From 0af11d75c33ea37ef6cb4d01596c19f57f22ced1 Mon Sep 17 00:00:00 2001
From: Graham <gpe@openrs2.dev>
Date: Mon, 31 Aug 2020 09:28:09 +0100
Subject: [PATCH] Add flag to disable encryption of uncompressed containers by
 default

These don't work in the 550 client due to a bug.

Signed-off-by: Graham <gpe@openrs2.dev>
---
 .../java/dev/openrs2/cache/Js5Compression.kt  | 39 +++++++++++++++----
 .../dev/openrs2/cache/Js5CompressionTest.kt   | 21 ++++++++++
 2 files changed, 53 insertions(+), 7 deletions(-)

diff --git a/cache/src/main/java/dev/openrs2/cache/Js5Compression.kt b/cache/src/main/java/dev/openrs2/cache/Js5Compression.kt
index d110b4e2..3b6d40cf 100644
--- a/cache/src/main/java/dev/openrs2/cache/Js5Compression.kt
+++ b/cache/src/main/java/dev/openrs2/cache/Js5Compression.kt
@@ -49,14 +49,39 @@ public object Js5Compression {
         }
     }
 
-    public fun compressBest(input: ByteBuf, enableLzma: Boolean = false, key: XteaKey = XteaKey.ZERO): ByteBuf {
-        var best = compress(input.slice(), Js5CompressionType.NONE, key)
-        try {
-            for (type in Js5CompressionType.values()) {
-                if (type == Js5CompressionType.NONE || (type == Js5CompressionType.LZMA && !enableLzma)) {
-                    continue
-                }
+    public fun compressBest(
+        input: ByteBuf,
+        enableLzma: Boolean = false,
+        enableUncompressedEncryption: Boolean = false,
+        key: XteaKey = XteaKey.ZERO
+    ): ByteBuf {
+        val types = mutableListOf(Js5CompressionType.BZIP2, Js5CompressionType.GZIP)
+        if (enableLzma) {
+            types += Js5CompressionType.LZMA
+        }
+        if (enableUncompressedEncryption || key.isZero) {
+            /*
+             * The 550 client doesn't strip the 2 byte version trailer before
+             * passing a group to the XTEA decryption function. This causes the
+             * last block to be incorrectly decrypt in many cases (depending
+             * on the length of the group mod the XTEA block size).
+             *
+             * This doesn't cause any problems with the client's GZIP/BZIP2
+             * implementations, as the last block is always part of the trailer
+             * and the trailer isn't checked. However, it would corrupt the
+             * last block of an unencrypted group.
+             *
+             * TODO(gpe): are there any clients with LZMA support _and_ the
+             * decryption bug? Could the enableLzma flag be re-used for
+             * enableNoneWithKey? Or should LZMA also be disabled in clients
+             * with the decryption bug?
+             */
+            types += Js5CompressionType.NONE
+        }
 
+        var best = compress(input.slice(), types.first(), key)
+        try {
+            for (type in types.drop(1)) {
                 compress(input.slice(), type, key).use { output ->
                     if (output.readableBytes() < best.readableBytes()) {
                         best.release()
diff --git a/cache/src/test/java/dev/openrs2/cache/Js5CompressionTest.kt b/cache/src/test/java/dev/openrs2/cache/Js5CompressionTest.kt
index 2151283d..723e4fd1 100644
--- a/cache/src/test/java/dev/openrs2/cache/Js5CompressionTest.kt
+++ b/cache/src/test/java/dev/openrs2/cache/Js5CompressionTest.kt
@@ -234,6 +234,27 @@ object Js5CompressionTest {
         }
     }
 
+    @Test
+    fun testUncompressedEncryption() {
+        Unpooled.wrappedBuffer("OpenRS2".toByteArray()).use { buf ->
+            Js5Compression.compressBest(buf.slice()).use { compressed ->
+                assertEquals(Js5CompressionType.NONE.ordinal, compressed.getUnsignedByte(0).toInt())
+            }
+
+            Js5Compression.compressBest(buf.slice(), enableUncompressedEncryption = true).use { compressed ->
+                assertEquals(Js5CompressionType.NONE.ordinal, compressed.getUnsignedByte(0).toInt())
+            }
+
+            Js5Compression.compressBest(buf.slice(), key = KEY).use { compressed ->
+                assertNotEquals(Js5CompressionType.NONE.ordinal, compressed.getUnsignedByte(0).toInt())
+            }
+
+            Js5Compression.compressBest(buf.slice(), key = KEY, enableUncompressedEncryption = true).use { compressed ->
+                assertEquals(Js5CompressionType.NONE.ordinal, compressed.getUnsignedByte(0).toInt())
+            }
+        }
+    }
+
     private fun read(name: String): ByteBuf {
         Js5CompressionTest::class.java.getResourceAsStream("compression/$name").use { input ->
             return Unpooled.wrappedBuffer(input.readAllBytes())