A Comprehensive Guide to Implementing SAST Tools

In 2023, the number of data breaches hit a record high of 3,205 incidents — a shocking 78% increase compared to the previous year. As data attacks rise, modern organizations are embracing a new approach to application security (shifting left) that integrates security testing earlier in the software development lifecycle (SDLC). 

Static Application Security Testing (SAST) tools are one key element in this shifting left approach. SAST tools scan an application's source code for potential security vulnerabilities and provide timely feedback to developers about issues that are introduced during development. 

Understanding how to implement SAST tools into your software development process can strengthen your application's security posture and empower your developers to write secure code from the start.

This comprehensive guide explores SAST tools, explaining their functionalities and key strategies for implementing them into your software development workflow.

Why Use a SAST Tool?

SAST tools provide several benefits that make them an essential part of a comprehensive application security strategy. Some of these benefits include:

1. Early Detection of Vulnerabilities: SAST tools excel at identifying security vulnerabilities early in the development cycle. Scanning source code before deployment, they catch issues such as SQL injection attacks, cross-site scripting, and misconfigured settings, preventing these vulnerabilities from reaching production.
   
   
2. Integration With Development Tools: Many SAST tools integrate with popular development environments and version control systems. They can analyze large codebases efficiently, prioritize vulnerabilities based on severity, and automate the generation of detailed reports for developers and security teams. This codebase integration enables developers to run security scans directly from their IDEs, facilitating continuous security testing and rapid feedback loops.
   
   
3. Empowering Developers With Security Knowledge: Incorporating SAST tools into the development workflow educates developers about secure coding practices and common security pitfalls. By receiving feedback on security issues directly in their development environment, developers learn to write more secure code and contribute to a culture of security awareness within the organization.

How Do SAST Tools Work?

Static Application Security Testing (SAST) tools continuously analyze your application's source code, bytecode, and binaries to uncover potential security vulnerabilities. Let's explore how they work step-by-step using a SQL injection example.

1. Source Code Ingestion

Connecting your application's source code to the SAST tool starts the process. You can do this manually by uploading your code files to the SAST tool’s site or integrating the SAST tool with your development environment for automatic scans. Here’s a code snippet of a login query susceptible to SQL injection:

​​username = request.getParameter("username");
password = request.getParameter("password");
query = "SELECT * FROM users WHERE username = '" + username + "' AND password = '" + password + "'";

2. Code Parsing and Tokenization

The SAST tool doesn't scan the code blindly. First, it breaks it down into fundamental building blocks like keywords, variables, and function calls. Our code snippet would look like this:

IDENTIFIER, ASSIGNMENT_OPERATOR, METHOD_CALL, LPAREN, STRING_LITERAL, RPAREN, SEMICOLON,
IDENTIFIER, ASSIGNMENT_OPERATOR, METHOD_CALL, LPAREN, STRING_LITERAL, RPAREN, SEMICOLON,
IDENTIFIER, ASSIGNMENT_OPERATOR, STRING_LITERAL, PLUS, IDENTIFIER, PLUS, STRING_LITERAL, PLUS, IDENTIFIER, PLUS, STRING_LITERAL, SEMICOLON

These are then transformed into tokens to make it easier to analyze.

3. Code Abstraction

Most SAST tools visualize the source code as a tree to help users understand its meaning and structure. An abstract syntax tree (AST) transforms lines of code into a hierarchical structure to show relationships between different aspects of code. SAST tools build an AST to represent the structure and flow of the code, enabling deeper analysis. 

 VariableDeclarationStatement
    /                            \
IDENTIFIER                    AssignmentExpression
"username"                    /                    \
                        MethodCallExpression    IDENTIFIER
                        /            |            \
                    IDENTIFIER    ArgumentList    
"request.getParameter('username')"
                    "request"      /        \
                                LPAREN   STRING_LITERAL
                                            "'username'"

    VariableDeclarationStatement
    /                            \
IDENTIFIER                    AssignmentExpression
"password"                   /                    \
                        MethodCallExpression    IDENTIFIER
                        /            |            \
                    IDENTIFIER    ArgumentList   
"request.getParameter('password')"
                    "request"      /        \
                                LPAREN   STRING_LITERAL
                                            "'password'"

    VariableDeclarationStatement
    /                            \
IDENTIFIER                    AssignmentExpression
"query"                       /                    \
                        BinaryExpression        IDENTIFIER
                        /                \
                STRING_LITERAL        BinaryExpression
                "SELECT * FROM..."    /                \
                                STRING_LITERAL        IDENTIFIER
                                "' AND password = '"  "password"

This AST representation shows the code's hierarchical structure, including variable declarations, method calls, and other language constructs. 

4. Signature-Based Pattern Matching

SAST tools then employ various techniques on the AST to uncover security weaknesses; one of them is signature-based pattern matching. This looks for known patterns or signatures of vulnerabilities in the source code. In this case, a SAST tool looks for known patterns like string concatenation with variables ("... = '" + variable + "'") that indicate potential SQL injection.

5. Semantic Analysis

SAST tools also perform semantic analysis on the source code. Semantic analysis goes beyond pattern matching and considers the code's context, logic, and dependencies. In this example, the SAST tool would analyze the code semantically to understand that the `username` and `password` variables are derived from user input (`request.getParameter()`) and that these values are being directly concatenated into a SQL query string without proper sanitization or validation.

The SAST tool would recognize that this practice is insecure and could potentially lead to SQL injection attacks if the user input contains malicious SQL code. It would also consider the surrounding context, such as whether the code is part of a web application or a database interaction module, to better assess the risk and impact of the vulnerability.

6. Taint Analysis

The third type of vulnerability analysis SAST tools perform is called taint analysis. Taint analysis is a form of data flow analysis that tracks the flow of untrusted data (or "tainted" data) through the application. In our SQL injection example, the SAST tool would identify the `request.getParameter()` calls as sources of tainted data, as they retrieve user input from the request parameters.

The SAST tool would then follow the flow of this tainted data through the code, tracking how the `username` and `password` variables are used. When it sees that these tainted values are directly concatenated into the SQL query string without proper sanitization, it would flag this as a potential SQL injection vulnerability, as the tainted user input could potentially introduce malicious SQL code into the query.

By combining these three techniques — signature-based pattern matching, semantic analysis, and taint analysis — SAST tools can effectively detect SQL injection vulnerabilities and other security issues in the source code

7. Vulnerability Alerting

If the SAST tool identifies a known pattern-matching vulnerability, it triggers an alert. This alert details the location of the vulnerability in the code (line number, function name), the specific type of vulnerability detected (SQL injection, in our case), and its potential severity (low, high, medium). This helps developers pinpoint the exact area requiring attention.

8. Remediation Guidance

Many SAST tools go beyond pointing out vulnerabilities. They offer valuable guidance on how to fix the issue. This could involve suggesting specific code changes to address the vulnerability, providing links to secure coding best practices, or recommending secure coding libraries that can be incorporated. In our SQL vulnerability example, the SAST tool could suggest remediation steps such as parameterized queries or input validation functions.

How To Implement SAST Tools in Your Organization

Implementing SAST tools is crucial in securing your organization's applications and codebase. These six steps can help you effectively integrate SAST tools into your organization's practices.

1. Assess the Scope of the Codebase

Start by identifying all the applications and modules that need to be scanned. Ensure all relevant code is included in the scan to identify potential vulnerabilities across your codebase.

2. Find the Right SAST Tool

When choosing a SAST tool, consider the following key factors:

• Programming Language Support: Many SAST tools support only a limited range of programming languages, so ensure the tool can scan all the languages used in your applications.
  
  
• Scanning Approach: Understand how the tool performs scans and whether it fits your development environment. 
  
  
• Vulnerability Detection: Evaluate the SAST tool's ability to detect vulnerabilities relevant to your code context. At a minimum, it should cover the OWASP Top 10 and other popular security issues.
  
  
• Configurability: Look for a tool that allows you to customize the results, the reports, and the types of issues it finds. 
  
  
• Licensing and Pricing: Consider the licensing model and pricing structure, as this can significantly impact the overall cost of implementation and ongoing use.

3. Create the Infrastructure and Deploy the SAST Tool

Decide on the deployment method that best suits your needs, whether on-premises or in the cloud. Handle the necessary licensing requirements, set up the required resources (databases, servers), and configure access control and authorization.

4. Configure Your Scan Settings

Define the scope of the scans and configure any custom rules or signatures you want the tool to use. Establish scan policies to ensure consistency and thoroughness. Additionally, determine how to handle false positives and negatives to improve the accuracy of the scan results.

5. Evaluate the Scan Results

Review the initial scan results, considering the application's context, such as user information, security mechanisms, and input validation. This will help you assess the results and identify genuine issues. Perform incremental or differential scans to ensure ongoing security as the codebase changes.

6. Integrate SAST Tools Into Your CI/CD Pipeline

Automate the SAST process by integrating the tool into your continuous integration and continuous delivery (CI/CD) pipeline. This allows you to run vulnerability scans with every code push or build, ensuring security is continuously enforced throughout the development lifecycle.

Don't Let Your SAST Tool Hold You Back

As we've discussed, SAST is not just about finding vulnerabilities but about fostering a culture of security-minded development from the beginning. The right SAST tool can significantly enhance your development processes' security posture and efficiency.

When making your final choice, we encourage you to consider Codacy Security. Codacy's SAST tool supports over 40 programming languages, including Java, Python, JavaScript, and C#. It can detect comprehensive vulnerabilities, including those from the OWASP Top 10, and provides customizable rules to fit your specific security requirements.

Codacy's SAST functionality can seamlessly integrate into your CI/CD pipeline, allowing you to continuously scan your codebase without disrupting your workflow. With its intuitive dashboard and detailed reports, Codacy makes tracking and managing vulnerabilities throughout your software development lifecycle easy. 

Explore Codacy's SAST capabilities and see how it can enhance your organization's application security. Start for free today.