DiscIO: Only allow alphanumeric ASCII in game IDs

We often use game IDs in paths, so we should try to make sure path
traversal is impossible in game IDs. Admittedly, doing any kind of real
attack using the six bytes available in game IDs is unrealistic, but no
game ID should contain non-alphanumeric or non-ASCII characters anyway.

Might also fix https://bugs.dolphin-emu.org/issues/13982 by skipping
converting between encodings for game IDs.

1 files changed, 13 insertions, 0 deletions

diff --git a/Source/Core/DiscIO/Volume.cpp b/Source/Core/DiscIO/Volume.cpp
index 7ef63f6950..c1942b2aeb 100644
--- a/Source/Core/DiscIO/Volume.cpp
+++ b/Source/Core/DiscIO/Volume.cpp
@@ -8,6 +8,7 @@
 #include <map>
 #include <memory>
 #include <optional>
+#include <ranges>
 #include <span>
 #include <string>
 #include <type_traits>
@@ -43,6 +44,18 @@ std::string Volume::DecodeString(std::span<const char> data) const
   return GetRegion() == Region::NTSC_J ? SHIFTJISToUTF8(string) : CP1252ToUTF8(string);
 }
 
+std::string Volume::FilterGameID(std::span<const char> data)
+{
+  std::string string(data.data(), data.size());
+
+  // We don't want game IDs to contain characters that are unprintable or might cause path
+  // traversal. Game IDs normally only contain ASCII uppercase letters and numbers,
+  // but GNHE5d contains a lowercase letter, so let's allow all ASCII letters and numbers.
+  std::ranges::replace_if(string, std::not_fn(Common::IsAlnum), '-');
+
+  return string;
+}
+
 template <typename T>
 static void AddToSyncHash(Common::SHA1::Context* context, const T& data)
 {