//========================================================================
//
// Decrypt.h
//
// Copyright 1996-2003 Glyph & Cog, LLC
//
//========================================================================

//========================================================================
//
// Modified under the Poppler project - http://poppler.freedesktop.org
//
// All changes made under the Poppler project to this file are licensed
// under GPL version 2 or later
//
// Copyright (C) 2008 Julien Rebetez <julien@fhtagn.net>
// Copyright (C) 2009 David Benjamin <davidben@mit.edu>
// Copyright (C) 2012 Fabio D'Urso <fabiodurso@hotmail.it>
// Copyright (C) 2013 Adrian Johnson <ajohnson@redneon.com>
// Copyright (C) 2013, 2018, 2019 Albert Astals Cid <aacid@kde.org>
// Copyright (C) 2013 Thomas Freitag <Thomas.Freitag@alfa.de>
//
// To see a description of the changes please see the Changelog file that
// came with your tarball or type make ChangeLog if you are building from git
//
//========================================================================

#ifndef DECRYPT_H
#define DECRYPT_H

#include "goo/GooString.h"
#include "Object.h"
#include "Stream.h"

//------------------------------------------------------------------------
// Decrypt
//------------------------------------------------------------------------

class Decrypt {
public:

  // Generate a file key.  The <fileKey> buffer must have space for at
  // least 16 bytes.  Checks <ownerPassword> and then <userPassword>
  // and returns true if either is correct.  Sets <ownerPasswordOk> if
  // the owner password was correct.  Either or both of the passwords
  // may be NULL, which is treated as an empty string.
  static bool makeFileKey(int encVersion, int encRevision, int keyLength,
			   const GooString *ownerKey, const GooString *userKey,
			   const GooString *ownerEnc, const GooString *userEnc,
			   int permissions, const GooString *fileID,
			   const GooString *ownerPassword, const GooString *userPassword,
			   unsigned char *fileKey, bool encryptMetadata,
			   bool *ownerPasswordOk);

private:

  static bool makeFileKey2(int encVersion, int encRevision, int keyLength,
			    const GooString *ownerKey, const GooString *userKey,
			    int permissions, const GooString *fileID,
			    const GooString *userPassword, unsigned char *fileKey,
			    bool encryptMetadata);
};

//------------------------------------------------------------------------
// Helper classes
//------------------------------------------------------------------------

/* DecryptRC4State, DecryptAESState, DecryptAES256State are named like this for
 * historical reasons, but they're used for encryption too.
 * In case of decryption, the cbc field in AES and AES-256 contains the previous
 * input block or the CBC initialization vector (IV) if the stream has just been
 * reset). In case of encryption, it always contains the IV, whereas the
 * previous output is kept in buf. The paddingReached field is only used in
 * case of encryption. */
struct DecryptRC4State {
  unsigned char state[256];
  unsigned char x, y;
};

struct DecryptAESState {
  unsigned int w[44];
  unsigned char state[16];
  unsigned char cbc[16];
  unsigned char buf[16];
  bool paddingReached; // encryption only
  int bufIdx;
};

struct DecryptAES256State {
  unsigned int w[60];
  unsigned char state[16];
  unsigned char cbc[16];
  unsigned char buf[16];
  bool paddingReached; // encryption only
  int bufIdx;
};

class BaseCryptStream : public FilterStream {
public:

  BaseCryptStream(Stream *strA, const unsigned char *fileKey, CryptAlgorithm algoA,
                  int keyLength, Ref ref);
  ~BaseCryptStream();
  StreamKind getKind() override { return strCrypt; }
  void reset() override;
  int getChar() override;
  int lookChar() override = 0;
  Goffset getPos() override;
  bool isBinary(bool last) override;
  Stream *getUndecodedStream() override { return this; }
  void setAutoDelete(bool val);

protected:
  CryptAlgorithm algo;
  int objKeyLength;
  unsigned char objKey[32];
  Goffset charactersRead; // so that getPos() can be correct
  int nextCharBuff;   // EOF means not read yet
  bool autoDelete;

  union {
    DecryptRC4State rc4;
    DecryptAESState aes;
    DecryptAES256State aes256;
  } state;
};

//------------------------------------------------------------------------
// EncryptStream / DecryptStream
//------------------------------------------------------------------------

class EncryptStream : public BaseCryptStream {
public:

  EncryptStream(Stream *strA, const unsigned char *fileKey, CryptAlgorithm algoA,
                int keyLength, Ref ref);
  ~EncryptStream();
  void reset() override;
  int lookChar() override;
};

class DecryptStream : public BaseCryptStream {
public:

  DecryptStream(Stream *strA, const unsigned char *fileKey, CryptAlgorithm algoA,
                int keyLength, Ref ref);
  ~DecryptStream();
  void reset() override;
  int lookChar() override;
};
 
//------------------------------------------------------------------------

extern void md5(const unsigned char *msg, int msgLen, unsigned char *digest);

#endif