来自PKCS＃9的双重约束语法是否合法？

Question

在PKCS＃9标准中，他们有以下任务。第一行定义了一个PrintableString类型，它只能有两个字符长，并且必须是ISO / IEC3166中定义的两个字母的国家首字母缩略词之一。用于定义此约束的语法是两个独立的约束，但是在查看ASN.1标准时，只能有一个“根”约束。 PKCS＃9标准中使用的语法是否不正确？

countryOfResidence ATTRIBUTE ::= {
    WITH SYNTAX PrintableString (SIZE(2))(CONSTRAINED BY {
    -- Must be a two-letter country acronym in accordance with
    -- ISO/IEC 3166 --})
    EQUALITY MATCHING RULE caseIgnoreMatch
    ID pkcs-9-at-countryOfResidence
}

ATTRIBUTE ::= CLASS {
  &derivation            ATTRIBUTE OPTIONAL,
  &Type                  OPTIONAL, -- either &Type or &derivation required
  &equality-match        MATCHING-RULE OPTIONAL,
  &ordering-match        MATCHING-RULE OPTIONAL,
  &substrings-match      MATCHING-RULE OPTIONAL,
  &single-valued         BOOLEAN DEFAULT FALSE,
  &collective            BOOLEAN DEFAULT FALSE,
  &dummy                 BOOLEAN DEFAULT FALSE,
  -- operational extensions
  &no-user-modification  BOOLEAN DEFAULT FALSE,
  &usage                 AttributeUsage DEFAULT userApplications,
  &id                    OBJECT IDENTIFIER UNIQUE
}
WITH SYNTAX {
  [SUBTYPE OF &derivation]
  [WITH SYNTAX &Type]
  [EQUALITY MATCHING RULE &equality-match]
  [ORDERING MATCHING RULE &ordering-match]
  [SUBSTRINGS MATCHING RULE &substrings-match]
  [SINGLE VALUE &single-valued]
  [COLLECTIVE &collective]
  [DUMMY &dummy]
  [NO USER MODIFICATION &no-user-modification]
  [USAGE &usage]
  ID &id
}

ASN.1 Production (Found in ISO/IEC 8824-1:2015 / Rec. ITU-T X.680 (08/2015) page. 87)

ConstrainedType ::=
    Type Constraint
    | TypeWithConstraint

Constraint ::= "(" ConstraintSpec ExceptionSpec ")"
ConstraintSpec ::=
    SubtypeConstraint
    | GeneralConstraint

Answer 1

约束可以连续应用。这是合法的。您要添加约束的“类型”本身可以是“ConstrainedType”。