58 lines
1.4 KiB
C++
58 lines
1.4 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 2015-2018 Danny Robson <danny@nerdcruft.net>
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*/
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#include "hotp.hpp"
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#include <cruft/util/endian.hpp>
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#include <cstring>
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using cruft::crypto::hash::HOTP;
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///////////////////////////////////////////////////////////////////////////////
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HOTP::HOTP (util::view<const char*> _key, uint64_t _counter):
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m_counter (_counter),
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m_hash (_key.template cast<const uint8_t*> ())
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{ ; }
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//-----------------------------------------------------------------------------
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unsigned
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HOTP::value (void)
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{
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union {
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uint64_t number;
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uint8_t bytes[8];
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};
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number = util::htob (m_counter);
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auto res = truncate (m_hash (util::make_cview (bytes)));
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++m_counter;
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return res % 1'000'000;
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}
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//-----------------------------------------------------------------------------
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uint32_t
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HOTP::truncate (SHA1::digest_t d)
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{
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// offset into the digest by the last 4 bits
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size_t o= d[d.size () - 1] & 0x0F;
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// mask the highest bit per the specification
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uint32_t v = (d[o + 0] & 0x7f) << 24 |
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(d[o + 1] & 0xff) << 16 |
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(d[o + 2] & 0xff) << 8 |
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(d[o + 3] & 0xff) << 0;
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return v;
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}
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