C: MD5算法代码和示例代码

说明：提供MD5算法代码和测试示例代码

简介：MD5（Message Digest Algorithm 5）是一种常用的加密算法，它将任意长度的“字节串”映射为一个128位的大数，并且设计者寄希望于它无法逆向生成或逆向碰撞。

MD5算法具有以下特性：

????????确定性：对于相同的输入，MD5算法总是产生相同的结果。
????????非逆向性：已知一个MD5散列，要找到原始输入是非常困难的。即使输入只有微小的变化，MD5的结果也会有巨大的差异。
????????雪崩效应：当输入数据发生变化时，MD5的结果会产生极大的差异，这使得它适合用于检测数据的完整性。
????????然而，随着计算机科学的发展，MD5已经被证明存在一些弱点，特别是关于碰撞的问题。因此，它现在主要用于检测数据的完整性，而不是用于安全敏感的应用，如密码存储。

????????例如，你可以使用MD5来检查下载的文件是否被篡改，或者在数据库中存储密码时确保密码的正确性。但请注意，不应该用MD5来存储密码或执行敏感的身份验证。在这种情况下，应该使用更安全的哈希函数，如bcrypt或Argon2。

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

/* md5 ------------------------------------------------------------------------------------------------------------- */
#if 1
typedef struct {
    unsigned long total[2]; /*!< number of bytes processed  处理的字节数*/
    unsigned long state[4]; /*!< intermediate digest state  摘要状态*/
    unsigned char buffer[64];   /*!< data block being processed  正在处理的数据块*/

    unsigned char ipad[64]; /*!< HMAC: inner padding HMAC：内部填充       */
    unsigned char opad[64]; /*!< HMAC: outer padding  HMAC：外部填充      */
} tiny_md5_context;
#endif

#define TINY_CRYPT_MD5

#if defined(TINY_CRYPT_MD5)

/*
 * 32-bit integer manipulation macros (little endian)
 */
#ifndef GET_ULONG_LE
#define GET_ULONG_LE(n,b,i)                             \
    {                                                   \
        (n) = ( (unsigned long) (b)[(i)    ]       )    \
            | ( (unsigned long) (b)[(i) + 1] <<  8 )    \
            | ( (unsigned long) (b)[(i) + 2] << 16 )    \
            | ( (unsigned long) (b)[(i) + 3] << 24 );   \
    }
#endif

#ifndef PUT_ULONG_LE
#define PUT_ULONG_LE(n,b,i)                             \
    {                                                   \
        (b)[(i)    ] = (unsigned char) ( (n)       );   \
        (b)[(i) + 1] = (unsigned char) ( (n) >>  8 );   \
        (b)[(i) + 2] = (unsigned char) ( (n) >> 16 );   \
        (b)[(i) + 3] = (unsigned char) ( (n) >> 24 );   \
    }
#endif

/*
 * MD5 context setup
 */
void tiny_md5_starts(tiny_md5_context * ctx)
{
    ctx->total[0] = 0;
    ctx->total[1] = 0;

    ctx->state[0] = 0x67452301;
    ctx->state[1] = 0xEFCDAB89;
    ctx->state[2] = 0x98BADCFE;
    ctx->state[3] = 0x10325476;
}

static void md5_process(tiny_md5_context * ctx, unsigned char data[64])
{
    unsigned long X[16], A, B, C, D;

    GET_ULONG_LE(X[0], data, 0);
    GET_ULONG_LE(X[1], data, 4);
    GET_ULONG_LE(X[2], data, 8);
    GET_ULONG_LE(X[3], data, 12);
    GET_ULONG_LE(X[4], data, 16);
    GET_ULONG_LE(X[5], data, 20);
    GET_ULONG_LE(X[6], data, 24);
    GET_ULONG_LE(X[7], data, 28);
    GET_ULONG_LE(X[8], data, 32);
    GET_ULONG_LE(X[9], data, 36);
    GET_ULONG_LE(X[10], data, 40);
    GET_ULONG_LE(X[11], data, 44);
    GET_ULONG_LE(X[12], data, 48);
    GET_ULONG_LE(X[13], data, 52);
    GET_ULONG_LE(X[14], data, 56);
    GET_ULONG_LE(X[15], data, 60);

#define S(x,n) ((x << n) | ((x & 0xFFFFFFFF) >> (32 - n)))

#define P(a,b,c,d,k,s,t)                            \
    {                                               \
        a += F(b,c,d) + X[k] + t; a = S(a,s) + b;   \
    }

    A = ctx->state[0];
    B = ctx->state[1];
    C = ctx->state[2];
    D = ctx->state[3];

#define F(x,y,z) (z ^ (x & (y ^ z)))

    P(A, B, C, D, 0, 7, 0xD76AA478);
    P(D, A, B, C, 1, 12, 0xE8C7B756);
    P(C, D, A, B, 2, 17, 0x242070DB);
    P(B, C, D, A, 3, 22, 0xC1BDCEEE);
    P(A, B, C, D, 4, 7, 0xF57C0FAF);
    P(D, A, B, C, 5, 12, 0x4787C62A);
    P(C, D, A, B, 6, 17, 0xA8304613);
    P(B, C, D, A, 7, 22, 0xFD469501);
    P(A, B, C, D, 8, 7, 0x698098D8);
    P(D, A, B, C, 9, 12, 0x8B44F7AF);
    P(C, D, A, B, 10, 17, 0xFFFF5BB1);
    P(B, C, D, A, 11, 22, 0x895CD7BE);
    P(A, B, C, D, 12, 7, 0x6B901122);
    P(D, A, B, C, 13, 12, 0xFD987193);
    P(C, D, A, B, 14, 17, 0xA679438E);
    P(B, C, D, A, 15, 22, 0x49B40821);

#undef F

#define F(x,y,z) (y ^ (z & (x ^ y)))

    P(A, B, C, D, 1, 5, 0xF61E2562);
    P(D, A, B, C, 6, 9, 0xC040B340);
    P(C, D, A, B, 11, 14, 0x265E5A51);
    P(B, C, D, A, 0, 20, 0xE9B6C7AA);
    P(A, B, C, D, 5, 5, 0xD62F105D);
    P(D, A, B, C, 10, 9, 0x02441453);
    P(C, D, A, B, 15, 14, 0xD8A1E681);
    P(B, C, D, A, 4, 20, 0xE7D3FBC8);
    P(A, B, C, D, 9, 5, 0x21E1CDE6);
    P(D, A, B, C, 14, 9, 0xC33707D6);
    P(C, D, A, B, 3, 14, 0xF4D50D87);
    P(B, C, D, A, 8, 20, 0x455A14ED);
    P(A, B, C, D, 13, 5, 0xA9E3E905);
    P(D, A, B, C, 2, 9, 0xFCEFA3F8);
    P(C, D, A, B, 7, 14, 0x676F02D9);
    P(B, C, D, A, 12, 20, 0x8D2A4C8A);

#undef F

#define F(x,y,z) (x ^ y ^ z)

    P(A, B, C, D, 5, 4, 0xFFFA3942);
    P(D, A, B, C, 8, 11, 0x8771F681);
    P(C, D, A, B, 11, 16, 0x6D9D6122);
    P(B, C, D, A, 14, 23, 0xFDE5380C);
    P(A, B, C, D, 1, 4, 0xA4BEEA44);
    P(D, A, B, C, 4, 11, 0x4BDECFA9);
    P(C, D, A, B, 7, 16, 0xF6BB4B60);
    P(B, C, D, A, 10, 23, 0xBEBFBC70);
    P(A, B, C, D, 13, 4, 0x289B7EC6);
    P(D, A, B, C, 0, 11, 0xEAA127FA);
    P(C, D, A, B, 3, 16, 0xD4EF3085);
    P(B, C, D, A, 6, 23, 0x04881D05);
    P(A, B, C, D, 9, 4, 0xD9D4D039);
    P(D, A, B, C, 12, 11, 0xE6DB99E5);
    P(C, D, A, B, 15, 16, 0x1FA27CF8);
    P(B, C, D, A, 2, 23, 0xC4AC5665);

#undef F

#define F(x,y,z) (y ^ (x | ~z))

    P(A, B, C, D, 0, 6, 0xF4292244);
    P(D, A, B, C, 7, 10, 0x432AFF97);
    P(C, D, A, B, 14, 15, 0xAB9423A7);
    P(B, C, D, A, 5, 21, 0xFC93A039);
    P(A, B, C, D, 12, 6, 0x655B59C3);
    P(D, A, B, C, 3, 10, 0x8F0CCC92);
    P(C, D, A, B, 10, 15, 0xFFEFF47D);
    P(B, C, D, A, 1, 21, 0x85845DD1);
    P(A, B, C, D, 8, 6, 0x6FA87E4F);
    P(D, A, B, C, 15, 10, 0xFE2CE6E0);
    P(C, D, A, B, 6, 15, 0xA3014314);
    P(B, C, D, A, 13, 21, 0x4E0811A1);
    P(A, B, C, D, 4, 6, 0xF7537E82);
    P(D, A, B, C, 11, 10, 0xBD3AF235);
    P(C, D, A, B, 2, 15, 0x2AD7D2BB);
    P(B, C, D, A, 9, 21, 0xEB86D391);

#undef F

    ctx->state[0] += A;
    ctx->state[1] += B;
    ctx->state[2] += C;
    ctx->state[3] += D;
}

/*
 * MD5 process buffer
 */
void tiny_md5_update(tiny_md5_context * ctx, unsigned char *input, int ilen)
{
    int fill;
    unsigned long left;

    if (ilen <= 0)
        return;

    left = ctx->total[0] & 0x3F;
    fill = 64 - left;

    ctx->total[0] += ilen;
    ctx->total[0] &= 0xFFFFFFFF;

    if (ctx->total[0] < (unsigned long)ilen)
        ctx->total[1]++;

    if (left && ilen >= fill) {
        memcpy((void *)(ctx->buffer + left), (void *)input, fill);
        md5_process(ctx, ctx->buffer);
        input += fill;
        ilen -= fill;
        left = 0;
    }

    while (ilen >= 64) {
        md5_process(ctx, input);
        input += 64;
        ilen -= 64;
    }

    if (ilen > 0) {
        memcpy((void *)(ctx->buffer + left), (void *)input, ilen);
    }
}

static const unsigned char md5_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
};

/*
 * MD5 final digest  MD5最终摘要
 */
void tiny_md5_finish(tiny_md5_context * ctx, unsigned char output[16])
{
    unsigned long last, padn;
    unsigned long high, low;
    unsigned char msglen[8];

    high = (ctx->total[0] >> 29)
        | (ctx->total[1] << 3);
    low = (ctx->total[0] << 3);

    PUT_ULONG_LE(low, msglen, 0);
    PUT_ULONG_LE(high, msglen, 4);

    last = ctx->total[0] & 0x3F;
    padn = (last < 56) ? (56 - last) : (120 - last);

    tiny_md5_update(ctx, (unsigned char *)md5_padding, padn);
    tiny_md5_update(ctx, msglen, 8);

    PUT_ULONG_LE(ctx->state[0], output, 0);
    PUT_ULONG_LE(ctx->state[1], output, 4);
    PUT_ULONG_LE(ctx->state[2], output, 8);
    PUT_ULONG_LE(ctx->state[3], output, 12);
}

/*
 * output = MD5( input buffer )
 */
void tiny_md5(unsigned char *input, int ilen, unsigned char output[16])
{
    tiny_md5_context ctx;

    tiny_md5_starts(&ctx);
    tiny_md5_update(&ctx, input, ilen);
    tiny_md5_finish(&ctx, output);

    memset(&ctx, 0, sizeof(tiny_md5_context));
}

/*
 * MD5 HMAC context setup MD5 HMAC上下文设置
 */
void tiny_md5_hmac_starts(tiny_md5_context * ctx, unsigned char *key, int keylen)
{
    int i;
    unsigned char sum[16];

    if (keylen > 64) {
        tiny_md5(key, keylen, sum);
        keylen = 16;
        key = sum;
    }

    memset(ctx->ipad, 0x36, 64);
    memset(ctx->opad, 0x5C, 64);

    for (i = 0; i < keylen; i++) {
        ctx->ipad[i] = (unsigned char)(ctx->ipad[i] ^ key[i]);
        ctx->opad[i] = (unsigned char)(ctx->opad[i] ^ key[i]);
    }

    tiny_md5_starts(ctx);
    tiny_md5_update(ctx, ctx->ipad, 64);

    memset(sum, 0, sizeof(sum));
}

/*
 * MD5 HMAC process buffer  MD5 HMAC进程缓冲区
 */
void tiny_md5_hmac_update(tiny_md5_context * ctx, unsigned char *input, int ilen)
{
    tiny_md5_update(ctx, input, ilen);
}

/*
 * MD5 HMAC final digest MD5 HMAC最终摘要
 */
void tiny_md5_hmac_finish(tiny_md5_context * ctx, unsigned char output[16])
{
    unsigned char tmpbuf[16];

    tiny_md5_finish(ctx, tmpbuf);
    tiny_md5_starts(ctx);
    tiny_md5_update(ctx, ctx->opad, 64);
    tiny_md5_update(ctx, tmpbuf, 16);
    tiny_md5_finish(ctx, output);

    memset(tmpbuf, 0, sizeof(tmpbuf));
}

/*
 * output = HMAC-MD5( hmac key, input buffer )
 */
void tiny_md5_hmac(unsigned char *key, int keylen, unsigned char *input, int ilen,unsigned char *od)
{
    unsigned char output[16];
    tiny_md5_context ctx;

    tiny_md5_hmac_starts(&ctx, key, keylen);
    tiny_md5_hmac_update(&ctx, input, ilen);
    tiny_md5_hmac_finish(&ctx, output);

    /*增加*/
    for (uint8_t var = 0; var < 16; ++var)
    {
        *(od+var) = output[var];
    }
    /*增加*/

    memset(&ctx, 0, sizeof(tiny_md5_context));
}
#endif



//测试
int main()
{
	uint8_t data[] = {0x12, 0x34, 0x56, 0x78};
	uint8_t output[16];

	tiny_md5((unsigned char *)&data[0],4,(unsigned char *)&output[0]);
	
    for (uint8_t var = 0; var < 16; ++var)
    {
   		 printf("%02X",output[var]);
    }
	printf("\n");
  
    return 0;
}

//计算结果
//891A26E0581A7F2C9A574CEFF1549EE1