// Crypto/WzAes.h
/*
This code implements Brian Gladman's scheme
specified in "A Password Based File Encryption Utility":
  - AES encryption (128,192,256-bit) in Counter (CTR) mode.
  - HMAC-SHA1 authentication for encrypted data (10 bytes)
  - Keys are derived by PPKDF2(RFC2898)-HMAC-SHA1 from ASCII password and
    Salt (saltSize = aesKeySize / 2).
  - 2 bytes contain Password Verifier's Code
*/

#ifndef __CRYPTO_WZ_AES_H
#define __CRYPTO_WZ_AES_H

#include "../../../C/Aes.h"

#include "../../Common/MyBuffer.h"
#include "../../Common/MyCom.h"

#include "../ICoder.h"
#include "../IPassword.h"

#include "HmacSha1.h"

namespace NCrypto {
namespace NWzAes {

/* ICompressFilter::Init() does nothing for this filter.

  Call to init:
    Encoder:
      CryptoSetPassword();
      WriteHeader();
    Decoder:
      [CryptoSetPassword();]
      ReadHeader();
      [CryptoSetPassword();] Init_and_CheckPassword();
      [CryptoSetPassword();] Init_and_CheckPassword();
*/

const UInt32 kPasswordSizeMax = 99; // 128;

const unsigned kSaltSizeMax = 16;
const unsigned kPwdVerifSize = 2;
const unsigned kMacSize = 10;

enum EKeySizeMode
{
  kKeySizeMode_AES128 = 1,
  kKeySizeMode_AES192 = 2,
  kKeySizeMode_AES256 = 3
};

struct CKeyInfo
{
  EKeySizeMode KeySizeMode;
  Byte Salt[kSaltSizeMax];
  Byte PwdVerifComputed[kPwdVerifSize];

  CByteBuffer Password;

  unsigned GetKeySize()  const { return (8 * KeySizeMode + 8); }
  unsigned GetSaltSize() const { return (4 * KeySizeMode + 4); }
  unsigned GetNumSaltWords() const { return (KeySizeMode + 1); }

  CKeyInfo(): KeySizeMode(kKeySizeMode_AES256) {}
};

struct CAesCtr2
{
  unsigned pos;
  unsigned offset;
  UInt32 aes[4 + AES_NUM_IVMRK_WORDS + 3];
  CAesCtr2();
};

void AesCtr2_Init(CAesCtr2 *p);
void AesCtr2_Code(CAesCtr2 *p, Byte *data, SizeT size);

class CBaseCoder:
  public ICompressFilter,
  public ICryptoSetPassword,
  public CMyUnknownImp
{
protected:
  CKeyInfo _key;
  NSha1::CHmac _hmac;
  CAesCtr2 _aes;

  void Init2();
public:
  MY_UNKNOWN_IMP1(ICryptoSetPassword)

  STDMETHOD(CryptoSetPassword)(const Byte *data, UInt32 size);

  STDMETHOD(Init)();
  
  unsigned GetHeaderSize() const { return _key.GetSaltSize() + kPwdVerifSize; }
  unsigned GetAddPackSize() const { return GetHeaderSize() + kMacSize; }

  bool SetKeyMode(unsigned mode)
  {
    if (mode < kKeySizeMode_AES128 || mode > kKeySizeMode_AES256)
      return false;
    _key.KeySizeMode = (EKeySizeMode)mode;
    return true;
  }
};

class CEncoder:
  public CBaseCoder
{
public:
  STDMETHOD_(UInt32, Filter)(Byte *data, UInt32 size);
  HRESULT WriteHeader(ISequentialOutStream *outStream);
  HRESULT WriteFooter(ISequentialOutStream *outStream);
};

class CDecoder:
  public CBaseCoder
  // public ICompressSetDecoderProperties2
{
  Byte _pwdVerifFromArchive[kPwdVerifSize];
public:
  // ICompressSetDecoderProperties2
  // STDMETHOD(SetDecoderProperties2)(const Byte *data, UInt32 size);
  STDMETHOD_(UInt32, Filter)(Byte *data, UInt32 size);
  HRESULT ReadHeader(ISequentialInStream *inStream);
  bool Init_and_CheckPassword();
  HRESULT CheckMac(ISequentialInStream *inStream, bool &isOK);
};

}}

#endif
