README.md

gcp-kmsenv

Detect variable from environment variable or GCP Cloud KMS.

You can access KMS with a syntax similar to os.Getenv

Requirements

Base64 encoded ciphertext

Encrypt credential with gcloud kms encrypt and convert with base64.

e.g.

echo -n SECRET_ACCESS_TOKEN | gcloud --project PROJECT_NAME kms encrypt --plaintext-file=- --ciphertext-file=- --location=global --keyring=KEY_RING_NAME --key=KEY_NAME | base64

After that, register with the environment variable starting with KMS_. (e.g. KMS_ACCESS_TOKEN )

Service account

Add IAM role roles/cloudkms.cryptoKeyDecrypter to service account if necessary.

Example

export SOME_KEY="env_value"
export KMS_ACCESS_TOKEN="base64_encoded_ciphertext"

package main

import "github.com/sue445/gcp-kmsenv"

func main() {
    keyringKeyName := "projects/PROJECT_NAME/locations/global/keyRings/KEY_RING_NAME/cryptoKeys/KEY_NAME"
    k, err := kmsenv.NewKmsEnv(keyringKeyName)
    if err != nil {
        panic(err)
    }

    // get from environment variable
    value, err := k.GetFromEnvOrKms("SOME_KEY", false)
    // => "env_value"

    // get and decrypt from KMS
    // NOTE. prefix `KMS_` is needless
    access_token, err := k.GetFromEnvOrKms("ACCESS_TOKEN", false)
    // => "SECRET_ACCESS_TOKEN"

    // When key is not found in both environment variable and KMS, returned empty string (not error)
    value, err := k.GetFromEnvOrKms("INVALID_KEY", false)
    // => ""

    // When key is not found in both environment variable and KMS, returned error
    value, err := k.GetFromEnvOrKms("INVALID_KEY", true)
    // => error
}

ProTip

Securely embed secret values in app.yaml for Google App Engine

# app.yaml
runtime: go113

env_variables:
  KMS_ACCESS_TOKEN: "THIS_IS_BASE64_ENCODED_CIPHER_TEXT"

Development

cp .envrc .envrc.example
vi .envrc