fix: contain source verification file reads

src/vouch/verify.py

@@ -9,8 +9,6 @@
 from __future__ import annotations
 
 from dataclasses import dataclass
-from pathlib import Path
-
 from . import audit
 from .models import Source
 from .storage import ArtifactNotFoundError, KBStore, sha256_hex
@@ -42,18 +40,15 @@ def verify_source(store: KBStore, source: Source) -> VerificationResult:
     external_status = "n/a"
     note: str | None = None
     if source.type.value == "file":
-        ext = Path(source.locator)
-        if ext.is_file():
-            try:
-                external_status = (
-                    "match" if sha256_hex(ext.read_bytes()) == source.id else "drift"
-                )
-            except OSError as e:
-                external_status = "missing"
-                note = f"unreadable: {e}"
-        else:
+        try:
+            _resolved, external_body = store.read_under_root(source.locator)
+        except (OSError, ValueError) as e:
             external_status = "missing"
-            note = "external file path no longer exists"
+            note = f"unreadable: {e}"
+        else:
+            external_status = (
+                "match" if sha256_hex(external_body) == source.id else "drift"
+            )
 
     return VerificationResult(
         source=source, stored_ok=stored_ok,

tests/test_verify.py

@@ -30,6 +30,24 @@ def test_verify_detects_external_drift(store: KBStore, tmp_path: Path) -> None:
     assert target.external_status == "drift"
 
 
+def test_verify_refuses_off_root_file_locator(store: KBStore, tmp_path: Path) -> None:
+    outside = tmp_path.parent / f"{tmp_path.name}-outside.txt"
+    outside.write_bytes(b"secret")
+    src = store.put_source(
+        b"placeholder",
+        title="outside",
+        locator=str(outside),
+        source_type="file",
+    )
+
+    result = verify.verify_source(store, src)
+
+    assert result.stored_ok is True
+    assert result.external_status == "missing"
+    assert result.note is not None
+    assert "unreadable" in result.note
+
+
 def test_verify_handles_missing_stored_content(store: KBStore, tmp_path: Path) -> None:
     # Regression for #30: verify_source caught FileNotFoundError, but
     # store.read_source_content() raises ArtifactNotFoundError (a KeyError