SecureRandom.h

 
#pragma once
#include <type_traits>
#include <memory>
#include <cassert>
#include <cstdint>
 
namespace Aws
{
    namespace Utils
    {
        namespace Crypto
        {
            class SecureRandomBytes
            {
            public:
                SecureRandomBytes() : m_failure(false)
                {
                }
 
                virtual ~SecureRandomBytes() = default;
 
                virtual void GetBytes(unsigned char* buffer, size_t bufferSize) = 0;
 
                operator bool() const { return !m_failure; }
 
            protected:
                bool m_failure;
            };
 
            template <typename DataType = uint64_t>
            class SecureRandom
            {
            public:
                SecureRandom(const std::shared_ptr<SecureRandomBytes>& entropySource) : m_entropy(entropySource)
                    { static_assert(std::is_unsigned<DataType>::value, "Type DataType must be integral"); }
 
                virtual ~SecureRandom() = default;
 
                virtual void Reset() {}
 
                virtual DataType operator()()
                {
                    DataType value(0);
                    unsigned char buffer[sizeof(DataType)];
                    m_entropy->GetBytes(buffer, sizeof(DataType));
 
                    assert(*m_entropy);
                    if(*m_entropy)
                    {
                        for (size_t i = 0; i < sizeof(DataType); ++i)
                        {
                             value <<= 8;
                             value |= buffer[i];
 
                        }
                    }
 
                    return value;
                }
 
                operator bool() const { return *m_entropy; }
 
            private:
                std::shared_ptr<SecureRandomBytes> m_entropy;
            };           
 
            class SecureRandomFactory
            {
            public:
                virtual ~SecureRandomFactory() = default;
 
                virtual std::shared_ptr<SecureRandomBytes> CreateImplementation() const = 0;
 
                virtual void InitStaticState() {}
 
                virtual void CleanupStaticState() {}
            };
        }
    }
}