//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2012, 2013 Ripple Labs Inc.

    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.

    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================

#include <ripple/basics/contract.h>
#include <ripple/crypto/csprng.h>
#include <array>
#include <cassert>
#include <openssl/rand.h>
#include <random>
#include <stdexcept>

namespace ripple {

csprng_engine::csprng_engine()
{
    // This is not strictly necessary
    if (RAND_poll() != 1)
        Throw<std::runtime_error>("CSPRNG: Initial polling failed");
}

csprng_engine::~csprng_engine()
{
    // This cleanup function is not needed in newer versions of OpenSSL
#if (OPENSSL_VERSION_NUMBER < 0x10100000L)
    RAND_cleanup();
#endif
}

void
csprng_engine::mix_entropy(void* buffer, std::size_t count)
{
    std::array<std::random_device::result_type, 128> entropy;

    {
        // On every platform we support, std::random_device
        // is non-deterministic and should provide some good
        // quality entropy.
        std::random_device rd;

        for (auto& e : entropy)
            e = rd();
    }

    std::lock_guard lock(mutex_);

    // We add data to the pool, but we conservatively assume that
    // it contributes no actual entropy.
    RAND_add(
        entropy.data(),
        entropy.size() * sizeof(std::random_device::result_type),
        0);

    if (buffer != nullptr && count != 0)
        RAND_add(buffer, count, 0);
}

void
csprng_engine::operator()(void* ptr, std::size_t count)
{
    // RAND_bytes is thread-safe on OpenSSL 1.1.0 and later when compiled
    // with thread support, so we don't need to grab a mutex.
    // https://mta.openssl.org/pipermail/openssl-users/2020-November/013146.html
#if (OPENSSL_VERSION_NUMBER < 0x10100000L) || !defined(OPENSSL_THREADS)
    std::lock_guard lock(mutex_);
#endif

    auto const result =
        RAND_bytes(reinterpret_cast<unsigned char*>(ptr), count);

    if (result != 1)
        Throw<std::runtime_error>("CSPRNG: Insufficient entropy");
}

csprng_engine::result_type
csprng_engine::operator()()
{
    result_type ret;
    (*this)(&ret, sizeof(result_type));
    return ret;
}

csprng_engine&
crypto_prng()
{
    static csprng_engine engine;
    return engine;
}

}  // namespace ripple