Implementation:Trailofbits Fickling UnsafeFileError

Knowledge Sources	Fickling
Domains	Security, Error_Handling, Deserialization
Last Updated	2026-02-14 14:00 GMT

Overview

Concrete exception class for reporting blocked pickle deserialization attempts provided by the Fickling library.

Description

UnsafeFileError is a custom exception raised by FicklingMLUnpickler.find_class() when a pickle file attempts to import a module or name not in the ML allowlist. It carries the file path and a description of the unsafe import as structured attributes.

Usage

Catch this exception when loading ML models under Fickling protection to handle security-blocked files gracefully. The .filepath and .info attributes provide details for logging or user notification.

Code Reference

Source Location

• Repository: fickling
• File: fickling/exception.py
• Lines: L1-8

Signature

class UnsafeFileError(Exception):
    def __init__(self, filepath: str, info: str):
        """
        Args:
            filepath: Path to the file that triggered the error.
            info: Description of the unsafe import detected.
        """

    def __str__(self) -> str:
        """Returns 'Safety results for {filepath} : {info}'"""

Import

from fickling.exception import UnsafeFileError

I/O Contract

Inputs

Name	Type	Required	Description
filepath	str	Yes	Path to the file that triggered the error
info	str	Yes	Description of the unsafe import detected

Outputs

Name	Type	Description
.filepath	str	The file path attribute
.info	str	The info string attribute
str(error)	str	"Safety results for {filepath} : {info}"

Usage Examples

Catching Blocked Imports

from fickling.exception import UnsafeFileError
from fickling.hook import activate_safe_ml_environment
import pickle

activate_safe_ml_environment()

try:
    with open("untrusted_model.pkl", "rb") as f:
        model = pickle.load(f)
except UnsafeFileError as e:
    print(f"Blocked: {e.filepath}")
    print(f"Reason: {e.info}")
    # Log, alert, or quarantine the file

Related Pages

Implements Principle

• Principle:Trailofbits_Fickling_Unsafe_Deserialization_Error_Handling