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XCCDF
Microsoft Windows Server Domain Name System (DNS) Security Technical Implementation Guide
SRG-APP-000215-DNS-000026
Trust anchors must be exported from authoritative Windows DNS Servers and distributed to validating Windows DNS Servers.
Trust anchors must be exported from authoritative Windows DNS Servers and distributed to validating Windows DNS Servers.
An XCCDF Rule
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Trust anchors must be exported from authoritative Windows DNS Servers and distributed to validating Windows DNS Servers.
Medium Severity
<VulnDiscussion>If name server replies are invalid or cannot be validated, many networking functions and communication would be adversely affected. With DNS, the presence of Delegation Signer (DS) records associated with child zones informs clients of the security status of child zones. These records are crucial to the DNSSEC chain of trust model. Each parent domain's DS record is used to verify the DNSKEY record in its sub domain, from the top of the DNS hierarchy down. A DNS server is an example of an information system providing name/address resolution service. Digital signatures and cryptographic keys are examples of additional artifacts. DNS resource records are examples of authoritative data. Applications other than the DNS, to map between host/service names and network addresses, must provide other means to assure the authenticity and integrity of response data. DNSSEC provides the means to verify integrity assurances for the host/service name to network address resolution information obtained through the service. By using the DS Resource Records (RRs) in the DNS, the security status of a child domain can be validated. The DS RR is used to identify the DNSSEC signing key of a delegated zone. Starting from a trusted name server (such as the root name server) and down to the current source of response through successive verifications of signature of the public key of a child by its parent, the chain of trust is established. The public key of the trusted name servers is called the trust anchor. After authenticating the source, the next process DNSSEC calls for is to authenticate the response. This requires that responses consist of not only the requested RRs but also an authenticator associated with them. In DNSSEC, this authenticator is the digital signature of an RRSet. The digital signature of an RRSet is encapsulated through a special RRType called RRSIG. The DNS client using the trusted public key of the source (whose trust has just been established) then verifies the digital signature to detect if the response is valid or bogus. This control enables the DNS to obtain origin authentication and integrity verification assurances for the host/service name to network address resolution information obtained through the service. Without indication of the security status of a child domain and enabling verification of a chain of trust, integrity and availability of the DNS infrastructure cannot be assured. A trust anchor is a preconfigured public key associated with a specific zone. A validating DNS server must be configured with one or more trust anchors to perform validation. If the DNS server is running on a domain controller, trust anchors are stored in the forest directory partition in Active Directory Domain Services (AD DS) and can be replicated to all domain controllers in the forest. On standalone DNS servers, trust anchors are stored in a file named "TrustAnchors.dns". A DNS server running Windows Server also displays configured trust anchors in the DNS Manager console tree in the Trust Points container. Trust anchors can also be viewed by executing Windows PowerShell commands or "Dnscmd.exe" at a Windows command prompt.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>