Move LZSS exploit segfault fix hook to ExploitFixes.cpp (#195)

* Move LZSS exploit fix hook to ExploitFixes.cpp

* Formatting changes for clang-format

1 files changed, 77 insertions, 0 deletions

diff --git a/NorthstarDedicatedTest/ExploitFixes.cpp b/NorthstarDedicatedTest/ExploitFixes.cpp
index af7d48ac..84ccc997 100644
--- a/NorthstarDedicatedTest/ExploitFixes.cpp
+++ b/NorthstarDedicatedTest/ExploitFixes.cpp
@@ -365,6 +365,83 @@ static void* GetEntByIndexHook(int idx)
 	return GetEntByIndex(idx);
 }
 
+// RELOCATED FROM https://github.com/R2Northstar/NorthstarLauncher/commit/25dbf729cfc75107a0fcf0186924b58ecc05214b
+// Rewrite of CLZSS::SafeUncompress to fix a vulnerability where malicious compressed payloads could cause the decompressor to try to read
+// out of the bounds of the output buffer.
+KHOOK(
+	LZSS_SafeUncompress,
+	("engine.dll", "48 89 5C 24 ? 48 89 6C 24 ? 48 89 74 24 ? 48 89 7C 24 ? 33 ED 41 8B F9"),
+	uint32_t,
+	__fastcall,
+	(void* self, const unsigned char* pInput, unsigned char* pOutput, unsigned int unBufSize))
+{
+	static constexpr int LZSS_LOOKSHIFT = 4;
+
+	uint32_t totalBytes = 0;
+	int getCmdByte = 0, cmdByte = 0;
+
+	struct lzss_header_t
+	{
+		uint32_t id, actualSize;
+	};
+
+	lzss_header_t header = *(lzss_header_t*)pInput;
+
+	if (pInput == NULL || header.id != 'SSZL' || header.actualSize == 0 || header.actualSize > unBufSize)
+		return 0;
+
+	pInput += sizeof(lzss_header_t);
+
+	for (;;)
+	{
+		if (!getCmdByte)
+			cmdByte = *pInput++;
+
+		getCmdByte = (getCmdByte + 1) & 0x07;
+
+		if (cmdByte & 0x01)
+		{
+			int position = *pInput++ << LZSS_LOOKSHIFT;
+			position |= (*pInput >> LZSS_LOOKSHIFT);
+			position += 1;
+
+			int count = (*pInput++ & 0x0F) + 1;
+			if (count == 1)
+				break;
+
+			// Ensure reference chunk exists entirely within our buffer
+			if (position > totalBytes)
+				return 0;
+
+			totalBytes += count;
+			if (totalBytes > unBufSize)
+				return 0;
+
+			unsigned char* pSource = pOutput - position;
+			for (int i = 0; i < count; i++)
+				*pOutput++ = *pSource++;
+		}
+		else
+		{
+			totalBytes++;
+			if (totalBytes > unBufSize)
+				return 0;
+
+			*pOutput++ = *pInput++;
+		}
+		cmdByte = cmdByte >> 1;
+	}
+
+	if (totalBytes == header.actualSize)
+	{
+		return totalBytes;
+	}
+	else
+	{
+		return 0;
+	}
+}
+
 //////////////////////////////////////////////////
 
 void DoBytePatches()