technitium-console/hub/server.ts

/*
The hub: a small server that impersonates ONE Technitium DNS Server for the console and
answers from several real ones.

    node --experimental-strip-types hub/server.ts

It serves the console's static build and a read-only, Technitium-compatible `/api/*`.
A call aimed at one server (`node=<id>`) is forwarded to it with that server's token; a
call with no node (or `node=cluster`) asks every server in parallel and merges the
answers (see merge.ts). Anything that would change data is refused.
*/
import http from 'node:http'
import { createReadStream } from 'node:fs'
import { stat } from 'node:fs/promises'
import path from 'node:path'
import { fileURLToPath } from 'node:url'
import { loadConfig, HUB_VERSION, type HubConfig, type HubServer } from './config.ts'
import { Upstream, UpstreamError, type Params } from './upstream.ts'
import { Sessions } from './session.ts'
import {
  mergeQueryLogs,
  mergeSettled,
  mergeStats,
  mergeTopResponses,
  type DashboardStats,
  type QueryLogPage,
  type Settled,
  type TopEntry,
} from './merge.ts'

type Json = Record<string, unknown>

const MAX_BODY = 64 * 1024

/* Paths relative to `/api/`. Anything not listed here is refused with 403. */
const READ_ENDPOINTS = new Set([
  'dashboard/stats/get',
  'dashboard/stats/getTop',
  'dashboard/metrics/json',
  'apps/list',
  'logs/query',
  'logs/list',
  'settings/get',
  'user/checkForUpdate',
  'admin/cluster/state',
])

const TYPES: Record<string, string> = {
  '.html': 'text/html; charset=utf-8',
  '.js': 'text/javascript; charset=utf-8',
  '.mjs': 'text/javascript; charset=utf-8',
  '.css': 'text/css; charset=utf-8',
  '.woff2': 'font/woff2',
  '.woff': 'font/woff',
  '.png': 'image/png',
  '.ico': 'image/x-icon',
  '.json': 'application/json; charset=utf-8',
  '.svg': 'image/svg+xml',
  '.txt': 'text/plain; charset=utf-8',
  '.map': 'application/json; charset=utf-8',
  '.webmanifest': 'application/manifest+json',
}

const HTML_HEADERS = {
  'content-security-policy': "default-src 'self'; img-src 'self' data:; style-src 'self' 'unsafe-inline'",
  'x-content-type-options': 'nosniff',
}

function send(res: http.ServerResponse, code: number, body: unknown): void {
  const text = JSON.stringify(body)
  res.writeHead(code, {
    'content-type': 'application/json; charset=utf-8',
    'cache-control': 'no-store',
    'content-length': Buffer.byteLength(text),
  })
  res.end(text)
}

const fail = (errorMessage: string): Json => ({ status: 'error', errorMessage })

async function readForm(req: http.IncomingMessage): Promise<URLSearchParams> {
  if (req.method !== 'POST') return new URLSearchParams()
  const chunks: Buffer[] = []
  let size = 0
  for await (const chunk of req) {
    size += (chunk as Buffer).length
    if (size > MAX_BODY) break
    chunks.push(chunk as Buffer)
  }
  const type = String(req.headers['content-type'] ?? '')
  if (size > MAX_BODY || !type.includes('application/x-www-form-urlencoded')) return new URLSearchParams()
  return new URLSearchParams(Buffer.concat(chunks).toString('utf8'))
}

function bearer(req: http.IncomingMessage): string | null {
  const header = String(req.headers.authorization ?? '')
  return header.startsWith('Bearer ') ? header.slice(7).trim() : null
}

function positive(value: string | undefined, fallback: number): number {
  const n = Number(value)
  return Number.isInteger(n) && n > 0 ? n : fallback
}

export function createHub(config: HubConfig): http.Server {
  const upstream = new Upstream(config)
  const sessions = new Sessions(config)
  const byId = new Map(config.servers.map((s) => [s.id, s]))

  /* Ask every server; the ones that fail become warnings (see mergeSettled). */
  async function everywhere<T>(apiPath: string, params: Params): Promise<Settled<T>[]> {
    const results = await Promise.allSettled(config.servers.map((s) => upstream.call(s, apiPath, params)))
    return results.map((r, i): Settled<T> => {
      const node = config.servers[i].id
      return r.status === 'fulfilled'
        ? { node, ok: true, data: r.value as T }
        : { node, ok: false, error: r.reason instanceof Error ? r.reason.message : 'failed' }
    })
  }

  /* `warnings` is given only by the aggregate answers (empty when every server answered), so the
     console can tell "all back" from "not an aggregate" and clear its warning only on the former. */
  function ok(response: unknown, warnings?: string[]): Json {
    return warnings === undefined ? { status: 'ok', response } : { status: 'ok', response, hubWarnings: warnings }
  }

  async function single(server: HubServer, apiPath: string, params: Params): Promise<Json> {
    try {
      return ok(await upstream.call(server, apiPath, params))
    } catch (e) {
      if (e instanceof UpstreamError) {
        return fail(e.kind === 'unreachable' ? `${server.id} did not answer: ${e.message}` : `${server.id}: ${e.message}`)
      }
      throw e
    }
  }

  async function aggregate(apiPath: string, params: Params): Promise<Json> {
    try {
      switch (apiPath) {
        case 'dashboard/stats/get': {
          const { data, warnings } = mergeSettled(await everywhere<DashboardStats>(apiPath, params))
          return ok(mergeStats(data), warnings)
        }
        case 'dashboard/stats/getTop': {
          const { data, warnings } = mergeSettled(await everywhere<Record<string, TopEntry[]>>(apiPath, params))
          const limit = params.limit === undefined ? undefined : positive(params.limit, 1000)
          return ok(mergeTopResponses(data, limit), warnings)
        }
        case 'logs/query': {
          const pageNumber = positive(params.pageNumber, 1)
          const entriesPerPage = positive(params.entriesPerPage, 25)
          // Page N of the merged list is cut from the head of every server's list.
          const asked = { ...params, pageNumber: '1', entriesPerPage: String(pageNumber * entriesPerPage) }
          const settled = await everywhere<QueryLogPage>(apiPath, asked)
          const { data, warnings } = mergeSettled(settled)
          // Only the servers that answered, in server order, so the i-th page is the i-th survivor's.
          const answered = settled.filter((r) => r.ok).map((r) => r.node)
          const pages = data.map((page, i) => ({ node: answered[i], page }))
          return ok(mergeQueryLogs(pages, { pageNumber, entriesPerPage, descending: params.descendingOrder !== 'false' }), warnings)
        }
        case 'apps/list': {
          const { data, warnings } = mergeSettled(await everywhere<{ apps?: { name: string }[] }>(apiPath, params))
          const seen = new Map<string, { name: string }>()
          for (const r of data) for (const app of r.apps ?? []) if (!seen.has(app.name)) seen.set(app.name, app)
          return ok({ ...data[0], apps: [...seen.values()] }, warnings)
        }
        default:
          // Everything else read-only is answered by the first server.
          return await single(config.servers[0], apiPath, params)
      }
    } catch (e) {
      if (e instanceof Error && !(e instanceof UpstreamError)) return fail(e.message)
      throw e
    }
  }

  async function api(req: http.IncomingMessage, res: http.ServerResponse, apiPath: string, url: URL): Promise<void> {
    const form = await readForm(req)
    const params: Params = {}
    for (const [k, v] of url.searchParams) params[k] = v
    for (const [k, v] of form) params[k] = v

    // Public and session endpoints.
    if (apiPath === 'status') {
      send(res, 200, { status: 'ok', hasDefaultCredentials: false, ssoEnabled: false })
      return
    }
    if (apiPath === 'user/login') {
      const token = sessions.login(params.user ?? '', params.pass ?? '')
      send(res, 200, token === null ? fail(`Invalid username or password for user: ${params.user ?? ''}`) : sessions.body(token))
      return
    }

    const token = bearer(req) ?? params.token ?? null
    if (!sessions.touch(token)) {
      send(res, 200, { status: 'invalid-token', errorMessage: 'Invalid token or session expired.' })
      return
    }
    if (apiPath === 'user/session/get') {
      send(res, 200, sessions.body(token as string))
      return
    }
    if (apiPath === 'user/logout') {
      sessions.logout(token as string)
      send(res, 200, { status: 'ok' })
      return
    }
    if (!READ_ENDPOINTS.has(apiPath)) {
      send(res, 403, fail('The hub is read-only.'))
      return
    }
    if (apiPath === 'user/checkForUpdate') {
      send(res, 200, ok({ updateAvailable: false }))
      return
    }
    if (apiPath === 'admin/cluster/state') {
      send(
        res,
        200,
        ok({
          version: HUB_VERSION,
          dnsServerDomain: config.domain,
          clusterInitialized: true,
          clusterDomain: config.domain,
          clusterNodes: config.servers.map((s, i) => ({
            id: i + 1,
            name: s.id,
            url: s.url,
            ipAddresses: [],
            type: i === 0 ? 'Primary' : 'Secondary',
            state: 'Connected',
          })),
        }),
      )
      return
    }

    // What the real servers get: the caller's params minus the hub's own.
    const { node = '', token: _token, ...forward } = params
    const server = byId.get(node)
    if (server !== undefined) {
      send(res, 200, await single(server, apiPath, forward))
      return
    }
    if (node !== '' && node !== 'cluster') {
      send(res, 200, fail(`Unknown node: ${node}`))
      return
    }
    send(res, 200, await aggregate(apiPath, forward))
  }

  async function serveStatic(req: http.IncomingMessage, res: http.ServerResponse, url: URL): Promise<void> {
    if (req.method !== 'GET' && req.method !== 'HEAD') {
      res.writeHead(405, { allow: 'GET, HEAD' }).end()
      return
    }
    const root = path.resolve(config.staticDir)
    let pathname: string
    try {
      pathname = decodeURIComponent(url.pathname)
    } catch {
      res.writeHead(400).end()
      return
    }
    const target = path.resolve(root, '.' + pathname)
    if (pathname.includes('\0') || (target !== root && !target.startsWith(root + path.sep))) {
      res.writeHead(403).end()
      return
    }

    let file = target
    let info = await stat(target).catch(() => null)
    if (info?.isDirectory()) {
      const index = path.join(target, 'index.html')
      if ((await stat(index).catch(() => null))?.isFile() !== true) info = null
      else if (!pathname.endsWith('/')) {
        // As Technitium: `/x` -> `/x/` when the folder has an index.
        res.writeHead(301, { location: `${url.pathname}/${url.search}` }).end()
        return
      } else {
        file = index
        info = await stat(index)
      }
    }
    if (info === null || !info.isFile()) {
      res.writeHead(404, { 'content-type': 'text/plain; charset=utf-8' }).end('Not found')
      return
    }

    const ext = path.extname(file).toLowerCase()
    const headers: Record<string, string | number> = {
      'content-type': TYPES[ext] ?? 'application/octet-stream',
      'content-length': info.size,
    }
    if (ext === '.html') Object.assign(headers, HTML_HEADERS, { 'cache-control': 'no-cache' })
    res.writeHead(200, headers)
    if (req.method === 'HEAD') {
      res.end()
      return
    }
    createReadStream(file).on('error', () => res.destroy()).pipe(res)
  }

  return http.createServer((req, res) => {
    void (async () => {
      try {
        const url = new URL(req.url ?? '/', 'http://hub')
        // The console may sit at a sub path: any `<prefix>/api/<path>` is the API.
        const match = /^(?:.*\/)?api\/(.+?)\/?$/.exec(url.pathname)
        if (match !== null) await api(req, res, match[1], url)
        else await serveStatic(req, res, url)
      } catch (e) {
        console.error('hub error:', e instanceof Error ? e.message : e)
        if (!res.headersSent) send(res, 500, fail('Internal hub error.'))
        else res.destroy()
      }
    })()
  })
}

/* Run directly (not imported by the tests). */
if (process.argv[1] !== undefined && path.resolve(process.argv[1]) === fileURLToPath(import.meta.url)) {
  let config: HubConfig
  try {
    config = loadConfig()
  } catch (e) {
    console.error(`hub: ${e instanceof Error ? e.message : String(e)}`)
    process.exit(1)
  }
  createHub(config).listen(config.port, () => {
    console.log(`Hub ${HUB_VERSION} on :${config.port}, servers: ${config.servers.map((s) => s.id).join(', ')}`)
  })
}