72 lines
2.6 KiB
TypeScript
72 lines
2.6 KiB
TypeScript
import { Decrypt as RawDecrypt } from './raw';
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import { GetArrayBuffer } from '@/decrypt/utils';
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import { DecryptResult } from '@/decrypt/entity';
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const segmentSize = 0x20;
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function isPrintableAsciiChar(ch: number) {
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return ch >= 0x20 && ch <= 0x7E;
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}
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function isUpperHexChar(ch: number) {
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return (ch >= 0x30 && ch <= 0x39) || (ch >= 0x41 && ch <= 0x46);
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}
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/**
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* @param {Buffer} data
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* @param {Buffer} key
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* @param {boolean} copy
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* @returns Buffer
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*/
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function decryptSegment(data: Uint8Array, key: Uint8Array) {
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for (let i = 0; i < data.byteLength; i++) {
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data[i] -= key[i % segmentSize];
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}
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return Buffer.from(data);
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}
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export async function Decrypt(file: File, raw_filename: string): Promise<DecryptResult> {
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const buf = new Uint8Array(await GetArrayBuffer(file));
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// 咪咕编码的 WAV 文件有很多“空洞”内容，尝试密钥。
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const header = buf.slice(0, 0x100);
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const bytesRIFF = Buffer.from('RIFF', 'ascii');
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const bytesWaveFormat = Buffer.from('WAVEfmt ', 'ascii');
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const possibleKeys = [];
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for (let i = segmentSize; i < segmentSize * 20; i += segmentSize) {
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const possibleKey = buf.slice(i, i + segmentSize);
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if (!possibleKey.every(isUpperHexChar)) continue;
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const tempHeader = decryptSegment(header, possibleKey);
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if (tempHeader.slice(0, 4).compare(bytesRIFF)) continue;
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if (tempHeader.slice(8, 16).compare(bytesWaveFormat)) continue;
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// fmt chunk 大小可以是 16 / 18 / 40。
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const fmtChunkSize = tempHeader.readUInt32LE(0x10);
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if (![16, 18, 40].includes(fmtChunkSize)) continue;
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// 下一个 chunk
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const firstDataChunkOffset = 0x14 + fmtChunkSize;
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const chunkName = tempHeader.slice(firstDataChunkOffset, firstDataChunkOffset + 4);
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if (!chunkName.every(isPrintableAsciiChar)) continue;
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const secondDataChunkOffset = firstDataChunkOffset + 8 + tempHeader.readUInt32LE(firstDataChunkOffset + 4);
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if (secondDataChunkOffset <= header.byteLength) {
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const secondChunkName = tempHeader.slice(secondDataChunkOffset, secondDataChunkOffset + 4);
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if (!secondChunkName.every(isPrintableAsciiChar)) continue;
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}
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possibleKeys.push(Buffer.from(possibleKey).toString('ascii'));
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}
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if (possibleKeys.length <= 0) {
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throw new Error(`ERROR: no suitable key discovered`);
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}
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const decryptionKey = Buffer.from(possibleKeys[0], 'ascii');
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decryptSegment(buf, decryptionKey);
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const musicData = new Blob([buf], { type: 'audio/x-wav' });
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return await RawDecrypt(musicData, raw_filename, 'wav', false);
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}
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