Add support for XEP-XXXX: OMEMO Media Sharing

Author: vanitasvitae

documentation/extensions/index.md

@@ -113,6 +113,7 @@ Unofficial XMPP Extensions
 | Name                                        | XEP                                                    | Version   | Description |
 |---------------------------------------------|--------------------------------------------------------|-----------|----------------------------------------------------------------------------------------------------------|
 | [Multi-User Chat Light](muclight.md)        | [XEP-xxxx](https://mongooseim.readthedocs.io/en/latest/open-extensions/xeps/xep-muc-light.html) | n/a     | Multi-User Chats for mobile XMPP applications and specific environment. |
+| OMEMO Media Sharing                         | [XEP-XXXX](https://xmpp.org/extensions/inbox/omemo-media-sharing.html) | 0.0.1     | Share files via HTTP File Upload in an encrypted fashion. |
 | Google GCM JSON payload                     | n/a                                                    | n/a       | Semantically the same as XEP-0335: JSON Containers. |
 
 Legacy Smack Extensions and currently supported XEPs of smack-legacy

smack-core/src/main/java/org/jivesoftware/smack/util/RandomUtils.java

@@ -0,0 +1,36 @@
+/**
+ *
+ * Copyright © 2019 Paul Schaub
+ *
+ * Licensed 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.jivesoftware.smack.util;
+
+import java.security.SecureRandom;
+
+public class RandomUtils {
+
+    private static final SecureRandom SECURE_RANDOM = new SecureRandom();
+
+    /**
+     * Generate a securely random byte array.
+     *
+     * @param len length of the byte array
+     * @return byte array
+     */
+    public static byte[] secureRandomBytes(int len) {
+        byte[] bytes = new byte[len];
+        SECURE_RANDOM.nextBytes(bytes);
+        return bytes;
+    }
+}

smack-core/src/main/java/org/jivesoftware/smack/util/StringUtils.java

@@ -261,6 +261,24 @@ public static String encodeHex(byte[] bytes) {
         return new String(hexChars);
     }
 
+    /**
+     * Convert a hexadecimal String to bytes.
+     *
+     * Source: https://stackoverflow.com/a/140861/11150851
+     *
+     * @param s hex string
+     * @return byte array
+     */
+    public static byte[] hexStringToByteArray(String s) {
+        int len = s.length();
+        byte[] data = new byte[len / 2];
+        for (int i = 0; i < len; i += 2) {
+            data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
+                    + Character.digit(s.charAt(i + 1), 16));
+        }
+        return data;
+    }
+
     public static byte[] toUtf8Bytes(String string) {
         return string.getBytes(StandardCharsets.UTF_8);
     }

smack-experimental/src/main/java/org/jivesoftware/smackx/httpfileupload/HttpFileUploadManager.java

@@ -21,16 +21,22 @@
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.io.InputStream;
 import java.io.OutputStream;
 import java.net.HttpURLConnection;
 import java.net.URL;
+import java.security.InvalidAlgorithmParameterException;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.WeakHashMap;
 import java.util.logging.Level;
 import java.util.logging.Logger;
-
+import javax.crypto.Cipher;
+import javax.crypto.CipherInputStream;
+import javax.crypto.NoSuchPaddingException;
 import javax.net.ssl.HttpsURLConnection;
 import javax.net.ssl.SSLContext;
 import javax.net.ssl.SSLSocketFactory;
@@ -43,24 +49,28 @@
 import org.jivesoftware.smack.XMPPConnection;
 import org.jivesoftware.smack.XMPPConnectionRegistry;
 import org.jivesoftware.smack.XMPPException;
-
 import org.jivesoftware.smackx.disco.ServiceDiscoveryManager;
 import org.jivesoftware.smackx.disco.packet.DiscoverInfo;
 import org.jivesoftware.smackx.httpfileupload.UploadService.Version;
 import org.jivesoftware.smackx.httpfileupload.element.Slot;
 import org.jivesoftware.smackx.httpfileupload.element.SlotRequest;
 import org.jivesoftware.smackx.httpfileupload.element.SlotRequest_V0_2;
+import org.jivesoftware.smackx.omemo_media_sharing.AesgcmUrl;
+import org.jivesoftware.smackx.omemo_media_sharing.OmemoMediaSharingUtils;
 import org.jivesoftware.smackx.xdata.FormField;
 import org.jivesoftware.smackx.xdata.packet.DataForm;
 
 import org.jxmpp.jid.DomainBareJid;
 
 /**
  * A manager for XEP-0363: HTTP File Upload.
+ * This manager is also capable of XEP-XXXX: OMEMO Media Sharing.
  *
  * @author Grigory Fedorov
  * @author Florian Schmaus
+ * @author Paul Schaub
  * @see <a href="http://xmpp.org/extensions/xep-0363.html">XEP-0363: HTTP File Upload</a>
+ * @see <a href="https://xmpp.org/extensions/inbox/omemo-media-sharing.html">XEP-XXXX: OMEMO Media Sharing</a>
  */
 public final class HttpFileUploadManager extends Manager {
 
@@ -245,7 +255,7 @@ public URL uploadFile(File file) throws InterruptedException, XMPPException.XMPP
      * Note that this is a synchronous call -- Smack must wait for the server response.
      *
      * @param file file to be uploaded
-     * @param listener upload progress listener of null
+     * @param listener upload progress listener or null
      * @return public URL for sharing uploaded file
      *
      * @throws InterruptedException
@@ -265,6 +275,74 @@ public URL uploadFile(File file, UploadProgressListener listener) throws Interru
         return slot.getGetUrl();
     }
 
+    /**
+     * Upload a file encrypted using the scheme described in OMEMO Media Sharing.
+     * The file is being encrypted using a random 256 bit AES key in Galois Counter Mode using a random 16 byte IV and
+     * then uploaded to the server.
+     * The URL that is returned has a modified scheme (aesgcm:// instead of https://) and has the IV and key attached
+     * as ref part.
+     *
+     * Note: The URL contains the used key and IV in plain text. Keep in mind to only share this URL though a secured
+     * channel (i.e. end-to-end encrypted message), as anybody who can read the URL can also decrypt the file.
+     *
+     * Note: This method uses a IV of length 16 instead of 12. Although not specified in the ProtoXEP, 16 byte IVs are
+     * currently used by most implementations. This implementation also supports 12 byte IVs when decrypting.
+     *
+     * @param file file
+     * @return AESGCM URL which contains the key and IV of the encrypted file.
+     *
+     * @see <a href="https://xmpp.org/extensions/inbox/omemo-media-sharing.html">XEP-XXXX: OMEMO Media Sharing</a>
+     */
+    public AesgcmUrl uploadFileEncrypted(File file) throws InterruptedException, IOException,
+            XMPPException.XMPPErrorException, SmackException, InvalidAlgorithmParameterException,
+            NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException {
+        return uploadFileEncrypted(file, null);
+    }
+    /**
+     * Upload a file encrypted using the scheme described in OMEMO Media Sharing.
+     * The file is being encrypted using a random 256 bit AES key in Galois Counter Mode using a random 16 byte IV and
+     * then uploaded to the server.
+     * The URL that is returned has a modified scheme (aesgcm:// instead of https://) and has the IV and key attached
+     * as ref part.
+     *
+     * Note: The URL contains the used key and IV in plain text. Keep in mind to only share this URL though a secured
+     * channel (i.e. end-to-end encrypted message), as anybody who can read the URL can also decrypt the file.
+     *
+     * Note: This method uses a IV of length 16 instead of 12. Although not specified in the ProtoXEP, 16 byte IVs are
+     * currently used by most implementations. This implementation also supports 12 byte IVs when decrypting.
+     *
+     * @param file file
+     * @param listener progress listener or null
+     * @return AESGCM URL which contains the key and IV of the encrypted file.
+     *
+     * @see <a href="https://xmpp.org/extensions/inbox/omemo-media-sharing.html">XEP-XXXX: OMEMO Media Sharing</a>
+     */
+    public AesgcmUrl uploadFileEncrypted(File file, UploadProgressListener listener) throws IOException,
+            InterruptedException, XMPPException.XMPPErrorException, SmackException, NoSuchPaddingException,
+            NoSuchAlgorithmException, InvalidAlgorithmParameterException, InvalidKeyException {
+        if (!file.isFile()) {
+            throw new FileNotFoundException("The path " + file.getAbsolutePath() + " is not a file");
+        }
+
+        // The encrypted file will contain an extra block with the AEAD MAC.
+        long cipherFileLength = file.length() + 16;
+
+        final Slot slot = requestSlot(file.getName(), cipherFileLength, "application/octet-stream");
+        URL slotUrl = slot.getGetUrl();
+
+        // fresh AES key + iv
+        byte[] key = OmemoMediaSharingUtils.generateRandomKey();
+        byte[] iv = OmemoMediaSharingUtils.generateRandomIV();
+        Cipher cipher = OmemoMediaSharingUtils.encryptionCipherFrom(key, iv);
+
+        FileInputStream fis = new FileInputStream(file);
+        // encrypt the file on the fly - encryption actually happens below in uploadFile()
+        CipherInputStream cis = new CipherInputStream(fis, cipher);
+
+        uploadFile(cis, cipherFileLength, slot, listener);
+
+        return new AesgcmUrl(slotUrl, key, iv);
+    }
 
     /**
      * Request a new upload slot from default upload service (if discovered). When you get slot you should upload file
@@ -391,10 +469,13 @@ private void uploadFile(final File file, final Slot slot, UploadProgressListener
         if (fileSize >= Integer.MAX_VALUE) {
             throw new IllegalArgumentException("File size " + fileSize + " must be less than " + Integer.MAX_VALUE);
         }
-        final int fileSizeInt = (int) fileSize;
 
         // Construct the FileInputStream first to make sure we can actually read the file.
         final FileInputStream fis = new FileInputStream(file);
+        uploadFile(fis, fileSize, slot, listener);
+    }
+
+    private void uploadFile(final InputStream fis, long fileSize, final Slot slot, UploadProgressListener listener) throws IOException {
 
         final URL putUrl = slot.getPutUrl();
 
@@ -404,7 +485,7 @@ private void uploadFile(final File file, final Slot slot, UploadProgressListener
         urlConnection.setUseCaches(false);
         urlConnection.setDoOutput(true);
         // TODO Change to using fileSize once Smack's minimum Android API level is 19 or higher.
-        urlConnection.setFixedLengthStreamingMode(fileSizeInt);
+        urlConnection.setFixedLengthStreamingMode((int) fileSize);
         urlConnection.setRequestProperty("Content-Type", "application/octet-stream;");
         for (Entry<String, String> header : slot.getHeaders().entrySet()) {
             urlConnection.setRequestProperty(header.getKey(), header.getValue());

smack-experimental/src/main/java/org/jivesoftware/smackx/omemo_media_sharing/AesgcmUrl.java

@@ -0,0 +1,161 @@
+/**
+ *
+ * Copyright © 2019 Paul Schaub
+ *
+ * Licensed 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.jivesoftware.smackx.omemo_media_sharing;
+
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.security.InvalidAlgorithmParameterException;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import javax.crypto.Cipher;
+import javax.crypto.NoSuchPaddingException;
+
+import org.jivesoftware.smack.util.Objects;
+import org.jivesoftware.smack.util.StringUtils;
+import org.jivesoftware.smackx.httpfileupload.element.Slot;
+
+/**
+ * This class represents a aesgcm URL as described in XEP-XXXX: OMEMO Media Sharing.
+ * As the builtin {@link URL} class cannot handle the aesgcm protocol identifier, this class
+ * is used as a utility class that bundles together a {@link URL}, key and IV.
+ *
+ * @see <a href="https://xmpp.org/extensions/inbox/omemo-media-sharing.html">XEP-XXXX: OMEMO Media Sharing</a>
+ */
+public class AesgcmUrl {
+
+    public static final String PROTOCOL = "aesgcm";
+
+    private final URL httpsUrl;
+    private final byte[] keyBytes;
+    private final byte[] ivBytes;
+
+    /**
+     * Private constructor that constructs the {@link AesgcmUrl} from a normal https {@link URL}, a key and iv.
+     *
+     * @param httpsUrl normal https url as given by the {@link Slot}.
+     * @param key byte array of an encoded 256 bit aes key
+     * @param iv 16 or 12 byte initialization vector
+     */
+    public AesgcmUrl(URL httpsUrl, byte[] key, byte[] iv) {
+        this.httpsUrl = Objects.requireNonNull(httpsUrl);
+        this.keyBytes = Objects.requireNonNull(key);
+        this.ivBytes = Objects.requireNonNull(iv);
+    }
+
+    /**
+     * Parse a {@link AesgcmUrl} from a {@link String}.
+     * The parsed object will provide a normal {@link URL} under which the offered file can be downloaded,
+     * as well as a {@link Cipher} that can be used to decrypt it.
+     *
+     * @param aesgcmUrlString aesgcm URL as a {@link String}
+     */
+    public AesgcmUrl(String aesgcmUrlString) {
+        if (!aesgcmUrlString.startsWith(PROTOCOL)) {
+            throw new IllegalArgumentException("Provided String does not resemble a aesgcm URL.");
+        }
+
+        // Convert aesgcm Url to https URL
+        this.httpsUrl = extractHttpsUrl(aesgcmUrlString);
+
+        // Extract IV and Key
+        byte[][] ivAndKey = extractIVAndKey(aesgcmUrlString);
+        this.ivBytes = ivAndKey[0];
+        this.keyBytes = ivAndKey[1];
+    }
+
+    /**
+     * Return a https {@link URL} under which the file can be downloaded.
+     *
+     * @return https URL
+     */
+    public URL getDownloadUrl() {
+        return httpsUrl;
+    }
+
+    /**
+     * Returns the {@link String} representation of this aesgcm URL.
+     *
+     * @return aesgcm URL with key and IV.
+     */
+    public String getAesgcmUrl() {
+        String aesgcmUrl = httpsUrl.toString().replaceFirst(httpsUrl.getProtocol(), PROTOCOL);
+        return aesgcmUrl + "#" + StringUtils.encodeHex(ivBytes) + StringUtils.encodeHex(keyBytes);
+    }
+
+    /**
+     * Returns a {@link Cipher} in decryption mode, which can be used to decrypt the offered file.
+     *
+     * @return cipher
+     *
+     * @throws NoSuchPaddingException if the JVM cannot provide the specified cipher mode
+     * @throws NoSuchAlgorithmException if the JVM cannot provide the specified cipher mode
+     * @throws InvalidAlgorithmParameterException if the JVM cannot provide the specified cipher
+     *                                            (eg. if no BC provider is added)
+     * @throws InvalidKeyException if the provided key is invalid
+     */
+    public Cipher getDecryptionCipher() throws NoSuchPaddingException, NoSuchAlgorithmException,
+            InvalidAlgorithmParameterException, InvalidKeyException {
+        return OmemoMediaSharingUtils.decryptionCipherFrom(keyBytes, ivBytes);
+    }
+
+    private static URL extractHttpsUrl(String aesgcmUrlString) {
+        // aesgcm -> https
+        String httpsUrlString = aesgcmUrlString.replaceFirst(PROTOCOL, "https");
+        // remove #ref
+        httpsUrlString = httpsUrlString.substring(0, httpsUrlString.indexOf("#"));
+
+        try {
+            return new URL(httpsUrlString);
+        } catch (MalformedURLException e) {
+            throw new AssertionError("Failed to convert aesgcm URL to https URL: '" + aesgcmUrlString + "'", e);
+        }
+    }
+
+    private static byte[][] extractIVAndKey(String aesgcmUrlString) {
+        int startOfRef = aesgcmUrlString.lastIndexOf("#");
+        if (startOfRef == -1) {
+            throw new IllegalArgumentException("The provided aesgcm Url does not have a ref part which is " +
+                    "supposed to contain the encryption key for file encryption.");
+        }
+
+        String ref = aesgcmUrlString.substring(startOfRef + 1);
+        byte[] refBytes = StringUtils.hexStringToByteArray(ref);
+
+        byte[] key = new byte[32];
+        byte[] iv;
+        int ivLen;
+        // determine the length of the initialization vector part
+        switch (refBytes.length) {
+            // 32 bytes key + 16 bytes IV
+            case 48:
+                ivLen = 16;
+                break;
+
+            // 32 bytes key + 12 bytes IV
+            case 44:
+                ivLen = 12;
+                break;
+            default:
+                throw new IllegalArgumentException("Provided URL has an invalid ref tag (" + ref.length() + "): '" + ref + "'");
+        }
+        iv = new byte[ivLen];
+        System.arraycopy(refBytes, 0, iv, 0, ivLen);
+        System.arraycopy(refBytes, ivLen, key, 0, 32);
+
+        return new byte[][] {iv, key};
+    }
+}