envexec

envexec helps to provision an application by taking values from sources like Vault and bringing them as environment variables.

Features

• Out of process (no code dependency)
• Works with any app written in any language
• One small static binary (💙 Golang)
• Familiar configuration format, with versions
• No supervising, just replaces the process with exec
• Simple Docker integration

Usage

Docker

The easiest way to embed envexec into your Docker image is to just copy the binary from the prebuilt image:

FROM alpine:3.18

COPY --from=hypnoglow/envexec:latest-scratch /envexec /usr/local/bin/envexec

ENTRYPOINT ["envexec", "--"]
CMD ["echo", "Hello from envexec!"]

An alternative approach is to build your image with envexec image as a base:

FROM hypnoglow/envexec:latest-alpine

ENTRYPOINT ["envexec", "--"]
CMD ["echo", "Hello from envexec!"]

NOTE: Using "latest" tags is not recommended. Prefer tagged versions.

See examples for more info.

Providers

Vault

To fetch secrets from Vault and export values as environment variables, you need to prepare a spec. Example:

apiVersion: envexec/v1alpha1
kind: VaultSecrets
secrets:
  - path: secret/namespace/service/some
    key: api_key
    env: SOME_API_KEY
  - path: secret/namespace/service/db
    key: password
    env: DB_PASSWORD

Store this spec in the file vaultsecrets.yaml.

Next you need to prepare environment variables to authenticate in Vault. This depends on the Vault Auth Method. Lets consider the simplest token authentication method:

export VAULT_ADDR="https://vault.company.tld"
export VAULT_METHOD="token"
export VAULT_TOKEN="put-vault-token-here"

Now you just run your app through envexec:

envexec --spec-file vaultsecrets.yaml -- /usr/bin/env

Auth Methods

Token

See: https://www.vaultproject.io/docs/auth/token.html

export VAULT_ADDR="https://vault.company.tld"
export VAULT_METHOD="token"
export VAULT_TOKEN="put-vault-token-here"

envexec --spec-file vaultsecrets.yaml -- /usr/bin/env

Kubernetes

See: https://www.vaultproject.io/docs/auth/kubernetes.html

export VAULT_ADDR="https://vault.company.tld"
export VAULT_AUTH_METHOD="kubernetes"
export VAULT_AUTH_KUBERNETES_ROLE="foo-app"

envexec --spec-file vaultsecrets.yaml /usr/bin/env

Acknowledgements

Inspired by:

• https://github.com/hashicorp/envconsul
• https://github.com/channable/vaultenv