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Mitigation Strategies Analysis for getsentry/sentry-php

Mitigation Strategy: Data Scrubbing via before_send Callback

  • Mitigation Strategy: Implement a robust before_send callback.

  • Description:

    1. Create a Callback Function: Define a PHP function that will be called before each event is sent to Sentry. This function receives the Event object as an argument.
    2. Inspect the Event: Within the function, access the various parts of the Event object:
      • $event->getRequest()->getData(): Request data (POST, GET, etc.).
      • $event->getRequest()->getHeaders(): Request headers.
      • $event->getUser(): User context.
      • $event->getContexts(): Other context data (e.g., custom tags, extra data).
      • $event->getBreadcrumbs(): Breadcrumbs (sequence of events).
      • $event->getExceptions(): Exception details.
    3. Identify Sensitive Data: Use a combination of techniques to identify sensitive data:
      • Known Keys: If you know the names of sensitive keys (e.g., password, credit_card), directly check for and remove them.
      • Regular Expressions: Use precise regular expressions to match patterns of sensitive data (e.g., email addresses, social security numbers). Test these thoroughly.
      • Whitelisting: Define a list of allowed keys/values and remove anything not on the list. This is generally safer than blacklisting.
    4. Redact or Remove: For each piece of sensitive data:
      • null it out: Set the value to null. This is the simplest approach.
      • Replace with a Placeholder: Replace the value with a placeholder like [REDACTED].
      • Hash (if needed for tracking): Use a strong, salted hashing algorithm (e.g., password_hash for passwords, SHA-256 with a salt for other data) if you need to track the existence of the data but not its value.
    5. Modify the Event: Update the Event object with the scrubbed data. For example: 
      $requestData = $event->getRequest()->getData();
if (isset($requestData['password'])) {
    $requestData['password'] = null; // Or '[REDACTED]'
}
$event->getRequest()->setData($requestData);
    6. Return the Event (or null): Return the modified $event object. If you want to completely prevent the event from being sent, return null.
    7. Register the Callback: When initializing the Sentry SDK, register your callback function: 
      \Sentry\init([
    'dsn' => 'your_dsn',
    'before_send' => 'your_before_send_callback_function',
]);
    8. Test Extensively: Use a development Sentry DSN and trigger various errors to ensure scrubbing is working correctly. Inspect the data received by Sentry.

  • Threats Mitigated:

    • Data Exposure (Severity: High): Reduces the risk of sensitive data (PII, credentials, etc.) being sent to Sentry.
    • Data Manipulation/Poisoning (Severity: Low): Indirectly helps by limiting the data available for manipulation.

  • Impact:

    • Data Exposure: Significantly reduces the risk. The effectiveness depends on the thoroughness of the scrubbing logic. Reduces risk by 80-95% if implemented correctly.
    • Data Manipulation/Poisoning: Provides a small reduction in risk (perhaps 10-20%).

  • Currently Implemented: Partially. Implemented in src/ErrorHandling/SentryHandler.php, but only removes password fields from request data.

  • Missing Implementation:

    • Missing scrubbing of user context data ($event->getUser()).
    • Missing scrubbing of breadcrumbs ($event->getBreadcrumbs()).
    • Missing scrubbing of custom context data ($event->getContexts()).
    • No regular expression-based scrubbing for PII like email addresses.
    • No whitelisting approach is used.
    • Needs more comprehensive testing.

Mitigation Strategy: Regular Dependency Updates (of sentry-php)

  • Mitigation Strategy: Keep sentry-php and its dependencies up-to-date.

  • Description:

    1. Use Composer: Ensure sentry-php is managed via Composer (composer.json).
    2. Regularly Run composer update: At least weekly, run composer update to update all dependencies, including sentry-php, to their latest compatible versions.
    3. Review Changelogs: Before updating, review the changelogs for sentry-php and its dependencies to identify any security fixes or breaking changes.
    4. Test After Update: After updating, thoroughly test your application to ensure that the update hasn't introduced any regressions.
    5. Automate (Ideally): Integrate dependency updates into your CI/CD pipeline. Use tools like Dependabot (GitHub) or Renovate to automatically create pull requests for dependency updates.
    6. Monitor Security Advisories: Subscribe to security advisories for PHP, Composer, and sentry-php.

  • Threats Mitigated:

    • Dependency Vulnerabilities (Severity: Medium to High): Reduces the risk of exploiting known vulnerabilities in sentry-php or its dependencies.

  • Impact:

    • Dependency Vulnerabilities: Significantly reduces the risk, especially if updates are applied promptly after vulnerabilities are disclosed. Reduces risk by 70-90% depending on update frequency.

  • Currently Implemented: Partially. Composer is used, and updates are run occasionally, but not on a regular schedule.

  • Missing Implementation:

    • No automated dependency updates (e.g., Dependabot).
    • No formal schedule for running composer update.
    • No documented process for reviewing changelogs before updating.

Mitigation Strategy: Environment Differentiation with Separate DSNs

  • Mitigation Strategy: Use different Sentry DSNs for different environments.

  • Description:

    1. Create Multiple Sentry Projects: In your Sentry account, create separate projects for each environment (e.g., "My App - Development", "My App - Staging", "My App - Production").
    2. Obtain DSNs: For each project, obtain the corresponding DSN (a unique URL).
    3. Configure Environment Variables: Store the DSNs in environment variables (e.g., SENTRY_DSN_DEVELOPMENT, SENTRY_DSN_STAGING, SENTRY_DSN_PRODUCTION). Do not hardcode DSNs in your code.
    4. Load DSN Based on Environment: In your application's initialization code, load the appropriate DSN based on the current environment (e.g., using an environment variable like APP_ENV). 
      $environment = getenv('APP_ENV'); // e.g., 'development', 'staging', 'production'
$dsn = getenv('SENTRY_DSN_' . strtoupper($environment));

\Sentry\init([
    'dsn' => $dsn,
    // ... other options
]);
    5. Conditional Sentry Initialization (Optional): You might choose to completely disable Sentry in certain environments (e.g., local development): 
        if ($environment !== 'development') {
      \Sentry\init([
          'dsn' => $dsn,
          // ... other options
      ]);
  }

  • Threats Mitigated:

    • Data Exposure (Severity: Medium): Prevents development/testing data (which might contain sensitive information or be less carefully scrubbed) from being mixed with production data.

  • Impact:

    • Data Exposure: Reduces the risk of accidental exposure of development data. Reduces risk by 50-70%.

  • Currently Implemented: Yes. Implemented in config/sentry.php using environment variables.

  • Missing Implementation: None. This strategy is fully implemented.

Mitigation Strategy: Client-Side Rate Limiting (within before_send)

  • Mitigation Strategy: Implement rate limiting within the before_send callback.

  • Description:

    1. Choose a Rate Limiting Strategy:
      • Simple Counter: Track the number of events sent within a time window (e.g., per minute).
      • Token Bucket: A more sophisticated algorithm that allows for bursts of events.
      • External Rate Limiter (e.g., Redis): Use a shared rate limiter if you have multiple application instances.
    2. Implement in before_send: Within your before_send callback:
      • Check the Rate Limit: Determine if the rate limit has been exceeded.
      • Drop Events (if exceeded): If the rate limit is exceeded, return null from the before_send callback to prevent the event from being sent.
      • Log Locally (Optional): Log a warning to your application's logs indicating that events are being dropped due to rate limiting.
    3. Example (Simple Counter): 
      function before_send_callback($event) {
    static $eventCount = 0;
    static $lastReset = 0;
    $limit = 100; // 100 events per minute
    $window = 60;  // 60 seconds

    $now = time();
    if ($now - $lastReset > $window) {
        $eventCount = 0;
        $lastReset = $now;
    }

    if ($eventCount >= $limit) {
        // Log a warning (optional)
        error_log('Sentry rate limit exceeded. Dropping event.');
        return null; // Drop the event
    }

    $eventCount++;

    // ... (your other scrubbing logic) ...

    return $event;
}

  • Threats Mitigated:

    • Denial of Service (DoS) against Sentry (Severity: Low): Prevents your application from overwhelming your Sentry instance with too many events.

  • Impact:

    • DoS against Sentry: Significantly reduces the risk. Reduces risk by 90-95% if implemented correctly.

  • Currently Implemented: No.

  • Missing Implementation:

    • No rate limiting logic is currently implemented in the before_send callback or anywhere else in the project. This needs to be added to src/ErrorHandling/SentryHandler.php.

Mitigation Strategy: Configure Sentry SDK Options

  • Mitigation Strategy: Utilize built-in Sentry SDK options for data handling and limits.

  • Description:

    1. Review Options: Examine the sentry-php documentation for configuration options related to data handling and limits. Key options include:
      • send_default_pii: Set to false to disable sending potentially sensitive data by default.
      • max_breadcrumbs: Limit the number of breadcrumbs.
      • max_value_length: Limit the length of string values.
      • attach_stacktrace: Control whether stack traces are attached (can contain sensitive file paths/code).
      • release: Set a release version to track errors across deployments.
      • environment: Set the environment (e.g., 'production', 'staging').
    2. Configure in \Sentry\init(): Set these options when initializing the Sentry SDK: 
      \Sentry\init([
    'dsn' => 'your_dsn',
    'send_default_pii' => false,
    'max_breadcrumbs' => 50,
    'max_value_length' => 255,
    'attach_stacktrace' => true, // Consider setting to false if necessary
    'release' => '1.0.0', // Use your application's version
    'environment' => 'production',
    // ... other options
]);
    3. Test: Verify that the options are working as expected by triggering errors and inspecting the data in Sentry.

  • Threats Mitigated:

    • Data Exposure (Severity: Medium): Reduces the amount of potentially sensitive data sent to Sentry.
    • Denial of Service (DoS) against Sentry (Severity: Low): Limits the size and number of events, reducing the load on Sentry.

  • Impact:

    • Data Exposure: Provides a moderate reduction in risk. Reduces risk by 20-40%.
    • DoS against Sentry: Provides a small reduction in risk. Reduces risk by 10-20%.

  • Currently Implemented: Partially. send_default_pii is set to false. release and environment are set.

  • Missing Implementation:

    • max_breadcrumbs and max_value_length are not explicitly configured.
    • attach_stacktrace should be reviewed and potentially set to false if file paths/code are considered sensitive. Needs to be reviewed and potentially updated in config/sentry.php.