Internet DRAFT - draft-pan-dnsop-explicit-forged-answer-signal
draft-pan-dnsop-explicit-forged-answer-signal
dnsop L. Pan
Internet-Draft 10 January 2024
Intended status: Informational
Expires: 13 July 2024
Explicit Forged Answer Signal
draft-pan-dnsop-explicit-forged-answer-signal-00
Abstract
This document describes that recursive resolver should give explict
signal in the forged answer.
Client could react more clearly based on the explict forged answer
signal, to protect user on security and privacy.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 13 July 2024.
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Table of Contents
1. Background and Motivation . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Attack Surface . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. HTTP Cookies Leakage . . . . . . . . . . . . . . . . . . 3
4. Explicit Forged Answer Signal . . . . . . . . . . . . . . . . 3
4.1. Format 1: Use Extended DNS Errors . . . . . . . . . . . . 3
4.2. Format 2: Use TXT RR . . . . . . . . . . . . . . . . . . 3
5. Client Reaction . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Reaction 1: Use DNSSEC . . . . . . . . . . . . . . . . . 4
5.2. Reaction 2: Change Recursive Resolver . . . . . . . . . . 4
5.3. Reaction 3: Stop Visit . . . . . . . . . . . . . . . . . 4
5.4. Reaction 4: Limited Visit . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
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].
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3. Attack Surface
Faked answer can avoid user to visit malicious website, however, it
may also increase the security and privacy risk.
3.1. HTTP Cookies Leakage
The HTTP cookies risk has been well discussed in [NXDamageControl]
and [NXDNSLies]. Furthermore, the risk is not only occured on
NXDOMAIN scenario, but also on other faked answer scenarios.
Imagine that user visits "abc.example.com" in browser.
Recursive resolver return a faked answer to browser.
Browser will visit the faked server, and leak the HTTP cookies in
"example.com" of the user to it.
With the leaked HTTP cookies, the faked server may pretend as the
user to visit "abc.example.com", result in user's security issue and
privacy leakage.
4. Explicit Forged Answer Signal
Recursive resolver should give explict forged answer signal to
client.
4.1. Format 1: Use Extended DNS Errors
[RFC8914] defined Extended DNS Errors (EDE) extension.
Recursive resolver could give the signal by include additional EDE
information in DNS response:
* INFO-Code is 4.
* EXTRA-TEXT is the specific scenario desciption, for example,
malware.
4.2. Format 2: Use TXT RR
[RFC1035] defined TXT RDATA format.
Recursive resolver could give the signal by include additional TXT RR
in DNS response, such as:
abc.example.com 300 IN A 1.2.3.4
abc.example.com 300 IN TXT "faked=malware"
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5. Client Reaction
Client could make its own reaction when it received an explict forged
answer signal from recursive resolver.
5.1. Reaction 1: Use DNSSEC
Client could make DNSSEC query by itself.
If the domain has deployed DNSSEC, the client could validate the
honest answer from authoritative server.
5.2. Reaction 2: Change Recursive Resolver
Client could change to another recursive resolver which is not lying.
5.3. Reaction 3: Stop Visit
Client could stop to visit on the website, since it knows that the
answer is faked.
5.4. Reaction 4: Limited Visit
Client could make limited visit on the website, prevent HTTP cookies
from being send to the faked server.
For example, browser should not send user's HTTP cookies to the faked
server, if it gets an explict faked answer signal in the DoH response
[RFC8484].
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.
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7. Acknowledgements
Thanks to all in the DNSOP mailing list.
8. References
8.1. Normative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>.
[RFC8914] Kumari, W., Hunt, E., Arends, R., Hardaker, W., and D.
Lawrence, "Extended DNS Errors", RFC 8914,
DOI 10.17487/RFC8914, October 2020,
<https://www.rfc-editor.org/info/rfc8914>.
8.2. Informative References
[DNSFirewall]
ISC, "Response Policy Zones (RPZ)", n.d.,
<https://www.isc.org/rpz/>.
[ISPRedirect]
Weber, J. L. R., "DNS Redirect Use by Service Providers",
n.d., <https://datatracker.ietf.org/doc/draft-livingood-
dns-redirect/>.
[LegalRedirect]
York, D., "Oups! French Government Mistakenly Blocks
Telegram Access for Millions", n.d.,
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<https://pulse.internetsociety.org/blog/oups-french-
government-mistakenly-blocks-telegram-access-for-
millions>.
[NXDamageControl]
Vixie, P., "What DNS Is Not", n.d.,
<https://queue.acm.org/detail.cfm?id=1647302>.
[NXDNSLies]
Huston, G., "NXDOMAIN?", n.d.,
<https://www.potaroo.net/ispcol/2009-12/nxdomain.pdf>.
[NXRedierct]
ISC, "NXDOMAIN Redirection Using DLZ in BIND 9.10 and
later", n.d., <https://kb.isc.org/docs/aa-01150>.
Author's Address
Lanlan Pan
Guangdong
China
Email: abbypan@gmail.com
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