Save

The pypickle module serializes objects so they can be saved to a file, and loaded in a program again later on. There are many types that can be saved, such as dictionaries, DataFrames, lists, etc. Saving can be performed using pypickle.pypickle.save():

import pypickle
filepath = 'test.pkl'

# Some data in a list
data = [1,2,3,4,5]

# Save
status = pypickle.save(filepath, data)

Security Mechanisms (save)

There are various key security mechanisms implemented in the save() function to mitigate risks associated with saving pickle files, especially when allowing file writes outside predefined safe directories. Before saving, the function performs several security checks:

  • Ensures the filepath is located in user or temporary directories, unless overridden.

  • Blocks writes to critical system paths.

  • Accepts only known-safe extensions (.pkl, .pickle, .pklz, .pbz2).

  • Prevents directory traversal exploits like ../../etc/passwd.

The table below outlines how explicit user consent, robust path validation, prevention of path traversal exploits, and audit logging work together to protect the system from unauthorized or accidental overwrites.

Mechanism

Purpose

Internal (cwd, tempdir)

Temp directories are permitted

Home directory

Home directory is permitted

allow_external=True

Explicit user opt-in to save outside safe directories

Critical path checks

Prevents saving in system or protected paths

Extension validation

Blocks non-pickle extensions (e.g., .exe, .bat)

Path traversal detection

Detects and blocks path traversal attempts

Audit logs

Logs warnings and overrides for traceability

 
import pypickle
import tempfile
import os

# Safe save
filepath = os.path.join(tempfile.gettempdir(), "test.pkl")
data = [1, 2, 3, 4, 5]
status = pypickle.save(filepath, data)

# Allow external save
filepath = "D:/myfolder/model.pkl"
status = pypickle.save(filepath, data, allow_external=True)

# Save with overwrite
status = pypickle.save(filepath, data, allow_external=True, overwrite=True)

# Unsafe extension (will be blocked)
filepath = "C:/temp/script.bat"
status = pypickle.save(filepath, data)

Critical System Paths

The following directories are considered critical system paths and are blocked from pickle saving to prevent security risks such as overwriting system files, tampering with user configurations, or compromising the operating system.

Path

Description

UNIX

/bin, /boot, /dev, /etc, /lib, /lib64

Core Unix/Linux system directories

/proc, /root, /sbin, /sys, /usr, /var

Additional system-critical paths on Unix/Linux

~/.ssh

Contains SSH private keys and credentials

~/.gnupg

Contains GPG encryption keys and configuration

~/.config

User configuration files

~/.local/share

User application data and caches

MACOS

/System, /Library, /Network

macOS system directories

/private

macOS directory for system-level files (e.g., /etc, /var)

/Volumes

macOS mounted volumes

/Applications

macOS applications

/usr/local/bin

macOS Homebrew and CLI tool location

WINDOWS

C:Windows, C:WindowsSystem32

Core Windows system files

C:Program Files, C:Program Files (x86)

Installed Windows applications

C:ProgramData, C:Recovery

Windows system and recovery data

%APPDATA%

Windows per-user application data (e.g., config, cache)

%LOCALAPPDATA%

Windows local application data

 
import pypickle
import os

# Check for critical path
status = pypickle.is_critical_path(r'/tmp')
pypickle.is_critical_path("C:\\Users\\User\\AppData\\Local\\Temp\\myfile.pkl")
False

pypickle.is_critical_path("C:\\Windows\\System32\\config.sys")
True

# Get all critical paths
crit_paths = pypickle.get_critical_paths()
print(crit_paths)

 # ['/bin',
 #  '/boot',
 #  '/dev',
 #  '/etc',
 #  '/lib',
 #  '/lib64',
 #  '/proc',
 #  '/root',
 #  '/sbin',
 #  '/sys',
 #  '/usr',
 #  '/var',
 #  'C:\\Users\\username/.ssh',
 #  'C:\\Users\\username/.gnupg',
 #  'C:\\Users\\username/.config',
 #  'C:\\Users\\username/.local/share',
 #  '/System',
 #  '/Library',
 #  '/Network',
 #  '/private',
 #  '/Volumes',
 #  '/Applications',
 #  '/usr/local/bin',
 #  'C:\\Windows',
 #  'C:\\Windows\\System32',
 #  'C:\\Program Files',
 #  'C:\\Program Files (x86)',
 #  'C:\\ProgramData',
 #  'C:\\Recovery',
 #  'C:\\Users\\username\\AppData\\Roaming',
 #  'C:\\Users\\username\\AppData\\Local']

Note

Attempts to save pickle files into these directories will be blocked, unless explicitly overridden (not recommended).

import pypickle
import tempfile
import os

# Safe save
filepath = os.path.join(tempfile.gettempdir(), "test.pkl")
data = [1, 2, 3, 4, 5]
status = pypickle.save(filepath, data)

# Critical system path (will be blocked)
filepath = "/etc/"
status = pypickle.save(filepath, data, overwrite=True)
# [pypickle.pypickle] [WARNING] [BLOCKED]: Extention must be of type ['.pkl', '.pickle', '.pklz', '.pbz2']: [/etc/] is not allowed.

# Critical system path (will be blocked)
filepath = "/etc/test.pkl"
status = pypickle.save(filepath, data, overwrite=True)
# [pypickle.pypickle] [WARNING] [BLOCKED]: Filepath: [/etc/test.pkl] is under critical path: [/etc]

# Critical system path (will be blocked)
filepath = "/etc/test.pkl"
status = pypickle.save(filepath, data, overwrite=True, allow_external=True)
# [pypickle.pypickle] [WARNING] [BLOCKED]: Filepath: [/etc/test.pkl] is under critical path: [/etc]