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Diffstat (limited to 'NorthstarDLL/exploitfixes_lzss.cpp')
-rw-r--r--NorthstarDLL/exploitfixes_lzss.cpp79
1 files changed, 79 insertions, 0 deletions
diff --git a/NorthstarDLL/exploitfixes_lzss.cpp b/NorthstarDLL/exploitfixes_lzss.cpp
new file mode 100644
index 00000000..4205133a
--- /dev/null
+++ b/NorthstarDLL/exploitfixes_lzss.cpp
@@ -0,0 +1,79 @@
+#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.
+// clang-format off
+AUTOHOOK(CLZSS__SafeDecompress, engine.dll + 0x432A10,
+unsigned int, __fastcall, (void* self, const unsigned char* pInput, unsigned char* pOutput, unsigned int unBufSize))
+// clang-format on
+{
+ 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()
+}