draft-ietf-dnsext-ad-is-secure-02.txt   draft-ietf-dnsext-ad-is-secure-03.txt 
DNSEXT Working Group Brian Wellington DNSEXT Working Group Brian Wellington
INTERNET-DRAFT Olafur Gudmundsson INTERNET-DRAFT Olafur Gudmundsson
<draft-ietf-dnsext-ad-is-secure-02.txt> June 2001 <draft-ietf-dnsext-ad-is-secure-03.txt> July 2001
Updates: RFC 2535 Updates: RFC 2535
Redefinition of DNS AD bit Redefinition of DNS AD bit
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
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The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html http://www.ietf.org/shadow.html
Comments should be sent to the authors or the DNSEXT WG mailing list Comments should be sent to the authors or the DNSEXT WG mailing list
namedroppers@ops.ietf.org namedroppers@ops.ietf.org
This draft expires on December 18, 2001. This draft expires on January 17, 2002.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2001). All rights reserved. Copyright (C) The Internet Society (2001). All rights reserved.
Abstract Abstract
Based on implementation experience, the current definition of the AD Based on implementation experience, the current definition of the AD
bit in the DNS header is not useful. This draft changes the bit in the DNS header is not useful. This draft changes the
specification so that the AD bit is only set on answers where specification so that the AD bit is only set on answers where
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As specified in RFC 2535 (section 6.1), the AD bit indicates in a As specified in RFC 2535 (section 6.1), the AD bit indicates in a
response that all the data included in the answer and authority response that all the data included in the answer and authority
portion of the response has been authenticated by the server portion of the response has been authenticated by the server
according to the policies of that server. This is not especially according to the policies of that server. This is not especially
useful in practice, since a conformant server should never reply with useful in practice, since a conformant server should never reply with
data that failed its security policy. data that failed its security policy.
This draft proposes to redefine the AD bit such that it is only set This draft proposes to redefine the AD bit such that it is only set
if all data in the response has been cryptographically verified. if all data in the response has been cryptographically verified.
Thus, a response containing properly delegated insecure data will not Thus, a response containing properly delegated insecure data will not
have AD set, as will a response from a server configured without have AD set, neither will a response from a server configured without
DNSSEC keys. As before, data which failed to verify will not be DNSSEC keys. As before, data which failed to verify will not be
returned. An application can then use the value of the AD bit to returned. An application can then use the value of the AD bit to
determine if the data is secure or not. determine if the data is secure or not.
1.1 - Requirements 1.1 - Requirements
The key words "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" in this The key words "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" in this
document are to be interpreted as described in RFC2119. document are to be interpreted as described in RFC2119.
1.2 - Updated documents and sections 1.2 - Updated documents and sections
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the answer and authority sections of the response are either the answer and authority sections of the response are either
Authenticated or Insecure." Authenticated or Insecure."
The changes are to delete the words "either" and "or Insecure" from The changes are to delete the words "either" and "or Insecure" from
the sentence. the sentence.
The replacement text reads: The replacement text reads:
"The AD bit MUST NOT be set on a response unless all of the RRsets in "The AD bit MUST NOT be set on a response unless all of the RRsets in
the answer and authority sections of the response are Authenticated." the answer and authority sections of the response are Authenticated."
"The AD bit SHOULD be set if and only if all RRs in the answer
section and any relevant negative response RRs in that authority
section are Authenticated."
AD should be set if and only if all RRs in the answer section, and AD should be set if and only if all RRs in the answer section, and
any relevant negative response RRs in the authority section are any relevant negative response RRs in the authority section are
Authenticated. Authenticated.
The AD bit MUST NOT be set on a response unless all of the RRsets in The AD bit MUST NOT be set on a response unless all of the RRsets in
the answer and authority sections are Authenticated. the answer and authority sections are Authenticated.
A resolver MUST NOT blindly trust the AD bit unless it communicates A resolver MUST NOT blindly trust the AD bit unless it communicates
with the server over secure transport mechanism or using message with the server over secure transport mechanism or using message
authentication such as TSIG[RFC2845] or SIG(0)[RFC2931], and the authentication such as TSIG[RFC2845] or SIG(0)[RFC2931], and the
resolver policy is that it can trust the server. resolver policy is that it can trust the server.
A DNS server following this modified specification will only set the Any DNS server supporting the OK bit MUST support this definition of
AD bit when it has cryptographically verified the data in the answer. the AD bit. A DNS server following this modified specification will
In the case of a primary server for a secure zone, the data MAY be only set the AD bit when it has cryptographically verified the data
considered Authenticated, depending on local policy. Secondary in the answer. In the case of a primary server for a secure zone,
servers SHOULD NOT consider data Authenticated unless the zone was the data MAY be considered Authenticated, depending on local policy.
transfered securely or the data was verified. Secondary servers SHOULD NOT consider data Authenticated unless the
zone was transfered securely or the data was verified.
3 - Interpretation of the AD bit 3 - Interpretation of the AD bit
A response containing data marked Insecure in the answer or authority A response containing data marked Insecure in the answer or authority
section will never have the AD bit set. In this case, the resolver section will never have the AD bit set. In this case, the resolver
SHOULD treat the data as Insecure whether or not SIG records are SHOULD treat the data as Insecure whether or not SIG records are
present. present.
4 - Security Considerations: 4 - Security Considerations:
This document redefines a bit in the DNS header. If a resolver This document redefines a bit in the DNS header. If a resolver
trusts the value of the AD bit, it must be sure that the server is trusts the value of the AD bit, it must be sure that the server is
using the updated definition. using the updated definition, which is any server supporting the OK
bit.
5 - IANA Considerations: 5 - IANA Considerations:
None None
6 - Acknowledgments: 6 - Acknowledgments:
The following people have provided input on this document: Andreas The following people have provided input on this document: Andreas
Gustafsson, Bob Halley, Steven Jacob. Gustafsson, Bob Halley, Steven Jacob.
 End of changes. 

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