short build records

WIP, incomplete, untested

router/java/src/net/i2p/data/i2np/BuildRequestRecord.java

@@ -57,7 +57,7 @@ import net.i2p.router.RouterContext;
  *   bytes  16-527: ElGamal encrypted block (discarding zero bytes at elg[0] and elg[257])
  * </pre>
  *
- * New ECIES format, ref: proposal 152:
+ * ECIES long record format, ref: proposal 152:
  *
  * Holds the unencrypted 464-byte tunnel request record,
  * with a constructor for ECIES decryption and a method for ECIES encryption.
@@ -90,6 +90,36 @@ import net.i2p.router.RouterContext;
  *   bytes 512-527: Poly1305 MAC
  * </pre>
  *
+ * ECIES short record format, ref: proposal 157:
+ *
+ * Holds the unencrypted 172-byte tunnel request record,
+ * with a constructor for ECIES decryption and a method for ECIES encryption.
+ * Iterative AES encryption/decryption is done elsewhere.
+ *
+ * Cleartext:
+ * <pre>
+ *   bytes     0-3: tunnel ID to receive messages as, nonzero
+ *   bytes     4-7: next tunnel ID, nonzero
+ *   bytes    8-39: next router identity hash
+ *   byte       40: flags
+ *   bytes   41-42: more flags, unused, set to 0 for compatibility
+ *   byte       43: layer enc. type
+ *   bytes   44-47: request time (in minutes since the epoch, rounded down)
+ *   bytes   48-51: request expiration (in seconds since creation)
+ *   bytes   52-55: next message ID
+ *   bytes    56-x: tunnel build options (Mapping)
+ *   bytes     x-x: other data as implied by flags or options
+ *   bytes   x-171: random padding
+ * </pre>
+ *
+ * Encrypted:
+ * <pre>
+ *   bytes    0-15: Hop's truncated identity hash
+ *   bytes   16-47: Sender's ephemeral X25519 public key
+ *   bytes  48-219: ChaCha20 encrypted BuildRequestRecord
+ *   bytes 220-235: Poly1305 MAC
+ * </pre>
+ *
  */
 public class BuildRequestRecord {
     private final byte[] _data;
@@ -138,7 +168,7 @@ public class BuildRequestRecord {
     // 222
     private static final int LENGTH = OFF_SEND_MSG_ID + 4 + PADDING_SIZE;
 
-    // New ECIES format
+    // ECIES long record format
     private static final int OFF_SEND_TUNNEL_EC = OFF_OUR_IDENT;
     private static final int OFF_SEND_IDENT_EC = OFF_SEND_TUNNEL_EC + 4;
     private static final int OFF_LAYER_KEY_EC = OFF_SEND_IDENT_EC + Hash.HASH_LENGTH;
@@ -152,6 +182,16 @@ public class BuildRequestRecord {
     private static final int OFF_OPTIONS = OFF_SEND_MSG_ID_EC + 4;
     private static final int LENGTH_EC = 464;
     private static final int MAX_OPTIONS_LENGTH = LENGTH_EC - OFF_OPTIONS; // includes options length
+
+    // ECIES short record format
+    private static final int OFF_FLAG_EC_SHORT = OFF_SEND_IDENT_EC + Hash.HASH_LENGTH;
+    private static final int OFF_LAYER_ENC_TYPE = OFF_FLAG_EC_SHORT + 3;
+    private static final int OFF_REQ_TIME_EC_SHORT = OFF_LAYER_ENC_TYPE + 1;
+    private static final int OFF_EXPIRATION_SHORT = OFF_REQ_TIME_EC + 4;
+    private static final int OFF_SEND_MSG_ID_EC_SHORT = OFF_EXPIRATION + 4;
+    private static final int OFF_OPTIONS_SHORT = OFF_SEND_MSG_ID_EC_SHORT + 4;
+    private static final int LENGTH_EC_SHORT = 172;
+    private static final int MAX_OPTIONS_LENGTH_SHORT = LENGTH_EC_SHORT - OFF_OPTIONS_SHORT; // includes options length
     
     private static final boolean TEST = false;
     private static KeyFactory TESTKF;
@@ -225,7 +265,8 @@ public class BuildRequestRecord {
      *
      */
     public boolean readIsInboundGateway() {
-        int off = _isEC ? OFF_FLAG_EC : OFF_FLAG;
+        int off = _isEC ? ( _data.length == LENGTH_EC_SHORT ? OFF_FLAG_EC_SHORT : OFF_FLAG_EC)
+                        : OFF_FLAG;
         return (_data[off] & FLAG_UNRESTRICTED_PREV) != 0;
     }
 
@@ -234,7 +275,8 @@ public class BuildRequestRecord {
      * fields refer to where the reply should be sent.
      */
     public boolean readIsOutboundEndpoint() { 
-        int off = _isEC ? OFF_FLAG_EC : OFF_FLAG;
+        int off = _isEC ? ( _data.length == LENGTH_EC_SHORT ? OFF_FLAG_EC_SHORT : OFF_FLAG_EC)
+                        : OFF_FLAG;
         return (_data[off] & FLAG_OUTBOUND_ENDPOINT) != 0;
     }
 
@@ -244,8 +286,10 @@ public class BuildRequestRecord {
      * This ignores leap seconds.
      */
     public long readRequestTime() {
-        if (_isEC)
-            return DataHelper.fromLong(_data, OFF_REQ_TIME_EC, 4) * (60 * 1000L);
+        if (_isEC) {
+            int off = _data.length == LENGTH_EC_SHORT ? OFF_REQ_TIME_EC_SHORT : OFF_REQ_TIME_EC;
+            return DataHelper.fromLong(_data, off, 4) * (60 * 1000L);
+        }
         return DataHelper.fromLong(_data, OFF_REQ_TIME, 4) * (60 * 60 * 1000L);
     }
 
@@ -254,7 +298,8 @@ public class BuildRequestRecord {
      * this specifies the message ID with which the reply should be sent.
      */
     public long readReplyMessageId() {
-        int off = _isEC ? OFF_SEND_MSG_ID_EC : OFF_SEND_MSG_ID;
+        int off = _isEC ? ( _data.length == LENGTH_EC_SHORT ? OFF_SEND_MSG_ID_EC_SHORT : OFF_SEND_MSG_ID_EC)
+                        : OFF_SEND_MSG_ID;
         return DataHelper.fromLong(_data, off, 4);
     }
 
@@ -265,7 +310,8 @@ public class BuildRequestRecord {
     public long readExpiration() {
         if (!_isEC)
             return DEFAULT_EXPIRATION_SECONDS * 1000L;
-        return DataHelper.fromLong(_data, OFF_EXPIRATION, 4) * 1000L;
+        int off = _data.length == LENGTH_EC_SHORT ? OFF_EXPIRATION_SHORT : OFF_EXPIRATION;
+        return DataHelper.fromLong(_data, off, 4) * 1000L;
     }
 
     /**
@@ -276,7 +322,11 @@ public class BuildRequestRecord {
     public Properties readOptions() {
         if (!_isEC)
             return null;
-        ByteArrayInputStream in = new ByteArrayInputStream(_data, OFF_OPTIONS, MAX_OPTIONS_LENGTH);
+        ByteArrayInputStream in;
+        if (_data.length == LENGTH_EC_SHORT)
+            in = new ByteArrayInputStream(_data, OFF_OPTIONS_SHORT, MAX_OPTIONS_LENGTH_SHORT);
+        else
+            in = new ByteArrayInputStream(_data, OFF_OPTIONS, MAX_OPTIONS_LENGTH);
         try {
             return DataHelper.readProperties(in, null);
         } catch (DataFormatException dfe) {
@@ -286,6 +336,17 @@ public class BuildRequestRecord {
         }
     }
     
+    /**
+     * ECIES short record only.
+     * @return 0 for ElGamal or ECIES long record
+     * @since 0.9.51
+     */
+    public int readLayerEncryptionType() {
+        if (_data.length == LENGTH_EC_SHORT)
+            return _data[OFF_LAYER_ENC_TYPE] & 0xff;
+        return 0;
+    }
+
     /**
      * Encrypt the record to the specified peer.  The result is formatted as: <pre>
      *   bytes 0-15: truncated SHA-256 of the current hop's identity (the toPeer parameter)
@@ -324,7 +385,8 @@ public class BuildRequestRecord {
         EncType type = toKey.getType();
         if (type != EncType.ECIES_X25519)
             throw new IllegalArgumentException();
-        byte[] out = new byte[EncryptedBuildRecord.LENGTH];
+        boolean isShort = _data.length == LENGTH_EC_SHORT;
+        byte[] out = new byte[isShort ? ShortEncryptedBuildRecord.LENGTH : EncryptedBuildRecord.LENGTH];
         System.arraycopy(toPeer.getData(), 0, out, 0, PEER_SIZE);
         HandshakeState state = null;
         try {
@@ -332,8 +394,8 @@ public class BuildRequestRecord {
             state = new HandshakeState(HandshakeState.PATTERN_ID_N, HandshakeState.INITIATOR, kf);
             state.getRemotePublicKey().setPublicKey(toKey.getData(), 0);
             state.start();
-            state.writeMessage(out, PEER_SIZE, _data, 0, LENGTH_EC);
-            EncryptedBuildRecord rv = new EncryptedBuildRecord(out);
+            state.writeMessage(out, PEER_SIZE, _data, 0, _data.length);
+            EncryptedBuildRecord rv = isShort ? new ShortEncryptedBuildRecord(out) : new EncryptedBuildRecord(out);
             _chachaReplyKey = new SessionKey(state.getChainingKey());
             _chachaReplyAD = new byte[32];
             System.arraycopy(state.getHandshakeHash(), 0, _chachaReplyAD, 0, 32);
@@ -414,8 +476,10 @@ public class BuildRequestRecord {
                 state.getLocalKeyPair().setKeys(ourKey.getData(), 0,
                                                 ourKey.toPublic().getData(), 0);
                 state.start();
-                decrypted = new byte[LENGTH_EC];
-                state.readMessage(encrypted, PEER_SIZE, EncryptedBuildRecord.LENGTH - PEER_SIZE,
+                int len = encryptedRecord.length();
+                boolean isShort = len == ShortEncryptedBuildRecord.LENGTH;
+                decrypted = new byte[isShort ? LENGTH_EC_SHORT : LENGTH_EC];
+                state.readMessage(encrypted, PEER_SIZE, len - PEER_SIZE,
                                   decrypted, 0);
                 _chachaReplyKey = new SessionKey(state.getChainingKey());
                 _chachaReplyAD = new byte[32];
@@ -507,7 +571,7 @@ public class BuildRequestRecord {
      * Populate this instance with data.  A new buffer is created to contain the data, with the 
      * necessary randomized padding.
      *
-     * ECIES only. ElGamal constructor above.
+     * ECIES long record only. ElGamal constructor above.
      *
      * @param receiveTunnelId tunnel the current hop will receive messages on
      * @param nextTunnelId id for the next hop, or where we send the reply (if we are the outbound endpoint)
@@ -559,6 +623,55 @@ public class BuildRequestRecord {
         }
     }
 
+    /**
+     * Populate this instance with data.  A new buffer is created to contain the data, with the 
+     * necessary randomized padding.
+     *
+     * ECIES short record only. ElGamal constructor above.
+     *
+     * @param receiveTunnelId tunnel the current hop will receive messages on
+     * @param nextTunnelId id for the next hop, or where we send the reply (if we are the outbound endpoint)
+     * @param nextHop next hop's identity, or where we send the reply (if we are the outbound endpoint)
+     * @param nextMsgId message ID to use when sending on to the next hop (or for the reply)
+     * @param isInGateway are we the gateway of an inbound tunnel?
+     * @param isOutEndpoint are we the endpoint of an outbound tunnel?
+     * @param options 116 bytes max when serialized
+     * @since 0.9.51
+     * @throws IllegalArgumentException if options too long
+     */
+    public BuildRequestRecord(I2PAppContext ctx, long receiveTunnelId, long nextTunnelId, Hash nextHop, long nextMsgId,
+                              boolean isInGateway, boolean isOutEndpoint, Properties options) {
+        byte buf[] = new byte[LENGTH_EC_SHORT];
+        _data = buf;
+        _isEC = true;
+        
+        DataHelper.toLong(buf, OFF_RECV_TUNNEL, 4, receiveTunnelId);
+        DataHelper.toLong(buf, OFF_SEND_TUNNEL_EC, 4, nextTunnelId);
+        System.arraycopy(nextHop.getData(), 0, buf, OFF_SEND_IDENT_EC, Hash.HASH_LENGTH);
+        if (isInGateway)
+            buf[OFF_FLAG_EC_SHORT] |= FLAG_UNRESTRICTED_PREV;
+        else if (isOutEndpoint)
+            buf[OFF_FLAG_EC_SHORT] |= FLAG_OUTBOUND_ENDPOINT;
+        // 2 bytes unused flags = 0
+        // 1 byte layer enc. type = 0
+        long truncatedMinute = ctx.clock().now();
+        // prevent hop identification at top of the minute
+        truncatedMinute -= ctx.random().nextInt(2048);
+        // this ignores leap seconds
+        truncatedMinute /= (60*1000L);
+        DataHelper.toLong(buf, OFF_REQ_TIME_EC_SHORT, 4, truncatedMinute);
+        DataHelper.toLong(buf, OFF_EXPIRATION_SHORT, 4, DEFAULT_EXPIRATION_SECONDS);
+        DataHelper.toLong(buf, OFF_SEND_MSG_ID_EC_SHORT, 4, nextMsgId);
+        try {
+            int off = DataHelper.toProperties(buf, OFF_OPTIONS_SHORT, options);
+            int sz = LENGTH_EC_SHORT - off;
+            if (sz > 0)
+                ctx.random().nextBytes(buf, off, sz);
+        } catch (Exception e) {
+            throw new IllegalArgumentException("options", e);
+        }
+    }
+
     /**
      *  @since 0.9.24
      */
@@ -566,6 +679,8 @@ public class BuildRequestRecord {
     public String toString() {
         StringBuilder buf = new StringBuilder(256);
         buf.append(_isEC ? "ECIES" : "ElGamal");
+        if (_data.length == LENGTH_EC_SHORT)
+            buf.append(" short ");
         buf.append(" BRR ");
         boolean isIBGW = readIsInboundGateway();
         boolean isOBEP = readIsOutboundEndpoint();
@@ -578,12 +693,14 @@ public class BuildRequestRecord {
             buf.append("part. in: ").append(readReceiveTunnelId())
                .append(" out: ").append(readNextTunnelId());
         }
-        buf.append(" to: ").append(readNextIdentity())
-           .append(" layer key: ").append(readLayerKey())
-           .append(" IV key: ").append(readIVKey())
-           .append(" reply key: ").append(readReplyKey())
-           .append(" reply IV: ").append(Base64.encode(readReplyIV()))
-           .append(" time: ").append(DataHelper.formatTime(readRequestTime()))
+        buf.append(" to: ").append(readNextIdentity());
+        if (_data.length != LENGTH_EC_SHORT) {
+            buf.append(" layer key: ").append(readLayerKey())
+               .append(" IV key: ").append(readIVKey())
+               .append(" reply key: ").append(readReplyKey())
+               .append(" reply IV: ").append(Base64.encode(readReplyIV()));
+        }
+        buf.append(" time: ").append(DataHelper.formatTime(readRequestTime()))
            .append(" reply msg id: ").append(readReplyMessageId())
            .append(" expires in: ").append(DataHelper.formatDuration(readExpiration()));
         if (_isEC) {

router/java/src/net/i2p/data/i2np/BuildResponseRecord.java

@@ -46,7 +46,7 @@ public class BuildResponseRecord {
     }
 
     /**
-     * Create a new encrypted response.
+     * Create a new encrypted response (long record).
      * ChaCha/Poly only for ECIES routers.
      *
      * @param status the response 0-255
@@ -77,6 +77,38 @@ public class BuildResponseRecord {
         return new EncryptedBuildRecord(rv);
     }
 
+    /**
+     * Create a new encrypted response (short record).
+     * ChaCha/Poly only for ECIES routers.
+     *
+     * @param status the response 0-255
+     * @param replyAD 32 bytes
+     * @param options 116 bytes max when serialized
+     * @return a 236-byte response record
+     * @throws IllegalArgumentException if options too big or on encryption failure
+     * @since 0.9.451
+     */
+    public static ShortEncryptedBuildRecord createShort(I2PAppContext ctx, int status, SessionKey replyKey,
+                                                        byte replyAD[], Properties options) {
+        byte rv[] = new byte[ShortTunnelBuildMessage.SHORT_RECORD_SIZE];
+        int off;
+        try {
+            off = DataHelper.toProperties(rv, 0, options);
+        } catch (Exception e) {
+            throw new IllegalArgumentException("options", e);
+        }
+        int sz = ShortTunnelBuildMessage.SHORT_RECORD_SIZE - off - 1;
+        if (sz > 0)
+            ctx.random().nextBytes(rv, off, sz);
+        else if (sz < 0)
+            throw new IllegalArgumentException("options");
+        rv[ShortTunnelBuildMessage.SHORT_RECORD_SIZE - 17] = (byte) status;
+        boolean ok = encryptAEADBlock(replyAD, rv, replyKey);
+        if (!ok)
+            throw new IllegalArgumentException("encrypt fail");
+        return new ShortEncryptedBuildRecord(rv);
+    }
+
     /**
      * Encrypts in place
      * @param ad non-null

router/java/src/net/i2p/data/i2np/I2NPMessageImpl.java

@@ -438,6 +438,15 @@ public abstract class I2NPMessageImpl implements I2NPMessage {
             // since 0.7.10
             case VariableTunnelBuildReplyMessage.MESSAGE_TYPE:
                 return new VariableTunnelBuildReplyMessage(context);
+            // since 0.9.51
+            case InboundTunnelBuildMessage.MESSAGE_TYPE:
+                return new InboundTunnelBuildMessage(context);
+            // since 0.9.51
+            case OutboundTunnelBuildReplyMessage.MESSAGE_TYPE:
+                return new OutboundTunnelBuildReplyMessage(context);
+            // since 0.9.51
+            case ShortTunnelBuildMessage.MESSAGE_TYPE:
+                return new ShortTunnelBuildMessage(context);
             default:
                 // unused
                 Builder builder = _builders.get(Integer.valueOf(type));

router/java/src/net/i2p/data/i2np/InboundTunnelBuildMessage.java

@@ -30,6 +30,16 @@ public class InboundTunnelBuildMessage extends TunnelBuildMessage {
         super(context, records);
     }
 
+    /**
+     *  @param record must be ShortEncryptedBuildRecord or null
+     */
+    @Override
+    public void setRecord(int index, EncryptedBuildRecord record) {
+        if (record != null && record.length() != SHORT_RECORD_SIZE)
+            throw new IllegalArgumentException();
+        super.setRecord(index, record);
+    }
+
     /**
      *  Set the slot and data for the plaintext record.
      *  @throws IllegalArgumentException on bad slot or data length.
@@ -71,7 +81,7 @@ public class InboundTunnelBuildMessage extends TunnelBuildMessage {
             throw new I2NPMessageException("Bad record count " + r);
         RECORD_COUNT = r;
         int _plaintextSlot = data[offset++] & 0xff;
-        if (_plaintextSlot < 0 || _plaintextSlot >= r)
+        if (_plaintextSlot >= r)
             throw new I2NPMessageException("Bad slot " + _plaintextSlot);
         int size = (int) DataHelper.fromLong(data, offset, 2);
         if (size <= 0 || size > MAX_PLAINTEXT_RECORD_SIZE)

router/java/src/net/i2p/data/i2np/OutboundTunnelBuildReplyMessage.java

@@ -30,6 +30,16 @@ public class OutboundTunnelBuildReplyMessage extends TunnelBuildReplyMessage {
         super(context, records);
     }
 
+    /**
+     *  @param record must be ShortEncryptedBuildRecord or null
+     */
+    @Override
+    public void setRecord(int index, EncryptedBuildRecord record) {
+        if (record != null && record.length() != SHORT_RECORD_SIZE)
+            throw new IllegalArgumentException();
+        super.setRecord(index, record);
+    }
+
     /**
      *  Set the slot and data for the plaintext record.
      *  @throws IllegalArgumentException on bad slot or data length.

router/java/src/net/i2p/data/i2np/ShortTunnelBuildMessage.java

@@ -21,6 +21,16 @@ public class ShortTunnelBuildMessage extends TunnelBuildMessage {
         super(context, records);
     }
 
+    /**
+     *  @param record must be ShortEncryptedBuildRecord or null
+     */
+    @Override
+    public void setRecord(int index, EncryptedBuildRecord record) {
+        if (record != null && record.length() != SHORT_RECORD_SIZE)
+            throw new IllegalArgumentException();
+        super.setRecord(index, record);
+    }
+
     @Override
     protected int calculateWrittenLength() { return 1 + (RECORD_COUNT * SHORT_RECORD_SIZE); }
 

router/java/src/net/i2p/data/i2np/TunnelBuildMessageBase.java

@@ -35,8 +35,14 @@ public abstract class TunnelBuildMessageBase extends I2NPMessageImpl {
         // else will be initialized by readMessage()
     }
 
+    /**
+     *  @param record may be null
+     */
     public void setRecord(int index, EncryptedBuildRecord record) { _records[index] = record; }
 
+    /**
+     *  @return may be null
+     */
     public EncryptedBuildRecord getRecord(int index) { return _records[index]; }
 
     /** @since 0.7.12 */

router/java/src/net/i2p/router/tunnel/BuildMessageGenerator.java

@@ -11,6 +11,9 @@ import net.i2p.data.SessionKey;
 import net.i2p.data.i2np.BuildRequestRecord;
 import net.i2p.data.i2np.EncryptedBuildRecord;
 import net.i2p.data.i2np.I2NPMessage;
+import net.i2p.data.i2np.InboundTunnelBuildMessage;
+import net.i2p.data.i2np.ShortEncryptedBuildRecord;
+import net.i2p.data.i2np.ShortTunnelBuildMessage;
 import net.i2p.data.i2np.TunnelBuildMessage;
 import net.i2p.router.RouterContext;
 
@@ -32,14 +35,17 @@ public abstract class BuildMessageGenerator {
     public static void createRecord(int recordNum, int hop, TunnelBuildMessage msg,
                                     TunnelCreatorConfig cfg, Hash replyRouter,
                                     long replyTunnel, RouterContext ctx, PublicKey peerKey) {
+        int mtype = msg.getType();
+        boolean isShort = mtype == InboundTunnelBuildMessage.MESSAGE_TYPE || mtype == ShortTunnelBuildMessage.MESSAGE_TYPE;
         EncryptedBuildRecord erec;
         if (peerKey != null) {
             boolean isEC = peerKey.getType() == EncType.ECIES_X25519;
             BuildRequestRecord req;
             if ( (!cfg.isInbound()) && (hop + 1 == cfg.getLength()) ) //outbound endpoint
-                req = createUnencryptedRecord(ctx, cfg, hop, replyRouter, replyTunnel, isEC);
+//// TODO if we're the OBEP
+                req = createUnencryptedRecord(ctx, cfg, hop, replyRouter, replyTunnel, isEC, isShort);
             else
-                req = createUnencryptedRecord(ctx, cfg, hop, null, -1, isEC);
+                req = createUnencryptedRecord(ctx, cfg, hop, null, -1, isEC, isShort);
             if (req == null)
                 throw new IllegalArgumentException("hop bigger than config");
             Hash peer = cfg.getPeer(hop);
@@ -50,26 +56,31 @@ public abstract class BuildMessageGenerator {
                 erec = req.encryptRecord(ctx, peerKey, peer);
             }
         } else {
-            byte encrypted[] = new byte[TunnelBuildMessage.RECORD_SIZE];
+            int len = isShort ? ShortTunnelBuildMessage.SHORT_RECORD_SIZE : TunnelBuildMessage.RECORD_SIZE;
+            byte encrypted[] = new byte[len];
             if (cfg.isInbound() && hop + 1 == cfg.getLength()) { // IBEP
                 System.arraycopy(cfg.getPeer(hop).getData(), 0, encrypted, 0, BuildRequestRecord.PEER_SIZE);
-                ctx.random().nextBytes(encrypted, BuildRequestRecord.PEER_SIZE, TunnelBuildMessage.RECORD_SIZE - BuildRequestRecord.PEER_SIZE);
+                ctx.random().nextBytes(encrypted, BuildRequestRecord.PEER_SIZE, len - BuildRequestRecord.PEER_SIZE);
                 byte[] h = new byte[Hash.HASH_LENGTH];
-                ctx.sha().calculateHash(encrypted, 0, TunnelBuildMessage.RECORD_SIZE, h, 0);
+                ctx.sha().calculateHash(encrypted, 0, len, h, 0);
                 cfg.setBlankHash(new Hash(h));
             } else {
                 ctx.random().nextBytes(encrypted);
             }
-            erec = new EncryptedBuildRecord(encrypted);
+            erec = isShort ? new ShortEncryptedBuildRecord(encrypted) : new EncryptedBuildRecord(encrypted);
         }
         msg.setRecord(recordNum, erec);
     }
     
     /**
      *  Returns null if hop >= cfg.length
+     *
+     *  @param isEC must be true if isShort is true
+     *  @param isShort short EC record
      */
     private static BuildRequestRecord createUnencryptedRecord(I2PAppContext ctx, TunnelCreatorConfig cfg, int hop,
-                                                              Hash replyRouter, long replyTunnel, boolean isEC) {
+                                                              Hash replyRouter, long replyTunnel, boolean isEC,
+                                                              boolean isShort) {
         if (hop < cfg.getLength()) {
             // ok, now lets fill in some data
             HopConfig hopConfig = cfg.getConfig(hop);
@@ -114,9 +125,15 @@ public abstract class BuildMessageGenerator {
             BuildRequestRecord rec;
             if (isEC) {
                 // TODO pass properties from cfg
-                rec = new BuildRequestRecord(ctx, recvTunnelId, nextTunnelId, nextPeer,
-                                             nextMsgId, layerKey, ivKey, replyKey, 
-                                             iv, isInGW, isOutEnd, EmptyProperties.INSTANCE);
+                if (isShort) {
+                    rec = new BuildRequestRecord(ctx, recvTunnelId, nextTunnelId, nextPeer,
+                                                 nextMsgId, layerKey, ivKey, replyKey, 
+                                                 iv, isInGW, isOutEnd, EmptyProperties.INSTANCE);
+                } else {
+                    rec = new BuildRequestRecord(ctx, recvTunnelId, nextTunnelId, nextPeer,
+                                                 nextMsgId,
+                                                 isInGW, isOutEnd, EmptyProperties.INSTANCE);
+                }
             } else {
                 rec = new BuildRequestRecord(ctx, recvTunnelId, peer, nextTunnelId, nextPeer,
                                              nextMsgId, layerKey, ivKey, replyKey, 
@@ -138,6 +155,9 @@ public abstract class BuildMessageGenerator {
      */
     public static void layeredEncrypt(I2PAppContext ctx, TunnelBuildMessage msg,
                                       TunnelCreatorConfig cfg, List<Integer> order) {
+////// TODO check msg type for short (STBM or ITBM)
+        int mtype = msg.getType();
+        boolean isShort = mtype == InboundTunnelBuildMessage.MESSAGE_TYPE || mtype == ShortTunnelBuildMessage.MESSAGE_TYPE;
         // encrypt the records so that the right elements will be visible at the right time
         for (int i = 0; i < msg.getRecordCount(); i++) {
             EncryptedBuildRecord rec = msg.getRecord(i);

router/java/src/net/i2p/router/tunnel/OutboundGatewayMessage.java

@@ -59,6 +59,7 @@ class OutboundGatewayMessage extends PendingGatewayMessage implements CDPQEntry
                 return 1000;
 
             // building new IB tunnel
+            case ShortTunnelBuildMessage.MESSAGE_TYPE:
             case TunnelBuildMessage.MESSAGE_TYPE:
             case VariableTunnelBuildMessage.MESSAGE_TYPE:
                 return 500;
@@ -78,6 +79,8 @@ class OutboundGatewayMessage extends PendingGatewayMessage implements CDPQEntry
             // these shouldn't go into a OBGW
             case DatabaseSearchReplyMessage.MESSAGE_TYPE:
             case DataMessage.MESSAGE_TYPE:
+            case InboundTunnelBuildMessage.MESSAGE_TYPE:
+            case OutboundTunnelBuildReplyMessage.MESSAGE_TYPE:
             case TunnelBuildReplyMessage.MESSAGE_TYPE:
             case TunnelDataMessage.MESSAGE_TYPE:
             case TunnelGatewayMessage.MESSAGE_TYPE:

router/java/src/net/i2p/router/tunnel/TunnelDispatcher.java

@@ -11,6 +11,9 @@ import net.i2p.data.DataHelper;
 import net.i2p.data.Hash;
 import net.i2p.data.TunnelId;
 import net.i2p.data.i2np.I2NPMessage;
+import net.i2p.data.i2np.InboundTunnelBuildMessage;
+import net.i2p.data.i2np.OutboundTunnelBuildReplyMessage;
+import net.i2p.data.i2np.ShortTunnelBuildMessage;
 import net.i2p.data.i2np.TunnelBuildMessage;
 import net.i2p.data.i2np.TunnelBuildReplyMessage;
 import net.i2p.data.i2np.TunnelDataMessage;
@@ -774,13 +777,15 @@ public class TunnelDispatcher implements Service {
         float factor;
         if (loc == Location.OBEP) {
             // we don't need to check for VTBRM/TBRM as that happens at tunnel creation
-            if (type == VariableTunnelBuildMessage.MESSAGE_TYPE || type == TunnelBuildMessage.MESSAGE_TYPE)
+            if (type == VariableTunnelBuildMessage.MESSAGE_TYPE || type == TunnelBuildMessage.MESSAGE_TYPE ||
+                type == ShortTunnelBuildMessage.MESSAGE_TYPE)
                 factor = 1 / 1.5f;
             else
                 factor = 1.5f;
         } else if (loc == Location.IBGW) {
             // we don't need to check for VTBM/TBM as that happens at tunnel creation
-            if (type == VariableTunnelBuildReplyMessage.MESSAGE_TYPE || type == TunnelBuildReplyMessage.MESSAGE_TYPE)
+            if (type == VariableTunnelBuildReplyMessage.MESSAGE_TYPE || type == TunnelBuildReplyMessage.MESSAGE_TYPE ||
+                type == OutboundTunnelBuildReplyMessage.MESSAGE_TYPE || type == InboundTunnelBuildMessage.MESSAGE_TYPE)
                 factor = 1 / (1.5f * 1.5f * 1.5f);
             else
                 factor = 1 / 1.5f;

router/java/src/net/i2p/router/tunnel/pool/BuildHandler.java

@@ -13,11 +13,15 @@ import net.i2p.data.EmptyProperties;
 import net.i2p.data.Hash;
 import net.i2p.data.router.RouterIdentity;
 import net.i2p.data.router.RouterInfo;
+import net.i2p.data.SessionKey;
 import net.i2p.data.TunnelId;
 import net.i2p.data.i2np.BuildRequestRecord;
 import net.i2p.data.i2np.BuildResponseRecord;
 import net.i2p.data.i2np.EncryptedBuildRecord;
 import net.i2p.data.i2np.I2NPMessage;
+import net.i2p.data.i2np.InboundTunnelBuildMessage;
+import net.i2p.data.i2np.OutboundTunnelBuildReplyMessage;
+import net.i2p.data.i2np.ShortTunnelBuildMessage;
 import net.i2p.data.i2np.TunnelBuildMessage;
 import net.i2p.data.i2np.TunnelBuildReplyMessage;
 import net.i2p.data.i2np.TunnelGatewayMessage;
@@ -28,6 +32,8 @@ import net.i2p.router.Job;
 import net.i2p.router.JobImpl;
 import net.i2p.router.OutNetMessage;
 import net.i2p.router.RouterContext;
+import net.i2p.router.crypto.ratchet.RatchetSessionTag;
+import net.i2p.router.networkdb.kademlia.MessageWrapper;
 import net.i2p.router.peermanager.TunnelHistory;
 import net.i2p.router.tunnel.BuildMessageProcessor;
 import net.i2p.router.tunnel.BuildReplyHandler;
@@ -166,6 +172,9 @@ class BuildHandler implements Runnable {
         ctx.inNetMessagePool().registerHandlerJobBuilder(TunnelBuildReplyMessage.MESSAGE_TYPE, tbrmhjb);
         ctx.inNetMessagePool().registerHandlerJobBuilder(VariableTunnelBuildMessage.MESSAGE_TYPE, tbmhjb);
         ctx.inNetMessagePool().registerHandlerJobBuilder(VariableTunnelBuildReplyMessage.MESSAGE_TYPE, tbrmhjb);
+        ctx.inNetMessagePool().registerHandlerJobBuilder(InboundTunnelBuildMessage.MESSAGE_TYPE, tbmhjb);
+        ctx.inNetMessagePool().registerHandlerJobBuilder(ShortTunnelBuildMessage.MESSAGE_TYPE, tbmhjb);
+        ctx.inNetMessagePool().registerHandlerJobBuilder(OutboundTunnelBuildReplyMessage.MESSAGE_TYPE, tbrmhjb);
     }
 
     /**
@@ -722,6 +731,21 @@ class BuildHandler implements Runnable {
                     _log.warn("Dropping build request, we are the previous hop: " + req);
                 return;
             }
+            if (state.msg.getType() == InboundTunnelBuildMessage.MESSAGE_TYPE) {
+                // can only be at IBGW
+                _context.statManager().addRateData("tunnel.rejectHostile", 1);
+                if (_log.shouldWarn())
+                    _log.warn("Dropping ITBM, we are not IBGW: " + req);
+                return;
+            }
+        } else {
+            if (state.msg.getType() == ShortTunnelBuildMessage.MESSAGE_TYPE) {
+                // cannot be at IBGW
+                _context.statManager().addRateData("tunnel.rejectHostile", 1);
+                if (_log.shouldWarn())
+                    _log.warn("Dropping STBM, we are IBGW: " + req);
+                return;
+            }
         }
         if ((!isOutEnd) && (!isInGW)) {
             // Previous and next hop the same? Don't help somebody be evil. Drop it without a reply.
@@ -948,20 +972,44 @@ class BuildHandler implements Runnable {
         if (isEC) {
             // TODO options
             Properties props = EmptyProperties.INSTANCE;
-            reply = BuildResponseRecord.create(_context, response, req.getChaChaReplyKey(), req.getChaChaReplyAD(), props);
+            if (state.msg.getType() == ShortTunnelBuildMessage.MESSAGE_TYPE) {
+                if (isOutEnd) {
+                    // reply will be sent in plaintext in a OTBRM, see below
+                    reply = null;
+                } else {
+                    // short build record
+                    reply = BuildResponseRecord.createShort(_context, response, req.getChaChaReplyKey(), req.getChaChaReplyAD(), props);
+                }
+            } else {
+                reply = BuildResponseRecord.create(_context, response, req.getChaChaReplyKey(), req.getChaChaReplyAD(), props);
+            }
         } else {
             reply = BuildResponseRecord.create(_context, response, req.readReplyKey(), req.readReplyIV(), state.msg.getUniqueId());
         }
         int records = state.msg.getRecordCount();
         int ourSlot = -1;
-        for (int j = 0; j < records; j++) {
-            if (state.msg.getRecord(j) == null) {
-                ourSlot = j;
-                state.msg.setRecord(j, reply);
-                //if (_log.shouldLog(Log.DEBUG))
-                //    _log.debug("Full reply record for slot " + ourSlot + "/" + ourId + "/" + nextId + "/" + req.readReplyMessageId()
-                //               + ": " + Base64.encode(reply));
-                break;
+        ShortTunnelBuildMessage stbm = null;
+        if (state.msg.getType() == InboundTunnelBuildMessage.MESSAGE_TYPE) {
+            // IBGW only (enforced above)
+            // Create a ShortTunnelBuildMessage and populate it for sending
+            InboundTunnelBuildMessage itbm = (InboundTunnelBuildMessage) state.msg;
+            ourSlot = itbm.getPlaintextSlot();
+            stbm = new ShortTunnelBuildMessage(_context, records);
+            for (int j = 0; j < records; j++) {
+                if (j == ourSlot)
+                    stbm.setRecord(j, reply);
+                else
+                    stbm.setRecord(j, itbm.getRecord(j));
+            }
+        } else {
+            for (int j = 0; j < records; j++) {
+                if (state.msg.getRecord(j) == null) {
+                    ourSlot = j;
+                    if (!(isOutEnd && state.msg.getType() == ShortTunnelBuildMessage.MESSAGE_TYPE))
+                        state.msg.setRecord(j, reply);
+                    // else reply will be sent in plaintext
+                    break;
+                }
             }
         }
 
@@ -973,9 +1021,14 @@ class BuildHandler implements Runnable {
         // now actually send the response
         long expires = now + NEXT_HOP_SEND_TIMEOUT;
         if (!isOutEnd) {
-            state.msg.setUniqueId(req.readReplyMessageId());
-            state.msg.setMessageExpiration(expires);
-            OutNetMessage msg = new OutNetMessage(_context, state.msg, expires, PRIORITY, nextPeerInfo);
+            TunnelBuildMessage nextMessage;
+            if (stbm != null)
+                nextMessage = stbm;
+            else
+                nextMessage = state.msg;
+            nextMessage.setUniqueId(req.readReplyMessageId());
+            nextMessage.setMessageExpiration(expires);
+            OutNetMessage msg = new OutNetMessage(_context, nextMessage, expires, PRIORITY, nextPeerInfo);
             if (response == 0)
                 msg.setOnFailedSendJob(new TunnelBuildNextHopFailJob(_context, cfg));
             _context.outNetMessagePool().add(msg);
@@ -984,16 +1037,36 @@ class BuildHandler implements Runnable {
             // send it to the reply tunnel on the reply peer within a new TunnelBuildReplyMessage
             // (enough layers jrandom?)
             TunnelBuildReplyMessage replyMsg;
-            if (records == TunnelBuildMessage.MAX_RECORD_COUNT)
+            if (state.msg.getType() == ShortTunnelBuildMessage.MESSAGE_TYPE) {
+                OutboundTunnelBuildReplyMessage otbrm  = new OutboundTunnelBuildReplyMessage(_context, records);
+                otbrm.setPlaintextRecord(ourSlot, null); // TODO
+                replyMsg = otbrm;
+            } else if (records == TunnelBuildMessage.MAX_RECORD_COUNT) {
                 replyMsg = new TunnelBuildReplyMessage(_context);
-            else
+            } else {
                 replyMsg = new VariableTunnelBuildReplyMessage(_context, records);
-            for (int i = 0; i < records; i++)
+            }
+            for (int i = 0; i < records; i++) {
                 replyMsg.setRecord(i, state.msg.getRecord(i));
+            }
             replyMsg.setUniqueId(req.readReplyMessageId());
             replyMsg.setMessageExpiration(expires);
+            I2NPMessage outMessage;
+            if (state.msg.getType() == ShortTunnelBuildMessage.MESSAGE_TYPE) {
+                // garlic encrypt
+                SessionKey sk = null; // TODO
+                RatchetSessionTag st = null; // TODO
+                outMessage = MessageWrapper.wrap(_context, replyMsg, sk, st);
+                if (outMessage == null) {
+                    if (_log.shouldWarn())
+                        _log.warn("OTBRM encrypt fail");
+                    return;
+                }
+            } else {
+                outMessage = replyMsg;
+            }
             TunnelGatewayMessage m = new TunnelGatewayMessage(_context);
-            m.setMessage(replyMsg);
+            m.setMessage(outMessage);
             m.setMessageExpiration(expires);
             m.setTunnelId(new TunnelId(nextId));
             if (_context.routerHash().equals(nextPeer)) {

router/java/src/net/i2p/router/tunnel/pool/BuildRequestor.java

@@ -4,6 +4,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
+import net.i2p.crypto.EncType;
 import net.i2p.data.DataHelper;
 import net.i2p.data.Hash;
 import net.i2p.data.PublicKey;
@@ -11,6 +12,7 @@ import net.i2p.data.router.RouterInfo;
 import net.i2p.data.TunnelId;
 import net.i2p.data.i2np.I2NPMessage;
 import net.i2p.data.i2np.InboundTunnelBuildMessage;
+import net.i2p.data.i2np.ShortTunnelBuildMessage;
 import net.i2p.data.i2np.TunnelBuildMessage;
 import net.i2p.data.i2np.VariableTunnelBuildMessage;
 import net.i2p.router.JobImpl;
@@ -31,8 +33,9 @@ import net.i2p.util.VersionComparator;
  */
 abstract class BuildRequestor {
     private static final List<Integer> ORDER = new ArrayList<Integer>(TunnelBuildMessage.MAX_RECORD_COUNT);
-    //private static final String MIN_VARIABLE_VERSION = "0.7.12";
+    private static final String MIN_NEWTBM_VERSION = "0.9.51";
     private static final boolean SEND_VARIABLE = true;
+    private static final boolean SEND_SHORT = false;
     private static final int SHORT_RECORDS = 4;
     private static final List<Integer> SHORT_ORDER = new ArrayList<Integer>(SHORT_RECORDS);
     /** 5 (~2600 bytes) fits nicely in 3 tunnel messages */
@@ -268,18 +271,18 @@ abstract class BuildRequestor {
         return true;
     }
 
-    /** @since 0.7.12 */
-/****
-we can assume everybody supports variable now...
-keep this here for the next time we change the build protocol
-    private static boolean supportsVariable(RouterContext ctx, Hash h) {
+    /**
+     * @since 0.9.51
+     */
+    private static boolean supportsShortTBM(RouterContext ctx, Hash h) {
         RouterInfo ri = ctx.netDb().lookupRouterInfoLocally(h);
         if (ri == null)
             return false;
+        if (ri.getIdentity().getPublicKey().getType() != EncType.ECIES_X25519)
+            return false;
         String v = ri.getVersion();
-        return VersionComparator.comp(v, MIN_VARIABLE_VERSION) >= 0;
+        return VersionComparator.comp(v, MIN_NEWTBM_VERSION) >= 0;
     }
-****/
 
     /**
      *  If the tunnel is short enough, and everybody in the tunnel, and the
@@ -294,53 +297,54 @@ keep this here for the next time we change the build protocol
         long replyTunnel = 0;
         Hash replyRouter;
         boolean useVariable = SEND_VARIABLE && cfg.getLength() <= MEDIUM_RECORDS;
+        boolean useShortTBM = SEND_SHORT && ctx.keyManager().getPublicKey().getType() == EncType.ECIES_X25519;
 
         if (cfg.isInbound()) {
             //replyTunnel = 0; // as above
             replyRouter = ctx.routerHash();
-/****
-we can assume everybody supports variable now...
-keep this here for the next time we change the build protocol
-            if (useVariable) {
-                // check the reply OBEP and all the tunnel peers except ourselves
-                if (!supportsVariable(ctx, pairedTunnel.getPeer(pairedTunnel.getLength() - 1))) {
-                    useVariable = false;
-                } else {
-                    for (int i = 0; i < cfg.getLength() - 1; i++) {
-                        if (!supportsVariable(ctx, cfg.getPeer(i))) {
-                            useVariable = false;
-                            break;
-                        }
+            if (useShortTBM) {
+                // check all the tunnel peers except ourselves
+                for (int i = 0; i < cfg.getLength() - 1; i++) {
+                    if (!supportsShortTBM(ctx, cfg.getPeer(i))) {
+                        useShortTBM = false;
+                        break;
                     }
                 }
             }
-****/
         } else {
             replyTunnel = pairedTunnel.getReceiveTunnelId(0).getTunnelId();
             replyRouter = pairedTunnel.getPeer(0);
-/****
-we can assume everybody supports variable now
-keep this here for the next time we change the build protocol
-            if (useVariable) {
-                // check the reply IBGW and all the tunnel peers except ourselves
-                if (!supportsVariable(ctx, replyRouter)) {
-                    useVariable = false;
-                } else {
-                    for (int i = 1; i < cfg.getLength() - 1; i++) {
-                        if (!supportsVariable(ctx, cfg.getPeer(i))) {
-                            useVariable = false;
-                            break;
-                        }
+            if (useShortTBM) {
+                // check all the tunnel peers except ourselves
+                for (int i = 1; i < cfg.getLength() - 1; i++) {
+                    if (!supportsShortTBM(ctx, cfg.getPeer(i))) {
+                        useShortTBM = false;
+                        break;
                     }
                 }
             }
-****/
         }
 
         // populate and encrypt the message
         TunnelBuildMessage msg;
         List<Integer> order;
-        if (useVariable) {
+        if (useShortTBM) {
+            int len;
+            if (cfg.getLength() <= SHORT_RECORDS) {
+                len = SHORT_RECORDS;
+                order = new ArrayList<Integer>(SHORT_ORDER);
+            } else if (cfg.getLength() <= MEDIUM_RECORDS) {
+                len = MEDIUM_RECORDS;
+                order = new ArrayList<Integer>(MEDIUM_ORDER);
+            } else {
+                len = TunnelBuildMessage.MAX_RECORD_COUNT;
+                order = new ArrayList<Integer>(ORDER);
+            }
+            if (cfg.isInbound())
+                msg = new InboundTunnelBuildMessage(ctx, len);
+            else
+                msg = new ShortTunnelBuildMessage(ctx, len);
+        } else if (useVariable) {
             if (cfg.getLength() <= SHORT_RECORDS) {
                 msg = new VariableTunnelBuildMessage(ctx, SHORT_RECORDS);
                 order = new ArrayList<Integer>(SHORT_ORDER);