1 files changed, 156 insertions, 0 deletions

diff --git a/server/server/middlewares/activitypub.ts b/server/server/middlewares/activitypub.ts
new file mode 100644
index 000000000..0d333061e
--- /dev/null
+++ b/server/server/middlewares/activitypub.ts
@@ -0,0 +1,156 @@
+import { NextFunction, Request, Response } from 'express'
+import { isActorDeleteActivityValid } from '@server/helpers/custom-validators/activitypub/actor.js'
+import { getAPId } from '@server/lib/activitypub/activity.js'
+import { wrapWithSpanAndContext } from '@server/lib/opentelemetry/tracing.js'
+import { ActivityDelete, ActivityPubSignature, HttpStatusCode } from '@peertube/peertube-models'
+import { logger } from '../helpers/logger.js'
+import { isHTTPSignatureVerified, isJsonLDSignatureVerified, parseHTTPSignature } from '../helpers/peertube-crypto.js'
+import { ACCEPT_HEADERS, ACTIVITY_PUB, HTTP_SIGNATURE } from '../initializers/constants.js'
+import { getOrCreateAPActor, loadActorUrlOrGetFromWebfinger } from '../lib/activitypub/actors/index.js'
+
+async function checkSignature (req: Request, res: Response, next: NextFunction) {
+  try {
+    const httpSignatureChecked = await checkHttpSignature(req, res)
+    if (httpSignatureChecked !== true) return
+
+    const actor = res.locals.signature.actor
+
+    // Forwarded activity
+    const bodyActor = req.body.actor
+    const bodyActorId = getAPId(bodyActor)
+    if (bodyActorId && bodyActorId !== actor.url) {
+      const jsonLDSignatureChecked = await checkJsonLDSignature(req, res)
+      if (jsonLDSignatureChecked !== true) return
+    }
+
+    return next()
+  } catch (err) {
+    const activity: ActivityDelete = req.body
+    if (isActorDeleteActivityValid(activity) && activity.object === activity.actor) {
+      logger.debug('Handling signature error on actor delete activity', { err })
+      return res.status(HttpStatusCode.NO_CONTENT_204).end()
+    }
+
+    logger.warn('Error in ActivityPub signature checker.', { err })
+    return res.fail({
+      status: HttpStatusCode.FORBIDDEN_403,
+      message: 'ActivityPub signature could not be checked'
+    })
+  }
+}
+
+function executeIfActivityPub (req: Request, res: Response, next: NextFunction) {
+  const accepted = req.accepts(ACCEPT_HEADERS)
+  if (accepted === false || ACTIVITY_PUB.POTENTIAL_ACCEPT_HEADERS.includes(accepted) === false) {
+    // Bypass this route
+    return next('route')
+  }
+
+  logger.debug('ActivityPub request for %s.', req.url)
+
+  return next()
+}
+
+// ---------------------------------------------------------------------------
+
+export {
+  checkSignature,
+  executeIfActivityPub,
+  checkHttpSignature
+}
+
+// ---------------------------------------------------------------------------
+
+async function checkHttpSignature (req: Request, res: Response) {
+  return wrapWithSpanAndContext('peertube.activitypub.checkHTTPSignature', async () => {
+    // FIXME: compatibility with http-signature < v1.3
+    const sig = req.headers[HTTP_SIGNATURE.HEADER_NAME] as string
+    if (sig && sig.startsWith('Signature ') === true) req.headers[HTTP_SIGNATURE.HEADER_NAME] = sig.replace(/^Signature /, '')
+
+    let parsed: any
+
+    try {
+      parsed = parseHTTPSignature(req, HTTP_SIGNATURE.CLOCK_SKEW_SECONDS)
+    } catch (err) {
+      logger.warn('Invalid signature because of exception in signature parser', { reqBody: req.body, err })
+
+      res.fail({
+        status: HttpStatusCode.FORBIDDEN_403,
+        message: err.message
+      })
+      return false
+    }
+
+    const keyId = parsed.keyId
+    if (!keyId) {
+      res.fail({
+        status: HttpStatusCode.FORBIDDEN_403,
+        message: 'Invalid key ID',
+        data: {
+          keyId
+        }
+      })
+      return false
+    }
+
+    logger.debug('Checking HTTP signature of actor %s...', keyId)
+
+    let [ actorUrl ] = keyId.split('#')
+    if (actorUrl.startsWith('acct:')) {
+      actorUrl = await loadActorUrlOrGetFromWebfinger(actorUrl.replace(/^acct:/, ''))
+    }
+
+    const actor = await getOrCreateAPActor(actorUrl)
+
+    const verified = isHTTPSignatureVerified(parsed, actor)
+    if (verified !== true) {
+      logger.warn('Signature from %s is invalid', actorUrl, { parsed })
+
+      res.fail({
+        status: HttpStatusCode.FORBIDDEN_403,
+        message: 'Invalid signature',
+        data: {
+          actorUrl
+        }
+      })
+      return false
+    }
+
+    res.locals.signature = { actor }
+    return true
+  })
+}
+
+async function checkJsonLDSignature (req: Request, res: Response) {
+  return wrapWithSpanAndContext('peertube.activitypub.JSONLDSignature', async () => {
+    const signatureObject: ActivityPubSignature = req.body.signature
+
+    if (!signatureObject?.creator) {
+      res.fail({
+        status: HttpStatusCode.FORBIDDEN_403,
+        message: 'Object and creator signature do not match'
+      })
+      return false
+    }
+
+    const [ creator ] = signatureObject.creator.split('#')
+
+    logger.debug('Checking JsonLD signature of actor %s...', creator)
+
+    const actor = await getOrCreateAPActor(creator)
+    const verified = await isJsonLDSignatureVerified(actor, req.body)
+
+    if (verified !== true) {
+      logger.warn('Signature not verified.', req.body)
+
+      res.fail({
+        status: HttpStatusCode.FORBIDDEN_403,
+        message: 'Signature could not be verified'
+      })
+      return false
+    }
+
+    res.locals.signature = { actor }
+    return true
+  })
+}