c++判断文件是否被修改（获取文件的MD5值）

需求分析

因为项目中需要检测一个文件是否被篡改，我采用了监测文件的MD5值。
MD5，简单地来说，就是文件的“指纹”。如果原始文件被修改了，那么MD5值也就会跟着发生变化，所以我们可以根据MD5是否变化来判断文件是否被改动。
感谢这位大牛的博客
计算文件的MD5值

实现

md5.h

/* MD5.H - header file for MD5C.C
*//* Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
rights reserved.License to copy and use this software is granted provided that it
is identified as the "RSA Data Security, Inc. MD5 Message-Digest
Algorithm" in all material mentioning or referencing this software
or this function.License is also granted to make and use derivative works provided
that such works are identified as "derived from the RSA Data
Security, Inc. MD5 Message-Digest Algorithm" in all material
mentioning or referencing the derived work.RSA Data Security, Inc. makes no representations concerning either
the merchantability of this software or the suitability of this
software for any particular purpose. It is provided "as is"
without express or implied warranty of any kind.These notices must be retained in any copies of any part of this
documentation and/or software.
*/#ifndef MD5_H
#define MD5_H/* MD5 context. */
typedef struct {UINT4 state[4];                                   /* state (ABCD) */UINT4 count[2];        /* number of bits, modulo 2^64 (lsb first) */unsigned char buffer[64];                         /* input buffer */
} MD5_CTX;void MD5Init(MD5_CTX*);
void MD5Update(MD5_CTX*, unsigned char*, unsigned int);
void MD5Final(unsigned char[16], MD5_CTX*);#endif

md5.cpp

/* MD5.C - RSA Data Security, Inc., MD5 message-digest algorithm
*//* Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
rights reserved.License to copy and use this software is granted provided that it
is identified as the "RSA Data Security, Inc. MD5 Message-Digest
Algorithm" in all material mentioning or referencing this software
or this function.License is also granted to make and use derivative works provided
that such works are identified as "derived from the RSA Data
Security, Inc. MD5 Message-Digest Algorithm" in all material
mentioning or referencing the derived work.RSA Data Security, Inc. makes no representations concerning either
the merchantability of this software or the suitability of this
software for any particular purpose. It is provided "as is"
without express or implied warranty of any kind.These notices must be retained in any copies of any part of this
documentation and/or software.
*/#include "md5global.h"
#include "md5.h"/* Constants for MD5Transform routine.
*/#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21static void MD5Transform(UINT4[4], unsigned char[64]);
static void Encode(unsigned char*, UINT4*, unsigned int);
static void Decode(UINT4*, unsigned char*, unsigned int);
static void MD5_memcpy(POINTER, POINTER, unsigned int);
static void MD5_memset(POINTER, int, unsigned int);static unsigned char 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
};/* F, G, H and I are basic MD5 functions.
*/
#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)))/* ROTATE_LEFT rotates x left n bits.
*/
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))/* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
Rotation is separate from addition to prevent recomputation.
*/
#define FF(a, b, c, d, x, s, ac) { \(a) += F ((b), (c), (d)) + (x) + (UINT4)(ac); \(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define GG(a, b, c, d, x, s, ac) { \(a) += G ((b), (c), (d)) + (x) + (UINT4)(ac); \(a) = ROTATE_LEFT ((a), (s)); \(a) += (b); \}
#define HH(a, b, c, d, x, s, ac) { \(a) += H ((b), (c), (d)) + (x) + (UINT4)(ac); \(a) = ROTATE_LEFT ((a), (s)); \(a) += (b); \}
#define II(a, b, c, d, x, s, ac) { \(a) += I ((b), (c), (d)) + (x) + (UINT4)(ac); \(a) = ROTATE_LEFT ((a), (s)); \(a) += (b); \}/* MD5 initialization. Begins an MD5 operation, writing a new context.
*/
void MD5Init(MD5_CTX* context) /* context */
{context->count[0] = context->count[1] = 0;/* Load magic initialization constants.*/context->state[0] = 0x67452301;context->state[1] = 0xefcdab89;context->state[2] = 0x98badcfe;context->state[3] = 0x10325476;
}/* MD5 block update operation. Continues an MD5 message-digest
operation, processing another message block, and updating the
context.
*/
void MD5Update(MD5_CTX* context, unsigned char* input, unsigned int inputLen)
{unsigned int i, index, partLen;/* Compute number of bytes mod 64 */index = (unsigned int)((context->count[0] >> 3) & 0x3F);/* Update number of bits */if ((context->count[0] += ((UINT4)inputLen << 3))< ((UINT4)inputLen << 3))context->count[1]++;context->count[1] += ((UINT4)inputLen >> 29);partLen = 64 - index;/* Transform as many times as possible.*/if (inputLen >= partLen) {MD5_memcpy((POINTER)&context->buffer[index], (POINTER)input, partLen);MD5Transform(context->state, context->buffer);for (i = partLen; i + 63 < inputLen; i += 64)MD5Transform(context->state, &input[i]);index = 0;}elsei = 0;/* Buffer remaining input */MD5_memcpy((POINTER)&context->buffer[index], (POINTER)&input[i],inputLen - i);
}/* MD5 finalization. Ends an MD5 message-digest operation, writing the
the message digest and zeroizing the context.
*/
void MD5Final(unsigned char digest[16], MD5_CTX* context)
{unsigned char bits[8];unsigned int index, padLen;/* Save number of bits */Encode(bits, context->count, 8);/* Pad out to 56 mod 64.*/index = (unsigned int)((context->count[0] >> 3) & 0x3f);padLen = (index < 56) ? (56 - index) : (120 - index);MD5Update(context, PADDING, padLen);/* Append length (before padding) */MD5Update(context, bits, 8);/* Store state in digest */Encode(digest, context->state, 16);/* Zeroize sensitive information.*/MD5_memset((POINTER)context, 0, sizeof(*context));
}/* MD5 basic transformation. Transforms state based on block.
*/
static void MD5Transform(UINT4 state[4], unsigned char block[64])
{UINT4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];Decode(x, block, 64);/* Round 1 */FF(a, b, c, d, x[0], S11, 0xd76aa478); /* 1 */FF(d, a, b, c, x[1], S12, 0xe8c7b756); /* 2 */FF(c, d, a, b, x[2], S13, 0x242070db); /* 3 */FF(b, c, d, a, x[3], S14, 0xc1bdceee); /* 4 */FF(a, b, c, d, x[4], S11, 0xf57c0faf); /* 5 */FF(d, a, b, c, x[5], S12, 0x4787c62a); /* 6 */FF(c, d, a, b, x[6], S13, 0xa8304613); /* 7 */FF(b, c, d, a, x[7], S14, 0xfd469501); /* 8 */FF(a, b, c, d, x[8], S11, 0x698098d8); /* 9 */FF(d, a, b, c, x[9], S12, 0x8b44f7af); /* 10 */FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 *//* Round 2 */GG(a, b, c, d, x[1], S21, 0xf61e2562); /* 17 */GG(d, a, b, c, x[6], S22, 0xc040b340); /* 18 */GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */GG(b, c, d, a, x[0], S24, 0xe9b6c7aa); /* 20 */GG(a, b, c, d, x[5], S21, 0xd62f105d); /* 21 */GG(d, a, b, c, x[10], S22, 0x2441453); /* 22 */GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */GG(b, c, d, a, x[4], S24, 0xe7d3fbc8); /* 24 */GG(a, b, c, d, x[9], S21, 0x21e1cde6); /* 25 */GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */GG(c, d, a, b, x[3], S23, 0xf4d50d87); /* 27 */GG(b, c, d, a, x[8], S24, 0x455a14ed); /* 28 */GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */GG(d, a, b, c, x[2], S22, 0xfcefa3f8); /* 30 */GG(c, d, a, b, x[7], S23, 0x676f02d9); /* 31 */GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 *//* Round 3 */HH(a, b, c, d, x[5], S31, 0xfffa3942); /* 33 */HH(d, a, b, c, x[8], S32, 0x8771f681); /* 34 */HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */HH(a, b, c, d, x[1], S31, 0xa4beea44); /* 37 */HH(d, a, b, c, x[4], S32, 0x4bdecfa9); /* 38 */HH(c, d, a, b, x[7], S33, 0xf6bb4b60); /* 39 */HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */HH(d, a, b, c, x[0], S32, 0xeaa127fa); /* 42 */HH(c, d, a, b, x[3], S33, 0xd4ef3085); /* 43 */HH(b, c, d, a, x[6], S34, 0x4881d05); /* 44 */HH(a, b, c, d, x[9], S31, 0xd9d4d039); /* 45 */HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */HH(b, c, d, a, x[2], S34, 0xc4ac5665); /* 48 *//* Round 4 */II(a, b, c, d, x[0], S41, 0xf4292244); /* 49 */II(d, a, b, c, x[7], S42, 0x432aff97); /* 50 */II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */II(b, c, d, a, x[5], S44, 0xfc93a039); /* 52 */II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */II(d, a, b, c, x[3], S42, 0x8f0ccc92); /* 54 */II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */II(b, c, d, a, x[1], S44, 0x85845dd1); /* 56 */II(a, b, c, d, x[8], S41, 0x6fa87e4f); /* 57 */II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */II(c, d, a, b, x[6], S43, 0xa3014314); /* 59 */II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */II(a, b, c, d, x[4], S41, 0xf7537e82); /* 61 */II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */II(c, d, a, b, x[2], S43, 0x2ad7d2bb); /* 63 */II(b, c, d, a, x[9], S44, 0xeb86d391); /* 64 */state[0] += a;state[1] += b;state[2] += c;state[3] += d;/* Zeroize sensitive information.*/MD5_memset((POINTER)x, 0, sizeof(x));
}/* Encodes input (UINT4) into output (unsigned char). Assumes len is
a multiple of 4.
*/
static void Encode(unsigned char* output, UINT4* input, unsigned int len)
{unsigned int i, j;for (i = 0, j = 0; j < len; i++, j += 4) {output[j] = (unsigned char)(input[i] & 0xff);output[j + 1] = (unsigned char)((input[i] >> 8) & 0xff);output[j + 2] = (unsigned char)((input[i] >> 16) & 0xff);output[j + 3] = (unsigned char)((input[i] >> 24) & 0xff);}
}/* Decodes input (unsigned char) into output (UINT4). Assumes len is
a multiple of 4.
*/
static void Decode(UINT4* output, unsigned char* input, unsigned int len)
{unsigned int i, j;for (i = 0, j = 0; j < len; i++, j += 4)output[i] = ((UINT4)input[j]) | (((UINT4)input[j + 1]) << 8) |(((UINT4)input[j + 2]) << 16) | (((UINT4)input[j + 3]) << 24);
}/* Note: Replace "for loop" with standard memcpy if possible.
*/static void MD5_memcpy(POINTER output, POINTER input, unsigned int len)
{unsigned int i;for (i = 0; i < len; i++)output[i] = input[i];
}/* Note: Replace "for loop" with standard memset if possible.
*/
static void MD5_memset(POINTER output, int value, unsigned int len)
{unsigned int i;for (i = 0; i < len; i++)((char*)output)[i] = (char)value;
}

md5file.h

#ifndef MD5FILE_H
#define MD5FILE_H#include <string>std::string getFileMD5(const std::string& filename);#endif

md5file.cpp

#include "md5file.h"
#include "md5global.h"
#include "md5.h"#include <fstream>
#include <sstream>
#include <memory>
#include <iomanip>
#include <exception>std::string getFileMD5(const std::string& filename)
{std::ifstream fin(filename.c_str(), std::ifstream::in | std::ifstream::binary);if (fin){MD5_CTX context;MD5Init(&context);fin.seekg(0, fin.end);const auto fileLength = fin.tellg();fin.seekg(0, fin.beg);const int bufferLen = 8192;std::unique_ptr<unsigned char[]> buffer{ new unsigned char[bufferLen] {} };unsigned long long totalReadCount = 0;decltype(fin.gcount()) readCount = 0;// 读取文件内容，调用MD5Update()更新MD5值while (fin.read(reinterpret_cast<char*>(buffer.get()), bufferLen)){readCount = fin.gcount();totalReadCount += readCount;MD5Update(&context, buffer.get(), static_cast<unsigned int>(readCount));}// 处理最后一次读到的数据readCount = fin.gcount();if (readCount > 0){totalReadCount += readCount;MD5Update(&context, buffer.get(), static_cast<unsigned int>(readCount));}fin.close();// 数据完整性检查if (totalReadCount != fileLength){std::ostringstream oss;oss << "FATAL ERROR: read " << filename << " failed!" << std::ends;throw std::runtime_error(oss.str());}unsigned char digest[16];MD5Final(digest, &context);// 获取MD5std::ostringstream oss;for (int i = 0; i < 16; ++i){oss << std::hex << std::setw(2) << std::setfill('0') << static_cast<unsigned int>(digest[i]);}oss << std::ends;return std::move(oss.str());}else{std::ostringstream oss;oss << "FATAL ERROR: " << filename << " can't be opened" << std::ends;throw std::runtime_error(oss.str());}
}

md5global.h

/* GLOBAL.H - RSAREF types and constants
*//* PROTOTYPES should be set to one if and only if the compiler supports
function argument prototyping.
The following makes PROTOTYPES default to 0 if it has not already
been defined with C compiler flags.
*/#ifndef MD5_GLOBAL_H
#define MD5_GLOBAL_H/* POINTER defines a generic pointer type */
typedef unsigned char* POINTER;/* UINT2 defines a two byte word */
typedef unsigned short int UINT2;/* UINT4 defines a four byte word */
typedef unsigned long int UINT4;#endif

main.cpp

#include <windows.h>
#include "md5file.h"
#include <iostream>
#include <winbase.h>using namespace std;#define PATH "D:\\Desktop\\Monitor_TangWeiKang\\UpgradedMonitoringMachine_TangWeiKang\\RecordingSeparation\\code\\VS2019\\DownloadWget\\record.txt"int main(void)
{while(1){//获取文件的MD5值//twk测试//std::cout << getFileMD5(PATH) << std::endl;string FileMD5 = getFileMD5(PATH);Sleep(1000);if(FileMD5.compare(getFileMD5(PATH))==0){cout << "文件没有被修改过" << endl;}else{cout << "文件被修改过l" << endl;}}return 0;
}

结果显示

在txt文件内添加和删除，MD5值是不断改变的

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c++判断文件是否被修改（获取文件的MD5值）

需求分析

实现

结果显示

c++判断文件是否被修改（获取文件的MD5值）相关推荐

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