faet: add support of xmly android (#1)

src/decrypt-worker/crypto/CryptoFactory.ts

@@ -3,6 +3,7 @@ import { CryptoFactory } from './CryptoBase';
 import { QMC1Crypto } from './qmc/qmc_v1';
 import { QMC2Crypto } from './qmc/qmc_v2';
 import { XiamiCrypto } from './xiami/xiami';
+import { XimalayaAndroidCrypto } from './xmly/xmly_android';
 
 export const allCryptoFactories: CryptoFactory[] = [
   // Xiami (*.xm)
@@ -16,4 +17,8 @@ export const allCryptoFactories: CryptoFactory[] = [
 
   // QMCv1 (*.qmcflac)
   QMC1Crypto.make,
+
+  // Ximalaya (Android)
+  XimalayaAndroidCrypto.makeX2M,
+  XimalayaAndroidCrypto.makeX3M,
 ];

src/decrypt-worker/crypto/xmly/xmly_android.key.ts

@@ -0,0 +1,17 @@
+export interface XimalayaAndroidKey {
+  contentKey: string;
+  init: number;
+  step: number;
+}
+
+export const XimalayaX2MKey: XimalayaAndroidKey = {
+  contentKey: 'xmly',
+  init: 0.615243,
+  step: 3.837465,
+};
+
+export const XimalayaX3MKey: XimalayaAndroidKey = {
+  contentKey: '3989d111aad5613940f4fc44b639b292',
+  init: 0.726354,
+  step: 3.948576,
+};

src/decrypt-worker/crypto/xmly/xmly_android.ts

@@ -0,0 +1,29 @@
+import { transformBlob } from '~/decrypt-worker/util/transformBlob';
+import type { CryptoBase } from '../CryptoBase.js';
+import { XimalayaAndroidKey, XimalayaX2MKey, XimalayaX3MKey } from './xmly_android.key.js';
+
+export class XimalayaAndroidCrypto implements CryptoBase {
+  cryptoName = 'Ximalaya/Android';
+  checkByDecryptHeader = true;
+  constructor(private key: XimalayaAndroidKey) {}
+
+  async decrypt(buffer: ArrayBuffer): Promise<Blob> {
+    const { contentKey, init, step } = this.key;
+    return transformBlob(buffer, (p) => {
+      const transformer = p.make.XimalayaAndroid(init, step, contentKey);
+      if (!transformer) {
+        throw new Error('could not make xmly transformer, is key invalid?');
+      }
+
+      return transformer;
+    });
+  }
+
+  public static makeX2M() {
+    return new XimalayaAndroidCrypto(XimalayaX2MKey);
+  }
+
+  public static makeX3M() {
+    return new XimalayaAndroidCrypto(XimalayaX3MKey);
+  }
+}