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/*
* EntropySource
* (C) 2008,2009,2014,2015 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#ifndef BOTAN_ENTROPY_H__
#define BOTAN_ENTROPY_H__
#include <botan/secmem.h>
#include <string>
#include <functional>
namespace Botan {
/**
* Class used to accumulate the poll results of EntropySources
*/
class BOTAN_DLL Entropy_Accumulator final
{
public:
/**
* Initialize an Entropy_Accumulator
*
* @param accum will be called with poll results, first params the data and
* length, the second a best estimate of min-entropy for the entire buffer;
* out of an abundance of caution this will be zero for many sources.
* accum should return true if it wants the polling to stop, though it may
* still be called again a few more times, and should be careful to return
* true then as well.
*/
Entropy_Accumulator(std::function<bool (const byte[], size_t, double)> accum) :
m_accum_fn(accum) {}
/**
* @return if our polling goal has been achieved
*/
bool polling_goal_achieved() const { return m_done; }
bool polling_finished() const { return m_done; }
/**
* Add entropy to the accumulator
* @param bytes the input bytes
* @param length specifies how many bytes the input is
* @param entropy_bits_per_byte is a best guess at how much
* entropy per byte is in this input
*/
void add(const void* bytes, size_t length, double entropy_bits_per_byte)
{
m_done = m_accum_fn(reinterpret_cast<const byte*>(bytes),
length, entropy_bits_per_byte * length) || m_done;
}
/**
* Add entropy to the accumulator
* @param v is some value
* @param entropy_bits_per_byte is a best guess at how much
* entropy per byte is in this input
*/
template<typename T>
void add(const T& v, double entropy_bits_per_byte)
{
add(&v, sizeof(T), entropy_bits_per_byte);
}
secure_vector<byte>& get_io_buf(size_t sz) { m_io_buf.resize(sz); return m_io_buf; }
private:
std::function<bool (const byte[], size_t, double)> m_accum_fn;
secure_vector<byte> m_io_buf;
bool m_done = false;
};
/**
* Abstract interface to a source of entropy
*/
class BOTAN_DLL Entropy_Source
{
public:
/*
* Return a new entropy source of a particular type, or null
* Each entropy source may require substantial resources (eg, a file handle
* or socket instance), so try to share them among multiple RNGs, or just
* use the preconfigured global list accessed by global_entropy_sources()
*/
static std::unique_ptr<Entropy_Source> create(const std::string& type);
/**
* @return name identifying this entropy source
*/
virtual std::string name() const = 0;
/**
* Perform an entropy gathering poll
* @param accum is an accumulator object that will be given entropy
*/
virtual void poll(Entropy_Accumulator& accum) = 0;
virtual ~Entropy_Source() {}
};
class BOTAN_DLL Entropy_Sources final
{
public:
static Entropy_Sources& global_sources();
void add_source(std::unique_ptr<Entropy_Source> src);
std::vector<std::string> enabled_sources() const;
void poll(Entropy_Accumulator& accum);
bool poll_just(Entropy_Accumulator& accum, const std::string& src);
Entropy_Sources() {}
Entropy_Sources(const std::vector<std::string>& sources);
~Entropy_Sources();
private:
std::vector<Entropy_Source*> m_srcs;
};
}
#endif
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