md5hash.c

/*
 * Simple MD5 implementation
 *
 * Compile with: gcc -o md5 -O3 -lm md5.c
 * ref: https://gist.github.com/creationix/4710780
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "md5hash.h"

// leftrotate function definition
#define LEFTROTATE(x, c) (((x) << (c)) | ((x) >> (32 - (c))))

u64 md5(u8 *initial_msg, size_t initial_len) {

    // These vars will contain the hash
    u32 h0, h1, h2, h3;

    // Message (to prepare)
    u8 *msg = NULL;

    // Note: All variables are unsigned 32 bit and wrap modulo 2^32 when calculating
    // r specifies the per-round shift amounts
    u32 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};

    // Use binary integer part of the sines of integers (in radians) as constants// Initialize variables:
    u32 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};

    h0 = 0x67452301;
    h1 = 0xefcdab89;
    h2 = 0x98badcfe;
    h3 = 0x10325476;

    // Pre-processing: adding a single 1 bit
    //append "1" bit to message
    /* Notice: the input bytes are considered as bits strings,
       where the first bit is the most significant bit of the byte.[37] */

    // Pre-processing: padding with zeros
    //append "0" bit until message length in bit ≡ 448 (mod 512)
    //append length mod (2 pow 64) to message

    int new_len;
    for(new_len = initial_len*8 + 1; new_len%512!=448; new_len++);
    new_len /= 8;

    msg = calloc(new_len + 64, 1); // also appends "0" bits
                                   // (we alloc also 64 extra bytes...)
    memcpy(msg, initial_msg, initial_len);
    msg[initial_len] = 128; // write the "1" bit

    u32 bits_len = 8*initial_len; // note, we append the len
    memcpy(msg + new_len, &bits_len, 4);           // in bits at the end of the buffer

    // Process the message in successive 512-bit chunks:
    //for each 512-bit chunk of message:
    int offset;
    for(offset=0; offset<new_len; offset += (512/8)) {

        // break chunk into sixteen 32-bit words w[j], 0 ≤ j ≤ 15
        u32 *w = (u32 *) (msg + offset);

#ifdef DEBUG
        printf("offset: %d %x\n", offset, offset);

        int j;
        for(j =0; j < 64; j++) printf("%x ", ((u8 *) w)[j]);
        puts("");
#endif

        // Initialize hash value for this chunk:
        u32 a = h0;
        u32 b = h1;
        u32 c = h2;
        u32 d = h3;

        // Main loop:
        u32 i;
        for(i = 0; i<64; i++) {

#ifdef ROUNDS
            u8 *p;
            printf("%i: ", i);
            p=(u8 *)&a;
            printf("%2.2x%2.2x%2.2x%2.2x ", p[0], p[1], p[2], p[3], a);

            p=(u8 *)&b;
            printf("%2.2x%2.2x%2.2x%2.2x ", p[0], p[1], p[2], p[3], b);

            p=(u8 *)&c;
            printf("%2.2x%2.2x%2.2x%2.2x ", p[0], p[1], p[2], p[3], c);

            p=(u8 *)&d;
            printf("%2.2x%2.2x%2.2x%2.2x", p[0], p[1], p[2], p[3], d);
            puts("");
#endif


            u32 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;
            }

#ifdef ROUNDS
            printf("f=%x g=%d w[g]=%x\n", f, g, w[g]);
#endif
            u32 temp = d;
            d = c;
            c = b;
#ifdef DEBUG
            printf("rotateLeft(%x + %x + %x + %x, %d)\n", a, f, k[i], w[g], r[i]);
#endif
            b = b + LEFTROTATE((a + f + k[i] + w[g]), r[i]);
            a = temp;



        }

        // Add this chunk's hash to result so far:

        h0 += a;
        h1 += b;
        h2 += c;
        h3 += d;
    }

    // cleanup
    free(msg);

    return h0 + h1 + h2 + h3;
}

u64 md5str(char *initial_msg, size_t initial_len) {
    /*u8 *unsigned_msg = (u8 *)calloc(initial_len, sizeof(char));
    for(size_t i = 0; i < initial_len; i++) {
        unsigned_msg[i] = (u8)(initial_msg[i]);
    }
    u64 ret =  md5((u8 *)unsigned_msg, initial_len); 
    free(unsigned_msg); unsigned_msg = NULL;
    return ret;
    */
    return md5((u8 *)initial_msg, initial_len);
}