core/detail/chacha.hpp

0001 //
0002 // Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
0003 //
0004 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0005 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006 //
0007 // Official repository: https://github.com/boostorg/beast
0008 //
0009
0010 //
0011 // This is a derivative work, original copyright follows:
0012 //
0013
0014 /*
0015     Copyright (c) 2015 Orson Peters <orsonpeters@gmail.com>
0016
0017     This software is provided 'as-is', without any express or implied warranty. In no event will the
0018     authors be held liable for any damages arising from the use of this software.
0019
0020     Permission is granted to anyone to use this software for any purpose, including commercial
0021     applications, and to alter it and redistribute it freely, subject to the following restrictions:
0022
0023     1. The origin of this software must not be misrepresented; you must not claim that you wrote the
0024        original software. If you use this software in a product, an acknowledgment in the product
0025        documentation would be appreciated but is not required.
0026
0027     2. Altered source versions must be plainly marked as such, and must not be misrepresented as
0028        being the original software.
0029
0030     3. This notice may not be removed or altered from any source distribution.
0031 */
0032
0033 #ifndef BOOST_BEAST_CORE_DETAIL_CHACHA_HPP
0034 #define BOOST_BEAST_CORE_DETAIL_CHACHA_HPP
0035
0036 #include <cstdint>
0037 #include <limits>
0038
0039 namespace boost {
0040 namespace beast {
0041 namespace detail {
0042
0043 template<std::size_t R>
0044 class chacha
0045 {
0046     alignas(16) std::uint32_t block_[16];
0047     std::uint32_t keysetup_[8];
0048     std::uint64_t ctr_ = 0;
0049     int idx_ = 16;
0050
0051     void generate_block()
0052     {
0053         std::uint32_t constexpr constants[4] = {
0054             0x61707865, 0x3320646e, 0x79622d32, 0x6b206574 };
0055         std::uint32_t input[16];
0056         for (int i = 0; i < 4; ++i)
0057             input[i] = constants[i];
0058         for (int i = 0; i < 8; ++i)
0059             input[4 + i] = keysetup_[i];
0060         input[12] = (ctr_ / 16) & 0xffffffffu;
0061         input[13] = (ctr_ / 16) >> 32;
0062         input[14] = input[15] = 0xdeadbeef; // Could use 128-bit counter.
0063         for (int i = 0; i < 16; ++i)
0064             block_[i] = input[i];
0065         chacha_core();
0066         for (int i = 0; i < 16; ++i)
0067             block_[i] += input[i];
0068     }
0069
0070     void chacha_core()
0071     {
0072         #define BOOST_BEAST_CHACHA_ROTL32(x, n) (((x) << (n)) | ((x) >> (32 - (n))))
0073
0074         #define BOOST_BEAST_CHACHA_QUARTERROUND(x, a, b, c, d) \
0075             x[a] = x[a] + x[b]; x[d] ^= x[a]; x[d] = BOOST_BEAST_CHACHA_ROTL32(x[d], 16); \
0076             x[c] = x[c] + x[d]; x[b] ^= x[c]; x[b] = BOOST_BEAST_CHACHA_ROTL32(x[b], 12); \
0077             x[a] = x[a] + x[b]; x[d] ^= x[a]; x[d] = BOOST_BEAST_CHACHA_ROTL32(x[d],  8); \
0078             x[c] = x[c] + x[d]; x[b] ^= x[c]; x[b] = BOOST_BEAST_CHACHA_ROTL32(x[b],  7)
0079
0080         for (unsigned i = 0; i < R; i += 2)
0081         {
0082             BOOST_BEAST_CHACHA_QUARTERROUND(block_, 0, 4,  8, 12);
0083             BOOST_BEAST_CHACHA_QUARTERROUND(block_, 1, 5,  9, 13);
0084             BOOST_BEAST_CHACHA_QUARTERROUND(block_, 2, 6, 10, 14);
0085             BOOST_BEAST_CHACHA_QUARTERROUND(block_, 3, 7, 11, 15);
0086             BOOST_BEAST_CHACHA_QUARTERROUND(block_, 0, 5, 10, 15);
0087             BOOST_BEAST_CHACHA_QUARTERROUND(block_, 1, 6, 11, 12);
0088             BOOST_BEAST_CHACHA_QUARTERROUND(block_, 2, 7,  8, 13);
0089             BOOST_BEAST_CHACHA_QUARTERROUND(block_, 3, 4,  9, 14);
0090         }
0091
0092         #undef BOOST_BEAST_CHACHA_QUARTERROUND
0093         #undef BOOST_BEAST_CHACHA_ROTL32
0094     }
0095
0096 public:
0097     static constexpr std::size_t state_size = sizeof(chacha::keysetup_);
0098
0099     using result_type = std::uint32_t;
0100
0101     chacha(std::uint32_t const* v, std::uint64_t stream)
0102     {
0103         for (int i = 0; i < 6; ++i)
0104             keysetup_[i] = v[i];
0105         keysetup_[6] = v[6] + (stream & 0xffffffff);
0106         keysetup_[7] = v[7] + ((stream >> 32) & 0xffffffff);
0107     }
0108
0109     std::uint32_t
0110     operator()()
0111     {
0112         if(idx_ == 16)
0113         {
0114             idx_ = 0;
0115             ++ctr_;
0116             generate_block();
0117         }
0118         return block_[idx_++];
0119     }
0120 };
0121
0122 } // detail
0123 } // beast
0124 } // boost
0125
0126 #endif