From 6e4bb8daca0321de9ec7dd7a527f74383f2423f4 Mon Sep 17 00:00:00 2001
From: a1denvalu3 <cloudsupper@proton.me>
Date: Sat, 25 Jul 2026 08:26:28 +0200
Subject: [PATCH] Preserve ambiguous raw deflate compatibility

---
 .../com/bitchat/android/protocol/CompressionUtil.kt | 13 +++++++++----
 .../bitchat/android/protocol/BinaryProtocolTest.kt  | 12 ++++++++++++
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/app/src/main/java/com/bitchat/android/protocol/CompressionUtil.kt b/app/src/main/java/com/bitchat/android/protocol/CompressionUtil.kt
index 230b9c7a..aa038abf 100644
--- a/app/src/main/java/com/bitchat/android/protocol/CompressionUtil.kt
+++ b/app/src/main/java/com/bitchat/android/protocol/CompressionUtil.kt
@@ -93,12 +93,17 @@ object CompressionUtil {
 
         return synchronized(decompressionLock) {
             if (looksLikeZlib(compressedData)) {
-                // A structurally valid zlib header selects the legacy wrapped format. Do not
-                // retry size/completion failures as raw deflate: that only doubles attacker work.
-                try {
+                // A raw stream can coincidentally begin with a valid-looking zlib header. The
+                // header therefore only determines which format to try first; any non-exact zlib
+                // result must still fall back to raw under the same size/completion bounds.
+                val zlibResult = try {
                     inflateExact(compressedData, originalSize, nowrap = false)
                 } catch (zlibException: DataFormatException) {
-                    // A raw stream can coincidentally begin with a valid-looking zlib header.
+                    null
+                }
+                if (zlibResult != null) {
+                    zlibResult
+                } else {
                     try {
                         inflateExact(compressedData, originalSize, nowrap = true)
                     } catch (rawException: DataFormatException) {
diff --git a/app/src/test/java/com/bitchat/android/protocol/BinaryProtocolTest.kt b/app/src/test/java/com/bitchat/android/protocol/BinaryProtocolTest.kt
index 6ea31a7e..f6a1042d 100644
--- a/app/src/test/java/com/bitchat/android/protocol/BinaryProtocolTest.kt
+++ b/app/src/test/java/com/bitchat/android/protocol/BinaryProtocolTest.kt
@@ -1139,6 +1139,18 @@ class BinaryProtocolTest {
         assertArrayEquals(payload, decoded!!.payload)
     }
 
+    @Test
+    fun `raw deflate with zlib-looking prefix falls back after non-exact zlib parse`() {
+        val payload = ByteArray(29) { index -> (index + 1).toByte() }
+        val compressed = byteArrayOf(
+            0x08, // non-final raw stored block; also zlib CMF
+            0x1d, 0x00, // LEN = 29; 0x08 0x1d passes the RFC 1950 header check
+            0xe2.toByte(), 0xff.toByte() // one's complement of LEN
+        ) + payload + byteArrayOf(0x03, 0x00) // final empty fixed-Huffman block
+
+        assertArrayEquals(payload, CompressionUtil.decompress(compressed, payload.size))
+    }
+
     @Test
     fun `under-declared zlib expansion is rejected by fallback`() {
         val payload = ByteArray(4_096) { 0x51 }