attack-surface.md

Attack Surface Analysis for bcit-ci/codeigniter

Attack Surface: Unvalidated Input (Beyond XSS) - Leveraging CodeIgniter's Input Class Inadequately

• Description: Failure to perform comprehensive input validation beyond basic XSS filtering provided by CodeIgniter's input class, leading to injection vulnerabilities (SQLi, command injection) and logic errors. This is specifically about not using CodeIgniter's validation tools effectively.
• CodeIgniter Contribution: The input class offers basic filtering (e.g., $this->input->post('something', TRUE) for XSS), but does not enforce data types, lengths, formats, or business rules. Developers must actively use the Form Validation library or custom validation, and often fail to do so comprehensively.
• Example: A developer uses $this->input->post('user_id') without further validation, assuming it will be an integer. An attacker provides 1; DROP TABLE users;--, leading to SQL injection.
• Impact: Data corruption, data loss, unauthorized data access, complete system compromise (depending on the injection type).
• Risk Severity: Critical
• Mitigation Strategies:
  • Mandatory Use of Form Validation Library: Enforce the use of CodeIgniter's Form Validation library for all form fields and any user-supplied data. Define strict rules for data types, lengths, formats, and allowed values.
  • Prepared Statements/Query Builder (with Caution): Always use CodeIgniter's Active Record or Query Builder for database interactions. However, be aware that even these can be misused; avoid direct concatenation of user input within query building methods.
  • Input Sanitization (Type-Specific): Sanitize input after validation, using appropriate functions for the expected data type (e.g., intval() for integers, floatval() for floats). This is a secondary defense.
  • Whitelist Validation: Whenever possible, validate against a whitelist of allowed values, rather than attempting to blacklist malicious input.

Attack Surface: Over-Reliance on CodeIgniter's XSS Filter (and Ignoring Output Encoding)

• Description: The incorrect assumption that CodeIgniter's built-in XSS filter ($this->input->post('something', TRUE) or the global filter) provides complete XSS protection, leading to a neglect of proper output encoding.
• CodeIgniter Contribution: CodeIgniter provides an XSS filter, but its documentation and common usage patterns can lead developers to believe it's a complete solution, which it is not. The existence of the filter can create a false sense of security.
• Example: A developer uses $this->input->post('comment', TRUE) to filter user comments and then displays them directly in an HTML page without using html_escape(). An attacker crafts a bypass for the filter, injecting malicious JavaScript.
• Impact: Session hijacking, defacement, phishing, malware distribution.
• Risk Severity: High
• Mitigation Strategies:
  • Prioritize Output Encoding: Always use context-appropriate output encoding (e.g., html_escape() for HTML, htmlspecialchars() in attributes) when displaying any user-supplied data, regardless of whether the input was filtered. This is the primary defense against XSS.
  • Selective XSS Filtering: Use the CodeIgniter XSS filter selectively, only where it's deemed necessary, and never globally. Understand its limitations.
  • Content Security Policy (CSP): Implement a strong CSP as a defense-in-depth measure to limit the impact of successful XSS attacks.

Attack Surface: Unrestricted File Uploads (Misusing CodeIgniter's File Uploading Class)

• Description: Improper configuration of CodeIgniter's File Uploading Class, allowing attackers to upload malicious files.
• CodeIgniter Contribution: The File Uploading Class provides the mechanism for file uploads, but its security depends entirely on the developer's configuration choices. The default settings are not secure.
• Example: A developer uses the File Uploading Class but fails to set $config['allowed_types']. An attacker uploads a PHP shell script (e.g., shell.php) and executes it on the server.
• Impact: Complete system compromise, data theft, malware distribution.
• Risk Severity: Critical
• Mitigation Strategies:
  • Strictly Limit Allowed File Types: Use $config['allowed_types'] to define a whitelist of allowed file extensions (e.g., gif|jpg|png). Never rely on blacklisting.
  • Sanitize File Names (Using CodeIgniter's Helper): Always use $this->security->sanitize_filename() to remove potentially dangerous characters from uploaded file names. Strongly consider generating unique, random file names on the server.
  • Enforce File Size Limits: Use $config['max_size'] to prevent denial-of-service attacks via excessively large file uploads.
  • Store Files Outside Web Root: Store uploaded files in a directory that is not directly accessible from the web. This is crucial.
  • Validate File Content (Beyond Extension): If possible, validate the actual content of the file, not just the extension (e.g., using a library to check image headers for image uploads).

Attack Surface: Session Fixation (Due to CodeIgniter's Default Behavior)

• Description: Vulnerability to session fixation attacks because CodeIgniter does not automatically regenerate the session ID after a user successfully authenticates.
• CodeIgniter Contribution: CodeIgniter's session management library provides the functionality, but the responsibility for regenerating the session ID after login rests solely with the developer. This is a common oversight.
• Example: An attacker sets a user's session ID to a known value (e.g., via a crafted URL). When the user logs in, the attacker can then use that same session ID to hijack the user's session.
• Impact: Session hijacking, unauthorized access to user accounts and data.
• Risk Severity: High
• Mitigation Strategies:
  • Mandatory Session Regeneration: Always call $this->session->sess_regenerate() immediately after a successful user login. This is the single most important mitigation.
  • HTTPS Enforcement: Ensure the entire application, especially login and session-related pages, uses HTTPS to prevent session ID interception over the network.

Attack Surface: Disabled or Misconfigured CSRF Protection (Ignoring CodeIgniter's Built-in Feature)

• Description: Vulnerability to Cross-Site Request Forgery (CSRF) attacks due to either disabling CodeIgniter's built-in protection or failing to properly include CSRF tokens in forms.
• CodeIgniter Contribution: CodeIgniter provides built-in CSRF protection, but it's not enabled by default, and developers must actively use it (either via form_open() or manual token inclusion).
• Example: A developer disables CSRF protection ($config['csrf_protection'] = FALSE;) or creates forms without using form_open() or manually adding the CSRF token. An attacker can then forge requests on behalf of authenticated users.
• Impact: Unauthorized actions performed on behalf of the user (e.g., changing passwords, making purchases, deleting data).
• Risk Severity: High
• Mitigation Strategies:
  • Enable CSRF Protection: Set $config['csrf_protection'] = TRUE; in config.php. This is essential.
  • Use form_open() Consistently: Use CodeIgniter's form_open() helper function to automatically include the CSRF token in all forms. This is the preferred method.
  • Manual Token Inclusion (If Necessary): If form_open() cannot be used, manually add the CSRF token to forms using $this->security->get_csrf_token_name() and $this->security->get_csrf_hash().
  • Token Verification (Automatic): CodeIgniter automatically verifies the CSRF token on POST requests when protection is enabled. Ensure this verification is not bypassed.

Attack Surface: Exposed Database Credentials (Due to Default Configuration File)

• Description: Storing database credentials directly within the database.php file, which, if misconfigured or if the server is compromised, can lead to credential exposure.
• CodeIgniter Contribution: CodeIgniter, by default, uses the database.php file for database configuration. This is a standard practice, but it places the onus on the developer/administrator to secure this file properly.
• Example: An attacker gains read access to the server's file system and obtains the database credentials from application/config/database.php.
• Impact: Complete database compromise, data theft, data modification, potential for further system compromise.
• Risk Severity: Critical
• Mitigation Strategies:
  • Environment Variables (Primary): Store database credentials (and other sensitive configuration) in environment variables, not directly in database.php. CodeIgniter can then read these variables.
  • Secure Configuration Management: Use a dedicated, secure configuration management system (e.g., HashiCorp Vault, AWS Secrets Manager, Azure Key Vault) to store and manage sensitive credentials.
  • Restrictive File Permissions: If, for some reason, environment variables or a secrets manager cannot be used, ensure that database.php has the most restrictive file permissions possible (e.g., readable only by the web server user and no one else). This is a last resort.