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.)

1 files changed, 47 insertions, 19 deletions

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];