82 lines
2.5 KiB
C++
82 lines
2.5 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Copyright 2015 Danny Robson <danny@nerdcruft.net>
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*/
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#ifndef CRUFT_CRYPTO_HASH_HMAC_HPP
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#define CRUFT_CRYPTO_HASH_HMAC_HPP
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#include <cruft/util/debug/assert.hpp>
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#include <cruft/util/view.hpp>
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#include <algorithm>
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#include <utility>
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namespace cruft::crypto::hash {
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template <class HashT>
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/// RFC 2104 key-hashing for message authentication
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class HMAC {
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public:
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using digest_t = typename HashT::digest_t;
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//---------------------------------------------------------------------
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HMAC (cruft::view<const std::uint8_t*> key)
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{
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CHECK (!key.empty ());
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static_assert (sizeof (m_ikey) == sizeof (m_okey), "key padding must match");
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// If the key is larger than the blocklength, use the hash of the key
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if (key.size () > HashT::BLOCK_SIZE) {
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auto d = HashT{} (key);
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auto tail = std::copy (d.begin (), d.end (), m_ikey.begin ());
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std::fill (tail, std::end (m_ikey), 0);
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// Use the key directly
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} else {
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auto tail = std::copy (key.begin (), key.end (), m_ikey.begin ());
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std::fill (tail, m_ikey.end (), 0);
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}
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// copy and xor the key data to the okey
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std::transform (
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std::begin (m_ikey),
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std::end (m_ikey),
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std::begin (m_okey),
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[] (auto v) { return v ^ OFILL; });
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// just xor the ikey in place
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std::transform (
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m_ikey.begin (),
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m_ikey.end (),
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m_ikey.begin (),
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[] (auto v) { return v ^ IFILL; });
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}
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//---------------------------------------------------------------------
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template <typename ...DataT>
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digest_t
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operator() (DataT&&...data) const noexcept
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{
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HashT h;
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return h (m_okey, h (m_ikey, std::forward<DataT> (data)...));
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};
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private:
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//---------------------------------------------------------------------
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static constexpr uint8_t IFILL = 0x36;
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static constexpr uint8_t OFILL = 0x5C;
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std::array<uint8_t,HashT::BLOCK_SIZE> m_ikey;
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std::array<uint8_t,HashT::BLOCK_SIZE> m_okey;
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};
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}
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#endif
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