1 files changed, 153 insertions, 0 deletions
diff --git a/src/main/java/org/whispersystems/libaxolotl/protocol/KeyExchangeMessage.java b/src/main/java/org/whispersystems/libaxolotl/protocol/KeyExchangeMessage.java
new file mode 100644
index 00000000..bec9208c
--- /dev/null
+++ b/src/main/java/org/whispersystems/libaxolotl/protocol/KeyExchangeMessage.java
@@ -0,0 +1,153 @@
+package org.whispersystems.libaxolotl.protocol;
+
+
+import com.google.protobuf.ByteString;
+
+import org.whispersystems.libaxolotl.IdentityKey;
+import org.whispersystems.libaxolotl.InvalidKeyException;
+import org.whispersystems.libaxolotl.InvalidMessageException;
+import org.whispersystems.libaxolotl.InvalidVersionException;
+import org.whispersystems.libaxolotl.LegacyMessageException;
+import org.whispersystems.libaxolotl.ecc.Curve;
+import org.whispersystems.libaxolotl.ecc.ECPublicKey;
+import org.whispersystems.libaxolotl.util.ByteUtil;
+
+import java.io.IOException;
+
+import static org.whispersystems.libaxolotl.protocol.WhisperProtos.KeyExchangeMessage.Builder;
+
+public class KeyExchangeMessage {
+
+  public static final int INITIATE_FLAG              = 0x01;
+  public static final int RESPONSE_FLAG              = 0X02;
+  public static final int SIMULTAENOUS_INITIATE_FLAG = 0x04;
+
+  private final int         version;
+  private final int         supportedVersion;
+  private final int         sequence;
+  private final int         flags;
+
+  private final ECPublicKey baseKey;
+  private final byte[]      baseKeySignature;
+  private final ECPublicKey ratchetKey;
+  private final IdentityKey identityKey;
+  private final byte[]      serialized;
+
+  public KeyExchangeMessage(int messageVersion, int sequence, int flags,
+                            ECPublicKey baseKey, byte[] baseKeySignature,
+                            ECPublicKey ratchetKey,
+                            IdentityKey identityKey)
+  {
+    this.supportedVersion = CiphertextMessage.CURRENT_VERSION;
+    this.version          = messageVersion;
+    this.sequence         = sequence;
+    this.flags            = flags;
+    this.baseKey          = baseKey;
+    this.baseKeySignature = baseKeySignature;
+    this.ratchetKey       = ratchetKey;
+    this.identityKey      = identityKey;
+
+    byte[]  version = {ByteUtil.intsToByteHighAndLow(this.version, this.supportedVersion)};
+    Builder builder = WhisperProtos.KeyExchangeMessage
+                                   .newBuilder()
+                                   .setId((sequence << 5) | flags)
+                                   .setBaseKey(ByteString.copyFrom(baseKey.serialize()))
+                                   .setRatchetKey(ByteString.copyFrom(ratchetKey.serialize()))
+                                   .setIdentityKey(ByteString.copyFrom(identityKey.serialize()));
+
+    if (messageVersion >= 3) {
+      builder.setBaseKeySignature(ByteString.copyFrom(baseKeySignature));
+    }
+
+    this.serialized = ByteUtil.combine(version, builder.build().toByteArray());
+  }
+
+  public KeyExchangeMessage(byte[] serialized)
+      throws InvalidMessageException, InvalidVersionException, LegacyMessageException
+  {
+    try {
+      byte[][] parts        = ByteUtil.split(serialized, 1, serialized.length - 1);
+      this.version          = ByteUtil.highBitsToInt(parts[0][0]);
+      this.supportedVersion = ByteUtil.lowBitsToInt(parts[0][0]);
+
+      if (this.version <= CiphertextMessage.UNSUPPORTED_VERSION) {
+        throw new LegacyMessageException("Unsupported legacy version: " + this.version);
+      }
+
+      if (this.version > CiphertextMessage.CURRENT_VERSION) {
+        throw new InvalidVersionException("Unknown version: " + this.version);
+      }
+
+      WhisperProtos.KeyExchangeMessage message = WhisperProtos.KeyExchangeMessage.parseFrom(parts[1]);
+
+      if (!message.hasId()           || !message.hasBaseKey()     ||
+          !message.hasRatchetKey()   || !message.hasIdentityKey() ||
+          (this.version >=3 && !message.hasBaseKeySignature()))
+      {
+        throw new InvalidMessageException("Some required fields missing!");
+      }
+
+      this.sequence         = message.getId() >> 5;
+      this.flags            = message.getId() & 0x1f;
+      this.serialized       = serialized;
+      this.baseKey          = Curve.decodePoint(message.getBaseKey().toByteArray(), 0);
+      this.baseKeySignature = message.getBaseKeySignature().toByteArray();
+      this.ratchetKey       = Curve.decodePoint(message.getRatchetKey().toByteArray(), 0);
+      this.identityKey      = new IdentityKey(message.getIdentityKey().toByteArray(), 0);
+    } catch (InvalidKeyException | IOException e) {
+      throw new InvalidMessageException(e);
+    }
+  }
+
+  public int getVersion() {
+    return version;
+  }
+
+  public ECPublicKey getBaseKey() {
+    return baseKey;
+  }
+
+  public byte[] getBaseKeySignature() {
+    return baseKeySignature;
+  }
+
+  public ECPublicKey getRatchetKey() {
+    return ratchetKey;
+  }
+
+  public IdentityKey getIdentityKey() {
+    return identityKey;
+  }
+
+  public boolean hasIdentityKey() {
+    return true;
+  }
+
+  public int getMaxVersion() {
+    return supportedVersion;
+  }
+
+  public boolean isResponse() {
+    return ((flags & RESPONSE_FLAG) != 0);
+  }
+
+  public boolean isInitiate() {
+    return (flags & INITIATE_FLAG) != 0;
+  }
+
+  public boolean isResponseForSimultaneousInitiate() {
+    return (flags & SIMULTAENOUS_INITIATE_FLAG) != 0;
+  }
+
+  public int getFlags() {
+    return flags;
+  }
+
+  public int getSequence() {
+    return sequence;
+  }
+
+  public byte[] serialize() {
+    return serialized;
+  }
+}