Configure HashiCorp Vault as a vault backend with GCP service account authentication

Before you can configure the Vault entity in Kong Gateway, you must configure HashiCorp Vault to authenticate clients using GCP service account JWTs and store a secret.

Create configuration files

First, create the primary configuration file config.hcl for HashiCorp Vault in the ./vault directory:

listener "tcp" {
  address     = "0.0.0.0:8200"
  tls_disable = true
}

storage "file" {
  path = "./vault/data"
}

ui = true

Then, create the HashiCorp Vault policy file rw-secrets.hcl in the ./vault directory:

path "*" {
  capabilities = ["create", "read", "update", "delete", "list", "sudo"]
}

Configure the Vault and store a secret

1. In a new terminal, start HashiCorp Vault:

   vault server -config=./vault/config.hcl

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2. In your previous terminal, set the Vault address:

   export VAULT_ADDR="http://localhost:8200"

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3. Initialize the Vault:

   vault operator init -key-shares=1 -key-threshold=1

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   This outputs your unseal key and initial root token. Export them as environment variables:

   export HCV_UNSEAL_KEY='YOUR-UNSEAL-KEY'
   export DECK_HCV_TOKEN='YOUR-INITIAL-ROOT-TOKEN'

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4. Unseal your Vault:

   vault operator unseal $HCV_UNSEAL_KEY

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5. Log in to your Vault:

   vault login $DECK_HCV_TOKEN

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6. Write the policy to access secrets:

   vault policy write rw-secrets ./vault/rw-secrets.hcl

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7. Enable GCP authentication:

   vault auth enable gcp

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8. Create an IAM role that binds to Kong Gateway’s GCP service account:

   vault write auth/gcp/role/kong-role \
     type="iam" \
     bound_service_accounts="$GCP_SERVICE_ACCOUNT_EMAIL" \
     token_policies="rw-secrets"

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9. Enable the K/V secrets engine:

   vault secrets enable -path=kong kv

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10. Create a secret:

    vault kv put kong/headers/request header="x-kong:test"

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11. Confirm you can retrieve the secret through Vault:

    vault kv get kong/headers/request

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Find the internal IP for your VM:

hostname -I

Export the following environment variables before creating the Vault entity:

export HCV_HOST="YOUR VM INTERNAL IP"
export GCP_AUTH_ROLE=kong-role

Using decK, create a Vault entity in the kong.yaml file with the required parameters for HashiCorp Vault GCP IAM authentication:

curl -X POST "http://localhost:8001/vaults" \
     --no-progress-meter --fail-with-body  \
     -H "Content-Type: application/json" \
     --json '{
       "name": "hcv",
       "prefix": "hashicorp-vault",
       "description": "Storing secrets in HashiCorp Vault",
       "config": {
         "host": "'$HCV_HOST'",
         "kv": "v1",
         "mount": "kong",
         "port": 8200,
         "protocol": "http",
         "auth_method": "gcp_iam",
         "gcp_auth_role": "'$GCP_AUTH_ROLE'",
         "gcp_service_account": "'$GCP_SERVICE_ACCOUNT_EMAIL'",
         "gcp_jwt_exp": 900
       }
     }'

To validate that the secret was stored correctly in HashiCorp Vault, call a secret from your vault using the kong vault get command within the Data Plane container.

docker exec kong-quickstart-gateway kong vault get {vault://hashicorp-vault/headers/request/header}

If the vault was configured correctly, this command returns the value of the secret. You can use {vault://hashicorp-vault/headers/request/header} to reference the secret in any referenceable field.

For more information about supported secret types, see What can be stored as a secret.