feat(worker): dispatch verified backends and preserve request-level failures

scripts/backend-service.py

@@ -0,0 +1,106 @@
+#!/usr/bin/env python3
+"""Offline status emitter / explicit installer handoff for the native model chooser.
+
+Status is percent-encoded tab-separated records to keep the C++ UI free of a
+second manifest/JSON/hash implementation. Installer execution is opt-in ONLY.
+"""
+import argparse
+import hashlib
+import os
+import re
+import stat
+from pathlib import Path
+import sys
+from urllib.parse import quote
+
+sys.path.insert(0, str(Path(__file__).resolve().parents[1] / "python"))
+from frameyap.model_files import load_backends, check_model
+
+
+def emit(*fields):
+    print("\t".join(quote(str(field), safe="") for field in fields), flush=True)
+
+
+_DIGEST = re.compile(r"[0-9a-f]{64}\Z", re.ASCII)
+
+
+def manifest_sha(manifest_dir, ident):
+    """Hash bounded raw ID.json bytes, never a reconstructed manifest."""
+    path = manifest_dir / (ident + ".json")
+    fd = os.open(path, os.O_RDONLY | os.O_NOFOLLOW | os.O_NONBLOCK)
+    with os.fdopen(fd, "rb") as stream:
+        before = os.fstat(stream.fileno())
+        if not stat.S_ISREG(before.st_mode) or before.st_size > 65536:
+            raise ValueError("unsafe backend manifest")
+        raw = stream.read(65537)
+        after = os.fstat(stream.fileno())
+        if len(raw) > 65536 or (before.st_size, before.st_mtime_ns, before.st_ctime_ns) != (
+                after.st_size, after.st_mtime_ns, after.st_ctime_ns):
+            raise ValueError("backend manifest changed")
+        return hashlib.sha256(raw).hexdigest()
+
+
+def main(argv=None):
+    parser = argparse.ArgumentParser(description=__doc__)
+    operation = parser.add_mutually_exclusive_group(required=True)
+    operation.add_argument("--status", action="store_true")
+    operation.add_argument("--install", action="store_true")
+    parser.add_argument("--manifest-dir", type=Path, required=True)
+    parser.add_argument("--model-store", type=Path, required=True)
+    parser.add_argument("--backend")
+    parser.add_argument("--installer", type=Path)
+    parser.add_argument("--legacy-model", type=Path)
+    parser.add_argument("--expected-manifest-sha256")
+    args = parser.parse_args(argv)
+    if not args.model_store.is_absolute() or not args.manifest_dir.is_absolute():
+        parser.error("paths must be absolute")
+    if args.status:
+        if args.expected_manifest_sha256:
+            parser.error("expected manifest applies only to install")
+        try:
+            # Bracket parsing and model checks with the same raw-byte snapshots.
+            # Never emit a consent record for metadata changed during status.
+            before = {p.stem: manifest_sha(args.manifest_dir, p.stem)
+                      for p in args.manifest_dir.iterdir() if p.suffix == ".json"}
+            records = []
+            for ident, backend in load_backends(args.manifest_dir).items():
+                path = args.model_store / ident
+                status = check_model(backend, path)
+                if ident == "redux" and args.legacy_model and status["state"] == "not_installed":
+                    legacy = check_model(backend, args.legacy_model)
+                    if legacy["state"] == "installed_verified":
+                        status, path = legacy, args.legacy_model
+                records.append(("ST", ident, backend.display_name, status["state"],
+                     status["reason"] or "", backend.total_bytes, backend.source,
+                     backend.license_id, backend.license_text, backend.attribution, path, before[ident]))
+            if before != {p.stem: manifest_sha(args.manifest_dir, p.stem)
+                          for p in args.manifest_dir.iterdir() if p.suffix == ".json"}:
+                raise ValueError("backend metadata changed during status")
+            for record in records:
+                emit(*record)
+            emit("DONE")
+            return 0
+        except (ValueError, OSError) as error:
+            emit("ERROR", type(error).__name__)
+            return 1
+    # No implicit installation: requires explicit --install AND backend and caller
+    # consent. The exec makes the installer the owned child (no hidden grandchild).
+    if (not args.backend or not args.installer or not args.expected_manifest_sha256 or
+            not _DIGEST.fullmatch(args.expected_manifest_sha256)):
+        parser.error("backend, installer and 64-character consent fingerprint required")
+    try:
+        backends = load_backends(args.manifest_dir)
+        if args.backend not in backends or manifest_sha(args.manifest_dir, args.backend) != args.expected_manifest_sha256:
+            parser.error("selected backend manifest changed since consent")
+    except (OSError, ValueError) as error:
+        parser.error(f"selected backend manifest unavailable: {type(error).__name__}")
+    if not args.installer.is_file() or args.installer.is_symlink():
+        parser.error("installer missing or unsafe")
+    dest = args.model_store / args.backend
+    os.execv("/bin/sh", ["sh", str(args.installer), "--install-model", "--backend", args.backend,
+                          "--model-dir", str(dest), "--expected-manifest-sha256",
+                          args.expected_manifest_sha256, "--yes", "--json"])
+
+
+if __name__ == "__main__":
+    sys.exit(main())