Zone Transfer in Hanami with Api Keys

Zone Transfer in Hanami with Api Keys occurs when an API endpoint that relies on API key authentication for authorization also exposes a DNS zone transfer interface or equivalent data-export functionality without proper scope or ownership checks. In this context, API keys are often treated as a simple bearer credential, but if the endpoint permits fetching large resource record sets and does not enforce per-key authorization boundaries, an attacker who obtains or guesses a key can request zone data that should be restricted.

For example, an endpoint like /api/v1/dns/export might accept an Authorization: ApiKey <key> header and return full DNS records unless the implementation validates that the key’s associated tenant or scope matches the requested zone. If the API deserializes the key, looks up permissions incompletely, or trusts path parameters without verifying ownership, the unauthenticated (from a broader network perspective) attacker can perform a logical BOLA/IDOR by iterating zone identifiers and harvesting DNS records via the same API key mechanism.

Because middleBrick scans the unauthenticated attack surface, it can detect such endpoints during its parallel checks, including BOLA/IDOR and Property Authorization tests. When API keys are used without scoping the data exposure to the key’s tenant or role, the scan may flag data exposure and insufficient authorization findings. The presence of API keys does not inherently prevent zone data leakage; it changes the threat model from network perimeter bypass to token misuse or horizontal privilege escalation.

Real-world parallels include insecure zone transfer mechanisms in DNS servers and APIs that inadvertently map generic credentials to broad data sets. MiddleBrick’s checks for Data Exposure and Property Authorization highlight cases where zone-like record sets are returned without validating that the requesting API key is authorized for that specific zone, aligning with findings from improper Access Control (broken access control in OWASP API Top 10).

Remediation focuses on ensuring API keys are bound to a specific scope or tenant and that endpoints validate this binding before returning zone data. Below are concrete Hanami-style code examples that demonstrate scoping and validation.

First, define a method that resolves the key to an authorized scope and fails early if the requested zone is outside that scope:

# app/services/zone_authorization.rb
class ZoneAuthorization
  def initialize(api_key:, requested_zone:)
    @api_key = api_key
    @requested_zone = requested_zone
  end

  def authorized?
    owner&.has_zone?(@requested_zone)
  end

  private

  def owner
    @owner ||= ApiKeyOwner.find_by(api_key: @api_key)
  end
end

In your endpoint or use case, apply the authorization check before exporting records:

# app/use_cases/export_zone.rb
class ExportZone
  def initialize(api_key, zone_name)
    @api_key = api_key
    @zone_name = zone_name
  end

  def call
    return { error: 'unauthorized' }, 403 unless authorization.authorized?

    { records: zone_records(@zone_name) }
  end

  private

  def authorization
    @authorization ||= ZoneAuthorization.new(api_key: @api_key, requested_zone: @zone_name)
  end

  def zone_records(zone)
    # Fetch and return only the records for the authorized zone
    DnsRecord.where(zone: zone)
  end
end

Ensure your API key model or lookup includes tenant or scope information so that keys cannot act across tenants:

# app/models/api_key.rb
class ApiKey
  include Hanami::Entity

  attributes :id, :key, :tenant_id

  def owner
    TenantRepository.new.find(tenant_id)
  end
end

Additionally, apply rate limiting and monitoring on these endpoints, and require explicit opt-in for zone export functionality rather than broad wildcard permissions. middleBrick’s CLI can be used to verify that endpoints with API key protection do not leak data across tenants by running scans against staging environments via the middlebrick scan <url> command and reviewing the returned findings.