Internet DRAFT - draft-krecicki-dnsenc
draft-krecicki-dnsenc
Internet Engineering Task Force W. Krecicki
Internet-Draft Internet Systems Consortium
Intended status: Standards Track September 30, 2015
Expires: April 2, 2016
Stateless DNS Encryption
draft-krecicki-dnsenc-00
Abstract
The DNS is the last common Internet protocol that has no encryption
scheme and therefore provides no privacy to the users. This document
proposes an extensible mechanism providing encryption of DNS queries
and responses with method for secure retrieval and verification of
validity of encryption keys. It is independent of the underlying
transport protocol.
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 April 2, 2016.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Communication process . . . . . . . . . . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . 3
4. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Normative References . . . . . . . . . . . . . . . . . . 4
4.2. Informative References . . . . . . . . . . . . . . . . . 4
Appendix A. Additional Stuff . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
The Domain Name System protocol is specified in RFC 1034 [RFC1034]
and RFC 1035" [RFC1035]. DNS messages are unencrypted and therefore
prone to eavesdropping. Although it's considered only metadata, the
are a lot of data that can be leaked - from simply domain names of
visited sites, to eg phone numbers (RFC 3761 [RFC3761]) or e-mail
addresses (draft-ietf-dane-smime-08 [I-D.ietf-dane-smime]).
The DNS protocol is very lightweight - the queries are usually < 100
bytes long, the responses are usually < 1000 bytes (with DNSSEC).
Existing transport encryption schemes such as TLS for TCP or DTLS for
UDP give huge and unnecessary overhead both in amount of data sent
and retrieved and in number of packets exchanged between client and
server.
In DNSENC the query is encrypted using asymmetric cryptography with a
securely retrieved key, the response is encrypted using symmetric
encryption using one-time key provided with query. DNSENC protocol
is confined within DNS and does not requires any additional external
mechanism such as external PKI/CA system.
The DNSENC communication can be split into three phases:
o first the client retrieves public key for server that is stored in
DNS and DNSSEC signed (this key can be cached)
o client creates the query, adds a random response encryption key
and encrypts the query with servers public key
o server decrypts the message, prepares the response and encrypts it
with the key provided by client
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1.1. Requirements Language
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 RFC 2119 [RFC2119].
2. Communication process
To communicate securely with server, client first needs to retrieve
servers public key for assymetric encryption. This key is stored in
DNSEK record for reverse DNS record IP address of DNS server, as
described in RFC3152, 1033, 2317. This record MUST be DNSSEC signed.
TODO alternative method - DNSEK kept by NS record
Each DNSEK RR consist of priority field, key identifier, query
encryption scheme (asymmetrical, eg. RSA), query key data and
possible response encryption schemes. The server might provide
multiple RR records, it's client responsibility to choose a RRR that
has query and response encryption schemes supported by client and has
highest priority.
After choosin encryption scheme client generates a random response
encryption key (symmetrical, eg. AES), prepares a regular DNS query
with DNSEK record containing the response encryption scheme and key
in ADDITIONAL section. This message is encrypted using query
encryption key and packed, along with encryption key ID, in a DNSENC
RR. A new query is created with query id copied from the encrypted
message, empty QUESTION (TODO or put something there?), ANSWER and
AUTHORITY sections and with DNSENC RR in ADDITIONAL section and sent
to server. The response encryption key is stored along its
identifier for decryption.
After receiving the query with DNSENC RR in ADDITIONAL section the
server checks if it has proper key and decrypts the message. A
regular DNS response packet is created, it is encrypted using
response encryption key sent by client and stored along with response
encryption key ID in DNSENC RR. New response packet with query ID
copied from the encrypted one is created with empty QUESTION, ANSWER
(TODO?) and AUTHORITY sections and with DNSENC RR in ADDITIONAL
section. This response packet is sent to the client.
3. Security Considerations
The security of this protocol is based deeply on DNSSEC [RFC4033].
Protection agains downgrade attack requires wide adoption of DNSSEC.
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4. References
4.1. Normative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<http://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <http://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,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", RFC
4033, DOI 10.17487/RFC4033, March 2005,
<http://www.rfc-editor.org/info/rfc4033>.
4.2. Informative References
[I-D.ietf-dane-smime]
Hoffman, P. and J. Schlyter, "Using Secure DNS to
Associate Certificates with Domain Names For S/MIME",
draft-ietf-dane-smime-08 (work in progress), February
2015.
[RFC3761] Faltstrom, P. and M. Mealling, "The E.164 to Uniform
Resource Identifiers (URI) Dynamic Delegation Discovery
System (DDDS) Application (ENUM)", RFC 3761, DOI 10.17487/
RFC3761, April 2004,
<http://www.rfc-editor.org/info/rfc3761>.
Appendix A. Additional Stuff
This becomes an Appendix.
Author's Address
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Witold Krecicki
Internet Systems Consortium
Warsaw
PL
Phone: +48 502117580
Email: wpk@isc.org
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