asn.1.rs

ASN.1 parser written in rust.

Usage

asn1rs [OPTIONS] <FILES>...

Features

The defined feature options of the compiler are shown below. All of the features are enabled by default. To disable all of the default features and strictly comply with the ASN.1 standards, strict mode can be enabled using -s. Features can then be specified on the command line using -f <feature name>.

• lowercase-keywords: Allows a version of all keywords to be accepted that does not require all letters to be uppercase. It the keyword already contains lowercase letters, no changes are allowed. If the keyword is used as a type reference, it will be transformed into PascalCase (Upper camel case). Otherwise it shall be all lower case. These transformed keywords will be allowed alongside the standard ones, not as a replacement.
• unicode-identifiers: Allows the parser to recognise identifiers that contain additional characters beyond the specified ones in the standard. A summery of the ITU-T standard specification for ASN.1 is that identifiers are to be sequences of characters that will match the regular expression [A-Za-z][A-Za-z0-9_$\-]*. This feature extends the definition of identifiers as specified in the "Compliance with UAX#31" section below. Note that for determining whether identifiers start with upper or lower case letters, any code point that is not upper case will be considered as lower case. This makes all symbols lower case. See UAX31-R4 below for more detail.
• unicode-whitespace: Allows the use of all unicode whitespace characters within source code. By default only the following characters are treated as whitespace: horizontal tabulation, line feed, vertical tabulation, form feed, carriage return, space, no-break space.

Standards

• ITU-T X.680 (02/2021) Information technology - Abstract Syntax Notation One (ASN.1): Specification of basic notation
• ITU-T X.681 (02/2021) Information technology - Abstract Syntax Notation One (ASN.1): Information object specification
• ITU-T X.682 (02/2021) Information technology - Abstract Syntax Notation One (ASN.1): Constraint specification
• ITU-T X.683 (02/2021) Information technology - Abstract Syntax Notation One (ASN.1): Parameterization of ASN.1 specifications

Secondary References

• ITU-T X.660 (07/2011) Information technology – Procedures for the operation of object identifier registration authorities: General procedures and top arcs of the international object identifier tree
• RFC 3987 Internationalized Resource Identifiers (IRIs)
• RFC 5891 Internationalized Domain Names in Applications (IDNA): Protocol
• The Unicode Standard, Version 15.1.0
  • The Unicode Standard is used in all places within other standards instead of ISO/IEC 10646. This should not affect the behaviour of any input as the two standards are compatible.

Limitations:

The following deviations from standards are made within this parser:

• X.680 OID-IRI values are specified with double quote tokens as their own production that is separate from character strings, however it is ambiguous whether a given double quote should be parsed as a character string or an OID-IRI until typechecking.

  The example included below is ambiguous in the standard, as it could be parsed as either the assignment of character strings to both of Foo and Bar or alternatively it could be the assignment of one OID-IRI value containing a multi-line comment to Foo.

  Foo MyType ::= "/a /*comment"
  Bar MyType ::= "*//b"

  This ambiguity cannot be resolved until MyType is resolved to either a character string type or an OID-IRI. Therefore, this parser has taken the decision to always parse the above example as two assignments of character string literals and never as an OID-IRI value containing a multi-line comment.

Unicode

This program aims to comply with the requirements within the Unicode Standard, Version 15.1.0.

• The only accepted source code input encoding is UTF-8. Any other encoding should be converted to UTF-8 prior to processing with this program.
• Any reference to characters within this program and its documentation should be taken to mean Unicode Code Point.
• If the first character of a source file is the byte order mark (U+FEFF) then it will be ignored. It will not be ignored in any other locations within a source file.

This program aims to comply with the requirements for identifiers, as specified in Version 15.1.0 of the Unicode Standard. See Unicode Standard Annex #31, “Unicode Identifiers and Syntax” (https://www.unicode.org/reports/tr31/tr31-39.html).

• UAX31-R1 Default Identifiers: Complied with, using a profile as follows:

  • Start := XID_Start plus the characters $ (U+0024) and _ (U+005F)
  • Continue := XID_Continue plus the characters $ (U+0024), _ (U+005F), Hyphen (U+2010) and Hyphen-Minus (U+002D)
  • Medial := empty

  With the following exceptions:

  • No identifiers can end with a hyphen character.
  • No identifiers can contain two consecutive hyphens.

• UAX31-R1b Stable Identifiers: Not complied with. No stability guarantees are made beyond that which are made in UAX31-R1.

• UAX31-R2 Immutable Identifiers: Not complied with for the same reasons as UAX31-R1b is not complied with.

• UAX31-R3 Pattern_White_Space and Pattern_Syntax Characters: Not currently complied with, but might be complied with in the future.

• UAX31-R4 Equivalent Normalized Identifiers: Complied with, using a profile as follows:

  • NFC normalisation for all identifiers.
  • All Hyphen (U+2010) and Hyphen-Minus (U+002D) characters will be treated as equivalent in identifiers.
  • Case detection of the first character shall check for General_Category=Uppercase_Letter to see if a character begins with an uppercase letter. All other characters, including non-cased characters are treated as lowercase for identifier parsing.
  • Case detection of all uppercase identifiers shall exclude all characters with General_Category=Lowercase_Letter and allow all other characters.
  • Note that this case detection is not guaranteed to be stable between Unicode versions, however likely will be for commonly used scripts and characters.

• UAX31-R5 Equivalent Case-Insensitive Identifiers: Not complied with as case insensitive identifiers are not used.

• UAX31-R6 Filtered Normalized Identifiers: Not complied with as no filtering is performed.

• UAX31-R7 Filtered Case-Insensitive Identifiers: Not complied with as no filtering is performed.

• UAX31-R8 Extended Hashtag Identifiers: Not complied with as hashtags are not relevant.

UTS#55, UTS#39 and UTR#36 are not currently complied with.