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98 lines
2.1 KiB
C++
98 lines
2.1 KiB
C++
#ifndef XRPL_BASICS_HARDENED_HASH_H_INCLUDED
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#define XRPL_BASICS_HARDENED_HASH_H_INCLUDED
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#include <xrpl/beast/hash/hash_append.h>
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#include <xrpl/beast/hash/xxhasher.h>
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#include <cstdint>
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#include <mutex>
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#include <random>
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#include <utility>
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namespace ripple {
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namespace detail {
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using seed_pair = std::pair<std::uint64_t, std::uint64_t>;
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template <bool = true>
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seed_pair
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make_seed_pair() noexcept
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{
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struct state_t
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{
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std::mutex mutex;
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std::random_device rng;
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std::mt19937_64 gen;
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std::uniform_int_distribution<std::uint64_t> dist;
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state_t() : gen(rng())
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{
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}
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// state_t(state_t const&) = delete;
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// state_t& operator=(state_t const&) = delete;
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};
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static state_t state;
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std::lock_guard lock(state.mutex);
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return {state.dist(state.gen), state.dist(state.gen)};
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}
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} // namespace detail
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/**
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* Seed functor once per construction
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A std compatible hash adapter that resists adversarial inputs.
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For this to work, T must implement in its own namespace:
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@code
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template <class Hasher>
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void
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hash_append (Hasher& h, T const& t) noexcept
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{
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// hash_append each base and member that should
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// participate in forming the hash
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using beast::hash_append;
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hash_append (h, static_cast<T::base1 const&>(t));
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hash_append (h, static_cast<T::base2 const&>(t));
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// ...
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hash_append (h, t.member1);
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hash_append (h, t.member2);
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// ...
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}
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@endcode
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Do not use any version of Murmur or CityHash for the Hasher
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template parameter (the hashing algorithm). For details
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see https://131002.net/siphash/#at
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*/
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template <class HashAlgorithm = beast::xxhasher>
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class hardened_hash
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{
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private:
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detail::seed_pair m_seeds;
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public:
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using result_type = typename HashAlgorithm::result_type;
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hardened_hash() : m_seeds(detail::make_seed_pair<>())
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{
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}
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template <class T>
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result_type
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operator()(T const& t) const noexcept
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{
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HashAlgorithm h(m_seeds.first, m_seeds.second);
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hash_append(h, t);
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return static_cast<result_type>(h);
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}
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};
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} // namespace ripple
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#endif
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