1 files changed, 77 insertions, 0 deletions
diff --git a/NorthstarDLL/exploitfixes_lzss.cpp b/NorthstarDLL/exploitfixes_lzss.cpp
new file mode 100644
index 00000000..cc95246f
--- /dev/null
+++ b/NorthstarDLL/exploitfixes_lzss.cpp
@@ -0,0 +1,77 @@
+#include "pch.h"
+
+AUTOHOOK_INIT()
+
+static constexpr int LZSS_LOOKSHIFT = 4;
+
+struct lzss_header_t
+{
+	unsigned int id;
+	unsigned int actualSize;
+};
+
+// 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.
+AUTOHOOK(CLZSS__SafeDecompress, engine.dll + 0x432A10,
+unsigned int,, (void* self, const unsigned char* pInput, unsigned char* pOutput, unsigned int unBufSize))
+{
+	unsigned int totalBytes = 0;
+	int getCmdByte = 0;
+	int cmdByte = 0;
+
+	lzss_header_t header = *(lzss_header_t*)pInput;
+
+	if (!pInput || !header.actualSize || header.id != 0x53535A4C || 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 0;
+
+	return totalBytes;
+}
+
+ON_DLL_LOAD("engine.dll", ExploitFixes_LZSS, (CModule module))
+{
+	AUTOHOOK_DISPATCH()
+}