fix(core): allow double-dot filenames while still blocking path traversal (#673)

Signed-off-by: Joe P <joe@basicmemory.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jope-bm

src/basic_memory/file_utils.py

@@ -447,6 +447,11 @@ def sanitize_for_filename(text: str, replacement: str = "-") -> str:
     # compress multiple, repeated replacements
     text = re.sub(f"{re.escape(replacement)}+", replacement, text)
 
+    # Strip trailing periods — they cause "hi-everyone..md" double-dot filenames
+    # when ".md" is appended, which triggers path traversal false positives.
+    # Trailing periods are also invalid on Windows filesystems.
+    text = text.strip(".")
+
     return text.strip(replacement)
 
 

src/basic_memory/utils.py

@@ -503,12 +503,23 @@ def valid_project_path_value(path: str):
     if not path:
         return True
 
-    # Check for obvious path traversal patterns first
-    if ".." in path or "~" in path:
+    # Check for tilde (home directory expansion)
+    if "~" in path:
         return False
 
-    # Check for Windows-style path traversal (even on Unix systems)
-    if "\\.." in path or path.startswith("\\"):
+    # Check for ".." as a path segment (path traversal), not as a substring.
+    # Filenames like "hi-everyone..md" are legitimate and must not be blocked.
+    # Also block segments like ".. " and ".. ." because Windows normalizes
+    # trailing dots and spaces away, making them equivalent to "..".
+    segments = path.replace("\\", "/").split("/")
+    if any(
+        seg == ".." or (len(seg) > 2 and seg[:2] == ".." and all(c in ". " for c in seg[2:]))
+        for seg in segments
+    ):
+        return False
+
+    # Check for Windows-style leading backslash
+    if path.startswith("\\"):
         return False
 
     # Block absolute paths (Unix-style starting with / or Windows-style with drive letters)

tests/utils/test_file_utils.py

@@ -198,6 +198,19 @@ def test_sanitize_for_filename_removes_invalid_characters():
         assert char not in sanitized_text
 
 
+def test_sanitize_for_filename_strips_trailing_periods():
+    """Trailing periods cause double-dot filenames like 'hi-everyone..md'.
+
+    This was a production bug where title "Hi everyone." produced file path
+    "hi-everyone..md" which failed path traversal validation.
+    """
+    assert sanitize_for_filename("Hi everyone.") == "Hi everyone"
+    assert sanitize_for_filename("test...") == "test"
+    assert sanitize_for_filename(".hidden") == "hidden"
+    assert sanitize_for_filename("...dots...") == "dots"
+    assert sanitize_for_filename("normal title") == "normal title"
+
+
 @pytest.mark.parametrize(
     "input_directory,expected",
     [

tests/utils/test_validate_project_path.py

@@ -191,6 +191,54 @@ def test_absolute_paths(self, tmp_path):
             assert not result, f"Absolute path '{path}' should be blocked"
 
 
+class TestValidateProjectPathDoubleDotInFilename:
+    """Test that filenames containing '..' as part of the name are allowed."""
+
+    def test_double_dot_in_filename_allowed(self, tmp_path):
+        """Filenames like 'hi-everyone..md' should NOT be blocked.
+
+        This was a production bug: a title ending with a period (e.g. "Hi everyone.")
+        produced a file path like "hi-everyone..md" which the old substring check
+        ('..' in path) incorrectly flagged as path traversal.
+        """
+        project_path = tmp_path / "project"
+        project_path.mkdir()
+
+        safe_paths_with_dots = [
+            "hi-everyone..md",
+            "notes/hi-everyone..md",
+            "version-2..0.md",
+            "file...name.md",
+            "docs/report..final.txt",
+        ]
+
+        for path in safe_paths_with_dots:
+            assert validate_project_path(path, project_path), (
+                f"Path '{path}' with '..' in filename should be allowed"
+            )
+
+    def test_actual_traversal_still_blocked(self, tmp_path):
+        """Ensure '..' as a path segment is still blocked."""
+        project_path = tmp_path / "project"
+        project_path.mkdir()
+
+        attack_paths = [
+            "../file.md",
+            "notes/../../etc/passwd",
+            "foo/../../../bar",
+            "..\\Windows\\System32",
+            # Windows normalizes trailing dots/spaces to ".."
+            ".. /file.md",
+            ".. ./file.md",
+            "notes/.. /etc/passwd",
+        ]
+
+        for path in attack_paths:
+            assert not validate_project_path(path, project_path), (
+                f"Traversal path '{path}' should still be blocked"
+            )
+
+
 class TestValidateProjectPathEdgeCases:
     """Test edge cases and error conditions."""