Common Elements of Generic String Encoding Rules (GSER) Encodings

Abstract

The Generic String Encoding Rules (GSER) describe a human readable text encoding for an Abstract Syntax Notation One (ASN

Considerations for Lightweight Directory Access Protocol (LDAP) Extensions

“…However, any reuse MUST not alter the semantics of the element. RFC3642] or other generic string encoding rules to provide string encodings for complex ASN.1 data definitions is RECOMMENDED. Otherwise, it is RECOMMENDED that the string encoding be described using a formal language (e.g., ABNF [RFC4234]).…”

Generic String Encoding Rules (GSER) for ASN.1 Types

“…bit-list = "{" [ sp identifier *( "," sp identifier ) ] sp "}" hstring = squote *hexadecimal-digit squote %x48 ; '...'H hexadecimal-digit = %x30-39 / ; "0" to "9" %x41-46 ; "A" to "F" bstring = squote *binary-digit squote %x42 ; '...'B binary-digit = "0" / "1" sp = *%x20 ; zero, one or more space characters squote = %x27 ; ' (single quote) A value of the unrestricted CHARACTER STRING type is encoded according to the corresponding SEQUENCE type defined in Clause 40.5 of X.680 [8] (see [15] for equivalent ABNF).…”

“…A value of the EMBEDDED PDV type is encoded according to the corresponding SEQUENCE type defined in Clause 33.5 of X.680 [8] (see [15] for equivalent ABNF).…”

“…A value of the REAL type MUST be encoded as "0" if it is zero, otherwise it is encoded as the special value <PLUS-INFINITY>, the special value <MINUS-INFINITY>, an optionally signed <realnumber>, or as a value of the corresponding SEQUENCE type for REAL defined in Clause 20.5 of X.680 [8] (see [15] for equivalent ABNF). 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.…”

“…Referencing GSER is sufficient to define a human readable text encoding for values of a specific ASN.1 type, however other specifications may wish to provide a customized Augmented Backus-Naur Form (ABNF) [3] description, independent of the ASN.1, as a convenience for the implementor (equivalent ABNF for the GSER encodings for ASN.1 types commonly occurring in LDAP syntaxes is provided in a separate document [15]). Such a specification SHOULD state that if there is a discrepancy between the customized ABNF and the GSER encoding defined by this document, that the GSER encoding takes precedence.…”