Make BA2 extension hash calculation safer (#7784)

components/bsa/ba2dx10file.cpp

@@ -177,7 +177,7 @@ namespace Bsa
             return std::nullopt; // folder not found
 
         uint32_t fileHash = generateHash(fileName);
-        uint32_t extHash = *reinterpret_cast<const uint32_t*>(ext.data() + 1);
+        uint32_t extHash = generateExtensionHash(ext);
         auto iter = it->second.find({ fileHash, extHash });
         if (iter == it->second.end())
             return std::nullopt; // file not found

components/bsa/ba2file.cpp

@@ -46,4 +46,12 @@ namespace Bsa
         return result;
     }
 
+    uint32_t generateExtensionHash(std::string_view extension)
+    {
+        uint32_t result = 0;
+        for (size_t i = 0; i < 4 && i < extension.size() - 1; i++)
+            result |= static_cast<uint8_t>(extension[i + 1]) << (8 * i);
+        return result;
+    }
+
 } // namespace Bsa

components/bsa/ba2file.hpp

@@ -7,6 +7,7 @@
 namespace Bsa
 {
     uint32_t generateHash(const std::string& name);
+    uint32_t generateExtensionHash(std::string_view extension);
 }
 
 #endif

components/bsa/ba2gnrlfile.cpp

@@ -172,7 +172,7 @@ namespace Bsa
             return FileRecord(); // folder not found, return default which has offset of sInvalidOffset
 
         uint32_t fileHash = generateHash(fileName);
-        uint32_t extHash = *reinterpret_cast<const uint32_t*>(ext.data() + 1);
+        uint32_t extHash = generateExtensionHash(ext);
         auto iter = it->second.find({ fileHash, extHash });
         if (iter == it->second.end())
             return FileRecord(); // file not found, return default which has offset of sInvalidOffset