Merge pull request '优化 QMCCache 解密过程' (#6) from jixunmoe/um-web:refactor/optimise-qm-cache-decode into master

Reviewed-on: #6
This commit is contained in:
Unlock Music Dev 2022-11-21 19:48:05 +00:00
commit 2872ceb3bb
3 changed files with 72 additions and 50 deletions

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@ -0,0 +1,20 @@
import { DecryptBuffer as DecryptQmcCacheBuffer } from '../qmccache';
import fs from 'fs';
const expectedBuffer = fs.readFileSync(__dirname + '/fixture/qmc_cache_expected.bin');
const createInputBuffer = () => {
const buffer = Buffer.alloc(256);
for (let i = buffer.byteLength; i >= 0; i--) {
buffer[i] = i;
}
return buffer;
};
describe('decrypt/qmccache', () => {
it('should decrypt specified buffer correctly', () => {
const input = createInputBuffer();
DecryptQmcCacheBuffer(input);
expect(input).toEqual(expectedBuffer);
});
});

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@ -13,16 +13,18 @@ import { DecryptResult } from '@/decrypt/entity';
import { parseBlob as metaParseBlob } from 'music-metadata-browser'; import { parseBlob as metaParseBlob } from 'music-metadata-browser';
export function DecryptBuffer(buffer: Uint8Array | Buffer) {
let length = buffer.byteLength;
for (let i = 0; i < length; i++) {
let byte = buffer[i] ^ 0xf4; // xor 0xf4
byte = ((byte & 0b0011_1111) << 2) | (byte >> 6); // rol 2
buffer[i] = byte;
}
}
export async function Decrypt(file: Blob, raw_filename: string, _: string): Promise<DecryptResult> { export async function Decrypt(file: Blob, raw_filename: string, _: string): Promise<DecryptResult> {
const buffer = new Uint8Array(await GetArrayBuffer(file)); const buffer = new Uint8Array(await GetArrayBuffer(file));
let length = buffer.length; DecryptBuffer(buffer);
for (let i = 0; i < length; i++) {
buffer[i] ^= 0xf4;
if (buffer[i] <= 0x3f) buffer[i] = buffer[i] * 4;
else if (buffer[i] <= 0x7f) buffer[i] = (buffer[i] - 0x40) * 4 + 1;
else if (buffer[i] <= 0xbf) buffer[i] = (buffer[i] - 0x80) * 4 + 2;
else buffer[i] = (buffer[i] - 0xc0) * 4 + 3;
}
let ext = SniffAudioExt(buffer, ''); let ext = SniffAudioExt(buffer, '');
const newName = SplitFilename(raw_filename); const newName = SplitFilename(raw_filename);
let audioBlob: Blob; let audioBlob: Blob;