Parsers

Pre-requisites

• You have forked https://github.com/DefectDojo/django-DefectDojo and cloned locally.
• Checkout dev and make sure you’re up to date with the latest changes.
• It’s advised that you create a dedicated branch for your development, such as git checkout -b parser-name.

It is easiest to use the docker compose deployment as it has hot-reload capbility for uWSGI. Set up your environment to use the dev environment:

$ docker/setEnv.sh dev

Please have a look at DOCKER.md for more details.

Docker images

You will want to build your docker images locally, and eventually pass in your local user’s uid to be able to write to the image (handy for database migration files). Assuming your user’s uid is 1000, then:

$ docker compose build --build-arg uid=1000

Which files do you need to modify?

Factory contract

Parsers are loaded dynamicaly with a factory pattern. To have your parser loaded and works correctly, you need to implement the contract.

1. your parser MUST be in a sub-module of module dojo.tools
   • ex: dojo.tools.my_tool.parser module
2. your parser MUST be a class in this sub-module.
   • ex: dojo.tools.my_tool.parser.MyToolParser
3. The name of this class MUST be the Python module name without underscores and with Parser suffix.
   • ex: dojo.tools.my_tool.parser.MyToolParser
4. This class MUST have an empty constructor or no constructor
5. This class MUST implement 3 methods:
   1. def get_scan_types(self) This function return a list of all the scan_type supported by your parser. This identifiers are used internally. Your parser can support more than one scan_type. For example some parsers use different identifier to modify the behavior of the parser (aggregate, filter, etc…)
   2. def get_label_for_scan_types(self, scan_type): This function return a string used to provide some text in the UI (short label)
   3. def get_description_for_scan_types(self, scan_type): This function return a string used to provide some text in the UI (long description)
   4. def get_findings(self, file, test) This function return a list of findings
6. If your parser have more than 1 scan_type (for detailled mode) you MUST implement def set_mode(self, mode) method

Example:

class MyToolParser(object):
    def get_scan_types(self):
        return ["My Tool Scan", "My Tool Scan detailed"]

    def get_label_for_scan_types(self, scan_type):
        if scan_type == "My Tool Scan":
            return "My Tool XML Scan aggregated by ..."
        else:
            return "My Tool XML Scan"

    def get_description_for_scan_types(self, scan_type):
        return "Aggregates findings per cwe, title, description, file_path. SonarQube output file can be imported in HTML format. Generate with https://github.com/soprasteria/sonar-report version >= 1.1.0"

    def requires_file(self, scan_type):
        return False

    # mode:
    # None (default): aggregates vulnerabilites per sink filename (legacy behavior)
    # 'detailed' : No aggregation
    mode = None

    def set_mode(self, mode):
        self.mode = mode

    def get_findings(self, file, test):
        <...>

API Parsers

DefectDojo has a limited number of API parsers. While we won’t remove these connectors, adding API connectors has been problematic and thus we cannot accept new API parsers / connectors from the community at this time for supportability reasonsing. To maintain a high quality API connector, it is necessary to have a license to the tool. To get that license requires partnership with the author or vendor. We’re close to announcing a new program to help address this and bring API connectors to DefectDojo.

Template Generator

Use the template parser to quickly generate the files required. To get started you will need to install cookiecutter.

$ pip install cookiecutter

Then generate your scanner parser from the root of django-DefectDojo:

$ cookiecutter https://github.com/DefectDojo/cookiecutter-scanner-parser

Read more on the template configuration variables.

Things to pay attention to

Here is a list of considerations that will make the parser robust for both common cases and edge cases.

Do not parse URLs by hand

We use 2 modules to handle endpoints:

• hyperlink
• dojo.models with a specific class to handle processing around URLs to create endpoints Endpoint.

All the existing parser use the same code to parse URL and create endpoints. Using Endpoint.from_uri() is the best way to create endpoints. If you really need to parse an URL, use hyperlink module.

Good example:

    if "url" in item:
        endpoint = Endpoint.from_uri(item["url"])
        finding.unsaved_endpoints = [endpoint]

Very bad example:

    u = urlparse(item["url"])
    endpoint = Endpoint(host=u.host)
    finding.unsaved_endpoints = [endpoint]

Use the right libraries to parse information

Various file formats are handled through libraries. In order to keep DefectDojo slim and also don’t extend the attack surface, keep the number of libraries used minimal and take other parsers as an example.

defusedXML in favour of lxml

As xml is by default an unsecure format, the information parsed from various xml output has to be parsed in a secure way. Within an evaluation, we determined that defusedXML is the library which we will use in the future to parse xml files in parsers as this library is rated more secure. Thus, we will only accept PRs with the defusedxml library.

Not all attributes are mandatory

Parsers may have many fields, out of which many of them may be optional. It better to not set attribute if you don’t have data instead of filling with values like NA, No data etc…

Check class dojo.models.Finding

Data could be missing in the source report

Always make sure you include checks to avoid potential KeyError errors (e.g. field does not exist), for those fields you are not absolutely certain will always be in file that will get uploaded. These translate to 500 error, and do not look good.

Good example:

   if "mykey" in data:
       finding.cwe = data["mykey"]

Do not parse CVSS by hand (vector, score or severity)

Data can have CVSS vectors or scores. Don’t write your own CVSS score algorithm. For parser, we rely on module cvss.

It’s easy to use and will make the parser aligned with the rest of the code.

Example of use:

from cvss.cvss3 import CVSS3
import cvss.parser
vectors = cvss.parser.parse_cvss_from_text("CVSS:3.0/S:C/C:H/I:H/A:N/AV:P/AC:H/PR:H/UI:R/E:H/RL:O/RC:R/CR:H/IR:X/AR:X/MAC:H/MPR:X/MUI:X/MC:L/MA:X")
if len(vectors) > 0 and type(vectors[0]) == CVSS3:
    print(vectors[0].severities())  # this is the 3 severities

    cvssv3 = vectors[0].clean_vector()
    severity = vectors[0].severities()[0]
    vectors[0].compute_base_score()
    cvssv3_score = vectors[0].scores()[0]
    print(severity)
    print(cvssv3_score)

Good example:

vectors = cvss.parser.parse_cvss_from_text(item['cvss_vect'])
if len(vectors) > 0 and type(vectors[0]) == CVSS3:
    finding.cvss = vectors[0].clean_vector()
    finding.severity = vectors[0].severities()[0]  # if your tool does generate severity

Bad example (DIY):

    def get_severity(self, cvss, cvss_version="2.0"):
        cvss = float(cvss)
        cvss_version = float(cvss_version[:1])
        # If CVSS Version 3 and above
        if cvss_version >= 3:
            if cvss > 0 and cvss < 4:
                return "Low"
            elif cvss >= 4 and cvss < 7:
                return "Medium"
            elif cvss >= 7 and cvss < 9:
                return "High"
            elif cvss >= 9:
                return "Critical"
            else:
                return "Informational"
        # If CVSS Version prior to 3
        else:
            if cvss > 0 and cvss < 4:
                return "Low"
            elif cvss >= 4 and cvss < 7:
                return "Medium"
            elif cvss >= 7 and cvss <= 10:
                return "High"
            else:
                return "Informational"

Deduplication algorithm

By default a new parser uses the ‘legacy’ deduplication algorithm documented at https://documentation.defectdojo.com/usage/features/#deduplication-algorithms

Please use a pre-defined deduplication algorithm where applicable.

Unit tests

Each parser must have unit tests, at least to test for 0 vuln, 1 vuln and many vulns. You can take a look at how other parsers have them for starters. The more quality tests, the better.

It’s important to add checks on attributes of findings. For ex:

        with self.subTest(i=0):
            finding = findings[0]
            self.assertEqual("test title", finding.title)
            self.assertEqual(True, finding.active)
            self.assertEqual(True, finding.verified)
            self.assertEqual(False, finding.duplicate)
            self.assertIn(finding.severity, Finding.SEVERITIES)
            self.assertEqual("CVE-2020-36234", finding.vulnerability_ids[0])
            self.assertEqual(261, finding.cwe)
            self.assertEqual("CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N", finding.cvssv3)
            self.assertIn("security", finding.tags)
            self.assertIn("network", finding.tags)
            self.assertEqual("3287f2d0-554f-491b-8516-3c349ead8ee5", finding.unique_id_from_tool)
            self.assertEqual("TEST1", finding.vuln_id_from_tool)

Use with to open example files

In order to make certain that file handles are closed properly, please use the with pattern to open files. Instead of:

    testfile = open("path_to_file.json")
    ...
    testfile.close()

use:

    with open("path_to_file.json") as testfile:
        ...

This ensures the file is closed at the end of the with statement, even if an exception occurs somewhere in the block.

Test database

To test your unit tests locally, you first need to grant some rights. Get your MySQL root password from the docker compose logs, login as root and issue the following commands:

MYSQL> grant all privileges on test_defectdojo.* to defectdojo@'%';
MYSQL> flush privileges;

Run your tests

This local command will launch the unit test for your new parser

$ docker compose exec uwsgi bash -c 'python manage.py test unittests.tools.<your_unittest_py_file>.<main_class_name> -v2'

or like this:

$ ./dc-unittest.sh --test-case unittests.tools.<your_unittest_py_file>.<main_class_name>

Example for the blackduck hub parser:

$ docker compose exec uwsgi bash -c 'python manage.py test unittests.tools.test_blackduck_csv_parser.TestBlackduckHubParser -v2'

or like this:

$ ./dc-unittest.sh --test-case unittests.tools.test_blackduck_csv_parser.TestBlackduckHubParser

Endpoint validation

Some types of parsers create a list of endpoints that are vulnerable (they are stored in finding.unsaved_endpoints). DefectDojo requires storing endpoints in a specific format (which follow RFCs). Endpoints that do not follow this format can be stored but they will be marked as broken (red flag 🚩in UI). To be sure your parse store endpoints in the correct format run the .clean() function for all endpoints in unit tests

findings = parser.get_findings(testfile, Test())
for finding in findings:
    for endpoint in finding.unsaved_endpoints:
        endpoint.clean()

Tests API Parsers

Not only parser but also importer should be tested. patch method from unittest.mock is usualy usefull for simulating API responses. It is highly recommeded to use it.

Other files that could be involved

Change to the model

In the event where you’d have to change the model, e.g. to increase a database column size to accomodate a longer string of data to be saved

• Change what you need in dojo/models.py

• Create a new migration file in dojo/db_migrations by running and including as part of your PR

      $ docker compose exec uwsgi bash -c 'python manage.py makemigrations -v2'
      

Accept a different type of file to upload

If you want to be able to accept a new type of file for your parser, take a look at dojo/forms.py around line 436 (at the time of this writing) or locate the 2 places (for import and re-import) where you find the string attrs={"accept":.

Formats currently accepted: .xml, .csv, .nessus, .json, .html, .js, .zip.

A need for more than just the parser.py

Of course, nothing prevents you from having more files than the parser.py file. It’s python :-)

Pull request examples

If you want to take a look at previous parsers that are now part of DefectDojo, take a look at https://github.com/DefectDojo/django-DefectDojo/pulls?q=is%3Apr+sort%3Aupdated-desc+label%3A%22Import+Scans%22+is%3Aclosed

Update the import page documentation

Please add a new .md file in [docs/content/en/integrations/parsers] with the details of your new parser. Include the following content headings:

• Acceptable File Type(s) - please include how to generate this type of file from the related tool, as some tools have multiple methods or require specific commands.
• An example unit test block, if applicable.
• A link to the relevant unit tests folder so that users can quickly navigate there from Documentation.
• A link to the scanner itself - (e.g. GitHub or vendor link)

Here is an example of a completed Parser documentation page: https://defectdojo.github.io/django-DefectDojo/integrations/parsers/file/awssecurityhub/