decryptio฻n ke(зіц)ys are rειnaðarann

src/api/appleMusicApi.ts

@@ -18,8 +18,12 @@ export default class AppleMusicApi {
         this.http = axios.create({
             baseURL: ampApiUrl,
             headers: {
+                "Origin": appleMusicHomepageUrl,
                 "Media-User-Token": mediaUserToken,
-                "Origin": appleMusicHomepageUrl
+                // TODO: move somewhere else
+                // this is only used for `getWidevineLicense`
+                "x-apple-music-user-token": mediaUserToken,
+                "x-apple-renewal": true // do i wanna know what this does?
             },
             params: {
                 "l": language
@@ -28,7 +32,7 @@ export default class AppleMusicApi {
     }
 
     public async login(): Promise<void> {
-        this.http.defaults.headers["Authorization"] = `Bearer ${await getToken(appleMusicHomepageUrl)}`;
+        this.http.defaults.headers.common["Authorization"] = `Bearer ${await getToken(appleMusicHomepageUrl)}`;
     }
 
     async getSong<
@@ -57,16 +61,14 @@ export default class AppleMusicApi {
         trackId: string,
         trackUri: string,
         challenge: string
-    ): Promise<string> {
+    ): Promise<{ license: string | undefined }> { // dubious type, doesn't matter much
         return (await this.http.post(licenseApiUrl, {
-            params: {
-                challenge: challenge,
-                "key-system": "com.widevine.alpha",
-                uri: trackUri,
-                adamId: trackId,
-                isLibrary: false,
-                "user-initiated": true
-            }
+            challenge: challenge,
+            "key-system": "com.widevine.alpha",
+            uri: trackUri,
+            adamId: trackId,
+            isLibrary: false,
+            "user-initiated": true
         })).data;
     }
 }

src/config.ts

@@ -22,7 +22,8 @@ const configSchema = z.object({
 const envSchema = z.object({
     MEDIA_USER_TOKEN: z.string(),
     ITUA: z.string(),
-    WIDEVINE_CLIENT_ID: z.string()
+    WIDEVINE_CLIENT_ID: z.string(),
+    WIDEVINE_PRIVATE_KEY: z.string()
 });
 
 // check that `config.toml` actually exists

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" });
+}

src/downloader/song.ts

@@ -3,7 +3,7 @@ import * as log from "../log.js";
 import type { SongAttributes } from "../api/types/appleMusic/attributes.js";
 import hls, { Item } from "parse-hls";
 import axios from "axios";
-// TODO: remove
+import { getWidevineDecryptionKey } from "./keygen.js";
 import { select } from "@inquirer/prompts";
 
 // ugliest type ever
@@ -21,12 +21,14 @@ type HLS = ReturnType<typeof hls.default.parse>;
 // havent had this issue with the small pool i tested before late 2024. what ????
 // i don't get it.
 // i just tried another thing from 2022 ro 2023 and it worked fine
+// SOLVED. widevine keys are not always present in the m3u8 manifest that is default (you can see that in link above, thats why it exists)
+// OH. it doesn't seem to give the keys you want anyway LOLLLLLLL????
+// i'm sure its used for *SOMETHING* so i'll keep it
 
 // SUPER TODO: turn this all into a streaminfo class
 
-// this typing is dubious...
-// TODO: possibly just stop using an array; use union type on generic
-// TODO: add "legacy" fallback
+// SUPER TODO: add "legacy", would use stuff from webplayback, default to this
+// TODO: make widevine/fairplay optional (esp for above)
 async function getStreamInfo(trackMetadata: SongAttributes<["extendedAssetUrls"]>): Promise<void> {
     const m3u8Url = trackMetadata.extendedAssetUrls.enhancedHls;
     const m3u8 = await axios.get(m3u8Url, { responseType: "text" });
@@ -43,9 +45,7 @@ async function getStreamInfo(trackMetadata: SongAttributes<["extendedAssetUrls"]
     const playreadyPssh = getPlayreadyPssh(drmInfos, drmIds);
     const fairplayKey = getFairplayKey(drmInfos, drmIds);
 
-    log.debug("widevine pssh", widevinePssh);
-    log.debug("playready pssh", playreadyPssh);
-    log.debug("fairplay key", fairplayKey);
+    await getWidevineDecryptionKey(widevinePssh, "1615276490");
 }
 
 // i don't think i wanna write all of the values we need. annoying !
@@ -123,6 +123,5 @@ const getPlayreadyPssh = (drmInfos: DrmInfos, drmIds: string[]): string => getDr
 const getFairplayKey = (drmInfos: DrmInfos, drmIds: string[]): string => getDrmData(drmInfos, drmIds, "com.apple.streamingkeydelivery");
 
 // TODO: remove later, this is just for testing
-log.debug(await appleMusicApi.getWebplayback("1758429584"));
-await getStreamInfo((await appleMusicApi.getSong("1758429584")).data[0].attributes);
-
+log.debug(await appleMusicApi.getWebplayback("1615276490"));
+await getStreamInfo((await appleMusicApi.getSong("1615276490")).data[0].attributes);