Implementation:Trailofbits Fickling Create Polyglot

Knowledge Sources	Fickling
Domains	Security_Research, Supply_Chain, File_Format
Last Updated	2026-02-14 14:00 GMT

Overview

Concrete tool for creating PyTorch polyglot files from two different format files, provided by the Fickling library.

Description

create_polyglot takes two PyTorch files of different formats, identifies their formats, and combines them into a single polyglot file. It delegates to format-specific creators: create_mar_legacy_pickle_polyglot, create_standard_torchscript_polyglot, or create_mar_legacy_tar_polyglot depending on the format combination. Returns a boolean indicating success.

Usage

Use for security research: creating test polyglots to validate detection capabilities.

Code Reference

Source Location

• Repository: fickling
• File: fickling/polyglot.py
• Lines: L402-437

Signature

def create_polyglot(
    first_file: str,
    second_file: str,
    polyglot_file_name: str | None = None,
    print_results: bool = True
) -> bool:
    """Create a polyglot from two PyTorch files of different formats.

    Args:
        first_file: Path to the first PyTorch file.
        second_file: Path to the second PyTorch file.
        polyglot_file_name: Output filename (auto-determined if None).
        print_results: Print progress to stdout.

    Returns:
        True if a polyglot was successfully created, False otherwise.

    Supported combinations:
        - MAR + PyTorch v0.1.10
        - PyTorch v1.3 + TorchScript v1.4
        - MAR + PyTorch v0.1.1
    """

Import

from fickling.polyglot import create_polyglot

I/O Contract

Inputs

Name	Type	Required	Description
first_file	str	Yes	Path to the first PyTorch file
second_file	str	Yes	Path to the second PyTorch file (different format)
polyglot_file_name	str or None	No	Output filename (auto-determined if None)
print_results	bool	No	Print progress (default: True)

Outputs

Name	Type	Description
(return)	bool	True if polyglot was created successfully
Side effect	File	Polyglot file written to polyglot_file_name

Usage Examples

Create a PyTorch/TorchScript Polyglot

from fickling.polyglot import create_polyglot, identify_pytorch_file_format

# Create polyglot from two different format files
success = create_polyglot(
    first_file="model_v13.pt",
    second_file="model_ts14.pt",
    polyglot_file_name="polyglot_test.pt"
)

if success:
    # Verify polyglot detection
    formats = identify_pytorch_file_format("polyglot_test.pt")
    print(f"Detected formats: {formats}")
    assert len(formats) > 1, "Polyglot should be detected as multiple formats"

Related Pages

Implements Principle

• Principle:Trailofbits_Fickling_Polyglot_File_Creation

Requires Environment

• Environment:Trailofbits_Fickling_PyTorch