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CVS libidn/doc/specifications
From: |
libidn-commit |
Subject: |
CVS libidn/doc/specifications |
Date: |
Thu, 24 Feb 2005 18:49:15 +0100 |
Update of /home/cvs/libidn/doc/specifications
In directory dopio:/tmp/cvs-serv13026
Added Files:
draft-ietf-ldapbis-dn-16.txt
Log Message:
Add.
--- /home/cvs/libidn/doc/specifications/draft-ietf-ldapbis-dn-16.txt
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2005/02/24 17:49:15 1.1
INTERNET-DRAFT Editor: Kurt D. Zeilenga
Intended Category: Standard Track OpenLDAP Foundation
Expires in six months 10 February 2005
Obsoletes: RFC 2253
LDAP: String Representation of Distinguished Names
<draft-ietf-ldapbis-dn-16.txt>
Status of Memo
This document is intended to be, after appropriate review and
revision, submitted to the RFC Editor as a Standard Track document
replacing RFC 2253. Distribution of this memo is unlimited.
Technical discussion of this document will take place on the IETF LDAP
Revision (LDAPBIS) Working Group mailing list
<address@hidden>. Please send editorial comments directly
to the document editor <address@hidden>.
By submitting this Internet-Draft, I accept the provisions of Section
4 of RFC 3667. By submitting this Internet-Draft, I certify that any
applicable patent or other IPR claims of which I am aware have been
disclosed, or will be disclosed, and any of which I become aware will
be disclosed, in accordance with RFC 3668.
Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference material
or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
Copyright (C) The Internet Society (2005). All Rights Reserved.
Please see the Full Copyright section near the end of this document
for more information.
Zeilenga LDAP: Distinguished Names [Page 1]
INTERNET-DRAFT draft-ietf-ldapbis-dn-16.txt 10 February 2005
Abstract
The X.500 Directory uses distinguished names (DNs) as primary keys to
entries in the directory. This document defines the string
representation used in the Lightweight Directory Access Protocol
(LDAP) to transfer distinguished names. The string representation is
designed to give a clean representation of commonly used distinguished
names, while being able to represent any distinguished name.
1. Background and Intended Usage
In X.500-based directory systems [X.500], including those accessed
using the Lightweight Directory Access Protocol (LDAP) [Roadmap],
distinguished names (DNs) are used to unambiguously refer to directory
entries [X.501][Models].
The structure of a DN [X.501] is described in terms of ASN.1 [X.680].
In the X.500 Directory Access Protocol [X.511] (and other ITU-defined
directory protocols), DNs are encoded using the Basic Encoding Rules
(BER) [X.690]. In LDAP, DNs are represented in the string form
described in this document.
It is important to have a common format to be able to unambiguously
represent a distinguished name. The primary goal of this
specification is ease of encoding and decoding. A secondary goal is
to have names that are human readable. It is not expected that LDAP
implementations with a human user interface would display these
strings directly to the user, but would most likely be performing
translations (such as expressing attribute type names in the local
national language).
This document defines the string representation of Distinguished Names
used in LDAP [Protocol][Syntaxes]. Section 2 details the RECOMMENDED
algorithm for converting a DN from its ASN.1 structured representation
to a string. Section 3 details how to convert a DN from a string to a
ASN.1 structured representation.
While other documents may define other algorithms for converting a DN
from its ASN.1 structured representation to a string, all algorithms
MUST produce strings which adhere to the requirements of Section 3.
This document does not define a canonical string representation for
DNs. Comparison of DNs for equality is to be performed in accordance
with the distinguishedNameMatch matching rule [Syntaxes].
This document is a integral part of the LDAP technical specification
[Roadmap] which obsoletes the previously defined LDAP technical
Zeilenga LDAP: Distinguished Names [Page 2]
INTERNET-DRAFT draft-ietf-ldapbis-dn-16.txt 10 February 2005
specification, RFC 3377, in its entirety. This document obsoletes RFC
2253. Changes since RFC 2253 are summarized in Appendix B.
This specification assumes familiarity with X.500 [X.500] and the
concept of Distinguished Name [X.501][Models].
1.1. Conventions
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 BCP 14 [RFC2119].
Character names in this document use the notation for code points and
names from the Unicode Standard [Unicode]. For example, the letter
"a" may be represented as either <U+0061> or <LATIN SMALL LETTER A>.
Note: a glossary of terms used in Unicode can be found in [Glossary].
Information on the Unicode character encoding model can be found in
[CharModel].
2. Converting DistinguishedName from ASN.1 to a String
X.501 [X.501] defines the ASN.1 [X.680] structure of distinguished
name. The following is a variant provided for discussion purposes.
DistinguishedName ::= RDNSequence
RDNSequence ::= SEQUENCE OF RelativeDistinguishedName
RelativeDistinguishedName ::= SET SIZE (1..MAX) OF
AttributeTypeAndValue
AttributeTypeAndValue ::= SEQUENCE {
type AttributeType,
value AttributeValue }
This section defines the RECOMMENDED algorithm for converting a
distinguished name from an ASN.1 structured representation to an UTF-8
[RFC3629] encoded Unicode [Unicode] character string representation.
Other documents may describe other algorithms for converting a
distinguished name to a string, but only strings which conform to the
grammar defined in Section 3 SHALL be produced by LDAP
implementations.
2.1. Converting the RDNSequence
Zeilenga LDAP: Distinguished Names [Page 3]
INTERNET-DRAFT draft-ietf-ldapbis-dn-16.txt 10 February 2005
If the RDNSequence is an empty sequence, the result is the empty or
zero length string.
Otherwise, the output consists of the string encodings of each
RelativeDistinguishedName in the RDNSequence (according to Section
2.2), starting with the last element of the sequence and moving
backwards toward the first.
The encodings of adjoining RelativeDistinguishedNames are separated by
a comma (',' U+002C) character.
2.2. Converting RelativeDistinguishedName
When converting from an ASN.1 RelativeDistinguishedName to a string,
the output consists of the string encodings of each
AttributeTypeAndValue (according to Section 2.3), in any order.
Where there is a multi-valued RDN, the outputs from adjoining
AttributeTypeAndValues are separated by a plus sign ('+' U+002B)
character.
2.3. Converting AttributeTypeAndValue
The AttributeTypeAndValue is encoded as the string representation of
the AttributeType, followed by an equals sign ('=' U+003D) character,
followed by the string representation of the AttributeValue. The
encoding of the AttributeValue is given in Section 2.4.
If the AttributeType is defined to have a short name (descriptor)
[Models] and that short name is known to be registered
[REGISTRY][BCP64bis] as identifying the AttributeType, that short
name, a <descr>, is used. Otherwise the AttributeType is encoded as
the dotted-decimal encoding, a <numericoid>, of its OBJECT IDENTIFIER.
The <descr> and <numericoid> is defined in [Models].
Implementations are not expected to dynamically update their knowledge
of registered short names. However, implementations SHOULD provide a
mechanism to allow its knowledge of registered short names to be
updated.
2.4. Converting an AttributeValue from ASN.1 to a String
If the AttributeType is of the dotted-decimal form, the AttributeValue
is represented by an number sign ('#' U+0023) character followed by
the hexadecimal encoding of each of the octets of the BER encoding of
Zeilenga LDAP: Distinguished Names [Page 4]
INTERNET-DRAFT draft-ietf-ldapbis-dn-16.txt 10 February 2005
the X.500 AttributeValue. This form is also used when the syntax of
the AttributeValue does not have a LDAP-specific [Syntaxes, Section
3.1] string encoding defined for it or the LDAP-specific string
encoding is not restricted to UTF-8 encoded Unicode characters. This
form may also be used in other cases, such as when a reversible string
representation is desired (see Section 5.2).
Otherwise, if the AttributeValue is of a syntax which has a
LDAP-specific string encoding, the value is converted first to a UTF-8
encoded Unicode string according to its syntax specification (see
[Syntaxes, Section 3.3] for examples). If that UTF-8 encoded Unicode
string does not have any of the following characters which need
escaping, then that string can be used as the string representation of
the value.
- a space (' ' U+0020) or number sign ('#' U+0023) occurring at
the beginning of the string;
- a space (' ' U+0020) character occurring at the end of the
string;
- one of the characters '"', '+', ',', ';', '<', '>', or '\'
(U+0022, U+002B, U+002C, U+003B, U+003C, U+003E, or U+005C
respectively);
- the null (U+0000) character.
Other characters may be escaped.
Each octet of the character to be escaped is replaced by a backslash
and two hex digits, which form a single octet in the code of the
character. Alternatively, if and only if the character to be escaped
is one of
' ', '"', '#', '+', ',', ';', '<', '=', '>', or '\'
(U+0020, U+0022, U+0023, U+002B, U+002C, U+003B,
U+003C, U+003D, U+003E, U+005C respectively)
it can be prefixed by a backslash ('\' U+005C).
Examples of the escaping mechanism are shown in Section 4.
3. Parsing a String back to a Distinguished Name
The string representation of Distinguished Names is restricted to
UTF-8 [RFC3629] encoded Unicode [Unicode] characters. The structure
of this string representation is specified using the following
Zeilenga LDAP: Distinguished Names [Page 5]
INTERNET-DRAFT draft-ietf-ldapbis-dn-16.txt 10 February 2005
Augmented BNF [RFC2234] grammar:
distinguishedName = [ relativeDistinguishedName
*( COMMA relativeDistinguishedName ) ]
relativeDistinguishedName = attributeTypeAndValue
*( PLUS attributeTypeAndValue )
attributeTypeAndValue = attributeType EQUALS attributeValue
attributeType = descr / numericoid
attributeValue = string / hexstring
; The following characters are to be escaped when they appear
; in the value to be encoded: ESC, one of <escaped>, leading
; SHARP or SPACE, trailing SPACE, and NULL.
string = [ ( leadchar / pair ) [ *( stringchar / pair )
( trailchar / pair ) ] ]
leadchar = LUTF1 / UTFMB
LUTF1 = %x01-1F / %x21 / %x24-2A / %x2D-3A /
%x3D / %x3F-5B / %x5D-7F
trailchar = TUTF1 / UTFMB
TUTF1 = %x01-1F / %x21 / %x23-2A / %x2D-3A /
%x3D / %x3F-5B / %x5D-7F
stringchar = SUTF1 / UTFMB
SUTF1 = %x01-21 / %x23-2A / %x2D-3A /
%x3D / %x3F-5B / %x5D-7F
pair = ESC ( ESC / special / hexpair )
special = escaped / SPACE / SHARP / EQUALS
escaped = DQUOTE / PLUS / COMMA / SEMI / LANGLE / RANGLE
hexstring = SHARP 1*hexpair
hexpair = HEX HEX
where the productions <descr>, <numericoid>, <COMMA>, <DQUOTE>,
<EQUALS>, <ESC>, <HEX>, <LANGLE>, <NULL>, <PLUS>, <RANGLE>, <SEMI>,
<SPACE>, <SHARP>, <UTFMB> are defined in [Models].
Each <attributeType>, either a <descr> or a <numericoid>, refers to an
attribute type of an attribute value assertion (AVA). The
<attributeType> is followed by a <EQUALS> and an <attributeValue>.
The <attributeValue> is either in <string> or <hexstring> form.
If in <string> form, a LDAP string representation asserted value can
be obtained by replacing (left-to-right, non-recursively) each <pair>
appearing in the <string> as follows:
replace <ESC><ESC> with <ESC>;
replace <ESC><special> with <special>;
Zeilenga LDAP: Distinguished Names [Page 6]
INTERNET-DRAFT draft-ietf-ldapbis-dn-16.txt 10 February 2005
replace <ESC><hexpair> with the octet indicated by the <hexpair>.
If in <hexstring> form, a BER representation can be obtained from
converting each <hexpair> of the <hexstring> to the octet indicated by
the <hexpair>.
One or more attribute values assertions, separated by <PLUS>, for a
relative distinguished name.
Zero or more relative distinguished names, separated by <COMMA>, for a
distinguished name.
Implementations MUST recognize AttributeType name strings
(descriptors) listed in the following table, but MAY recognize other
name strings.
String X.500 AttributeType
------ --------------------------------------------
CN commonName (2.5.4.3)
L localityName (2.5.4.7)
ST stateOrProvinceName (2.5.4.8)
O organizationName (2.5.4.10)
OU organizationalUnitName (2.5.4.11)
C countryName (2.5.4.6)
STREET streetAddress (2.5.4.9)
DC domainComponent (0.9.2342.19200300.100.1.25)
UID userId (0.9.2342.19200300.100.1.1)
Implementations MAY recognize other DN string representations (such as
that described in RFC 1779). However, as there is no requirement that
alternative DN string representations to be recognized (and, if so,
how), implementations SHOULD only generate DN strings in accordance
with Section 2 of this document.
4. Examples
This notation is designed to be convenient for common forms of name.
This section gives a few examples of distinguished names written using
this notation. First is a name containing three relative
distinguished names (RDNs):
UID=jsmith,DC=example,DC=net
Here is an example name containing three RDNs, in which the first RDN
is multi-valued:
OU=Sales+CN=J. Smith,DC=example,DC=net
Zeilenga LDAP: Distinguished Names [Page 7]
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This example shows the method of escaping of a special characters
appearing in a common name:
[443 lines skipped]