Overview

A CLI tool to perform syntactic and semantic validation of YAML files.

$ nac-validate --help

 Usage: nac-validate [OPTIONS] PATHS...

 A CLI tool to perform syntactic and semantic validation of YAML files.

╭─ Arguments ────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ *    paths      PATHS...  List of paths pointing to YAML files or directories. [default: None] [required]                                                              │
╰────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
╭─ Options ──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ --verbosity   -v      [DEBUG|INFO|WARNING|ERROR|CRITICAL]  Verbosity level. [env var: NAC_VALIDATE_VERBOSITY] [default: WARNING]                                       │
│ --schema      -s      FILE                                 Path to schema file. [env var: NAC_VALIDATE_SCHEMA] [default: .schema.yaml]                                 │
│ --rules       -r      DIRECTORY                            Path to directory with semantic validation rules. [env var: NAC_VALIDATE_RULES] [default: .rules]           │
│ --output      -o      FILE                                 Write merged content from YAML files to a new YAML file. [env var: NAC_VALIDATE_OUTPUT] [default: None]     │
│ --non-strict                                               Accept unexpected elements in YAML files. [env var: NAC_VALIDATE_NON_STRICT]                                │
│ --version                                                  Display version number.                                                                                     │
│ --help                                                     Show this message and exit.                                                                                 │
╰────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯

Syntactic validation is done by basic YAML syntax validation (e.g., indentation) and by providing a Yamale schema and validating all YAML files against that schema. Semantic validation is done by providing a set of rules (implemented in Python) which are then validated against the YAML data. Every rule is implemented as a Python class and should be placed in a .py file located in the --rules path.

Each .py file must have a single class named Rule. This class must have the following attributes: id, description and severity. It must implement a classmethod() named match that has a single function argument data which is the data read from all YAML files. It can optionally also have a second argument schema which would then provide the Yamale schema. It should return a list of strings, one for each rule violation with a descriptive message. A sample rule can be found below.

class Rule:
    id = "101"
    description = "Verify child naming restrictions"
    severity = "HIGH"

    @classmethod
    def match(cls, data):
        results = []
        try:
            for child in data["root"]["children"]:
                if child["name"] == "FORBIDDEN":
                    results.append("root.children.name" + " - " + str(child["name"]))
        except KeyError:
            pass
        return results

Installation

Python 3.10+ is required to install nac-validate. Don’t have Python 3.10 or later? See Python 3 Installation & Setup Guide.

nac-validate can be installed in a virtual environment using pip:

pip install nac-validate

Pre-Commit Hook

The tool can be integrated via a pre-commit hook with the following config (.pre-commit-config.yaml), assuming the default values (.schema.yaml, .rules/) are appropriate:

repos:
  - repo: https://github.com/netascode/nac-validate
    rev: v0.3.0
    hooks:
      - id: nac-validate

In case the schema or validation rules are located somewhere else the required CLI arguments can be added like this:

repos:
  - repo: https://github.com/netascode/nac-validate
    rev: v0.3.0
    hooks:
      - id: nac-validate
        args:
          - '-s'
          - 'my_schema.yaml'
          - '-r'
          - 'rules/'

Ansible Vault Support

Values can be encrypted using Ansible Vault. This requires Ansible (ansible-vault command) to be installed and the following two environment variables to be defined:

export ANSIBLE_VAULT_ID=dev
export ANSIBLE_VAULT_PASSWORD=Password123

ANSIBLE_VAULT_ID is optional, and if not defined will be omitted.

Additional Tags

Reading Environment Variables

The !env YAML tag can be used to read values from environment variables.

root:
  name: !env VAR_NAME