fix(history): reject invalid inspection targets (#209)

py/api/images.py

@@ -20,7 +20,13 @@ from PIL import Image, UnidentifiedImageError
 from .prompts import bad_request, parse_page_params, publish_image_paths
 from .prompts import thumbnail_url_for
 from .prompts import safe_error_message as _safe_error
-from .inspection_service import CurrentFileChanged, inspect_current_file
+from .inspection_service import (
+    CurrentFileChanged,
+    IMAGE_EXTENSIONS as _IMAGE_EXTENSIONS,
+    SERVABLE_EXTENSIONS,
+    VIDEO_EXTENSIONS,
+    inspect_current_file,
+)
 
 try:
     from ...utils.parallel import map_parallel
@@ -29,23 +35,8 @@ except ImportError:
     from utils.parallel import map_parallel
     from utils.inspection_response import encode_inspection_response
 
-# Only these file types are ever served by the image routes, regardless of
-# what sits inside an allowed directory (defence in depth for the gallery).
-IMAGE_EXTENSIONS = frozenset(
-    {
-        ".png",
-        ".jpg",
-        ".jpeg",
-        ".webp",
-        ".gif",
-        ".bmp",
-        ".tiff",
-        ".tif",
-        ".mp4",
-        ".webm",
-        ".mov",
-    }
-)
+
+IMAGE_EXTENSIONS = _IMAGE_EXTENSIONS
 
 
 def _public_path(path):
@@ -97,11 +88,7 @@ def _media_access_error(path, allowed_dirs):
 
 # Media types the gallery scans and thumbnails (a superset is never served).
 GALLERY_IMAGE_EXTENSIONS = frozenset({".png", ".jpg", ".jpeg", ".webp", ".gif"})
-VIDEO_EXTENSIONS = frozenset({".mp4", ".webm", ".avi", ".mov", ".mkv", ".m4v", ".wmv"})
 MEDIA_EXTENSIONS = GALLERY_IMAGE_EXTENSIONS | VIDEO_EXTENSIONS
-# What the serve routes hand out: every image type above plus every video type
-# the gallery lists, so a card never points at a 403.
-SERVABLE_EXTENSIONS = IMAGE_EXTENSIONS | VIDEO_EXTENSIONS
 
 # Caps on request-triggered filesystem work.
 MAX_SCAN_DEPTH = 12

py/api/inspection_service.py

@@ -1,5 +1,7 @@
 """One bounded current-file inspection worker shared by physical identities."""
 
+import os
+import stat
 from pathlib import Path
 
 try:
@@ -18,23 +20,56 @@ except ImportError:
     from utils.video_metadata import is_video_path
 
 
+# Only these file types are served or inspected within an authorized directory.
+IMAGE_EXTENSIONS = frozenset(
+    {
+        ".png",
+        ".jpg",
+        ".jpeg",
+        ".webp",
+        ".gif",
+        ".bmp",
+        ".tiff",
+        ".tif",
+        ".mp4",
+        ".webm",
+        ".mov",
+    }
+)
+VIDEO_EXTENSIONS = frozenset({".mp4", ".webm", ".avi", ".mov", ".mkv", ".m4v", ".wmv"})
+SERVABLE_EXTENSIONS = IMAGE_EXTENSIONS | VIDEO_EXTENSIONS
+
+
 class CurrentFileChanged(Exception):
-    """File facts changed across the bounded metadata observation."""
+    """File facts are invalid or changed across the bounded metadata observation."""
+
+
+def _current_file_facts(path: Path) -> os.stat_result:
+    if path.suffix.lower() not in SERVABLE_EXTENSIONS:
+        raise CurrentFileChanged
+    try:
+        observed = path.stat()
+    except (FileNotFoundError, NotADirectoryError, PermissionError):
+        raise CurrentFileChanged from None
+    if (
+        not stat.S_ISREG(observed.st_mode)
+        or not observed.st_mode & 0o444
+        or not os.access(path, os.R_OK)
+    ):
+        raise CurrentFileChanged
+    return observed
 
 
 def inspect_current_file(
     path: Path, *, source_label: str, saved: dict | None, library: dict
 ) -> dict:
-    before = path.stat()
+    before = _current_file_facts(path)
     try:
         inspection = read_inspection_file(path)
     except MetadataReadError:
         inspection = None
-    try:
-        after = path.stat()
-    except FileNotFoundError:
-        raise CurrentFileChanged from None
-    fields = ("st_dev", "st_ino", "st_size", "st_mtime_ns", "st_ctime_ns")
+    after = _current_file_facts(path)
+    fields = ("st_dev", "st_ino", "st_mode", "st_size", "st_mtime_ns", "st_ctime_ns")
     if any(getattr(before, key) != getattr(after, key) for key in fields):
         raise CurrentFileChanged
     if inspection is None: