327 lines
13 KiB
C
327 lines
13 KiB
C
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// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_HASH_MD5_CONSTEXPR_INTERNAL_H_
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#define BASE_HASH_MD5_CONSTEXPR_INTERNAL_H_
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#include <array>
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#include <cstddef>
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#include <cstdint>
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#include "base/hash/md5.h"
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#include "base/logging.h"
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namespace base {
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namespace internal {
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// The implementation here is based on the pseudocode provided by Wikipedia:
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// https://en.wikipedia.org/wiki/MD5#Pseudocode
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struct MD5CE {
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//////////////////////////////////////////////////////////////////////////////
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// DATA STRUCTURES
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// The data representation at each round is a 4-tuple of uint32_t.
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struct IntermediateData {
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uint32_t a;
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uint32_t b;
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uint32_t c;
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uint32_t d;
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};
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// The input data for a single round consists of 16 uint32_t (64 bytes).
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using RoundData = std::array<uint32_t, 16>;
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//////////////////////////////////////////////////////////////////////////////
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// CONSTANTS
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static constexpr std::array<uint32_t, 64> kConstants = {
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{0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee, 0xf57c0faf, 0x4787c62a,
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0xa8304613, 0xfd469501, 0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
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0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821, 0xf61e2562, 0xc040b340,
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0x265e5a51, 0xe9b6c7aa, 0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
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0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed, 0xa9e3e905, 0xfcefa3f8,
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0x676f02d9, 0x8d2a4c8a, 0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
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0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70, 0x289b7ec6, 0xeaa127fa,
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0xd4ef3085, 0x04881d05, 0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
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0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039, 0x655b59c3, 0x8f0ccc92,
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0xffeff47d, 0x85845dd1, 0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
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0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391}};
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static constexpr std::array<uint32_t, 16> kShifts = {
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{7, 12, 17, 22, 5, 9, 14, 20, 4, 11, 16, 23, 6, 10, 15, 21}};
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// The initial intermediate data.
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static constexpr IntermediateData kInitialIntermediateData{
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0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476};
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//////////////////////////////////////////////////////////////////////////////
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// PADDED MESSAGE GENERATION / EXTRACTION
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// Given the message length, calculates the padded message length. There has
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// to be room for the 1-byte end-of-message marker, plus 8 bytes for the
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// uint64_t encoded message length, all rounded up to a multiple of 64 bytes.
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static constexpr uint32_t GetPaddedMessageLength(const uint32_t n) {
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return (((n + 1 + 8) + 63) / 64) * 64;
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}
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// Extracts the |i|th byte of a uint64_t, where |i == 0| extracts the least
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// significant byte. It is expected that 0 <= i < 8.
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static constexpr uint8_t ExtractByte(const uint64_t value, const uint32_t i) {
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DCHECK(i < 8);
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return static_cast<uint8_t>((value >> (i * 8)) & 0xff);
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}
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// Extracts the |i|th byte of a message of length |n|.
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static constexpr uint8_t GetPaddedMessageByte(const char* data,
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const uint32_t n,
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const uint32_t m,
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const uint32_t i) {
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DCHECK(i < m);
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DCHECK(n < m);
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DCHECK(m % 64 == 0);
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if (i < n) {
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// Emit the message itself...
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return data[i];
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} else if (i == n) {
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// ...followed by the end of message marker.
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return 0x80;
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} else if (i >= m - 8) {
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// The last 8 bytes encode the original message length times 8.
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return ExtractByte(n * 8, i - (m - 8));
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} else {
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// And everything else is just empyt padding.
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return 0;
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}
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}
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// Extracts the uint32_t starting at position |i| from the padded message
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// generate by the provided input |data| of length |n|. The bytes are treated
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// in little endian order.
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static constexpr uint32_t GetPaddedMessageWord(const char* data,
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const uint32_t n,
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const uint32_t m,
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const uint32_t i) {
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DCHECK(i % 4 == 0);
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DCHECK(i < m);
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DCHECK(n < m);
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DCHECK(m % 64 == 0);
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return static_cast<uint32_t>(GetPaddedMessageByte(data, n, m, i)) |
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static_cast<uint32_t>((GetPaddedMessageByte(data, n, m, i + 1))
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<< 8) |
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static_cast<uint32_t>((GetPaddedMessageByte(data, n, m, i + 2))
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<< 16) |
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static_cast<uint32_t>((GetPaddedMessageByte(data, n, m, i + 3))
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<< 24);
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}
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// Given an input buffer of length |n| bytes, extracts one round worth of data
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// starting at offset |i|.
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static constexpr RoundData GetRoundData(const char* data,
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const uint32_t n,
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const uint32_t m,
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const uint32_t i) {
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DCHECK(i % 64 == 0);
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DCHECK(i < m);
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DCHECK(n < m);
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DCHECK(m % 64 == 0);
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return RoundData{{GetPaddedMessageWord(data, n, m, i),
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GetPaddedMessageWord(data, n, m, i + 4),
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GetPaddedMessageWord(data, n, m, i + 8),
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GetPaddedMessageWord(data, n, m, i + 12),
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GetPaddedMessageWord(data, n, m, i + 16),
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GetPaddedMessageWord(data, n, m, i + 20),
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GetPaddedMessageWord(data, n, m, i + 24),
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GetPaddedMessageWord(data, n, m, i + 28),
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GetPaddedMessageWord(data, n, m, i + 32),
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GetPaddedMessageWord(data, n, m, i + 36),
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GetPaddedMessageWord(data, n, m, i + 40),
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GetPaddedMessageWord(data, n, m, i + 44),
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GetPaddedMessageWord(data, n, m, i + 48),
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GetPaddedMessageWord(data, n, m, i + 52),
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GetPaddedMessageWord(data, n, m, i + 56),
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GetPaddedMessageWord(data, n, m, i + 60)}};
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}
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//////////////////////////////////////////////////////////////////////////////
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// HASH IMPLEMENTATION
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// Mixes elements |b|, |c| and |d| at round |i| of the calculation.
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static constexpr uint32_t CalcF(const uint32_t i,
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const uint32_t b,
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const uint32_t c,
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const uint32_t d) {
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DCHECK(i < 64);
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if (i < 16) {
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return d ^ (b & (c ^ d));
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} else if (i < 32) {
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return c ^ (d & (b ^ c));
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} else if (i < 48) {
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return b ^ c ^ d;
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} else {
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return c ^ (b | (~d));
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}
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}
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static constexpr uint32_t CalcF(const uint32_t i,
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const IntermediateData& intermediate) {
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return CalcF(i, intermediate.b, intermediate.c, intermediate.d);
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}
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// Calculates the indexing function at round |i|.
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static constexpr uint32_t CalcG(const uint32_t i) {
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DCHECK(i < 64);
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if (i < 16) {
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return i;
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} else if (i < 32) {
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return (5 * i + 1) % 16;
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} else if (i < 48) {
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return (3 * i + 5) % 16;
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} else {
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return (7 * i) % 16;
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}
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}
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// Calculates the rotation to be applied at round |i|.
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static constexpr uint32_t GetShift(const uint32_t i) {
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DCHECK(i < 64);
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return kShifts[(i / 16) * 4 + (i % 4)];
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}
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// Rotates to the left the given |value| by the given |bits|.
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static constexpr uint32_t LeftRotate(const uint32_t value,
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const uint32_t bits) {
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DCHECK(bits < 32);
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return (value << bits) | (value >> (32 - bits));
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}
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// Applies the ith step of mixing.
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static constexpr IntermediateData ApplyStep(
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const uint32_t i,
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const RoundData& data,
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const IntermediateData& intermediate) {
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DCHECK(i < 64);
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const uint32_t g = CalcG(i);
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DCHECK(g < 16);
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const uint32_t f =
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CalcF(i, intermediate) + intermediate.a + kConstants[i] + data[g];
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const uint32_t s = GetShift(i);
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return IntermediateData{/* a */ intermediate.d,
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/* b */ intermediate.b + LeftRotate(f, s),
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/* c */ intermediate.b,
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/* d */ intermediate.c};
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}
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// Adds two IntermediateData together.
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static constexpr IntermediateData Add(const IntermediateData& intermediate1,
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const IntermediateData& intermediate2) {
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return IntermediateData{
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intermediate1.a + intermediate2.a, intermediate1.b + intermediate2.b,
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intermediate1.c + intermediate2.c, intermediate1.d + intermediate2.d};
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}
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// Processes an entire message.
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static constexpr IntermediateData ProcessMessage(const char* message,
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const uint32_t n) {
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const uint32_t m = GetPaddedMessageLength(n);
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IntermediateData intermediate0 = kInitialIntermediateData;
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for (uint32_t offset = 0; offset < m; offset += 64) {
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RoundData data = GetRoundData(message, n, m, offset);
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IntermediateData intermediate1 = intermediate0;
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for (uint32_t i = 0; i < 64; ++i)
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intermediate1 = ApplyStep(i, data, intermediate1);
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intermediate0 = Add(intermediate0, intermediate1);
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}
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return intermediate0;
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}
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//////////////////////////////////////////////////////////////////////////////
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// HELPER FUNCTIONS
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// Converts an IntermediateData to a final digest.
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static constexpr MD5Digest IntermediateDataToMD5Digest(
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const IntermediateData& intermediate) {
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return MD5Digest{{static_cast<uint8_t>((intermediate.a >> 0) & 0xff),
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static_cast<uint8_t>((intermediate.a >> 8) & 0xff),
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static_cast<uint8_t>((intermediate.a >> 16) & 0xff),
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static_cast<uint8_t>((intermediate.a >> 24) & 0xff),
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static_cast<uint8_t>((intermediate.b >> 0) & 0xff),
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static_cast<uint8_t>((intermediate.b >> 8) & 0xff),
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static_cast<uint8_t>((intermediate.b >> 16) & 0xff),
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static_cast<uint8_t>((intermediate.b >> 24) & 0xff),
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static_cast<uint8_t>((intermediate.c >> 0) & 0xff),
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static_cast<uint8_t>((intermediate.c >> 8) & 0xff),
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static_cast<uint8_t>((intermediate.c >> 16) & 0xff),
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static_cast<uint8_t>((intermediate.c >> 24) & 0xff),
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static_cast<uint8_t>((intermediate.d >> 0) & 0xff),
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static_cast<uint8_t>((intermediate.d >> 8) & 0xff),
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static_cast<uint8_t>((intermediate.d >> 16) & 0xff),
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static_cast<uint8_t>((intermediate.d >> 24) & 0xff)}};
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}
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static constexpr uint32_t StringLength(const char* string) {
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const char* end = string;
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while (*end != 0)
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++end;
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// Double check that the precision losing conversion is safe.
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DCHECK(end >= string);
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DCHECK(static_cast<std::ptrdiff_t>(static_cast<uint32_t>(end - string)) ==
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(end - string));
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return static_cast<uint32_t>(end - string);
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}
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static constexpr uint32_t SwapEndian(uint32_t a) {
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return ((a & 0xff) << 24) | (((a >> 8) & 0xff) << 16) |
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(((a >> 16) & 0xff) << 8) | ((a >> 24) & 0xff);
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}
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//////////////////////////////////////////////////////////////////////////////
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// WRAPPER FUNCTIONS
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static constexpr MD5Digest Sum(const char* data, uint32_t n) {
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return IntermediateDataToMD5Digest(ProcessMessage(data, n));
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}
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static constexpr uint64_t Hash64(const char* data, uint32_t n) {
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IntermediateData intermediate = ProcessMessage(data, n);
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return (static_cast<uint64_t>(SwapEndian(intermediate.a)) << 32) |
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static_cast<uint64_t>(SwapEndian(intermediate.b));
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}
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static constexpr uint32_t Hash32(const char* data, uint32_t n) {
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IntermediateData intermediate = ProcessMessage(data, n);
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return SwapEndian(intermediate.a);
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}
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};
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} // namespace internal
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// Implementations of the functions exposed in the public header.
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constexpr MD5Digest MD5SumConstexpr(const char* string) {
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return internal::MD5CE::Sum(string, internal::MD5CE::StringLength(string));
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}
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constexpr MD5Digest MD5SumConstexpr(const char* string, uint32_t length) {
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return internal::MD5CE::Sum(string, length);
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}
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constexpr uint64_t MD5Hash64Constexpr(const char* string) {
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return internal::MD5CE::Hash64(string, internal::MD5CE::StringLength(string));
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}
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constexpr uint64_t MD5Hash64Constexpr(const char* string, uint32_t length) {
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return internal::MD5CE::Hash64(string, length);
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}
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constexpr uint32_t MD5Hash32Constexpr(const char* string) {
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return internal::MD5CE::Hash32(string, internal::MD5CE::StringLength(string));
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}
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constexpr uint32_t MD5Hash32Constexpr(const char* string, uint32_t length) {
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return internal::MD5CE::Hash32(string, length);
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}
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} // namespace base
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#endif // BASE_HASH_MD5_CONSTEXPR_INTERNAL_H_
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