mirror of
https://github.com/RGBCube/serenity
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119 lines
3 KiB
C++
119 lines
3 KiB
C++
/*
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* Copyright (c) 2020, Ali Mohammad Pur <mpfard@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/ByteReader.h>
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#include <AK/Debug.h>
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#include <AK/Types.h>
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#include <LibCrypto/Authentication/GHash.h>
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namespace {
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static u32 to_u32(u8 const* b)
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{
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return AK::convert_between_host_and_big_endian(ByteReader::load32(b));
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}
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static void to_u8s(u8* b, u32 const* w)
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{
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for (auto i = 0; i < 4; ++i) {
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ByteReader::store(b + i * 4, AK::convert_between_host_and_big_endian(w[i]));
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}
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}
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}
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namespace Crypto::Authentication {
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GHash::TagType GHash::process(ReadonlyBytes aad, ReadonlyBytes cipher)
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{
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u32 tag[4] { 0, 0, 0, 0 };
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auto transform_one = [&](auto& buf) {
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size_t i = 0;
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for (; i < buf.size(); i += 16) {
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if (i + 16 <= buf.size()) {
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for (auto j = 0; j < 4; ++j) {
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tag[j] ^= to_u32(buf.offset(i + j * 4));
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}
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galois_multiply(tag, m_key, tag);
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}
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}
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if (i > buf.size()) {
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u8 buffer[16] = {};
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Bytes buffer_bytes { buffer, 16 };
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buf.slice(i - 16).copy_to(buffer_bytes);
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for (auto j = 0; j < 4; ++j) {
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tag[j] ^= to_u32(buffer_bytes.offset(j * 4));
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}
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galois_multiply(tag, m_key, tag);
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}
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};
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transform_one(aad);
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transform_one(cipher);
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auto aad_bits = 8 * (u64)aad.size();
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auto cipher_bits = 8 * (u64)cipher.size();
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auto high = [](u64 value) -> u32 { return value >> 32; };
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auto low = [](u64 value) -> u32 { return value & 0xffffffff; };
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if constexpr (GHASH_PROCESS_DEBUG) {
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dbgln("AAD bits: {} : {}", high(aad_bits), low(aad_bits));
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dbgln("Cipher bits: {} : {}", high(cipher_bits), low(cipher_bits));
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dbgln("Tag bits: {} : {} : {} : {}", tag[0], tag[1], tag[2], tag[3]);
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}
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tag[0] ^= high(aad_bits);
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tag[1] ^= low(aad_bits);
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tag[2] ^= high(cipher_bits);
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tag[3] ^= low(cipher_bits);
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dbgln_if(GHASH_PROCESS_DEBUG, "Tag bits: {} : {} : {} : {}", tag[0], tag[1], tag[2], tag[3]);
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galois_multiply(tag, m_key, tag);
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TagType digest;
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to_u8s(digest.data, tag);
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return digest;
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}
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/// Galois Field multiplication using <x^127 + x^7 + x^2 + x + 1>.
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/// Note that x, y, and z are strictly BE.
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void galois_multiply(u32 (&z)[4], const u32 (&_x)[4], const u32 (&_y)[4])
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{
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u32 x[4] { _x[0], _x[1], _x[2], _x[3] };
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u32 y[4] { _y[0], _y[1], _y[2], _y[3] };
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__builtin_memset(z, 0, sizeof(z));
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for (ssize_t i = 127; i > -1; --i) {
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if ((y[3 - (i / 32)] >> (i % 32)) & 1) {
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z[0] ^= x[0];
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z[1] ^= x[1];
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z[2] ^= x[2];
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z[3] ^= x[3];
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}
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auto a0 = x[0] & 1;
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x[0] >>= 1;
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auto a1 = x[1] & 1;
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x[1] >>= 1;
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x[1] |= a0 << 31;
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auto a2 = x[2] & 1;
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x[2] >>= 1;
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x[2] |= a1 << 31;
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auto a3 = x[3] & 1;
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x[3] >>= 1;
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x[3] |= a2 << 31;
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if (a3)
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x[0] ^= 0xe1000000;
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}
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}
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}
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