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93 lines
2.0 KiB
C++
93 lines
2.0 KiB
C++
#pragma once
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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 xrpl {
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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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makeSeedPair() noexcept
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{
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struct StateT
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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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StateT() : 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 StateT kSTATE;
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std::scoped_lock const lock(kSTATE.mutex);
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return {kSTATE.dist(kSTATE.gen), kSTATE.dist(kSTATE.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 HardenedHash
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{
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private:
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detail::seed_pair seeds_{detail::makeSeedPair<>()};
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public:
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using result_type = typename HashAlgorithm::result_type;
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HardenedHash() = default;
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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(seeds_.first, 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 xrpl
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