feat(anhaenge): ATTACH-Zeile im erzeugten ICS

Jeder Anhang wird als ATTACH mit FMTTYPE, SIZE und FILENAME ausgegeben,
als URI statt inline base64 -- bei 10 MB je Datei wuerde sonst bei jeder
Synchronisation der ganze Anhang im ICS-Rumpf mitgeschleppt.

Die absolute URL kommt aus dav_util.public_base, das PUBLIC_BASE_URL und
die Forwarded-Header schon behandelt; ohne Basis-URL wird die Zeile
weggelassen, weil eine relative ATTACH-URL einem externen Client nichts
nuetzt. Abschaltbar ueber ATTACHMENT_PUBLIC_LINKS=0.

Der CalDAV-PUT ist geprueft: ein externer Client, der den Termin
zurueckschreibt, laesst die Anhaenge unberuehrt.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

backend/attachments_store.py

@@ -21,6 +21,7 @@ and forgets the helper.
 
 import io
 import logging
+import os
 import secrets
 import time
 import uuid
@@ -75,6 +76,11 @@ _TEXT_TYPES = {
 # row is committed, and a sweep landing in between would delete a good file.
 SWEEP_GRACE_SECONDS = 3600
 
+# Deployments that would rather lose attachments in external calendar clients
+# than hand out unauthenticated URLs set this to 0: no ATTACH line is emitted
+# and the capability endpoint 404s.
+PUBLIC_LINKS_ENABLED = os.environ.get("ATTACHMENT_PUBLIC_LINKS", "1") != "0"
+
 
 def sniff(raw: bytes, filename: str) -> tuple[str, str]:
     """Determine ``(content_type, extension)`` from the BYTES.
@@ -243,6 +249,23 @@ def counts_for_events(db: Session, event_ids: Iterable[int]) -> dict[int, int]:
     return {event_id: n for event_id, n in rows}
 
 
+def by_event(db: Session, event_ids: Iterable[int]) -> dict[int, list]:
+    """Attachments grouped by event id, in ONE query — for ICS generation."""
+    ids = [i for i in event_ids if i is not None]
+    if not ids:
+        return {}
+    out: dict[int, list] = {}
+    rows = (
+        db.query(models.EventAttachment)
+        .filter(models.EventAttachment.event_id.in_(ids))
+        .order_by(models.EventAttachment.id)
+        .all()
+    )
+    for row in rows:
+        out.setdefault(row.event_id, []).append(row)
+    return out
+
+
 def sweep(db: Session) -> tuple[int, int]:
     """Drop attachments whose event is gone, and files with no row.
 

backend/ical_io.py

@@ -9,9 +9,11 @@ from __future__ import annotations
 
 import logging
 import uuid
+from urllib.parse import quote
 from datetime import date, datetime, timedelta, timezone
 
-from icalendar import Calendar, Event, vCalAddress, vRecur, vText
+from icalendar import Calendar, Event, vCalAddress, vRecur, vText, vUri
+from icalendar.parser import Parameters
 
 logger = logging.getLogger(__name__)
 
@@ -150,8 +152,17 @@ def _parse_iso(s: str) -> datetime:
     return dt
 
 
-def build_ics(calendar, events, *, name_cache: dict | None = None) -> str:
+def build_ics(calendar, events, *, name_cache: dict | None = None,
-    """Build a VCALENDAR string for a local calendar and its events."""
+              attachments_by_event: dict | None = None,
+              base_url: str | None = None) -> str:
+    """Build a VCALENDAR string for a local calendar and its events.
+
+    ``attachments_by_event`` maps LocalEvent.id -> list of EventAttachment. With
+    a ``base_url`` each one becomes an ATTACH property pointing at its
+    capability URL, so external clients (Apple Calendar, Thunderbird) can fetch
+    it — they cannot send a bearer token. Both arguments are optional so every
+    existing caller keeps working and emits no ATTACH at all.
+    """
     cal = Calendar()
     cal.add("prodid", "-//Calendarr//EN")
     cal.add("version", "2.0")
@@ -200,6 +211,20 @@ def build_ics(calendar, events, *, name_cache: dict | None = None) -> str:
             organizer.params["CN"] = vText(organizer_name.replace('"', ""))
             item.add("organizer", organizer)
 
+        # ATTACH: one line per attachment, as a URI rather than inline base64 —
+        # the files are up to 10 MB each and would otherwise be copied into
+        # every ICS body on every sync.
+        for att in (attachments_by_event or {}).get(getattr(ev, "id", None), ()):
+            if not base_url:
+                continue  # a relative ATTACH URL is useless to an external client
+            uri = vUri(f"{base_url}/api/attach/{att.token}/{quote(att.filename)}")
+            uri.params = Parameters({
+                "FMTTYPE": att.content_type,
+                "SIZE": str(att.size_bytes),
+                "FILENAME": att.filename,
+            })
+            item.add("attach", uri, encode=0)
+
         cal.add_component(item)
 
     return cal.to_ical().decode("utf-8")

backend/routers/attachments_router.py

@@ -10,7 +10,6 @@ Two routers live here:
                   send a bearer token. See the README for the tradeoff.
 """
 
-import os
 from urllib.parse import quote
 
 from fastapi import APIRouter, Depends, File, HTTPException, UploadFile
@@ -29,12 +28,6 @@ from database import get_db
 router = APIRouter()
 public_router = APIRouter()
 
-# Deployments that would rather lose attachments in external calendar clients
-# than hand out unauthenticated URLs can set this to 0: the capability endpoint
-# then 404s and no ATTACH line is emitted into any ICS.
-PUBLIC_LINKS_ENABLED = os.environ.get("ATTACHMENT_PUBLIC_LINKS", "1") != "0"
-
-
 def _to_dict(att: models.EventAttachment) -> dict:
     uploader = None
     if att.uploader is not None:
@@ -261,7 +254,7 @@ def public_attachment(token: str, name: str = "", db: Session = Depends(get_db))
 
     Never distinguish "wrong token" from "deleted": both are 404.
     """
-    if not PUBLIC_LINKS_ENABLED:
+    if not attachments_store.PUBLIC_LINKS_ENABLED:
         raise HTTPException(404, "Not found")
     att = (
         db.query(models.EventAttachment)

backend/routers/dav_router.py

@@ -160,8 +160,15 @@ def _name_cache(cal: models.LocalCalendar, db: Session) -> dict:
     return {}
 
 
-def _build_ics(cal: models.LocalCalendar, evs: list[models.LocalEvent], db: Session) -> str:
+def _build_ics(cal: models.LocalCalendar, evs: list[models.LocalEvent], db: Session,
-    return ical_io.build_ics(cal, evs, name_cache=_name_cache(cal, db))
+               base_url: str | None = None) -> str:
+    # Without a base URL (or with public links switched off) no ATTACH is
+    # emitted: a relative attachment URL is useless to an external client.
+    atts = None
+    if base_url and attachments_store.PUBLIC_LINKS_ENABLED:
+        atts = attachments_store.by_event(db, [e.id for e in evs])
+    return ical_io.build_ics(cal, evs, name_cache=_name_cache(cal, db),
+                             attachments_by_event=atts, base_url=base_url)
 
 
 # ── XML builders ──────────────────────────────────────────
@@ -277,7 +284,8 @@ def _handle_propfind(cal: models.LocalCalendar, base: str, resource: str, depth:
     return _multistatus("\n".join(parts))
 
 
-def _handle_report(cal: models.LocalCalendar, base: str, body: bytes, db: Session) -> Response:
+def _handle_report(cal: models.LocalCalendar, base: str, body: bytes, db: Session,
+                   base_url: str | None = None) -> Response:
     report_type = None
     hrefs: list[str] = []
     if body:
@@ -297,17 +305,17 @@ def _handle_report(cal: models.LocalCalendar, base: str, body: bytes, db: Sessio
 
     parts = []
     for ev in evs:
-        ics = _build_ics(cal, [ev], db)
+        ics = _build_ics(cal, [ev], db, base_url)
         parts.append(_event_propstat(base, ev, with_data=True, ics=ics))
     return _multistatus("\n".join(parts) if parts else "")
 
 
 def _handle_get(cal: models.LocalCalendar, resource: str, db: Session,
-                *, head: bool = False) -> Response:
+                *, head: bool = False, base_url: str | None = None) -> Response:
     ev = _find_event(cal, resource, db)
     if not ev:
         return Response(status_code=404)
-    ics = _build_ics(cal, [ev], db)
+    ics = _build_ics(cal, [ev], db, base_url)
     headers = {"ETag": f'"{_etag(ev)}"'}
     return Response(
         content=b"" if head else ics,
@@ -390,13 +398,15 @@ async def _dispatch_collection(request: Request, cal: models.LocalCalendar, base
         depth = request.headers.get("Depth", "0")
         return _handle_propfind(cal, base, resource, depth, db,
                                 principal_href=principal_href, home_href=home_href)
+    # The public origin as clients actually reach us, for ATTACH URLs.
+    base_url = dav_util.public_base(request)
     if method == "REPORT":
-        return _handle_report(cal, base, await request.body(), db)
+        return _handle_report(cal, base, await request.body(), db, base_url)
     if method in ("GET", "HEAD"):
         if not resource:
-            ics = _build_ics(cal, _events(cal, db), db)
+            ics = _build_ics(cal, _events(cal, db), db, base_url)
             return Response(content=ics, media_type="text/calendar; charset=utf-8")
-        return _handle_get(cal, resource, db, head=(method == "HEAD"))
+        return _handle_get(cal, resource, db, head=(method == "HEAD"), base_url=base_url)
     if method == "PUT":
         return _handle_put(cal, resource, await request.body(), db)
     if method == "DELETE":

backend/routers/local_router.py

@@ -772,6 +772,7 @@ async def import_generic(
 @router.get("/calendars/{calendar_id}/export")
 def export_calendar(
     calendar_id: int,
+    request: Request,
     db: Session = Depends(get_db),
     current_user: models.User = Depends(get_current_user),
 ):
@@ -783,7 +784,12 @@ def export_calendar(
     )
     # Resolve creator display names for ORGANIZER.
     name_cache = {u.id: (u.display_name or u.username) for u in db.query(models.User).all()}
-    ics = ical_io.build_ics(cal, events, name_cache=name_cache)
+    base_url = dav_util.public_base(request)
+    atts = None
+    if base_url and attachments_store.PUBLIC_LINKS_ENABLED:
+        atts = attachments_store.by_event(db, [e.id for e in events])
+    ics = ical_io.build_ics(cal, events, name_cache=name_cache,
+                            attachments_by_event=atts, base_url=base_url)
     safe_name = "".join(c for c in cal.name if c.isalnum() or c in (" ", "-", "_")).strip() or "calendar"
     return Response(
         content=ics,

backend/tests/test_attachments.py

@@ -516,3 +516,132 @@ def test_busy_masked_event_reports_no_attachments(client):
     masked = next(e for e in events if e["id"] == ev["id"])
     assert masked["title"] == "Beschäftigt"
     assert masked["attachment_count"] == 0
+
+
+# ── ATTACH in the generated ICS ───────────────────────────
+
+def _publish(client, token, cal_id):
+    """Publish the calendar over CalDAV and return its secret token URL path."""
+    r = client.put(f"/api/local/calendars/{cal_id}", headers=auth(token),
+                   json={"caldav_published": True})
+    assert r.status_code == 200, r.text
+    cals = client.get("/api/local/calendars", headers=auth(token)).json()
+    url = next(c["caldav_url"] for c in cals if c["id"] == cal_id)
+    return "/dav/" + url.rstrip("/").rsplit("/", 1)[-1] + "/"
+
+
+def _attach_props(ics_text):
+    """Re-parse instead of grepping: icalendar folds lines at 75 octets, so a
+    naive substring check would miss a long URL."""
+    from icalendar import Calendar
+
+    cal = Calendar.from_ical(ics_text)
+    out = []
+    for comp in cal.walk("VEVENT"):
+        prop = comp.get("attach")
+        if prop is None:
+            continue
+        for p in (prop if isinstance(prop, list) else [prop]):
+            out.append((str(p), dict(p.params)))
+    return out
+
+
+def test_ics_carries_an_attach_line_per_attachment(client):
+    token = register_admin(client)
+    cal_id = _make_calendar(client, token)
+    ev = _make_event(client, token, cal_id)
+    _upload(client, token, ev["id"], name="Mietvertrag.pdf")
+    _upload(client, token, ev["id"], png_bytes(), "foto.png", "image/png")
+    dav_path = _publish(client, token, cal_id)
+
+    props = _attach_props(client.get(dav_path).text)
+    assert len(props) == 2
+    by_name = {params["FILENAME"]: (uri, params) for uri, params in props}
+    assert set(by_name) == {"Mietvertrag.pdf", "foto.png"}
+
+    uri, params = by_name["Mietvertrag.pdf"]
+    assert params["FMTTYPE"] == "application/pdf"
+    assert int(params["SIZE"]) == len(PDF_BYTES)
+    assert "/api/attach/" in uri and uri.startswith("http")
+
+
+def test_attach_url_from_the_ics_actually_serves_the_file(client):
+    """The whole point: an external client follows the URL with no credentials."""
+    token = register_admin(client)
+    cal_id = _make_calendar(client, token)
+    ev = _make_event(client, token, cal_id)
+    _upload(client, token, ev["id"])
+    dav_path = _publish(client, token, cal_id)
+
+    uri, _ = _attach_props(client.get(dav_path).text)[0]
+    path = uri.split("testserver", 1)[1]
+    r = client.get(path)  # no Authorization header
+    assert r.status_code == 200
+    assert r.content == PDF_BYTES
+
+
+def test_attach_url_honours_public_base_url(client, monkeypatch):
+    """Behind a reverse proxy the app only sees its internal origin."""
+    monkeypatch.setenv("PUBLIC_BASE_URL", "https://cal.example.com")
+    token = register_admin(client)
+    cal_id = _make_calendar(client, token)
+    ev = _make_event(client, token, cal_id)
+    _upload(client, token, ev["id"])
+    dav_path = _publish(client, token, cal_id)
+
+    uri, _ = _attach_props(client.get(dav_path).text)[0]
+    assert uri.startswith("https://cal.example.com/api/attach/")
+
+
+def test_no_attach_when_public_links_are_switched_off(client, monkeypatch):
+    monkeypatch.setattr(attachments_store, "PUBLIC_LINKS_ENABLED", False)
+    token = register_admin(client)
+    cal_id = _make_calendar(client, token)
+    ev = _make_event(client, token, cal_id)
+    _upload(client, token, ev["id"])
+    dav_path = _publish(client, token, cal_id)
+
+    assert _attach_props(client.get(dav_path).text) == []
+
+
+def test_events_without_attachments_get_no_attach(client):
+    token = register_admin(client)
+    cal_id = _make_calendar(client, token)
+    _make_event(client, token, cal_id)
+    dav_path = _publish(client, token, cal_id)
+    assert _attach_props(client.get(dav_path).text) == []
+
+
+def test_upload_changes_the_event_etag(client):
+    """The ICS body changes, so CalDAV clients must be told to re-fetch."""
+    token = register_admin(client)
+    cal_id = _make_calendar(client, token)
+    ev = _make_event(client, token, cal_id)
+    db = SessionLocal()
+    before = db.query(models.LocalEvent).filter(
+        models.LocalEvent.uid == ev["id"]).first().etag
+    db.close()
+
+    _upload(client, token, ev["id"])
+
+    db = SessionLocal()
+    after = db.query(models.LocalEvent).filter(
+        models.LocalEvent.uid == ev["id"]).first().etag
+    db.close()
+    assert after != before
+
+
+def test_caldav_put_leaves_attachments_alone(client):
+    """An external client rewriting the event must not drop its attachments."""
+    token = register_admin(client)
+    cal_id = _make_calendar(client, token)
+    ev = _make_event(client, token, cal_id)
+    _upload(client, token, ev["id"])
+    dav_path = _publish(client, token, cal_id)
+
+    ics = client.get(dav_path).text
+    r = client.put(f"{dav_path}{ev['id']}.ics", content=ics.encode("utf-8"),
+                   headers={"Content-Type": "text/calendar"})
+    assert r.status_code in (201, 204), r.text
+    assert _row_count() == 1
+    assert len(_attach_props(client.get(dav_path).text)) == 1