Re-implement FixCommonKeyIndex for WAD files

The old implementation of this was not able to distinguish between
a title that had the common key index set to 1 because it actually
was Korean and a title that had the common key index set to 1 due to
fakesigning. This new implementation solves the problem by
decrypting a content with each possible common key and checking
which result matches the provided SHA-1 hash.

The problem that the old implementation causes has only been reported
to affect a certain pirated WAD of Chronos Twins DX (WC6EUP), but it's
possible that the problem would start affecting more WADs if we add
support for the vWii common key (which uses index 2). Adding support
for the vWii common key would also prevent us from using the simpler
solution of always forcing the index to 0 if the title is not Korean.

1 files changed, 22 insertions, 40 deletions

diff --git a/Source/Core/DiscIO/VolumeVerifier.cpp b/Source/Core/DiscIO/VolumeVerifier.cpp
index 22a732a8ab..06d669ce61 100644
--- a/Source/Core/DiscIO/VolumeVerifier.cpp
+++ b/Source/Core/DiscIO/VolumeVerifier.cpp
@@ -11,7 +11,6 @@
 #include <string>
 #include <unordered_set>
 
-#include <mbedtls/aes.h>
 #include <mbedtls/md5.h>
 #include <mbedtls/sha1.h>
 #include <zlib.h>
@@ -604,29 +603,33 @@ void VolumeVerifier::CheckMisc()
     }
   }
 
-  const IOS::ES::TicketReader& ticket = m_volume.GetTicket(m_volume.GetGamePartition());
-  if (ticket.IsValid())
+  m_ticket = m_volume.GetTicket(m_volume.GetGamePartition());
+  if (m_ticket.IsValid())
   {
-    const u8 common_key = ticket.GetCommonKeyIndex();
+    const u8 specified_common_key_index = m_ticket.GetCommonKeyIndex();
 
-    if (common_key > IOS::HLE::IOSC::COMMON_KEY_HANDLES.size())
+    // Wii discs only use common key 0 (regular) and common key 1 (Korean), not common key 2 (vWii).
+    if (m_volume.GetVolumeType() == Platform::WiiDisc && specified_common_key_index > 1)
     {
-      // Many fakesigned WADs have the common key index set to a (random?) bogus value.
-      // For WADs, Dolphin will detect this and use common key 0 instead, making this low severity.
-      const Severity severity =
-          m_volume.GetVolumeType() == Platform::WiiWAD ? Severity::Low : Severity::High;
-      // i18n: This is "common" as in "shared", not the opposite of "uncommon"
-      AddProblem(severity, Common::GetStringT("This title is set to use an invalid common key."));
+      AddProblem(Severity::High,
+                 // i18n: This is "common" as in "shared", not the opposite of "uncommon"
+                 Common::GetStringT("This title is set to use an invalid common key."));
     }
 
-    if (common_key == 1 && region != Region::NTSC_K)
+    if (m_volume.GetVolumeType() == Platform::WiiWAD)
     {
-      // Apparently a certain pirate WAD of Chronos Twins DX unluckily got an index of 1,
-      // which Dolphin does not change to 0 because 1 is valid on Korean Wiis.
-      // https://forums.dolphin-emu.org/Thread-wiiware-chronos-twins-dx
-      AddProblem(Severity::High,
-                 // i18n: This is "common" as in "shared", not the opposite of "uncommon"
-                 Common::GetStringT("This non-Korean title is set to use the Korean common key."));
+      m_ticket = m_volume.GetTicketWithFixedCommonKey();
+      const u8 fixed_common_key_index = m_ticket.GetCommonKeyIndex();
+      if (specified_common_key_index != fixed_common_key_index)
+      {
+        // Many fakesigned WADs have the common key index set to a (random?) bogus value.
+        // For WADs, Dolphin will detect this and use the correct key, making this low severity.
+        std::string text = StringFromFormat(
+            // i18n: This is "common" as in "shared", not the opposite of "uncommon"
+            Common::GetStringT("The specified common key index is %u but should be %u.").c_str(),
+            specified_common_key_index, fixed_common_key_index);
+        AddProblem(Severity::Low, std::move(text));
+      }
     }
   }
 
@@ -737,7 +740,7 @@ void VolumeVerifier::Process()
 
   if (content_read)
   {
-    if (!CheckContentIntegrity(content))
+    if (!m_volume.CheckContentIntegrity(content, m_content_offsets[m_content_index], m_ticket))
     {
       AddProblem(
           Severity::High,
@@ -768,27 +771,6 @@ void VolumeVerifier::Process()
   }
 }
 
-bool VolumeVerifier::CheckContentIntegrity(const IOS::ES::Content& content)
-{
-  std::vector<u8> encrypted_data = m_volume.GetContent(content.index);
-
-  mbedtls_aes_context context;
-  const std::array<u8, 16> key = m_volume.GetTicket(PARTITION_NONE).GetTitleKey();
-  mbedtls_aes_setkey_dec(&context, key.data(), 128);
-
-  std::array<u8, 16> iv{};
-  iv[0] = static_cast<u8>(content.index >> 8);
-  iv[1] = static_cast<u8>(content.index & 0xFF);
-
-  std::vector<u8> decrypted_data(Common::AlignUp(content.size, 0x40));
-  mbedtls_aes_crypt_cbc(&context, MBEDTLS_AES_DECRYPT, decrypted_data.size(), iv.data(),
-                        encrypted_data.data(), decrypted_data.data());
-
-  std::array<u8, 20> sha1;
-  mbedtls_sha1_ret(decrypted_data.data(), content.size, sha1.data());
-  return sha1 == content.sha1;
-}
-
 u64 VolumeVerifier::GetBytesProcessed() const
 {
   return m_progress;