Certificate Transparency (CT) information of DNS resolver

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Table of Contents

1. Background

DNS resolver can support any encrypted DNS scheme, such as DNS over HTTPS (DoH) [RFC8484], DNS over TLS (DoT) [RFC7858], or DNS over QUIC (DoQ) [RFC9250].¶

Certificate hijacking allows attackers to impersonate a legitimate encrypted DNS resolver, see also [MisIssuedCF].¶

Certificate Transparency (CT) is to combat the certificate hijacking issue [RFC9162]. This document describes the CT information of the encrypted DNS resolver.¶

2. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].¶

Basic terms used in this specification are defined in the documents [RFC1034], [RFC1035], [RFC9499], [RFC9606], [RFC9162].¶

3. IANA Considerations

4. Security Considerations

DNS clients can get trustworthy DNS resolver information through DNSSEC query or out-of-band configuration.¶

Suppose the DNS clients find the CT value in the trustworthy DNS resolver information. In that case, they can mandate the CT validation in the encrypted communication channel setup process with the encrypted DNS resolver.¶

5. Acknowledgements

Thanks to all in the DNSOP mailing list.¶

6. References

Author's Address