minio/docs/kms/README.md

# KMS Quickstart Guide [![Slack](https://slack.minio.io/slack?type=svg)](https://slack.minio.io)

Minio uses a key-management-system (KMS) to support SSE-S3. If a client requests SSE-S3 or auto-encryption
is enabled the Minio server encrypts each object with an unique object key which is protected by a master key
managed by the KMS. Usually many/all object keys are protected by a single master key.

Minio supports two different KMS concepts:
 - External KMS:
   Minio can be configured to use an external KMS i.e. [Hashicorp Vault](https://www.vaultproject.io/).
   An external KMS decouples Minio as storage system from key-management. An external KMS can
   be managed by a dedicated security team and allows to grant/deny access to (certain) objects
   by en/disabling the corresponding master keys on demand.
   However, an external KMS causes configuration and management overhead. 
 - Direct KMS master keys:
   Minio can also be configured to directly use a master key specified by the ENV. variable `MINIO_SSE_MASTER_KEY`.
   Direct master keys are useful if the storage backend is not on the same machine as the Minio server - e.g.
   if network drives or Minio gateway is used - and an external KMS would cause too much management overhead.  
   Note: If the Minio server machine is ever compromised, then the master key must also be 
   treated as compromised.

**Important:**  
If multiple minio server are configured as [gateways](https://github.com/minio/minio/blob/master/docs/gateway/README.md)
pointing to the *same* backend - for example the same NAS storage - than the KMS configuration **must** be equal for
all gateways. Otherwise one gateway may not be able to decrypt objects created by another gateway. It's the operators 
responsibility to ensure that.

## Get started

### 1. Prerequisites
Install Minio - [Minio Quickstart Guide](https://docs.minio.io/docs/minio-quickstart-guide).

### 2. Setup a KMS

Either use Hashicorp Vault as external KMS or specify a master key directly depending on your use case.

#### 2.1 Setup Hashicorp Vault

Here is a sample quick start for configuring vault with a transit backend and Approle with correct policy 

Minio requires the following Vault setup:
- The [transit backend](https://www.vaultproject.io/api/secret/transit/index.html) configured with a named encryption key-ring
- [AppRole](https://www.vaultproject.io/docs/auth/approle.html) based authentication with read/update policy for transit backend. In particular, read and update policy are required for the [Generate Data Key](https://www.vaultproject.io/api/secret/transit/index.html#generate-data-key) endpoint and [Decrypt Data](https://www.vaultproject.io/api/secret/transit/index.html#decrypt-data) endpoint.

**2.1.1 Start Vault server in dev mode**

In dev mode, Vault server runs in-memory and starts unsealed. Note that running Vault in dev mode is insecure and any data stored in the Vault is lost upon restart.
```
vault server -dev
```

**2.1.2 Set up vault transit backend and create an app role**

```
cat > vaultpolicy.hcl <<EOF
path "transit/datakey/plaintext/my-minio-key" { 
  capabilities = [ "read", "update"]
}
path "transit/decrypt/my-minio-key" { 
  capabilities = [ "read", "update"]
}
path "transit/encrypt/my-minio-key" { 
  capabilities = [ "read", "update"]
}

EOF

export VAULT_ADDR='http://127.0.0.1:8200'
vault auth enable approle    # enable approle style auth
vault secrets enable transit  # enable transit secrets engine
vault write -f  transit/keys/my-minio-key  #define a encryption key-ring for the transit path
vault policy write minio-policy ./vaultpolicy.hcl  #define a policy for AppRole to access transit path
vault write auth/approle/role/my-role token_num_uses=0  secret_id_num_uses=0  period=60s # period indicates it is renewable if token is renewed before the period is over
# define an AppRole
vault write auth/approle/role/my-role policies=minio-policy # apply policy to role
vault read auth/approle/role/my-role/role-id  # get Approle ID
vault write -f auth/approle/role/my-role/secret-id

```

The AppRole ID, AppRole Secret Id, Vault endpoint and Vault key name can now be used to start minio server with Vault as KMS.

**2.1.3 Vault Environment variables**

You'll need the Vault endpoint, AppRole ID, AppRole SecretID and encryption key-ring name defined in step 2.1.2

```sh
export MINIO_SSE_VAULT_APPROLE_ID=9b56cc08-8258-45d5-24a3-679876769126
export MINIO_SSE_VAULT_APPROLE_SECRET=4e30c52f-13e4-a6f5-0763-d50e8cb4321f
export MINIO_SSE_VAULT_ENDPOINT=https://vault-endpoint-ip:8200
export MINIO_SSE_VAULT_KEY_NAME=my-minio-key
export MINIO_SSE_VAULT_AUTH_TYPE=approle
minio server ~/export
```

Optionally set `MINIO_SSE_VAULT_CAPATH` to a directory of PEM-encoded CA cert files to use mTLS for client-server authentication.

```
export MINIO_SSE_VAULT_CAPATH=/home/user/custom-certs
```

Optionally set `MINIO_SSE_VAULT_NAMESPACE` if AppRole and Transit Secrets engine have been scoped to Vault Namespace

```
export MINIO_SSE_VAULT_NAMESPACE=ns1
```

Note: If [Vault Namespaces](https://learn.hashicorp.com/vault/operations/namespaces) are in use, MINIO_SSE_VAULT_NAMESPACE variable needs to be set before setting approle and transit secrets engine.



#### 2.2 Specify a master key

A KMS master key consists of a master-key ID (CMK) and the 256 bit master key encoded as HEX value separated by a `:`.
A KMS master key can be specified directly using:

```sh
export MINIO_SSE_MASTER_KEY=my-minio-key:6368616e676520746869732070617373776f726420746f206120736563726574
```

### 3. Test your setup

To test this setup, start minio server with environment variables set in Step 3, and server is ready to handle SSE-S3 requests.

### Auto-Encryption

Minio can also enable auto-encryption **if** a valid KMS configuration is specified and the storage backend supports
encrypted objects. Auto-Encryption, if enabled, ensures that all uploaded objects are encrypted using the specified
KMS configuration.

Auto-Encryption is useful especially if the Minio operator wants to ensure that objects are **never** stored in 
plaintext - for example if sensitive data is stored on public cloud storage.

To enable auto-encryption either set the ENV. variable: 

```sh
export MINIO_SSE_AUTO_ENCRYPTION=on
```

Note: Auto-Encryption only affects non-SSE-C requests since objects uploaded using SSE-C are already encrypted
and S3 only allows either SSE-S3 or SSE-C but not both for the same object.   


# Explore Further

- [Use `mc` with Minio Server](https://docs.minio.io/docs/minio-client-quickstart-guide)
- [Use `aws-cli` with Minio Server](https://docs.minio.io/docs/aws-cli-with-minio)
- [Use `s3cmd` with Minio Server](https://docs.minio.io/docs/s3cmd-with-minio)
- [Use `minio-go` SDK with Minio Server](https://docs.minio.io/docs/golang-client-quickstart-guide)
- [The Minio documentation website](https://docs.minio.io)