Secure Coding Practices

1. Input Validation

Input validation is the process of ensuring that user inputs conform to expected formats and types. This practice prevents malicious inputs from exploiting vulnerabilities such as SQL injection and cross-site scripting (XSS). Input validation should be performed both on the client side and server side to ensure comprehensive security.

Example: When a user enters an email address into a form, the system checks if the input matches the expected email format (e.g., name@domain.com). If the input does not match, the system rejects it and prompts the user to enter a valid email address.

2. Output Encoding

Output encoding involves converting data into a safe format before displaying it to the user. This practice prevents XSS attacks by ensuring that any potentially harmful characters are rendered harmless. Output encoding should be applied to all dynamic content that is sent to the browser.

Example: If a user enters a comment containing HTML tags, the system encodes these tags (e.g., converting "<" to "<" and ">" to ">") before displaying the comment. This ensures that the tags are not interpreted as HTML by the browser, preventing XSS attacks.

3. Parameterized Queries

Parameterized queries are a technique used to prevent SQL injection attacks. By using placeholders for parameters in SQL queries, the database engine can distinguish between code and data, ensuring that user inputs are treated as data and not executable code.

Example: Instead of constructing an SQL query as "SELECT * FROM users WHERE username = '" + userInput + "'", a parameterized query would be written as "SELECT * FROM users WHERE username = ?", with the user input passed as a parameter. This ensures that any malicious input is treated as a string and not executable SQL code.

4. Error Handling

Error handling involves managing and responding to errors in a way that does not expose sensitive information to attackers. Proper error handling ensures that error messages provide useful information to legitimate users while hiding details that could be exploited by attackers.

Example: When a user attempts to log in with incorrect credentials, the system should display a generic error message such as "Invalid username or password" instead of detailed error messages like "The username does not exist" or "The password is incorrect". This prevents attackers from gaining information about the system's structure and potential vulnerabilities.