asn1tools 0.20.0

ASN.1 parsing, encoding and decoding.

About

A Python package for ASN.1 parsing, encoding and decoding.

This project is under development and does only support a subset of the ASN.1 specification syntax.

Codecs under development:

• Basic Encoding Rules (BER)

• Distinguished Encoding Rules (DER)

• JSON Encoding Rules (JER)

• Aligned Packed Encoding Rules (PER)

• Unaligned Packed Encoding Rules (UPER)

• XML Encoding Rules (XER)

Planned codecs:

• Octet Encoding Rules (OER)

Project homepage: https://github.com/eerimoq/asn1tools

Documentation: http://asn1tools.readthedocs.org/en/latest

Installation

pip install asn1tools

Example Usage

This is an example ASN.1 specification defining the messages of a fictitious Foo protocol (based on the FooProtocol on Wikipedia).

Foo DEFINITIONS ::= BEGIN

    Question ::= SEQUENCE {
        id        INTEGER,
        question  IA5String
    }

    Answer ::= SEQUENCE {
        id        INTEGER,
        answer    BOOLEAN
    }

END

Scripting

Compile the ASN.1 specification, and encode and decode a question using the default codec (BER).

>>> import asn1tools
>>> foo = asn1tools.compile_files('tests/files/foo.asn')
>>> encoded = foo.encode('Question', {'id': 1, 'question': 'Is 1+1=3?'})
>>> encoded
bytearray(b'0\x0e\x02\x01\x01\x16\x09Is 1+1=3?')
>>> foo.decode('Question', encoded)
{'id': 1, 'question': 'Is 1+1=3?'}

The same ASN.1 specification, but using the PER codec.

>>> import asn1tools
>>> foo = asn1tools.compile_files('tests/files/foo.asn', 'per')
>>> encoded = foo.encode('Question', {'id': 1, 'question': 'Is 1+1=3?'})
>>> encoded
bytearray(b'\x01\x01\tIs 1+1=3?')
>>> foo.decode('Question', encoded)
{'id': 1, 'question': 'Is 1+1=3?'}

See the examples folder for additional examples.

Command line tool

Decode given encoded Question using the default codec (BER).

$ asn1tools decode tests/files/foo.asn Question 300e0201011609497320312b313d333f
id: 1
question: Is 1+1=3?
$

Decode given encoded Question using the UPER codec.

$ asn1tools decode --codec uper tests/files/foo.asn Question 01010993cd03156c5eb37e
id: 1
question: Is 1+1=3?
$

Contributing

1. Fork the repository.

2. Implement the new feature or bug fix.

3. Implement test case(s) to ensure that future changes do not break legacy.

4. Run the tests.

   make test

5. Create a pull request.

Specifications

ASN.1 specifications released by ITU.

General

• X.680: Specification of basic notation

• X.681: Information object specification

• X.682: Constraint specification

• X.683: Parameterization of ASN.1 specifications

Encodings

• X.690: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)

• X.691: Specification of Packed Encoding Rules (PER)

• X.693: XML Encoding Rules (XER)