Opened 12 years ago

Closed 12 years ago

#10 closed defect (fixed)

Section 4.4

Reported by: bernard_aboba@… Owned by: jon.peterson@…
Priority: major Milestone: milestone1
Component: draft-iab-dns-applications Version: 1.0
Severity: Active WG Document Keywords:
Cc: stefan@…


Implementing domain redirection in the DNS, however, has important
consequences for application security, in the absence of universal
DNSSEC. Applications must trust DNS in order to accept that their
request has not been hijacked and redirected to a potentially
malicious domain, as the target of the redirection typically cannot
produce a certificate corresponding to the initially-requested
domain. In the application layer, protocols like HTTP and SIP have
widely deployed security mechanisms such as TLS that can use
certificates to vouch that a redirection came from the domain that
the originator initially hoped to contact.

[BA] RFC 4985 appears to provide a mechanism for the target of a
redirection to assert the legitimacy of an SRV RR binding, without
having to produce a certificate corresponding to the initially requested domain. From RFC 4985 Section 1:

  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

The document defines the SRVName as follows:

id-on-dnsSRV OBJECT IDENTIFIER ::= { id-on 7 }

SRVName ::= IA5String (SIZE (1..MAX))

The SRVName, if present, MUST contain a service name and a domain
name in the following form:


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:


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.


The DNS domain name of the domain where the specified service
is located.

If the domain name is an Internationalized Domain Name (IDN),
then encoding in ASCII form SHALL be done as defined in section

Note that the protocol component is not included.

Change History (3)

comment:1 Changed 12 years ago by bernard_aboba@…

  • Component changed from dns-applications to draft-iab-dns-applications

comment:2 Changed 12 years ago by bernard_aboba@…

  • Severity changed from Candidate WG Document to Active WG Document

comment:3 Changed 12 years ago by jon.peterson@…

  • Resolution set to fixed
  • Status changed from new to closed

some text regarding RFC4985 as a potential solution and the hard-problem draft has been added

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