draft-ietf-ldapbis-dn-07.txt   draft-ietf-ldapbis-dn-08.txt 
INTERNET-DRAFT Editor: Kurt D. Zeilenga INTERNET-DRAFT Editor: Kurt D. Zeilenga
Intended Category: Standard Track OpenLDAP Foundation Intended Category: Standard Track OpenLDAP Foundation
Expires in six months 1 March 2002 Expires in six months 18 August 2002
Obsoletes: 2253 Obsoletes: 2253
LDAP: String Representation of Distinguished Names LDAP: String Representation of Distinguished Names
<draft-ietf-ldapbis-dn-07.txt> <draft-ietf-ldapbis-dn-08.txt>
Status of Memo Status of Memo
This document is an Internet-Draft and is in full conformance with all This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026. provisions of Section 10 of RFC2026.
This document is intended to be, after appropriate review and This document is intended to be, after appropriate review and
revision, submitted to the RFC Editor as a Standard Track document revision, submitted to the RFC Editor as a Standard Track document
replacing RFC 2253. Distribution of this memo is unlimited. replacing RFC 2253. Distribution of this memo is unlimited.
Technical discussion of this document will take place on the IETF LDAP Technical discussion of this document will take place on the IETF LDAP
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Please send editorial comments directly to the document editor <ietf-ldapbis@openldap.org>. Please send editorial comments directly
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Copyright 2002, The Internet Society. All Rights Reserved. Copyright 2002, The Internet Society. All Rights Reserved.
Please see the Copyright section near the end of this document for Please see the Copyright section near the end of this document for
more information. more information.
Abstract Abstract
The X.500 Directory uses distinguished names as the primary keys to The X.500 Directory uses distinguished names (DNs) as primary keys to
entries in the directory. Distinguished Names are encoded in ASN.1 in entries in the directory. This document defines the string
the X.500 Directory protocols. In the Lightweight Directory Access representation used in the Lightweight Directory Access Protocol
Protocol, a string representation of distinguished names is (LDAP) to transfer distinguished names. The string representation is
transferred. This specification defines the string format for designed to give a clean representation of commonly used distinguished
representing names, which is designed to give a clean representation names, while being able to represent any distinguished name.
of commonly used distinguished names, while being able to represent
any distinguished name.
1. Background 1. Background and Intended Usage
This specification assumes familiarity with X.500 [X.500], and the In X.500-based directory systems [X.500], including those accessed
concept of Distinguished Name (DN). It is important to have a common using the Lightweight Directory Access Protocol (LDAP) [LDAPTS],
format to be able to unambiguously represent a distinguished name. distinguished names (DNs) are used to unambiguously refer to a
The primary goal of this specification is ease of encoding and directory entry [X.501][Models].
decoding. A secondary goal is to have names that are human readable.
It is not expected that LDAP clients with a human user interface would The structure of a DN [X.501] is described in terms of ASN.1 [X.680].
display these strings directly to the user, but would most likely be In the X.500 Directory Access Protocol [X.511] (and other ITU-defined
performing translations (such as expressing attribute type names in directory protocols), DNs are encoded using the Basic Encoding Rules
one of the local national languages). (BER) [X.690]. In LDAP, DNs are represented in string form.
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 one of the
local national languages).
This document defines the string representation of Distinguished Names
used in LDAP [Protocol][Syntaxes]. Section 2 details how to convert a
DN from ASN.1 structured representation to a string. Section 3
details how to convert a DN from string to ASN.1 structured
representation.
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 an integral part of the LDAP Technical Specification This document is an integral part of the LDAP Technical Specification
[Roadmap]. [Roadmap].
This document obsoletes RFC 2253. Changes since RFC 2253 are This document obsoletes RFC 2253. Changes since RFC 2253 are
summarized in Appendix A. summarized in Appendix B.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14 [RFC2119]. document are to be interpreted as described in BCP 14 [RFC2119].
This specification assumes familiarity with X.500 [X.500], and the
concept of Distinguished Name [X.501][Models].
2. Converting DistinguishedName from ASN.1 to a String 2. Converting DistinguishedName from ASN.1 to a String
In X.501 [X.501] the ASN.1 structure of distinguished name is defined In X.501 [X.501] the ASN.1 [X.680] structure of distinguished name is
as: defined as:
DistinguishedName ::= RDNSequence DistinguishedName ::= RDNSequence
RDNSequence ::= SEQUENCE OF RelativeDistinguishedName RDNSequence ::= SEQUENCE OF RelativeDistinguishedName
RelativeDistinguishedName ::= SET SIZE (1..MAX) OF RelativeDistinguishedName ::= SET SIZE (1..MAX) OF
AttributeTypeAndValue AttributeTypeAndValue
AttributeTypeAndValue ::= SEQUENCE { AttributeTypeAndValue ::= SEQUENCE {
type AttributeType, type AttributeType,
value AttributeValue } value AttributeValue }
The following sections define the RECOMMENDED algorithm for converting This section defines the RECOMMENDED algorithm for converting a
from an ASN.1 structured representation to a UTF-8 [RFC2279] string distinguished name from an ASN.1 structured representation to an UTF-8
representation. [RFC2279] encoded Universal Character Set (UCS) [ISO10646] character
string representation.
2.1. Converting the RDNSequence 2.1. Converting the RDNSequence
If the RDNSequence is an empty sequence, the result is the empty or If the RDNSequence is an empty sequence, the result is the empty or
zero length string. zero length string.
Otherwise, the output consists of the string encodings of each Otherwise, the output consists of the string encodings of each
RelativeDistinguishedName in the RDNSequence (according to 2.2), RelativeDistinguishedName in the RDNSequence (according to Section
starting with the last element of the sequence and moving backwards 2.2), starting with the last element of the sequence and moving
toward the first. backwards toward the first.
The encodings of adjoining RelativeDistinguishedNames are separated by The encodings of adjoining RelativeDistinguishedNames are separated by
a comma character ("," ASCII 44). a comma character ("," U+0002C).
2.2. Converting RelativeDistinguishedName 2.2. Converting RelativeDistinguishedName
When converting from an ASN.1 RelativeDistinguishedName to a string, When converting from an ASN.1 RelativeDistinguishedName to a string,
the output consists of the string encodings of each the output consists of the string encodings of each
AttributeTypeAndValue (according to 2.3), in any order. AttributeTypeAndValue (according to Section 2.3), in any order.
Where there is a multi-valued RDN, the outputs from adjoining Where there is a multi-valued RDN, the outputs from adjoining
AttributeTypeAndValues are separated by a plus ("+" ASCII 43) AttributeTypeAndValues are separated by a plus sign ("+" U+0002B)
character. character.
2.3. Converting AttributeTypeAndValue 2.3. Converting AttributeTypeAndValue
The AttributeTypeAndValue is encoded as the string representation of The AttributeTypeAndValue is encoded as the string representation of
the AttributeType, followed by an equals character ("=" ASCII 61), the AttributeType, followed by an equals character ("=" U+0003D),
followed by the string representation of the AttributeValue. The followed by the string representation of the AttributeValue. The
encoding of the AttributeValue is given in Section 2.4. encoding of the AttributeValue is given in Section 2.4.
If the AttributeType is in the following table of attribute types If the AttributeType is in the following table of attribute types
associated with LDAP [Schema], then the type name string from that associated with LDAP [Schema], then the type name string, a <descr>,
table is used, otherwise it is encoded as the dotted-decimal encoding from that table is used, otherwise it is encoded as the dotted-decimal
of the AttributeType's OBJECT IDENTIFIER. The dotted-decimal notation encoding, a <numericoid>, of the AttributeType's OBJECT IDENTIFIER.
(numericoid) is described in [Models]. The <descr> and <numericoid> is defined in [Models].
The type name string is not case sensitive. The type name string is not case sensitive.
String X.500 AttributeType String X.500 AttributeType
------ -------------------------------------------- ------ --------------------------------------------
CN commonName (2.5.4.3) CN commonName (2.5.4.3)
L localityName (2.5.4.7) L localityName (2.5.4.7)
ST stateOrProvinceName (2.5.4.8) ST stateOrProvinceName (2.5.4.8)
O organizationName (2.5.4.10) O organizationName (2.5.4.10)
OU organizationalUnitName (2.5.4.11) OU organizationalUnitName (2.5.4.11)
C countryName (2.5.4.6) C countryName (2.5.4.6)
STREET streetAddress (2.5.4.9) STREET streetAddress (2.5.4.9)
DC domainComponent (0.9.2342.19200300.100.1.25) DC domainComponent (0.9.2342.19200300.100.1.25)
UID userId (0.9.2342.19200300.100.1.1) UID userId (0.9.2342.19200300.100.1.1)
2.4. Converting an AttributeValue from ASN.1 to a String Note: This table lists the complete set of type name strings which
all implementations MUST recognize in DN string representation.
As no extension could reasonable require all existing
implementations be updated to recognize additional type name
strings, this table is not extensible.
If the AttributeValue is of a type which does not have a string 2.4. Converting an AttributeValue from ASN.1 to a String
representation defined for it, then it is simply encoded as an
octothorpe character ("#" ASCII 35) followed by the hexadecimal
representation of each of the octets of the BER encoding of the X.500
AttributeValue. This form is also be used if the AttributeType is of
the dotted-decimal form.
Otherwise, if the AttributeValue is of a type which has a string If the AttributeType is of the dotted-decimal form, the AttributeValue
representation, the value is converted first to a UTF-8 string is represented by an number sign character ("#" U+00023) followed by
according to its syntax specification (see for example Section 6 of the hexadecimal encoding of each of the octets of the BER encoding of
[Syntaxes]). the X.500 AttributeValue. This form is also used when the syntax of
the AttributeValue does not have a native string encoding defined for
it or the native string encoding is not restricted to UTF-8 encoded
UCS (or a subset of UCS) characters. This form may also be used in
other cases, such as when a reversible string representation is
desired (see Section 5.2).
If the UTF-8 string does not have any of the following characters Otherwise, if the AttributeValue is of a syntax which has a native
which need escaping, then that string can be used as the string string encoding, the value is converted first to a UTF-8 encoded UCS
representation of the value. string according to its syntax specification (see for example Section
6 of [Syntaxes]). If that UTF-8 encoded UCS 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 (" " ASCII 32) or octothorpe ("#" ASCII 35) occurring at - a space (" " U+00020) or number sign ("#" U+00023) occurring at
the beginning of the string the beginning of the string;
- a space (" " ASCII 32) character occurring at the end of the - a space (" " U+00020) character occurring at the end of the
string string;
- one of the characters ",", "+", """, "\", "<", ">" or ";" (ASCII - one of the characters """, "+", ",", ";", "<", ">", or "\"
44, 43, 34, 92, 60, 62, or 59, respectively) (U+00022, U+0002B, U+0002C, U+0003B, U+0003C, U+0003E, or
U+0005C respectively);
- the null (ASCII 0) character - the null (U+00000) character.
Implementations MAY escape other characters. Other characters may be escaped.
Each octet of the character to be escaped is replaced by a backslash 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 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 character. Alternatively, if and only if the character to be escaped
is one of is one of
",", "+", """, "\", "<", ">", ";", "#", "=", or " " " ", """, "#", "+", ",", ";", "<", "=", ">", or "\"
(ASCII 44, 43, 34, 92, 60, 62, 59, 35, 61 or 32 respectively) (U+00020, U+00022, U+00023, U+0002B, U+0002C, U+0003B,
U+0003C, U+0003D, U+0003E, U+0005C respectively)
it can be prefixed by a backslash ("\" ASCII 92). it can be prefixed by a backslash ("\" U+00005C).
Examples of the escaping mechanism are shown in Section 4. Examples of the escaping mechanism are shown in Section 4.
3. Parsing a String back to a Distinguished Name 3. Parsing a String back to a Distinguished Name
The structure of the UTF-8 [RFC2279] string is specified using the The string representation of Distinguished Names is restricted to
following Augmented BNF [RFC2234] grammar. UTF-8 [RFC2279] encoded characters from the Universal Character Set
(UCS) [ISO10646]. The structure of this string representation is
distinguishedName = [name] specified using the following Augmented BNF [RFC2234] grammar using
; may be empty the common productions defined in [Models].
name = name-component *(COMMA name-component)
name-component = attributeTypeAndValue *(PLUS attributeTypeAndValue)
attributeTypeAndValue
= attributeType EQUALS attributeValue
attributeType = keyword / oid distinguishedName = [ relativeDistinguishedName
*( COMMA relativeDistinguishedName ) ]
keyword = ALPHA 1*keychar relativeDistinguishedName = attributeTypeAndValue
*( PLUS attributeTypeAndValue )
keychar = ALPHA / DIGIT / MINUS attributeTypeAndValue = attributeType EQUALS attributeValue
attributeType = descr / numericoid
oid = number *(DOT number) attributeValue = string / hexstring
number = ( LDIGIT *DIGIT ) / DIGIT ; The UTF-8 string shall not contain NULL, ESC, or
; one of escaped, shall not start with SHARP or SPACE,
; and shall must not end with SPACE.
string = [ (leadchar / pair)
[ *( stringchar / pair ) ( trailchar / pair ) ] ]
attributeValue = string / hexstring leadchar = LUTF1 / UTFMB
LUTF1 = %x01-1F / %x21 / %x24-2A / %x2D-3A /
%x3D / %x3F-5B / %x5D-7F
string = *( stringchar / pair ) trailchar = TUTF1 / UTFMB
; the string MUST NOT start with SHARP or SP TUTF1 = %x01-1F / %x21 / %x23-2A / %x2D-3A /
; and MUST NOT end with SP %x3D / %x3F-5B / %x5D-7F
stringchar = <any UTF-8 character (can be multiple octets) stringchar = SUTF1 / UTFMB
except one of escaped or ESC or NULL> SUTF1 = %x01-21 / %x23-2A / %x2D-3A /
%x3D / %x3F-5B / %x5D-7F
pair = ESC ( ESC / special / hexpair ) pair = ESC ( ESC / special / hexpair )
special = escaped / SHARP / EQUALS / SP special = escaped / SPACE / SHARP / EQUALS
escaped = COMMA / PLUS / %x22 / %x3C / %x3E / %x3B escaped = DQUOTE / PLUS / COMMA / SEMI / LANGLE / RANGLE
; "," / "+" / """ / "<" / ">" / ";"
hexstring = SHARP 1*hexpair hexstring = SHARP 1*hexpair
hexpair = HEX HEX hexpair = HEX HEX
HEX = DIGIT / %x41-46 / %x61-66 where the productions <descr>, <numericoid>, <COMMA>, <DQUOTE>,
; 0-9 / A-F / a-f <EQUALS>, <ESC>, <HEX>, <LANGLE>, <NULL>, <PLUS>, <RANGLE>, <SEMI>,
ALPHA = %x41-5A / %x61-7A <SPACE>, <SHARP>, <UTFMB> are defined in [Models].
; A-Z / a-z
LDIGIT = %x31-39
; 1-9
DIGIT = %x30 / LDIGIT
; 0-9
SP = %x20 ; space (" ")
SHARP = %x23 ; octothorpe (or sharp sign) ("#")
PLUS = %x2B ; plus sign ("+")
COMMA = %x2C ; comma (",")
MINUS = %x2D ; minus sign ("-")
DOT = %x2E ; period (".")
EQUALS = %x3D ; equals sign ("=")
ESC = %x5C ; backslash ("\")
NULL = %x00 ; null (0)
Implementations MUST recognize AttributeType string type names Implementations MUST recognize AttributeType name strings
(keywords) listed in the Section 2.3 table, but MAY recognize other (descriptors) listed in the Section 2.3 table, but MAY recognize other
names. Implementations MAY recognize other DN string representations name strings. Implementations MAY recognize other DN string
(such as that described in RFC 1779). As there is no requirement for representations (such as that described in RFC 1779). However, as
other names or alternative DN string representations to be recognized, there is no requirement for other names or alternative DN string
implementations SHOULD only generate DN strings in accordance with representations to be recognized (and, if so, how), implementations
Section 2 of this document. SHOULD only generate DN strings in accordance with Section 2 of this
document.
4. Examples 4. Examples
This notation is designed to be convenient for common forms of name. This notation is designed to be convenient for common forms of name.
This section gives a few examples of distinguished names written using This section gives a few examples of distinguished names written using
this notation. First is a name containing three relative this notation. First is a name containing three relative
distinguished names (RDNs): distinguished names (RDNs):
UID=jsmith,DC=example,DC=net UID=jsmith,DC=example,DC=net
Here is an example name containing three RDNs, in which the first RDN Here is an example name containing three RDNs, in which the first RDN
is multi-valued: is multi-valued:
skipping to change at page 7, line 16 skipping to change at page 7, line 33
An example name in which an RDN was of an unrecognized type. The An example name in which an RDN was of an unrecognized type. The
value is the BER encoding of an OCTET STRING containing two octets value is the BER encoding of an OCTET STRING containing two octets
0x48 and 0x69. 0x48 and 0x69.
1.3.6.1.4.1.1466.0=#04024869,DC=example,DC=com 1.3.6.1.4.1.1466.0=#04024869,DC=example,DC=com
Finally, an example of an RDN commonName value consisting of 5 Finally, an example of an RDN commonName value consisting of 5
letters: letters:
Unicode Letter Description 10646 code UTF-8 Quoted Unicode Letter Description UCS code UTF-8 Quoted
=============================== ========== ====== ======= ------------------------------- -------- ------ --------
LATIN CAPITAL LETTER L U+0000004C 0x4C L LATIN CAPITAL LETTER L U+0004C 0x4C L
LATIN SMALL LETTER U U+00000075 0x75 u LATIN SMALL LETTER U U+00075 0x75 u
LATIN SMALL LETTER C WITH CARON U+0000010D 0xC48D \C4\8D LATIN SMALL LETTER C WITH CARON U+0010D 0xC48D \C4\8D
LATIN SMALL LETTER I U+00000069 0x69 i LATIN SMALL LETTER I U+00069 0x69 i
LATIN SMALL LETTER C WITH ACUTE U+00000107 0xC487 \C4\87 LATIN SMALL LETTER C WITH ACUTE U+00107 0xC487 \C4\87
could be written in printable ASCII (useful for debugging purposes): could be written in printable ASCII (useful for debugging purposes):
CN=Lu\C4\8Di\C4\87 CN=Lu\C4\8Di\C4\87
5. Security Considerations 5. Security Considerations
The following security considerations are specific to the handling of The following security considerations are specific to the handling of
distinguished names. LDAP security considerations are discussed in distinguished names. LDAP security considerations are discussed in
[Protocol] and other documents comprising the LDAP Technical [Protocol] and other documents comprising the LDAP Technical
skipping to change at page 8, line 23 skipping to change at page 8, line 38
For example, a distinguished name consisting of one RDN with one AVA, For example, a distinguished name consisting of one RDN with one AVA,
in which the type is commonName and the value is of the TeletexString in which the type is commonName and the value is of the TeletexString
choice with the letters 'Sam' would be represented in LDAP as the choice with the letters 'Sam' would be represented in LDAP as the
string CN=Sam. Another distinguished name in which the value is still string CN=Sam. Another distinguished name in which the value is still
'Sam' but of the PrintableString choice would have the same 'Sam' but of the PrintableString choice would have the same
representation CN=Sam. representation CN=Sam.
Applications which require the reconstruction of the DER form of the Applications which require the reconstruction of the DER form of the
value SHOULD NOT use the string representation of attribute syntaxes value SHOULD NOT use the string representation of attribute syntaxes
when converting a distinguished name to the LDAP format. Instead, when converting a distinguished name to the LDAP format. Instead,
they SHOULD use the hexadecimal form prefixed by the octothorpe ('#') they SHOULD use the hexadecimal form prefixed by the number sign ('#')
as described in the first paragraph of Section 2.3. as described in the first paragraph of Section 2.3.
5.3. Use of Other Names 5.3. Use of Other Names
Attribute type names are not unique. A string representation Attribute type names are not unique. A string representation
generated with names other than those in the Section 2.3 table is generated with names other than those in the Section 2.3 table is
ambiguous. That is, two applications may recognize the string as ambiguous. That is, two applications may recognize the string as
representing two different DNs possibly associated with two different representing two different DNs possibly associated with two different
entries. This may lead to a wide range of unexpected behaviors which entries. This may lead to a wide range of unexpected behaviors which
can have both direct and indirect impacts upon security. can have both direct and indirect impacts upon security.
skipping to change at page 8, line 46 skipping to change at page 9, line 14
of the known locally attribute type FOO and the value "BAR" (an of the known locally attribute type FOO and the value "BAR" (an
octetString) could be represented in LDAP as the string FOO=BAR. As octetString) could be represented in LDAP as the string FOO=BAR. As
the name FOO does not uniquely identify an attribute type, the DN the name FOO does not uniquely identify an attribute type, the DN
FOO=BAR is ambiguous. That is, FOO could be recognized as the FOO=BAR is ambiguous. That is, FOO could be recognized as the
attribute type 1.1.1 by one application and 1.2.3.4 in another and not attribute type 1.1.1 by one application and 1.2.3.4 in another and not
recognized by another. This may lead to operations not behaving as recognized by another. This may lead to operations not behaving as
intended. intended.
Applications desiring to generate an unambiguous string representation Applications desiring to generate an unambiguous string representation
of a DN SHOULD generate string representation per section 2, not use of a DN SHOULD generate string representation per section 2, not use
names other than those in the Section 2.3 table, and while taking 5.2 names other than those in the Section 2.3 table, and while taking
into consideration. Section 5.2 into consideration.
It is noted that while a registry for attribute type names
(descriptors) has been established [LDAPIANA], this registry does not
remove the ambiguity of attribute types names used in LDAP. It only
removes the ambiguity of attribute type names used in Standard Track
technical specifications.
6. Acknowledgment 6. Acknowledgment
This document is an update to RFC 2253, by Mark Wahl, Tim Howes, and This document is an update to RFC 2253, by Mark Wahl, Tim Howes, and
Steve Kille. RFC 2253 was a product of the IETF ASID Working Group. Steve Kille. RFC 2253 was a product of the IETF ASID Working Group.
This document is a product of the IETF LDAPbis Working Group. This document is a product of the IETF LDAPbis Working Group.
7. Document Editor's Address 7. Document Editor's Address
Kurt D. Zeilenga Kurt D. Zeilenga
OpenLDAP Foundation OpenLDAP Foundation
<Kurt@OpenLDAP.org> <Kurt@OpenLDAP.org>
skipping to change at page 9, line 19 skipping to change at page 9, line 40
7. Document Editor's Address 7. Document Editor's Address
Kurt D. Zeilenga Kurt D. Zeilenga
OpenLDAP Foundation OpenLDAP Foundation
<Kurt@OpenLDAP.org> <Kurt@OpenLDAP.org>
8. Normative References 8. Normative References
[X.501] "The Directory -- Models," ITU-T Rec. X.501(1993). [X.501] "The Directory -- Models," ITU-T Rec. X.501(1993).
[X.680] ITU-T, "Abstract Syntax Notation One (ASN.1) -
Specification of Basic Notation", X.680, 1994.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119. Requirement Levels", BCP 14 (also RFC 2119).
[RFC2234] Crocker, D., and P. Overell, "Augmented BNF for Syntax [RFC2234] Crocker, D., and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997. Specifications: ABNF", RFC 2234, November 1997.
[RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO
10646", RFC 2279, January 1998. 10646", RFC 2279, January 1998.
[Models] K. Zeilenga (editor), "LDAP: Directory Information [Models] K. Zeilenga (editor), "LDAP: Directory Information
Models", draft-ietf-ldapbis-models-xx.txt, a work in Models", draft-ietf-ldapbis-models-xx.txt, a work in
progress. progress.
[Roadmap] K. Zeilenga (editor), "LDAP: Technical Specification Road [Roadmap] K. Zeilenga, "LDAP: Technical Specification Road Map",
Map", draft-ietf-ldapbis-roadmap-xx.txt, a work in draft-ietf-ldapbis-roadmap-xx.txt, a work in progress.
progress.
[Protocol] J. Sermersheim (editor), "LDAP: The Protocol", [Protocol] J. Sermersheim (editor), "LDAP: The Protocol",
draft-ietf-ldapbis-protocol-xx.txt, a work in progress. draft-ietf-ldapbis-protocol-xx.txt, a work in progress.
[Syntaxes] K. Dally (editor), "LDAP: Syntaxes", [Syntaxes] S. Legg (editor), "LDAP: Syntaxes",
draft-ietf-ldapbis-syntaxes-xx.txt, a work in progress. draft-ietf-ldapbis-syntaxes-xx.txt, a work in progress.
[Schema] K. Dally (editor), "LDAP: User Schema", [Schema] K. Dally (editor), "LDAP: User Schema",
draft-ietf-ldapbis-user-schema-xx.txt, a work in draft-ietf-ldapbis-user-schema-xx.txt, a work in
progress. progress.
[ISO10646] Universal Multiple-Octet Coded Character Set (UCS) -
Architecture and Basic Multilingual Plane, ISO/IEC
10646-1 : 1993.
9. Informative References 9. Informative References
[X.500] "The Directory -- overview of concepts, models and [X.500] "The Directory -- overview of concepts, models and
services," ITU-T Rec. X.500(1993). services," ITU-T Rec. X.500(1993).
Appendix A. Changes made since RFC 2253 [X.690] ITU-T, "Specification of ASN.1 encoding rules: Basic,
Canonical, and Distinguished Encoding Rules", X.690,
1994.
[LDAPIANA] K. Zeilenga, "IANA Considerations for LDAP",
draft-ietf-ldapbis-xx.txt (a work in progress).
[RFC2849] G. Good, "The LDAP Data Interchange Format (LDIF) -
Technical Specification", RFC 2849, June 2000.
Appendix A. Presentation Issues
This appendix is provided for informational purposes only, it is not a
normative part of this specification.
The string representation described in this document is not intended
to be presented to humans without translation. However, at times it
may be desirable to present non-translated DN strings to users. This
section discusses presentation issues associated with non-translated
DN strings. Presentation of translated DN strings issues are not
discussed in this document. Transcoding issues are also not discussed
in this document.
This appendix provides guidance for applications presenting DN strings
to users. This section is not comprehensive, it does not discuss all
presentation issues which implementors may face.
Not all user interfaces are capable of displaying the full set of UCS
characters. Some UCS characters are not displayable.
It is recommended that human interfaces use the optional hex pair
escaping mechanism (Section 2.3) to produce a string representation
suitable for display to the human. For example, an application only
capable of displaying printable characters can generate a DN string
for display which escapes all non-printable characters appearing in
the AttributeValue's string representation (as demonstrated in the
final example of Section 4).
When a DN string is displayed in free form text, it is necessary to
distinguish the DN string from surrounding text. While this is often
done with white space (as demonstrated in Section 4), it is noted that
DN strings may end with white space. Careful readers of Section 3
will note that characters "<" and ">" may only appear in the DN string
if escaped. These characters are intended to be used in free form
text to distinguish a DN string from surrounding text. For example,
<CN=Sam\ > distinguished the string representation of the DN comprised
of one RDN consisting of the AVA: the commonName (CN) value "Sam "
from the surrounding text. It should be noted to the user that the
wrapping "<" and ">" characters are not part of the DN string.
DN strings can be quite long. It is often desirable to line-wrap
overly long DN strings in presentations. Line wrapping should be done
by inserting white space after the RDN separator character or, if
necessary, after the AVA separator character in such presentations.
It should be noted to the user that the inserted white space is not
part of the DN string and is to be removed before use in LDAP. For
example,
The following DN string is long:
CN=Kurt D. Zeilenga,OU=Engineering,L=Redwood Shores,
O=OpenLDAP Foundation,ST=California,C=US
so it has been line-wrapped for readability. The extra white
space is to be removed the DN string is used in LDAP.
It is not advised to insert white space otherwise as it may not be
obvious to the user what white space is part of the DN string and what
white space was added for readability.
Another alternative is to use the LDAP Data Interchange Format (LDIF)
[RFC2849]. For example,
The following entry has a long DN:
dn: CN=Kurt D. Zeilenga,OU=Engineering,L=Redwood Shores,
O=OpenLDAP Foundation,ST=California,C=US
CN: Kurt D. Zeilenga
SN: Zeilenga
objectClass: person
It is noted that that is often desirable to replace dotted-decimal
OIDs appearing in DN strings with attribute type names. Such
replacement is viewed as a translation and, hence, not discussed here.
Appendix B. Changes made since RFC 2253
This appendix is provided for informational purposes only, it is not a This appendix is provided for informational purposes only, it is not a
normative part of this specification. normative part of this specification.
The following substantive changes were made to RFC 2253: The following substantive changes were made to RFC 2253:
- Removed IESG Note. The IESG Note is addressed by RFC 2829. - Removed IESG Note. The IESG Note has been addressed.
- Clarified (in Section 1), that this document does not define a
canonical string representation.
- Replaced specification of additional requirements for LDAPv2 - Replaced specification of additional requirements for LDAPv2
implementations which also support LDAPv3 (Section 4) with a implementations which also support LDAPv3 (RFC 2253, Section 4)
statement (in Section 3) allowing recognition of alternative with a statement (in Section 3) allowing recognition of
string representations. alternative string representations.
- Updated 2.3 to clarify which table is the published table of names - Clarified (in Section 2.3) that the "published" table of names
which may be appear in DNs. Remove "as an example" language. which may be appear in DNs is the table which Section 2.3
Added statement (in Section 3) allowing recognition of additional provides. Remove "as an example" language. Noted this table is
names. Added security consideration (Section 5.3) regarding the not extensible. Added statement (in Section 3) allowing
use of other names. recognition of additional names. Added security considerations
- Updated 2.3 to indicate attribute type name strings are not case (Section 5.3) regarding the use of other names.
sensitive. - Updated Section 2.3 to indicate attribute type name strings are
- Updated 2.4 to allow hex pair escaping of all characters and case insensitive.
clarified escaping for when multiple octet UTF-8 characters are - Updated Section 2.4 to allow hex pair escaping of all characters
present. and clarified escaping for when multiple octet UTF-8 characters
are present.
- Rewrote Section 3 to use ABNF as defined in RFC 2234. - Rewrote Section 3 to use ABNF as defined in RFC 2234.
- Rewrote Section 3 ABNF to be consistent with 2.4. - Rewrote Section 3 ABNF to be consistent with 2.4.
- Rewrote examples. - Rewrote examples.
- Added reference to documentations containing LDAP-specific - Added reference to documentations containing general LDAP security
security considerations. considerations.
- Added discussion of presentation issues (Appendix A).
- Added this appendix.
In addition, numerous editorial changes were made. In addition, numerous editorial changes were made.
Copyright 2002, The Internet Society. All Rights Reserved. Copyright 2002, The Internet Society. All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published and or assist in its implementation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind, distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are provided that the above copyright notice and this paragraph are
 End of changes. 

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