Explicit Forged Answer Signal

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Table of Contents

1. Background and Motivation

Recursive server may replace a forged answer to a query with a configured answer of the authoritative server in some specific scenarios, such as NXDOMAIN, phishing, fraud, malware, ransomware, botnet DDoS attack, and legal requirement, etc. See also [NXRedierct] [ISPRedirect] [DNSFirewall] [LegalRedirect].¶

The RCODE of faked answer is NOERROR, which make client hard to distinguish it with honest answer, if client doesn't make iterative dns query by itself, or make DNSSEC validation.¶

At least, the client has the right to know that it has received a forged answer and it could make clearer reaction by itself.¶

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], [RFC8499].¶

• Authoritative Server: Described in [RFC8499].¶

• Recursive Resolver: Described in [RFC8499].¶

3. Attack Surface

Faked answer can avoid user to visit malicious website, however, it may also increase the security and privacy risk.¶

4. Explicit Forged Answer Signal

Recursive resolver should give explict forged answer signal to client.¶

abc.example.com  300 IN  A  1.2.3.4
abc.example.com  300 IN  TXT  "faked=malware"

5. Client Reaction

Client could make its own reaction when it received an explict forged answer signal from recursive resolver.¶

6. Security Considerations

Faked answer is unauthenticated by authoritative server, just offered by recursive resolver on some specific scenarios.¶

Ideally, with the DNSSEC deployed on second level domain, client would not trust any faked answer if it makes all RRSIG validation by itself.¶

Explicit faked answer signal is to help client to make clearer reaction on faked answer, with the help of recursive resolver.¶

As a trade-off, explict faked answer signal could help browser to mitigate the http cookies leaked to faked server, protect user security and privacy in conditional limited environment.¶

7. Acknowledgements

Thanks to all in the DNSOP mailing list.¶

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