MD5

main.cc

#include "md5.h"

#include <cstdio>
#include <cstdlib>

int main(int argc, char **argv) {
	if (argc < 2) {
		printf("usage: %s 'string'\n", argv[0]);
		return 1;
	}

	std::string_view const msg = argv[1];

	auto const digest = md5(msg);

	for (auto &x : digest)
		printf("%2.2x", x);

	printf("\n");
}

md5.cc

/*
 * MD5
 *
 * Converted to modern C++17 by Nikolay Mihaylov (nmmm@nmmm.nu)
 * Copyright (C) 2022-09-08
 *
 *
 *
 * based on:
 * http://www.zedwood.com/article/cpp-md5-function
 *
 *
 *
 * converted to C++ class by Frank Thilo (thilo@unix-ag.org)
 * for bzflag (http://www.bzflag.org)
 *
 * based on:
 *
 *
 *
 * md5.h and md5.c
 * reference implementation of RFC 1321
 *
 * Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991.
 * All rights reserved.
 *
 * License to copy and use this software is granted provided that it
 * is identified as the "RSA Data Security, Inc. MD5 Message-Digest
 * Algorithm" in all material mentioning or referencing this software
 * or this function.
 *
 * License is also granted to make and use derivative works provided
 * that such works are identified as "derived from the RSA Data
 * Security, Inc. MD5 Message-Digest Algorithm" in all material
 * mentioning or referencing the derived work.
 *
 * RSA Data Security, Inc. makes no representations concerning either
 * the merchantability of this software or the suitability of this
 * software for any particular purpose. It is provided "as is"
 * without express or implied warranty of any kind.
 *
 * These notices must be retained in any copies of any part of this
 * documentation and/or software.
 */



#include "md5.h"

#include <cstring>



namespace md5_implementation_{
	namespace{
		auto memset_secure(void *p, int value, size_t size){
			return memset(p, value, size);
		}

		using uint1	= MD5::uint1;
		using uint4	= MD5::uint4;
		using size_type	= MD5::size_type;

		constexpr uint1 padding[64] = {
			0x80,
			0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0
		};

		// Constants for MD5Transform routine.
		constexpr uint1 S11 =  7;
		constexpr uint1 S12 = 12;
		constexpr uint1 S13 = 17;
		constexpr uint1 S14 = 22;
		constexpr uint1 S21 =  5;
		constexpr uint1 S22 =  9;
		constexpr uint1 S23 = 14;
		constexpr uint1 S24 = 20;
		constexpr uint1 S31 =  4;
		constexpr uint1 S32 = 11;
		constexpr uint1 S33 = 16;
		constexpr uint1 S34 = 23;
		constexpr uint1 S41 =  6;
		constexpr uint1 S42 = 10;
		constexpr uint1 S43 = 15;
		constexpr uint1 S44 = 21;

		// F, G, H and I are basic MD5 functions.
		constexpr uint4 F(uint4 x, uint4 y, uint4 z) {
			return (x & y) | (~x & z);
		}

		constexpr uint4 G(uint4 x, uint4 y, uint4 z) {
			return (x & z) | (y & ~z);
		}

		constexpr uint4 H(uint4 x, uint4 y, uint4 z) {
			return x ^ y ^ z;
		}

		constexpr uint4 I(uint4 x, uint4 y, uint4 z) {
			return y ^ (x | ~z);
		}

		// rotate_left rotates x left n bits.
		constexpr uint4 rotate_left(uint4 x, int n) {
			return (x << n) | (x >> (32-n));
		}

		// FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
		// Rotation is separate from addition to prevent recomputation.
		constexpr void FF(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac) {
			a = rotate_left(a+ F(b,c,d) + x + ac, s) + b;
		}

		constexpr void GG(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac) {
			a = rotate_left(a + G(b,c,d) + x + ac, s) + b;
		}

		constexpr void HH(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac) {
			a = rotate_left(a + H(b,c,d) + x + ac, s) + b;
		}

		constexpr void II(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac) {
			a = rotate_left(a + I(b,c,d) + x + ac, s) + b;
		}

		// decodes input (unsigned char) into output (uint4). Assumes len is a multiple of 4.
		void decode(uint4 *output, const uint1 *input, size_type len){
			for (unsigned int i = 0, j = 0; j < len; i++, j += 4)
				output[i] =
					(((uint4)input[j + 0]) <<  0) |
					(((uint4)input[j + 1]) <<  8) |
					(((uint4)input[j + 2]) << 16) |
					(((uint4)input[j + 3]) << 24)
				;
		}

		// encodes input (uint4) into output (unsigned char). Assumes len is a multiple of 4.
		void encode(uint1 *output, const uint4 *input, size_type len){
			for (size_type i = 0, j = 0; j < len; i++, j += 4) {
				output[j + 0] = uint1(input[i] >>  0) & 0xff;
				output[j + 1] = uint1(input[i] >>  8) & 0xff;
				output[j + 2] = uint1(input[i] >> 16) & 0xff;
				output[j + 3] = uint1(input[i] >> 24) & 0xff;
			}
		}

		void encode(MD5::Digest &digest, const uint4 *input){
			return encode(digest.data(), input, (size_type) digest.size());
		}
	} // anonymous namespace
} // namespace md5_implementation_

// apply MD5 algo on a block
void MD5::transform_(const uint1 block[blocksize]){
	using namespace md5_implementation_;

	uint4 a = state[0];
	uint4 b = state[1];
	uint4 c = state[2];
	uint4 d = state[3];

	uint4 x[16];

	decode (x, block, blocksize);

	/* Round 1 */
	FF(a, b, c, d, x[ 0], S11, 0xd76aa478); /*  1 */
	FF(d, a, b, c, x[ 1], S12, 0xe8c7b756); /*  2 */
	FF(c, d, a, b, x[ 2], S13, 0x242070db); /*  3 */
	FF(b, c, d, a, x[ 3], S14, 0xc1bdceee); /*  4 */
	FF(a, b, c, d, x[ 4], S11, 0xf57c0faf); /*  5 */
	FF(d, a, b, c, x[ 5], S12, 0x4787c62a); /*  6 */
	FF(c, d, a, b, x[ 6], S13, 0xa8304613); /*  7 */
	FF(b, c, d, a, x[ 7], S14, 0xfd469501); /*  8 */
	FF(a, b, c, d, x[ 8], S11, 0x698098d8); /*  9 */
	FF(d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
	FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
	FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
	FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
	FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
	FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
	FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

	/* Round 2 */
	GG(a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
	GG(d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
	GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
	GG(b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
	GG(a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
	GG(d, a, b, c, x[10], S22, 0x02441453); /* 22 */
	GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
	GG(b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
	GG(a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
	GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
	GG(c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
	GG(b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
	GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
	GG(d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
	GG(c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
	GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

	/* Round 3 */
	HH(a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
	HH(d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
	HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
	HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
	HH(a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
	HH(d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
	HH(c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
	HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
	HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
	HH(d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
	HH(c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
	HH(b, c, d, a, x[ 6], S34, 0x04881d05); /* 44 */
	HH(a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
	HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
	HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
	HH(b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */

	/* Round 4 */
	II(a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
	II(d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
	II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
	II(b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
	II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
	II(d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
	II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
	II(b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
	II(a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
	II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
	II(c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
	II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
	II(a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
	II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
	II(c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
	II(b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */

	state[0] += a;
	state[1] += b;
	state[2] += c;
	state[3] += d;

	// Zeroize sensitive information.
	if constexpr(MD5::secure_wipe)
		memset_secure(x, 0, sizeof(x));
}

// MD5 block update operation. Continues an MD5 message-digest operation,
// processing another message block
void MD5::update(const unsigned char input[], size_type length){
	using namespace md5_implementation_;

	// compute number of bytes mod 64
	size_type index = count[0] / 8 % blocksize;

	// Update number of bits
	if ((count[0] += (length << 3)) < (length << 3))
		count[1]++;

	count[1] += (length >> 29);

	// number of bytes we need to fill in buffer
	size_type firstpart = 64 - index;

	size_type i;

	// transform as many times as possible.
	if (length >= firstpart){
		// fill buffer first, transform
		memcpy(&buffer[index], input, firstpart);

		transform_(buffer);

		// transform chunks of blocksize (64 bytes)
		for(i = firstpart; i + blocksize <= length; i += blocksize)
			transform_(&input[i]);

		index = 0;
	}else
		i = 0;

	// buffer remaining input
	memcpy(&buffer[index], &input[i], length-i);
}

// MD5 finalization. Ends an MD5 message-digest operation,
// writing the the message digest and zeroizing the context.

auto MD5::finalize() -> Digest{
	using namespace md5_implementation_;

	// Save number of bits
	uint1 bits[8];
	encode(bits, count, 8);

	// pad out to 56 mod 64.
	size_type index  = count[0] / 8 % 64;
	size_type padLen = (index < 56) ? (56 - index) : (120 - index);
	update(padding, padLen);

	// Append length (before padding)
	update(bits, 8);

	Digest digest;

	// Store state in digest
	encode(digest, state);

	// Zeroize sensitive information.
	if constexpr(MD5::secure_wipe){
		memset_secure(buffer, 0, sizeof(buffer));
		memset_secure(count,  0, sizeof(count ));
	}

	return digest;
}

md5.h

#ifndef MY_MD5_H_
#define MY_MD5_H_

#include <cstdint>
#include <string_view>
#include <array>
#include <limits>
#include <cassert>



class MD5{
public:
	constexpr static auto bits = 128;

	constexpr static bool secure_wipe = true;

	using uint1	= uint8_t;
	using uint4	= uint32_t;
	using size_type	= uint4;	// must be 32bit

	using Digest = std::array<uint1, 16>;

public:
	MD5() = default;

	MD5(std::string_view s){
		update(s);
	}

	void update(const uint1 *buffer, size_type size);

	void update(const char *s, size_t size){
		assert( size < std::numeric_limits<size_type>::max() );

		update((const uint1 *) s, (size_type) size);
	}

	void update(std::string_view s){
		update(s.data(), s.size());
	}


	Digest finalize();

private:
	constexpr static auto blocksize = 64;

private:
	void transform_(const uint1 block[blocksize]);

private:
	uint1 buffer[blocksize];	// bytes that didn't fit in last 64 byte chunk

	uint4 count[2] = {		// 64bit counter for number of bits (lo, hi)
		0,
		0
	};

	uint4 state[4] = {		// digest so far
		0x67452301,
		0xefcdab89,
		0x98badcfe,
		0x10325476
	};
};



inline MD5::Digest md5(std::string_view s){
	MD5 f(s);
	return f.finalize();
}



#endif