---
layout: docs
page_title: Secret data transformation
description: >-
  Learn how to transform secret data with the Vault Secrets Operator.
---

# Secret data transformation

Utilizing advanced templating and data filters, the Vault Secrets Operator for Kubernetes (VSO) can
transform source secret data, secret metadata, resource labels and annotations into a format that is
compatible with your application. All secret data sources are supported. Secret transformations can
be specified directly within a secret custom resource (CR), or by references to one or more
[SecretTransformation](/vault/docs/platform/k8s/vso/api-reference#secrettransformation) custom resource
instances, or both.

## Templating

VSO utilizes the data-driven [templates for Golang](https://pkg.go.dev/text/template) to generate
secret data output. The template data input holds the secret data, secret metadata, resource labels
and annotations.

Templates are configured in a secret custom resource's
[spec.Destination.Transformation.Templates](/vault/docs/platform/k8s/vso/api-reference#transformation),
or in a SecretTransformation resource's [spec.templates](/vault/docs/platform/k8s/vso/api-reference#secrettransformationspec).

VSO provides access to a large library of template functions, some of which are documented
[below](#template-functions).

### Secret data input

Secret data is accessed through the `.Secrets` input member. It contains a map of secret
key-value pairs, which are assumed to be sensitive information fetched from a
[secret source](/vault/docs/platform/k8s/vso/sources).

For example, to include a password in your application's secret, you might specify
a template like:
```go
{{- printf "password=%s" (get .Secrets "password") -}}
```

### Secret metadata input

Secret metadata is accessed through the `.Metadata` input member. It contains a map of metadata key to
its value. The data should not contain any confidential information.

For example, to include a secret metadata value in your application's secret, you might specify
a template like:
```go
{{- printf "secretGroup=%s" (get .Metadata "secretGroup") -}}
```

### Resource annotations input

Resource annotations are accessed through the `.Annotations` input member. The annotations consist
of all `metadata.annotations` configured on the secret custom resource.

For example, to include a value from the resource's annotations in your application's secret, you
might specify a template like:
```go
{{- printf "host=%s" (get .Annotations "myapp.config/host") -}}
```

### Resource labels input

Resource labels are accessed through the `.Labels` input member. The labels consist
of all `metadata.labels` configured on the secret custom resource.

For example, to include a value from the resource's labels in your application's secret, you
might specify a template like:
```go
{{- printf "appType=%s" (get .Labels "appType") -}}
```

## Filters

Filters are used to control which source secret data fields are included in the destination secret's
data. They are specified as a set of exclude/include RE2 accepted [regular expressions](https://golang.org/s/re2syntax).

Filters are configured in the `excludes` and `includes` fields of a secret custom resource's
[spec.Destination.Transformation](/vault/docs/platform/k8s/vso/api-reference#transformation),
or in a SecretTransformation resource's [spec](/vault/docs/platform/k8s/vso/api-reference#secrettransformationspec).

All exclude patterns take precedence over any include patterns, and are never applied to templated keys.

## Examples

### Local transformation

A VaultDynamicSecret configured to sync Postgres database credentials from Vault to the Kubernetes
secret named `example-vds`.
```yaml
---
apiVersion: secrets.hashicorp.com/v1beta1
kind: VaultDynamicSecret
metadata:
  namespace: example-ns
  name: example-vds
  annotations:
    myapp.config/postgres-host: postgres-postgresql.postgres.svc.cluster.local:5432
spec:
  destination:
    create: true
    name: app-secret
    transformation:
      excludes:
       - .*
      templates:
        url:
          text: |
            {{- $host := get .Annotations "myapp.config/postgres-host" -}}
            {{- printf "postgresql://%s:%s@%s/postgres?sslmode=disable" (get .Secrets "username") (get .Secrets "password") $host -}}
  path: creds/dev-postgres
```

The resulting Kubernetes secret includes a single key named `url`, with a valid Postgres connection
URL as its value.

```yaml
url: postgresql://v-postgres-user:XUpah-password@postgres-postgresql.postgres.svc.cluster.local:5432/postgres?sslmode=disable
```

### Shared transformation

The following manifest contains shared transformation templates and filters. All `templates` it provides
will be included in the destination k8s secret. It also provides `sourceTemplates` that can be included
in any template text configured in a secret CR or within the same resource instance.

```yaml
---
apiVersion: secrets.hashicorp.com/v1beta1
kind: SecretTransformation
metadata:
  name: vso-templates
  namespace: example-vds
spec:
  excludes:
    - password|username
  templates:
    url:
      text: '{{- template "dbUrl" . -}}'
  sourceTemplates:
    - name: helpers
      text: |
        {{/*
          create a Java props from SecretInput for this app
        */}}
        {{- define "appProps" -}}
        {{- $host := get .Annotations "myapp.config/postgres-host" -}}
        {{- printf "db.host=%s\n" $host -}}
        {{- range $k, $v := .Secrets -}}
        {{- printf "db.%s=%s\n" $k $v -}}
        {{- end -}}
        {{- end -}}
        {{/*
          create a JSON config from SecretInput for this app
        */}}
        {{- define "appJson" -}}
        {{- $host := get .Annotations "myapp.config/postgres-host" -}}
        {{- $copy := .Secrets | mustDeepCopy -}}
        {{- $_ := set $copy "host" $host -}}
        {{- mustToPrettyJson $copy -}}
        {{- end -}}
        {{/*
          compose a Postgres URL from SecretInput for this app
        */}}
        {{- define "dbUrl" -}}
        {{- $host := get .Annotations "myapp.config/postgres-host" -}}
        {{- printf "postgresql://%s:%s@%s/postgres?sslmode=disable" (get .Secrets "username") (get .Secrets "password") $host -}}
        {{- end -}}
        {{/*
          get the app name from the VSO resource's label
        */}}
        {{- define "appName" -}}
        {{- get .Labels "myapp/name" -}}
        {{- end -}}
```

The following `VaultDynamicSecret` manifest references the `SecretTransformation` above.
All templates and filters from the reference object will be applied to the destination secret data.
```yaml
---
apiVersion: secrets.hashicorp.com/v1beta1
kind: VaultDynamicSecret
metadata:
  namespace: example-ns
  name: example-vds
  annotations:
    myapp.config/postgres-host: postgres-postgresql.postgres.svc.cluster.local:5432
spec:
  destination:
    create: true
    name: app-secret
    transformation:
      transformationRefs:
        - name: vso-templates
  path: creds/dev-postgres
```

The resulting Kubernetes secret includes a single key named `url`, with a valid Postgres connection
URL as its value

```yaml
url: postgresql://v-postgres-user:XUpah-password@postgres-postgresql.postgres.svc.cluster.local:5432/postgres?sslmode=disable
```

### Template functions

All template functions are provided by the [sprig](http://masterminds.github.io/sprig) library. Some common functions are mentioned below.
For the complete list of functions see [allowedSprigFuncs](https://github.com/hashicorp/vault-secrets-operator/blob/main/template/funcs.go#L26)

### String functions

`trim` removes any leading or trailing whitespaces from the input:
```
trim " host " -> `host`
```

### Encoding functions

`b64enc` base64 encodes an input value
```
b64enc "host" -> `aG9zdAo=`
```

`b64dec` base64 decodes an input value
```
b64dec "aG9zdAo=" -> `host`
```

### Map functions

`get` retrieves a value from a `map` input:
```
get .Secrets "baz" -> `qux`
```

Given a nested `map` input:

```json
{
  "foo": {
    "bar": "baz",
    "quz": "quux"
  }
}
```

`get` can retrieve a specific value:
```
get (get .Secrets "foo") "bar" -> `baz`
```

`dig` can also retrieve a specific value, or return a default if any of the keys
are not found:
```
dig "foo" "quz" "<not found>" .Secrets -> `quux`

dig "foo" "nux" "<not found>" .Secrets -> `<not found>`
```

## Related API references

- [Transformation](/vault/docs/platform/k8s/vso/api-reference#transformation)
- [HCPVaultSecretsApp](/vault/docs/platform/k8s/vso/api-reference#hcpvaultsecretsapp)
- [VaultDynamicSecret](/vault/docs/platform/k8s/vso/api-reference#vaultdynamicsecret)
- [VaultPKISecret](/vault/docs/platform/k8s/vso/api-reference#vaultpkisecret)
- [VaultStaticSecret](/vault/docs/platform/k8s/vso/api-reference#vaultstaticsecret)
- [SecretTransformation](/vault/docs/platform/k8s/vso/api-reference#secrettransformation)
