Collection of git hooks for Terraform to be used with pre-commit framework

How to install

1. Install dependencies

• pre-commit
• terraform-docs required for terraform_docs hooks. GNU awk is required if using terraform-docs older than 0.8.0 with Terraform 0.12.
• TFLint required for terraform_tflint hook.
• TFSec required for terraform_tfsec hook.
• coreutils required for terraform_validate hook on macOS (due to use of realpath).
• checkov required for checkov hook.
• terrascan required for terrascan hook.

or build and use the Docker image locally as mentioned below in the Run section.

MacOS

brew install pre-commit gawk terraform-docs tflint tfsec coreutils checkov terrascan

Ubuntu 18.04

sudo apt update
sudo apt install -y gawk unzip software-properties-common
sudo add-apt-repository ppa:deadsnakes/ppa
sudo apt install -y python3.7 python3-pip
pip3 install pre-commit
curl -L "$(curl -s https://api.github.com/repos/terraform-docs/terraform-docs/releases/latest | grep -o -E "https://.+?-linux-amd64.tar.gz")" > terraform-docs.tgz && tar xzf terraform-docs.tgz && chmod +x terraform-docs && sudo mv terraform-docs /usr/bin/
curl -L "$(curl -s https://api.github.com/repos/terraform-linters/tflint/releases/latest | grep -o -E "https://.+?_linux_amd64.zip")" > tflint.zip && unzip tflint.zip && rm tflint.zip && sudo mv tflint /usr/bin/
curl -L "$(curl -s https://api.github.com/repos/tfsec/tfsec/releases/latest | grep -o -E "https://.+?tfsec-linux-amd64")" > tfsec && chmod +x tfsec && sudo mv tfsec /usr/bin/
curl -L "$(curl -s https://api.github.com/repos/accurics/terrascan/releases/latest | grep -o -E "https://.+?_Linux_x86_64.tar.gz")" > terrascan.tar.gz && tar -xf terrascan.tar.gz terrascan && rm terrascan.tar.gz && sudo mv terrascan /usr/bin/
python3.7 -m pip install -U checkov

2. Install the pre-commit hook globally

Note: not needed if you use the Docker image

DIR=~/.git-template
git config --global init.templateDir ${DIR}
pre-commit init-templatedir -t pre-commit ${DIR}

3. Add configs and hooks

Step into the repository you want to have the pre-commit hooks installed and run:

git init
cat <<EOF > .pre-commit-config.yaml
repos:
- repo: git://github.com/antonbabenko/pre-commit-terraform
  rev: <VERSION> # Get the latest from: https://github.com/antonbabenko/pre-commit-terraform/releases
  hooks:
    - id: terraform_fmt
    - id: terraform_docs
EOF

4. Run

After pre-commit hook has been installed you can run it manually on all files in the repository

pre-commit run -a

or you can also build and use the provided Docker container, which wraps all dependencies by

# first building it
docker build -t pre-commit .
# and then running it in the folder
# with the terraform code you want to check by executing
docker run -v $(pwd):/lint -w /lint pre-commit run -a

Available Hooks

There are several pre-commit hooks to keep Terraform configurations (both *.tf and *.tfvars) and Terragrunt configurations (*.hcl) in a good shape:

Hook name	Description
terraform_fmt	Rewrites all Terraform configuration files to a canonical format.
terraform_validate	Validates all Terraform configuration files.
terraform_docs	Inserts input and output documentation into README.md. Recommended.
terraform_docs_without_aggregate_type_defaults	Inserts input and output documentation into README.md without aggregate type defaults.
terraform_docs_replace	Runs terraform-docs and pipes the output directly to README.md (requires terraform-docs v0.10.0 or later)
terraform_tflint	Validates all Terraform configuration files with TFLint.
terragrunt_fmt	Rewrites all Terragrunt configuration files (*.hcl) to a canonical format.
terragrunt_validate	Validates all Terragrunt configuration files (*.hcl)
terraform_tfsec	TFSec static analysis of terraform templates to spot potential security issues.
checkov	checkov static analysis of terraform templates to spot potential security issues.
terrascan	terrascan Detect compliance and security violations.

Check the source file to know arguments used for each hook.

Notes about terraform_docs hooks

1. terraform_docs and terraform_docs_without_aggregate_type_defaults will insert/update documentation generated by terraform-docs framed by markers:

<!-- BEGINNING OF PRE-COMMIT-TERRAFORM DOCS HOOK -->

<!-- END OF PRE-COMMIT-TERRAFORM DOCS HOOK -->

if they are present in README.md.

1. terraform_docs_replace replaces the entire README.md rather than doing string replacement between markers. Put your additional documentation at the top of your main.tf for it to be pulled in. The optional --dest argument lets you change the name of the file that gets created/modified. This hook requires terraform-docs v0.10.0 or later.

   1. Example:

   hooks:
     - id: terraform_docs_replace
       args: ['--sort-by-required', '--dest=TEST.md']

2. It is possible to pass additional arguments to shell scripts when using terraform_docs and terraform_docs_without_aggregate_type_defaults. Send pull-request with the new hook if there is something missing.

Notes about terraform_tflint hooks

1. terraform_tflint supports custom arguments so you can enable module inspection, deep check mode etc.

   1. Example:

   hooks:
     - id: terraform_tflint
       args: ['--args=--deep']

   In order to pass multiple args, try the following:

    - id: terraform_tflint
      args:
         - '--args=--deep'
         - '--args=--enable-rule=terraform_documented_variables'

2. When you have multiple directories and want to run tflint in all of them and share single config file it is impractical to hard-code the path to .tflint.hcl file. The solution is to use __GIT_WORKING_DIR__ placeholder which will be replaced by terraform_tflint hooks with Git working directory (repo root) at run time. For example:

   hooks:
     - id: terraform_tflint
       args:
         - '--args=--config=__GIT_WORKING_DIR__/.tflint.hcl'

Notes about terraform_tfsec hooks

1. terraform_tfsec will consume modified files that pre-commit passes to it, so you can perform whitelisting of directories or files to run against via files pre-commit flag

   1. Example:

   hooks:
     - id: terraform_tfsec
       files: ^prd-infra/

   The above will tell pre-commit to pass down files from the prd-infra/ folder only such that the underlying tfsec tool can run against changed files in this directory, ignoring any other folders at the root level

2. To ignore specific warnings, follow the convention from the documentation.

   1. Example:

   resource "aws_security_group_rule" "my-rule" {
       type = "ingress"
       cidr_blocks = ["0.0.0.0/0"] #tfsec:ignore:AWS006
   }

Notes about terraform_validate hooks

1. terraform_validate supports custom arguments so you can pass supported no-color or json flags.

   1. Example:

   hooks:
     - id: terraform_validate
       args: ['--args=-json']

   In order to pass multiple args, try the following:

    - id: terraform_validate
      args:
         - '--args=-json'
         - '--args=-no-color'

2. terraform_validate also supports custom environment variables passed to the pre-commit runtime

   1. Example:

   hooks:
     - id: terraform_validate
       args: ['--envs=AWS_DEFAULT_REGION="us-west-2"']

   In order to pass multiple args, try the following:

    - id: terraform_validate
      args:
         - '--envs=AWS_DEFAULT_REGION="us-west-2"'
         - '--envs=AWS_ACCESS_KEY_ID="anaccesskey"'
         - '--envs=AWS_SECRET_ACCESS_KEY="asecretkey"'

3. It may happen that Terraform working directory (.terraform) already exists but not in the best condition (eg, not initialized modules, wrong version of Terraform, etc). To solve this problem you can find and delete all .terraform directories in your repository using this command:

   find . -type d -name ".terraform" -print0 | xargs -0 rm -r

   terraform_validate hook will try to reinitialize them before running terraform validate command.

Notes for developers

1. Python hooks are supported now too. All you have to do is:
   1. add a line to the console_scripts array in entry_points in setup.py
   2. Put your python script in the pre_commit_hooks folder

Enjoy the clean, valid, and documented code!

Authors

This repository is managed by Anton Babenko with help from these awesome contributors.

License

MIT licensed. See LICENSE for full details.