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VolumeWiiCrypted: Decryption optimization 

The block doesn't have to be read if it already is in m_pBuffer.
This commit is contained in:
JosJuice 2015-01-26 15:59:25 +01:00
parent 7df55d220f
commit 521ccd7b44
2 changed files with 18 additions and 14 deletions
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30
Source/Core/DiscIO/VolumeWiiCrypted.cpp
View File

@ -47,7 +47,6 @@ bool CVolumeWiiCrypted::ChangePartition(u64 offset)
return true; return true;
} }
CVolumeWiiCrypted::~CVolumeWiiCrypted() CVolumeWiiCrypted::~CVolumeWiiCrypted()
{ {
delete[] m_pBuffer; delete[] m_pBuffer;
@ -66,36 +65,41 @@ bool CVolumeWiiCrypted::Read(u64 _ReadOffset, u64 _Length, u8* _pBuffer, bool de
while (_Length > 0) while (_Length > 0)
{ {
static unsigned char IV[16]; // Calculate block offset
// math block offset
u64 Block = _ReadOffset / 0x7C00; u64 Block = _ReadOffset / 0x7C00;
u64 Offset = _ReadOffset % 0x7C00; u64 Offset = _ReadOffset % 0x7C00;
// read current block
if (!m_pReader->Read(m_VolumeOffset + m_dataOffset + Block * 0x8000, 0x8000, m_pBuffer))
return(false);
if (m_LastDecryptedBlockOffset != Block) if (m_LastDecryptedBlockOffset != Block)
{ {
memcpy(IV, m_pBuffer + 0x3d0, 16); // Read the current block
aes_crypt_cbc(m_AES_ctx.get(), AES_DECRYPT, 0x7C00, IV, m_pBuffer + 0x400, m_LastDecryptedBlock); if (!m_pReader->Read(m_VolumeOffset + m_dataOffset + Block * 0x8000, 0x8000, m_pBuffer))
return false;
// Decrypt the block's data.
// 0x3D0 - 0x3DF in m_pBuffer will be overwritten,
// but that won't affect anything, because we won't
// use the content of m_pBuffer anymore after this
aes_crypt_cbc(m_AES_ctx.get(), AES_DECRYPT, 0x7C00, m_pBuffer + 0x3D0, m_pBuffer + 0x400, m_LastDecryptedBlock);
m_LastDecryptedBlockOffset = Block; m_LastDecryptedBlockOffset = Block;
// The only thing we currently use from the 0x000 - 0x3FF part
// of the block is the IV (at 0x3D0), but it also contains SHA-1
// hashes that IOS uses to check that discs aren't tampered with.
// http://wiibrew.org/wiki/Wii_Disc#Encrypted
} }
// copy the encrypted data // Copy the decrypted data
u64 MaxSizeToCopy = 0x7C00 - Offset; u64 MaxSizeToCopy = 0x7C00 - Offset;
u64 CopySize = (_Length > MaxSizeToCopy) ? MaxSizeToCopy : _Length; u64 CopySize = (_Length > MaxSizeToCopy) ? MaxSizeToCopy : _Length;
memcpy(_pBuffer, &m_LastDecryptedBlock[Offset], (size_t)CopySize); memcpy(_pBuffer, &m_LastDecryptedBlock[Offset], (size_t)CopySize);
// increase buffers // Update offsets
_Length -= CopySize; _Length -= CopySize;
_pBuffer += CopySize; _pBuffer += CopySize;
_ReadOffset += CopySize; _ReadOffset += CopySize;
} }
return(true); return true;
} }
bool CVolumeWiiCrypted::GetTitleID(u8* _pBuffer) const bool CVolumeWiiCrypted::GetTitleID(u8* _pBuffer) const

2
Source/Core/DiscIO/VolumeWiiCrypted.h
View File

@ -53,7 +53,7 @@ private:
u64 m_dataOffset; u64 m_dataOffset;
mutable u64 m_LastDecryptedBlockOffset; mutable u64 m_LastDecryptedBlockOffset;
mutable unsigned char m_LastDecryptedBlock[0x8000]; mutable unsigned char m_LastDecryptedBlock[0x7C00];
}; };
} // namespace } // namespace