Contributing to VulnerableCode

Thank you so much for being so interested in contributing to VulnerableCode. We are always on the lookout for enthusiastic contributors like you who can make our project better, and we are willing to lend a helping hand if you have any questions or need guidance along the way. That being said, here are a few resources to help you get started.

Note

By contributing to the VulnerableCode project, you agree to the Developer Certificate of Origin.

Do Your Homework

Before adding a contribution or create a new issue, take a look at the project’s README, read through our documentation, and browse existing issues, to develop some understanding of the project and confirm whether a given issue/feature has previously been discussed.

Ways to Contribute

Contributing to the codebase is not the only way to add value to VulnerableCode or join our community. Below are some examples to get involved:

First Timers

You are here to help, but you are a new contributor! No worries, we always welcome newcomer contributors. We maintain some good first issues and encourage new contributors to work on those issues for a smooth start.

Tip

If you are an open-source newbie, make sure to check the extra resources at the bottom of this page to get the hang of the contribution process!

Code Contributions

For more established contributors, you can contribute to the codebase in several ways:

Report a bug; just remember to be as specific as possible.
Submit a bug fix for any existing issue.
Create a new issue to request a feature, submit a feedback, or ask a question.

Note

Make sure to check existing issues, to confirm whether a given issue or a question has previously been discussed.

Documentation Improvements

Documentation is a critical aspect of any project that is usually neglected or overlooked. We value any suggestions to improve vulnerablecode documentation.

Tip

Our documentation is treated like code. Make sure to check our writing guidelines to help guide new users.

Other Ways

You want to contribute to other aspects of the VulnerableCode project, and you cannot find what you are looking for! You can always discuss new topics, ask questions, and interact with us and other community members on AboutCode Gitter and VulnerableCode Gitter

Helpful Resources

Review our comprehensive guide for more details on how to add quality contributions to our codebase and documentation
Check this free resource on how to contribute to an open source project on github
Follow this wiki page on how to write good commit messages
Pro Git book
How to write a good bug report

Add a new importer

This tutorial contains all the things one should know to quickly implement an importer. Many internal details about importers can be found inside the :file:`vulnerabilites/importer.py` file. Make sure to go through :ref:`importer-overview` before you begin writing one.

TL;DR

Create a new :file:`vulnerabilities/importers/{importer_name.py}` file.
Create a new importer subclass inheriting from the Importer superclass defined in vulnerabilites.importer. It is conventional to end an importer name with Importer.
Specify the importer license.
Implement the advisory_data method to process the data source you are writing an importer for.
Add the newly created importer to the importers registry at vulnerabilites/importers/__init__.py

Prerequisites

Before writing an importer, it is important to familiarize yourself with the following concepts.

PackageURL

VulnerableCode extensively uses Package URLs to identify a package. See the PackageURL specification and its Python implementation for more details.

Example usage:

from packageurl import PackageURL
purl = PackageURL(name="ffmpeg", type="deb", version="1.2.3")

AdvisoryData

AdvisoryData is an intermediate data format: it is expected that your importer will convert the raw scraped data into AdvisoryData objects. All the fields in AdvisoryData dataclass are optional; it is the importer's resposibility to ensure that it contains meaningful information about a vulnerability.

AffectedPackage

AffectedPackage data type is used to store a range of affected versions and a fixed version of a given package. For all version-related data, univers library is used.

Univers

univers is a Python implementation of the vers specification. It can parse and compare all the package versions and all the ranges, from debian, npm, pypi, ruby and more. It processes all the version range specs and expressions.

Importer

All the generic importers need to implement the Importer class. For Git or Oval data source, GitImporter or OvalImporter could be implemented.

Note

GitImporter and OvalImporter need a complete rewrite. Interested in :ref:`contributing` ?

Writing an importer

Create Importer Source File

All importers are located in the :file:`vulnerabilites/importers` directory. Create a new file to put your importer code in. Generic importers are implemented by writing a subclass for the Importer superclass and implementing the unimplemented methods.

Specify the Importer License

Importers scrape data off the internet. In order to make sure the data is useable, a license must be provided. Populate the spdx_license_expression with the appropriate value. The SPDX license identifiers can be found at https://spdx.org/licenses/.

Note

An SPDX license identifier by itself is a valid licence expression. In case you need more complex expressions, see https://spdx.github.io/spdx-spec/v2.3/SPDX-license-expressions/

Implement the `advisory_data` Method

The advisory_data method scrapes the advisories from the data source this importer is targeted at. It is required to return an Iterable of AdvisoryData objects, and thus it is a good idea to yield from this method after creating each AdvisoryData object.

At this point, an example importer will look like this:

:file:`vulnerabilites/importers/example.py`

from typing import Iterable

from packageurl import PackageURL

from vulnerabilities.importer import AdvisoryData
from vulnerabilities.importer import Importer


class ExampleImporter(Importer):

    spdx_license_expression = "BSD-2-Clause"

    def advisory_data(self) -> Iterable[AdvisoryData]:
        return []

This importer is only a valid skeleton and does not import anything at all.

Let us implement another dummy importer that actually imports some data.

Here we have a dummy_package which follows NginxVersionRange and SemverVersion for version management from univers.

Note

It is possible that the versioning scheme you are targeting has not yet been implemented in the univers library. If this is the case, you will need to head over there and implement one.

from datetime import datetime
from datetime import timezone
from typing import Iterable

import requests
from packageurl import PackageURL
from univers.version_range import NginxVersionRange
from univers.versions import SemverVersion

from vulnerabilities.importer import AdvisoryData
from vulnerabilities.importer import AffectedPackage
from vulnerabilities.importer import Importer
from vulnerabilities.importer import Reference
from vulnerabilities.importer import VulnerabilitySeverity
from vulnerabilities.severity_systems import SCORING_SYSTEMS


class ExampleImporter(Importer):

    spdx_license_expression = "BSD-2-Clause"

    def advisory_data(self) -> Iterable[AdvisoryData]:
        raw_data = fetch_advisory_data()
        for data in raw_data:
            yield parse_advisory_data(data)


def fetch_advisory_data():
    return [
        {
            "id": "CVE-2021-23017",
            "summary": "1-byte memory overwrite in resolver",
            "advisory_severity": "medium",
            "vulnerable": "0.6.18-1.20.0",
            "fixed": "1.20.1",
            "reference": "http://mailman.nginx.org/pipermail/nginx-announce/2021/000300.html",
            "published_on": "14-02-2021 UTC",
        },
        {
            "id": "CVE-2021-1234",
            "summary": "Dummy advisory",
            "advisory_severity": "high",
            "vulnerable": "0.6.18-1.20.0",
            "fixed": "1.20.1",
            "reference": "http://example.com/cve-2021-1234",
            "published_on": "06-10-2021 UTC",
        },
    ]


def parse_advisory_data(raw_data) -> AdvisoryData:
    purl = PackageURL(type="example", name="dummy_package")
    affected_version_range = NginxVersionRange.from_native(raw_data["vulnerable"])
    fixed_version = SemverVersion(raw_data["fixed"])
    affected_package = AffectedPackage(
        package=purl, affected_version_range=affected_version_range, fixed_version=fixed_version
    )
    severity = VulnerabilitySeverity(
        system=SCORING_SYSTEMS["generic_textual"], value=raw_data["advisory_severity"]
    )
    references = [Reference(url=raw_data["reference"], severities=[severity])]
    date_published = datetime.strptime(raw_data["published_on"], "%d-%m-%Y %Z").replace(
        tzinfo=timezone.utc
    )

    return AdvisoryData(
        aliases=[raw_data["id"]],
        summary=raw_data["summary"],
        affected_packages=[affected_package],
        references=references,
        date_published=date_published,
    )

Note

Use make valid to format your new code using black and isort automatically.

Use make check to check for formatting errors.

Register the Importer

Finally, register your importer in the importer registry at :file:`vulnerabilites/importers/__init__.py`

 from vulnerabilities.importers import example
 from vulnerabilities.importers import nginx

 IMPORTERS_REGISTRY = [nginx.NginxImporter, example.ExampleImporter]

 IMPORTERS_REGISTRY = {x.qualified_name: x for x in IMPORTERS_REGISTRY}

Congratulations! You have written your first importer.

Run Your First Importer

If everything went well, you will see your importer in the list of available importers.

 $ ./manage.py import --list

 Vulnerability data can be imported from the following importers:
 vulnerabilities.importers.nginx.NginxImporter
 vulnerabilities.importers.example.ExampleImporter

Now, run the importer.

$ ./manage.py import vulnerabilities.importers.example.ExampleImporter

Importing data using vulnerabilities.importers.example.ExampleImporter
Successfully imported data using vulnerabilities.importers.example.ExampleImporter

See :ref:`command_line_interface` for command line usage instructions.

Enable Debug Logging (Optional)

For more visibility, turn on debug logs in :file:`vulnerablecode/settings.py`.

DEBUG = True
LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'handlers': {
        'console': {
            'class': 'logging.StreamHandler',
        },
    },
    'root': {
        'handlers': ['console'],
        'level': 'DEBUG',
    },
}

Invoke the import command now and you will see (in a fresh database):

$ ./manage.py import vulnerabilities.importers.example.ExampleImporter

Importing data using vulnerabilities.importers.example.ExampleImporter
Starting import for vulnerabilities.importers.example.ExampleImporter
[*] New Advisory with aliases: ['CVE-2021-23017'], created_by: vulnerabilities.importers.example.ExampleImporter
[*] New Advisory with aliases: ['CVE-2021-1234'], created_by: vulnerabilities.importers.example.ExampleImporter
Finished import for vulnerabilities.importers.example.ExampleImporter. Imported 2 advisories.
Successfully imported data using vulnerabilities.importers.example.ExampleImporter

Add a new improver

This tutorial contains all the things one should know to quickly implement an improver. Many internal details about improvers can be found inside the :file:`vulnerabilites/improver.py` file. Make sure to go through :ref:`improver-overview` before you begin writing one.

TL;DR

Locate the importer that this improver will be improving data of at :file:`vulnerabilities/importers/{importer_name.py}` file.
Create a new improver subclass inheriting from the Improver superclass defined in vulnerabilites.improver. It is conventional to end an improver name with Improver.
Implement the interesting_advisories property to return a QuerySet of imported data (Advisory) you are interested in.
Implement the get_inferences method to return an iterable of Inference objects for the given AdvisoryData.
Add the newly created improver to the improvers registry at vulnerabilites/improvers/__init__.py.

Prerequisites

Before writing an improver, it is important to familiarize yourself with the following concepts.

Importer

Importers are responsible for scraping vulnerability data from various data sources without creating a complete relational model between vulnerabilites and their fixes and storing them in a structured fashion. These data are stored in the Advisory model and can be converted to an equivalent AdvisoryData for various use cases. See :ref:`importer-overview` for a brief overview on importers.

Importer Prerequisites

Improvers consume data produced by importers, and thus it is important to familiarize yourself with :ref:`Importer Prerequisites <tutorial_add_a_new_importer_prerequisites>`.

Inference

Inferences express the contract between the improvers and the improve runner framework. An inference is intended to contain data points about a vulnerability without any uncertainties, which means that one inference will target one vulnerability with the specific relevant affected and fixed packages (in the form of PackageURLs). There is no notion of version ranges here: all package versions must be explicitly specified.

Because this concrete relationship is rarely available anywhere upstream, we have to infer these values, thus the name. As inferring something is not always perfect, an Inference also comes with a confidence score.

Improver

All the Improvers must inherit from Improver superclass and implement the interesting_advisories property and the get_inferences method.

Writing an improver

Locate the Source File

If the improver will be working on data imported by a specific importer, it will be located in the same file at :file:`vulnerabilites/importers/{importer-name.py}`. Otherwise, if it is a generic improver, create a new file :file:`vulnerabilites/improvers/{improver-name.py}`.

Explore Package Managers (Optional)

If your Improver depends on the discrete versions of a package, the package managers' VersionAPI located at :file:`vulnerabilites/package_managers.py` could come in handy. You will need to instantiate the relevant VersionAPI in the improver's constructor and use it later in the implemented methods. See an already implemented improver (NginxBasicImprover) for an example usage.

Implement the `interesting_advisories` Property

This property is intended to return a QuerySet of Advisory on which the Improver is designed to work.

For example, if the improver is designed to work on Advisories imported by ExampleImporter, the property can be implemented as

class ExampleBasicImprover(Improver):

    @property
    def interesting_advisories(self) -> QuerySet:
        return Advisory.objects.filter(created_by=ExampleImporter.qualified_name)

Implement the `get_inferences` Method

The framework calls get_inferences method for every AdvisoryData that is obtained from the Advisory QuerySet returned by the interesting_advisories property.

It is expected to return an iterable of Inference objects for the given AdvisoryData. To avoid storing a lot of Inferences in memory, it is preferable to yield from this method.

A very simple Improver that processes all Advisories to create the minimal relationships that can be obtained by existing data can be found at :file:`vulnerabilites/improvers/default.py`, which is an example of a generic improver. For a more sophisticated and targeted example, you can look at an already implemented improver (e.g., :file:`vulnerabilites/importers/nginx.py`).

Improvers are not limited to improving discrete versions and may also improve aliases. One such example, improving the importer written in the :ref:`importer tutorial <tutorial_add_a_new_importer>`, is shown below.

from datetime import datetime
from datetime import timezone
from typing import Iterable

import requests
from django.db.models.query import QuerySet
from packageurl import PackageURL
from univers.version_range import NginxVersionRange
from univers.versions import SemverVersion

from vulnerabilities.importer import AdvisoryData
from vulnerabilities.improver import MAX_CONFIDENCE
from vulnerabilities.improver import Improver
from vulnerabilities.improver import Inference
from vulnerabilities.models import Advisory
from vulnerabilities.severity_systems import SCORING_SYSTEMS


class ExampleImporter(Importer):
    ...


class ExampleAliasImprover(Improver):
    @property
    def interesting_advisories(self) -> QuerySet:
        return Advisory.objects.filter(created_by=ExampleImporter.qualified_name)

    def get_inferences(self, advisory_data) -> Iterable[Inference]:
        for alias in advisory_data.aliases:
            new_aliases = fetch_additional_aliases(alias)
            aliases = new_aliases + [alias]
            yield Inference(aliases=aliases, confidence=MAX_CONFIDENCE)


def fetch_additional_aliases(alias):
    alias_map = {
        "CVE-2021-23017": ["PYSEC-1337", "CERTIN-1337"],
        "CVE-2021-1234": ["ANONSEC-1337", "CERTDES-1337"],
    }
    return alias_map.get(alias)

Note

Use make valid to format your new code using black and isort automatically.

Use make check to check for formatting errrors.

Register the Improver

Finally, register your improver in the improver registry at :file:`vulnerabilites/improvers/__init__.py`.

 from vulnerabilities import importers
 from vulnerabilities.improvers import default

 IMPROVERS_REGISTRY = [
     default.DefaultImprover,
     importers.nginx.NginxBasicImprover,
     importers.example.ExampleAliasImprover,
 ]

 IMPROVERS_REGISTRY = {x.qualified_name: x for x in IMPROVERS_REGISTRY}

Congratulations! You have written your first improver.

Run Your First Improver

If everything went well, you will see your improver in the list of available improvers.

 $ ./manage.py improve --list

 Vulnerability data can be processed by these available improvers:
 vulnerabilities.improvers.default.DefaultImprover
 vulnerabilities.importers.nginx.NginxBasicImprover
 vulnerabilities.importers.example.ExampleAliasImprover

Before running the improver, make sure you have imported the data. An improver cannot improve if there is nothing imported.

$ ./manage.py import vulnerabilities.importers.example.ExampleImporter

Importing data using vulnerabilities.importers.example.ExampleImporter
Successfully imported data using vulnerabilities.importers.example.ExampleImporter

Now, run the improver.

$ ./manage.py improve vulnerabilities.importers.example.ExampleAliasImprover

 Improving data using vulnerabilities.importers.example.ExampleAliasImprover
 Successfully improved data using vulnerabilities.importers.example.ExampleAliasImprover

See :ref:`command_line_interface` for command line usage instructions.

Enable Debug Logging (Optional)

For more visibility, turn on debug logs in :file:`vulnerablecode/settings.py`.

DEBUG = True
LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'handlers': {
        'console': {
            'class': 'logging.StreamHandler',
        },
    },
    'root': {
        'handlers': ['console'],
        'level': 'DEBUG',
    },
}

Invoke the improve command now and you will see (in a fresh database, after importing):

$ ./manage.py improve vulnerabilities.importers.example.ExampleAliasImprover

Improving data using vulnerabilities.importers.example.ExampleAliasImprover
Running improver: vulnerabilities.importers.example.ExampleAliasImprover
Improving advisory id: 1
New alias for <Vulnerability: VULCOID-23dd9060-3bc0-4454-bfbd-d16c08a966a6>: PYSEC-1337
New alias for <Vulnerability: VULCOID-23dd9060-3bc0-4454-bfbd-d16c08a966a6>: CVE-2021-23017
New alias for <Vulnerability: VULCOID-23dd9060-3bc0-4454-bfbd-d16c08a966a6>: CERTIN-1337
Improving advisory id: 2
New alias for <Vulnerability: VULCOID-fae4e06e-4815-45fe-ae95-8d2356ffb5b9>: CERTDES-1337
New alias for <Vulnerability: VULCOID-fae4e06e-4815-45fe-ae95-8d2356ffb5b9>: ANONSEC-1337
New alias for <Vulnerability: VULCOID-fae4e06e-4815-45fe-ae95-8d2356ffb5b9>: CVE-2021-1234
Finished improving using vulnerabilities.importers.example.ExampleAliasImprover.
Successfully improved data using vulnerabilities.importers.example.ExampleAliasImprover

Note

Even though CVE-2021-23017 and CVE-2021-1234 are not supplied by this improver, the output above shows them because we left out running the DefaultImprover in the example. The DefaultImprover inserts minimal data found via the importers in the database (here, the above two CVEs). Run importer, DefaultImprover and then your improver in this sequence to avoid this anomaly.

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Contributing to VulnerableCode

Do Your Homework

Ways to Contribute

First Timers

Code Contributions

Documentation Improvements

Other Ways

Helpful Resources

Add a new importer

TL;DR

Prerequisites

PackageURL

AdvisoryData

AffectedPackage

Univers

Importer

Writing an importer

Create Importer Source File

Specify the Importer License

Implement the advisory_data Method

Register the Importer

Run Your First Importer

Enable Debug Logging (Optional)

Add a new improver

TL;DR

Prerequisites

Importer

Importer Prerequisites

Inference

Improver

Writing an improver

Locate the Source File

Explore Package Managers (Optional)

Implement the interesting_advisories Property

Implement the get_inferences Method

Register the Improver

Run Your First Improver

Enable Debug Logging (Optional)

Implement the `advisory_data` Method

Implement the `interesting_advisories` Property

Implement the `get_inferences` Method