SC-21 Secure Name/Address Resolution Service (Recursive or Caching Resolver)
Control
Request and perform data origin authentication and data integrity verification on the name/address resolution responses the system receives from authoritative sources.
Requirement:
Control description should include how DNSSEC is implemented on recursive DNS servers to make DNSSEC requests when resolving DNS requests from internal components to domains external to the CSO boundary.
- If the reply is signed, and fails DNSSEC, do not use the reply
- If the reply is unsigned: * CSP chooses the policy to apply
Requirement:
Internal recursive DNS servers must be located inside an authorized environment. It is typically within the boundary, or leveraged from an underlying IaaS/PaaS.
Guidance:
Accepting an unsigned reply is acceptable
Guidance:
SC-21 applies to use of internal recursive DNS to access a domain outside the boundary by a component inside the boundary.
- DNSSEC resolution to access a component inside the boundary is excluded.
Discussion
Each client of name resolution services either performs this validation on its own or has authenticated channels to trusted validation providers. Systems that provide name and address resolution services for local clients include recursive resolving or caching domain name system (DNS) servers. DNS client resolvers either perform validation of DNSSEC signatures, or clients use authenticated channels to recursive resolvers that perform such validations. Systems that use technologies other than the DNS to map between host and service names and network addresses provide some other means to enable clients to verify the authenticity and integrity of response data.
FedRAMP-Defined Assignment / Selection Parameters
N/A