feat(QMCv2): add decoder

(cherry picked from commit 29ac94d1fe52e666fda619f8716d2bc0b120a9ee)
This commit is contained in:
MengYX 2021-12-17 06:07:43 +08:00
parent 76c3887eec
commit 334864f6d8
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GPG Key ID: E63F9C7303E8F604
8 changed files with 107 additions and 6 deletions

32
src/decrypt/qmc.test.ts Normal file
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@ -0,0 +1,32 @@
import fs from "fs";
import {QmcDecoder} from "@/decrypt/qmc";
import {BytesEqual} from "@/decrypt/utils";
function loadTestDataDecoder(name: string): {
cipherText: Uint8Array,
clearText: Uint8Array
} {
const cipherBody = fs.readFileSync(`./testdata/${name}_raw.bin`);
const cipherSuffix = fs.readFileSync(`./testdata/${name}_suffix.bin`);
const cipherText = new Uint8Array(cipherBody.length + cipherSuffix.length);
cipherText.set(cipherBody);
cipherText.set(cipherSuffix, cipherBody.length);
return {
cipherText,
clearText: fs.readFileSync(`testdata/${name}_target.bin`)
}
}
test("qmc: real file", async () => {
const cases = ["mflac0_rc4", "mflac_map", "mgg_map", "qmc0_static"]
for (const name of cases) {
const {clearText, cipherText} = loadTestDataDecoder(name)
const c = new QmcDecoder(cipherText)
const buf = c.decrypt()
expect(BytesEqual(buf, clearText)).toBeTruthy()
}
})

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@ -1,4 +1,4 @@
import {QmcStaticCipher} from "./qmc_cipher";
import {QmcMapCipher, QmcRC4Cipher, QmcStaticCipher, StreamCipher} from "./qmc_cipher";
import {
AudioMimeType,
GetArrayBuffer,
@ -16,6 +16,7 @@ import {DecryptQMCv2} from "./qmcv2";
import iconv from "iconv-lite";
import {DecryptResult} from "@/decrypt/entity";
import {queryAlbumCover} from "@/utils/api";
import {QmcDecryptKey} from "@/decrypt/qmc_key";
interface Handler {
ext: string
@ -137,3 +138,63 @@ async function getCoverImage(title: string, artist?: string, album?: string): Pr
}
return ""
}
export class QmcDecoder {
file: Uint8Array
size: number
decoded: boolean = false
audioSize?: number
cipher?: StreamCipher
constructor(file: Uint8Array) {
this.file = file
this.size = file.length
this.searchKey()
}
decrypt(): Uint8Array {
if (!this.cipher) {
throw new Error("no cipher found")
}
if (!this.audioSize || this.audioSize <= 0) {
throw new Error("invalid audio size")
}
const audioBuf = this.file.subarray(0, this.audioSize)
if (!this.decoded) {
this.cipher.decrypt(audioBuf, 0)
this.decoded = true
}
return audioBuf
}
private searchKey() {
const last4Byte = this.file.slice(this.size - 4);
const textEnc = new TextDecoder()
if (textEnc.decode(last4Byte) === 'QTag') {
const sizeBuf = this.file.slice(this.size - 8, this.size - 4)
const sizeView = new DataView(sizeBuf.buffer, sizeBuf.byteOffset)
const keySize = sizeView.getUint32(0, false)
this.audioSize = this.size - keySize - 8
const rawKey = this.file.subarray(this.audioSize, this.size - 8)
const keyEnd = rawKey.findIndex(v => v == ','.charCodeAt(0))
const keyDec = QmcDecryptKey(rawKey.subarray(0, keyEnd))
this.cipher = new QmcRC4Cipher(keyDec)
} else {
const sizeView = new DataView(last4Byte.buffer, last4Byte.byteOffset);
const keySize = sizeView.getUint32(0, true)
if (keySize < 0x300) {
this.audioSize = this.size - keySize - 4
const rawKey = this.file.subarray(this.audioSize, this.size - 4)
const keyDec = QmcDecryptKey(rawKey)
this.cipher = new QmcMapCipher(keyDec)
} else {
this.audioSize = this.size
this.cipher = new QmcStaticCipher()
}
}
}
}

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@ -1,4 +1,4 @@
import {DecryptKey, simpleMakeKey,} from "@/decrypt/qmc_key";
import {QmcDecryptKey, simpleMakeKey,} from "@/decrypt/qmc_key";
import fs from "fs";
test("key dec: make simple key", () => {
@ -23,7 +23,7 @@ test("key dec: real file", async () => {
const cases = ["mflac_map", "mgg_map", "mflac0_rc4"]
for (const name of cases) {
const {clearText, cipherText} = loadTestDataKeyDecrypt(name)
const buf = DecryptKey(cipherText)
const buf = QmcDecryptKey(cipherText)
expect(buf).toStrictEqual(clearText)
}

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@ -83,8 +83,9 @@ function decryptTencentTea(inBuf: Uint8Array, key: Uint8Array): Uint8Array {
return outBuf
}
export function DecryptKey(raw: Uint8Array): Uint8Array {
const rawDec = Buffer.from(raw.toString(), 'base64')
export function QmcDecryptKey(raw: Uint8Array): Uint8Array {
const textDec = new TextDecoder()
const rawDec = Buffer.from(textDec.decode(raw), 'base64')
let n = rawDec.length;
if (n < 16) {
throw Error("key length is too short")

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@ -32,6 +32,13 @@ export function BytesHasPrefix(data: Uint8Array, prefix: number[]): boolean {
})
}
export function BytesEqual(a: Uint8Array, b: Uint8Array,): boolean {
if (a.length != b.length) return false
return a.every((val, idx) => {
return val === b[idx];
})
}
export function SniffAudioExt(data: Uint8Array, fallback_ext: string = "mp3"): string {
if (BytesHasPrefix(data, MP3_HEADER)) return "mp3"

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testdata/qmc0_static_raw.bin vendored Normal file

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testdata/qmc0_static_suffix.bin vendored Normal file
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testdata/qmc0_static_target.bin vendored Normal file

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