Implement e2e media decryption

Add MediaDecryption class to decrypt images, videos, audio and documents

build.gradle

@@ -28,6 +28,9 @@ dependencies {
 	// https://mvnrepository.com/artifact/commons-codec/commons-codec
 	compile group: 'commons-codec', name: 'commons-codec', version: '1.14'
 
+	// https://mvnrepository.com/artifact/commons-io/commons-io
+	compile group: 'commons-io', name: 'commons-io', version: '2.7'
+
 	// https://mvnrepository.com/artifact/org.whispersystems/curve25519-java
 	compile group: 'org.whispersystems', name: 'curve25519-java', version: '0.5.0'
 

src/main/java/icu/jnet/whatsjava/Main.java

@@ -3,15 +3,10 @@
 import java.awt.image.BufferedImage;
 import java.io.File;
 import java.io.IOException;
-import java.util.Base64;
 
 import javax.imageio.ImageIO;
 
-import icu.jnet.whatsjava.helper.Utils;
 import icu.jnet.whatsjava.web.WebChat;
-import icu.jnet.whatsjava.web.WebConversationMessage;
-import icu.jnet.whatsjava.web.WebImageMessage;
-import icu.jnet.whatsjava.web.WebVideoMessage;
 
 public class Main {
 

src/main/java/icu/jnet/whatsjava/constants/ExpectedResponse.java

@@ -4,17 +4,11 @@ public class ExpectedResponse {
 
 	// Excepted message type for the next message of the backend
 
-	public static final byte LOGIN = 0;
-
-	public static final byte NEW_SERVER_ID = 1;
-
-	public static final byte SCAN_QR_CODE = 2;
-
-	public static final byte RESTORE_SESSION = 3;
-
-	public static final byte RESOLVE_CHALLENGE = 4;
-
-	public static final byte LOGGING_OUT = 5;
-
-	public static final byte MESSAGE_GENERIC = 6;
+	public static final byte LOGIN = 0,
+			NEW_SERVER_ID = 1,
+			SCAN_QR_CODE = 2,
+			RESTORE_SESSION = 3,
+			RESOLVE_CHALLENGE = 4,
+			LOGGING_OUT = 5,
+			MESSAGE_GENERIC = 6;
 }

src/main/java/icu/jnet/whatsjava/encryption/AES.java

@@ -31,7 +31,22 @@ static byte[] decrypt(byte[] encrypted, byte[] secretKey) {
 	    return null;
 	}
 
-	// Encrypt it using AES and encKey
+	// Used for E2E media decryption in the MediaEncryption class
+	static byte[] decrypt(byte[] encrypted, byte[] secretKey, byte[] iv) {
+	    try 
+	    {
+	    	Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING"); // PKCS5PADDING required
+	    	SecretKeySpec secretKeySpec = new SecretKeySpec(secretKey, "AES");
+	    	cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, new IvParameterSpec(iv));
+
+	    	return cipher.doFinal(encrypted);
+	    } catch (Exception e) {
+	        System.out.println("Error while decrypting: " + e.toString());
+	    }
+	    return null;
+	}
+
+	// Encrypt using AES and encKey
 	static byte[] encrypt(byte[] decrypted, byte[] encKey) {
 	    try 
 	    {

src/main/java/icu/jnet/whatsjava/encryption/BinaryDecoder.java

@@ -279,26 +279,26 @@ private String readNode() {
 
 				try {
 					switch(tag) {
-						// "message" message
+						// Conversation messages
 						case BinaryConstants.Tags.BINARY_8:
 							byte[] bin8 = readBytes(readByte() & 0xff);
 							base64Decoded = Base64.getEncoder().encodeToString(
 									WebMessageInfo.parseFrom(bin8).toByteArray());
+
 							break;
-						// video & image message
+						// Image, video, extended and rarely conversation messages
 						case BinaryConstants.Tags.BINARY_20:
 							byte[] bin20 = readBytes(readInt20());
-
 							base64Decoded = Base64.getEncoder().encodeToString(
 									WebMessageInfo.parseFrom(bin20).toByteArray());
+
 							break;
 						// ?
 						case BinaryConstants.Tags.BINARY_32:
 							byte[] bin32 = readBytes(readInt(4, false));
-
 							base64Decoded = Base64.getEncoder().encodeToString(
 									WebMessageInfo.parseFrom(bin32).toByteArray());
-
+							
 							break;
 						default:
 							base64Decoded = readString(tag);

src/main/java/icu/jnet/whatsjava/encryption/BinaryEncryption.java

@@ -9,6 +9,11 @@
 
 public class BinaryEncryption {
 
+	/*
+	 * Encrypt and decrypt binary messages, but no E2E media
+	 * 
+	 */
+
 	public static byte[] decrypt(byte[] message, EncryptionKeyPair keyPair) throws DecoderException {
 		// Encode byte array to hex char
 		String hexMessage = Hex.encodeHexString(message, true);

src/main/java/icu/jnet/whatsjava/encryption/EncryptionKeys.java

@@ -6,7 +6,6 @@
 
 import org.whispersystems.curve25519.Curve25519;
 
-import at.favre.lib.crypto.HKDF;
 import icu.jnet.whatsjava.helper.Utils;
 
 public class EncryptionKeys {
@@ -25,7 +24,7 @@ public static EncryptionKeyPair generate(String base64Secret, byte[] privateKey)
 		byte[] sharedSecret = Curve25519.getInstance(Curve25519.BEST)
 				.calculateAgreement(publicKey, privateKey);
 		// Expand the shared key to 80 bytes using HKDF
-		byte[] sharedSecretExpanded = expandUsingHKDF(sharedSecret, 80);
+		byte[] sharedSecretExpanded = Utils.expandUsingHKDF(sharedSecret, 80, null);
 
 		// Validate data by HMAC
 		boolean valid = hmacValidate(sharedSecretExpanded, secret);
@@ -61,11 +60,6 @@ public static EncryptionKeyPair generate(String base64Secret, byte[] privateKey)
 		return null;
 	}
 
-	private static byte[] expandUsingHKDF(byte[] key, int length) {
-		byte[] pseudoRandomKey = HKDF.fromHmacSha256().extract(null, key);
-		return HKDF.fromHmacSha256().expand(pseudoRandomKey, null, length);
-	}
-
 	private static boolean hmacValidate(byte[] sharedSecretExpanded, byte[] secret) {
 		byte[] hmacValidationKey = Arrays.copyOfRange(sharedSecretExpanded, 32, 64);
 		byte[] hmacSecretA = Arrays.copyOfRange(secret, 0, 32);

src/main/java/icu/jnet/whatsjava/encryption/MediaEncryption.java

@@ -0,0 +1,52 @@
+package icu.jnet.whatsjava.encryption;
+
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+
+import icu.jnet.whatsjava.helper.Utils;
+
+public class MediaEncryption {
+
+	/*
+	 * Decrypt E2E media
+	 * 
+	 */
+
+	// Depending on the media type a different info parameter is used for the HKDF function
+	public static String MEDIA_TYPE_IMAGE = "WhatsApp Image Keys",
+			MEDIA_TYPE_VIDEO = "WhatsApp Video Keys",
+			MEDIA_TYPE_AUDIO = "WhatsApp Audio Keys",
+			MEDIA_TYPE_DOCUMENT = "WhatsApp Document Keys";
+
+
+	public static byte[] decrypt(byte[] mediaKey, String url, String mediaType) {
+		// Expand mediaKey to 112 bytes and add mediaInfo
+		byte[] mediaKeyExpanded = Utils.expandUsingHKDF(mediaKey, 112, mediaType.getBytes());
+
+		byte[] iv = Arrays.copyOfRange(mediaKeyExpanded, 0, 16);
+		byte[] cipherKey = Arrays.copyOfRange(mediaKeyExpanded, 16, 48);
+		byte[] macKey = Arrays.copyOfRange(mediaKeyExpanded, 48, 80);
+		// refKey mediaKeyExpanded[80:112] not used
+
+		// Download encrypted media
+		byte[] encryptedMedia = Utils.urlToEncMedia(url);
+
+		if(encryptedMedia != null) {
+			byte[] file = Arrays.copyOfRange(encryptedMedia, 0, encryptedMedia.length - 10);
+			byte[] mac = Arrays.copyOfRange(encryptedMedia, encryptedMedia.length - 10, encryptedMedia.length);
+
+			// Hmac sign message
+			byte[] message = ByteBuffer.allocate(iv.length + file.length).put(iv).put(file).array();
+
+			// Validate macKey of mediaKeyExpanded with mac key of the encrypted media
+			byte[] hmacSign = Utils.signHMAC(macKey, message);
+
+			// Media validated
+			if(Arrays.equals(mac, Arrays.copyOfRange(hmacSign, 0, 10))) {
+				return AES.decrypt(file, cipherKey, iv);
+			}
+		}
+
+		return null;
+	}
+}

src/main/java/icu/jnet/whatsjava/helper/Utils.java

@@ -1,6 +1,12 @@
 package icu.jnet.whatsjava.helper;
 
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.net.URL;
 import java.nio.ByteBuffer;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.security.InvalidKeyException;
 import java.security.NoSuchAlgorithmException;
 import java.time.Instant;
@@ -9,9 +15,12 @@
 import javax.crypto.Mac;
 import javax.crypto.spec.SecretKeySpec;
 
+import org.apache.commons.io.FileUtils;
+
 import com.google.gson.JsonObject;
 import com.google.gson.JsonParser;
 
+import at.favre.lib.crypto.HKDF;
 import icu.jnet.whatsjava.constants.RequestType;
 import icu.jnet.whatsjava.encryption.BinaryEncoder;
 import icu.jnet.whatsjava.encryption.BinaryEncryption;
@@ -34,7 +43,7 @@ public static void waitMillis(long millis) {
 		}
 	}
 
-	/* Generate random byte array of specified length */
+	// Generate random byte array of specified length
 	public static byte[] randomBytes(int length) {
 		Random rand = new Random();
 		byte[] clientId = new byte[length];
@@ -43,26 +52,26 @@ public static byte[] randomBytes(int length) {
 		return clientId;
 	}
 
-	/* WhatsApp adds a tag to most of the json messages. That's why we need to remove it */
+	// WhatsApp adds a tag to most of the json messages. That's why we need to remove it
 	public static JsonObject encodeValidJson(String message, String splitStart) {
 		String rawSplittedMessage = message.replaceFirst(splitStart, "##").split("##")[1];
 		String rawMessage = rawSplittedMessage.substring(0, rawSplittedMessage.length() - 1);
 		return JsonParser.parseString(rawMessage).getAsJsonObject();
 	}
 
-	/* Default split char [,] */
+	// Default split char [,]
 	public static JsonObject encodeValidJson(String message) {
 		String raw = message.replaceFirst("[,]", "##").split("##")[1];
 		return JsonParser.parseString(raw).getAsJsonObject();
 	}
 
-	/* WhatsApp needs a message tag at the start of every Websocket request */
+	// WhatsApp needs a message tag at the start of every Websocket request
 	private static String getMessageTag() {
 		String messageTag = Instant.now().getEpochSecond() + ".--" + wsRequestCount++;
 		return messageTag;
 	}
 
-	/* WhatsApp binary message tags look different */
+	// WhatsApp binary message tags look different
 	private static String getBinaryMessageTag() {
 		if(binaryMessageTag.equals("")) {
 			binaryMessageTag = (new Random().nextInt(900) + 100) + "";
@@ -76,7 +85,7 @@ public static int getMessageCount() {
 		return wsRequestCount;
 	}
 
-	/* Create a new websocket json request string  */
+	// Create a new websocket json request string
 	public static String buildWebsocketJsonRequest(int requestType, String... content) {
 		String messageTag = getMessageTag();
 
@@ -108,7 +117,7 @@ public static String buildWebsocketJsonRequest(int requestType, String... conten
 		return request;
 	}
 
-	/* Create a new websocket binary request array  */
+	// Create a new websocket binary request array
 	public static byte[] buildWebsocketBinaryRequest(EncryptionKeyPair keyPair, String json, byte... waTags) {
 		String tag = null;
 
@@ -130,7 +139,13 @@ public static byte[] buildWebsocketBinaryRequest(EncryptionKeyPair keyPair, Stri
 				.put(messageTag).put(waTags).put(hmacSign).put(encrypted).array();
 	}
 
-	/* Implementation: https://github.com/danharper/hmac-examples */
+	// HLDF key expansion
+	public static byte[] expandUsingHKDF(byte[] key, int expandedLength, byte[] info) {
+		byte[] pseudoRandomKey = HKDF.fromHmacSha256().extract(null, key);
+		return HKDF.fromHmacSha256().expand(pseudoRandomKey, info, expandedLength);
+	}
+
+	// Implementation: https://github.com/danharper/hmac-examples
 	public static byte[] signHMAC(byte[] hmacValidationKey, byte[] hmacValidationMessage) {
 	    try {
 	    	Mac hasher = Mac.getInstance("HmacSHA256");
@@ -143,4 +158,28 @@ public static byte[] signHMAC(byte[] hmacValidationKey, byte[] hmacValidationMes
 		}
 		return null;
 	}
+
+	// Download encrypted media files
+	public static byte[] urlToEncMedia(String url) {
+		try {
+			// Create random temporary file
+			Path path = Files.createTempFile(null, ".enc");
+			File tmpFile = path.toFile();
+
+			byte[] encryptedMedia = null;
+			// Download encrypted file
+			try {
+				FileUtils.copyURLToFile(new URL(url), tmpFile);
+
+				// Convert file to byte array
+				encryptedMedia = Files.readAllBytes(path);
+			} catch(FileNotFoundException ex) {}
+
+			tmpFile.delete();
+			return encryptedMedia;
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+		return null;
+	}
 }

src/main/java/icu/jnet/whatsjava/web/WebImageMessage.java

@@ -1,10 +1,17 @@
 package icu.jnet.whatsjava.web;
 
+import icu.jnet.whatsjava.encryption.MediaEncryption;
 import icu.jnet.whatsjava.encryption.proto.ProtoBuf.ImageMessage;
 import icu.jnet.whatsjava.encryption.proto.ProtoBuf.WebMessageInfo;
 
 public class WebImageMessage extends WebMessage {
 
+	/*
+	 * E2E media image message
+	 * 
+	 */
+
+
 	private String mimetype, url, caption;
 	private byte[] fileSha256, mediaKey, jpegThumbnail;
 	private long fileLength;
@@ -51,6 +58,10 @@ public byte[] getJpegThumbnail() {
 		return jpegThumbnail;
 	}
 
+	public byte[] getJpegFullResolution() {
+		return MediaEncryption.decrypt(mediaKey, url, MediaEncryption.MEDIA_TYPE_IMAGE);
+	}
+
 	public long getFileLength() {
 		return fileLength;
 	}

src/main/java/icu/jnet/whatsjava/web/WebVideoMessage.java

@@ -1,11 +1,17 @@
 package icu.jnet.whatsjava.web;
 
+import icu.jnet.whatsjava.encryption.MediaEncryption;
 import icu.jnet.whatsjava.encryption.proto.ProtoBuf.VideoMessage;
 import icu.jnet.whatsjava.encryption.proto.ProtoBuf.WebMessageInfo;
 import icu.jnet.whatsjava.encryption.proto.ProtoBuf.VideoMessage.VIDEO_MESSAGE_ATTRIBUTION;
 
 public class WebVideoMessage extends WebMessage {
 
+	/*
+	 * E2E media video message
+	 * 
+	 */
+
 	private String mimetype, url;
 	private byte[] fileSha256, mediaKey, jpegThumbnail;
 	private long fileLength;
@@ -46,10 +52,14 @@ public byte[] getMediaKey() {
 		return mediaKey;
 	}
 
-	public byte[] getJpegThumbnail() {
+	public byte[] getMp4Thumbnail() {
 		return jpegThumbnail;
 	}
 
+	public byte[] getMp4FullResolution() {
+		return MediaEncryption.decrypt(mediaKey, url, MediaEncryption.MEDIA_TYPE_VIDEO);
+	}
+
 	public long getFileLength() {
 		return fileLength;
 	}