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199 lines (174 loc) · 6.8 KB
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/*
This file is part of libhttpserver
Copyright (C) 2011-2026 Sebastiano Merlino
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see the file LICENSE in
the distribution; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
// In-tree SHA-256 (FIPS 180-4 / RFC 6234) for the native v3 surface
// (TASK-114, architecture section 4 / DR-V3-001): the SHA-256 variant
// of the documented RFC 7616 Digest algorithms. FIPS 180-4's own
// structure: big-endian words, the 64-word message schedule built
// from the two small sigmas, and the eight-word working register
// chained through the Sigma/Ch/Maj functions.
#if !defined(HTTPSERVER_COMPILATION)
#error "sha256.hpp is internal; only reachable when compiling libhttpserver."
#endif
#ifndef SRC_HTTPSERVER_DETAIL_SHA256_HPP_
#define SRC_HTTPSERVER_DETAIL_SHA256_HPP_
#include <array>
#include <cstddef>
#include <cstdint>
#include <span>
namespace httpserver {
namespace detail {
// Round constants: fractional parts of the cube roots of the first
// 64 primes (FIPS 180-4 section 4.2.2).
inline constexpr std::array<std::uint32_t, 64> k_sha256_k{
0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b,
0x59f111f1, 0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01,
0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7,
0xc19bf174, 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da, 0x983e5152,
0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc,
0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819,
0xd6990624, 0xf40e3585, 0x106aa070, 0x19a4c116, 0x1e376c08,
0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f,
0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
};
inline constexpr std::uint32_t sha256_rotate_right(
std::uint32_t value, int bits) noexcept {
return (value >> bits) | (value << (32 - bits));
}
// The two schedule-expansion sigmas (FIPS 180-4 section 4.1.2).
inline constexpr std::uint32_t sha256_sigma0(std::uint32_t x) noexcept {
return sha256_rotate_right(x, 7) ^ sha256_rotate_right(x, 18)
^ (x >> 3);
}
inline constexpr std::uint32_t sha256_sigma1(std::uint32_t x) noexcept {
return sha256_rotate_right(x, 17) ^ sha256_rotate_right(x, 19)
^ (x >> 10);
}
// The two big-register Sigmas plus Ch and Maj.
inline constexpr std::uint32_t sha256_big_sigma0(
std::uint32_t x) noexcept {
return sha256_rotate_right(x, 2) ^ sha256_rotate_right(x, 13)
^ sha256_rotate_right(x, 22);
}
inline constexpr std::uint32_t sha256_big_sigma1(
std::uint32_t x) noexcept {
return sha256_rotate_right(x, 6) ^ sha256_rotate_right(x, 11)
^ sha256_rotate_right(x, 25);
}
inline constexpr std::uint32_t sha256_choose(std::uint32_t e,
std::uint32_t f,
std::uint32_t g) noexcept {
return (e & f) ^ (~e & g);
}
inline constexpr std::uint32_t sha256_majority(std::uint32_t a,
std::uint32_t b,
std::uint32_t c) noexcept {
return (a & b) ^ (a & c) ^ (b & c);
}
inline std::uint32_t sha256_load_word(const std::byte* p) noexcept {
std::uint32_t word = 0;
for (int i = 0; i < 4; ++i) {
word = (word << 8)
| static_cast<std::uint32_t>(
static_cast<unsigned char>(p[i]));
}
return word;
}
inline void sha256_store_word(std::byte* p,
std::uint32_t word) noexcept {
for (int i = 0; i < 4; ++i) {
p[i] = static_cast<std::byte>((word >> (24 - 8 * i)) & 0xff);
}
}
// One 512-bit block into the eight running state words.
inline void sha256_compress(std::uint32_t (&h)[8],
const std::byte* block) noexcept {
std::uint32_t w[64];
for (int t = 0; t < 16; ++t) {
w[t] = sha256_load_word(block + t * 4);
}
for (int t = 16; t < 64; ++t) {
w[t] = sha256_sigma1(w[t - 2]) + w[t - 7]
+ sha256_sigma0(w[t - 15]) + w[t - 16];
}
std::uint32_t a = h[0];
std::uint32_t b = h[1];
std::uint32_t c = h[2];
std::uint32_t d = h[3];
std::uint32_t e = h[4];
std::uint32_t f = h[5];
std::uint32_t g = h[6];
std::uint32_t hh = h[7];
for (int t = 0; t < 64; ++t) {
const std::uint32_t t1 = hh + sha256_big_sigma1(e)
+ sha256_choose(e, f, g) + k_sha256_k[t] + w[t];
const std::uint32_t t2 =
sha256_big_sigma0(a) + sha256_majority(a, b, c);
hh = g;
g = f;
f = e;
e = d + t1;
d = c;
c = b;
b = a;
a = t1 + t2;
}
h[0] += a;
h[1] += b;
h[2] += c;
h[3] += d;
h[4] += e;
h[5] += f;
h[6] += g;
h[7] += hh;
}
inline std::array<std::byte, 32> sha256(std::span<const std::byte> data) {
std::uint32_t h[8] = {0x6a09e667, 0xbb67ae85, 0x3c6ef372,
0xa54ff53a, 0x510e527f, 0x9b05688c,
0x1f83d9ab, 0x5be0cd19};
std::size_t seen = 0;
while (seen + 64 <= data.size()) {
sha256_compress(h, data.data() + seen);
seen += 64;
}
std::byte tail[128] = {};
const std::size_t leftover = data.size() - seen;
for (std::size_t i = 0; i < leftover; ++i) {
tail[i] = data[seen + i];
}
tail[leftover] = std::byte{0x80};
const std::size_t room = (leftover < 56) ? 64 : 128;
const std::uint64_t bit_total =
static_cast<std::uint64_t>(data.size()) * 8;
for (int i = 0; i < 8; ++i) {
tail[room - 8 + i] =
static_cast<std::byte>((bit_total >> (56 - 8 * i)) & 0xff);
}
sha256_compress(h, tail);
if (room == 128) sha256_compress(h, tail + 64);
std::array<std::byte, 32> digest{};
for (int i = 0; i < 8; ++i) {
sha256_store_word(digest.data() + i * 4, h[i]);
}
return digest;
}
} // namespace detail
} // namespace httpserver
#endif // SRC_HTTPSERVER_DETAIL_SHA256_HPP_