86 lines
2.7 KiB
JavaScript
86 lines
2.7 KiB
JavaScript
// @ts-check
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const assert = require("assert/strict")
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const {defineEventHandler, getValidatedRouterParams, sendRedirect, createError, H3Event} = require("h3")
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const {z} = require("zod")
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/** @type {import("xxhash-wasm").XXHashAPI} */ // @ts-ignore
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let hasher = null
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// @ts-ignore
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require("xxhash-wasm")().then(h => hasher = h)
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const {discord, as, select} = require("../../passthrough")
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const schema = {
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params: z.object({
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channel_id: z.string().regex(/^[0-9]+$/),
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attachment_id: z.string().regex(/^[0-9]+$/),
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file_name: z.string().regex(/^[-A-Za-z0-9_.,]+$/)
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})
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}
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/**
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* @param {H3Event} event
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* @returns {import("snowtransfer").SnowTransfer}
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*/
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function getSnow(event) {
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/* c8 ignore next */
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return event.context.snow || discord.snow
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}
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/** @type {Map<string, Promise<string>>} */
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const cache = new Map()
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/** @param {string} url */
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function timeUntilExpiry(url) {
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const params = new URL(url).searchParams
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const ex = params.get("ex")
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assert(ex) // refreshed urls from the discord api always include this parameter
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const time = parseInt(ex, 16)*1000 - Date.now()
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if (time > 0) return time
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return false
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}
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function defineMediaProxyHandler(domain) {
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return defineEventHandler(async event => {
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const params = await getValidatedRouterParams(event, schema.params.parse)
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const unsignedHash = hasher.h64(params.attachment_id)
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const signedHash = unsignedHash - 0x8000000000000000n // shifting down to signed 64-bit range
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const row = select("media_proxy", "permitted_hash", {permitted_hash: signedHash}).get()
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if (row == null) {
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throw createError({
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status: 403,
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data: `The file you requested isn't permitted by this media proxy.`
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})
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}
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const url = `https://${domain}/attachments/${params.channel_id}/${params.attachment_id}/${params.file_name}`
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let promise = cache.get(url)
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/** @type {string | undefined} */
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let refreshed
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if (promise) {
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refreshed = await promise
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if (!timeUntilExpiry(refreshed)) promise = undefined
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}
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if (!promise) {
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const snow = getSnow(event)
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promise = snow.channel.refreshAttachmentURLs([url]).then(x => x.refreshed_urls[0].refreshed)
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cache.set(url, promise)
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refreshed = await promise
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const time = timeUntilExpiry(refreshed)
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assert(time) // the just-refreshed URL will always be in the future
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setTimeout(() => {
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cache.delete(url)
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}, time).unref()
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}
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assert(refreshed) // will have been assigned by one of the above branches
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return sendRedirect(event, refreshed)
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})
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}
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as.router.get(`/download/discordcdn/:channel_id/:attachment_id/:file_name`, defineMediaProxyHandler("cdn.discordapp.com"))
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as.router.get(`/download/discordmedia/:channel_id/:attachment_id/:file_name`, defineMediaProxyHandler("media.discordapp.net"))
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