Skip to content

Latest commit

 

History

History
176 lines (143 loc) · 15.7 KB

sec-design-deep-analysis.md

File metadata and controls

176 lines (143 loc) · 15.7 KB

Okay, let's perform a deep security analysis of the "whoops" project based on the provided design review and the GitHub repository (https://github.com/filp/whoops).

1. Objective, Scope, and Methodology

  • Objective: To conduct a thorough security analysis of the "whoops" library, focusing on identifying potential vulnerabilities, assessing their impact, and providing actionable mitigation strategies. The analysis will cover key components, data flow, and configuration options, with a particular emphasis on information disclosure and injection vulnerabilities.

  • Scope:

    • The core "whoops" library itself (PHP code).
    • Configuration options and their security implications.
    • Interaction with the host application (how "whoops" receives and processes data).
    • Dependencies managed by Composer (indirectly, focusing on known vulnerabilities).
    • The provided security design review document.

  • Methodology:

    1. Code Review: Manual inspection of the PHP source code to identify potential vulnerabilities, focusing on areas like input handling, output encoding, and data sanitization.
    2. Dependency Analysis: Examination of the composer.json and composer.lock files to identify dependencies and check for known vulnerabilities.
    3. Architecture and Data Flow Analysis: Inferring the architecture and data flow based on the code, documentation, and design review, to understand how data is handled and where vulnerabilities might exist.
    4. Threat Modeling: Identifying potential threats based on the identified vulnerabilities and the library's intended use case.
    5. Mitigation Strategy Development: Proposing specific, actionable steps to mitigate the identified threats.

2. Security Implications of Key Components

Let's break down the key components and their security implications, drawing from the code and design review:

  • Whoops\Run (Main Class):

    • handleException($exception): This is the core entry point. It receives the Throwable object (Exception or Error) from the PHP application. The security risk here is that the exception object itself might contain sensitive data in its message, trace, or previous exceptions.
    • register() / unregister(): These methods register and unregister "whoops" as the default exception handler. A security concern here is if an attacker could somehow manipulate the application to unregister a secure exception handler and replace it with a malicious one, or unregister whoops leaving the application with a less secure default handler. This is a lower risk, as it requires significant control over the application.
    • pushHandler($handler) / popHandler(): Whoops allows pushing and popping custom handlers. The security implication is that a poorly written or malicious handler could expose sensitive information or introduce other vulnerabilities. The order of handlers is also important.
    • sendHttpCode($code): Sets the HTTP response code. While not a direct security vulnerability, incorrect usage could lead to misleading error reporting or potentially be abused in combination with other vulnerabilities.

  • Handlers (e.g., PrettyPageHandler, JsonResponseHandler, PlainTextHandler):

    • handle(): Each handler's handle() method is responsible for generating the output (HTML, JSON, plain text). This is the most critical area for security vulnerabilities, specifically information disclosure and XSS.
    • PrettyPageHandler: This is the default handler, generating the visually appealing HTML error page.
      • Information Disclosure: The PrettyPageHandler displays a wealth of information:
        • Stack Trace: Shows the code execution path, potentially revealing file paths, function names, and variable values.
        • Request Information: Includes GET, POST, COOKIE, and SESSION data. This is extremely dangerous if not carefully controlled, as it could expose sensitive user data, tokens, or credentials.
        • Environment Variables: Displays server environment variables, which might include database credentials, API keys, or other secrets.
        • Table of Application & Framework Information: Includes versions, which can help attackers identify known vulnerabilities.
      • XSS: If any of the displayed data (especially request data) is not properly escaped, it could lead to XSS vulnerabilities. For example, a malicious GET parameter could inject JavaScript code that would be executed in the context of the error page.
    • JsonResponseHandler: Generates a JSON response. The same information disclosure risks as PrettyPageHandler apply, but the attack vector is different (JSON injection instead of HTML injection).
    • PlainTextHandler: Generates a plain text response. Information disclosure is still a risk, but XSS is less likely (though not impossible, depending on how the output is used).

  • Frames (Whoops\Frame\Frame, Whoops\Frame\FrameCollection):

    • These represent individual frames in the stack trace. They contain information about the file, line number, function, class, and arguments. The arguments are particularly sensitive, as they could contain user data or internal application state.
    • The FrameCollection class provides methods for filtering and manipulating frames. Incorrect filtering could lead to sensitive frames being exposed.

  • Inspector (Whoops\Inspector):

    • Provides methods for inspecting the exception and its frames. It's a helper class used by the handlers. The security risk here is primarily indirect – if the Inspector provides inaccurate or incomplete information, it could lead to vulnerabilities in the handlers.

  • Configuration:

    • $editor: Allows configuring a code editor link. If this is not properly sanitized, it could be an XSS vector.
    • $blacklist: Whoops has a blacklist feature to prevent certain values from being displayed in superglobals (e.g., $_ENV, $_SERVER). This is a crucial security feature, but it relies on the developer to configure it correctly. It's not a foolproof solution, as attackers might find ways to bypass the blacklist.
    • $extraTables: Allows adding custom data tables to the output. This is a potential information disclosure risk if not used carefully.
    • $logger: Allows configuring a logger. While not a direct security vulnerability, the logger itself should be secured to prevent unauthorized access to logged error data.

3. Architecture and Data Flow

  1. Error Occurs: An unhandled exception or error occurs within the PHP application.
  2. Whoops Intercepts: If "whoops" is registered as the exception handler, it intercepts the Throwable object.
  3. Inspector Creates: A Whoops\Inspector is created to analyze the exception.
  4. Handlers are Called: The Whoops\Run object iterates through the registered handlers.
  5. Handler Processes: Each handler's handle() method is called. The handler uses the Inspector to access information about the exception and its frames.
  6. Output Generated: The handler generates the output (HTML, JSON, or plain text).
  7. Response Sent: The output is sent to the browser (or client).

4. Identified Threats (Specific to Whoops)

  • T1: Sensitive Information Disclosure (High Severity):

    • Description: Exposure of sensitive data (database credentials, API keys, session tokens, user data, internal file paths, etc.) in the error output.
    • Attack Vector: Unconfigured or misconfigured "whoops" installation, especially in production environments. Exploitation of application vulnerabilities that lead to exceptions containing sensitive data.
    • Impact: Compromise of application data, accounts, or the entire system.

  • T2: Cross-Site Scripting (XSS) (High Severity):

    • Description: Injection of malicious JavaScript code into the error page.
    • Attack Vector: Unescaped user input (GET, POST, COOKIE data) displayed on the error page. Exploitation of application vulnerabilities that allow attackers to control parts of the exception message or other data displayed by "whoops."
    • Impact: Theft of user cookies, session hijacking, defacement of the website, phishing attacks.

  • T3: Denial of Service (DoS) (Low-Medium Severity):

    • Description: "whoops" itself could be used to trigger a DoS attack if it consumes excessive resources (CPU, memory) while processing a large or complex exception.
    • Attack Vector: Crafting malicious input that triggers a very deep or recursive exception, or exploiting a vulnerability in "whoops" that leads to resource exhaustion.
    • Impact: Application becomes unavailable to users.

  • T4: Security Misconfiguration (Medium Severity):

    • Description: Incorrect configuration of "whoops" that weakens security.
    • Attack Vector: Failure to configure the blacklist, using an insecure editor configuration, or adding sensitive data to extraTables.
    • Impact: Increased risk of information disclosure or XSS.

  • T5: Dependency Vulnerabilities (Medium Severity):

    • Description: Vulnerabilities in "whoops" dependencies (managed by Composer).
    • Attack Vector: Exploitation of known vulnerabilities in outdated or compromised dependencies.
    • Impact: Varies depending on the specific vulnerability, but could range from information disclosure to remote code execution.

5. Mitigation Strategies (Actionable and Tailored to Whoops)

  • M1: Strict Configuration for Production Environments (Critical):

    • Action: Implement a "production" mode that disables the PrettyPageHandler entirely, or severely restricts its output. Use the JsonResponseHandler or PlainTextHandler instead, and configure them to display only a generic error message (e.g., "An unexpected error occurred"). Never display stack traces, request data, or environment variables in production.
    • Code Example (Conceptual): 
      if (getenv('APPLICATION_ENV') === 'production') {
    $whoops->clearHandlers();
    $whoops->pushHandler(function ($exception) {
        echo 'An unexpected error occurred. Please try again later.';
    });
}
    • Whoops Specific: This leverages the clearHandlers() and pushHandler() methods to completely control the output in production.

  • M2: Comprehensive Blacklisting (Critical):

    • Action: Use the $blacklist feature extensively to prevent sensitive data from being displayed in superglobals. Include at least the following:
      • $_ENV (all keys)
      • $_SERVER['DB_PASSWORD'] (and any other sensitive server variables)
      • $_COOKIE (all keys, or selectively blacklist sensitive cookies)
      • $_SESSION (all keys, or selectively blacklist sensitive session data)
      • $_POST (selectively blacklist sensitive POST data, if applicable)
    • Code Example: 
      $whoops->blacklist('_ENV', '*'); // Blacklist all environment variables
$whoops->blacklist('_SERVER', 'DB_PASSWORD');
$whoops->blacklist('_COOKIE', '*'); // Blacklist all cookies
    • Whoops Specific: This directly uses the blacklist() method provided by Whoops.

  • M3: Output Encoding and Sanitization (Critical):

    • Action: Ensure that all data displayed on the error page is properly encoded and sanitized to prevent XSS. This is particularly important for the PrettyPageHandler.
    • Code Example (Conceptual - within PrettyPageHandler): 
      // Instead of:
// echo "<div>" . $variable . "</div>";

// Use:
echo "<div>" . htmlspecialchars($variable, ENT_QUOTES, 'UTF-8') . "</div>";
    • Whoops Specific: This requires careful review and modification of the PrettyPageHandler's code to ensure that htmlspecialchars() (or equivalent) is used consistently. Consider using a templating engine with built-in output encoding.

  • M4: Limit Stack Trace Depth (Important):

    • Action: Limit the number of frames displayed in the stack trace, especially in production. This reduces the amount of potentially sensitive information exposed.
    • Code Example (Conceptual - within PrettyPageHandler): 
      $frames = $inspector->getFrames();
$frames = $frames->limit(10); // Limit to 10 frames
    • Whoops Specific: Use the FrameCollection::limit() method.

  • M5: Secure Editor Configuration (Important):

    • Action: If using the editor feature, ensure that the editor URL is properly sanitized to prevent XSS. Avoid using user-provided input to construct the editor URL.
    • Whoops Specific: Carefully review the $editor configuration option and the code that handles it.

  • M6: Regular Dependency Updates (Important):

    • Action: Use composer update regularly to update dependencies to their latest versions. Use a tool like composer audit (or a similar service) to check for known vulnerabilities in dependencies.
    • Whoops Specific: This is standard Composer best practice.

  • M7: Content Security Policy (CSP) (Important):

    • Action: Implement a strict CSP to mitigate the impact of potential XSS attacks. This should be done at the application level (not within "whoops" itself), but it's an important defense-in-depth measure.
    • Example CSP (Restrictive): 
      Content-Security-Policy: default-src 'self'; script-src 'none'; style-src 'self'; img-src 'self';
    • Whoops Specific: This is an application-level configuration, but it's highly relevant to "whoops" because it helps protect against XSS vulnerabilities in the error page.

  • M8: Avoid Displaying Sensitive Data in Exceptions (Important):

    • Action: Review the application code that uses "whoops" and ensure that exceptions do not contain sensitive data in their messages or other properties. Use generic error messages in production.
    • Whoops Specific: This is an application-level best practice, but it's crucial for preventing information disclosure through "whoops."

  • M9: Static Analysis (Recommended):

    • Action: Integrate static analysis tools (e.g., PHPStan, Psalm) into the development workflow to identify potential code quality and security issues.
    • Whoops Specific: This helps catch potential vulnerabilities early in the development process.

  • M10: Security Audits (Recommended):

    • Action: Conduct regular security audits of the "whoops" codebase and its integration with the application.
    • Whoops Specific: This helps identify vulnerabilities that might be missed by other methods.

  • M11: Disable filp/whoops in production (Strong Recommendation):

    • Action: The best way to secure filp/whoops in production is to disable it completely. Use a custom error handler that logs the error (with full details) to a secure location and displays a generic message to the user.
    • Whoops Specific: This is the most secure approach, as it eliminates the risk of information disclosure and XSS through Whoops.

This deep analysis provides a comprehensive overview of the security considerations for "whoops." The most critical vulnerabilities are information disclosure and XSS, and the mitigation strategies focus on preventing these through strict configuration, output encoding, blacklisting, and limiting the amount of data displayed. The strongest recommendation is to disable Whoops entirely in a production environment and replace it with a custom, minimal error handler.