网易云ncm一键转flac、mp3等等格式

发送不了链接。。。算了，就说说怎么做的吧。
直接AES128 ECB方式解密。源码奉上
int aes128_ecb_decrypt(const uint8_t *key, uint8_t *in, int in_len, uint8_t *out) {
int outlen;
int temp;
EVP_CIPHER_CTX Object;
EVP_CIPHER_CTX_init(&Object);
EVP_CIPHER_CTX_set_padding(&Object, 1);
if (!EVP_DecryptInit_ex(&Object, EVP_aes_128_ecb(), 0, key, NULL)) {
return -1;
}
if (!EVP_DecryptUpdate(&Object, out, &outlen, in, in_len))
{
return -2;
}
if (!EVP_DecryptFinal_ex(&Object, out + outlen, &temp)) {
return -3;
}
outlen += temp;
EVP_CIPHER_CTX_cleanup(&x);
return outlen;
}
然后就是keybox。大家自己观察这个格式就懂了，文件头22偏移开始是数据段。

关键写出函数
while (n > 1) {
n = fread(buffer, 1, n, f);
for (i = 0; i < n; i++)
{
int j = (i + 1) & 0xff;
buffer[i] ^= box[(box[j] + box[(box[j] + j) & 0xff]) & 0xff];
}
fmusic.write((const char*)buffer, n);
}
关键密匙盒构造函数
uint8_t* build_key_box(uint8_t *key, int key_len) {
uint8_t *box = (uint8_t*)malloc(256);
int i;
for (i = 0; i < 256; ++i)
{
box[i] = (uint8_t)i;
}
uint8_t swap = 0;
uint8_t c = 0;
uint8_t last_byte = 0;
uint8_t key_offset = 0;
for (i = 0; i < 256; ++i)
{
swap = box[i];
c = ((swap + last_byte + key[key_offset++]) & 0xff);
if (key_offset >= key_len) key_offset = 0;
box[i] = box[c]; box[c] = swap;
last_byte = c;
}
return box;
}
终于可以在walkman上听歌了，开心。