draft-ietf-ldapbis-dn-08.txt   draft-ietf-ldapbis-dn-09.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 18 August 2002 Expires in six months 3 March 2003
Obsoletes: 2253 Obsoletes: 2253
LDAP: String Representation of Distinguished Names LDAP: String Representation of Distinguished Names
<draft-ietf-ldapbis-dn-08.txt> <draft-ietf-ldapbis-dn-09.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
skipping to change at page 1, line 37 skipping to change at page 1, line 37
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as ``work in progress.'' material or to cite them other than as ``work in progress.''
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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Internet-Draft Shadow Directories can be accessed at Internet-Draft Shadow Directories can be accessed at
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Copyright 2002, The Internet Society. All Rights Reserved. Copyright 2003, 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 (DNs) as primary keys to The X.500 Directory uses distinguished names (DNs) as primary keys to
entries in the directory. This document defines the string entries in the directory. This document defines the string
representation used in the Lightweight Directory Access Protocol representation used in the Lightweight Directory Access Protocol
(LDAP) to transfer distinguished names. The string representation is (LDAP) to transfer distinguished names. The string representation is
designed to give a clean representation of commonly used distinguished designed to give a clean representation of commonly used distinguished
names, while being able to represent any distinguished name. names, while being able to represent any distinguished name.
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].
1. Background and Intended Usage 1. Background and Intended Usage
In X.500-based directory systems [X.500], including those accessed In X.500-based directory systems [X.500], including those accessed
using the Lightweight Directory Access Protocol (LDAP) [LDAPTS], using the Lightweight Directory Access Protocol (LDAP) [Roadmap],
distinguished names (DNs) are used to unambiguously refer to a distinguished names (DNs) are used to unambiguously refer to a
directory entry [X.501][Models]. directory entry [X.501][Models].
The structure of a DN [X.501] is described in terms of ASN.1 [X.680]. 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 In the X.500 Directory Access Protocol [X.511] (and other ITU-defined
directory protocols), DNs are encoded using the Basic Encoding Rules directory protocols), DNs are encoded using the Basic Encoding Rules
(BER) [X.690]. In LDAP, DNs are represented in string form. (BER) [X.690]. In LDAP, DNs are represented in string form.
It is important to have a common format to be able to unambiguously It is important to have a common format to be able to unambiguously
represent a distinguished name. The primary goal of this represent a distinguished name. The primary goal of this
specification is ease of encoding and decoding. A secondary goal is specification is ease of encoding and decoding. A secondary goal is
to have names that are human readable. It is not expected that LDAP to have names that are human readable. It is not expected that LDAP
implementations with a human user interface would display these implementations with a human user interface would display these
strings directly to the user, but would most likely be performing strings directly to the user, but would most likely be performing
translations (such as expressing attribute type names in one of the translations (such as expressing attribute type names in one of the
local national languages). local national languages).
This document defines the string representation of Distinguished Names This document defines the string representation of Distinguished Names
used in LDAP [Protocol][Syntaxes]. Section 2 details how to convert a used in LDAP [Protocol][Syntaxes]. Section 2 details the RECOMMENDED
DN from ASN.1 structured representation to a string. Section 3 algorithm for converting a DN from its ASN.1 structured representation
details how to convert a DN from string to ASN.1 structured to a string. Section 3 details how to convert a DN from a string to a
representation. 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 This document does not define a canonical string representation for
DNs. Comparison of DNs for equality is to be performed in accordance DNs. Comparison of DNs for equality is to be performed in accordance
with the distinguishedNameMatch matching rule [Syntaxes]. 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 B. summarized in Appendix B.
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].
This specification assumes familiarity with X.500 [X.500], and the This specification assumes familiarity with X.500 [X.500], and the
concept of Distinguished Name [X.501][Models]. 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 [X.680] structure of distinguished name is X.501 [X.501] defines the ASN.1 [X.680] structure of distinguished
defined as: name. The following is a varient provided for discussion purposes.
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 }
This section defines the RECOMMENDED algorithm for converting a This section defines the RECOMMENDED algorithm for converting a
distinguished name from an ASN.1 structured representation to an UTF-8 distinguished name from an ASN.1 structured representation to an UTF-8
[RFC2279] encoded Universal Character Set (UCS) [ISO10646] character [RFC2279] encoded Universal Character Set (UCS) [ISO10646] character
string representation. 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 MUST be produced by
LDAP implementations.
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 Section RelativeDistinguishedName in the RDNSequence (according to Section
2.2), starting with the last element of the sequence and moving 2.2), starting with the last element of the sequence and moving
backwards 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 ("," U+0002C). a comma ("," U+002C) character.
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 Section 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 sign ("+" U+0002B) AttributeTypeAndValues are separated by a plus sign ("+" U+002B)
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 ("=" U+0003D), the AttributeType, followed by an equals ("=" U+003D) character,
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, a <descr>, associated with LDAP [Schema], then the type name string, a <descr>,
from that table is used, otherwise it is encoded as the dotted-decimal from that table is used, otherwise it is encoded as the dotted-decimal
encoding, a <numericoid>, of the AttributeType's OBJECT IDENTIFIER. encoding, a <numericoid>, of the AttributeType's OBJECT IDENTIFIER.
The <descr> and <numericoid> is defined 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.
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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)
Note: This table lists the complete set of type name strings which Note: This table lists the complete set of type name strings which all
all implementations MUST recognize in DN string representation. implementations MUST recognize in DN string representation (per
As no extension could reasonable require all existing Section 3). As no extension could reasonably require all
implementations be updated to recognize additional type name existing implementations be updated to recognize additional type
strings, this table is not extensible. name strings, this table is not extensible.
2.4. Converting an AttributeValue from ASN.1 to a String 2.4. Converting an AttributeValue from ASN.1 to a String
If the AttributeType is of the dotted-decimal form, the AttributeValue If the AttributeType is of the dotted-decimal form, the AttributeValue
is represented by an number sign character ("#" U+00023) followed by is represented by an number sign ("#" U+0023) character followed by
the hexadecimal encoding of each of the octets of the BER encoding of the hexadecimal encoding of each of the octets of the BER encoding of
the X.500 AttributeValue. This form is also used when the syntax of the X.500 AttributeValue. This form is also used when the syntax of
the AttributeValue does not have a native string encoding defined for the AttributeValue does not have a native string encoding defined for
it or the native string encoding is not restricted to UTF-8 encoded 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 UCS (or a subset of UCS) characters. This form may also be used in
other cases, such as when a reversible string representation is other cases, such as when a reversible string representation is
desired (see Section 5.2). desired (see Section 5.2).
Otherwise, if the AttributeValue is of a syntax which has a native Otherwise, if the AttributeValue is of a syntax which has a native
string encoding, the value is converted first to a UTF-8 encoded UCS string encoding, the value is converted first to a UTF-8 encoded UCS
string according to its syntax specification (see for example Section string according to its syntax specification (see for example Section
6 of [Syntaxes]). If that UTF-8 encoded UCS string does not have any 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 of the following characters which need escaping, then that string can
be used as the string representation of the value. be used as the string representation of the value.
- a space (" " U+00020) or number sign ("#" U+00023) occurring at - a space (" " U+0020) or number sign ("#" U+0023) occurring at
the beginning of the string; the beginning of the string;
- a space (" " U+00020) character occurring at the end of the - a space (" " U+0020) character occurring at the end of the
string; string;
- one of the characters """, "+", ",", ";", "<", ">", or "\" - one of the characters """, "+", ",", ";", "<", ">", or "\"
(U+00022, U+0002B, U+0002C, U+0003B, U+0003C, U+0003E, or (U+0022, U+002B, U+002C, U+003B, U+003C, U+003E, or U+005C
U+0005C respectively); respectively);
- the null (U+00000) character. - the null (U+0000) character.
Other characters may be escaped. 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 "\"
(U+00020, U+00022, U+00023, U+0002B, U+0002C, U+0003B, (U+0020, U+0022, U+0023, U+002B, U+002C, U+003B,
U+0003C, U+0003D, U+0003E, U+0005C respectively) U+003C, U+003D, U+003E, U+005C respectively)
it can be prefixed by a backslash ("\" U+00005C). it can be prefixed by a backslash ("\" U+005C).
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 string representation of Distinguished Names is restricted to The string representation of Distinguished Names is restricted to
UTF-8 [RFC2279] encoded characters from the Universal Character Set UTF-8 [RFC2279] encoded characters from the Universal Character Set
(UCS) [ISO10646]. The structure of this string representation is (UCS) [ISO10646]. The structure of this string representation is
specified using the following Augmented BNF [RFC2234] grammar using specified using the following Augmented BNF [RFC2234] grammar:
the common productions defined in [Models].
distinguishedName = [ relativeDistinguishedName distinguishedName = [ relativeDistinguishedName
*( COMMA relativeDistinguishedName ) ] *( COMMA relativeDistinguishedName ) ]
relativeDistinguishedName = attributeTypeAndValue relativeDistinguishedName = attributeTypeAndValue
*( PLUS attributeTypeAndValue ) *( PLUS attributeTypeAndValue )
attributeTypeAndValue = attributeType EQUALS attributeValue attributeTypeAndValue = attributeType EQUALS attributeValue
attributeType = descr / numericoid attributeType = descr / numericoid
attributeValue = string / hexstring attributeValue = string / hexstring
; The UTF-8 string shall not contain NULL, ESC, or ; The UTF-8 string shall not contain NULL, ESC, or
; one of escaped, shall not start with SHARP or SPACE, ; one of escaped, shall not start with SHARP or SPACE,
; and shall must not end with SPACE. ; and shall must not end with SPACE.
string = [ (leadchar / pair) string = [ (leadchar / pair)
[ *( stringchar / pair ) ( trailchar / pair ) ] ] [ *( stringchar / pair ) ( trailchar / pair ) ] ]
skipping to change at page 6, line 40 skipping to change at page 6, line 50
escaped = DQUOTE / PLUS / COMMA / SEMI / LANGLE / RANGLE escaped = DQUOTE / PLUS / COMMA / SEMI / LANGLE / RANGLE
hexstring = SHARP 1*hexpair hexstring = SHARP 1*hexpair
hexpair = HEX HEX hexpair = HEX HEX
where the productions <descr>, <numericoid>, <COMMA>, <DQUOTE>, where the productions <descr>, <numericoid>, <COMMA>, <DQUOTE>,
<EQUALS>, <ESC>, <HEX>, <LANGLE>, <NULL>, <PLUS>, <RANGLE>, <SEMI>, <EQUALS>, <ESC>, <HEX>, <LANGLE>, <NULL>, <PLUS>, <RANGLE>, <SEMI>,
<SPACE>, <SHARP>, <UTFMB> are defined in [Models]. <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 represention 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>;
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 Implementations MUST recognize AttributeType name strings
(descriptors) listed in the Section 2.3 table, but MAY recognize other (descriptors) listed in the Section 2.3 table, but MAY recognize other
name strings. Implementations MAY recognize other DN string name strings. Implementations MAY recognize other DN string
representations (such as that described in RFC 1779). However, as representations (such as that described in RFC 1779). However, as
there is no requirement for other names or alternative DN string there is no requirement for other names or alternative DN string
representations to be recognized (and, if so, how), implementations representations to be recognized (and, if so, how), implementations
SHOULD only generate DN strings in accordance with Section 2 of this SHOULD only generate DN strings in accordance with Section 2 of this
document. document.
4. Examples 4. Examples
skipping to change at page 7, line 33 skipping to change at page 8, line 17
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 UCS code UTF-8 Quoted Unicode Letter Description UCS code UTF-8 Escaped
------------------------------- -------- ------ -------- ------------------------------- -------- ------ --------
LATIN CAPITAL LETTER L U+0004C 0x4C L LATIN CAPITAL LETTER L U+004C 0x4C L
LATIN SMALL LETTER U U+00075 0x75 u LATIN SMALL LETTER U U+0075 0x75 u
LATIN SMALL LETTER C WITH CARON U+0010D 0xC48D \C4\8D LATIN SMALL LETTER C WITH CARON U+010D 0xC48D \C4\8D
LATIN SMALL LETTER I U+00069 0x69 i LATIN SMALL LETTER I U+0069 0x69 i
LATIN SMALL LETTER C WITH ACUTE U+00107 0xC487 \C4\87 LATIN SMALL LETTER C WITH ACUTE U+0107 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 24 skipping to change at page 9, line 9
- its physical location (country, locality, city, street address) - its physical location (country, locality, city, street address)
- organizational attributes (such as department name or affiliation) - organizational attributes (such as department name or affiliation)
Most countries have privacy laws regarding the publication of Most countries have privacy laws regarding the publication of
information about people. information about people.
5.2. Use of Distinguished Names in Security Applications 5.2. Use of Distinguished Names in Security Applications
The transformations of an AttributeValue value from its X.501 form to The transformations of an AttributeValue value from its X.501 form to
an LDAP string representation are not always reversible back to the an LDAP string representation are not always reversible back to the
same BER or DER form. An example of a situation which requires the same BER (Base Encoding Rules) or DER (Distinguished Encoding Rules)
DER form of a distinguished name is the verification of an X.509 form. An example of a situation which requires the DER form of a
certificate. distinguished name is the verification of an X.509 certificate.
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
skipping to change at page 9, line 7 skipping to change at page 9, line 39
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.
For example, a distinguished name consisting of one RDN with one AVA For example, a distinguished name consisting of one RDN with one AVA
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 string representation FOO=BAR is ambiguous. That is, FOO could be
attribute type 1.1.1 by one application and 1.2.3.4 in another and not recognized as the attribute type 1.1.1 by one application and 1.2.3.4
recognized by another. This may lead to operations not behaving as in another and not recognized by another. This may lead to operations
intended. not behaving as 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 names other than those in the Section 2.3 table, and while taking
Section 5.2 into consideration. Section 5.2 into consideration.
It is noted that while a registry for attribute type names It is noted that while a registry for attribute type names
(descriptors) has been established [LDAPIANA], this registry does not (descriptors) has been established [RFC3383], however this registry
remove the ambiguity of attribute types names used in LDAP. It only does not remove the ambiguity of attribute types names used in LDAP.
removes the ambiguity of attribute type names used in Standard Track
technical specifications. 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>
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).
skipping to change at page 10, line 38 skipping to change at page 11, line 22
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).
[X.690] ITU-T, "Specification of ASN.1 encoding rules: Basic, [X.690] ITU-T, "Specification of ASN.1 encoding rules: Basic,
Canonical, and Distinguished Encoding Rules", X.690, Canonical, and Distinguished Encoding Rules", X.690,
1994. 1994.
[LDAPIANA] K. Zeilenga, "IANA Considerations for LDAP", [RFC3383] K. Zeilenga, "IANA Considerations for LDAP", BCP 64 (also
draft-ietf-ldapbis-xx.txt (a work in progress). RFC 3383), September 2002.
[RFC2849] G. Good, "The LDAP Data Interchange Format (LDIF) - [RFC2849] G. Good, "The LDAP Data Interchange Format (LDIF) -
Technical Specification", RFC 2849, June 2000. Technical Specification", RFC 2849, June 2000.
Appendix A. Presentation Issues Appendix A. Presentation Issues
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 string representation described in this document is not intended The string representation described in this document is not intended
to be presented to humans without translation. However, at times it to be presented to humans without translation. However, at times it
may be desirable to present non-translated DN strings to users. This may be desirable to present non-translated DN strings to users. This
section discusses presentation issues associated with non-translated section discusses presentation issues associated with non-translated
DN strings. Presentation of translated DN strings issues are not DN strings. Presentation of translated DN strings issues are not
discussed in this document. Transcoding issues are also not discussed discussed in this appendix. Transcoding issues are also not discussed
in this document. in this appendix.
This appendix provides guidance for applications presenting DN strings This appendix provides guidance for applications presenting DN strings
to users. This section is not comprehensive, it does not discuss all to users. This section is not comprehensive, it does not discuss all
presentation issues which implementors may face. presentation issues which implementors may face.
Not all user interfaces are capable of displaying the full set of UCS Not all user interfaces are capable of displaying the full set of UCS
characters. Some UCS characters are not displayable. characters. Some UCS characters are not displayable.
It is recommended that human interfaces use the optional hex pair It is recommended that human interfaces use the optional hex pair
escaping mechanism (Section 2.3) to produce a string representation escaping mechanism (Section 2.3) to produce a string representation
suitable for display to the human. For example, an application only suitable for display to the user. For example, an application can
capable of displaying printable characters can generate a DN string generate a DN string for display which escapes all non-printable
for display which escapes all non-printable characters appearing in characters appearing in the AttributeValue's string representation (as
the AttributeValue's string representation (as demonstrated in the demonstrated in the final example of Section 4).
final example of Section 4).
When a DN string is displayed in free form text, it is necessary to When a DN string is displayed in free form text, it is often necessary
distinguish the DN string from surrounding text. While this is often to distinguish the DN string from surrounding text. While this is
done with white space (as demonstrated in Section 4), it is noted that often done with white space (as demonstrated in Section 4), it is
DN strings may end with white space. Careful readers of Section 3 noted that DN strings may end with white space. Careful readers of
will note that characters "<" and ">" may only appear in the DN string Section 3 will note that characters "<" (U+003C) and ">" (U+003E) may
if escaped. These characters are intended to be used in free form only appear in the DN string if escaped. These characters are
text to distinguish a DN string from surrounding text. For example, intended to be used in free form text to distinguish a DN string from
<CN=Sam\ > distinguished the string representation of the DN comprised surrounding text. For example, <CN=Sam\ > distinguished the string
of one RDN consisting of the AVA: the commonName (CN) value "Sam " representation of the DN comprised of one RDN consisting of the AVA:
from the surrounding text. It should be noted to the user that the the commonName (CN) value "Sam " from the surrounding text. It should
wrapping "<" and ">" characters are not part of the DN string. 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 DN strings can be quite long. It is often desirable to line-wrap
overly long DN strings in presentations. Line wrapping should be done overly long DN strings in presentations. Line wrapping should be done
by inserting white space after the RDN separator character or, if by inserting white space after the RDN separator character or, if
necessary, after the AVA separator character in such presentations. necessary, after the AVA separator character. It should be noted to
It should be noted to the user that the inserted white space is not the user that the inserted white space is not part of the DN string
part of the DN string and is to be removed before use in LDAP. For and is to be removed before use in LDAP. For example,
example,
The following DN string is long: The following DN string is long:
CN=Kurt D. Zeilenga,OU=Engineering,L=Redwood Shores, CN=Kurt D. Zeilenga,OU=Engineering,L=Redwood Shores,
O=OpenLDAP Foundation,ST=California,C=US O=OpenLDAP Foundation,ST=California,C=US
so it has been line-wrapped for readability. The extra white so it has been line-wrapped for readability. The extra white
space is to be removed the DN string is used in LDAP. space is to be removed before the DN string is used in LDAP.
It is not advised to insert white space otherwise as it may not be 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 obvious to the user which white space is part of the DN string and
white space was added for readability. which white space was added for readability.
Another alternative is to use the LDAP Data Interchange Format (LDIF) Another alternative is to use the LDAP Data Interchange Format (LDIF)
[RFC2849]. For example, [RFC2849]. For example,
The following entry has a long DN: # This entry has a long DN...
dn: CN=Kurt D. Zeilenga,OU=Engineering,L=Redwood Shores, dn: CN=Kurt D. Zeilenga,OU=Engineering,L=Redwood Shores,
O=OpenLDAP Foundation,ST=California,C=US O=OpenLDAP Foundation,ST=California,C=US
CN: Kurt D. Zeilenga CN: Kurt D. Zeilenga
SN: Zeilenga SN: Zeilenga
objectClass: person objectClass: person
It is noted that that is often desirable to replace dotted-decimal It is noted that it may be desirable to replace dotted-decimal OIDs
OIDs appearing in DN strings with attribute type names. Such appearing in DN strings with attribute type names. Such replacement
replacement is viewed as a translation and, hence, not discussed here. is viewed as a translation and, hence, not discussed here.
Appendix B. Changes made since RFC 2253 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 has been addressed. - Removed IESG Note. The IESG Note has been addressed.
- Clarified (in Section 1), that this document does not define a - Clarified (in Section 1), that this document does not define a
canonical string representation. canonical string representation.
skipping to change at page 12, line 47 skipping to change at page 13, line 31
not extensible. Added statement (in Section 3) allowing not extensible. Added statement (in Section 3) allowing
recognition of additional names. Added security considerations recognition of additional names. Added security considerations
(Section 5.3) regarding the use of other names. (Section 5.3) regarding the use of other names.
- Updated Section 2.3 to indicate attribute type name strings are - Updated Section 2.3 to indicate attribute type name strings are
case insensitive. case insensitive.
- Updated Section 2.4 to allow hex pair escaping of all characters - Updated Section 2.4 to allow hex pair escaping of all characters
and clarified escaping for when multiple octet UTF-8 characters and clarified escaping for when multiple octet UTF-8 characters
are present. 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.
- Updated Section 3 to describe how to parse elements of the
grammar.
- Rewrote examples. - Rewrote examples.
- Added reference to documentations containing general LDAP security - Added reference to documentations containing general LDAP security
considerations. considerations.
- Added discussion of presentation issues (Appendix A). - Added discussion of presentation issues (Appendix A).
- Added this appendix. - 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 2003, 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
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of Internet organizations, except as needed for the purpose of
 End of changes. 

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