ayobfs.h

/* --------------------------------- ABOUT -------------------------------------

   Original Author: Adam Yaxley
Website: https://github.com/adamyaxley
License: See end of file

Obfuscate
Guaranteed compile-time string literal obfuscation library for C++14

Usage:
Pass string literals into the AY_OBFUSCATE macro to obfuscate them at compile
time. AY_OBFUSCATE returns a reference to an ay::obfuscated_data object with the
following traits:
- Guaranteed obfuscation of string
The passed string is encrypted with a simple XOR cipher at compile-time to
prevent it being viewable in the binary image
- Global lifetime
The actual instantiation of the ay::obfuscated_data takes place inside a
lambda as a function level static
- Implicitly convertable to a char*
This means that you can pass it directly into functions that would normally
take a char* or a const char*

Example:
const char* obfuscated_string = AY_OBFUSCATE("Hello World");
std::cout << obfuscated_string << std::endl;

----------------------------------------------------------------------------- */

#ifndef AY_OBFUSCATE_DEFAULT_KEY
// The default 64 bit key to obfuscate strings with.
// This can be user specified by defining AY_OBFUSCATE_DEFAULT_KEY before
// including obfuscate.h
#define AY_OBFUSCATE_DEFAULT_KEY ay::generate_key(__LINE__)
#endif

#define _ROR(x, d) (((x)>>(d))|((x)<<(sizeof(void*)*8-(d))))
#define ENCRYPT_PTR(p) (_ROR((uintptr_t)(p), 13))
#define DECRYPT_PTR(p) ((void*)_ROR((uintptr_t)(p), sizeof(void*)*8-13))

namespace ay
{
  using size_type = unsigned long long;
  using key_type = unsigned long long;

  // Generate a pseudo-random key that spans all 8 bytes
  constexpr key_type generate_key(key_type seed)
  {
    // Use the MurmurHash3 64-bit finalizer to hash our seed
    key_type key = seed;
    key ^= (key >> 33);
    key *= 0xff51afd7ed558ccd;
    key ^= (key >> 33);
    key *= 0xc4ceb9fe1a85ec53;
    key ^= (key >> 33);

    // Make sure that a bit in each byte is set
    key |= 0x0101010101010101ull;

    return key;
  }

  // Obfuscates or deobfuscates data with key
  constexpr void cipher(char* data, size_type size, key_type key)
  {
    // Obfuscate with a simple XOR cipher based on key
    for (size_type i = 0; i < size; i++)
    {
      data[i] ^= char(key >> ((i % 8) * 8));
    }
  }

  // Obfuscates a string at compile time
  template <size_type N, key_type KEY>
    class obfuscator
    {
      public:
        // Obfuscates the string 'data' on construction
        constexpr obfuscator(const char* data)
        {
          // Copy data
          for (size_type i = 0; i < N; i++)
          {
            m_data[i] = data[i];
          }

          // On construction each of the characters in the string is
          // obfuscated with an XOR cipher based on key
          cipher(m_data, N, KEY);
        }

        constexpr const char* data() const
        {
          return &m_data[0];
        }

        constexpr size_type size() const
        {
          return N;
        }

        constexpr key_type key() const
        {
          return KEY;
        }

      private:

        char m_data[N]{};
    };

  // Handles decryption and re-encryption of an encrypted string at runtime
  template <size_type N, key_type KEY>
    class obfuscated_data
    {
      public:
        obfuscated_data(const obfuscator<N, KEY>& obfuscator)
        {
          // Copy obfuscated data
          for (size_type i = 0; i < N; i++)
          {
            m_data[i] = obfuscator.data()[i];
          }
        }

        ~obfuscated_data()
        {
          // Zero m_data to remove it from memory
          for (size_type i = 0; i < N; i++)
          {
            m_data[i] = 0;
          }
          if (m_ptr){
            free(DECRYPT_PTR(m_ptr));
            m_ptr = 0;
          }
        }

        // Returns a pointer to the plain text string, decrypting it if
        // necessary
        inline operator char*()
        {
          decrypt();
          return (char*)DECRYPT_PTR(m_ptr);
        }

        // Manually decrypt the string
        inline void decrypt()
        {
          if (!m_ptr)
          {
            char* ret = (char*)malloc(N);
            memcpy(ret, m_data, N); 
            cipher(ret, N, KEY);
            m_ptr = ENCRYPT_PTR(ret);
          }
        }

      private:

        // Local storage for the string. Call is_encrypted() to check whether or
        // not the string is currently obfuscated.
        char m_data[N];

        // Whether data is currently encrypted
        // bool m_encrypted{ true };
        uintptr_t m_ptr {0};
    };

  // This function exists purely to extract the number of elements 'N' in the
  // array 'data'
  template <size_type N, key_type KEY = AY_OBFUSCATE_DEFAULT_KEY>
    constexpr auto make_obfuscator(const char(&data)[N])
    {
      return obfuscator<N, KEY>(data);
    }
}

// Obfuscates the string 'data' at compile-time and returns a reference to a
// ay::obfuscated_data object with global lifetime that has functions for
// decrypting the string and is also implicitly convertable to a char*
#define AY_OBFUSCATE(data) AY_OBFUSCATE_KEY(data, AY_OBFUSCATE_DEFAULT_KEY)

// Obfuscates the string 'data' with 'key' at compile-time and returns a
// reference to a ay::obfuscated_data object with global lifetime that has
// functions for decrypting the string and is also implicitly convertable to a
// char*
#define AY_OBFUSCATE_KEY(data, key) \
  []() -> ay::obfuscated_data<sizeof(data)/sizeof(data[0]), key>& { \
    static_assert(sizeof(decltype(key)) == sizeof(ay::key_type), "key must be a 64 bit unsigned integer"); \
    static_assert((key) >= (1ull << 56), "key must span all 8 bytes"); \
    constexpr auto n = sizeof(data)/sizeof(data[0]); \
    constexpr auto obfuscator = ay::make_obfuscator<n, key>(data); \
    static auto obfuscated_data = ay::obfuscated_data<n, key>(obfuscator); \
    return obfuscated_data; \
  }()

/* -------------------------------- LICENSE ------------------------------------

   Public Domain (http://www.unlicense.org)

   This is free and unencumbered software released into the public domain.

   Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
   software, either in source code form or as a compiled binary, for any purpose,
   commercial or non-commercial, and by any means.

   In jurisdictions that recognize copyright laws, the author or authors of this
   software dedicate any and all copyright interest in the software to the public
   domain. We make this dedication for the benefit of the public at large and to
   the detriment of our heirs and successors. We intend this dedication to be an
   overt act of relinquishment in perpetuity of all present and future rights to
   this software under copyright law.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
   FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE
   LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
   CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
   SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

   ----------------------------------------------------------------------------- */