Manual Secure Coding in Python #

Python is a powerful programming language commonly used for developing various applications. When it comes to coding in Python, ensuring security should be a top priority. In this article, we will explore some manual techniques to write secure Python code, followed by an example of using Google Apps Script for secure coding.

Use Strong Input Validation #

One of the most crucial aspects of secure coding is input validation. Always validate user input and be thorough in checking for any potential vulnerabilities or malicious inputs. Use robust input validation techniques such as regular expressions, whitelisting, or blacklisting to ensure that only valid and safe input is processed.

import re

def validate_input(input):
# Using regular expressions to validate input
if re.match(r'^[A-Za-z0-9_]+$', input):
return True
else:
return False

Implement Proper Authentication and Authorization #

When dealing with user authentication and authorization, it is important to implement secure practices. Avoid storing sensitive information such as passwords in plain text. Instead, use cryptographic hashing algorithms like bcrypt or hashlib to securely store and validate passwords.

import bcrypt

def hash_password(password):
salt = bcrypt.gensalt()
hashed_password = bcrypt.hashpw(password.encode('utf-8'), salt)
return hashed_password

def validate_password(password, hashed_password):
return bcrypt.checkpw(password.encode('utf-8'), hashed_password)

Ensure that access control mechanisms are in place to restrict unauthorized access to sensitive resources or functionalities. Implement proper user roles and permissions to grant access only to authorized users.

Protect Against Injection Attacks #

Injection attacks, such as SQL injection and command injection, can be devastating for any application. Protect your code by using parameterized queries or prepared statements when interacting with databases to prevent SQL injection attacks.

import sqlite3

def execute_query(query, params):
conn = sqlite3.connect('database.db')
cursor = conn.cursor()
cursor.execute(query, params)
result = cursor.fetchall()
conn.commit()
cursor.close()
conn.close()
return result

Avoid using string concatenation or formatting to form SQL queries, as it can leave your code vulnerable to attacks.

Sanitize Output #

Ensure that any output sent from your application is properly sanitized and encoded to prevent cross-site scripting (XSS) attacks. Use appropriate encoding functions like HTML.escape() or cgi.escape() to sanitize user-generated content before displaying it.

import html

def sanitize_input(input):
return html.escape(input)

Handle Exceptions Properly #

Exception handling plays a vital role in secure coding. Handle exceptions and errors correctly to prevent critical information from being exposed to potential attackers. Avoid displaying detailed error messages in production environments, as they may reveal sensitive information that can be exploited by hackers.

def function_with_potential_exception():
try:
# Code that may raise an exception
result = 1 / 0
return result
except Exception as e:
# Handle the exception gracefully
log_error(e)
return None

def log_error(error):
# Log the error without revealing sensitive information
logger.error("An error occurred")

Google Apps Script for Secure Coding #

Google Apps Script provides a platform for automating tasks and extending the functionality of various Google services like Sheets, Docs, and Forms. While it is primarily focused on JavaScript, it is also possible to write secure code using Google Apps Script.

For example, let's consider a use case where we want to restrict access to a Google Sheet. We can use Google Apps Script to implement secure authentication and authorization.

function onOpen() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var menuItems = [
{name: 'Access Control', functionName: 'showAccessControlDialog'},
];
ss.addMenu('Secure Menu', menuItems);
}

function showAccessControlDialog() {
var ui = SpreadsheetApp.getUi();
var user = Session.getActiveUser().getEmail();

// Perform authorization checks here based on user's email

if (user === 'admin@example.com') {
ui.alert('Access granted to admin role');
} else {
ui.alert('Access denied');
}
}

In the above Google Apps Script code, we create a custom menu item 'Access Control' which triggers the function showAccessControlDialog(). Inside that function, we can perform any necessary authorization or authentication checks to determine whether access should be granted or denied.

By using Google Apps Script, we can extend the security features of Google services and create more secure applications.

Use Cases Examples #

  • Building a web application that handles user registration and login. Implement secure password hashing and enforce strong input validation to prevent common vulnerabilities like brute force attacks or injection attacks.

  • Developing an API server that interacts with a database. Use parameterized queries to protect against SQL injection attacks and ensure proper access control mechanisms to restrict unauthorized access to sensitive data.

  • Creating a web scraping script that pulls data from external websites. Implement proper input validation and carefully analyze the target website's terms of service to ensure that accessing and scraping the data is performed legally and ethically.

In conclusion, secure coding in Python is a critical aspect of developing robust and safe applications. By following the manual techniques discussed above and leveraging platforms like Google Apps Script when applicable, developers can significantly enhance the security of their Python code and protect against potential vulnerabilities and attacks.