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forked from um/web
web/src/decrypt/kwm.ts

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import {
AudioMimeType,
BytesHasPrefix,
GetArrayBuffer,
GetCoverFromFile,
GetMetaFromFile,
SniffAudioExt
} from "@/decrypt/utils.ts";
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import {Decrypt as RawDecrypt} from "@/decrypt/raw.ts";
import {parseBlob as metaParseBlob} from "music-metadata-browser";
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const MagicHeader = [
0x79, 0x65, 0x65, 0x6C, 0x69, 0x6F, 0x6E, 0x2D,
0x6B, 0x75, 0x77, 0x6F, 0x2D, 0x74, 0x6D, 0x65,
]
const PreDefinedKey = "MoOtOiTvINGwd2E6n0E1i7L5t2IoOoNk"
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export async function Decrypt(file: File, raw_filename: string, _: string) {
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const oriData = new Uint8Array(await GetArrayBuffer(file));
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if (!BytesHasPrefix(oriData, MagicHeader)) {
if (SniffAudioExt(oriData) === "aac") {
return await RawDecrypt(file, raw_filename, "aac", true)
}
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return {status: false, message: "Not a valid kwm file!"}
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}
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let fileKey = oriData.slice(0x18, 0x20)
let mask = createMaskFromKey(fileKey)
let audioData = oriData.slice(0x400);
let lenAudioData = audioData.length;
for (let cur = 0; cur < lenAudioData; ++cur)
audioData[cur] ^= mask[cur % 0x20];
const ext = SniffAudioExt(audioData);
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const mime = AudioMimeType[ext];
let musicBlob = new Blob([audioData], {type: mime});
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const musicMeta = await metaParseBlob(musicBlob);
const {title, artist} = GetMetaFromFile(raw_filename, musicMeta.common.title, musicMeta.common.artist)
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return {
status: true,
album: musicMeta.common.album,
picture: GetCoverFromFile(musicMeta),
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file: URL.createObjectURL(musicBlob),
mime,
title,
artist,
ext
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}
}
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function createMaskFromKey(keyBytes: Uint8Array): Uint8Array {
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let keyView = new DataView(keyBytes.buffer)
let keyStr = keyView.getBigUint64(0, true).toString()
let keyStrTrim = trimKey(keyStr)
let key = new Uint8Array(32)
for (let i = 0; i < 32; i++) {
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key[i] = PreDefinedKey.charCodeAt(i) ^ keyStrTrim.charCodeAt(i)
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}
return key
}
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function trimKey(keyRaw: string): string {
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let lenRaw = keyRaw.length;
let out = keyRaw;
if (lenRaw > 32) {
out = keyRaw.slice(0, 32)
} else if (lenRaw < 32) {
out = keyRaw.padEnd(32, keyRaw)
}
return out
}