Change getPublicUrlForMxc function for authmedia

discord/discord-command-handler.js

@@ -11,6 +11,8 @@ const {discord, sync, db, select} = require("../passthrough")
 const api = sync.require("../matrix/api")
 /** @type {import("../matrix/file")} */
 const file = sync.require("../matrix/file")
+/** @type {import("../m2d/converters/utils")} */
+const mxUtils = sync.require("../matrix/utils")
 /** @type {import("../d2m/actions/create-space")} */
 const createSpace = sync.require("../d2m/actions/create-space")
 /** @type {import("./utils")} */
@@ -91,9 +93,8 @@ const commands = [{
 
 			// Current avatar
 			const avatarEvent = await api.getStateEvent(roomID, "m.room.avatar", "")
-			const avatarURLParts = avatarEvent?.url.match(/^mxc:\/\/([^/]+)\/(\w+)$/)
 			let currentAvatarMessage =
-				( avatarURLParts ? `Current room-specific avatar: ${reg.ooye.server_origin}/_matrix/media/r0/download/${avatarURLParts[1]}/${avatarURLParts[2]}`
+				( avatarEvent.url ? `Current room-specific avatar: ${mxUtils.getPublicUrlForMxc(avatarEvent.url)}`
 				: "No avatar. Now's your time to strike. Use `//icon` again with a link or upload to set the room-specific avatar.")
 
 			// Next potential avatar

m2d/converters/event-to-message.js

@@ -15,6 +15,8 @@ const {sync, db, discord, select, from} = passthrough
 const mxUtils = sync.require("../converters/utils")
 /** @type {import("../../discord/utils")} */
 const dUtils = sync.require("../../discord/utils")
+/** @type {import("../../matrix/file")} */
+const file = sync.require("../../matrix/file")
 /** @type {import("./emoji-sheet")} */
 const emojiSheet = sync.require("./emoji-sheet")
 

m2d/converters/utils.js

@@ -1,8 +1,13 @@
 // @ts-check
 
+const assert = require("assert").strict
+
+const passthrough = require("../../passthrough")
+const {db} = passthrough
+
 const {reg} = require("../../matrix/read-registration")
 const userRegex = reg.namespaces.users.map(u => new RegExp(u.regex))
-const assert = require("assert").strict
+
 /** @type {import("xxhash-wasm").XXHashAPI} */ // @ts-ignore
 let hasher = null
 // @ts-ignore
@@ -35,16 +40,6 @@ function eventSenderIsFromDiscord(sender) {
 	return false
 }
 
-/**
- * @param {string} mxc
- * @returns {string?}
- */
-function getPublicUrlForMxc(mxc) {
-	const avatarURLParts = mxc?.match(/^mxc:\/\/([^/]+)\/(\w+)$/)
-	if (avatarURLParts) return `${reg.ooye.server_origin}/_matrix/media/r0/download/${avatarURLParts[1]}/${avatarURLParts[2]}`
-	else return null
-}
-
 /**
  * Event IDs are really big and have more entropy than we need.
  * If we want to store the event ID in the database, we can store a more compact version by hashing it with this.
@@ -213,6 +208,32 @@ async function getViaServersQuery(roomID, api) {
 	return qs
 }
 
+/**
+ * Since the introduction of authenticated media, this can no longer just be the /_matrix/media/r0/download URL
+ * because Discord and Discord users cannot use those URLs. Media now has to be proxied through the bridge.
+ * To avoid the bridge acting as a proxy for *any* media, there is a list of permitted media stored in the database.
+ * (The other approach would be signing the URLs with a MAC (or similar) and adding the signature, but I'm not a
+ * cryptographer, so I don't want to.) To reduce database disk space usage, instead of storing each permitted URL,
+ * we just store its xxhash as a signed (as in +/-, not signature) 64-bit integer, which fits in an SQLite integer field.
+ * @see https://matrix.org/blog/2024/06/26/sunsetting-unauthenticated-media/ background
+ * @see https://matrix.org/blog/2024/06/20/matrix-v1.11-release/ implementation details
+ * @see https://www.sqlite.org/fileformat2.html#record_format SQLite integer field size
+ * @param {string} mxc
+ * @returns {string?}
+ */
+function getPublicUrlForMxc(mxc) {
+	assert(hasher, "xxhash is not ready yet")
+	const avatarURLParts = mxc?.match(/^mxc:\/\/([^/]+)\/(\w+)$/)
+	if (!avatarURLParts) return null
+
+	const serverAndMediaID = `${avatarURLParts[1]}/${avatarURLParts[2]}`
+	const unsignedHash = hasher.h64(serverAndMediaID)
+	const signedHash = unsignedHash - 0x8000000000000000n // shifting down to signed 64-bit range
+	db.prepare("INSERT OR IGNORE INTO media_proxy (permitted_hash) VALUES (?)").run(signedHash)
+
+	return `${reg.ooye.bridge_origin}/download/matrix/${serverAndMediaID}`
+}
+
 module.exports.BLOCK_ELEMENTS = BLOCK_ELEMENTS
 module.exports.eventSenderIsFromDiscord = eventSenderIsFromDiscord
 module.exports.getPublicUrlForMxc = getPublicUrlForMxc

stdin.js

@@ -32,7 +32,6 @@ if (process.stdin.isTTY) {
 		} else {
 			Object.assign(passthrough.repl.context, extraContext)
 		}
-		// @ts-expect-error Says exit isn't assignable to a string
 		sync.addTemporaryListener(passthrough.repl, "exit", () => process.exit())
 	})
 }

test/test.js

@@ -23,6 +23,7 @@ reg.ooye.server_name = "cadence.moe"
 reg.id = "baby" // don't actually take authenticated actions on the server
 reg.as_token = "baby"
 reg.hs_token = "baby"
+reg.ooye.bridge_origin = "https://bridge.example.org"
 reg.ooye.invite = []
 
 const sync = new HeatSync({watchFS: false})

types.d.ts

@@ -21,6 +21,7 @@ export type AppServiceRegistrationConfig = {
 		max_file_size: number
 		server_name: string
 		server_origin: string
+		bridge_origin: string
 		content_length_workaround: boolean
 		include_user_id_in_mxid: boolean
 		invite: string[]