README.md

@@ -136,8 +136,9 @@ provisional cache policy or a pointer to a missing immutable target.
 
 Artifact input directories must be pairwise disjoint after filesystem
 resolution. Publication stops before build or upload if one contains another or
-escapes the repository, preventing protected input from entering a public
-artifact. Split storage endpoints are pinned to Garage, and each website
+escapes the repository. Descendant symlinks are also rejected, preventing
+protected input from entering a public artifact through dereference. Split
+storage endpoints are pinned to Garage, and each website
 authority is derived from its bucket; a site cannot expose an arbitrary backend.
 
 Each split route gets a bucket-specific `<bucket>.web.sjc001.fritzlab.net`

scripts/utils.py

@@ -427,6 +427,8 @@ def normalize_site_config(raw, site_name):
 
 def validate_artifact_inputs(site_dir, cfg):
     """Reject source containment before a public or protected build starts."""
+    if cfg["compatibility"]:
+        return
     root = Path(site_dir).resolve()
     sources = []
     for artifact in cfg["artifacts"]:
@@ -435,6 +437,13 @@ def validate_artifact_inputs(site_dir, cfg):
             raise ConfigError(
                 f"artifact {artifact['name']} content_dir resolves outside the repository"
             )
+        if source.exists():
+            symlink = next((path for path in source.rglob("*") if path.is_symlink()), None)
+            if symlink is not None:
+                raise ConfigError(
+                    f"artifact {artifact['name']} build input contains symlink: "
+                    f"{symlink.relative_to(root)}"
+                )
         sources.append((artifact["name"], source))
     for index, (name, source) in enumerate(sources):
         for other_name, other_source in sources[index + 1:]:

tests/test_contract.py

@@ -219,6 +219,17 @@ class ConfigContractTests(unittest.TestCase):
             with self.assertRaisesRegex(ConfigError, "build inputs overlap after resolution"):
                 validate_artifact_inputs(root, cfg)
 
+    def test_descendant_symlink_cannot_cross_artifact_boundary(self):
+        cfg = normalize_site_config(self.raw, "baseline.fritzlab.net")
+        with tempfile.TemporaryDirectory() as tmp:
+            root = Path(tmp)
+            (root / "dist").mkdir()
+            (root / "portal" / "build").mkdir(parents=True)
+            (root / "portal" / "build" / "private.txt").write_text("private")
+            (root / "dist" / "portal-link").symlink_to(root / "portal" / "build")
+            with self.assertRaisesRegex(ConfigError, "build input contains symlink"):
+                validate_artifact_inputs(root, cfg)
+
 
 class GenerationTests(unittest.TestCase):
     def render(self, raw):