Jixun Wu
3 years ago
committed by
MengYX
MengYX
4 changed files with 129 additions and 19 deletions
@ -0,0 +1,95 @@ |
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import QMCCryptoModule from '@jixun/qmc2-crypto'; |
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// EOF Magic detection.
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const DETECTION_SIZE = 40; |
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// Process in 2m buffer size
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const DECRYPTION_BUF_SIZE = 2 * 1024 * 1024; |
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/** |
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* 解密一个 QMC2 加密的文件。 |
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* |
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* 如果检测并解密成功，返回解密后的 Uint8Array 数组，按顺序拼接即可得到完整文件。 |
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* 若失败，返回 `null`。 |
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* @param {ArrayBuffer} mggBlob 读入的文件 Blob |
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* @param {string} name 文件名 |
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* @return {Promise<Uint8Array[]|null>} |
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*/ |
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export async function decryptMGG(mggBlob: ArrayBuffer) { |
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// 初始化模组
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const QMCCrypto = await QMCCryptoModule(); |
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// 申请内存块，并文件末端数据到 WASM 的内存堆
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const detectionBuf = new Uint8Array(mggBlob.slice(-DETECTION_SIZE)); |
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const pDetectionBuf = QMCCrypto._malloc(detectionBuf.length); |
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QMCCrypto.writeArrayToMemory(detectionBuf, pDetectionBuf); |
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// 检测结果内存块
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const pDetectionResult = QMCCrypto._malloc(QMCCrypto.sizeof_qmc_detection()); |
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// 进行检测
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const detectOK = QMCCrypto.detectKeyEndPosition( |
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pDetectionResult, |
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pDetectionBuf, |
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detectionBuf.length |
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); |
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// 提取结构体内容：
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// (pos: i32; len: i32; error: char[??])
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const position = QMCCrypto.getValue(pDetectionResult, "i32"); |
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const len = QMCCrypto.getValue(pDetectionResult + 4, "i32"); |
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const detectionError = QMCCrypto.UTF8ToString(pDetectionResult + 8); |
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// 释放内存
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QMCCrypto._free(pDetectionBuf); |
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QMCCrypto._free(pDetectionResult); |
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if (detectOK) { |
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// 计算解密后文件的大小。
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// 之前得到的 position 为相对当前检测数据起点的偏移。
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const decryptedSize = mggBlob.byteLength - DETECTION_SIZE + position; |
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// $prog.max = decryptedSize;
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// 提取嵌入到文件的 EKey
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const ekey = new Uint8Array( |
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mggBlob.slice(decryptedSize, decryptedSize + len) |
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); |
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// 解码 UTF-8 数据到 string
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const decoder = new TextDecoder(); |
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const ekey_b64 = decoder.decode(ekey); |
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// 初始化加密与缓冲区
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const hCrypto = QMCCrypto.createInstWidthEKey(ekey_b64); |
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const buf = QMCCrypto._malloc(DECRYPTION_BUF_SIZE); |
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const decryptedParts = []; |
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let offset = 0; |
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let bytesToDecrypt = decryptedSize; |
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while (bytesToDecrypt > 0) { |
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const blockSize = Math.min(bytesToDecrypt, DECRYPTION_BUF_SIZE); |
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// 解密一些片段
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const blockData = new Uint8Array( |
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mggBlob.slice(offset, offset + blockSize) |
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); |
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QMCCrypto.writeArrayToMemory(blockData, buf); |
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QMCCrypto.decryptStream(hCrypto, buf, offset, blockSize); |
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decryptedParts.push(QMCCrypto.HEAPU8.slice(buf, buf + blockSize)); |
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offset += blockSize; |
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bytesToDecrypt -= blockSize; |
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// $prog.value = offset;
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// 避免网页卡死，让 event loop 处理一下其它事件。
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// Worker 应该不需要等待也可以？
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// await new Promise((resolve) => setTimeout(resolve));
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} |
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QMCCrypto._free(buf); |
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hCrypto.delete(); |
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return decryptedParts; |
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} else { |
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throw new Error("ERROR: could not decrypt\n " + detectionError); |
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} |
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} |
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