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forked from um/web
web/src/decrypt/ncm.ts

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import {
AudioMimeType,
BytesHasPrefix,
GetArrayBuffer,
GetImageFromURL,
GetMetaFromFile,
IMusicMeta,
SniffAudioExt,
WriteMetaToFlac,
WriteMetaToMp3,
} from '@/decrypt/utils';
import { parseBlob as metaParseBlob } from 'music-metadata-browser';
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import jimp from 'jimp';
import AES from 'crypto-js/aes';
import PKCS7 from 'crypto-js/pad-pkcs7';
import ModeECB from 'crypto-js/mode-ecb';
import WordArray from 'crypto-js/lib-typedarrays';
import Base64 from 'crypto-js/enc-base64';
import EncUTF8 from 'crypto-js/enc-utf8';
import EncHex from 'crypto-js/enc-hex';
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import { DecryptResult } from '@/decrypt/entity';
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const CORE_KEY = EncHex.parse('687a4852416d736f356b496e62617857');
const META_KEY = EncHex.parse('2331346C6A6B5F215C5D2630553C2728');
const MagicHeader = [0x43, 0x54, 0x45, 0x4e, 0x46, 0x44, 0x41, 0x4d];
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export async function Decrypt(file: File, raw_filename: string, _: string): Promise<DecryptResult> {
return new NcmDecrypt(await GetArrayBuffer(file), raw_filename).decrypt();
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}
interface NcmMusicMeta {
//musicId: number
musicName?: string;
artist?: Array<string | number>[];
format?: string;
album?: string;
albumPic?: string;
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}
interface NcmDjMeta {
mainMusic: NcmMusicMeta;
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}
class NcmDecrypt {
raw: ArrayBuffer;
view: DataView;
offset: number = 0;
filename: string;
format: string = '';
mime: string = '';
audio?: Uint8Array;
blob?: Blob;
oriMeta?: NcmMusicMeta;
newMeta?: IMusicMeta;
image?: { mime: string; buffer: ArrayBuffer; url: string };
constructor(buf: ArrayBuffer, filename: string) {
const prefix = new Uint8Array(buf, 0, 8);
if (!BytesHasPrefix(prefix, MagicHeader)) throw Error('此ncm文件已损坏');
this.offset = 10;
this.raw = buf;
this.view = new DataView(buf);
this.filename = filename;
}
_getKeyData(): Uint8Array {
const keyLen = this.view.getUint32(this.offset, true);
this.offset += 4;
const cipherText = new Uint8Array(this.raw, this.offset, keyLen).map((uint8) => uint8 ^ 0x64);
this.offset += keyLen;
const plainText = AES.decrypt(
// @ts-ignore
{ ciphertext: WordArray.create(cipherText) },
CORE_KEY,
{ mode: ModeECB, padding: PKCS7 },
);
const result = new Uint8Array(plainText.sigBytes);
const words = plainText.words;
const sigBytes = plainText.sigBytes;
for (let i = 0; i < sigBytes; i++) {
result[i] = (words[i >>> 2] >>> (24 - (i % 4) * 8)) & 0xff;
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}
return result.slice(17);
}
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_getKeyBox(): Uint8Array {
const keyData = this._getKeyData();
const box = new Uint8Array(Array(256).keys());
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const keyDataLen = keyData.length;
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let j = 0;
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for (let i = 0; i < 256; i++) {
j = (box[i] + j + keyData[i % keyDataLen]) & 0xff;
[box[i], box[j]] = [box[j], box[i]];
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}
return box.map((_, i, arr) => {
i = (i + 1) & 0xff;
const si = arr[i];
const sj = arr[(i + si) & 0xff];
return arr[(si + sj) & 0xff];
});
}
_getMetaData(): NcmMusicMeta {
const metaDataLen = this.view.getUint32(this.offset, true);
this.offset += 4;
if (metaDataLen === 0) return {};
const cipherText = new Uint8Array(this.raw, this.offset, metaDataLen).map((data) => data ^ 0x63);
this.offset += metaDataLen;
WordArray.create();
const plainText = AES.decrypt(
// @ts-ignore
{
ciphertext: Base64.parse(
// @ts-ignore
WordArray.create(cipherText.slice(22)).toString(EncUTF8),
),
},
META_KEY,
{ mode: ModeECB, padding: PKCS7 },
).toString(EncUTF8);
const labelIndex = plainText.indexOf(':');
let result: NcmMusicMeta;
if (plainText.slice(0, labelIndex) === 'dj') {
const tmp: NcmDjMeta = JSON.parse(plainText.slice(labelIndex + 1));
result = tmp.mainMusic;
} else {
result = JSON.parse(plainText.slice(labelIndex + 1));
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}
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if (result.albumPic) {
result.albumPic = result.albumPic.replace('http://', 'https://') + '?param=500y500';
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}
return result;
}
_getAudio(keyBox: Uint8Array): Uint8Array {
this.offset += this.view.getUint32(this.offset + 5, true) + 13;
const audioData = new Uint8Array(this.raw, this.offset);
let lenAudioData = audioData.length;
for (let cur = 0; cur < lenAudioData; ++cur) audioData[cur] ^= keyBox[cur & 0xff];
return audioData;
}
async _buildMeta() {
if (!this.oriMeta) throw Error('invalid sequence');
const info = GetMetaFromFile(this.filename, this.oriMeta.musicName);
// build artists
let artists: string[] = [];
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if (typeof this.oriMeta.artist === 'string') {
// v3.0: artist 现在可能是字符串了?
artists.push(this.oriMeta.artist);
} else if (Array.isArray(this.oriMeta.artist)) {
this.oriMeta.artist.forEach((artist) => {
if (typeof artist === 'string') {
artists.push(artist);
} else if (Array.isArray(artist) && artist[0] && typeof artist[0] === 'string') {
artists.push(artist[0]);
}
});
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}
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if (artists.length === 0 && info.artist) {
artists = info.artist
.split(',')
.map((val) => val.trim())
.filter((val) => val != '');
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}
if (this.oriMeta.albumPic)
try {
this.image = await GetImageFromURL(this.oriMeta.albumPic);
while (this.image && this.image.buffer.byteLength >= 1 << 24) {
let img = await jimp.read(Buffer.from(this.image.buffer));
await img.resize(Math.round(img.getHeight() / 2), jimp.AUTO);
this.image.buffer = await img.getBufferAsync('image/jpeg');
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}
} catch (e) {
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console.log('fetch cover image failed', e);
}
this.newMeta = { title: info.title, artists, album: this.oriMeta.album, picture: this.image?.buffer };
}
async _writeMeta() {
if (!this.audio || !this.newMeta) throw Error('invalid sequence');
if (!this.blob) this.blob = new Blob([this.audio], { type: this.mime });
const ori = await metaParseBlob(this.blob);
let shouldWrite = !ori.common.album && !ori.common.artists && !ori.common.title;
if (shouldWrite || this.newMeta.picture) {
if (this.format === 'mp3') {
this.audio = WriteMetaToMp3(Buffer.from(this.audio), this.newMeta, ori);
} else if (this.format === 'flac') {
this.audio = WriteMetaToFlac(Buffer.from(this.audio), this.newMeta, ori);
} else {
console.info(`writing meta for ${this.format} is not being supported for now`);
return;
}
this.blob = new Blob([this.audio], { type: this.mime });
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}
}
gatherResult(): DecryptResult {
if (!this.newMeta || !this.blob) throw Error('bad sequence');
return {
title: this.newMeta.title,
artist: this.newMeta.artists?.join('; '),
ext: this.format,
album: this.newMeta.album,
picture: this.image?.url,
file: URL.createObjectURL(this.blob),
blob: this.blob,
mime: this.mime,
};
}
async decrypt() {
const keyBox = this._getKeyBox();
this.oriMeta = this._getMetaData();
this.audio = this._getAudio(keyBox);
this.format = this.oriMeta.format || SniffAudioExt(this.audio);
this.mime = AudioMimeType[this.format];
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try {
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await this._buildMeta();
await this._writeMeta();
} catch (e) {
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console.warn('build/write meta failed, skip.', e);
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}
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return this.gatherResult();
}
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}