MD5 算法 实现

最近接触了HTML5中的websocket，下载了一个C实现的websocket库，但是其MD5算法实现中，涉及到AVR相关内容，编译时缺少头文件，而且需要交叉编译，我不是很清楚，于是乎，参照相关资料，实现了MD5算法。

由于我要处理的是字符串，长度较小，而且是以byte为单位，因此实现中并未以bit作为基本单位，同时内部对输入数据进行了拷贝，不适合处理大型文件。

/*
 * summary: MD5
 * author: caosiyang
 * email: csy3228@gmail.com
 */
#ifndef __MD5_H__
#define __MD5_H__


#include <assert.h>
#include <math.h>
#include <iostream>
#include <string>
using namespace std;


class MD5 {
public:
    MD5();
    ~MD5();
    string calc(const char *str);
    string calc(const char *buf, int32_t len);

protected:
    MD5(const MD5 &);
    MD5& operator=(const MD5 &);

private:
    uint32_t T[64];
    static const uint32_t CV[4];
    static const uint32_t R[64];

    void prepare(const char *buf, int32_t len, char *&outbuf, int32_t &outlen);
    inline uint32_t rotate_left(uint32_t num, uint32_t n) const;
    string _gen_md5_str(uint32_t a, uint32_t b, uint32_t c, uint32_t d) const;
    inline uint32_t _reverse(const uint32_t n) const;

    inline uint32_t F(uint32_t x, uint32_t y, uint32_t z) const;
    inline uint32_t G(uint32_t x, uint32_t y, uint32_t z) const;
    inline uint32_t H(uint32_t x, uint32_t y, uint32_t z) const;
    inline uint32_t I(uint32_t x, uint32_t y, uint32_t z) const;

#if 0
    inline int32_t FF(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t);
    inline int32_t GG(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t);
    inline int32_t HH(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t);
    inline int32_t II(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t);
#endif
};


#endif

#include "md5.h"


const uint32_t MD5::CV[4] = {
    0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476
};


const uint32_t MD5::R[64] = {
    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
};


MD5::MD5() {
    //initialize T[]
    for (int i = 1; i <= 64; ++i) {
        long long ti = pow(2, 32) * sin(i);
        if (ti < 0) {
            ti = 0 - ti;
        }
        T[i - 1] = ti;
    }
}


MD5::~MD5() {
}


string MD5::calc(const char *str) {
    return calc(str, strlen(str));
}


string MD5::calc(const char *buf, const int32_t len) {
    char *outbuf = NULL;
    int32_t outlen = 0;
    prepare(buf, len, outbuf, outlen);
    assert(outlen > 0 && outlen % 64 == 0);
    
    uint32_t A = CV[0];
    uint32_t B = CV[1];
    uint32_t C = CV[2];
    uint32_t D = CV[3];
    
    for (int32_t i = 0; i < outlen / 64; ++i) {
        uint32_t X[16] = {0};
        for (int32_t j = 0; j < 16; ++j) {
            X[j] = *(uint32_t*)(outbuf + (64 * i + 4 * j));
        }

        uint32_t a = A;
        uint32_t b = B;
        uint32_t c = C;
        uint32_t d = D;
        
        for (int i = 0; i < 64; ++i) {
            int32_t g = 0;
            if (i >= 0 && i <= 15) {
                g = i;
                a = (uint32_t)(b + rotate_left(a + F(b, c, d) + X[g] + T[i], R[i]));
            } else if (i >= 16 && i <= 31) {
                g = (i * 5 + 1) % 16;
                a = (uint32_t)(b + rotate_left(a + G(b, c, d) + X[g] + T[i], R[i]));
            } else if (i >= 32 && i <= 47) {
                g = (i * 3 + 5) % 16;
                a = (uint32_t)(b + rotate_left(a + H(b, c, d) + X[g] + T[i], R[i]));
            } else if (i >= 48 && i <= 63) {
                g = (i * 7) % 16;
                a = (uint32_t)(b + rotate_left(a + I(b, c, d) + X[g] + T[i], R[i]));
            }
            
            //loop swap
            uint32_t temp = d;
            d = c;
            c = b;
            b = a;
            a = temp;
        }

        A = A + a;
        B = B + b;
        C = C + c;
        D = D + d;
    }

    return _gen_md5_str(A, B, C, D);
}


inline uint32_t MD5::rotate_left(uint32_t num, uint32_t n) const {
    return (num << n) | (num >> (32 - n % 32));
}


string MD5::_gen_md5_str(uint32_t a, uint32_t b, uint32_t c, uint32_t d) const {
    char res[33] = {0};
    sprintf(res, "%08x%08x%08x%08x", _reverse(a), _reverse(b), _reverse(c), _reverse(d));
    return res;
}


inline uint32_t MD5::_reverse(const uint32_t n) const {
    return ((n & 0x000000ff) << 24) | ((n & 0x0000ff00) << 8) | ((n & 0x00ff0000) >> 8) | ((n & 0xff000000) >> 24);
}


void MD5::prepare(const char *buf, int32_t len, char *&outbuf, int32_t &outlen) {
    int32_t x = len * 8 % 512;
    int32_t bit_to_fill = (x < 448) ? (448 - x) : (512 - x + 448);
    char c1 = 1, c2 = 0;
    c1 = c1 << 7;

    if (bit_to_fill % 8 == 0) {
        int32_t byte_to_fill = bit_to_fill / 8;
        int32_t new_len = len + byte_to_fill + 8;

        char *p = new (nothrow) char[new_len];
        assert(p);
        char *q = p;
        memcpy(q, buf, len);
        q += len;
        for (int i = 0; i < byte_to_fill; ++i) {
            if (i == 0) {
                memcpy(q, &c1, 1);
            } else {
                memcpy(q, &c2, 1);
            }
            ++q;
        }

        int64_t length = len * 8;
        memcpy(q, &length, 8);

        outbuf = p;
        outlen = new_len;
    }
    assert(bit_to_fill % 8 == 0);
}
    

inline uint32_t MD5::F(uint32_t x, uint32_t y, uint32_t z) const {
    return (x & y) | ((~x) & z);
}


inline uint32_t MD5::G(uint32_t x, uint32_t y, uint32_t z) const {
    return (x & z) | (y & (~z));
}


inline uint32_t MD5::H(uint32_t x, uint32_t y, uint32_t z) const {
    return x ^ y ^ z;
}


inline uint32_t MD5::I(uint32_t x, uint32_t y, uint32_t z) const {
    return y ^ (x | (~z));
}


#if 0
inline int32_t MD5::FF(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t) {
}


inline int32_t MD5::GG(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t) {
}


inline int32_t MD5::HH(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t) {
}


inline int32_t MD5::II(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t) {
}
#endif

#include "md5.h"


int main() {
    MD5 md5;
    string code;
    code = md5.calc("");
    cout << "md5 = " << code << endl;
    code = md5.calc("a");
    cout << "md5 = " << code << endl;
    code = md5.calc("abc");
    cout << "md5 = " << code << endl;
    code = md5.calc("message digest");
    cout << "md5 = " << code << endl;
    code = md5.calc("abcdefghijklmnopqrstuvwxyz");
    cout << "md5 = " << code << endl;
    code = md5.calc("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");
    cout << "md5 = " << code << endl;
    return 0;
}