# asn1crypto A fast, pure Python library for parsing and serializing ASN.1 structures. - [Features](#features) - [Why Another Python ASN.1 Library?](#why-another-python-asn1-library) - [Related Crypto Libraries](#related-crypto-libraries) - [Current Release](#current-release) - [Dependencies](#dependencies) - [Installation](#installation) - [License](#license) - [Documentation](#documentation) - [Continuous Integration](#continuous-integration) - [Testing](#testing) - [Development](#development) [![Travis CI](https://api.travis-ci.org/wbond/asn1crypto.svg?branch=master)](https://travis-ci.org/wbond/asn1crypto) [![AppVeyor](https://ci.appveyor.com/api/projects/status/github/wbond/asn1crypto?branch=master&svg=true)](https://ci.appveyor.com/project/wbond/asn1crypto) [![CircleCI](https://circleci.com/gh/wbond/asn1crypto.svg?style=shield)](https://circleci.com/gh/wbond/asn1crypto) [![Codecov](https://codecov.io/gh/wbond/asn1crypto/branch/master/graph/badge.svg)](https://codecov.io/gh/wbond/asn1crypto) [![PyPI](https://img.shields.io/pypi/v/asn1crypto.svg)](https://pypi.python.org/pypi/asn1crypto) ## Features In addition to an ASN.1 BER/DER decoder and DER serializer, the project includes a bunch of ASN.1 structures for use with various common cryptography standards: | Standard | Module | Source | | ---------------------- | ------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------- | | X.509 | [`asn1crypto.x509`](asn1crypto/x509.py) | [RFC 5280](https://tools.ietf.org/html/rfc5280) | | CRL | [`asn1crypto.crl`](asn1crypto/crl.py) | [RFC 5280](https://tools.ietf.org/html/rfc5280) | | CSR | [`asn1crypto.csr`](asn1crypto/csr.py) | [RFC 2986](https://tools.ietf.org/html/rfc2986), [RFC 2985](https://tools.ietf.org/html/rfc2985) | | OCSP | [`asn1crypto.ocsp`](asn1crypto/ocsp.py) | [RFC 6960](https://tools.ietf.org/html/rfc6960) | | PKCS#12 | [`asn1crypto.pkcs12`](asn1crypto/pkcs12.py) | [RFC 7292](https://tools.ietf.org/html/rfc7292) | | PKCS#8 | [`asn1crypto.keys`](asn1crypto/keys.py) | [RFC 5208](https://tools.ietf.org/html/rfc5208) | | PKCS#1 v2.1 (RSA keys) | [`asn1crypto.keys`](asn1crypto/keys.py) | [RFC 3447](https://tools.ietf.org/html/rfc3447) | | DSA keys | [`asn1crypto.keys`](asn1crypto/keys.py) | [RFC 3279](https://tools.ietf.org/html/rfc3279) | | Elliptic curve keys | [`asn1crypto.keys`](asn1crypto/keys.py) | [SECG SEC1 V2](http://www.secg.org/sec1-v2.pdf) | | PKCS#3 v1.4 | [`asn1crypto.algos`](asn1crypto/algos.py) | [PKCS#3 v1.4](ftp://ftp.rsasecurity.com/pub/pkcs/ascii/pkcs-3.asc) | | PKCS#5 v2.1 | [`asn1crypto.algos`](asn1crypto/algos.py) | [PKCS#5 v2.1](http://www.emc.com/collateral/white-papers/h11302-pkcs5v2-1-password-based-cryptography-standard-wp.pdf) | | CMS (and PKCS#7) | [`asn1crypto.cms`](asn1crypto/cms.py) | [RFC 5652](https://tools.ietf.org/html/rfc5652), [RFC 2315](https://tools.ietf.org/html/rfc2315) | | TSP | [`asn1crypto.tsp`](asn1crypto/tsp.py) | [RFC 3161](https://tools.ietf.org/html/rfc3161) | | PDF signatures | [`asn1crypto.pdf`](asn1crypto/pdf.py) | [PDF 1.7](http://wwwimages.adobe.com/content/dam/Adobe/en/devnet/pdf/pdfs/PDF32000_2008.pdf) | ## Why Another Python ASN.1 Library? Python has long had the [pyasn1](https://pypi.python.org/pypi/pyasn1) and [pyasn1_modules](https://pypi.python.org/pypi/pyasn1-modules) available for parsing and serializing ASN.1 structures. While the project does include a comprehensive set of tools for parsing and serializing, the performance of the library can be very poor, especially when dealing with bit fields and parsing large structures such as CRLs. After spending extensive time using *pyasn1*, the following issues were identified: 1. Poor performance 2. Verbose, non-pythonic API 3. Out-dated and incomplete definitions in *pyasn1-modules* 4. No simple way to map data to native Python data structures 5. No mechanism for overridden universal ASN.1 types The *pyasn1* API is largely method driven, and uses extensive configuration objects and lowerCamelCase names. There were no consistent options for converting types of native Python data structures. Since the project supports out-dated versions of Python, many newer language features are unavailable for use. Time was spent trying to profile issues with the performance, however the architecture made it hard to pin down the primary source of the poor performance. Attempts were made to improve performance by utilizing unreleased patches and delaying parsing using the `Any` type. Even with such changes, the performance was still unacceptably slow. Finally, a number of structures in the cryptographic space use universal data types such as `BitString` and `OctetString`, but interpret the data as other types. For instance, signatures are really byte strings, but are encoded as `BitString`. Elliptic curve keys use both `BitString` and `OctetString` to represent integers. Parsing these structures as the base universal types and then re-interpreting them wastes computation. *asn1crypto* uses the following techniques to improve performance, especially when extracting one or two fields from large, complex structures: - Delayed parsing of byte string values - Persistence of original ASN.1 encoded data until a value is changed - Lazy loading of child fields - Utilization of high-level Python stdlib modules While there is no extensive performance test suite, the `CRLTests.test_parse_crl` test case was used to parse a 21MB CRL file on a late 2013 rMBP. *asn1crypto* parsed the certificate serial numbers in just under 8 seconds. With *pyasn1*, using definitions from *pyasn1-modules*, the same parsing took over 4,100 seconds. For smaller structures the performance difference can range from a few times faster to an order of magnitude of more. ## Related Crypto Libraries *asn1crypto* is part of the modularcrypto family of Python packages: - [asn1crypto](https://github.com/wbond/asn1crypto) - [oscrypto](https://github.com/wbond/oscrypto) - [csrbuilder](https://github.com/wbond/csrbuilder) - [certbuilder](https://github.com/wbond/certbuilder) - [crlbuilder](https://github.com/wbond/crlbuilder) - [ocspbuilder](https://github.com/wbond/ocspbuilder) - [certvalidator](https://github.com/wbond/certvalidator) ## Current Release 0.24.0 - [changelog](changelog.md) ## Dependencies Python 2.6, 2.7, 3.2, 3.3, 3.4, 3.5, 3.6 or pypy. *No third-party packages required.* ## Installation ```bash pip install asn1crypto ``` ## License *asn1crypto* is licensed under the terms of the MIT license. See the [LICENSE](LICENSE) file for the exact license text. ## Documentation The documentation for *asn1crypto* is composed of tutorials on basic usage and links to the source for the various pre-defined type classes. ### Tutorials - [Universal Types with BER/DER Decoder and DER Encoder](docs/universal_types.md) - [PEM Encoder and Decoder](docs/pem.md) ### Reference - [Universal types](asn1crypto/core.py), `asn1crypto.core` - [Digest, HMAC, signed digest and encryption algorithms](asn1crypto/algos.py), `asn1crypto.algos` - [Private and public keys](asn1crypto/keys.py), `asn1crypto.keys` - [X509 certificates](asn1crypto/x509.py), `asn1crypto.x509` - [Certificate revocation lists (CRLs)](asn1crypto/crl.py), `asn1crypto.crl` - [Online certificate status protocol (OCSP)](asn1crypto/ocsp.py), `asn1crypto.ocsp` - [Certificate signing requests (CSRs)](asn1crypto/csr.py), `asn1crypto.csr` - [Private key/certificate containers (PKCS#12)](asn1crypto/pkcs12.py), `asn1crypto.pkcs12` - [Cryptographic message syntax (CMS, PKCS#7)](asn1crypto/cms.py), `asn1crypto.cms` - [Time stamp protocol (TSP)](asn1crypto/tsp.py), `asn1crypto.tsp` - [PDF signatures](asn1crypto/pdf.py), `asn1crypto.pdf` ## Continuous Integration - [Windows](https://ci.appveyor.com/project/wbond/asn1crypto/history) via AppVeyor - [OS X](https://circleci.com/gh/wbond/asn1crypto) via CircleCI - [Linux](https://travis-ci.org/wbond/asn1crypto/builds) via Travis CI - [Test Coverage](https://codecov.io/gh/wbond/asn1crypto/commits) via Codecov ## Testing Tests are written using `unittest` and require no third-party packages: ```bash python run.py tests ``` To run only some tests, pass a regular expression as a parameter to `tests`. ```bash python run.py tests ocsp ``` ## Development To install the package used for linting, execute: ```bash pip install --user -r requires/lint ``` The following command will run the linter: ```bash python run.py lint ``` Support for code coverage can be installed via: ```bash pip install --user -r requires/coverage ``` Coverage is measured by running: ```bash python run.py coverage ``` To install the necessary packages for releasing a new version on PyPI, run: ```bash pip install --user -r requires/release ``` Releases are created by: - Making a git tag in [semver](http://semver.org/) format - Running the command: ```bash python run.py release ``` Existing releases can be found at https://pypi.python.org/pypi/asn1crypto. ## CI Tasks A task named `deps` exists to ensure a modern version of `pip` is installed, along with all necessary testing dependencies. The `ci` task runs `lint` (if flake8 is available for the version of Python) and `coverage` (or `tests` if coverage is not available for the version of Python). If the current directory is a clean git working copy, the coverage data is submitted to codecov.io. ```bash python run.py deps python run.py ci ```