reverse-engineering-anything/docs/node-sea.md

Node.js single executable applications

REA inventories injected Node.js SEA blobs through inspect-artifact / inspect_artifact and materializes their contents through extract-artifact / extract_artifact. It never runs the application or deserializes V8 snapshots or code cache.

rea inspect-artifact ./application --json
rea inspect-artifact ./application --detail summary --evidence_output evidence.json --json
rea extract-artifact ./application --json

For MCP, open the carrier with open_binary, then call inspect_artifact. Summary delivery retains the complete Evidence: use parent_evidence_id with inspect_analysis_view to request particular inventory paths and fields. Extraction returns a fresh output_root; analyze that extracted directory with analyze_javascript_application. Snapshot-only applications have no recovered main script and receive no JavaScript next probe. Neither does a main script whose logical path lacks a JavaScript source suffix, such as main, because the analyzer selects extracted files by suffix.

Recognition and evidence

The container format is node-sea. REA locates Mach-O sections named __NODE_SEA_BLOB in NODE_SEA or __NODE_SEA, ELF notes owned by NODE_SEA_BLOB, and PE RCDATA resources named NODE_SEA_BLOB. PE resource locations come from the shared PE resource parser. ELF program-header PT_NOTE segments are authoritative, as at runtime; SHT_NOTE sections are read only when no program-header table is readable, because injectors can leave stale section entries. A PE without a NODE_SEA_BLOB resource name is left to native classification. Universal Mach-O carriers with different slice blobs are rejected as ambiguous; identical blobs are inventoried once. Native carrier bytes keep their content hash and native classification while the root occurrence represents the SEA container.

Root format_metadata preserves raw flags, decoded flags, code path, blob location, exec arguments and fuse observations. Main and asset children retain their role and exact declared name in source_path. Safe, noncolliding names become logical paths after the shared NFC path normalization. Names that are unsafe as relative paths, have an exact or file-prefix collision with another entry, or occupy the reserved __node_sea__ namespace receive deterministic logical paths: __node_sea__/main.cjs for the main CommonJS source and __node_sea__/assets/<ordinal> for assets, using their zero-based order in the blob. The original declared name remains in source_path, including an empty asset key. Snapshots and code caches use __node_sea__/snapshot and __node_sea__/code-cache. Extraction materializes the logical paths through the shared path-containment and collision rules and never overwrites existing files.

The fuse scan independently records set, unset, absent, or conflicting. An unset fuse with a present blob is reported as a limitation. These are static sentinel observations, not proof of runtime activation: sentinel-like text in script or asset bytes also participates in the scan.

Supported layout and limits

The decoder follows the 64-bit little-endian layout in Node v24.10.0 node_sea.cc and node_sea.h, including the exec-argument extension byte. Older layouts without that byte, 32-bit length fields, big-endian blobs and future flags are not supported. Carrier byte order is independent of blob byte order.

Malformed magic, truncation, unknown flags/extensions, invalid UTF-8, duplicate raw asset keys and conflicting blob declarations fail closed with named reasons. Zero padding after a complete blob is allowed. The blob read ceiling is 256 MiB; PE carriers also use the shared 512 MiB input, 65,536 directory-entry and 8 MiB resource-metadata ceilings. The decoder admits at most 100,000 assets whose names total at most 8 MiB, and 4,096 exec arguments totaling at most 1 MiB of text. These are fixed resource bounds, not Node format limits, checked before decoding names or creating records; a hit fails as a limit with no runtime override. Asset and argument decoding, padding scans, and inventory construction yield in bounded batches and honor caller cancellation. Asset count and name budgets bound retained metadata independently of stored member body sizes. The PE name probe reads headers from the first 64 KiB of the carrier; a PE whose headers extend beyond that is left to native classification. Snapshot and code-cache bytes remain opaque.

Verification

Synthetic fixtures cover Mach-O, ELF and PE inventory/extraction, malformed blobs, collisions and fuse contradictions. CLI and MCP tests exercise the same artifact provider and advertised schemas. A CLI regression also generates a blob with the pinned local Node version, an absolute main path and an empty asset key, then inventories it inside a synthetic ELF carrier. This verifies the real blob producer, not a real injected executable.

The optional real ELF lane uses Docker's official Node v24.10.0 image and pinned postject to build a fixture, then verifies inventory and extracted script/asset bytes without running the injected application:

npm run verify:node-sea

This requires Docker and network access to fetch the producer image and postject. It creates and removes its own temporary fixture directory. A real macOS Mach-O or Windows PE run is separate coverage; synthetic carriers do not establish real-platform verification. No performance improvement is claimed; whole-task tokens, CPU, memory, and cold/warm timings have not been measured.