threatcl

Threat Modeling with HCL

What happened to hcltm?

hcltm has been renamed to threatcl. Welcome!

Overview

[!TIP] Want to read the new documentation? Head over to threatcl.dev

There are many different ways in which a threat model can be documented. From a simple text file, to more in-depth word documents, to fully instrumented threat models in a centralised solution. Two of the most valuable attributes of a threat model are being able to clearly document the threats, and to be able to drive valuable change.

threatcl aims to provide a DevOps-first approach to documenting a system threat model by focusing on the following goals:

Simple text-file format
Simple cli-driven user experience
Integration into version control systems (VCS)

This repository is the home of the threatcl cli software. The threatcl spec is based on HCL2, HashiCorp's Configuration Language, which aims to be "pleasant to read and write for humans, and a JSON-based variant that is easier for machines to generate and parse". The threatcl spec lives at github.com/threatcl/spec. Combining the threatcl cli software and the threatcl spec allows practitioners to define a system threat model in HCL, for example:

threatmodel "Tower of London" {
  description = "A historic castle"
  author = "@xntrik"

  attributes {
    new_initiative = "true"
    internet_facing = "true"
    initiative_size = "Small"
  }

  information_asset "crown jewels" {
    description = "including the imperial state crown"
    information_classification = "Confidential"
  }

  usecase {
    description = "The Queen can fetch the crown"
  }

  third_party_dependency "community watch" {
    description = "The community watch helps guard the premise"
    uptime_dependency = "degraded"
  }

  threat "Crown theft" {
    description = "Someone who isn't the Queen steals the crown"
    impacts = ["Confidentiality"]

    control "Guards" {
      description = "Trained guards patrol tower"
      risk_reduction = 75
    }
  }

  data_flow_diagram_v2 "dfd name" {
    // ... see below for more information
  }

}

See Data Flow Diagram for more information on how to construct data flow diagrams that may be converted to PNGs automatically.

To see an example of how to reference pre-defined control libraries for the OWASP Proactive Controls and AWS Security Checklist see examples/tm3.hcl. We also have the MITRE ATT&CK Controls here.

You can also include an external threatmodel into your own, to reference and use all its information. You can see examples/including-example/corp-app.hcl as an example.

To see a full description of the spec, see here or run:

threatcl generate boilerplate

threatcl will also process JSON files, but the only caveat is that import modules and variables won't work. You can see examples/tm1.json as an example.

Why HCL?

HCL is the primary configuration language used in the products by HashiCorp, in-particularly, Terraform - their open-source Infrastructure-as-Code software. I worked at HashiCorp for a while and the language really grew on me, plus, if DevOps and Software engineers are using the language, then simplifying how they document threat models aligns with threatcl's goals.

You can use threatcl with JSON, but you lose some of the features. For more, see the examples/ folder.

Why not just document them in MD?

I liked the idea of using a format that could be programmatically interacted with.

Kudos and References

One of the features of threatcl is the automatic generation of data flow diagrams from HCL files. This leverages the go-dfd package by Marqeta and Blake Hitchcock. Definitely check out their blog post on Threat models at the speed of DevOps.

Additionally I'd like to extend thanks to Jamie Finnigan and Talha Tariq at HashiCorp for allowing me to continue working on this open-source tool even after I'd finished up with HashiCorp.

Also thanks to the IriusRisk folks for the OpenThreatModel specification.

threatcl cli

Installation

Download the latest version from releases and move the threatcl binary into your PATH.

Install with Homebrew

The following will add a local tap, and install threatcl with Homebrew

brew install threatcl

Run with Docker

docker run --rm -it ghcr.io/threatcl/threatcl:latest

Run with GitHub Actions

threatcl can be integrated directly into your GitHub repos with https://github.com/threatcl/threatcl-action. This is one of the ideal methods to manage your threat models, and helps meet the goal of integrating into your version control systems.

Building from Source

Clone this repository.
Change into the directory, threatcl
make bootstrap
make build

For further help on contributing to threatcl please see the CHANGELOG.md.

Usage

For help on any subcommands use the -h flag.

$ threatcl
Usage: threatcl [--version] [--help] <command> [<args>]

Available commands are:
    dashboard    Generate markdown files from existing HCL threatmodel file(s)
    dfd          Generate Data Flow Diagram PNG or DOT files from existing HCL threatmodel file(s)
    export       Export threat models into other formats
    generate     Generate an HCL Threat Model
    list         List Threatmodels found in HCL file(s)
    mcp          Model Context Protocol (MCP) server for threatcl
    query        Execute GraphQL queries against threat model data
    server       Start a GraphQL API server for threat models
    terraform    Parse output from 'terraform show -json'
    validate     Validate existing HCL Threatmodel file(s)
    view         View existing HCL Threatmodel file(s)

(Optional) Config file

Most of the threatcl commands have a -config flag that allows you to specify a config.hcl file. HCL within this file may be used to overwrite some of threatcl's default attributes. These are listed below:

Initiative Sizes - defaults to "Undefined", "Small", "Medium", "Large"
Default Initiative Size - defaults to "Undefined
Information Classifications - defaults to "Restricted", "Confidential", "Public"
Default Information Classification - defaults to "Confidential"
Impact Types - defaults to "Confidentiality", "Integrity", "Availability"
STRIDE Elements - defaults to "Spoofing", "Tampering", "Info Disclosure", "Denial Of Service", "Elevation Of Privilege"
Uptime Dependency Classifications - defaults to "none", "degraded", "hard", "operational"
Default Uptime Depency Classification - defaults to "none"

For example:

initiative_sizes = ["S", "M", "L"]
default_initiative_size = "M"
info_classifications = ["1", "2"]
default_info_classification = "1"
impact_types = ["big", "small"]
strides = ["S", "T"]
uptime_dep_classifications = ["N", "D"]
default_uptime_dep_classification = "N"

If you modify these attributes, you'll need to remember to provide the config file for other operations, as this may impact validation or dashboard creation.

List and View

The threatcl list and threatcl view commands can be used to list and view data from threatcl spec HCL files.

$ threatcl list examples/*
#  File              Threatmodel      Author
1  examples/tm1.hcl  Tower of London  @xntrik
2  examples/tm1.hcl  Fort Knox        @xntrik
3  examples/tm2.hcl  Modelly model    @xntrik

Validate

The threatcl validate command is used to validate a threatcl spec HCL file.

$ threatcl validate examples/*
Validated 3 threatmodels in 3 files

Export

The threatcl export command is used to export a threatcl threat model (or models) into the native JSON representation (by default), or into the OTM json representation, or even back into hcl (Which is useful to output fresh HCL from dynamic threat models). You can also directly save them into a file with the -output flag.

$ threatcl export -format=otm examples/tm1.hcl
[{"assets":[{"description":"including the imperial state crown","id":"crown-jewels","name":"crown jewels","risk":{"availability":0,"confidentiality":0,"integrity":0}}],"mitigations":[{"attributes":{"implementation_notes":"They are trained to be guards as well","implemented":true},"description":"Lots of guards patrol the area","id":"lots-of-guards","name":"Lots of Guards","riskReduction":80}],"otmVersion":"0.2.0","project":{"attributes":{"initiative_size":"Small","internet_facing":true,"network_segment":"dmz","new_initiative":true},"description":"A historic castle","id":"tower-of-london","name":"Tower of London","owner":"@xntrik"},"threats":[{"categories":["Confidentiality"],"description":"Someone who isn't the Queen steals the crown","id":"threat-1","name":"Threat 1","risk":{"impact":0,"likelihood":null}}]},{"assets":[{"description":"Lots of gold","id":"gold","name":"Gold","risk":{"availability":0,"confidentiality":0,"integrity":0}}],"mitigations":[{"attributes":{"implemented":true},"description":"A larg

Threatcl

Install / Use

README