From 119aff932429e5a292608fb43fc034767aa940eb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Arnaud=20Cogolu=C3=A8gnes?= <acogoluegnes@gmail.com>
Date: Thu, 29 Jul 2021 16:19:14 +0200
Subject: [PATCH] Keep reading from network on TLS buffer underflow

Fixes #700
---
 .../client/impl/nio/SslEngineFrameBuilder.java    | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/main/java/com/rabbitmq/client/impl/nio/SslEngineFrameBuilder.java b/src/main/java/com/rabbitmq/client/impl/nio/SslEngineFrameBuilder.java
index c2f1923874..e96b2d7e8c 100644
--- a/src/main/java/com/rabbitmq/client/impl/nio/SslEngineFrameBuilder.java
+++ b/src/main/java/com/rabbitmq/client/impl/nio/SslEngineFrameBuilder.java
@@ -32,6 +32,8 @@ public class SslEngineFrameBuilder extends FrameBuilder {
 
     private final ByteBuffer cipherBuffer;
 
+    private boolean needToReadMore = false;
+
     public SslEngineFrameBuilder(SSLEngine sslEngine, ByteBuffer plainIn, ByteBuffer cipherIn, ReadableByteChannel channel) {
         super(channel, plainIn);
         this.sslEngine = sslEngine;
@@ -40,11 +42,21 @@ public SslEngineFrameBuilder(SSLEngine sslEngine, ByteBuffer plainIn, ByteBuffer
 
     @Override
     protected boolean somethingToRead() throws IOException {
-        if (applicationBuffer.hasRemaining()) {
+        if (applicationBuffer.hasRemaining() && !needToReadMore) {
             return true;
         } else {
             applicationBuffer.clear();
 
+            if (needToReadMore) {
+                int read = NioHelper.read(channel, cipherBuffer);
+                if (read == 0) {
+                    return false;
+                } else {
+                    this.needToReadMore = false;
+                    this.cipherBuffer.flip();
+                }
+            }
+
             while (true) {
                 SSLEngineResult result = sslEngine.unwrap(cipherBuffer, applicationBuffer);
                 switch (result.getStatus()) {
@@ -61,6 +73,7 @@ protected boolean somethingToRead() throws IOException {
                         cipherBuffer.compact();
                         int read = NioHelper.read(channel, cipherBuffer);
                         if (read == 0) {
+                            this.needToReadMore = true;
                             return false;
                         }
                         cipherBuffer.flip();