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Vault key management service
Vault KMS
50

The Vault key management service (KMS) provides key management and access control for your secrets. The {{% vendor/name %}} Vault KMS offers the transit secrets engine to sign, verify, encrypt, decrypt, and rewrap information.

Vault doesn't store the data sent to the transit secrets engine, so it can be viewed as encryption as a service. To store secrets such as API keys, create sensitive environment variables.

Supported versions

{{% major-minor-versions-note configMinor="true" %}}

{{< image-versions image="vault-kms" status="supported" environment="grid" >}}

{{% relationship-ref-intro %}}

{{< codetabs >}} +++ title= Service environment variables +++

{{% service-values-change %}}

VAULT_SERVICE_USERNAME=
VAULT_SERVICE_SCHEME=http
VAULT_SERVICE_SERVICE=vault-kms
VAULT_SERVICE_FRAGMENT=
VAULT_SERVICE_IP=123.456.78.90
VAULT_SERVICE_INSTANCE_IPS=['123.456.78.90']
VAULT_SERVICE_HOSTNAME=azertyuiopqsdfghjklm.vault-kms.service._.eu-1.{{< vendor/urlraw "hostname" >}}
VAULT_SERVICE_PORT=8200
VAULT_SERVICE_CLUSTER=azertyuiopqsdf-main-afdwftq
VAULT_SERVICE_HOST=vault_secret.internal
VAULT_SERVICE_REL=manage_keys
VAULT_SERVICE_PATH=/
VAULT_SERVICE_QUERY={'is_master': True}
VAULT_SERVICE_PASSWORD=ChangeMe
VAULT_SERVICE_EPOCH=0
VAULT_SERVICE_TYPE=vault-kms:{{% latest "vault-kms" %}}
VAULT_SERVICE_PUBLIC=false
VAULT_SERVICE_HOST_MAPPED=false

<--->

+++ title= PLATFORM_RELATIONSHIPS environment variable +++

For some advanced use cases, you can use the PLATFORM_RELATIONSHIPS environment variable. The structure of the PLATFORM_RELATIONSHIPS environment variable can be obtained by running {{< vendor/cli >}} relationships in your terminal:

{
    "username": "",
    "scheme": "http",
    "service": "vault-kms",
    "fragment": "",
    "ip": "123.456.78.90",
    "instance_ips": [
      "123.456.78.90"
    ],
    "hostname": "azertyuiopqsdfghjklm.vault-kms.service._.eu-1.{{< vendor/urlraw "hostname" >}}",
    "port": 8200,
    "cluster": "azertyuiopqsdf-main-7rqtwti",
    "host": "vault_secret.internal",
    "rel": "sign",
    "path": "\/",
    "query": {
        "is_master": true
    },
    "password": "ChangeMe",
    "type": "vault-kms:{{% latest "vault-kms" %}}",
    "public": false,
    "host_mapped": false
}

Here is an example of how to gather PLATFORM_RELATIONSHIPS environment variable information in a .environment file:

# Decode the built-in credentials object variable.
export RELATIONSHIPS_JSON=$(echo $PLATFORM_RELATIONSHIPS | base64 --decode)

# Set environment variables for individual credentials.
export APP_VAULT_HOST=="$(echo $RELATIONSHIPS_JSON | jq -r '.vault_secret[0].host')"

{{< /codetabs >}}

Usage example

{{% endpoint-description type="vault-kms" noApp=true %}}

  • {{< variable "SERVICE_NAME" >}} is the name you choose to identify the service.

  • {{< variable "VERSION" >}} is a supported version of the service.

  • {{< variable "ENDPOINT_ID" >}} is an identifier you choose for the endpoint.

  • {{< variable "KEY_NAME" >}} is the name of the key to be stored in the Vault KMS.

  • {{< variable "POLICY" >}} is one of the available policies based on what you want to accomplish.

  • The type is one of:

    • sign: for signing payloads, with the type ecdsa-p256
    • encrypt (for encryptchacha20-poly1305).

    The type can't be changed after creation.

You can create multiple endpoints, such as to have key management separate from key use.

512 MB is the minimum required disk space for the Vault KMS service.

{{% /endpoint-description %}}

Use Vault KMS

To connect your app to the Vault KMS, use a token that's defined in the service environment variables. With this token for authentication, you can use any of the policies you defined in your {{< vendor/configfile "services" >}} file.

{{% service-values-change %}}

The following examples use cURL as an example, which you could do in a hook or after accessing your app with SSH. Adapt the examples for your app's language.

Get the token

To make any calls to the Vault KMS, you need your token. Get it from the service environment variables:

echo ${{{< variable "RELATIONSHIP_NAME" >}}_PASSWORD}"

{{< variable "RELATIONSHIP_NAME" >}} is the relationship name you defined in your {{< vendor/configfile "app" >}} file.

You can also store this as a variable:

VAULT_TOKEN=${{{< variable "RELATIONSHIP_NAME" >}}_PASSWORD}

A given token is valid for one year from its creation.

Get the right URL

The service environment variable also contains the information you need to construct a URL for contacting the Vault KMS: the host and port.

Assign it to a variable as follows:

VAULT_URL=${{{< variable "RELATIONSHIP_NAME" >}}_HOST}:${{{< variable "RELATIONSHIP_NAME" >}}_PORT}

{{< variable "RELATIONSHIP_NAME" >}} is the name you defined in your {{< vendor/configfile "app" >}} file.

Manage your keys

Your key names are defined in your {{< vendor/configfile "services" >}} file. You can manage them if you've set an admin policy for them.

To get information on a key, such as its expiration date, run the following command:

curl \
  --header "X-Vault-Token: $VAULT_TOKEN" \
  http://"$VAULT_URL"/v1/transit/keys/"$KEY_NAME" | jq .

$KEY_NAME is the name in your {{< vendor/configfile "services" >}} file.

To rotate the version of your key, run the following command:

curl \
  --header "X-Vault-Token: $VAULT_TOKEN" \
  http://"$VAULT_URL"/v1/transit/keys/"$KEY_NAME">/rotate \
  --request POST

Sign and verify payloads

If you've set sign and verify policies, you can use your keys to sign and verify various payloads, such as a JSON Web Token (JWT) for authentication in your app. Note that all payloads (all plaintext data) must be base64-encoded.

To sign a specific payload, run the following command:

curl \
  --header "X-Vault-Token: $VAULT_TOKEN" \
  http://$VAULT_URL/v1/transit/sign/"$KEY_NAME"/sha2-512 \
  --data "{\"input\": \"$(echo SECRET | base64)\"}"

The string at the end of the URL denotes the specific hash algorithm used by the Vault KMS.

You get back a JSON object that includes the signature for the payload:

{
  "request_id": "a58b549f-1356-4028-d191-4c9cd585ca25",
  ...
  "data": {
    "key_version": 1,
    "signature": "vault-kms:v1:MEUCIAiN4UtXh..."
  },
  ...
}

You can then use data.signature to sign things such as a JWT.

To verify a payload, run the following command:

curl \
  --header "X-Vault-Token: $VAULT_TOKEN" \
  http://"$VAULT_URL"/v1/transit/verify/"$KEY_NAME"/sha2-512 \
  --data "
{
  \"input\": \"$(echo SECRET | base64)\",
  \"signature\": \"$SIGNATURE\"
}"

You get back a JSON object that includes whether or not the signature is valid:

{
  "request_id": "5b624718-fd9d-37f6-8b95-b387379d2648",
  ...
  "data": {
    "valid": true
  },
  ...
}

A true value means the signature matches and a false value means it doesn't.

Encrypt and decrypt data

If you've set encrypt and decrypt policies, you can use your keys to encrypt and decrypt any data you want. Note that all of plaintext data you work with must be base64-encoded.

To sign a specific payload, run the following command:

curl \
  --header "X-Vault-Token: $VAULT_TOKEN" \
  http://$VAULT_URL/v1/transit/encrypt/"$KEY_NAME" \
  --data "{\"plaintext\": \"$(echo SECRET | base64)\"}"

You get back a JSON object that includes your encrypted data:

{
  "request_id": "690d634a-a4fb-bdd6-9947-e895578b79d5",
  ...
  "data": {
    "ciphertext": "vault-kms:v1:LEtOWSwh3N...",
    "key_version": 1
  },
  ...
}

To decrypt data that you've already encrypted, run the following command:

curl \
  --header "X-Vault-Token: $VAULT_TOKEN" \
  http://"$VAULT_URL"/v1/transit/decrypt/"$KEY_NAME" \
  --data "
{
  \"ciphertext\": \"$CIPHERTEXT\"
}"

You get back a JSON object that your decrypted data base64-encoded:

{
  "request_id": "bbd411ca-6ed7-aa8b-8177-0f35055ce613",
  ...
  "data": {
    "plaintext": "U0VDUkVUCg=="
  },
  ...
}

To get the value un-encoded, add | jq -r ".data.plaintext" | base64 -d to the end of the curl command.

Rewrap encrypted data

If you have already encrypted data and you have changed your key version, you can rewrap the encrypted data with the new key.

Assuming $CIPHERTEXT stores your encrypted data (vault:v1:LEtOWSwh3N...), run the following command:

curl \
  --header "X-Vault-Token: $VAULT_TOKEN" \
  http://"$VAULT_URL"/v1/transit/rewrap/"$KEY_NAME" \
  --data "
{
  \"ciphertext\": \"$CIPHERTEXT\"
}"

In the JSON object that's returned, you can notice that the ciphertext is different (and now includes the new key version as a prefix) as is the key_version:

{
  ...
  "data": {
    "ciphertext": "vault-kms:v2:ICRi0yAlH...",
    "key_version": 2
  },
  ...
}

Policies

Policy Endpoint Capabilities Purpose
admin transit/keys/${KEY} read Access to key properties and various functions performed on keys such as rotation and deletion
transit/keys/${KEY}/* read, create, update, delete
sign transit/sign/${KEY}/${HASH_ALGORITHM} read, update Signing payloads with an existing key
verify transit/verify/${KEY}/${HASH_ALGORITHM} read, update Verifying already signed payloads
encrypt transit/encrypt/${KEY} read, update Encrypting data with an existing key
decrypt transit/decrypt/${KEY} read, update Decrypting data with an existing key
rewrap transit/rewrap/${KEY} read, update Re-encrypting data with a new key version without revealing the secret