Skip to main content

ASN.1 parsing, encoding and decoding.

Project description

buildstatus coverage

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)

  • Basic ASN.1 value notation

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

The shell subcommand

Use the command line shell to decode encoded data.

> asn1tools shell

Welcome to the asn1tools shell.

$ help
Commands:
  compile <codec> <specification> [<specification> ...]
  decode <type> <hexstring>
$ compile ber tests/files/foo.asn
$ decode Question 300e0201011609497320312b313d333f
question Question ::= {
    id 1,
    question "Is 1+1=3?"
}
$ exit
>

The decode subcommand

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

> asn1tools decode tests/files/foo.asn Question 300e0201011609497320312b313d333f
question Question ::= {
    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
question Question ::= {
    id 1,
    question "Is 1+1=3?"
}
>

Continuously decode encoded Questions read from standard input. Any line that cannot be decoded is printed as is, in this example the dates.

> cat encoded.txt
2018-02-24 11:22:09
300e0201011609497320312b313d333f
2018-02-24 11:24:15
300e0201021609497320322b323d353f
> cat encoded.txt | asn1tools decode tests/files/foo.asn Question -
2018-02-24 11:22:09
question Question ::= {
    id 1,
    question "Is 1+1=3?"
}
2018-02-24 11:24:15
question Question ::= {
    id 2,
    question "Is 2+2=5?"
}
>

Contributing

  1. Fork the repository.

  2. Install prerequisites.

    pip install -r requirements.txt
  3. Implement the new feature or bug fix.

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

  5. Run the tests.

    make test
  6. Create a pull request.

Specifications

ASN.1 specifications released by ITU.

General

Encodings

Project details


Release history Release notifications | RSS feed

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

asn1tools-0.60.0.tar.gz (581.1 kB view hashes)

Uploaded Source

Built Distribution

asn1tools-0.60.0-py2.py3-none-any.whl (55.9 kB view hashes)

Uploaded Python 2 Python 3

Supported by

AWS AWS Cloud computing and Security Sponsor Datadog Datadog Monitoring Fastly Fastly CDN Google Google Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Sentry Sentry Error logging StatusPage StatusPage Status page