From 1e927ad962b59c9ab49a6a295d99c91e7c8df112 Mon Sep 17 00:00:00 2001
From: Jixun Wu <jixun.moe@gmail.com>
Date: Wed, 15 Dec 2021 22:07:05 +0000
Subject: [PATCH] fix: treat qmcflac/qmcogg as QMCv2 and fallback to QMCv1

(cherry picked from commit 41e588e9864801897fa13eb96a1764baaa5a4ab5)
---
 src/decrypt/qmc.ts   | 29 +++++++++++++++++++++--------
 src/decrypt/qmcv2.ts |  5 ++---
 2 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/src/decrypt/qmc.ts b/src/decrypt/qmc.ts
index 6bc8117..e7fffb9 100644
--- a/src/decrypt/qmc.ts
+++ b/src/decrypt/qmc.ts
@@ -27,11 +27,14 @@ export const HandlerMap: { [key: string]: Handler } = {
     "mflac": {ext: "flac", version: 2},
     "mflac0": {ext: "flac", version: 2},
 
+    // qmcflac / qmcogg:
+    // 有可能是 v2 加密但混用同一个后缀名。
+    "qmcflac": {ext: "flac", version: 2},
+    "qmcogg": {ext: "ogg", version: 2},
+
     "qmc0": {ext: "mp3", version: 1},
     "qmc2": {ext: "ogg", version: 1},
     "qmc3": {ext: "mp3", version: 1},
-    "qmcogg": {ext: "ogg", version: 1},
-    "qmcflac": {ext: "flac", version: 1},
     "bkcmp3": {ext: "mp3", version: 1},
     "bkcflac": {ext: "flac", version: 1},
     "tkm": {ext: "m4a", version: 1},
@@ -45,16 +48,26 @@ export const HandlerMap: { [key: string]: Handler } = {
 export async function Decrypt(file: Blob, raw_filename: string, raw_ext: string): Promise<DecryptResult> {
     if (!(raw_ext in HandlerMap)) throw `Qmc cannot handle type: ${raw_ext}`;
     const handler = HandlerMap[raw_ext];
+    let { version } = handler;
 
     const fileBuffer = await GetArrayBuffer(file);
-    let musicDecoded: Uint8Array;
-    if (handler.version === 1) {
+    let musicDecoded: Uint8Array|undefined;
+
+    if (version === 2) {
+        const v2Decrypted = await DecryptQMCv2(fileBuffer);
+        // 如果 v2 检测失败，降级到 v1 再尝试一次
+        if (v2Decrypted) {
+            musicDecoded = v2Decrypted;
+        } else {
+            version = 1;
+        }
+    }
+
+    if (version === 1) {
         const seed = QmcMaskGetDefault();
         musicDecoded = seed.Decrypt(new Uint8Array(fileBuffer));
-    } else if (handler.version === 2) {
-        musicDecoded = await DecryptQMCv2(fileBuffer);
-    } else {
-        throw new Error(`不支持的加密版本: ${handler.version} (${raw_ext})`);
+    } else if (!musicDecoded) {
+        throw new Error(`解密失败: ${raw_ext}`);
     }
 
     const ext = SniffAudioExt(musicDecoded, handler.ext);
diff --git a/src/decrypt/qmcv2.ts b/src/decrypt/qmcv2.ts
index 68f11dc..f1f5c81 100644
--- a/src/decrypt/qmcv2.ts
+++ b/src/decrypt/qmcv2.ts
@@ -28,7 +28,7 @@ function MergeUint8Array(array: Uint8Array[]): Uint8Array {
  * 如果检测并解密成功，返回解密后的 Uint8Array 数据。
  * @param  {ArrayBuffer} mggBlob 读入的文件 Blob
  * @param  {string}         name 文件名
- * @return {Promise<Uint8Array|null>}
+ * @return {Promise<Uint8Array|false>}
  */
 export async function DecryptQMCv2(mggBlob: ArrayBuffer) {
   // 初始化模组
@@ -53,14 +53,13 @@ export async function DecryptQMCv2(mggBlob: ArrayBuffer) {
   // (pos: i32; len: i32; error: char[??])
   const position = QMCCrypto.getValue(pDetectionResult, "i32");
   const len = QMCCrypto.getValue(pDetectionResult + 4, "i32");
-  const detectionError = QMCCrypto.UTF8ToString(pDetectionResult + 8);
 
   // 释放内存
   QMCCrypto._free(pDetectionBuf);
   QMCCrypto._free(pDetectionResult);
 
   if (!detectOK) {
-    throw new Error("解密失败: \n  " + detectionError);
+    return false;
   }
 
   // 计算解密后文件的大小。