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A simple extension to Pydantic BaseSettings that can retrieve secrets from Hashicorp Vault

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Pydantic-Vault

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A simple extension to Pydantic BaseSettings that can retrieve secrets from a KV v2 secrets engine in Hashicorp Vault

Getting started

Starting with Pydantic 1.8, custom settings sources are officially supported.

You can create a normal BaseSettings class, and define the customise_sources() method to load secrets from your Vault instance using the vault_config_settings_source function:

import os

from pydantic import BaseSettings, Field, SecretStr
from pydantic_vault import vault_config_settings_source

class Settings(BaseSettings):
    username: str = Field(..., vault_secret_path="path/to/secret", vault_secret_key="my_user")
    password: SecretStr = Field(..., vault_secret_path="path/to/secret", vault_secret_key="my_password")

    class Config:
        vault_url: str = "https://vault.tld"
        vault_token: SecretStr = os.environ["VAULT_TOKEN"]
        vault_namespace: str = "your/namespace"  # Optional, pydantic-vault supports Vault namespaces (for Vault Enterprise)
        vault_secret_mount_point: str = "secrets"  # Optional, if your KV v2 secrets engine is not available at the default "secret" mount point

        @classmethod
        def customise_sources(
                cls,
                init_settings,
                env_settings,
                file_secret_settings,
        ):
            # This is where you can choose which settings sources to use and their priority
            return (
                init_settings,
                env_settings,
                vault_config_settings_source,
                file_secret_settings
            )

settings = Settings()
# These variables will come from the Vault secret you configured
settings.username
settings.password.get_secret_value()


# Now let's pretend we have already set the USERNAME in an environment variable
# (see the Pydantic documentation for more information and to know how to configure it)
# With the priority order we defined above, its value will override the Vault secret
os.environ["USERNAME"] = "my user"

settings = Settings()
settings.username  # "my user", defined in the environment variable
settings.password.get_secret_value()  # the value set in Vault

Documentation

Field additional parameters

You might have noticed that we import Field directly from Pydantic. Pydantic-Vault doesn't add any custom logic to it, which means you can still use everything you know and love from Pydantic.

The additional parameters Pydantic-Vault uses are:

Parameter name Required Description
vault_secret_path Yes The path to your secret in Vault
vault_secret_key Yes The key to use in the secret

For example, if you create a secret database/prod with a key password and a value of a secret password, you would use

password: SecretStr = Field(..., vault_secret_path="database/prod", vault_secret_key="password")

Authentication

For now Pydantic-Vault only supports direct token authentication, that is you must authenticate using your method of choice then pass the resulting Vault token to your Settings class.

Support is planned for Approle and Kubernetes authentication methods.

Configuration

In your Settings.Config class you can configure the following elements:

Settings name Required Description
customise_sources() Yes You need to implement this function to use Vault as a settings source, and choose the priority order you want
vault_url Yes Your Vault URL
vault_token Yes A token allowing to connect to Vault (retrieve it with any auth method you want)
vault_namespace No Your Vault namespace (if you use one, requires Vault Enterprise)
vault_secret_mount_point No The mount point of the KV v2 secrets engine, if different from the default "secret" mount point

You can also configure everything available in the original Pydantic BaseSettings class.

Order of priority

Thanks to the new feature in Pydantic 1.8 that allows you to customize settings sources, you can choose the order of priority you want.

Here are some examples:

from pydantic import BaseSettings
from pydantic_vault import vault_config_settings_source

class Settings(BaseSettings):
    """
    In descending order of priority:
      - arguments passed to the `Settings` class initializer
      - environment variables
      - Vault variables
      - variables loaded from the secrets directory, such as Docker Secrets
      - the default field values for the `Settings` model
    """
    class Config:
        @classmethod
        def customise_sources(
                cls,
                init_settings,
                env_settings,
                file_secret_settings,
        ):
            return (
                init_settings,
                env_settings,
                vault_config_settings_source,
                file_secret_settings
            )


class Settings(BaseSettings):
    """
    In descending order of priority:
      - Vault variables
      - environment variables
      - variables loaded from the secrets directory, such as Docker Secrets
      - the default field values for the `Settings` model
    Here we chose to remove the "init arguments" source,
    and move the Vault source up before the environment source
    """
    class Config:
        @classmethod
        def customise_sources(
                cls,
                init_settings,
                env_settings,
                file_secret_settings,
        ):
            return (
                vault_config_settings_source,
                env_settings,
                file_secret_settings
            )

License

Pydantic-Vault is available under the MIT license.

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