Make the support for unencrypted Wii disc images less broken

These disc images are only used on dev units and not retail units.
There are two important differences compared to normal Wii disc images:

- The data starts 0x8000 bytes into each partition instead of 0x20000
- The data of a partition is stored unencrypted and contains no hashes

Our old implementation was just guesswork and doesn't work at all.
According to testing by GerbilSoft, this commit's implementation
is able to read and extract files in the filesystem correctly,
but the tested game still isn't able to boot. (It's thanks to their
info about unencrypted disc images that I was able to make this commit.)

5 files changed, 65 insertions, 26 deletions

diff --git a/Source/Core/DiscIO/DirectoryBlob.cpp b/Source/Core/DiscIO/DirectoryBlob.cpp
index 61aac73694..8628c50fc0 100644
--- a/Source/Core/DiscIO/DirectoryBlob.cpp
+++ b/Source/Core/DiscIO/DirectoryBlob.cpp
@@ -54,6 +54,8 @@ enum class PartitionType : u32
 // 0xFF is an arbitrarily picked value. Note that we can't use 0x00, because that means NTSC-J
 constexpr u32 INVALID_REGION = 0xFF;
 
+constexpr u32 PARTITION_DATA_OFFSET = 0x20000;
+
 constexpr u8 ENTRY_SIZE = 0x0c;
 constexpr u8 FILE_ENTRY = 0;
 constexpr u8 DIRECTORY_ENTRY = 1;
@@ -508,8 +510,8 @@ void DirectoryBlobReader::SetPartitions(std::vector<PartitionWithType>&& partiti
 
     const u64 partition_data_size = partitions[i].partition.GetDataSize();
     m_partitions.emplace(partition_address, std::move(partitions[i].partition));
-    const u64 unaligned_next_partition_address =
-        VolumeWii::PartitionOffsetToRawOffset(partition_data_size, Partition(partition_address));
+    const u64 unaligned_next_partition_address = VolumeWii::EncryptedPartitionOffsetToRawOffset(
+        partition_data_size, Partition(partition_address), PARTITION_DATA_OFFSET);
     partition_address = Common::AlignUp(unaligned_next_partition_address, 0x10000ull);
   }
   m_data_size = partition_address;
@@ -546,7 +548,6 @@ void DirectoryBlobReader::SetPartitionHeader(const DirectoryBlobPartition& parti
                                           partition_root + "h3.bin");
 
   constexpr u32 PARTITION_HEADER_SIZE = 0x1c;
-  constexpr u32 DATA_OFFSET = 0x20000;
   const u64 data_size = Common::AlignUp(partition.GetDataSize(), 0x7c00) / 0x7c00 * 0x8000;
   m_partition_headers.emplace_back(PARTITION_HEADER_SIZE);
   std::vector<u8>& partition_header = m_partition_headers.back();
@@ -555,7 +556,7 @@ void DirectoryBlobReader::SetPartitionHeader(const DirectoryBlobPartition& parti
   Write32(static_cast<u32>(cert_size), 0x8, &partition_header);
   Write32(static_cast<u32>(cert_offset >> 2), 0x0C, &partition_header);
   Write32(H3_OFFSET >> 2, 0x10, &partition_header);
-  Write32(DATA_OFFSET >> 2, 0x14, &partition_header);
+  Write32(PARTITION_DATA_OFFSET >> 2, 0x14, &partition_header);
   Write32(static_cast<u32>(data_size >> 2), 0x18, &partition_header);
 
   m_nonpartition_contents.Add(partition_address + TICKET_SIZE, partition_header);
diff --git a/Source/Core/DiscIO/DiscExtractor.cpp b/Source/Core/DiscIO/DiscExtractor.cpp
index 7494bd5ab7..eaba17b68a 100644
--- a/Source/Core/DiscIO/DiscExtractor.cpp
+++ b/Source/Core/DiscIO/DiscExtractor.cpp
@@ -361,7 +361,8 @@ bool ExportSystemData(const Volume& volume, const Partition& partition,
     success &= ExportTicket(volume, partition, export_folder + "/ticket.bin");
     success &= ExportTMD(volume, partition, export_folder + "/tmd.bin");
     success &= ExportCertificateChain(volume, partition, export_folder + "/cert.bin");
-    success &= ExportH3Hashes(volume, partition, export_folder + "/h3.bin");
+    if (volume.IsEncryptedAndHashed())
+      success &= ExportH3Hashes(volume, partition, export_folder + "/h3.bin");
   }
 
   return success;
diff --git a/Source/Core/DiscIO/Volume.h b/Source/Core/DiscIO/Volume.h
index f1625a9681..2d800da31a 100644
--- a/Source/Core/DiscIO/Volume.h
+++ b/Source/Core/DiscIO/Volume.h
@@ -58,6 +58,7 @@ public:
     return temp ? static_cast<u64>(*temp) << GetOffsetShift() : std::optional<u64>();
   }
 
+  virtual bool IsEncryptedAndHashed() const { return false; }
   virtual std::vector<Partition> GetPartitions() const { return {}; }
   virtual Partition GetGamePartition() const { return PARTITION_NONE; }
   virtual std::optional<u32> GetPartitionType(const Partition& partition) const { return {}; }
@@ -70,6 +71,10 @@ public:
   virtual const IOS::ES::TMDReader& GetTMD(const Partition& partition) const { return INVALID_TMD; }
   // Returns a non-owning pointer. Returns nullptr if the file system couldn't be read.
   virtual const FileSystem* GetFileSystem(const Partition& partition) const = 0;
+  virtual u64 PartitionOffsetToRawOffset(u64 offset, const Partition& partition) const
+  {
+    return offset;
+  }
   std::string GetGameID() const { return GetGameID(GetGamePartition()); }
   virtual std::string GetGameID(const Partition& partition) const = 0;
   std::string GetMakerID() const { return GetMakerID(GetGamePartition()); }
diff --git a/Source/Core/DiscIO/VolumeWii.cpp b/Source/Core/DiscIO/VolumeWii.cpp
index d4558c0c99..9816b0cb66 100644
--- a/Source/Core/DiscIO/VolumeWii.cpp
+++ b/Source/Core/DiscIO/VolumeWii.cpp
@@ -33,19 +33,13 @@
 
 namespace DiscIO
 {
-constexpr u64 PARTITION_DATA_OFFSET = 0x20000;
-
 VolumeWii::VolumeWii(std::unique_ptr<BlobReader> reader)
     : m_pReader(std::move(reader)), m_game_partition(PARTITION_NONE),
       m_last_decrypted_block(UINT64_MAX)
 {
   ASSERT(m_pReader);
 
-  if (m_pReader->ReadSwapped<u32>(0x60) != u32(0))
-  {
-    // No partitions - just read unencrypted data like with a GC disc
-    return;
-  }
+  m_encrypted = m_pReader->ReadSwapped<u32>(0x60) == u32(0);
 
   for (u32 partition_group = 0; partition_group < 4; ++partition_group)
   {
@@ -118,12 +112,16 @@ VolumeWii::VolumeWii(std::unique_ptr<BlobReader> reader)
         return file_system->IsValid() ? std::move(file_system) : nullptr;
       };
 
+      auto get_data_offset = [this, partition]() -> u64 {
+        return ReadSwappedAndShifted(partition.offset + 0x2b8, PARTITION_NONE).value_or(0);
+      };
+
       m_partitions.emplace(
           partition, PartitionDetails{Common::Lazy<std::unique_ptr<mbedtls_aes_context>>(get_key),
                                       Common::Lazy<IOS::ES::TicketReader>(get_ticket),
                                       Common::Lazy<IOS::ES::TMDReader>(get_tmd),
                                       Common::Lazy<std::unique_ptr<FileSystem>>(get_file_system),
-                                      *partition_type});
+                                      Common::Lazy<u64>(get_data_offset), *partition_type});
     }
   }
 }
@@ -137,14 +135,21 @@ bool VolumeWii::Read(u64 _ReadOffset, u64 _Length, u8* _pBuffer, const Partition
   if (partition == PARTITION_NONE)
     return m_pReader->Read(_ReadOffset, _Length, _pBuffer);
 
-  if (m_pReader->SupportsReadWiiDecrypted())
-    return m_pReader->ReadWiiDecrypted(_ReadOffset, _Length, _pBuffer, partition.offset);
-
-  // Get the decryption key for the partition
   auto it = m_partitions.find(partition);
   if (it == m_partitions.end())
     return false;
-  mbedtls_aes_context* aes_context = it->second.key->get();
+  const PartitionDetails& partition_details = it->second;
+
+  if (!m_encrypted)
+  {
+    return m_pReader->Read(partition.offset + *partition_details.data_offset + _ReadOffset, _Length,
+                           _pBuffer);
+  }
+
+  if (m_pReader->SupportsReadWiiDecrypted())
+    return m_pReader->ReadWiiDecrypted(_ReadOffset, _Length, _pBuffer, partition.offset);
+
+  mbedtls_aes_context* aes_context = partition_details.key->get();
   if (!aes_context)
     return false;
 
@@ -152,8 +157,8 @@ bool VolumeWii::Read(u64 _ReadOffset, u64 _Length, u8* _pBuffer, const Partition
   while (_Length > 0)
   {
     // Calculate offsets
-    u64 block_offset_on_disc =
-        partition.offset + PARTITION_DATA_OFFSET + _ReadOffset / BLOCK_DATA_SIZE * BLOCK_TOTAL_SIZE;
+    u64 block_offset_on_disc = partition.offset + *partition_details.data_offset +
+                               _ReadOffset / BLOCK_DATA_SIZE * BLOCK_TOTAL_SIZE;
     u64 data_offset_in_block = _ReadOffset % BLOCK_DATA_SIZE;
 
     if (m_last_decrypted_block != block_offset_on_disc)
@@ -190,6 +195,11 @@ bool VolumeWii::Read(u64 _ReadOffset, u64 _Length, u8* _pBuffer, const Partition
   return true;
 }
 
+bool VolumeWii::IsEncryptedAndHashed() const
+{
+  return m_encrypted;
+}
+
 std::vector<Partition> VolumeWii::GetPartitions() const
 {
   std::vector<Partition> partitions;
@@ -235,15 +245,29 @@ const FileSystem* VolumeWii::GetFileSystem(const Partition& partition) const
   return it != m_partitions.end() ? it->second.file_system->get() : nullptr;
 }
 
-u64 VolumeWii::PartitionOffsetToRawOffset(u64 offset, const Partition& partition)
+u64 VolumeWii::EncryptedPartitionOffsetToRawOffset(u64 offset, const Partition& partition,
+                                                   u64 partition_data_offset)
 {
   if (partition == PARTITION_NONE)
     return offset;
 
-  return partition.offset + PARTITION_DATA_OFFSET + (offset / BLOCK_DATA_SIZE * BLOCK_TOTAL_SIZE) +
+  return partition.offset + partition_data_offset + (offset / BLOCK_DATA_SIZE * BLOCK_TOTAL_SIZE) +
          (offset % BLOCK_DATA_SIZE);
 }
 
+u64 VolumeWii::PartitionOffsetToRawOffset(u64 offset, const Partition& partition) const
+{
+  auto it = m_partitions.find(partition);
+  if (it == m_partitions.end())
+    return offset;
+  const u64 data_offset = *it->second.data_offset;
+
+  if (!m_encrypted)
+    return partition.offset + data_offset + offset;
+
+  return EncryptedPartitionOffsetToRawOffset(offset, partition, data_offset);
+}
+
 std::string VolumeWii::GetGameID(const Partition& partition) const
 {
   char ID[6];
@@ -357,11 +381,15 @@ u64 VolumeWii::GetRawSize() const
 
 bool VolumeWii::CheckIntegrity(const Partition& partition) const
 {
+  if (!m_encrypted)
+    return false;
+
   // Get the decryption key for the partition
   auto it = m_partitions.find(partition);
   if (it == m_partitions.end())
     return false;
-  mbedtls_aes_context* aes_context = it->second.key->get();
+  const PartitionDetails& partition_details = it->second;
+  mbedtls_aes_context* aes_context = partition_details.key->get();
   if (!aes_context)
     return false;
 
@@ -373,7 +401,7 @@ bool VolumeWii::CheckIntegrity(const Partition& partition) const
   u32 nClusters = (u32)(partDataSize / 0x8000);
   for (u32 clusterID = 0; clusterID < nClusters; ++clusterID)
   {
-    u64 clusterOff = partition.offset + PARTITION_DATA_OFFSET + (u64)clusterID * 0x8000;
+    u64 clusterOff = partition.offset + *partition_details.data_offset + (u64)clusterID * 0x8000;
 
     // Read and decrypt the cluster metadata
     u8 clusterMDCrypted[0x400];
diff --git a/Source/Core/DiscIO/VolumeWii.h b/Source/Core/DiscIO/VolumeWii.h
index a173d17aa7..ede26959f9 100644
--- a/Source/Core/DiscIO/VolumeWii.h
+++ b/Source/Core/DiscIO/VolumeWii.h
@@ -33,6 +33,7 @@ public:
   VolumeWii(std::unique_ptr<BlobReader> reader);
   ~VolumeWii();
   bool Read(u64 _Offset, u64 _Length, u8* _pBuffer, const Partition& partition) const override;
+  bool IsEncryptedAndHashed() const override;
   std::vector<Partition> GetPartitions() const override;
   Partition GetGamePartition() const override;
   std::optional<u32> GetPartitionType(const Partition& partition) const override;
@@ -40,6 +41,9 @@ public:
   const IOS::ES::TicketReader& GetTicket(const Partition& partition) const override;
   const IOS::ES::TMDReader& GetTMD(const Partition& partition) const override;
   const FileSystem* GetFileSystem(const Partition& partition) const override;
+  static u64 EncryptedPartitionOffsetToRawOffset(u64 offset, const Partition& partition,
+                                                 u64 partition_data_offset);
+  u64 PartitionOffsetToRawOffset(u64 offset, const Partition& partition) const override;
   std::string GetGameID(const Partition& partition) const override;
   std::string GetMakerID(const Partition& partition) const override;
   std::optional<u16> GetRevision(const Partition& partition) const override;
@@ -59,8 +63,6 @@ public:
   u64 GetSize() const override;
   u64 GetRawSize() const override;
 
-  static u64 PartitionOffsetToRawOffset(u64 offset, const Partition& partition);
-
   static constexpr unsigned int BLOCK_HEADER_SIZE = 0x0400;
   static constexpr unsigned int BLOCK_DATA_SIZE = 0x7C00;
   static constexpr unsigned int BLOCK_TOTAL_SIZE = BLOCK_HEADER_SIZE + BLOCK_DATA_SIZE;
@@ -75,12 +77,14 @@ private:
     Common::Lazy<IOS::ES::TicketReader> ticket;
     Common::Lazy<IOS::ES::TMDReader> tmd;
     Common::Lazy<std::unique_ptr<FileSystem>> file_system;
+    Common::Lazy<u64> data_offset;
     u32 type;
   };
 
   std::unique_ptr<BlobReader> m_pReader;
   std::map<Partition, PartitionDetails> m_partitions;
   Partition m_game_partition;
+  bool m_encrypted;
 
   mutable u64 m_last_decrypted_block;
   mutable u8 m_last_decrypted_block_data[BLOCK_DATA_SIZE];