feat: added audio ext detection

src/decrypt-worker/crypto/CryptoBase.ts

@@ -1,4 +1,8 @@
 export interface CryptoBase {
+  /**
+   * When returning false, a successful decryption should be checked by its decrypted content instead.
+   */
+  hasSignature(): boolean;
   isSupported(blob: Blob): Promise<boolean>;
   decrypt(blob: Blob): Promise<Blob>;
 }

src/decrypt-worker/crypto/qmc/qmc_v1.ts

@@ -1,5 +1,5 @@
+import { transformBlob } from '~/decrypt-worker/util/transformBlob';
 import type { CryptoBase } from '../CryptoBase';
-import { loadLibParakeet, factory, BlobSink, createArrayBufferReader, TransformResult } from '@jixun/libparakeet';
 
 const key = new Uint8Array([
   0x77, 0x48, 0x32, 0x73, 0xde, 0xf2, 0xc0, 0xc8, 0x95, 0xec, 0x30, 0xb2, 0x51, 0xc3, 0xe1, 0xa0, 0x9e, 0xe6, 0x9d,
@@ -19,33 +19,15 @@ const key = new Uint8Array([
 ]);
 
 export class QMC1Crypto implements CryptoBase {
-  async isSupported(_blob: Blob): Promise<boolean> {
+  hasSignature(): boolean {
+    return false;
+  }
+
+  async isSupported(): Promise<boolean> {
     return true;
   }
 
   async decrypt(blob: Blob): Promise<Blob> {
-    const cleanup: (() => void)[] = [];
-
-    try {
-      const mod = await loadLibParakeet();
-      const transformer = factory.CreateQMCv1Transformer(mod, key);
-      cleanup.push(() => transformer.delete());
-
-      const reader = createArrayBufferReader(await blob.arrayBuffer(), mod);
-      cleanup.push(() => reader.delete());
-
-      const sink = new BlobSink(mod);
-      const writer = sink.getWriter();
-      cleanup.push(() => writer.delete());
-
-      const result = transformer.Transform(writer, reader);
-      if (result !== TransformResult.OK) {
-        throw new Error(`transform failed with error: ${TransformResult[result]} (${result})`);
-      }
-
-      return sink.collectBlob();
-    } finally {
-      cleanup.forEach((clean) => clean());
-    }
+    return transformBlob(blob, (p) => p.make.QMCv1(key));
   }
 }

src/decrypt-worker/crypto/xiami/xiami.ts

@@ -23,6 +23,10 @@ const u8Sub = (a: number, b: number) => {
 };
 
 export class XiamiCrypto implements CryptoBase {
+  hasSignature(): boolean {
+    return true;
+  }
+
   async isSupported(blob: Blob): Promise<boolean> {
     const headerBuffer = await blob.slice(0, 0x10).arrayBuffer();
     const header = new Uint8Array(headerBuffer);

src/decrypt-worker/util/transformBlob.ts

@@ -0,0 +1,31 @@
+import { Transformer, Parakeet, TransformResult, fetchParakeet } from '@jixun/libparakeet';
+
+export async function transformBlob(
+  blob: Blob,
+  transformerFactory: (p: Parakeet) => Transformer | Promise<Transformer>,
+  parakeet?: Parakeet
+) {
+  const cleanup: (() => void)[] = [];
+
+  try {
+    const mod = parakeet ?? (await fetchParakeet());
+    const transformer = await transformerFactory(mod);
+    cleanup.push(() => transformer.delete());
+
+    const reader = mod.make.Reader(await blob.arrayBuffer());
+    cleanup.push(() => reader.delete());
+
+    const sink = mod.make.WriterSink();
+    const writer = sink.getWriter();
+    cleanup.push(() => writer.delete());
+
+    const result = transformer.Transform(writer, reader);
+    if (result !== TransformResult.OK) {
+      throw new Error(`transform failed with error: ${TransformResult[result]} (${result})`);
+    }
+
+    return sink.collectBlob();
+  } finally {
+    cleanup.forEach((clean) => clean());
+  }
+}

src/decrypt-worker/worker.ts

@@ -4,6 +4,7 @@ import { DECRYPTION_WORKER_ACTION_NAME } from './constants';
 import type { CryptoFactory } from './crypto/CryptoBase';
 import { XiamiCrypto } from './crypto/xiami/xiami';
 import { QMC1Crypto } from './crypto/qmc/qmc_v1';
+import { fetchParakeet } from '@jixun/libparakeet';
 
 const bus = new WorkerServerBus();
 onmessage = bus.onmessage;
@@ -16,14 +17,27 @@ const decryptorFactories: CryptoFactory[] = [
   () => new QMC1Crypto(),
 ];
 
+// Use first 4MiB of the file to perform check.
+const TEST_FILE_HEADER_LEN = 1024 * 1024 * 4;
+
 bus.addEventHandler(DECRYPTION_WORKER_ACTION_NAME.DECRYPT, async (blobURI) => {
   const blob = await fetch(blobURI).then((r) => r.blob());
+  const parakeet = await fetchParakeet();
 
   for (const factory of decryptorFactories) {
     const decryptor = factory();
     if (await decryptor.isSupported(blob)) {
-      const decrypted = await decryptor.decrypt(blob);
-      return { decrypted: URL.createObjectURL(decrypted) };
+      const decryptedBlob = await decryptor.decrypt(blob);
+
+      // Check if we had a successful decryption
+      const header = await decryptedBlob.slice(0, TEST_FILE_HEADER_LEN).arrayBuffer();
+      const audioExt = parakeet.detectAudioExtension(header);
+      if (!decryptor.hasSignature() && audioExt === 'bin') {
+        // skip this decryptor result
+        continue;
+      }
+
+      return { decrypted: URL.createObjectURL(decryptedBlob), ext: audioExt };
     }
   }