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900 lines
32 KiB
Plaintext
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INTERNET-DRAFT S. Legg
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draft-legg-ldap-gser-03.txt Adacel Technologies
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Intended Category: Standard Track May 7, 2003
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Generic String Encoding Rules for ASN.1 Types
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Copyright (C) The Internet Society (2003). All Rights Reserved.
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Status of this Memo
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This document is an Internet-Draft and is in full conformance with
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all provisions of Section 10 of RFC2026.
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Internet-Drafts are working documents of the Internet Engineering
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Task Force (IETF), its areas, and its working groups. Note that
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other groups may also distribute working documents as
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Internet-Drafts.
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Internet-Drafts are draft documents valid for a maximum of six months
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and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
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material or to cite them other than as "work in progress".
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The list of current Internet-Drafts can be accessed at
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http://www.ietf.org/ietf/1id-abstracts.txt
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The list of Internet-Draft Shadow Directories can be accessed at
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http://www.ietf.org/shadow.html.
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Distribution of this document is unlimited. Comments should be sent
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to the LDAPEXT working group mailing list <ietf-ldapext@netscape.com>
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or to the author.
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This Internet-Draft expires on 7 November 2003.
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Abstract
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This document defines a set of Abstract Syntax Notation One (ASN.1)
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encoding rules, called the Generic String Encoding Rules, that
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produce a human readable text encoding for values of any given ASN.1
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data type.
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Legg Expires 7 November 2003 [Page 1]
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INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
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1. Table of Contents
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1. Table of Contents ............................................. 2
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2. Introduction .................................................. 2
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3. Conventions ................................................... 3
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4. Generic String Encoding Rules ................................. 3
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4.1 Type Referencing Notations ................................ 4
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4.2 Restricted Character String Types ......................... 4
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4.3 ChoiceOfStrings Types ..................................... 5
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4.4 Identifiers ............................................... 7
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4.5 BIT STRING ................................................ 7
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4.6 BOOLEAN ................................................... 8
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4.7 ENUMERATED ................................................ 8
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4.8 INTEGER ................................................... 8
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4.9 NULL ...................................................... 8
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4.10 OBJECT IDENTIFIER and RELATIVE-OID ....................... 9
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4.11 OCTET STRING ............................................. 9
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4.12 CHOICE ................................................... 9
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4.13 SEQUENCE and SET ......................................... 10
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4.14 SEQUENCE OF and SET OF ................................... 11
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4.15 CHARACTER STRING ......................................... 11
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4.16 EMBEDDED PDV ............................................. 11
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4.17 EXTERNAL ................................................. 11
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4.18 INSTANCE OF .............................................. 12
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4.19 REAL ..................................................... 12
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4.20 Variant Encodings ........................................ 12
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5. GSER Transfer Syntax .......................................... 13
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6. Security Considerations ....................................... 13
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7. Normative References .......................................... 14
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8. Informative References ........................................ 15
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9. Copyright Notice .............................................. 15
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10. Author's Address ............................................. 16
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2. Introduction
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This document defines a set of ASN.1 [8] encoding rules, called the
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Generic String Encoding Rules or GSER, that produce a human readable
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UTF8 [6] character string encoding of ASN.1 values of any given
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arbitrary ASN.1 type.
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Note that "ASN.1 value" does not mean a BER [13] encoded value. The
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ASN.1 value is an abstract concept that is independent of any
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particular encoding. BER is just one possible encoding of an ASN.1
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value.
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GSER is based on ASN.1 value notation [8], with changes to
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accommodate the notation's use as a transfer syntax, and to support
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Legg Expires 7 November 2003 [Page 2]
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INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
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well established ad-hoc string encodings for LDAP [14] directory data
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types.
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Though primarily intended for defining the LDAP-specific encoding of
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new LDAP attribute syntaxes and assertion syntaxes, these encoding
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rules could also be used in other domains where human readable
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renderings of ASN.1 values would be useful.
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Referencing the Generic String Encoding Rules (GSER) is sufficient to
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define a human readable text encoding for values of a specific ASN.1
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type, however other specifications may wish to provide a customized
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ABNF [3] description, independent of the ASN.1, as a convenience for
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the implementor (equivalent ABNF for the GSER encodings for ASN.1
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types commonly occuring in LDAP syntaxes is provided in [15]). Such
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a specification SHOULD state that if there is a discrepancy between
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the customized ABNF and the GSER encoding defined by this document,
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that the GSER encoding takes precedence.
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3. Conventions
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Throughout this document "type" shall be taken to mean an ASN.1 type,
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and "value" shall be taken to mean an ASN.1 value.
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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document are to be interpreted as described in RFC 2119 [1].
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4. Generic String Encoding Rules
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The GSER encoding of a value of any ASN.1 type is described by the
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following ABNF [3]:
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Value = BitStringValue /
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BooleanValue /
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CharacterStringValue /
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ChoiceValue /
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EmbeddedPDVValue /
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EnumeratedValue /
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ExternalValue /
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GeneralizedTimeValue /
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IntegerValue /
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InstanceOfValue /
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NullValue /
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ObjectDescriptorValue /
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ObjectIdentifierValue /
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OctetStringValue /
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Legg Expires 7 November 2003 [Page 3]
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INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
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RealValue /
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RelativeOIDValue /
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SequenceOfValue /
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SequenceValue /
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SetOfValue /
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SetValue /
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StringValue /
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UTCTimeValue /
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VariantEncoding
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The ABNF for each of the above rules is given in the following
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sections.
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4.1 Type Referencing Notations
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A value of a type with a defined type name is encoded according to
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the type definition on the right hand side of the type assignment for
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the type name.
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A value of a type denoted by the use of a parameterized type with
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actual parameters is encoded according to the parameterized type with
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the DummyReferences [12] substituted with the actual parameters.
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A value of a tagged or constrained type is encoded as a value of the
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type without the tag or constraint, respectively. Tags do not appear
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in the string encodings defined by this document. See [8] and [11]
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for the details of ASN.1 constraint notation.
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A value of an open type denoted by an ObjectClassFieldType (Clause 14
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of [10]) is encoded according to the specific type of the value.
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A value of a fixed type denoted by an ObjectClassFieldType is encoded
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according to that fixed type.
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A value of a selection type is encoded according to the type
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referenced by the selection type.
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A value of a type described by TypeFromObject notation (Clause 15 of
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[10]) is encoded according to the denoted type.
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A value of a type described by ValueSetFromObjects notation (Clause
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15 of [10]) is encoded according to the governing type.
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4.2 Restricted Character String Types
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The contents of a string value are encoded as a UTF8 character string
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Legg Expires 7 November 2003 [Page 4]
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INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
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between double quotes, regardless of the ASN.1 string type.
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Depending on the ASN.1 string type, and an application's internal
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representation of that string type, a translation to or from the UTF8
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character encoding may be required. NumericString, PrintableString,
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IA5String, VisibleString (ISO646String) are compatible with UTF8 and
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do not require any translation. BMPString (UCS-2) and
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UniversalString (UCS-4) have a direct mapping to and from UTF8 [6].
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For the remaining string types see [8]. Any embedded double quotes
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in the resulting UTF8 character string are escaped by repeating the
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double quote characters.
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A value of the NumericString, PrintableString, TeletexString
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(T61String), VideotexString, IA5String, GraphicString, VisibleString
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(ISO646String), GeneralString, BMPString, UniversalString or
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UTF8String type is encoded according to the <StringValue> rule.
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StringValue = dquote *SafeUTF8Character dquote
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dquote = %x22 ; " (double quote)
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SafeUTF8Character = %x00-21 / %x23-7F / ; ASCII minus dquote
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dquote dquote / ; escaped double quote
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%xC0-DF %x80-BF / ; 2 byte UTF8 character
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%xE0-EF 2(%x80-BF) / ; 3 byte UTF8 character
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%xF0-F7 3(%x80-BF) / ; 4 byte UTF8 character
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%xF8-FB 4(%x80-BF) / ; 5 byte UTF8 character
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%xFC-FD 5(%x80-BF) ; 6 byte UTF8 character
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A value of the GeneralizedTime type, UTCTime type or ObjectDescriptor
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type is encoded as a string value. GeneralizedTime and UTCTime use
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the VisibleString character set so the conversion to UTF8 is trivial.
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ObjectDescriptor uses the GraphicString type.
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GeneralizedTimeValue = StringValue
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UTCTimeValue = StringValue
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ObjectDescriptorValue = StringValue
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4.3 ChoiceOfStrings Types
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It is not uncommon for ASN.1 specifications to define types that are
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a CHOICE between two or more alternative ASN.1 string types, where
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the particular alternative chosen carries no semantic significance
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(DirectoryString [7] being a prime example). Such types are defined
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to avoid having to use a complicated character encoding for all
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values when most values could use a simpler string type, or to deal
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with evolving requirements that compel the use of a broader character
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set while still maintaining backward compatibility.
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Legg Expires 7 November 2003 [Page 5]
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INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
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GSER encodes values of all the ASN.1 string types as UTF8 character
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strings so the alternative chosen in a purely syntactic CHOICE of
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string types makes no material difference to the final encoding of
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the string value.
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While there are certain ASN.1 constructs that betray the semantic
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significance of the alternatives within a CHOICE type, the absence of
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those constructs does not necessarily mean a CHOICE type is purely
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syntactic. Therefore, it is necessary for specifications to declare
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the purely syntactic CHOICE types so that they may be more compactly
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encoded (see Section 4.12). These declared CHOICE types are referred
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to as ChoiceOfStrings types.
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To be eligible to be declared a ChoiceOfStrings type an ASN.1 type
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MUST satisfy the following conditions.
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a) The type is a CHOICE type.
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b) The component type of each alternative is one of the following
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ASN.1 restricted string types: NumericString, PrintableString,
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TeletexString (T61String), VideotexString, IA5String,
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GraphicString, VisibleString (ISO646String), GeneralString,
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BMPString, UniversalString or UTF8String.
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c) All the alternatives are of different restricted string types,
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i.e. no two alternatives have the same ASN.1 restricted string
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type.
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d) Either none of the alternatives has a constraint, or all of the
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alternatives have exactly the same constraint.
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Tagging on the alternative types is ignored.
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Consider the ASN.1 parameterized type definition of DirectoryString.
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DirectoryString { INTEGER : maxSize } ::= CHOICE {
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teletexString TeletexString (SIZE (1..maxSize)),
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printableString PrintableString (SIZE (1..maxSize)),
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bmpString BMPString (SIZE (1..maxSize)),
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universalString UniversalString (SIZE (1..maxSize)),
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uTF8String UTF8String (SIZE (1..maxSize)) }
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Any use of the DirectoryString parameterized type with an actual
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parameter defines a ASN.1 type that satisfies the above conditions.
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Recognising that the alternative within a DirectoryString carries no
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semantic significance, this document declares (each and every use of)
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DirectoryString{} to be a ChoiceOfStrings type.
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Legg Expires 7 November 2003 [Page 6]
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INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
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Other specifications MAY declare other types satisfying the above
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conditions to be ChoiceOfStrings types. The declaration SHOULD be
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made at the point where the ASN.1 type is defined, otherwise it
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SHOULD be made at the point where it is introduced as, or in, an LDAP
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attribute or assertion syntax.
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4.4 Identifiers
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An <identifier> conforms to the definition of an identifier in ASN.1
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notation (Clause 11.3 of [8]). It begins with a lowercase letter and
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is followed by zero or more letters, digits, and hyphens. A hyphen
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is not permitted to be the last character and a hyphen is not
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permitted to be followed by another hyphen. The case of letters in
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an identifier is always significant.
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identifier = lowercase *alphanumeric *(hyphen 1*alphanumeric)
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alphanumeric = uppercase / lowercase / decimal-digit
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uppercase = %x41-5A ; "A" to "Z"
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lowercase = %x61-7A ; "a" to "z"
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decimal-digit = %x30-39 ; "0" to "9"
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hyphen = "-"
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4.5 BIT STRING
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A value of the BIT STRING type is encoded according to the
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<BitStringValue> rule. If the definition of the BIT STRING type
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includes a named bit list, the <bit-list> form of <BitStringValue>
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MAY be used. If the number of bits in a BIT STRING value is a
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multiple of four the <hstring> form of <BitStringValue> MAY be used.
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The <bstring> form of <BitStringValue> is used otherwise.
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BitStringValue = bstring / hstring / bit-list
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The <bit-list> rule encodes the one bits in the bit string value as a
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comma separated list of identifiers. Each <identifier> MUST be one
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of those in the named bit list. An <identifier> MUST NOT appear more
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than once in the same <bit-list>. The <bstring> rule encodes each
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bit as the character "0" or "1" in order from the first bit to the
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last bit. The <hstring> rule encodes each group of four bits as a
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hexadecimal number where the first bit is the most significant. An
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odd number of hexadecimal digits is permitted.
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bit-list = "{" [ sp identifier
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*( "," sp identifier ) ] sp "}"
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hstring = squote *hexadecimal-digit squote %x48 ; '...'H
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Legg Expires 7 November 2003 [Page 7]
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INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
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hexadecimal-digit = %x30-39 / ; "0" to "9"
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%x41-46 ; "A" to "F"
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bstring = squote *binary-digit squote %x42 ; '...'B
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binary-digit = "0" / "1"
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sp = *%x20 ; zero, one or more space characters
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squote = %x27 ; ' (single quote)
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4.6 BOOLEAN
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A value of the BOOLEAN type is encoded according to the
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<BooleanValue> rule.
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BooleanValue = %x54.52.55.45 / ; "TRUE"
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%x46.41.4C.53.45 ; "FALSE"
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4.7 ENUMERATED
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A value of the ENUMERATED type is encoded according to the
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<EnumeratedValue> rule. The <identifier> MUST be one of those in the
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list of enumerations in the definition of the ENUMERATED type.
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EnumeratedValue = identifier
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4.8 INTEGER
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A value of the INTEGER type is encoded according to the
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<IntegerValue> rule. If the definition of the INTEGER type includes
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a named number list, the <identifier> form of <IntegerValue> MAY be
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used, in which case the <identifier> MUST be one of those in the
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named number list.
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IntegerValue = "0" /
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positive-number /
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("-" positive-number) /
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identifier
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positive-number = non-zero-digit *decimal-digit
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non-zero-digit = %x31-39 ; "1" to "9"
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4.9 NULL
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A value of the NULL type is encoded according to the <NullValue>
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Legg Expires 7 November 2003 [Page 8]
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INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
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rule.
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NullValue = %x4E.55.4C.4C ; "NULL"
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4.10 OBJECT IDENTIFIER and RELATIVE-OID
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A value of the OBJECT IDENTIFIER type is encoded according to the
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<ObjectIdentifierValue> rule. The <ObjectIdentifierValue> rule
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allows either a dotted decimal representation of the OBJECT
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IDENTIFIER value or an object descriptor name, i.e. <descr>. The
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<descr> rule is described in [4]. An object descriptor name is
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potentially ambiguous and should be used with care.
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ObjectIdentifierValue = numeric-oid / descr
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numeric-oid = oid-component 1*( "." oid-component )
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oid-component = "0" / positive-number
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A value of the RELATIVE-OID [9] type is encoded according to the
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<RelativeOIDValue> rule.
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RelativeOIDValue = oid-component *( "." oid-component )
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4.11 OCTET STRING
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A value of the OCTET STRING type is encoded according to the
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<OctetStringValue> rule. The octets are encoded in order from the
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first octet to the last octet. Each octet is encoded as a pair of
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hexadecimal digits where the first digit corresponds to the four most
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significant bits of the octet. If the hexadecimal string does not
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have an even number of digits the four least significant bits in the
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last octet are assumed to be zero.
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OctetStringValue = hstring
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4.12 CHOICE
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A value of a CHOICE type is encoded according to the <ChoiceValue>
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rule. The <ChoiceOfStringsValue> encoding MAY be used if the
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corresponding CHOICE type has been declared a ChoiceOfStrings type.
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This document declares DirectoryString to be a ChoiceOfStrings type
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(see Section 4.3). The <IdentifiedChoiceValue> form of <ChoiceValue>
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is used otherwise.
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ChoiceValue = IdentifiedChoiceValue /
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ChoiceOfStringsValue
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Legg Expires 7 November 2003 [Page 9]
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INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
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IdentifiedChoiceValue = identifier ":" Value
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ChoiceOfStringsValue = StringValue
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For implementations that recognise the internal structure of the
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DirectoryString CHOICE type (e.g. X.500 directories [16]), if the
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character string between the quotes in a <StringValue> contains only
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characters that are permitted in a PrintableString the
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DirectoryString is assumed to use the printableString alternative,
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otherwise it is assumed to use the uTF8String alternative. The
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<IdentifiedChoiceValue> rule MAY be used for a value of type
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DirectoryString to indicate a different alternative to the one that
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would otherwise be assumed from the string contents. No matter what
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alternative is chosen, the <Value> will still be a UTF8 encoded
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character string, however it is a syntax error if the characters in
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the UTF8 string cannot be represented in the string type of the
|
||
chosen alternative.
|
||
|
||
Implementations that don't care about the internal structure of a
|
||
DirectoryString value MUST be able to parse the
|
||
<IdentifiedChoiceValue> form for a DirectoryString value, though the
|
||
particular identifier found will be of no interest.
|
||
|
||
4.13 SEQUENCE and SET
|
||
|
||
A value of a SEQUENCE type is encoded according to the
|
||
<SequenceValue> rule. The <ComponentList> rule encodes a comma
|
||
separated list of the particular component values present in the
|
||
SEQUENCE value, where each component value is preceded by the
|
||
corresponding identifier from the SEQUENCE type definition. The
|
||
components are encoded in the order of their definition in the
|
||
SEQUENCE type.
|
||
|
||
SequenceValue = ComponentList
|
||
|
||
ComponentList = "{" [ sp NamedValue *( "," sp NamedValue) ] sp "}"
|
||
NamedValue = identifier msp Value
|
||
msp = 1*%x20 ; one or more space characters
|
||
|
||
A value of a SET type is encoded according to the <SetValue> rule.
|
||
The components are encoded in the order of their definition in
|
||
the SET type (i.e. just like a SEQUENCE value).
|
||
This is a deliberate departure from ASN.1 value notation where
|
||
the components of a SET can be written in any order.
|
||
|
||
SetValue = ComponentList
|
||
|
||
SEQUENCE and SET type definitions are sometimes extended by the
|
||
inclusion of additional component types, so an implementation SHOULD
|
||
|
||
|
||
|
||
Legg Expires 7 November 2003 [Page 10]
|
||
|
||
INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
|
||
|
||
|
||
be capable of skipping over any <NamedValue> encoding with an
|
||
identifier that is not recognised, on the assumption that the sender
|
||
is using a more recent definition of the SEQUENCE or SET type.
|
||
|
||
|
||
4.14 SEQUENCE OF and SET OF
|
||
|
||
A value of a SEQUENCE OF type is encoded according to the
|
||
<SequenceOfValue> rule, as a comma separated list of the instances in
|
||
the value. Each instance is encoded according to the component type
|
||
of the SEQUENCE OF type.
|
||
|
||
SequenceOfValue = "{" [ sp Value *( "," sp Value) ] sp "}"
|
||
|
||
A value of a SET OF type is encoded according to the <SetOfValue>
|
||
rule, as a list of the instances in the value. Each instance is
|
||
encoded according to the component type of the SET OF type.
|
||
|
||
SetOfValue = "{" [ sp Value *( "," sp Value) ] sp "}"
|
||
|
||
|
||
4.15 CHARACTER STRING
|
||
|
||
A value of the unrestricted CHARACTER STRING type is encoded
|
||
according to the corresponding SEQUENCE type defined in Clause 39.5
|
||
of [8] (see [15] for equivalent ABNF).
|
||
|
||
CharacterStringValue = SequenceValue
|
||
|
||
|
||
4.16 EMBEDDED PDV
|
||
|
||
A value of the EMBEDDED PDV type is encoded according to the
|
||
corresponding SEQUENCE type defined in Clause 32.5 of [8] (see [15]
|
||
for equivalent ABNF).
|
||
|
||
EmbeddedPDVValue = SequenceValue
|
||
|
||
|
||
4.17 EXTERNAL
|
||
|
||
A value of the EXTERNAL type is encoded according to the
|
||
corresponding SEQUENCE type defined in Clause 8.18.1 of [13] (see
|
||
[15] for equivalent ABNF).
|
||
|
||
ExternalValue = SequenceValue
|
||
|
||
|
||
|
||
|
||
|
||
Legg Expires 7 November 2003 [Page 11]
|
||
|
||
INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
|
||
|
||
|
||
4.18 INSTANCE OF
|
||
|
||
A value of the INSTANCE OF type is encoded according to the
|
||
corresponding SEQUENCE type defined in Annex C of [10].
|
||
|
||
InstanceOfValue = SequenceValue
|
||
|
||
|
||
4.19 REAL
|
||
|
||
A value of the REAL type MUST be encoded as "0" if it is zero,
|
||
otherwise it is encoded as either the special value <PLUS-INFINITY>,
|
||
the special value <MINUS-INFINITY>, an optionally signed <realnumber>
|
||
(based on the extended value notation for REAL from [17]) or as a
|
||
value of the corresponding SEQUENCE type for REAL defined in Clause
|
||
20.5 of [8] (see [15] for equivalent ABNF).
|
||
|
||
RealValue = "0" ; zero REAL value
|
||
/ PLUS-INFINITY ; positive infinity
|
||
/ MINUS-INFINITY ; negative infinity
|
||
/ realnumber ; positive base 10 REAL value
|
||
/ "-" realnumber ; negative base 10 REAL value
|
||
/ SequenceValue ; non-zero REAL value, base 2 or 10
|
||
realnumber = mantissa exponent
|
||
mantissa = (positive-number [ "." *decimal-digit ])
|
||
/ ( "0." *("0") positive-number )
|
||
exponent = "E" ( "0" / ([ "-" ] positive-number))
|
||
|
||
PLUS-INFINITY = %x50.4C.55.53.2D.49.4E.46.49.4E.49.54.59
|
||
; "PLUS-INFINITY"
|
||
MINUS-INFINITY = %x4D.49.4E.55.53.2D.49.4E.46.49.4E.49.54.59
|
||
; "MINUS-INFINITY"
|
||
|
||
|
||
4.20 Variant Encodings
|
||
|
||
The values of some named complex ASN.1 types have special string
|
||
encodings. These special encodings are always used instead of the
|
||
encoding that would otherwise apply based on the ASN.1 type
|
||
definition.
|
||
|
||
VariantEncoding = RDNSequenceValue /
|
||
RelativeDistinguishedNameValue /
|
||
ORAddressValue
|
||
|
||
A value of the RDNSequence type, i.e. a distinguished name, is
|
||
encoded according to the <RDNSequenceValue> rule, as a quoted LDAPDN
|
||
character string. The character string is first derived according to
|
||
|
||
|
||
|
||
Legg Expires 7 November 2003 [Page 12]
|
||
|
||
INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
|
||
|
||
|
||
the <distinguishedName> rule in Section 3 of [5], and then it is
|
||
encoded as if it were a UTF8String value, i.e. between double quotes
|
||
with any embedded double quotes escaped by being repeated.
|
||
|
||
RDNSequenceValue = StringValue
|
||
|
||
A RelativeDistinguishedName value that is not part of an RDNSequence
|
||
value is encoded according to the <RelativeDistinguishedNameValue>
|
||
rule as a quoted character string. The character string is first
|
||
derived according to the <name-component> rule in Section 3 of [5],
|
||
and then it is encoded as if it were a UTF8String value.
|
||
|
||
RelativeDistinguishedNameValue = StringValue
|
||
|
||
A value of the ORAddress type is encoded according to the
|
||
<ORAddressValue> rule as a quoted character string. The character
|
||
string is first derived according to the textual representation of
|
||
MTS.ORAddress from [2], and then it is encoded as if it were an
|
||
IA5String value.
|
||
|
||
ORAddressValue = StringValue
|
||
|
||
|
||
5. GSER Transfer Syntax
|
||
|
||
The following OBJECT IDENTIFIER has been assigned to identify the
|
||
Generic String Encoding Rules:
|
||
|
||
{ 1 2 36 79672281 0 0 }
|
||
|
||
This OBJECT IDENTIFIER would be used, for example, to describe the
|
||
transfer syntax for a GSER encoded data-value in an EMBEDDED PDV
|
||
value.
|
||
|
||
|
||
6. Security Considerations
|
||
|
||
The Generic String Encoding Rules do not define a canonical encoding.
|
||
That is, a transformation from a GSER encoding into some other
|
||
encoding (e.g. BER) and back into GSER will not necessarily reproduce
|
||
exactly the original GSER octet encoding. Therefore GSER SHOULD NOT
|
||
be used where a canonical encoding is needed.
|
||
|
||
Furthermore, GSER does not necessarily enable the exact octet
|
||
encoding of values of the TeletexString, VideotexString,
|
||
GraphicString or GeneralString types to be reconstructed, so a
|
||
transformation from DER to GSER and back to DER may not reproduce the
|
||
original DER encoding. Therefore GSER SHOULD NOT be used where
|
||
|
||
|
||
|
||
Legg Expires 7 November 2003 [Page 13]
|
||
|
||
INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
|
||
|
||
|
||
reversibility to DER is needed, e.g. for the verification of digital
|
||
signatures. Instead, DER or a DER-reversible encoding should be
|
||
used.
|
||
|
||
When interpreting security-sensitive fields, and in particular fields
|
||
used to grant or deny access, implementations MUST ensure that any
|
||
comparisons are done on the underlying abstract value, regardless of
|
||
the particular encoding used.
|
||
|
||
|
||
7. Normative References
|
||
|
||
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
|
||
Levels", BCP 14, RFC 2119, March 1997.
|
||
|
||
[2] Kille, S., "MIXER (Mime Internet X.400 Enhanced Relay): Mapping
|
||
between X.400 and RFC 822/MIME", RFC 2156, January 1998.
|
||
|
||
[3] Crocker, D. and P. Overell, "Augmented BNF for Syntax
|
||
Specifications: ABNF", RFC 2234, November 1997.
|
||
|
||
[4] Wahl, M., Coulbeck, A., Howes, T. and S. Kille, "Lightweight
|
||
Directory Access Protocol (v3): Attribute Syntax Definitions",
|
||
RFC 2252, December 1997.
|
||
|
||
[5] Wahl, M., Kille S. and T. Howes. "Lightweight Directory Access
|
||
Protocol (v3): UTF-8 String Representation of Distinguished
|
||
Names", RFC 2253, December 1997.
|
||
|
||
[6] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC
|
||
2279, January 1998.
|
||
|
||
[7] ITU-T Recommendation X.520 (1993) | ISO/IEC 9594-6:1994,
|
||
Information Technology - Open Systems Interconnection - The
|
||
Directory: Selected attribute types
|
||
|
||
[8] ITU-T Recommendation X.680 (1997) | ISO/IEC 8824-1:1998
|
||
Information Technology - Abstract Syntax Notation One (ASN.1):
|
||
Specification of basic notation
|
||
|
||
[9] ITU-T Recommendation X.680 - Amendment 1 (06/99) | ISO/IEC
|
||
8824-1:1998/Amd 1:2000 Relative object identifiers
|
||
|
||
[10] ITU-T Recommendation X.681 (1997) | ISO/IEC 8824-2:1998
|
||
Information Technology - Abstract Syntax Notation One (ASN.1):
|
||
Information object specification
|
||
|
||
[11] ITU-T Recommendation X.682 (1997) | ISO/IEC 8824-3:1998
|
||
|
||
|
||
|
||
Legg Expires 7 November 2003 [Page 14]
|
||
|
||
INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
|
||
|
||
|
||
Information Technology - Abstract Syntax Notation One (ASN.1):
|
||
Constraint specification
|
||
|
||
[12] ITU-T Recommendation X.683 (1997) | ISO/IEC 8824-4:1998
|
||
Information Technology - Abstract Syntax Notation One (ASN.1):
|
||
Parameterization of ASN.1 specifications
|
||
|
||
[13] ITU-T Recommendation X.690 (1997) | ISO/IEC 8825-1:1998
|
||
Information Technology - ASN.1 encoding rules: Specification of
|
||
Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and
|
||
Distinguished Encoding Rules (DER)
|
||
|
||
|
||
8. Informative References
|
||
|
||
[14] Hodges, J. and R. Morgan, "Lightweight Directory Access
|
||
Protocol (v3): Technical Specification", RFC 3377, September
|
||
2002.
|
||
|
||
[15] Legg, S., "Common Elements of GSER Encodings",
|
||
draft-legg-ldap-gser-abnf-xx.txt, a work in progress, May 2003.
|
||
|
||
[16] ITU-T Recommendation X.500 (1993) | ISO/IEC 9594-1:1994,
|
||
Information Technology - Open Systems Interconnection - The
|
||
Directory: Overview of concepts, models and services
|
||
|
||
[17] ITU-T Recommendation X.680 - Corrigendum 3 (02/2001)
|
||
|
||
|
||
9. Copyright Notice
|
||
|
||
Copyright (C) The Internet Society (2003). All Rights Reserved.
|
||
|
||
This document and translations of it may be copied and furnished to
|
||
others, and derivative works that comment on or otherwise explain it
|
||
or assist in its implementation may be prepared, copied, published
|
||
and distributed, in whole or in part, without restriction of any
|
||
kind, provided that the above copyright notice and this paragraph are
|
||
included on all such copies and derivative works. However, this
|
||
document itself may not be modified in any way, such as by removing
|
||
the copyright notice or references to the Internet Society or other
|
||
Internet organizations, except as needed for the purpose of
|
||
developing Internet standards in which case the procedures for
|
||
copyrights defined in the Internet Standards process must be
|
||
followed, or as required to translate it into languages other than
|
||
English.
|
||
|
||
The limited permissions granted above are perpetual and will not be
|
||
|
||
|
||
|
||
Legg Expires 7 November 2003 [Page 15]
|
||
|
||
INTERNET-DRAFT Generic String Encoding Rules May 7, 2003
|
||
|
||
|
||
revoked by the Internet Society or its successors or assigns.
|
||
|
||
This document and the information contained herein is provided on an
|
||
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
|
||
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
|
||
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
|
||
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
|
||
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
|
||
|
||
|
||
10. Author's Address
|
||
|
||
Steven Legg
|
||
Adacel Technologies Ltd.
|
||
250 Bay Street
|
||
Brighton, Victoria 3186
|
||
AUSTRALIA
|
||
|
||
Phone: +61 3 8530 7710
|
||
Fax: +61 3 8530 7888
|
||
EMail: steven.legg@adacel.com.au
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Legg Expires 7 November 2003 [Page 16]
|
||
|