decryptio฻n ke(зіц)ys are rειnaðarann

src/downloader/keygen.ts

@@ -0,0 +1,48 @@
+import { LicenseType, Session } from "node-widevine";
+import { env } from "../config.js";
+import { appleMusicApi } from "../api/index.js";
+import { dataUriToBuffer } from "data-uri-to-buffer";
+import * as log from "../log.js";
+import fs from "node:fs";
+import * as psshTools from "pssh-tools";
+
+export async function getWidevineDecryptionKey(psshDataUri: string, trackId: string): Promise<void> {
+    let pssh = Buffer.from(dataUriToBuffer(psshDataUri).buffer);
+
+    const privateKey = Buffer.from(env.WIDEVINE_PRIVATE_KEY, "base64");
+    const identifierBlob = Buffer.from(env.WIDEVINE_CLIENT_ID, "base64");
+    let session = new Session({ privateKey, identifierBlob }, pssh);
+
+    let challenge: Buffer;
+    try {
+        challenge = session.createLicenseRequest(LicenseType.STREAMING);
+    } catch (err) {
+        // for some reason, if gotten from a webplayback manifest, the pssh is in a completely different format
+        // well, somewhat. we have to rebuild the pssh
+        const rebuiltPssh = psshTools.widevine.encodePssh({
+            contentId: "Hiiii", // lol?? i don't know what this is, random slop go!!!!
+            dataOnly: false,
+            keyIds: [Buffer.from(dataUriToBuffer(psshDataUri).buffer).toString("hex")]
+        });
+
+        log.warn("pssh was invalid, treating it as raw data");
+        log.warn("this should not error, unless the pssh data is invalid, too");
+
+        pssh = Buffer.from(rebuiltPssh, "base64");
+        session = new Session({ privateKey, identifierBlob }, pssh);
+        challenge = session.createLicenseRequest(LicenseType.STREAMING);
+    }
+
+    const response = await appleMusicApi.getWidevineLicense(
+        trackId,
+        psshDataUri,
+        challenge.toString("base64")
+    );
+
+    if (typeof response?.license !== "string") { throw "license is missing or not a string! sign that authentication failed (unsupported codec?)"; }
+    const license = session.parseLicense(Buffer.from(response.license, "base64"));
+    if (license.length === 0) { throw "license(s) failed to be parsed. this could be an error for invalid data! (e.x. pssh/challenge)"; }
+
+    log.info(license);
+    fs.writeFileSync("license", response.license, { encoding: "utf-8" });
+}