【安全算法之MD5】MD5摘要运算的C语言源码实现-MD5报文摘要的长度是

​ 大家都知道，MD5是一种摘要运算算法，关于更多的摘要算法，可以参考我之前的一篇文章：摘要算法汇总

今天要给大家带来的是MD5摘要运算的源码实现，废话不多说，直接上源码：

先看头文件，什么了一些结构体定义和操作宏定义，以及导出的3个API接口：

复制 #ifndef __MD5_H__ #define __MD5_H__ #ifdef __cplusplus extern “C” { #endif /* __cplusplus */ #include typedef struct _md5_ctx_t { uint32_t count[2]; uint32_t state[4]; uint8_t buffer[64]; } md5_ctx_t; #define F(x,y,z) ((x & y) | (~x & z)) #define G(x,y,z) ((x & z) | (y & ~z)) #define H(x,y,z) (x^y^z) #define I(x,y,z) (y ^ (x | ~z)) #define ROTATE_LEFT(x,n) ((x << n) | (x >> (32-n))) #define MD5_DIGEST_LEN 16 #define FF(a,b,c,d,x,s,ac) \ { \ a += F(b,c,d) + x + ac; \ a = ROTATE_LEFT(a,s); \ a += b; \ } #define GG(a,b,c,d,x,s,ac) \ { \ a += G(b,c,d) + x + ac; \ a = ROTATE_LEFT(a,s); \ a += b; \ } #define HH(a,b,c,d,x,s,ac) \ { \ a += H(b,c,d) + x + ac; \ a = ROTATE_LEFT(a,s); \ a += b; \ } #define II(a,b,c,d,x,s,ac) \ { \ a += I(b,c,d) + x + ac; \ a = ROTATE_LEFT(a,s); \ a += b; \ } extern void crypto_md5_init(md5_ctx_t *ctx); extern void crypto_md5_update(md5_ctx_t *ctx, uint8_t *in, uint32_t in_len); extern void crypto_md5_final(md5_ctx_t *ctx, uint8_t digest[MD5_DIGEST_LEN]); #ifdef __cplusplus } #endif /* __cplusplus */ #endif /*__MD5_H__*/

接下来，上实现源码：

复制 #include #include #include “md5.h” static const unsigned char PADDING[] = { 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 }; void crypto_md5_init(md5_ctx_t *context) { context->count[0] = 0; context->count[1] = 0; context->state[0] = 0x67452301; context->state[1] = 0xEFCDAB89; context->state[2] = 0x98BADCFE; context->state[3] = 0x10325476; } static void crypto_md5_decode(unsigned int *output, unsigned char *input, unsigned int len) { unsigned int i = 0; unsigned int j = 0; while (j < len) { output[i] = (input[j]) | (input[j+1] << 8) | (input[j+2] << 16) | (input[j+3] << 24); i++; j += 4; } } static void crypto_md5_transform(unsigned int state[4], unsigned char block[64]) { unsigned int a = state[0]; unsigned int b = state[1]; unsigned int c = state[2]; unsigned int d = state[3]; unsigned int x[64]; crypto_md5_decode(x,block,64); FF(a, b, c, d, x[ 0], 7, 0xd76aa478); /* 1 */ FF(d, a, b, c, x[ 1], 12, 0xe8c7b756); /* 2 */ FF(c, d, a, b, x[ 2], 17, 0x242070db); /* 3 */ FF(b, c, d, a, x[ 3], 22, 0xc1bdceee); /* 4 */ FF(a, b, c, d, x[ 4], 7, 0xf57c0faf); /* 5 */ FF(d, a, b, c, x[ 5], 12, 0x4787c62a); /* 6 */ FF(c, d, a, b, x[ 6], 17, 0xa8304613); /* 7 */ FF(b, c, d, a, x[ 7], 22, 0xfd469501); /* 8 */ FF(a, b, c, d, x[ 8], 7, 0x698098d8); /* 9 */ FF(d, a, b, c, x[ 9], 12, 0x8b44f7af); /* 10 */ FF(c, d, a, b, x[10], 17, 0xffff5bb1); /* 11 */ FF(b, c, d, a, x[11], 22, 0x895cd7be); /* 12 */ FF(a, b, c, d, x[12], 7, 0x6b901122); /* 13 */ FF(d, a, b, c, x[13], 12, 0xfd987193); /* 14 */ FF(c, d, a, b, x[14], 17, 0xa679438e); /* 15 */ FF(b, c, d, a, x[15], 22, 0x49b40821); /* 16 */ /* Round 2 */ GG(a, b, c, d, x[ 1], 5, 0xf61e2562); /* 17 */ GG(d, a, b, c, x[ 6], 9, 0xc040b340); /* 18 */ GG(c, d, a, b, x[11], 14, 0x265e5a51); /* 19 */ GG(b, c, d, a, x[ 0], 20, 0xe9b6c7aa); /* 20 */ GG(a, b, c, d, x[ 5], 5, 0xd62f105d); /* 21 */ GG(d, a, b, c, x[10], 9, 0x2441453); /* 22 */ GG(c, d, a, b, x[15], 14, 0xd8a1e681); /* 23 */ GG(b, c, d, a, x[ 4], 20, 0xe7d3fbc8); /* 24 */ GG(a, b, c, d, x[ 9], 5, 0x21e1cde6); /* 25 */ GG(d, a, b, c, x[14], 9, 0xc33707d6); /* 26 */ GG(c, d, a, b, x[ 3], 14, 0xf4d50d87); /* 27 */ GG(b, c, d, a, x[ 8], 20, 0x455a14ed); /* 28 */ GG(a, b, c, d, x[13], 5, 0xa9e3e905); /* 29 */ GG(d, a, b, c, x[ 2], 9, 0xfcefa3f8); /* 30 */ GG(c, d, a, b, x[ 7], 14, 0x676f02d9); /* 31 */ GG(b, c, d, a, x[12], 20, 0x8d2a4c8a); /* 32 */ /* Round 3 */ HH(a, b, c, d, x[ 5], 4, 0xfffa3942); /* 33 */ HH(d, a, b, c, x[ 8], 11, 0x8771f681); /* 34 */ HH(c, d, a, b, x[11], 16, 0x6d9d6122); /* 35 */ HH(b, c, d, a, x[14], 23, 0xfde5380c); /* 36 */ HH(a, b, c, d, x[ 1], 4, 0xa4beea44); /* 37 */ HH(d, a, b, c, x[ 4], 11, 0x4bdecfa9); /* 38 */ HH(c, d, a, b, x[ 7], 16, 0xf6bb4b60); /* 39 */ HH(b, c, d, a, x[10], 23, 0xbebfbc70); /* 40 */ HH(a, b, c, d, x[13], 4, 0x289b7ec6); /* 41 */ HH(d, a, b, c, x[ 0], 11, 0xeaa127fa); /* 42 */ HH(c, d, a, b, x[ 3], 16, 0xd4ef3085); /* 43 */ HH(b, c, d, a, x[ 6], 23, 0x4881d05); /* 44 */ HH(a, b, c, d, x[ 9], 4, 0xd9d4d039); /* 45 */ HH(d, a, b, c, x[12], 11, 0xe6db99e5); /* 46 */ HH(c, d, a, b, x[15], 16, 0x1fa27cf8); /* 47 */ HH(b, c, d, a, x[ 2], 23, 0xc4ac5665); /* 48 */ /* Round 4 */ II(a, b, c, d, x[ 0], 6, 0xf4292244); /* 49 */ II(d, a, b, c, x[ 7], 10, 0x432aff97); /* 50 */ II(c, d, a, b, x[14], 15, 0xab9423a7); /* 51 */ II(b, c, d, a, x[ 5], 21, 0xfc93a039); /* 52 */ II(a, b, c, d, x[12], 6, 0x655b59c3); /* 53 */ II(d, a, b, c, x[ 3], 10, 0x8f0ccc92); /* 54 */ II(c, d, a, b, x[10], 15, 0xffeff47d); /* 55 */ II(b, c, d, a, x[ 1], 21, 0x85845dd1); /* 56 */ II(a, b, c, d, x[ 8], 6, 0x6fa87e4f); /* 57 */ II(d, a, b, c, x[15], 10, 0xfe2ce6e0); /* 58 */ II(c, d, a, b, x[ 6], 15, 0xa3014314); /* 59 */ II(b, c, d, a, x[13], 21, 0x4e0811a1); /* 60 */ II(a, b, c, d, x[ 4], 6, 0xf7537e82); /* 61 */ II(d, a, b, c, x[11], 10, 0xbd3af235); /* 62 */ II(c, d, a, b, x[ 2], 15, 0x2ad7d2bb); /* 63 */ II(b, c, d, a, x[ 9], 21, 0xeb86d391); /* 64 */ state[0] += a; state[1] += b; state[2] += c; state[3] += d; } void crypto_md5_update(md5_ctx_t *context, unsigned char *input, unsigned int inputlen) { unsigned int i = 0; unsigned int index = 0; unsigned int partlen = 0; index = (context->count[0] >> 3) & 0x3F; partlen = 64 – index; context->count[0] += inputlen << 3; if(context->count[0] < (inputlen << 3)) context->count[1]++; context->count[1] += inputlen >> 29; if (inputlen >= partlen) { memcpy(&context->buffer[index], input,partlen); crypto_md5_transform(context->state, context->buffer); for (i = partlen; i+64 <= inputlen; i+=64) { crypto_md5_transform(context->state, &input[i]); } index = 0; } else { i = 0; } memcpy(&context->buffer[index], &input[i], inputlen-i); } static void crypto_md5_encode(unsigned char *output,unsigned int *input,unsigned int len) { unsigned int i = 0; unsigned int j = 0; while (j < len) { output[j] = input[i] & 0xFF; output[j+1] = (input[i] >> 8) & 0xFF; output[j+2] = (input[i] >> 16) & 0xFF; output[j+3] = (input[i] >> 24) & 0xFF; i++; j += 4; } } void crypto_md5_final(md5_ctx_t *context, unsigned char digest[16]) { unsigned int index = 0,padlen = 0; unsigned char bits[8]; index = (context->count[0] >> 3) & 0x3F; padlen = (index < 56)?(56-index):(120-index); crypto_md5_encode(bits, context->count, 8); crypto_md5_update(context, (unsigned char *)PADDING, padlen); crypto_md5_update(context, bits, 8); crypto_md5_encode(digest, context->state, 16); }

我们先写一段测试代码测试一下看看：

复制#include #include #include “md5.h” int main(int argc, const char *argv[]) { const char *data = “C1D0F8FB4958670DBA40AB1F3752EF0D”; uint8_t digest_calc[MD5_DIGEST_LEN]; uint8_t digest_exp[MD5_DIGEST_LEN] = “\x4C\x61\x8F\xD1\x4C\x14\x88\x1E\xFB\x13\x35\x2E\x40\x04\x73\xB1”; md5_ctx_t ctx; const char *p_calc = data; uint8_t data_bytes[128]; uint16_t len_bytes; char data_str[128]; if (argc > 1) { p_calc = argv[1]; } crypto_md5_init(&ctx); crypto_md5_update(&ctx, (uint8_t *)p_calc, strlen(p_calc)); crypto_md5_final(&ctx, digest_calc); if (!memcmp(digest_calc, digest_exp, sizeof(digest_calc))) { printf(“MD5 digest test OK\n”); } else { //log_hexdump(“digest_calc”, digest_calc, sizeof(digest_calc)); //log_hexdump(“digest_exp”, digest_exp, sizeof(digest_exp)); printf(“MD5 digest test FAIL\n”); } return 0; }

这个测试案例，是计算一段字符串：”C1D0F8FB4958670DBA40AB1F3752EF0D”的MD5摘要，然后期往的MD5摘要是下面的32字节数据：

“\x4C\x61\x8F\xD1\x4C\x14\x88\x1E\xFB\x13\x35\x2E\x40\x04\x73\xB1”

通过取得计算的结果与期望值进行比对，进而得出运算结果正确与否。

通过运行测试程序，可以发现，运算结果正常。

也可以跟一些算法小工具的结果做下对比，发现，结果也是没有问题的。

以上就是本次对MD5源码的测试，本案例的所有源代码，均可以在我的github上面找到，对你有帮助的话，请帮忙点个star呦，先谢谢了。

更多参考链接

[1] 【安全算法的github仓库】

[2] 【安全算法之概述】一文带你简要了解常见常用的安全算法