threat-modeling.md

Threat Model Analysis for yourls/yourls

Threat: Open Redirection

Threat: Open Redirection

Description: An attacker crafts a shortened YOURLS URL that, when clicked, redirects the user to a malicious website. This is achieved by exploiting vulnerabilities in YOURLS redirection logic, allowing manipulation of the redirection target. Attackers use this for phishing, malware distribution, or SEO spam.

Impact: User compromise (phishing, malware infection), reputation damage.

Affected YOURLS Component: URL Redirection Functionality, Core Application Logic

Risk Severity: High

Mitigation Strategies:

• Implement strict input validation and sanitization for redirection targets in YOURLS code.
• Use a whitelist of allowed domains for redirection targets within YOURLS configuration (if feasible).
• Consider displaying a warning page before redirecting to external URLs in YOURLS templates.
• Regularly update YOURLS to the latest version to patch known open redirection vulnerabilities.

Threat: Redirection Target Manipulation

Threat: Redirection Target Manipulation

Description: An attacker injects malicious code or modifies the intended redirection target during the YOURLS URL shortening process. This is done by exploiting input validation flaws in YOURLS URL submission forms or API endpoints. This leads to users being redirected to unintended malicious websites.

Impact: User compromise (phishing, malware infection), reputation damage, data theft.

Affected YOURLS Component: URL Shortening Functionality, Input Validation, API (if used)

Risk Severity: High

Mitigation Strategies:

• Implement robust input validation and sanitization for all URL inputs within YOURLS code.
• Use URL parsing libraries within YOURLS to properly handle and validate URLs.
• Enforce URL format restrictions and reject invalid or suspicious URLs in YOURLS input processing.
• Regularly audit YOURLS code for input validation vulnerabilities.

Threat: URL Injection through Keywords

Threat: URL Injection through Keywords

Description: An attacker injects malicious code into custom keywords during YOURLS URL shortening. If keyword output is not properly encoded by YOURLS, this leads to Cross-Site Scripting (XSS) vulnerabilities when the keyword is displayed in URLs, admin panels, or statistics pages.

Impact: Cross-Site Scripting (XSS), account compromise, malicious script execution in user browsers.

Affected YOURLS Component: Keyword Input Handling, Keyword Output Display, Admin Interface, Statistics Pages

Risk Severity: High

Mitigation Strategies:

• Implement strict input validation and sanitization for keyword inputs within YOURLS code.
• Properly encode keyword output when displaying them in HTML contexts within YOURLS templates and admin interface (e.g., using HTML entity encoding).
• Use a Content Security Policy (CSP) configured within the web server to mitigate XSS risks for the YOURLS application.
• Regularly audit YOURLS code for XSS vulnerabilities related to keyword handling.

Threat: Malicious or Vulnerable Plugins

Threat: Malicious or Vulnerable Plugins

Description: An attacker installs a malicious plugin or exploits vulnerabilities in poorly written YOURLS plugins. Malicious plugins can contain backdoors or steal data. Vulnerable plugins introduce security flaws like XSS, SQL Injection, or Remote Code Execution within the YOURLS instance.

Impact: Full application compromise, data breach, server compromise, denial of service.

Affected YOURLS Component: Plugin System, Plugin Installation, Plugin Execution

Risk Severity: Critical

Mitigation Strategies:

• Only install plugins from trusted and reputable sources for YOURLS.
• Thoroughly review plugin code before installation (if possible) for YOURLS plugins.
• Keep plugins updated to the latest versions to patch known vulnerabilities in YOURLS.
• Implement a plugin security policy and guidelines for developers contributing to YOURLS plugin ecosystem.
• Consider disabling or removing unnecessary plugins in YOURLS.

Threat: Insecure Plugin Installation/Update Process

Threat: Insecure Plugin Installation/Update Process

Description: An attacker intercepts or manipulates the YOURLS plugin installation or update process if it lacks integrity checks or secure communication. This allows them to inject malicious plugins or modified versions of legitimate plugins, compromising the YOURLS instance.

Impact: Installation of malicious plugins, application compromise, data breach.

Affected YOURLS Component: Plugin Installation Mechanism, Plugin Update Mechanism

Risk Severity: High

Mitigation Strategies:

• Use HTTPS for plugin downloads and updates within YOURLS plugin management.
• Implement integrity checks (e.g., checksum verification) for plugin files in YOURLS plugin installation process.
• Verify plugin signatures if available in YOURLS plugin system.
• Restrict plugin installation to administrators only in YOURLS configuration.

Threat: Admin Authentication Bypass

Threat: Admin Authentication Bypass

Description: An attacker exploits vulnerabilities in the YOURLS admin login mechanism to bypass authentication and gain unauthorized access to the YOURLS admin interface. This could be through SQL Injection, brute-force attacks (if not properly protected by YOURLS), or logic flaws in YOURLS authentication code.

Impact: Full administrative control, data manipulation, application takeover, user data compromise.

Affected YOURLS Component: Admin Login Functionality, Authentication System

Risk Severity: Critical

Mitigation Strategies:

• Use strong password hashing algorithms in YOURLS authentication.
• Implement rate limiting and account lockout mechanisms in YOURLS to prevent brute-force attacks.
• Enforce strong password policies for administrators of YOURLS.
• Regularly audit YOURLS authentication code for vulnerabilities.
• Consider using multi-factor authentication for admin access to YOURLS.

Threat: Admin Session Management Issues

Threat: Admin Session Management Issues

Description: An attacker exploits weaknesses in YOURLS admin session management, such as predictable session IDs, session fixation vulnerabilities, or lack of proper session expiration. This allows them to hijack an administrator's session and gain unauthorized access to the YOURLS admin interface.

Impact: Unauthorized admin access, data manipulation, application takeover.

Affected YOURLS Component: Admin Session Handling, Session Management

Risk Severity: High

Mitigation Strategies:

• Use cryptographically secure random session IDs in YOURLS session management.
• Implement proper session regeneration after login in YOURLS.
• Set appropriate session expiration times and timeouts in YOURLS configuration.
• Use secure session storage mechanisms for YOURLS sessions.
• Protect against session fixation attacks in YOURLS session handling.

Threat: Cross-Site Scripting (XSS) in Admin Interface

Threat: Cross-Site Scripting (XSS) in Admin Interface

Description: An attacker injects malicious scripts into input fields or data displayed within the YOURLS admin interface. When an administrator accesses the affected page, the script executes in their browser, potentially allowing the attacker to steal admin session cookies, perform actions on behalf of the administrator, or deface the YOURLS admin interface.

Impact: Admin account compromise, data theft, defacement of admin interface, further attacks on users.

Affected YOURLS Component: Admin Interface, Input Handling in Admin Pages, Output Display in Admin Pages

Risk Severity: High

Mitigation Strategies:

• Implement robust input validation and sanitization for all admin interface inputs in YOURLS code.
• Properly encode output displayed in the YOURLS admin interface (e.g., using HTML entity encoding).
• Use a Content Security Policy (CSP) to mitigate XSS risks for the YOURLS admin interface.
• Regularly audit YOURLS admin interface code for XSS vulnerabilities.

Threat: Exposure of Original URLs

Threat: Exposure of Original URLs

Description: If the database or storage mechanism containing the mapping between shortened and original URLs in YOURLS is not properly secured, an attacker could gain unauthorized access and retrieve sensitive information contained in the original URLs. This could be through SQL Injection vulnerabilities in YOURLS or database misconfiguration.

Impact: Information disclosure, privacy breach, exposure of sensitive data within original URLs.

Affected YOURLS Component: Database, Data Storage, URL Mapping Logic

Risk Severity: High

Mitigation Strategies:

• Secure database access with strong credentials and access controls for YOURLS database.
• Implement proper database security hardening measures for YOURLS database server.
• Encrypt sensitive data in the YOURLS database if necessary.
• Restrict access to YOURLS database backups and configuration files.

Threat: Insecure Default Configuration

Threat: Insecure Default Configuration

Description: YOURLS ships with insecure default configurations, such as weak default admin credentials. If administrators fail to change these defaults, attackers can easily exploit them to gain unauthorized access to the YOURLS instance.

Impact: Easy initial access for attackers, application compromise, data breach.

Affected YOURLS Component: Default Configuration, Installation Process

Risk Severity: High

Mitigation Strategies:

• Change default admin credentials immediately after YOURLS installation.
• Review and harden other default configuration settings in YOURLS.
• Provide clear instructions and warnings to users about changing default configurations during YOURLS installation and setup.
• Consider shipping with more secure default configurations in future YOURLS versions.

Threat: Misconfiguration leading to Vulnerabilities

Threat: Misconfiguration leading to Vulnerabilities

Description: Incorrect configuration of YOURLS itself, such as improper file permissions for YOURLS files or exposed YOURLS configuration files due to web server misconfiguration, introduces vulnerabilities that attackers can exploit. For example, publicly accessible config.php or incorrect file permissions allowing unauthorized modification of YOURLS files.

Impact: Various vulnerabilities depending on the misconfiguration, ranging to full application compromise, data breach, or code execution.

Affected YOURLS Component: Server Configuration, YOURLS Configuration, Deployment Environment

Risk Severity: Critical

Mitigation Strategies:

• Follow security best practices for server and web server configuration when deploying YOURLS.
• Use secure file permissions for YOURLS files and directories, ensuring web server cannot write to sensitive files.
• Regularly review and audit YOURLS and server configurations for security best practices.
• Use configuration management tools to ensure consistent and secure YOURLS configurations across deployments.

Threat: Exposure of Configuration Files

Threat: Exposure of Configuration Files

Description: Web server misconfiguration allows direct web access to YOURLS configuration files (e.g., config.php). These files often contain sensitive information like database credentials and salts, leading to full YOURLS application compromise if exposed.

Impact: Full application compromise, data breach, server compromise.

Affected YOURLS Component: Web Server Configuration, Configuration File Storage

Risk Severity: Critical

Mitigation Strategies:

• Configure web server to explicitly deny direct access to YOURLS configuration files (e.g., using .htaccess in Apache or location blocks in Nginx).
• Store YOURLS configuration files outside of the web root if possible.
• Regularly audit web server configuration to ensure configuration files are not publicly accessible.