技术教程 编程教程 网易云VIP音乐NCM文件转MP3,C语言版本。 正文

网易云VIP音乐NCM文件转MP3,C语言版本。

2023-02-18,,,,

前言

网易云的Vip音乐下载下来,格式不是mp3/flac这种通用的音乐格式，而是经过加密的ncm文件。只有用网易云的音乐App才能够打开。于是想到可不可以把.ncm文件转换成mp3或者flac文件，上google查了一下，发现有不少人已经做了这件事，但没有发现C语言版本的，就想着写一个纯C语言版本的ncm转mp3/flac。

NCM文件结构

ncm文件的结构，网上有人解析出来了，分为下面几个部分

信息 大小 说明
Magic Header 10 bytes 文件头
Key Length 4 bytes AES128加密后的RC4密钥长度，字节是按小端排序。
Key Data Key Length 用AES128加密后的RC4密钥。
1. 先按字节对0x64进行异或。
2. AES解密,去除填充部分。
3. 去除最前面'neteasecloudmusic'17个字节，得到RC4密钥。
Music Info Length 4 bytes 音乐相关信息的长度，小端排序。
Music Info Data Music Info Length Json格式音乐信息数据。
1. 按字节对0x63进行异或。
2. 去除最前面22个字节。
3. Base64进行解码。
4. AES解密。
6. 去除前面6个字节得到Json数据。
CRC 4 bytes 跳过
Gap 5 bytes 跳过
Image Size 4 bytes 图片的大小
Image Image Size 图片数据
Music Data - 1. RC4-KSA生成S盒。
2. 用S盒解密（自定义的解密方法)，不是RC4-PRGA解密。

两个AES对应密钥

unsigned char meta_key[] = { 0x23,0x31,0x34,0x6C,0x6A,0x6B,0x5F,0x21,0x5C,0x5D,0x26,0x30,0x55,0x3C,0x27,0x28 };

unsigned char core_key[] = { 0x68,0x7A,0x48,0x52,0x41,0x6D,0x73,0x6F,0x35,0x6B,0x49,0x6E,0x62,0x61,0x78,0x57 };

不得不佩服当初破解这个东西的人，不仅把文件结构摸得请清楚楚，还把密钥也搞到手，应该是个破解大神。有了上面的东西，剩下的就很简单了，按部就班来就行了。

一些算法准备

开始前我们需要把AES算法，BASE64算法,RC4算法和Json解析算法先写好。

除此之外还有一个编码问题，解析出来的ncm文件是用utf-8编码存储的，所以它在中文windows系统下汉字会出现乱码，因为中文windows系统采用的编码是GBK,两者不兼容，所以我们要写一个编码转换算法，将utf8格式字符串转位GBK的。Linux下不用转换，Linux本身就是用UTF-8的。

C语言没有这些库，都要自己来。

AES用GitHub上的

tiny-AES-c
JSON用GitHub上的CJSON

CJSON
Base64和RC4算法比较简单我们自己写

unsigned char* base64_decode(unsigned char* code,int len,int * actLen)

{

    //根据base64表，以字符找到对应的十进制数据

    int table[] = { 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,

             0,0,0,0,0,0,0,62,0,0,0,

             63,52,53,54,55,56,57,58,

             59,60,61,0,0,0,0,0,0,0,0,

             1,2,3,4,5,6,7,8,9,10,11,12,

             13,14,15,16,17,18,19,20,21,

             22,23,24,25,0,0,0,0,0,0,26,

             27,28,29,30,31,32,33,34,35,

             36,37,38,39,40,41,42,43,44,

             45,46,47,48,49,50,51

    };

    long str_len;

    unsigned char* res;

    int i, j;

    //计算解码后的字符串长度

    //判断编码后的字符串后是否有=

    if (strstr(code, "=="))

        str_len = len / 4 * 3 - 2;

    else if (strstr(code, "="))

        str_len = len / 4 * 3 - 1;

    else

        str_len = len / 4 * 3;

    *actLen = str_len;

    res = malloc(sizeof(unsigned char) * str_len + 1);

    res[str_len] = '\0';

    //以4个字符为一位进行解码

    for (i = 0, j = 0; i < len - 2; j += 3, i += 4)

    {

        res[j] = ((unsigned char)table[code[i]]) << 2 | (((unsigned char)table[code[i + 1]]) >> 4);

        res[j + 1] = (((unsigned char)table[code[i + 1]]) << 4) | (((unsigned char)table[code[i + 2]]) >> 2);

        res[j + 2] = (((unsigned char)table[code[i + 2]]) << 6) | ((unsigned char)table[code[i + 3]]);

    }

    return res;

}

RC4生成S盒

//用key生成S盒

/*

* s: s盒

* key: 密钥

* len: 密钥长度

*/

void rc4Init(unsigned char* s, const unsigned char* key, int len)

{

    int i = 0, j = 0;

    unsigned char T[256] = { 0 };

    for (i = 0; i < 256; i++)

    {

        s[i] = i;

        T[i] = key[i % len];

    }

    for (i = 0; i < 256; i++)

    {

        j = (j + s[i] + T[i]) % 256;

        unsigned tmp = s[i];

		s[i]=s[j];

		s[j]=tmp;

    }

}

//针对NCM文件的解密

//异或关系

/*

* s: s盒

* data: 要加密或者解密的数据

* len: data的长度

*/

void rc4PRGA(unsigned char* s, unsigned char* data, int len)

{

    int i = 0;

    int j = 0;

    int k = 0;

    int idx = 0;

    for (idx = 0; idx < len; idx++)

    {

        i = (idx + 1) % 256;

        j = (i + s[i]) % 256;

        k= (s[i] + s[j]) % 256;

        data[idx]^=s[k];  //异或

    }

}

Windows下utf8转GBK

#ifdef WIN32

#include<Windows.h>

//返回转换好的字符串指针

unsigned char* utf8ToGbk(unsigned char*src,int len)

{

	wchar_t* tmp = (wchar_t*)malloc(sizeof(wchar_t) * len+2);

	unsigned char* newSrc = (unsigned char*)malloc(sizeof(unsigned char) * len + 2);

	MultiByteToWideChar(CP_UTF8, 0, src, -1, tmp, len);

	WideCharToMultiByte(CP_ACP, 0, tmp, -1, newSrc, len+2, NULL,NULL);

	return newSrc;

}

#endif

NCM文件解析

按照NCM文件结构一步一步读取数据来进行解析

//fileName:要转换的文件

void readFileData(const char* fileName)

{

	FILE* f;

	f = fopen(fileName, "rb");

	if (!f)

	{

		printf("No such file: %s\n", fileName);

		return;

	}

	unsigned char buf[16];

	int len=0;

	int i = 0;

	unsigned char meta_key[] = { 0x23,0x31,0x34,0x6C,0x6A,0x6B,0x5F,0x21,0x5C,0x5D,0x26,0x30,0x55,0x3C,0x27,0x28 };

	unsigned char core_key[] = { 0x68,0x7A,0x48,0x52,0x41,0x6D,0x73,0x6F,0x35,0x6B,0x49,0x6E,0x62,0x61,0x78,0x57 };

	fseek(f, 10, SEEK_CUR); //f从当前位置移动10个字节

	fread(buf, 1, 4, f);    //读取rc4 key 的长度

	len = (buf[3] << 8 | buf[2]) << 16 | (buf[1] << 8 | buf[0]);

	unsigned char* rc4Key= (unsigned char*)malloc(sizeof(unsigned char) * len);

	fread(rc4Key, 1, len, f);   //读取rc4数据

	//解密rc4密钥

	for (i = 0; i < len; i++)

	{

		rc4Key[i] ^= 0x64;

	}

	struct AES_ctx ctx;

	AES_init_ctx(&ctx, core_key);	//使用core_key密钥

	int packSize = len / 16;	//采用的是AES-ECB加密方式，和Pkcs7padding填充

	for (i = 0; i < packSize; i++)

	{

		AES_ECB_decrypt(&ctx, &rc4Key[i * 16]);

	}

	int pad = rc4Key[len - 1];	//获取填充的长度

	rc4Key[len - pad] = '\0';	//去除填充的部分，得到RC4密钥

	fread(buf, 1, 4, f);    //读取Music Info 长度数据

	len = ((buf[3] << 8 | buf[2]) << 16) | (buf[1] << 8 | buf[0]);

	unsigned char* meta = (unsigned char*)malloc(sizeof(unsigned char) * len);

	fread(meta, 1, len, f); //读取Music Info数据

	//解析Music info信息

	for (i = 0; i < len; i++)

	{

		meta[i] ^= 0x63;

	}

	int act = 0;

	unsigned char* data = base64_decode(&meta[22], len - 22, &act);	//base64解码

	AES_init_ctx(&ctx, meta_key);	//AES解密

	packSize = act / 16;

	for (i = 0; i < packSize; i++)

	{

		AES_ECB_decrypt(&ctx, &data[i * 16]);

	}

	pad = data[act - 1];

	data[act - pad] = '\0';	//去除填充部分

	unsigned char* newData = data;

#ifdef WIN32

	newData = utf8ToGbk(data, strlen(data));

#endif

	cJSON* cjson = cJSON_Parse(&newData[6]);	//json解析，获取格式和名字等

	if (cjson == NULL)

	{

		printf("cjson parse failed\n");

		return;

	}

	//printf("%s\n", cJSON_Print(cjson));	//输出json

	fseek(f, 9, SEEK_CUR);  //从当前位置跳过9个字节

	fread(buf, 1, 4, f);    //读取图片大小

	len = (buf[3] << 8 | buf[2]) << 16 | (buf[1] << 8 | buf[0]);

	unsigned char* img = (unsigned char*)malloc(sizeof(unsigned char) * len);

	fread(img, 1, len, f);  //读取图片数据

	int offset= 1024 * 1024 * 10;    //10MB 音乐数据一般比较大一次读入10MB

	int total = 0;

	int reSize = offset;

	unsigned char* musicData = (unsigned char*)malloc(offset); //10m

	while (!feof(f))

	{

		len = fread(musicData+total, 1, offset, f);	//每次读取10M

		total += len;

		reSize += offset;

	    musicData=realloc(musicData,reSize);	//扩容

	}

	unsigned char sBox[256] = { 0 };	//s盒

	rc4Init(sBox, &rc4Key[17], strlen(&rc4Key[17]));	//用rC4密钥进行初始化s盒

	rc4PRGA(sBox, musicData, total);	//解密

	//拼接文件名(artist + music name+format)

	char* musicName = cJSON_GetObjectItem(cjson, "musicName")->valuestring;

	cJSON* sub = cJSON_GetObjectItem(cjson, "artist");

	char*artist=cJSON_GetArrayItem(cJSON_GetArrayItem(sub, 0),0)->valuestring;

	char* format = cJSON_GetObjectItem(cjson, "format")->valuestring;

	char* saveFileName =(char*)malloc(strlen(musicName) + strlen(artist) + strlen(format)+5);

	sprintf(saveFileName, "%s - %s.%s", artist, musicName, format);

	FILE* fo=fopen(saveFileName, "wb");

	if (fo == NULL)

	{

		printf("The fileName - '%s' is invalid in this system\n", saveFileName);

	}

	else

	{

		fwrite(musicData, 1, total, fo);

		fclose(fo);

	}

#ifdef WIN32

	free(newData);

#endif

	free(data);

	free(meta);

	free(img);

	free(musicData);

	fclose(f);

}
    AES采用的是AES-ECB模式，pack7padding填充方式。即16个字节为一组，如果不够16个字节，那就缺几个字节就填充几个字节，每个字节的值都是缺少的字节数。所以获取最后一个字节的值就知道要填充了几个字节。
    RC4解密那里，不是按RC4的来的，虽说叫RC4，但只有生成S盒那里是一样的，其它的不是按RC4算法来的。
    有些解析出来音乐的名字，系统是不支持的，比如带'/'的，在创建新文件写入时会失败。
    以"結束バンド - ギターと孤独と蒼い惑星.ncm"为例看看它的json数据是怎么样的

{

"musicId": 1991012773,

"musicName": "ギターと孤独と蒼い惑星",

"artist": [["結束バンド", 54103171]],

"albumId": 153542094,

"album": "ギターと孤独と蒼い惑星",

"albumPicDocId": "109951167983448236",

"albumPic": "https://p4.music.126.net/rfstzrVK05hCPjU-4mzSFA==/109951167983448236.jpg",

"bitrate": 320000,

"mp3DocId": "f481d20151f01d5d681d2768d753ad64",

"duration": 229015,

"mvId": 0,

"alias": ["TV动画《孤独摇滚！》插曲"],

"transNames": [],

"format": "mp3",

"flag": 4

}

可以根据需要自由提取需要的信息

完整代码

点击查看代码 
/*

* date:2022-12-12

* author: FL

* purpose: ncm file to mp3

*/

#include <stdio.h>

#include <string.h>

#include <stdlib.h>

#include "aes.h"

#include "cJSON.h"

#ifdef WIN32

#include<Windows.h>

//返回转换好的字符串指针

unsigned char* utf8ToGbk(unsigned char*src,int len)

{

	wchar_t* tmp = (wchar_t*)malloc(sizeof(wchar_t) * len+2);

	unsigned char* newSrc = (unsigned char*)malloc(sizeof(unsigned char) * len + 2);

	MultiByteToWideChar(CP_UTF8, 0, src, -1, tmp, len);	//转为unicode

	WideCharToMultiByte(CP_ACP, 0, tmp, -1, newSrc, len+2, NULL,NULL); //转gbk

	return newSrc;

}

#endif

void swap(unsigned char* a, unsigned char* b)

{

	unsigned char t = *a;

	*a = *b;

	*b = t;

}

//用key生成S盒

/*

* s: s盒

* key: 密钥

* len: 密钥长度

*/

void rc4Init(unsigned char* s, const unsigned char* key, int len)

{

	int i = 0, j = 0;

	unsigned char T[256] = { 0 };

	for (i = 0; i < 256; i++)

	{

		s[i] = i;

		T[i] = key[i % len];

	}

	for (i = 0; i < 256; i++)

	{

		j = (j + s[i] + T[i]) % 256;

		swap(s + i, s + j);

	}

}

//针对NCM文件的解密

//异或关系

/*

* s: s盒

* data: 要加密或者解密的数据

* len: data的长度

*/

void rc4PRGA(unsigned char* s, unsigned char* data, int len)

{

	int i = 0;

	int j = 0;

	int k = 0;

	int idx = 0;

	for (idx = 0; idx < len; idx++)

	{

		i = (idx + 1) % 256;

		j = (i + s[i]) % 256;

		k = (s[i] + s[j]) % 256;

		data[idx] ^= s[k];  //异或

	}

}

//base64 解码

/*

* code: 要解码的数据

*/

unsigned char* base64_decode(unsigned char* code, int len, int* actLen)

{

	//根据base64表，以字符找到对应的十进制数据

	int table[] = { 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,

			 0,0,0,0,0,0,0,62,0,0,0,

			 63,52,53,54,55,56,57,58,

			 59,60,61,0,0,0,0,0,0,0,0,

			 1,2,3,4,5,6,7,8,9,10,11,12,

			 13,14,15,16,17,18,19,20,21,

			 22,23,24,25,0,0,0,0,0,0,26,

			 27,28,29,30,31,32,33,34,35,

			 36,37,38,39,40,41,42,43,44,

			 45,46,47,48,49,50,51

	};

	long str_len;

	unsigned char* res;

	int i, j;

	//计算解码后的字符串长度

	//判断编码后的字符串后是否有=

	if (strstr(code, "=="))

		str_len = len / 4 * 3 - 2;

	else if (strstr(code, "="))

		str_len = len / 4 * 3 - 1;

	else

		str_len = len / 4 * 3;

	*actLen = str_len;

	res = malloc(sizeof(unsigned char) * str_len + 1);

	res[str_len] = '\0';

	//以4个字符为一位进行解码

	for (i = 0, j = 0; i < len - 2; j += 3, i += 4)

	{

		res[j] = ((unsigned char)table[code[i]]) << 2 | (((unsigned char)table[code[i + 1]]) >> 4);

		res[j + 1] = (((unsigned char)table[code[i + 1]]) << 4) | (((unsigned char)table[code[i + 2]]) >> 2);

		res[j + 2] = (((unsigned char)table[code[i + 2]]) << 6) | ((unsigned char)table[code[i + 3]]);

	}

	return res;

}

void readFileData(const char* fileName)

{

	FILE* f;

	f = fopen(fileName, "rb");

	if (!f)

	{

		printf("No such file: %s\n", fileName);

		return;

	}

	unsigned char buf[16];

	int len=0;

	int i = 0;

	unsigned char meta_key[] = { 0x23,0x31,0x34,0x6C,0x6A,0x6B,0x5F,0x21,0x5C,0x5D,0x26,0x30,0x55,0x3C,0x27,0x28 };

	unsigned char core_key[] = { 0x68,0x7A,0x48,0x52,0x41,0x6D,0x73,0x6F,0x35,0x6B,0x49,0x6E,0x62,0x61,0x78,0x57 };

	fseek(f, 10, SEEK_CUR); //f从当前位置移动10个字节

	fread(buf, 1, 4, f);    //读取rc4 key 的长度

	len = (buf[3] << 8 | buf[2]) << 16 | (buf[1] << 8 | buf[0]);

	unsigned char* rc4Key= (unsigned char*)malloc(sizeof(unsigned char) * len);

	fread(rc4Key, 1, len, f);   //读取rc4数据

	//解密rc4密钥

	for (i = 0; i < len; i++)

	{

		rc4Key[i] ^= 0x64;

	}

	struct AES_ctx ctx;

	AES_init_ctx(&ctx, core_key);	//使用core_key密钥

	int packSize = len / 16;	//采用的是AES-ECB加密方式，和Pkcs7padding填充

	for (i = 0; i < packSize; i++)

	{

		AES_ECB_decrypt(&ctx, &rc4Key[i * 16]);

	}

	int pad = rc4Key[len - 1];	//获取填充的长度

	rc4Key[len - pad] = '\0';	//去除填充的部分，得到RC4密钥

	fread(buf, 1, 4, f);    //读取Music Info 长度数据

	len = ((buf[3] << 8 | buf[2]) << 16) | (buf[1] << 8 | buf[0]);

	unsigned char* meta = (unsigned char*)malloc(sizeof(unsigned char) * len);

	fread(meta, 1, len, f); //读取Music Info数据

	//解析Music info信息

	for (i = 0; i < len; i++)

	{

		meta[i] ^= 0x63;

	}

	int act = 0;

	unsigned char* data = base64_decode(&meta[22], len - 22, &act);	//base64解码

	AES_init_ctx(&ctx, meta_key);	//AES解密

	packSize = act / 16;

	for (i = 0; i < packSize; i++)

	{

		AES_ECB_decrypt(&ctx, &data[i * 16]);

	}

	pad = data[act - 1];

	data[act - pad] = '\0';	//去除填充部分

	unsigned char* newData = data;

#ifdef WIN32

	newData = utf8ToGbk(data, strlen(data));

#endif

	cJSON* cjson = cJSON_Parse(&newData[6]);	//json解析，获取格式和名字等

	if (cjson == NULL)

	{

		printf("cjson parse failed\n");

		return;

	}

	//printf("%s\n", cJSON_Print(cjson));	//输出json

	fseek(f, 9, SEEK_CUR);  //从当前位置跳过9个字节

	fread(buf, 1, 4, f);    //读取图片大小

	len = (buf[3] << 8 | buf[2]) << 16 | (buf[1] << 8 | buf[0]);

	unsigned char* img = (unsigned char*)malloc(sizeof(unsigned char) * len);

	fread(img, 1, len, f);  //读取图片数据

	int offset= 1024 * 1024 * 10;    //10MB 音乐数据一般比较大一次读入10MB

	int total = 0;

	int reSize = offset;

	unsigned char* musicData = (unsigned char*)malloc(offset); //10m

	while (!feof(f))

	{

		len = fread(musicData+total, 1, offset, f);	//每次读取10M

		total += len;

		reSize += offset;

	    musicData=realloc(musicData,reSize);	//扩容

	}

	unsigned char sBox[256] = { 0 };	//s盒

	rc4Init(sBox, &rc4Key[17], strlen(&rc4Key[17]));	//用rC4密钥进行初始化s盒

	rc4PRGA(sBox, musicData, total);	//解密

	//拼接文件名(artist + music name+format)

	char* musicName = cJSON_GetObjectItem(cjson, "musicName")->valuestring;

	cJSON* sub = cJSON_GetObjectItem(cjson, "artist");

	char*artist=cJSON_GetArrayItem(cJSON_GetArrayItem(sub, 0),0)->valuestring;

	char* format = cJSON_GetObjectItem(cjson, "format")->valuestring;

	char* saveFileName =(char*)malloc(strlen(musicName) + strlen(artist) + strlen(format)+5);

	sprintf(saveFileName, "%s - %s.%s", artist, musicName, format);

	FILE* fo=fopen(saveFileName, "wb");

	if (fo == NULL)

	{

		printf("The fileName - '%s' is invalid in this system\n", saveFileName);

	}

	else

	{

		fwrite(musicData, 1, total, fo);

		fclose(fo);

	}

#ifdef WIN32

	free(newData);

#endif

	free(data);

	free(meta);

	free(img);

	free(musicData);

	fclose(f);

}

int main(int argc,char**argv)

{

	readFileData("結束バンド - ギターと孤独と蒼い惑星.ncm");

	return 0;

}

GitHub项目

NcmToMp3

星期五女孩

网易云VIP音乐NCM文件转MP3,C语言版本。的相关教程结束。

《网易云VIP音乐NCM文件转MP3,C语言版本。.doc》

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