From 878f56b411279cd9865a7ec05f1d14c9f70f6187 Mon Sep 17 00:00:00 2001
From: Andrew Godwin
Date: Sat, 12 Nov 2022 21:14:21 -0700
Subject: Post URIs and host-meta

---
 users/views/activitypub.py | 148 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 148 insertions(+)
 create mode 100644 users/views/activitypub.py

(limited to 'users/views/activitypub.py')

diff --git a/users/views/activitypub.py b/users/views/activitypub.py
new file mode 100644
index 0000000..54f04bc
--- /dev/null
+++ b/users/views/activitypub.py
@@ -0,0 +1,148 @@
+import json
+
+from asgiref.sync import async_to_sync
+from django.http import Http404, HttpResponse, HttpResponseBadRequest, JsonResponse
+from django.utils.decorators import method_decorator
+from django.views.decorators.csrf import csrf_exempt
+from django.views.generic import View
+
+from core.ld import canonicalise
+from core.signatures import (
+    HttpSignature,
+    LDSignature,
+    VerificationError,
+    VerificationFormatError,
+)
+from users.models import Identity, InboxMessage
+from users.shortcuts import by_handle_or_404
+
+
+class HttpResponseUnauthorized(HttpResponse):
+    status_code = 401
+
+
+class HostMeta(View):
+    """
+    Returns a canned host-meta response
+    """
+
+    def get(self, request):
+        return HttpResponse(
+            """<?xml version="1.0" encoding="UTF-8"?>
+            <XRD xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0">
+            <Link rel="lrdd" template="https://%s/.well-known/webfinger?resource={uri}"/>
+            </XRD>"""
+            % request.META["HTTP_HOST"],
+            content_type="application/xml",
+        )
+
+
+class Webfinger(View):
+    """
+    Services webfinger requests
+    """
+
+    def get(self, request):
+        resource = request.GET.get("resource")
+        if not resource.startswith("acct:"):
+            raise Http404("Not an account resource")
+        handle = resource[5:].replace("testfedi", "feditest")
+        identity = by_handle_or_404(request, handle)
+        return JsonResponse(
+            {
+                "subject": f"acct:{identity.handle}",
+                "aliases": [
+                    identity.urls.view_short.full(),
+                ],
+                "links": [
+                    {
+                        "rel": "http://webfinger.net/rel/profile-page",
+                        "type": "text/html",
+                        "href": identity.urls.view_short.full(),
+                    },
+                    {
+                        "rel": "self",
+                        "type": "application/activity+json",
+                        "href": identity.actor_uri,
+                    },
+                ],
+            }
+        )
+
+
+class Actor(View):
+    """
+    Returns the AP Actor object
+    """
+
+    def get(self, request, handle):
+        identity = by_handle_or_404(self.request, handle)
+        response = {
+            "@context": [
+                "https://www.w3.org/ns/activitystreams",
+                "https://w3id.org/security/v1",
+            ],
+            "id": identity.actor_uri,
+            "type": "Person",
+            "inbox": identity.actor_uri + "inbox/",
+            "preferredUsername": identity.username,
+            "publicKey": {
+                "id": identity.public_key_id,
+                "owner": identity.actor_uri,
+                "publicKeyPem": identity.public_key,
+            },
+            "published": identity.created.strftime("%Y-%m-%dT%H:%M:%SZ"),
+            "url": identity.urls.view_short.full(),
+        }
+        if identity.name:
+            response["name"] = identity.name
+        if identity.summary:
+            response["summary"] = identity.summary
+        return JsonResponse(canonicalise(response, include_security=True))
+
+
+@method_decorator(csrf_exempt, name="dispatch")
+class Inbox(View):
+    """
+    AP Inbox endpoint
+    """
+
+    def post(self, request, handle):
+        # Load the LD
+        document = canonicalise(json.loads(request.body), include_security=True)
+        # Find the Identity by the actor on the incoming item
+        # This ensures that the signature used for the headers matches the actor
+        # described in the payload.
+        identity = Identity.by_actor_uri(document["actor"], create=True)
+        if not identity.public_key:
+            # See if we can fetch it right now
+            async_to_sync(identity.fetch_actor)()
+        if not identity.public_key:
+            print("Cannot get actor")
+            return HttpResponseBadRequest("Cannot retrieve actor")
+        # If there's a "signature" payload, verify against that
+        if "signature" in document:
+            try:
+                LDSignature.verify_signature(document, identity.public_key)
+            except VerificationFormatError as e:
+                print("Bad LD signature format:", e.args[0])
+                return HttpResponseBadRequest(e.args[0])
+            except VerificationError:
+                print("Bad LD signature")
+                return HttpResponseUnauthorized("Bad signature")
+        # Otherwise, verify against the header (assuming it's the same actor)
+        else:
+            try:
+                HttpSignature.verify_request(
+                    request,
+                    identity.public_key,
+                )
+            except VerificationFormatError as e:
+                print("Bad HTTP signature format:", e.args[0])
+                return HttpResponseBadRequest(e.args[0])
+            except VerificationError:
+                print("Bad HTTP signature")
+                return HttpResponseUnauthorized("Bad signature")
+        # Hand off the item to be processed by the queue
+        InboxMessage.objects.create(message=document)
+        return HttpResponse(status=202)
-- 
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