.isEncrypted(message);
+
+        assertTrue(encrypted);
+    }
+
+    @Test
+    public void isEncrypted_withInlinePgp_shouldReturnTrue() {
+        Message message = createTextMessage("text/plain", "" +
+                "-----BEGIN PGP MESSAGE-----" + CRLF +
+                "some encrypted stuff here" + CRLF +
+                "-----END PGP MESSAGE-----");
+
+        boolean encrypted = encryptionDetector.isEncrypted(message);
+
+        assertTrue(encrypted);
+    }
+
+    @Test
+    public void isEncrypted_withPlainTextAndPreambleWithInlinePgp_shouldReturnFalse() {
+        Message message = createTextMessage("text/plain", "" +
+                "preamble" + CRLF +
+                "-----BEGIN PGP MESSAGE-----" + CRLF +
+                "some encrypted stuff here" + CRLF +
+                "-----END PGP MESSAGE-----" + CRLF +
+                "epilogue");
+
+        boolean encrypted = encryptionDetector.isEncrypted(message);
+
+        assertFalse(encrypted);
+    }
+
+    @Test
+    public void isEncrypted_withQuotedInlinePgp_shouldReturnFalse() {
+        Message message = createTextMessage("text/plain", "" +
+                "good talk!" + CRLF +
+                CRLF +
+                "> -----BEGIN PGP MESSAGE-----" + CRLF +
+                "> some encrypted stuff here" + CRLF +
+                "> -----END PGP MESSAGE-----" + CRLF +
+                CRLF +
+                "-- " + CRLF +
+                "my signature");
+
+        boolean encrypted = encryptionDetector.isEncrypted(message);
+
+        assertFalse(encrypted);
+    }
+}

app/crypto-openpgp/src/test/java/com/fsck/k9/crypto/openpgp/MessageCreationHelper.java

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+package com.fsck.k9.crypto.openpgp;
+
+
+import com.fsck.k9.mail.Body;
+import com.fsck.k9.mail.BodyPart;
+import com.fsck.k9.mail.Message;
+import com.fsck.k9.mail.MessagingException;
+import com.fsck.k9.mail.internet.MimeBodyPart;
+import com.fsck.k9.mail.internet.MimeHeader;
+import com.fsck.k9.mail.internet.MimeMessage;
+import com.fsck.k9.mail.internet.MimeMultipart;
+import com.fsck.k9.mail.internet.TextBody;
+import com.fsck.k9.mailstore.BinaryMemoryBody;
+
+
+public class MessageCreationHelper {
+    public static BodyPart createPart(String mimeType) throws MessagingException {
+        BinaryMemoryBody body = new BinaryMemoryBody(new byte[0], "utf-8");
+        return new MimeBodyPart(body, mimeType);
+    }
+
+    public static Message createTextMessage(String mimeType, String text) {
+        TextBody body = new TextBody(text);
+        return createMessage(mimeType, body);
+    }
+
+    public static Message createMultipartMessage(String mimeType, BodyPart... parts) {
+        MimeMultipart body = createMultipartBody(mimeType, parts);
+        return createMessage(mimeType, body);
+    }
+
+    public static Message createMessage(String mimeType) {
+        return createMessage(mimeType, null);
+    }
+
+    private static Message createMessage(String mimeType, Body body) {
+        MimeMessage message = new MimeMessage();
+        message.setBody(body);
+        message.setHeader(MimeHeader.HEADER_CONTENT_TYPE, mimeType);
+
+        return message;
+    }
+
+    private static MimeMultipart createMultipartBody(String mimeType, BodyPart[] parts) {
+        MimeMultipart multipart = new MimeMultipart(mimeType, "boundary");
+        for (BodyPart part : parts) {
+            multipart.addBodyPart(part);
+        }
+        return multipart;
+    }
+}