Server-Side Object Encryption with Azure Key Vault Root KMS

MinIO Server-Side Encryption (SSE) protects objects as part of write operations, allowing clients to take advantage of server processing power to secure objects at the storage layer (encryption-at-rest). SSE also provides key functionality to regulatory and compliance requirements around secure locking and erasure.

MinIO SSE uses Key Encryption Service (KES) and an external root Key Management Service (KMS) for performing secured cryptographic operations at scale. The root KMS provides stateful and secured storage of External Keys (EK) while KES is stateless and derives additional cryptographic keys from the root-managed EK.

This procedure assumes you have access to a Kubernetes cluster with an active MinIO Operator installation, with a cluster-accessible Azure Key Vault service as the external root KMS. As part of this procedure, you will:

Use the MinIO Operator Console to create or manage a MinIO Tenant.
Access the Encryption settings for that tenant and configure SSE using Azure Key Vault as the root KMS.
Create a new EK on Vault for use with SSE.
Configure automatic bucket-default SSE-KMS.

For production baremetal environments, see the MinIO on Linux documentation for tutorials on configuring MinIO with KES and Azure Key Vault.

Important

Enabling SSE on a MinIO deployment automatically encrypts the backend data for that deployment using the default encryption key.

MinIO requires access to KES and the root KMS to decrypt the backend and start normally. You cannot disable KES later or “undo” the SSE configuration at a later point.

Prerequisites

MinIO Kubernetes Operator and Plugin

The procedures on this page requires a valid installation of the MinIO Kubernetes Operator and assumes the local host has a matching installation of the MinIO Kubernetes Operator. This procedure assumes the latest stable Operator and Plugin version 5.0.4.

See Deploy the MinIO Operator for complete documentation on deploying the MinIO Operator.

Azure Key Vault

This procedure assumes familiarity with Azure Key Vault. The Key Vault Quickstart provides a sufficient foundation for the purposes of this procedure.

MinIO specifically requires the following Azure settings or configurations:

Register an application for KES (e.g. minio-kes). Note the Application (client) ID, Directory (tenant) ID, and Client credentials. You may need to create the client credentials secret and copy the Secret Value for use in this procedure.
Create an Access Policy for use by KES. The policy must have the following Secret Permissions:
- Get
- List
- Set
- Delete
- Purge
Set the Principal for the new policy to the KES Application ID.

Deploy MinIO Tenant with Server-Side Encryption using Azure Key Vault

1) Access the Operator Console

Use the kubectl minio proxy command to temporarily forward traffic between the local host machine and the MinIO Operator Console:

kubectl minio proxy

The command returns output similar to the following:

Starting port forward of the Console UI.

To connect open a browser and go to http://localhost:9090

Current JWT to login: TOKEN

Open your browser to the specified URL and enter the JWT Token into the login page. You should see the Tenants page:

Click the + Create Tenant to start creating a MinIO Tenant.

2) Complete the Encryption Section

Reference the Deploy a MinIO Tenant procedure for complete documentation of other Tenant settings.

To enable SSE with Azure Key Vault during Tenant deployment, select the Encryption section and toggle the switch to Enabled. You can then select the Azure Radio button to display the Azure Key Vault configuration settings.

MinIO Operator Console - Create a Tenant - Encryption Section

An asterisk * marks required fields. The following table provides general guidance for those fields:

Field	Description
Endpoint	The hostname or IP address for the Azure Key Vault service to use for SSE. The MinIO Tenant KES pods must have network access to the specified endpoint.
Tenant ID Client ID Client Secret	Specify the Azure Key Vault credentials the MinIO Tenant should use when authenticating to the service. Review the Azure Prerequisites for instructions on generating these values.

Field

Description

Endpoint

The hostname or IP address for the Azure Key Vault service to use for SSE.

The MinIO Tenant KES pods must have network access to the specified endpoint.

Tenant ID
Client ID
Client Secret

Specify the Azure Key Vault credentials the MinIO Tenant should use when authenticating to the service. Review the Azure Prerequisites for instructions on generating these values.

Once you have completed the Azure Key Vault configuration, you can finish any remaining sections of Tenant Deployment.

3) Generate a New Encryption Key

Unseal Vault Before Creating Key

You must unseal the backing Vault instance before creating new encryption keys. See the Vault documentation on Seal/Unseal for more information.

MinIO requires that the EK for a given bucket or object exist on the root KMS before performing SSE operations using that key. You can use the mc admin kms key create command against the MinIO Tenant.

You must ensure your local host can access the MinIO Tenant pods and services before using mc to manage the Tenant. For hosts internal to the Kubernetes cluster, you can use the service DNS name. For hosts external to the Kubernetes cluster, specify the hostname of the service exposed by Ingress, Load Balancer, or similar Kubernetes network control component.

Run this command in a separate Terminal or Shell:

# Replace '-n minio' with the namespace of the MinIO deployment
# If you deployed the Tenant without TLS you may need to change the port range

# You can validate the ports in use by running
#  kubectl get svc/minio -n minio

kubectl port forward svc/minio 443:443 -n minio

The following commands in a new Terminal or Shell window:

Connect a local mc client to the Tenant.
Create the encryption key.

See Quickstart for instructions on installing mc on your local host.

# Replace USERNAME and PASSWORD with a user on the tenant with administrative permissions
# such as the root user

mc alias add k8s https://localhost:443 ROOTUSER ROOTPASSWORD

# Replace my-new-key with the name of the key you want to use for SSE-KMS
mc admin kms key create k8s encrypted-bucket-key

4) Enable SSE-KMS for a Bucket

You can use either the MinIO Tenant Console or the MinIO mc CLI to enable bucket-default SSE-KMS with the generated key:

MinIO Tenant Console

Connect to the MinIO Tenant Console service and log in. For clients internal to the Kubernetes cluster, you can specify the service DNS name. For clients external to the Kubernetes cluster, specify the hostname of the service exposed by Ingress, Load Balancer, or similar Kubernetes network control component.

Once logged in, create a new Bucket and name it to your preference. Select the Gear icon to open the management view.

Select the pencil icon next to the Encryption field to open the modal for configuring a bucket default SSE scheme.

Select SSE-KMS, then enter the name of the key created in the previous step.

Once you save your changes, try to upload a file to the bucket. When viewing that file in the object browser, note that in the sidebar the metadata includes the SSE encryption scheme and information on the key used to encrypt that object. This indicates the successful encrypted state of the object.

MinIO CLI

Use the MinIO API Service to create a new alias for the MinIO deployment. You can then use the mc encrypt set command to enable SSE-KMS encryption for a bucket:

mc alias set k8s https://minio.minio-tenant-1.svc.cluster-domain.example:443 ROOTUSER ROOTPASSWORD

mc mb k8s/encryptedbucket
mc encrypt set SSE-KMS encrypted-bucket-key k8s/encryptedbucket

For clients external to the Kubernetes cluster, specify the hostname of the service exposed by Ingress, Load Balancer, or similar Kubernetes network control component.

Write a file to the bucket using mc cp or any S3-compatible SDK with a PutObject function. You can then run mc stat on the file to confirm the associated encryption metadata.

Configuration Reference for Azure Key Vault Root KMS

The following section describes each of the Key Encryption Service (KES) configuration settings for using Azure Key Vault as the root Key Management Service (KMS) for SSE:

Important

Starting with https://github.com/minio/minio/releases/tag/RELEASE.2023-02-17T17-52-43Z, MinIO requires expanded KES permissions for functionality. The example configuration in this section contains all required permissions.

YAML Overview

Fields with ${<STRING>} use the environment variable matching the <STRING> value. You can use this functionality to set credentials without writing them to the configuration file.

The YAML assumes a minimal set of permissions for the MinIO deployment accessing KES. As an alternative, you can omit the policy.minio-server section and instead set the ${MINIO_IDENTITY} hash as the ${ROOT_IDENTITY}.

address: 0.0.0.0:7373
root: ${ROOT_IDENTITY}

tls:
  key: kes-server.key
  cert: kes-server.cert

policy:
  minio-server:
    allow:
    - /v1/key/create/*
    - /v1/key/generate/*
    - /v1/key/decrypt/*
    - /v1/key/bulk/decrypt
    - /v1/key/list
    - /v1/status
    - /v1/metrics
    - /v1/log/audit
    - /v1/log/error
    identities:
    - ${MINIO_IDENTITY}

keys:
  - name: "minio-encryption-key-alpha"
  - name: "minio-encryption-key-baker"
  - name: "minio-encryption-key-charlie"

keystore:
  azure:
    keyvault:
      endpoint: "https://<keyvaultinstance>.vault.azure.net"
      credentials:
        tenant_id: "${TENANTID}" # The directory/tenant UUID
        client_id: "${CLIENTID}" # The application/client UUID
        client_secret: "${CLIENTSECRET}" # The Active Directory secret for the application

Reference

Key	Description
`address`	The network address and port the KES server listens to on startup. Defaults to port `7373` on all host network interfaces.
`root`	The identity for the KES superuser (`root`) identity. Clients connecting with a TLS certificate whose hash (`kes identity of client.cert`) matches this value have access to all KES API operations. Specify `disabled` to remove the root identity and rely only on the `policy` configuration for controlling identity and access management to KES.
`tls`	The TLS private key and certificate used by KES for establishing TLS-secured communications. Specify the full path for both the private `.key` and public `.cert` to the `key` and `cert` fields, respectively.
`policy`	Specify one or more policies to control access to the KES server. MinIO SSE requires access to the following KES cryptographic APIs: `/v1/key/create/` `/v1/key/generate/` `/v1/key/decrypt/` Specifying additional keys does not expand MinIO SSE functionality and may violate security best practices around providing unnecessary client access to cryptographic key operations. You can restrict the range of key names MinIO can create as part of performing SSE by specifying a prefix before the ``. For example, `minio-sse-*` only grants access to create, generate, or decrypt keys using the `minio-sse-` prefix. KES uses mTLS to authorize connecting clients by comparing the hash of the TLS certificate against the `identities` of each configured policy. Use the `kes identity of` command to compute the identity of the MinIO mTLS certificate and add it to the `policy.<NAME>.identities` array to associate MinIO to the `<NAME>` policy.
`keys`	Specify an array of keys which must exist on the root KMS for KES to successfully start. KES attempts to create the keys if they do not exist and exits with an error if it fails to create any key. KES does not accept any client requests until it completes validation of all specified keys.
`keystore.azure.keyvault`	The configuration for the Azure Key Vault `endpoint` - The hostname for the Key Vault service. `credentials` - Replace the `credentials` with the credentials for the Active Directory application as which KES authenticates. The specified credentials must have the appropriate permissions