Fundamental principles for writing more secure software.
Secure coding practices are a set of guidelines and principles that developers should follow to write software that is resilient to attacks. Building security into the software development lifecycle from the beginning is far more effective and less costly than trying to patch vulnerabilities after a product has been deployed. Here are some fundamental principles: 1. Validate All Input: Treat all data coming from an external source—whether it's a user, another application's API, or a file—as untrusted. Input validation involves checking that the data is in the expected format, type, and range before it is processed. This is the primary defense against injection-style attacks. 2. Sanitize and Encode Output: Before displaying any data back to a user, especially if it originated from an external source, it must be properly encoded for the context in which it's being displayed (e.g., HTML encoding, URL encoding). This is the main defense against Cross-Site Scripting (XSS). 3. Principle of Least Privilege: As discussed before, applications and their components should run with the minimum level of privilege necessary to function. This limits the damage an attacker can do if they manage to exploit a vulnerability. 4. Defense in Depth: Don't rely on a single security control. Use multiple, layered defenses. For example, in addition to using parameterized queries to stop SQLi, you could also use a web application firewall (WAF) and ensure the database user has minimal permissions. 5. Fail Securely: Applications should handle errors gracefully and without revealing sensitive information (like stack traces or database error messages) that could help an attacker. When an application fails, it should do so in a way that leaves the system in a secure state. 6. Keep Security Simple: Complex systems are harder to secure. Strive for simple, straightforward designs as they are easier to analyze and protect.