NOTE! This code has been upgraded and the current release no longer supports installation in AWS

If you wish to deploy in AWS, use this previous release.

Farsight DNSDB Relay (Cisco Hosted)

Concrete Relay implementation using Farsight DNSDB as a third-party Cyber Threat Intelligence service provider.

The Relay itself is just a simple application written in Python that can be easily packaged and deployed. This relay is now Cisco Hosted and no longer requires AWS Lambda.

Rationale

• We need an application that will translate API requests from SecureX Threat Response to the third-party integration, and vice versa.
• We need an application that can be completely self contained within a virtualized container using Docker.

Testing (Optional)

Open the code folder in your terminal.

cd code

If you want to test the application you have to install a couple of extra dependencies from the Pipfile file:

pip install --no-cache-dir --upgrade pipenv && pipenv install --dev

You can perform two kinds of testing:

• Run static code analysis checking for any semantic discrepancies and PEP 8 compliance:

  flake8 .

• Run the suite of unit tests and measure the code coverage:

  coverage run --source api/ -m pytest --verbose tests/unit/ && coverage report

If you want to test the live Lambda you may use any HTTP client (e.g. Postman), just make sure to send requests to your Lambda's URL with the Authorization header set to Bearer <JWT>.

NOTE. If you need input data for testing purposes you can use data from the observables.json file.

Building the Docker Container

In order to build the application, we need to use a Dockerfile.

1. Open a terminal. Build the container image using the docker build command.

docker build -t tr-05-farsight-dnsdb .

2. Once the container is built, and an image is successfully created, start your container using the docker run command and specify the name of the image we have just created. By default, the container will listen for HTTP requests using port 9090.

docker run -dp 9090:9090 --name tr-05-farsight-dnsdb tr-05-farsight-dnsdb

3. Watch the container logs to ensure it starts correctly.

docker logs tr-05-farsight-dnsdb

4. Once the container has started correctly, open your web browser to http://localhost:9090. You should see a response from the container.

curl http://localhost:9090

Implementation Details

This application was developed and tested under Python 3.9.

Implemented Relay Endpoints

• POST /health

  • Verifies the Authorization Bearer JWT and decodes it to restore the original credentials.
  • Authenticates to the underlying external service to check that the provided credentials are valid and the service is available at the moment.

• POST /observe/observables

  • Accepts a list of observables and filters out unsupported ones.
  • Verifies the Authorization Bearer JWT and decodes it to restore the original credentials.
  • Makes a series of requests to the underlying external service to query for some cyber threat intelligence data on each supported observable.
  • Maps the fetched data into appropriate CTIM entities.
  • Returns a list per each of the following CTIM entities (if any extracted):
    • Sighting.

• POST /refer/observables

  • Accepts a list of observables and filters out unsupported ones.
  • Builds a search link per each supported observable to pivot back to the underlying external service and look up the observable there.
  • Builds a browse link per each supported observable to pivot back directly to the observable page if there is one.
  • Returns a list of those links.

• POST /version

  • Returns the current version of the application.

Supported Types of Observables

• ip
• ipv6
• domain

CTIM Mapping Specifics

There are two possible mappings of Farsight historical Domain->IP resolution to CTIM Sighting which can be switched between with an environment variable AGGREGATE.

• If Aggregated Mode is off, each resolution generates a CTIM Sighting.

  • If an investigated observable is a domain, it is linked to each IP item from the resolution.rdata field with an observed relation domain->'Resolved_To'->IP.
  • If an investigated observable is an IP, it is linked to a domain from the resolution.rrname field with an observed relation domain->'Resolved_To'->IP.
  • The resolution count field is used as a Sighting.count.
  • Each Farsight resolution is timestamped with at least one pair of fields time_first and time_last (indicating the time an observable was seen via passive DNS replication) or zone_time_first and zone_time_list (indicating the time an observable was seen via zone file import) which is used as a Sighting.observed_time. The Sighting.sensor field depends on the time pair used and has a value Passive DNS replication or Zone file import correspondingly. If both pairs are presented, time_first and time_last pair is used.

• If Aggregated Mode is on, all resolutions for the last 90 days generate a single CTIM Sighting with unique values from the resolution rdata or rrname fields linked as Sighting observed relations.

  • The sum of values from the resolution count is used as a Sighting.count.
  • The time of investigation is used as a Sighting.observed_time.start_time.

NOTE. If there are too many results, timeout or other performance issues may occur.