From 5c1700c2ab3cdbc87dd1374458fefa3f6bd9ce51 Mon Sep 17 00:00:00 2001
From: zzz <zzz@mail.i2p>
Date: Fri, 20 Mar 2020 19:01:56 +0000
Subject: [PATCH] Ratchet: Make DI optional in ACK request Don't put ACK
 request in NS or NSR

---
 .../crypto/ratchet/ECIESAEADEngine.java       | 11 ++++--
 .../router/crypto/ratchet/RatchetPayload.java | 34 ++++++++++++++-----
 2 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/router/java/src/net/i2p/router/crypto/ratchet/ECIESAEADEngine.java b/router/java/src/net/i2p/router/crypto/ratchet/ECIESAEADEngine.java
index 743860592..19c74065b 100644
--- a/router/java/src/net/i2p/router/crypto/ratchet/ECIESAEADEngine.java
+++ b/router/java/src/net/i2p/router/crypto/ratchet/ECIESAEADEngine.java
@@ -583,7 +583,8 @@ public final class ECIESAEADEngine {
         if (re == null) {
             if (_log.shouldDebug())
                 _log.debug("Encrypting as NS to " + target);
-            return encryptNewSession(cloves, target, priv, keyManager, replyDI);
+            // no ack in NS
+            return encryptNewSession(cloves, target, priv, keyManager, null);
         }
 
         HandshakeState state = re.key.getHandshakeState();
@@ -597,7 +598,8 @@ public final class ECIESAEADEngine {
             }
             if (_log.shouldDebug())
                 _log.debug("Encrypting as NSR to " + target + " with tag " + re.tag.toBase64());
-            return encryptNewSessionReply(cloves, target, state, re.tag, keyManager, replyDI);
+            // no ack in NSR
+            return encryptNewSessionReply(cloves, target, state, re.tag, keyManager, null);
         }
         if (_log.shouldDebug())
             _log.debug("Encrypting as ES to " + target + " with key " + re.key + " and tag " + re.tag.toBase64());
@@ -812,6 +814,7 @@ public final class ECIESAEADEngine {
         public final List<GarlicClove> cloveSet = new ArrayList<GarlicClove>(3);
         public long datetime;
         public NextSessionKey nextKey;
+        public boolean ackRequested;
 
         public void gotDateTime(long time) {
             if (_log.shouldDebug())
@@ -846,6 +849,7 @@ public final class ECIESAEADEngine {
         public void gotAckRequest(int id, DeliveryInstructions di) {
             if (_log.shouldDebug())
                 _log.debug("Got ACK REQUEST block: " + di);
+            ackRequested = true;
         }
 
         public void gotTermination(int reason, long count) {
@@ -890,7 +894,8 @@ public final class ECIESAEADEngine {
         }
         if (replyDI != null) {
             // put after the cloves so recipient has any LS garlic
-            Block block = new AckRequestBlock(0, replyDI);
+            // ignore actual DI
+            Block block = new AckRequestBlock(0, null);
             blocks.add(block);
             len += block.getTotalLength();
         }
diff --git a/router/java/src/net/i2p/router/crypto/ratchet/RatchetPayload.java b/router/java/src/net/i2p/router/crypto/ratchet/RatchetPayload.java
index 0290131c4..836d1db44 100644
--- a/router/java/src/net/i2p/router/crypto/ratchet/RatchetPayload.java
+++ b/router/java/src/net/i2p/router/crypto/ratchet/RatchetPayload.java
@@ -68,6 +68,7 @@ class RatchetPayload {
         public void gotAck(int id, int n);
 
         /**
+         *  @param di may be null
          *  @since 0.9.46
          */
         public void gotAckRequest(int id, DeliveryInstructions di);
@@ -148,7 +149,7 @@ class RatchetPayload {
                 case BLOCK_ACKKEY:
                   {
                     if (len < 4 || (len % 4) != 0)
-                        throw new IOException("Bad length for REPLYDI: " + len);
+                        throw new IOException("Bad length for ACKKEY: " + len);
                     for (int j = i; j < i + len; j += 4) {
                         int id = (int) DataHelper.fromLong(payload, j, 2);
                         int n = (int) DataHelper.fromLong(payload, j + 2, 2);
@@ -159,11 +160,16 @@ class RatchetPayload {
 
                 case BLOCK_REPLYDI:
                   {
-                    if (len < 6)
+                    if (len < 3)
                         throw new IOException("Bad length for REPLYDI: " + len);
-                    int id = (int) DataHelper.fromLong(payload, i, 4);
-                    DeliveryInstructions di = new DeliveryInstructions();
-                    di.readBytes(payload, i + 5);
+                    int id = (int) DataHelper.fromLong(payload, i, 2);
+                    DeliveryInstructions di;
+                    if ((payload[2] & 0x01) != 0) {
+                        di = new DeliveryInstructions();
+                        di.readBytes(payload, i + 3);
+                    } else {
+                        di = null;
+                    }
                     cb.gotAckRequest(id, di);
                   }
                     break;
@@ -383,12 +389,22 @@ class RatchetPayload {
     public static class AckRequestBlock extends Block {
         private final byte[] data;
 
+        /**
+         *  @param sessionID 0 - 65535
+         *  @param di may be null
+         */
         public AckRequestBlock(int sessionID, DeliveryInstructions di) {
             super(BLOCK_REPLYDI);
-            data = new byte[5 + di.getSize()];
-            DataHelper.toLong(data, 0, 4, sessionID);
-            // flag is zero
-            di.writeBytes(data, 5);
+            int len = 3;
+            if (di != null)
+                len += di.getSize();
+            data = new byte[len];
+            DataHelper.toLong(data, 0, 2, sessionID);
+            if (di != null) {
+                data[2] = 0x01;
+                di.writeBytes(data, 3);
+            }
+            // else flag is zero
         }
 
         public int getDataLength() {