Zone Transfer in Hanami with Dynamodb

In Hanami applications that use Dynamodb as the persistence layer, a zone transfer misconfiguration can expose internal DNS or service metadata to unauthenticated endpoints. This occurs when endpoint definitions or route mappings inadvertently reveal how internal services resolve to Dynamodb table names or ARNs. middleBrick scans the unauthenticated attack surface and flags this as a BOLA/IDOR or Property Authorization finding when endpoint introspection returns data that should be restricted.

During a scan, middleBrick checks whether API responses include Dynamodb-specific identifiers such as table ARNs or global secondary index names that should not be disclosed. If an endpoint returns a full Dynamodb resource description without proper authorization, this becomes an information exposure vector. The scanner cross-references the OpenAPI specification against runtime behavior, detecting cases where $ref entries for Dynamodb structures are overly permissive.

For example, an endpoint like /api/v1/users/:id might internally reference a Dynamodb table name derived from the environment. If the API response includes this table name or related metadata, an attacker can map internal AWS resources without credentials. middleBrick’s LLM/AI Security checks further detect whether prompts or responses leak system patterns that could be abused to infer Dynamodb naming conventions.

Real-world patterns include hardcoded table names in Hanami entity definitions that are serialized into JSON responses. If combined with insufficient input validation, this can enable enumeration attacks where attackers iterate through known table prefixes. The scanner’s BFLA/Privilege Escalation checks look for endpoints that allow modifying query parameters to access adjacent data zones.

middleBrick connects these findings to compliance frameworks such as OWASP API Top 10 and SOC2, noting that exposed Dynamodb identifiers can lead to further compromise if AWS credentials are accidentally leaked elsewhere. The scanner does not fix these issues but provides prioritized findings with remediation guidance, emphasizing the need to treat Dynamodb metadata as sensitive.

To remediate zone transfer risks in Hanami with Dynamodb, ensure that API responses never expose table names, ARNs, or internal indexing details. Use abstraction layers that map logical entity names to Dynamodb resources without revealing the mapping in payloads.

Example of a vulnerable Hanami entity that leaks the Dynamodb table name:

module Entities
  class User
    include Hanami::Entity

    attribute :id, Types::Strict::String
    attribute :table_name, Types::Strict::String

    def initialize(attributes = {})
      super(attributes.merge(table_name: ENV['DYNAMODB_TABLE']))
    end
  end
end

Safer approach using a dedicated mapping that keeps table names internal:

module Repositories
  class UserRepository
    TABLE_NAME = ENV.fetch('DYNAMODB_TABLE')

    def find(id)
      response = dynamodb_client.get_item(
        table_name: TABLE_NAME,
        key: { id: { s: id } }
      )
      UserEntity.new(response.item.except('table_name'))
    end
  end
end

In the API endpoint, ensure only necessary attributes are serialized:

module API
  class Users::Show
    def call(params)
      user = UserRepository.new.find(params[:id])
      Presenters::User.new(user).serialize # excludes internal metadata
    end
  end
end

For middleware handling Dynamodb errors, avoid returning raw AWS error messages that might include table or index names:

module Errors
  class DynamodbErrorHandler
    def call(error, env)
      { 'error' => 'request_failed' }
    end
  end
end

middleBrick’s dashboard helps track these changes over time, while the CLI can validate that no sensitive metadata appears in JSON output. The GitHub Action can enforce that any merge affecting entity definitions passes security checks before deployment.