Internet X.509 Public Key Infrastructure Subject Alternative Name for Expression of Service Name
RFC 4985
Network Working Group S. Santesson
Request for Comments: 4985 Microsoft
Category: Standards Track August 2007
Internet X.509 Public Key Infrastructure
Subject Alternative Name for Expression of Service Name
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract
This document defines a new name form for inclusion in the otherName
field of an X.509 Subject Alternative Name extension that allows a
certificate subject to be associated with the service name and domain
name components of a DNS Service Resource Record.
Table of Contents
1. Introduction ....................................................2
1.1. Terminology ................................................2
2. Name Definitions ................................................2
3. Internationalized Domain Names ..................................4
4. Name Constraints Matching Rules .................................5
5. Security Considerations .........................................6
6. Normative References ............................................6
Appendix A. ASN.1 Syntax ...........................................7
Appendix A.1. 1988 ASN.1 Module .................................7
Appendix A.2. 1993 ASN.1 Module .................................8
Santesson Standards Track [Page 1]
RFC 4985 DNS SRV RR otherName August 2007
1. Introduction
This document specifies a name form for inclusion in X.509
certificates that may be used by a certificate relying party to
verify that a particular host is authorized to provide a specific
service within a domain.
RFC 2782 [N3] defines a DNS RR (Resource Record) for specifying the
location of services (SRV RR), which allows clients to ask for a
specific service/protocol for a specific domain and get back the
names of any available servers.
Existing name forms in X.509 certificates support authentication of a
host name. This is useful when the name of the host is known by the
client prior to authentication.
When a server host name is discovered through DNS RR lookup query
based on service name, the client may need to authenticate the
server's authorization to provide the requested service in addition
to the server's host name.
While DNS servers may have the capacity to provide trusted
information, there may be many other situations where the binding
between the name of the host and the provided service needs to be
supported by additional credentials.
Current dNSName GeneralName Subject Alternative name form only
provides for DNS host names to be expressed in "preferred name
syntax", as specified by RFC 1034 [N4]. This definition is therefore
not broad enough to allow expression of a service related to that
domain.
1.1. 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 RFC 2119 [N1].
2. Name Definitions
This section defines the SRVName name as a form of otherName from the
GeneralName structure in SubjectAltName defined in RFC 3280 [N2].
id-on-dnsSRV OBJECT IDENTIFIER ::= { id-on 7 }
SRVName ::= IA5String (SIZE (1..MAX))
Santesson Standards Track [Page 2]
RFC 4985 DNS SRV RR otherName August 2007
The SRVName, if present, MUST contain a service name and a domain
name in the following form:
_Service.Name
The content of the components of this name form MUST be consistent
with the corresponding definition of these components in an SRV RR
according to RFC 2782 [N3].
The content of these components are:
Service
The symbolic name of the desired service, as defined in
Assigned Numbers [N5] or locally. An underscore (_) is
prepended to the service identifier to avoid collisions with
DNS labels that occur in nature. Some widely used services,
notably POP, don't have a single universal name. If Assigned
Numbers names the service indicated, that name is the only name
that is allowed in the service component of this name form.
The Service is case insensitive.
Name
The DNS domain name of the domain where the specified service
is located.
If the domain name is an Internationalized Domain Name (IDN),
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