P3-1-T2/T4/T5. Extend createShareLinkSchema with an optional, bounded
documentIds set; validate each id as the caller's own live document and create
the membership rows in the same transaction (frozen write-once). Summary DTOs
gain documentCount (never ids, never bytes).
Add the public share-scoped serve route /c/<token>/d/<id>: token-resolved
(never requireAuth), passphrase-gated via the token-scoped unlock cookie,
revocation/expiry re-checked before any decrypt, confined to the link's frozen
document set (foreign/deleted id → flat 404), fail-closed decrypt, identical
serving-class posture as the owner route (inline Class A / attachment Class B,
nosniff, no-store), EXIF-stripped for raster images on egress, per-link rate
limit.
Carve the serve path out of the proxy's blanket DENY posture with the same
document CSP as the owner route (default-src 'none'; frame-ancestors 'self'),
anchored to exactly two dynamic segments so no lookalike over-matches.
The blanket X-Frame-Options: DENY + frame-ancestors 'none' refused the
detail preview's same-origin <iframe>, and the middleware page CSP
clobbered whatever the serve route set — the inline PDF preview rendered
as a permanent skeleton. Carve out exactly the /original path:
SAMEORIGIN framing, frame-ancestors 'self', and a document CSP of
default-src 'none'. Deliberately NO sandbox directive and no sandbox
attribute on the preview iframe — Chromium force-downloads PDFs in
sandboxed documents instead of rendering them (verified against a real
Chromium channel; headless test builds ship no PDF viewer at all). The
load-bearing boundaries for user-uploaded bytes are unchanged:
magic-byte classification at upload, true Content-Type + nosniff at
serve, HTML/SVG denied entirely, attachment-only posture for every
non-passive format. Tests pin the carve-out and that every neighbouring
path keeps the DENY posture.
Plan-Task: W2-T3 (preview integration)
Marc-André Bombeck