feat(config): discover deep symlinks dynamically when accessing previews

py/config.py

@@ -766,7 +766,23 @@ class Config:
         return f'/api/lm/previews?path={encoded_path}'
 
     def is_preview_path_allowed(self, preview_path: str) -> bool:
-        """Return ``True`` if ``preview_path`` is within an allowed directory."""
+        """Return ``True`` if ``preview_path`` is within an allowed directory.
+        
+        If the path is initially rejected, attempts to discover deep symlinks
+        that were not scanned during initialization. If a symlink is found,
+        updates the in-memory path mappings and retries the check.
+        """
+
+        if self._is_path_in_allowed_roots(preview_path):
+            return True
+
+        if self._try_discover_deep_symlink(preview_path):
+            return self._is_path_in_allowed_roots(preview_path)
+
+        return False
+
+    def _is_path_in_allowed_roots(self, preview_path: str) -> bool:
+        """Check if preview_path is within allowed preview roots without modification."""
 
         if not preview_path:
             return False
@@ -776,30 +792,73 @@ class Config:
         except Exception:
             return False
 
-        # Use os.path.normcase for case-insensitive comparison on Windows.
-        # On Windows, Path.relative_to() is case-sensitive for drive letters,
-        # causing paths like 'a:/folder' to not match 'A:/folder'.
         candidate_str = os.path.normcase(str(candidate))
         for root in self._preview_root_paths:
             root_str = os.path.normcase(str(root))
-            # Check if candidate is equal to or under the root directory
             if candidate_str == root_str or candidate_str.startswith(root_str + os.sep):
                 return True
 
-        if self._preview_root_paths:
         logger.debug(
-                "Preview path rejected: %s (candidate=%s, num_roots=%d, first_root=%s)",
+            "Path not in allowed roots: %s (candidate=%s, num_roots=%d)",
             preview_path,
             candidate_str,
             len(self._preview_root_paths),
-                os.path.normcase(str(next(iter(self._preview_root_paths)))),
         )
-        else:
+
+        return False
+
+    def _try_discover_deep_symlink(self, preview_path: str) -> bool:
+        """Attempt to discover a deep symlink that contains the preview_path.
+
+        Walks up from the preview path to the root directories, checking each
+        parent directory for symlinks. If a symlink is found, updates the
+        in-memory path mappings and preview roots.
+
+        Only updates in-memory state (self._path_mappings and self._preview_root_paths),
+        does not modify the persistent cache file.
+
+        Returns:
+            True if a symlink was discovered and mappings updated, False otherwise.
+        """
+        if not preview_path:
+            return False
+
+        try:
+            candidate = Path(preview_path).expanduser()
+        except Exception:
+            return False
+
+        current = candidate
+        while True:
+            try:
+                if self._is_link(str(current)):
+                    try:
+                        target = os.path.realpath(str(current))
+                        normalized_target = self._normalize_path(target)
+                        normalized_link = self._normalize_path(str(current))
+
+                        self._path_mappings[normalized_target] = normalized_link
+                        self._preview_root_paths.update(self._expand_preview_root(normalized_target))
+                        self._preview_root_paths.update(self._expand_preview_root(normalized_link))
+
                         logger.debug(
-                "Preview path rejected (no roots configured): %s",
+                            "Discovered deep symlink: %s -> %s (preview path: %s)",
-                preview_path,
+                            normalized_link,
+                            normalized_target,
+                            preview_path
                         )
 
+                        return True
+                    except OSError:
+                        pass
+            except OSError:
+                pass
+
+            parent = current.parent
+            if parent == current:
+                break
+            current = parent
+
         return False
 
     def apply_library_settings(self, library_config: Mapping[str, object]) -> None:

py/routes/handlers/preview_handlers.py

@@ -33,6 +33,10 @@ class PreviewHandler:
             raise web.HTTPBadRequest(text="Invalid preview path encoding") from exc
 
         normalized = decoded_path.replace("\\", "/")
+
+        if not self._config.is_preview_path_allowed(normalized):
+            raise web.HTTPForbidden(text="Preview path is not within an allowed directory")
+
         candidate = Path(normalized)
         try:
             resolved = candidate.expanduser().resolve(strict=False)
@@ -40,12 +44,8 @@ class PreviewHandler:
             logger.debug("Failed to resolve preview path %s: %s", normalized, exc)
             raise web.HTTPBadRequest(text="Unable to resolve preview path") from exc
 
-        resolved_str = str(resolved)
-        if not self._config.is_preview_path_allowed(resolved_str):
-            raise web.HTTPForbidden(text="Preview path is not within an allowed directory")
-
         if not resolved.is_file():
-            logger.debug("Preview file not found at %s", resolved_str)
+            logger.debug("Preview file not found at %s", str(resolved))
             raise web.HTTPNotFound(text="Preview file not found")
 
         # aiohttp's FileResponse handles range requests and content headers for us.

tests/config/test_symlink_cache.py

@@ -298,6 +298,134 @@ def test_deep_symlink_not_scanned(monkeypatch: pytest.MonkeyPatch, tmp_path):
     assert normalized_external not in cfg._path_mappings
 
 
+def test_deep_symlink_discovered_on_preview_access(monkeypatch: pytest.MonkeyPatch, tmp_path):
+    """Deep symlinks are discovered dynamically when preview is accessed."""
+    loras_dir, settings_dir = _setup_paths(monkeypatch, tmp_path)
+
+    # Create nested structure with deep symlink at second level
+    subdir = loras_dir / "anime"
+    subdir.mkdir()
+    external_dir = tmp_path / "external"
+    external_dir.mkdir()
+    deep_symlink = subdir / "styles"
+    deep_symlink.symlink_to(external_dir, target_is_directory=True)
+
+    # Create preview file under deep symlink
+    preview_file = deep_symlink / "model.preview.jpeg"
+    preview_file.write_bytes(b"preview")
+
+    # Config should not initially detect deep symlinks
+    cfg = config_module.Config()
+    normalized_external = _normalize(str(external_dir))
+    normalized_deep_link = _normalize(str(deep_symlink))
+    assert normalized_external not in cfg._path_mappings
+
+    # First preview access triggers symlink discovery automatically and returns True
+    is_allowed = cfg.is_preview_path_allowed(str(preview_file))
+
+    # After discovery, preview should be allowed
+    assert is_allowed
+    assert normalized_external in cfg._path_mappings
+    assert cfg._path_mappings[normalized_external] == normalized_deep_link
+
+    # Verify preview path is now allowed without triggering discovery again
+    assert cfg.is_preview_path_allowed(str(preview_file))
+
+
+def test_deep_symlink_at_third_level(monkeypatch: pytest.MonkeyPatch, tmp_path):
+    """Deep symlinks at third level are also discovered dynamically."""
+    loras_dir, settings_dir = _setup_paths(monkeypatch, tmp_path)
+
+    # Create nested structure with deep symlink at third level
+    level1 = loras_dir / "category"
+    level1.mkdir()
+    level2 = level1 / "subcategory"
+    level2.mkdir()
+    external_dir = tmp_path / "external_deep"
+    external_dir.mkdir()
+    deep_symlink = level2 / "deep"
+    deep_symlink.symlink_to(external_dir, target_is_directory=True)
+
+    # Create preview file under deep symlink
+    preview_file = deep_symlink / "preview.webp"
+    preview_file.write_bytes(b"test")
+
+    cfg = config_module.Config()
+
+    # First preview access triggers symlink discovery at third level
+    is_allowed = cfg.is_preview_path_allowed(str(preview_file))
+
+    assert is_allowed
+    normalized_external = _normalize(str(external_dir))
+    normalized_deep_link = _normalize(str(deep_symlink))
+    assert normalized_external in cfg._path_mappings
+    assert cfg._path_mappings[normalized_external] == normalized_deep_link
+
+
+def test_deep_symlink_points_outside_roots(monkeypatch: pytest.MonkeyPatch, tmp_path):
+    """Deep symlinks can point to locations outside configured roots."""
+    loras_dir, settings_dir = _setup_paths(monkeypatch, tmp_path)
+
+    # Create nested structure with deep symlink pointing outside roots
+    subdir = loras_dir / "shared"
+    subdir.mkdir()
+    outside_root = tmp_path / "storage"
+    outside_root.mkdir()
+    deep_symlink = subdir / "models"
+    deep_symlink.symlink_to(outside_root, target_is_directory=True)
+
+    # Create preview file under deep symlink (outside original roots)
+    preview_file = deep_symlink / "external.png"
+    preview_file.write_bytes(b"external")
+
+    cfg = config_module.Config()
+
+    # Preview access triggers symlink discovery
+    is_allowed = cfg.is_preview_path_allowed(str(preview_file))
+
+    # After discovery, preview should be allowed even though target is outside roots
+    assert is_allowed
+    normalized_outside = _normalize(str(outside_root))
+    assert normalized_outside in cfg._path_mappings
+
+
+def test_normal_path_unaffected_by_discovery(monkeypatch: pytest.MonkeyPatch, tmp_path):
+    """Normal paths (no symlinks) are not affected by symlink discovery logic."""
+    loras_dir, settings_dir = _setup_paths(monkeypatch, tmp_path)
+
+    # Create normal file structure (no symlinks)
+    preview_file = loras_dir / "normal.preview.jpeg"
+    preview_file.write_bytes(b"normal")
+
+    cfg = config_module.Config()
+
+    # Normal paths work without any discovery
+    assert cfg.is_preview_path_allowed(str(preview_file))
+    assert len(cfg._path_mappings) == 0
+
+
+def test_first_level_symlink_still_works(monkeypatch: pytest.MonkeyPatch, tmp_path):
+    """First-level symlinks continue to work as before."""
+    loras_dir, settings_dir = _setup_paths(monkeypatch, tmp_path)
+
+    # Create first-level symlink
+    external_dir = tmp_path / "first_level_external"
+    external_dir.mkdir()
+    first_symlink = loras_dir / "first_level"
+    first_symlink.symlink_to(external_dir, target_is_directory=True)
+
+    # Create preview file under first-level symlink
+    preview_file = first_symlink / "model.png"
+    preview_file.write_bytes(b"first_level")
+
+    cfg = config_module.Config()
+
+    # First-level symlinks are scanned during initialization
+    normalized_external = _normalize(str(external_dir))
+    assert normalized_external in cfg._path_mappings
+    assert cfg.is_preview_path_allowed(str(preview_file))
+
+
 def test_legacy_symlink_cache_automatic_cleanup(monkeypatch: pytest.MonkeyPatch, tmp_path):
     """Test that legacy symlink cache is automatically cleaned up after migration."""
     settings_dir = tmp_path / "settings"

tests/routes/test_preview_routes.py

@@ -188,3 +188,91 @@ def test_is_preview_path_allowed_rejects_prefix_without_separator(tmp_path):
     # The sibling path should NOT be allowed even though it shares a prefix
     assert not config.is_preview_path_allowed(str(sibling_file)), \
         f"Path in '{sibling_root}' should NOT be allowed when root is '{library_root}'"
+
+
+async def test_preview_handler_serves_from_deep_symlink(tmp_path):
+    """Test that previews under deep symlinks are served correctly."""
+    library_root = tmp_path / "library"
+    library_root.mkdir()
+
+    # Create nested structure with deep symlink at second level
+    subdir = library_root / "anime"
+    subdir.mkdir()
+    external_dir = tmp_path / "external"
+    external_dir.mkdir()
+    deep_symlink = subdir / "styles"
+    deep_symlink.symlink_to(external_dir, target_is_directory=True)
+
+    # Create preview file under deep symlink
+    preview_file = deep_symlink / "model.preview.webp"
+    preview_file.write_bytes(b"preview_content")
+
+    config = Config()
+    config.apply_library_settings(
+        {
+            "folder_paths": {
+                "loras": [str(library_root)],
+                "checkpoints": [],
+                "unet": [],
+                "embeddings": [],
+            }
+        }
+    )
+
+    handler = PreviewHandler(config=config)
+    encoded_path = urllib.parse.quote(str(preview_file), safe="")
+    request = make_mocked_request("GET", f"/api/lm/previews?path={encoded_path}")
+
+    response = await handler.serve_preview(request)
+
+    assert isinstance(response, web.FileResponse)
+    assert response.status == 200
+    assert Path(response._path) == preview_file.resolve()
+
+
+async def test_deep_symlink_discovered_on_first_access(tmp_path):
+    """Test that deep symlinks are discovered on first preview access."""
+    library_root = tmp_path / "library"
+    library_root.mkdir()
+
+    # Create nested structure with deep symlink at second level
+    subdir = library_root / "category"
+    subdir.mkdir()
+    external_dir = tmp_path / "storage"
+    external_dir.mkdir()
+    deep_symlink = subdir / "models"
+    deep_symlink.symlink_to(external_dir, target_is_directory=True)
+
+    # Create preview file under deep symlink
+    preview_file = deep_symlink / "test.png"
+    preview_file.write_bytes(b"test_image")
+
+    config = Config()
+    config.apply_library_settings(
+        {
+            "folder_paths": {
+                "loras": [str(library_root)],
+                "checkpoints": [],
+                "unet": [],
+                "embeddings": [],
+            }
+        }
+    )
+
+    # Deep symlink should not be in mappings initially
+    normalized_external = os.path.normpath(str(external_dir)).replace(os.sep, '/')
+    assert normalized_external not in config._path_mappings
+
+    handler = PreviewHandler(config=config)
+    encoded_path = urllib.parse.quote(str(preview_file), safe="")
+    request = make_mocked_request("GET", f"/api/lm/previews?path={encoded_path}")
+
+    # First access should trigger symlink discovery and serve the preview
+    response = await handler.serve_preview(request)
+
+    assert isinstance(response, web.FileResponse)
+    assert response.status == 200
+    assert Path(response._path) == preview_file.resolve()
+
+    # Deep symlink should now be in mappings
+    assert normalized_external in config._path_mappings