mitigations.md

Mitigation Strategies Analysis for bettererrors/better_errors

Mitigation Strategy: Conditional Loading via Gemfile

• Mitigation Strategy: Conditional Loading via Gemfile

  • Description:

    1. Open the project's Gemfile.
    2. Locate the better_errors and binding_of_caller gem declarations.
    3. Ensure these gems are only included within a group :development do ... end block. If they are outside this block, move them inside.
    4. Run bundle install to update the project's dependencies.
    5. Verify that running bundle show better_errors in a production environment (e.g., by setting RAILS_ENV=production) results in an error, indicating the gem is not installed.

  • Threats Mitigated:

    • Threat: Accidental Deployment of better_errors to Production.
      • Severity: Critical. Exposes full application source code, environment variables, and allows arbitrary code execution.
    • Threat: Unintentional Exposure in Staging/Testing Environments.
      • Severity: High. Similar risks to production, though potentially with a smaller attack surface.

  • Impact:

    • Accidental Deployment: Risk reduced from Critical to Negligible (assuming proper deployment procedures). The gem is simply not present in the production environment.
    • Unintentional Exposure: Risk reduced significantly, as the gem is only available in the development environment. Further mitigation (IP whitelisting) is still recommended for staging.

  • Currently Implemented: Yes. Gemfile correctly uses the :development group.

  • Missing Implementation: None. This is a fundamental and correctly implemented step.

Mitigation Strategy: IP Address Whitelisting (Staging/Testing Only)

• Mitigation Strategy: IP Address Whitelisting (Staging/Testing Only)

  • Description:

    1. Identify the IP addresses or CIDR blocks of authorized developers/testers who need access to better_errors in staging.
    2. Create or modify the configuration file for the staging environment (e.g., config/environments/staging.rb).
    3. Add the following line, replacing the example IPs with your authorized IPs/CIDR blocks:

       BetterErrors.allowed_ip_addresses = ['192.168.1.100', '10.0.0.5', '192.168.2.0/24']

    4. Restart the application server in the staging environment.
    5. Test access from both allowed and disallowed IP addresses to confirm the restriction is working.

  • Threats Mitigated:

    • Threat: Unauthorized Access to Debugger in Staging.
      • Severity: High. Attackers could gain access to sensitive information and potentially execute code.
    • Threat: Exploitation via Compromised Internal Machine.
      • Severity: Medium. If an attacker compromises a machine within the allowed IP range, they could still access the debugger.

  • Impact:

    • Unauthorized Access: Risk significantly reduced. Only requests originating from the whitelisted IPs can access the debugger.
    • Compromised Internal Machine: Risk remains, but the attack surface is limited to the whitelisted IPs. Further mitigation (disabling REPL) is recommended.

  • Currently Implemented: Partially. config/environments/staging.rb includes an allowed_ip_addresses setting, but it currently allows all IPs (0.0.0.0/0).

  • Missing Implementation: The allowed_ip_addresses setting in config/environments/staging.rb needs to be updated with the correct, restrictive IP addresses/CIDR blocks.

Mitigation Strategy: Environment Variable Control

• Mitigation Strategy: Environment Variable Control

  • Description:

    1. Modify the development environment configuration file (e.g., config/environments/development.rb).
    2. Wrap the better_errors configuration within a conditional block that checks for an environment variable:

       if ENV['ENABLE_BETTER_ERRORS'] == 'true'
         # BetterErrors configuration here (e.g., maximum_variable_inspect_size)
       end

    3. Developers must explicitly set the ENABLE_BETTER_ERRORS environment variable to true (e.g., in their shell or .env file) to enable better_errors.
    4. Test by running the application with and without the environment variable set, verifying that better_errors is only active when the variable is true.

  • Threats Mitigated:

    • Threat: Accidental Activation in Development.
      • Severity: Medium. Reduces the chance of developers inadvertently leaving better_errors active when not actively debugging.
    • Threat: Unauthorized Local Access.
      • Severity: Low. If someone gains unauthorized access to a developer's machine, they would still need to know to set the environment variable.

  • Impact:

    • Accidental Activation: Risk reduced. better_errors is only active when explicitly enabled.
    • Unauthorized Local Access: Provides a small additional layer of security, but is not a primary defense.

  • Currently Implemented: No. better_errors is always active in the development environment.

  • Missing Implementation: The conditional block based on ENV['ENABLE_BETTER_ERRORS'] needs to be added to config/environments/development.rb.

Mitigation Strategy: Limit Variable Inspection Size and Frame Depth

• Mitigation Strategy: Limit Variable Inspection Size and Frame Depth

  • Description:

    1. Locate the better_errors configuration (likely in config/environments/development.rb or a dedicated initializer).
    2. Add or modify the following settings:

       BetterErrors.maximum_variable_inspect_size = 100000  # Example: 100KB
       BetterErrors.maximum_frames_to_inspect = 10       # Example: 10 frames

       Adjust the values as appropriate for your application, balancing debugging needs with security.
    3. Restart the application server.
    4. Test by triggering an error and inspecting variables/stack frames to ensure the limits are enforced.

  • Threats Mitigated:

    • Threat: Information Disclosure (Large Variables).
      • Severity: Medium. Limits the amount of data exposed if an attacker gains access to the debugger.
    • Threat: Information Disclosure (Deep Stack Traces).
      • Severity: Medium. Reduces the amount of code execution context revealed.
    • Threat: Denial of Service (Resource Exhaustion).
      • Severity: Low. Large variable inspection or deep stack traces could potentially consume excessive resources.

  • Impact:

    • Information Disclosure: Risk reduced by limiting the data exposed.
    • Denial of Service: Risk reduced by limiting resource consumption.

  • Currently Implemented: Partially. BetterErrors.maximum_frames_to_inspect is set to 15. BetterErrors.maximum_variable_inspect_size is not set.

  • Missing Implementation: BetterErrors.maximum_variable_inspect_size needs to be set in the configuration. BetterErrors.maximum_frames_to_inspect should be reviewed and potentially lowered.

Mitigation Strategy: Disable REPL in Sensitive Environments (Staging)

• Mitigation Strategy: Disable REPL in Sensitive Environments (Staging)

  • Description:

    1. Open the staging environment configuration file (e.g., config/environments/staging.rb).
    2. Add the following lines:

       BetterErrors.allow_remote_requests = false
       BetterErrors::Middleware.allow_ip! '127.0.0.1'
       BetterErrors::Middleware.allow_ip! '::1'

    3. Restart the application server in the staging environment.
    4. Attempt to access the REPL functionality (if previously accessible) to confirm it is disabled.

  • Threats Mitigated:

    • Threat: Arbitrary Code Execution via REPL.
      • Severity: Critical. Prevents attackers from executing arbitrary code on the server, even if they bypass IP whitelisting.

  • Impact:

    • Arbitrary Code Execution: Risk eliminated. The REPL is completely disabled.

  • Currently Implemented: No. The REPL is potentially accessible in staging (depending on IP whitelisting).

  • Missing Implementation: The lines to disable allow_remote_requests and restrict to localhost need to be added to config/environments/staging.rb.