1 files changed, 249 insertions, 0 deletions
diff --git a/src/main/java/eu/siacs/conversations/crypto/axolotl/XmppAxolotlMessage.java b/src/main/java/eu/siacs/conversations/crypto/axolotl/XmppAxolotlMessage.java
new file mode 100644
index 00000000..cf950d6d
--- /dev/null
+++ b/src/main/java/eu/siacs/conversations/crypto/axolotl/XmppAxolotlMessage.java
@@ -0,0 +1,249 @@
+package eu.siacs.conversations.crypto.axolotl;
+
+import android.util.Base64;
+import android.util.Log;
+
+import java.security.InvalidAlgorithmParameterException;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.NoSuchProviderException;
+import java.security.SecureRandom;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import javax.crypto.BadPaddingException;
+import javax.crypto.Cipher;
+import javax.crypto.IllegalBlockSizeException;
+import javax.crypto.KeyGenerator;
+import javax.crypto.NoSuchPaddingException;
+import javax.crypto.SecretKey;
+import javax.crypto.spec.IvParameterSpec;
+import javax.crypto.spec.SecretKeySpec;
+
+import eu.siacs.conversations.Config;
+import eu.siacs.conversations.xml.Element;
+import eu.siacs.conversations.xmpp.jid.Jid;
+
+public class XmppAxolotlMessage {
+	public static final String CONTAINERTAG = "encrypted";
+	public static final String HEADER = "header";
+	public static final String SOURCEID = "sid";
+	public static final String KEYTAG = "key";
+	public static final String REMOTEID = "rid";
+	public static final String IVTAG = "iv";
+	public static final String PAYLOAD = "payload";
+
+	private static final String KEYTYPE = "AES";
+	private static final String CIPHERMODE = "AES/GCM/NoPadding";
+	private static final String PROVIDER = "BC";
+
+	private byte[] innerKey;
+	private byte[] ciphertext = null;
+	private byte[] iv = null;
+	private final Map<Integer, byte[]> keys;
+	private final Jid from;
+	private final int sourceDeviceId;
+
+	public static class XmppAxolotlPlaintextMessage {
+		private final String plaintext;
+		private final String fingerprint;
+
+		public XmppAxolotlPlaintextMessage(String plaintext, String fingerprint) {
+			this.plaintext = plaintext;
+			this.fingerprint = fingerprint;
+		}
+
+		public String getPlaintext() {
+			return plaintext;
+		}
+
+
+		public String getFingerprint() {
+			return fingerprint;
+		}
+	}
+
+	public static class XmppAxolotlKeyTransportMessage {
+		private final String fingerprint;
+		private final byte[] key;
+		private final byte[] iv;
+
+		public XmppAxolotlKeyTransportMessage(String fingerprint, byte[] key, byte[] iv) {
+			this.fingerprint = fingerprint;
+			this.key = key;
+			this.iv = iv;
+		}
+
+		public String getFingerprint() {
+			return fingerprint;
+		}
+
+		public byte[] getKey() {
+			return key;
+		}
+
+		public byte[] getIv() {
+			return iv;
+		}
+	}
+
+	private XmppAxolotlMessage(final Element axolotlMessage, final Jid from) throws IllegalArgumentException {
+		this.from = from;
+		Element header = axolotlMessage.findChild(HEADER);
+		this.sourceDeviceId = Integer.parseInt(header.getAttribute(SOURCEID));
+		List<Element> keyElements = header.getChildren();
+		this.keys = new HashMap<>(keyElements.size());
+		for (Element keyElement : keyElements) {
+			switch (keyElement.getName()) {
+				case KEYTAG:
+					try {
+						Integer recipientId = Integer.parseInt(keyElement.getAttribute(REMOTEID));
+						byte[] key = Base64.decode(keyElement.getContent(), Base64.DEFAULT);
+						this.keys.put(recipientId, key);
+					} catch (NumberFormatException e) {
+						throw new IllegalArgumentException(e);
+					}
+					break;
+				case IVTAG:
+					if (this.iv != null) {
+						throw new IllegalArgumentException("Duplicate iv entry");
+					}
+					iv = Base64.decode(keyElement.getContent(), Base64.DEFAULT);
+					break;
+				default:
+					Log.w(Config.LOGTAG, "Unexpected element in header: " + keyElement.toString());
+					break;
+			}
+		}
+		Element payloadElement = axolotlMessage.findChild(PAYLOAD);
+		if (payloadElement != null) {
+			ciphertext = Base64.decode(payloadElement.getContent(), Base64.DEFAULT);
+		}
+	}
+
+	public XmppAxolotlMessage(Jid from, int sourceDeviceId) {
+		this.from = from;
+		this.sourceDeviceId = sourceDeviceId;
+		this.keys = new HashMap<>();
+		this.iv = generateIv();
+		this.innerKey = generateKey();
+	}
+
+	public static XmppAxolotlMessage fromElement(Element element, Jid from) {
+		return new XmppAxolotlMessage(element, from);
+	}
+
+	private static byte[] generateKey() {
+		try {
+			KeyGenerator generator = KeyGenerator.getInstance(KEYTYPE);
+			generator.init(128);
+			return generator.generateKey().getEncoded();
+		} catch (NoSuchAlgorithmException e) {
+			Log.e(Config.LOGTAG, e.getMessage());
+			return null;
+		}
+	}
+
+	private static byte[] generateIv() {
+		SecureRandom random = new SecureRandom();
+		byte[] iv = new byte[16];
+		random.nextBytes(iv);
+		return iv;
+	}
+
+	public void encrypt(String plaintext) throws CryptoFailedException {
+		try {
+			SecretKey secretKey = new SecretKeySpec(innerKey, KEYTYPE);
+			IvParameterSpec ivSpec = new IvParameterSpec(iv);
+			Cipher cipher = Cipher.getInstance(CIPHERMODE, PROVIDER);
+			cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec);
+			this.innerKey = secretKey.getEncoded();
+			this.ciphertext = cipher.doFinal(plaintext.getBytes());
+		} catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException
+				| IllegalBlockSizeException | BadPaddingException | NoSuchProviderException
+				| InvalidAlgorithmParameterException e) {
+			throw new CryptoFailedException(e);
+		}
+	}
+
+	public Jid getFrom() {
+		return this.from;
+	}
+
+	public int getSenderDeviceId() {
+		return sourceDeviceId;
+	}
+
+	public byte[] getCiphertext() {
+		return ciphertext;
+	}
+
+	public void addDevice(XmppAxolotlSession session) {
+		byte[] key = session.processSending(innerKey);
+		if (key != null) {
+			keys.put(session.getRemoteAddress().getDeviceId(), key);
+		}
+	}
+
+	public byte[] getInnerKey() {
+		return innerKey;
+	}
+
+	public byte[] getIV() {
+		return this.iv;
+	}
+
+	public Element toElement() {
+		Element encryptionElement = new Element(CONTAINERTAG, AxolotlService.PEP_PREFIX);
+		Element headerElement = encryptionElement.addChild(HEADER);
+		headerElement.setAttribute(SOURCEID, sourceDeviceId);
+		for (Map.Entry<Integer, byte[]> keyEntry : keys.entrySet()) {
+			Element keyElement = new Element(KEYTAG);
+			keyElement.setAttribute(REMOTEID, keyEntry.getKey());
+			keyElement.setContent(Base64.encodeToString(keyEntry.getValue(), Base64.DEFAULT));
+			headerElement.addChild(keyElement);
+		}
+		headerElement.addChild(IVTAG).setContent(Base64.encodeToString(iv, Base64.DEFAULT));
+		if (ciphertext != null) {
+			Element payload = encryptionElement.addChild(PAYLOAD);
+			payload.setContent(Base64.encodeToString(ciphertext, Base64.DEFAULT));
+		}
+		return encryptionElement;
+	}
+
+	private byte[] unpackKey(XmppAxolotlSession session, Integer sourceDeviceId) {
+		byte[] encryptedKey = keys.get(sourceDeviceId);
+		return (encryptedKey != null) ? session.processReceiving(encryptedKey) : null;
+	}
+
+	public XmppAxolotlKeyTransportMessage getParameters(XmppAxolotlSession session, Integer sourceDeviceId) {
+		byte[] key = unpackKey(session, sourceDeviceId);
+		return (key != null)
+				? new XmppAxolotlKeyTransportMessage(session.getFingerprint(), key, getIV())
+				: null;
+	}
+
+	public XmppAxolotlPlaintextMessage decrypt(XmppAxolotlSession session, Integer sourceDeviceId) throws CryptoFailedException {
+		XmppAxolotlPlaintextMessage plaintextMessage = null;
+		byte[] key = unpackKey(session, sourceDeviceId);
+		if (key != null) {
+			try {
+				Cipher cipher = Cipher.getInstance(CIPHERMODE, PROVIDER);
+				SecretKeySpec keySpec = new SecretKeySpec(key, KEYTYPE);
+				IvParameterSpec ivSpec = new IvParameterSpec(iv);
+
+				cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
+
+				String plaintext = new String(cipher.doFinal(ciphertext));
+				plaintextMessage = new XmppAxolotlPlaintextMessage(plaintext, session.getFingerprint());
+
+			} catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException
+					| InvalidAlgorithmParameterException | IllegalBlockSizeException
+					| BadPaddingException | NoSuchProviderException e) {
+				throw new CryptoFailedException(e);
+			}
+		}
+		return plaintextMessage;
+	}
+}