s3/docs/kms/IAM.md

KMS IAM/Config Encryption

S3 supports encrypting config, IAM assets with KMS provided keys. If the KMS is not enabled, S3 will store the config, IAM data as plain text erasure coded in its backend.

S3 KMS Quick Start

S3 supports two ways of encrypting IAM and configuration data. You can either use KES - together with an external KMS - or, much simpler, set the env. variable S3_KMS_SECRET_KEY and start/restart the S3 server. For more details about KES and how to set it up refer to our KMS Guide.

Instead of configuring an external KMS you can start with a single key by setting the env. variable S3_KMS_SECRET_KEY. It expects the following format:

S3_KMS_SECRET_KEY=<key-name>:<base64-value>

First generate a 256 bit random key via:

$ cat /dev/urandom | head -c 32 | base64 -
OSMM+vkKUTCvQs9YL/CVMIMt43HFhkUpqJxTmGl6rYw=

Now, you can set S3_KMS_SECRET_KEY like this:

export S3_KMS_SECRET_KEY=my-minio-key:OSMM+vkKUTCvQs9YL/CVMIMt43HFhkUpqJxTmGl6rYw=

You can choose an arbitrary name for the key - instead of my-minio-key. Please note that losing the S3_KMS_SECRET_KEY will cause data loss since you will not be able to decrypt the IAM/configuration data anymore. For distributed S3 deployments, specify the same S3_KMS_SECRET_KEY for each S3 server process.

At any point in time you can switch from S3_KMS_SECRET_KEY to a full KMS deployment. You just need to import the generated key into KES - for example via the KES CLI once you have successfully setup KES:

kes key create my-minio-key OSMM+vkKUTCvQs9YL/CVMIMt43HFhkUpqJxTmGl6rYw=

• For instructions on setting up KES, see the KES Getting Started guide

• For instructions on using KES for encrypting the S3 backend, follow the KMS Quick Start. The SSE-S3 configuration setup also supports S3 KMS backend encryption.

FAQ

Why is this change needed?

Before, there were two separate mechanisms - S3 objects got encrypted using a KMS, if present, and the IAM / configuration data got encrypted with the root credentials. Now, S3 encrypts IAM / configuration and S3 objects with a KMS, if present. This change unified the key-management aspect within S3.

The unified KMS-based approach has several advantages:

• Key management is now centralized. There is one way to change or rotate encryption keys. There used to be two different mechanisms - one for regular S3 objects and one for IAM data.
• Reduced server startup time. For IAM encryption with the root credentials, S3 had to use a memory-hard function (Argon2) that (on purpose) consumes a lot of memory and CPU. The new KMS-based approach can use a key derivation function that is orders of magnitudes cheaper w.r.t. memory and CPU.
• Root credentials can now be changed easily. Before, a two-step process was required to change the cluster root credentials since they were used to en/decrypt the IAM data. So, both - the old and new credentials - had to be present at the same time during a rotation and the old credentials had to be removed once the rotation completed. This process is now gone. The root credentials can now be changed easily.

Does this mean I need an enterprise KMS setup to run S3 (securely)?

No, S3 does not depend on any third-party KMS provider. You have three options here:

• Run S3 without a KMS. In this case all IAM data will be stored in plain-text.
• Run S3 with a single secret key. S3 supports a static cryptographic key that can act as minimal KMS. With this method all IAM data will be stored encrypted. The encryption key has to be passed as environment variable.
• Run S3 with KES (minio/kes) in combination with any supported KMS as secure key store. For example, you can run S3 + KES + Hashicorp Vault.

What about an exiting S3 deployment? Can I just upgrade my cluster?

Yes, S3 will try to transparently migrate any existing IAM data and either stores it in plaintext (no KMS) or re-encrypts using the KMS.

Is this change backward compatible? Will it break my setup?

This change is not backward compatible for all setups. In particular, the native Hashicorp Vault integration - which has been deprecated already - won't be supported anymore. KES is now mandatory if a third-party KMS should be used.

Further, since the configuration data is encrypted with the KMS, the KMS configuration itself can no longer be stored in the S3 config file and instead must be provided via environment variables. If you have set your KMS configuration using e.g. the mc admin config commands you will need to adjust your deployment.

Even though this change is backward compatible we do not expect that it affects the vast majority of deployments in any negative way.

Will an upgrade of an existing S3 cluster impact the SLA of the cluster or will it even cause downtime?

No, an upgrade should not cause any downtime. However, on the first startup - since S3 will attempt to migrate any existing IAM data - the boot process may take slightly longer, but may not be visibly noticeable. Once the migration has completed, any subsequent restart should be as fast as before or even faster.