Modified MD5 library

md5.c

#include "md5.h"
 
const uint32_t r[] = {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};

const 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};

void md5(uint8_t *initial_msg, size_t initial_len, uint32_t hash[4]) 
{
    uint8_t *msg = NULL;
 
    hash[0] = 0x67452301;
    hash[1] = 0xefcdab89;
    hash[2] = 0x98badcfe;
    hash[3] = 0x10325476;
 
    int new_len = ((((initial_len + 8) / 64) + 1) * 64) - 8;
 
    msg = calloc(new_len + 64, 1);
    memcpy(msg, initial_msg, initial_len);
    msg[initial_len] = 128;
 
    uint32_t bits_len = 8*initial_len;
    memcpy(msg + new_len, &bits_len, 4);

    int offset;
    for(offset=0; offset<new_len; offset += (512/8)) {
        uint32_t *w = (uint32_t *) (msg + offset);

        uint32_t a = hash[0];
        uint32_t b = hash[1];
        uint32_t c = hash[2];
        uint32_t d = hash[3];
 
        uint32_t i;
        for(i = 0; i<64; i++) {
            uint32_t f, g;
 
            if (i < 16) {
                f = (b & c) | ((~b) & d);
                g = i;
            } else if (i < 32) {
                f = (d & b) | ((~d) & c);
                g = (5*i + 1) % 16;
            } else if (i < 48) {
                f = b ^ c ^ d;
                g = (3*i + 5) % 16;          
            } else {
                f = c ^ (b | (~d));
                g = (7*i) % 16;
            }

            uint32_t temp = d;
            d = c;
            c = b;
            b = b + LEFTROTATE((a + f + k[i] + w[g]), r[i]);
            a = temp;
        }
 
        hash[0] += a;
        hash[1] += b;
        hash[2] += c;
        hash[3] += d;
    }
    
    free(msg);
}

void md5_to_hex(uint32_t hash[4], char str[33])
{
    char part[8];
    uint8_t *p;
    for (int i = 0; i < 4; i++) {
        p = (uint8_t *) &hash[i];
        sprintf(part, "%2.2x%2.2x%2.2x%2.2x", p[0], p[1], p[2], p[3], hash[i]);
        strcat(str, part);
    }
    strcat(str, "\0");
}

md5.h

#ifndef _MD5_H
#define _MD5_H

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

#define LEFTROTATE(x, c) (((x) << (c)) | ((x) >> (32 - (c))))

void md5(uint8_t *initial_msg, size_t initial_len, uint32_t hash[4]);
void md5_to_hex(uint32_t hash[4], char str[33]);

#endif

md5_test.c

/*
 * Simple MD5 implementation
 *
 * Compile with: gcc md5.c md5_test.c -o md5_test.exe
 */

#include "md5.h"

int main(int argc, char **argv) 
{
    if (argc < 2) {
        printf("usage: %s 'string'\n", argv[0]);
        return 1;
    }
 
    char *msg = argv[1];
    size_t len = strlen(msg);
    uint32_t md5_val[4];
 
    // benchmark
    // int i;
    // for (i = 0; i < 1000000; i++) {
        md5(msg, len, md5_val);
    // }
 
    char str[33];
    md5_to_hex(md5_val, str);
    printf("%s\n", str);
 
    return 0;
}