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md5.cpp
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/*
Christoffer Maliniemi 2016-10-25
Based pseudocode from wikipedia and RFC 1321 specification.
*/
#include "md5.h"
#include <algorithm>
#include <cstring>
constexpr uint32_t s[] = {
7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22,
5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20,
4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23,
6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21
};
constexpr uint32_t K[] = {
0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
};
constexpr uint32_t leftrotate(uint32_t x, uint32_t c) {
return (x << c) | (x >> (32 - c));
}
constexpr uint32_t bitwise_part(int i, uint32_t x, uint32_t y, uint32_t z) {
return (i < 16) ? z ^ (x & (y ^ z)) : (i < 32) ? y ^ (z & (x ^ y)) : (i < 48) ? x ^ y ^ z : y ^ (x | ~z);
}
constexpr int data_index(int i) {
return (i < 16) ? i : (i < 32) ? (5 * i + 1) % 16 : (i < 48) ? (3 * i + 5) % 16 : (7 * i) % 16;
}
template<int index>
constexpr void process(uint32_t& a, uint32_t b, uint32_t c, uint32_t d, uint32_t* data) {
a = leftrotate(a + bitwise_part(index, b, c, d) + data[data_index(index)] + K[index], s[index]) + b;
}
MD5Value md5(const char* message, int length) {
MD5Value value{{0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476}};
size_t chunks = (length + 8) >> 6;
int remaining = length;
bool ending = false;
for(size_t i = 0; i <= chunks; ++i) {
uint32_t data[16];
uint8_t* bufptr = reinterpret_cast<uint8_t*>(data);
int bytes = std::min(remaining, 64);
std::memcpy(data, message + remaining - length, bytes);
std::memset(bufptr + bytes, 0, 64 - bytes);
if(remaining < 64) {
if(!ending) {
*(bufptr + bytes) = 1 << 7;
ending = true;
}
if(i == chunks) {
*(uint64_t*)(bufptr + 64 - 8) = (length * 8);
}
}
remaining -= bytes;
uint32_t a = value.chunks.a;
uint32_t b = value.chunks.b;
uint32_t c = value.chunks.c;
uint32_t d = value.chunks.d;
process< 0>(a, b, c, d, data);
process< 1>(d, a, b, c, data);
process< 2>(c, d, a, b, data);
process< 3>(b, c, d, a, data);
process< 4>(a, b, c, d, data);
process< 5>(d, a, b, c, data);
process< 6>(c, d, a, b, data);
process< 7>(b, c, d, a, data);
process< 8>(a, b, c, d, data);
process< 9>(d, a, b, c, data);
process<10>(c, d, a, b, data);
process<11>(b, c, d, a, data);
process<12>(a, b, c, d, data);
process<13>(d, a, b, c, data);
process<14>(c, d, a, b, data);
process<15>(b, c, d, a, data);
process<16>(a, b, c, d, data);
process<17>(d, a, b, c, data);
process<18>(c, d, a, b, data);
process<19>(b, c, d, a, data);
process<20>(a, b, c, d, data);
process<21>(d, a, b, c, data);
process<22>(c, d, a, b, data);
process<23>(b, c, d, a, data);
process<24>(a, b, c, d, data);
process<25>(d, a, b, c, data);
process<26>(c, d, a, b, data);
process<27>(b, c, d, a, data);
process<28>(a, b, c, d, data);
process<29>(d, a, b, c, data);
process<30>(c, d, a, b, data);
process<31>(b, c, d, a, data);
process<32>(a, b, c, d, data);
process<33>(d, a, b, c, data);
process<34>(c, d, a, b, data);
process<35>(b, c, d, a, data);
process<36>(a, b, c, d, data);
process<37>(d, a, b, c, data);
process<38>(c, d, a, b, data);
process<39>(b, c, d, a, data);
process<40>(a, b, c, d, data);
process<41>(d, a, b, c, data);
process<42>(c, d, a, b, data);
process<43>(b, c, d, a, data);
process<44>(a, b, c, d, data);
process<45>(d, a, b, c, data);
process<46>(c, d, a, b, data);
process<47>(b, c, d, a, data);
process<48>(a, b, c, d, data);
process<49>(d, a, b, c, data);
process<50>(c, d, a, b, data);
process<51>(b, c, d, a, data);
process<52>(a, b, c, d, data);
process<53>(d, a, b, c, data);
process<54>(c, d, a, b, data);
process<55>(b, c, d, a, data);
process<56>(a, b, c, d, data);
process<57>(d, a, b, c, data);
process<58>(c, d, a, b, data);
process<59>(b, c, d, a, data);
process<60>(a, b, c, d, data);
process<61>(d, a, b, c, data);
process<62>(c, d, a, b, data);
process<63>(b, c, d, a, data);
value.chunks.a += a;
value.chunks.b += b;
value.chunks.c += c;
value.chunks.d += d;
}
return value;
}
void uint32_to_chars(uint32_t value, char* buffer) {
const char* hex_digits = "0123456789abcdef";
for(int i = 0, j = 1; i < 8; ++i) {
buffer[i] = hex_digits[((value >> ((i + j) * 4)) & 0xf)];
j = -j;
}
}
void md5_to_chars(char* buffer, MD5Value value) {
uint32_to_chars(value.chunks.a, buffer);
uint32_to_chars(value.chunks.b, buffer + 8);
uint32_to_chars(value.chunks.c, buffer + 16);
uint32_to_chars(value.chunks.d, buffer + 24);
}