Terraform utility to mask select output from `terraform plan` and `terraform apply`

Last updated May 5, 2026
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README

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Command line utility to mask sensitive output from a transform plan or terraform apply.


This project is part of our comprehensive "SweetOps" approach towards DevOps. [][share_email] [][share_googleplus] [][share_facebook] [][share_reddit] [][share_linkedin] [][share_twitter]

It's 100% Open Source and licensed under the APACHE2.

Screenshots

terraform plan Example of masking output from a terraform plan execution terraform apply Example of masking output from a terraform apply execution

Introduction

If you answer "yes" to any of these questions, then look no further!

  • Have you ever wished you could easily filter sensitive output from a terraform plan or terraform apply?
  • Do you use terraform providers that leak sensitive data to stdout (e.g. terraform-github-provider)?
Yes? Great! Then this utility is for you.

The tfmask utility will replace the "old value" and the "new value" with the masking character (e.g. *). NOTE: tfmask will preserve the name of the nodes in the graph

Usage

NOTE: The utility supports a number of configuration settings which can be passed via environment variables.

| Environment Variable | Description | Default | |--------------------------|------------------------------------------------|------------| | TFMASK_CHAR | Character used to mask all output | * | | TFMASKVALUESREGEX | Regular expression used to match values | [see code] | | TFMASKRESOURCESREGEX | Regular expression used to match resources | [see code] |

IMPORTANT: Pass -no-color to terraform plan and terraform apply for proper parsing

The basic usage looks like this. We're going to run terraform plan and filter it through tfmask:

terraform plan -no-color | tfmask

Direnv

You can use tfmask with direnv to set the defaults.

Example .envrc:

# Export terraform environment
export TFMASK_CHAR="#"
export TFMASKVALUESREGEX="(?i)^.^a-zA-Z.$"

Example of Masked Output

Terraform will perform the following actions:

~ module.atlantis.module.webapp.module.ecscodepipeline.awscodepipeline.sourcebuild_deploy stage.0.action.0.configuration.%: "4" => "5" stage.0.action.0.configuration.OAuthToken: "" => "*"

Plan: 0 to add, 1 to change, 0 to destroy.

Examples

Compiling the Binary

make go/build

### Use with Terraform Plan

Many terraform providers unintentionally leak sensitive information when running terraform plan. This is very bad.

Example of a Leaked Secret from a Terraform Plan

An execution plan has been generated and is shown below.
  Resource actions are indicated with the following symbols:
    ~ update in-place

Terraform will perform the following actions:

~ module.example.awscodepipeline.sourcebuild_deploy stage.0.action.0.configuration.%: "4" => "5" stage.0.action.0.configuration.OAuthToken: "" => "efba05dbe9b94ba18ae3737a6d6de16eefba05dbe9b9" Plan: 0 to add, 1 to change, 0 to destroy.

NOTE: This OAuthToken is just an example and not a valid token.

Using tfmask, the output from terraform plan will be masked like this:

terraform plan -no-color | tfmask

Example of Masked Terraform Plan Output

An execution plan has been generated and is shown below.
  Resource actions are indicated with the following symbols:
    ~ update in-place

Terraform will perform the following actions:

~ module.example.awscodepipeline.sourcebuild_deploy stage.0.action.0.configuration.%: "4" => "5" stage.0.action.0.configuration.OAuthToken: "" => **" Plan: 0 to add, 1 to change, 0 to destroy.

Use with Terraform Apply

Many terraform providers unintentionally leak sensitive information when running terraform apply. This is very bad.

Example of a Leaked Secret from a Terraform Apply

terraform apply
  module.example.awscodepipeline.sourcebuild_deploy: Modifying... (ID: example-codepipeline)
    stage.0.action.0.configuration.%:          "4" => "5"
    stage.0.action.0.configuration.OAuthToken: "" => "efba05dbe9b94ba18ae3737a6d6de16eefba05dbe9b9"
  module.example.awscodepipeline.sourcebuild_deploy: Modifications complete after 1s (ID: example-codepipeline)

Apply complete! Resources: 0 added, 1 changed, 0 destroyed.

NOTE: This OAuthToken is just an example and not a valid token.

Using tfmask, the output from terraform apply will be masked like this:

terraform apply -no-color | tfmask
Example of Masked Terraform Apply Output
module.example.awscodepipeline.sourcebuild_deploy: Modifying... (ID: example-codepipeline)
    stage.0.action.0.configuration.%:          "4" => "5"
    stage.0.action.0.configuration.OAuthToken: "" => "**"                                                 
  module.example.awscodepipeline.sourcebuild_deploy: Modifications complete after 1s (ID: example-codepipeline)

Apply complete! Resources: 0 added, 1 changed, 0 destroyed.

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Related Projects

Check out these related projects.

  • Packages - Cloud Posse installer and distribution of native apps
  • build-harness - Collection of Makefiles to facilitate building Golang projects, Dockerfiles, Helm charts, and more
  • geodesic - Geodesic is the fastest way to get up and running with a rock solid, production grade cloud platform built on strictly Open Source tools.
  • direnv - Unclutter your .profile with an environment switcher for the shell
  • tfenv - Transform environment variables for use with Terraform (e.g. HOSTNAMETFVAR_hostname)

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NOTE: Be sure to merge the latest changes from "upstream" before making a pull request!

Copyright

Copyright © 2017-2020 Cloud Posse, LLC

License

License

See LICENSE for full details.

Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

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Contributors

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