[mirror] Normalize outgoing JSON-LD for Pixelfed interop

[yashwant86]

Mirror of upstream fedify-dev#721 for benchmark. Do not merge.

---

Summary by MergeMonkey

• Documentation:
  • Updated send.md with JSON-LD normalization configuration details.
  • Added CHANGES.md entry documenting outgoing JSON-LD wire-format fixes.
• What's New:
  • Normalizes outgoing ActivityStreams attachments to arrays for Pixelfed interop.
  • Adds normalizeExistingProofs option to preserve pre-signed activity normalization.
  • Implements preloaded-only JSON-LD context loader for safe verification fallbacks.
• Squashed Bugs:
  • Fixes single-item attachment scalars rejected by Pixelfed's JSON parser.
  • Ensures proof verification accepts both wire-form and normalized JSON-LD.

[bot-mergemonkey]

⚡ Risk Assessment — CRITICAL · ~45 min review

Focus areas: Proof verification fallback logic with preloaded-only loader · normalizeExistingProofs flag propagation through fanout queue · Async test coverage for attachment normalization

Assessment: Modifies proof creation and verification logic, adds conditional normalization affecting signed activity bytes.

Walkthrough

When sending an activity, Fedify now normalizes outgoing JSON-LD to fix interoperability issues: scalar attachments are wrapped in arrays (Pixelfed expects arrays), and public audience URIs are expanded. For pre-signed activities, normalization is skipped by default to preserve proof bytes, but callers can opt in via normalizeExistingProofs. Proof verification accepts both wire-form and normalized forms, using a preloaded-only context loader to prevent attacker-controlled contexts from triggering network fetches.

Changes

Files	Summary
Outgoing JSON-LD Normalization Core packages/fedify/src/compat/outgoing-jsonld.ts, outgoing-jsonld.test.ts, preloaded-context-loader.ts	Adds attachment array normalization and public audience fixes for outgoing activities. Wraps scalar attachments in arrays when semantically safe, with depth-bounded traversal and JSON-LD canonicalization validation. Preloaded-only context loader prevents network fetches on adversarial JSON-LD.
Public Audience Normalization Refactor packages/fedify/src/compat/public-audience.ts	Extracts preloaded-only document loader to shared module for reuse in proof verification and attachment normalization.
Proof Creation & Verification packages/fedify/src/sig/proof.ts, proof.test.ts	Updates createProof() to normalize outgoing JSON-LD before signing. Refactors verifyProofInternal() to use preloaded-only loader for fallback normalization, preventing attacker-controlled context URLs from triggering network fetches. Adds test coverage for attachment normalization in signed objects.
Activity Sending & Fanout packages/fedify/src/federation/middleware.ts, context.ts, queue.ts	Adds normalizeExistingProofs option to sendActivity() and fanout queue. Conditionally applies outgoing JSON-LD normalization based on proof creation state: normalizes unsigned activities and Fedify-created proofs, preserves existing proofs unless explicitly opted in. Propagates flag through fanout pipeline.
Documentation & Configuration docs/manual/send.md CHANGES.md	Documents JSON-LD normalization configuration and wire-format interoperability fixes.

Sequence Diagram

sequenceDiagram
  participant Caller
  participant sendActivity
  participant createProof
  participant normalizeOutgoing
  participant verifyProof
  Caller->>sendActivity: activity, keys, options
  alt has existing proof
    sendActivity->>sendActivity: check normalizeExistingProofs flag
    alt flag true or proof created by Fedify
      sendActivity->>normalizeOutgoing: normalize JSON-LD
    else flag false
      sendActivity->>sendActivity: skip normalization
    end
  else no proof
    sendActivity->>createProof: sign activity
    createProof->>normalizeOutgoing: normalize before signing
    normalizeOutgoing-->>createProof: normalized bytes
    createProof->>createProof: sign normalized form
  end
  sendActivity->>sendActivity: serialize to compact JSON-LD
  sendActivity-->>Caller: send to inbox
  Caller->>verifyProof: received JSON-LD, proof
  verifyProof->>verifyProof: try verify on-wire form
  alt verification fails
    verifyProof->>normalizeOutgoing: normalize with preloaded-only loader
    verifyProof->>verifyProof: try verify normalized form
  end
  verifyProof-->>Caller: verification result

Loading

Dig Deeper With Commands

• /review <file-path> <function-optional>
• /chat <file-path> "<question>"
• /roast <file-path>

Runs only when explicitly triggered.