» Active Directory Secrets Engine

The Active Directory (AD) secrets engine is a plugin residing here.

The AD secrets engine rotates AD passwords dynamically, and is designed for a high-load environment where many instances may be accessing a shared password simultaneously. With a simple set up and a simple creds API, it doesn't require instances to be manually registered in advance to gain access. As long as access has been granted to the creds path via a method like AppRole, they're available.

Passwords are lazily rotated based on preset TTLs and can have a length configured to meet your needs.

» A Note on Lazy Rotation

To drive home the point that passwords are rotated "lazily", consider this scenario:

  • A password is configured with a TTL of 1 hour.
  • All instances of a service using this password are off for 12 hours.
  • Then they wake up and again request the password.

In this scenario, although the password TTL was set to 1 hour, the password wouldn't be rotated for 12 hours when it was next requested. "Lazy" rotation means passwords are rotated when all of the following conditions are true:

  • They are over their TTL
  • They are requested

Therefore, the AD TTL can be considered a soft contract. It's fulfilled when the given password is next requested.

To ensure your passwords are rotated as expected, we'd recommend you configure services to request each password at least twice as often as its TTL.

» A Note on Escaping

It is up to the administrator to provide properly escaped DNs. This includes the user DN, bind DN for search, and so on.

The only DN escaping performed by this method is on usernames given at login time when they are inserted into the final bind DN, and uses escaping rules defined in RFC 4514.

Additionally, Active Directory has escaping rules that differ slightly from the RFC; in particular it requires escaping of '#' regardless of position in the DN (the RFC only requires it to be escaped when it is the first character), and '=', which the RFC indicates can be escaped with a backslash, but does not contain in its set of required escapes. If you are using Active Directory and these appear in your usernames, please ensure that they are escaped, in addition to being properly escaped in your configured DNs.

For reference, see RFC 4514 and this TechNet post on characters to escape in Active Directory.

» Quick Setup

Most secrets engines must be configured in advance before they can perform their functions. These steps are usually completed by an operator or configuration management tool.

  1. Enable the Active Directory secrets engine:

    $ vault secrets enable ad
    Success! Enabled the ad secrets engine at: ad/
    

    By default, the secrets engine will mount at the name of the engine. To enable the secrets engine at a different path, use the -path argument.

  2. Configure the credentials that Vault uses to communicate with Active Directory to generate passwords:

    $ vault write ad/config \
        binddn=$USERNAME \
        bindpass=$PASSWORD \
        url=ldaps://138.91.247.105 \
        userdn='dc=example,dc=com'
    

    The $USERNAME and $PASSWORD given must have access to modify passwords for the given account. It is possible to delegate access to change passwords for these accounts to the one Vault is in control of, and this is usually the highest-security solution.

    If you'd like to do a quick, insecure evaluation, also set insecure_tls to true. However, this is NOT RECOMMENDED in a production environment. In production, we recommend insecure_tls is false (its default) and is used with a valid certificate.

  3. Configure a role that maps a name in Vault to an account in Active Directory. When applications request passwords, password rotation settings will be managed by this role.

    $ vault write ad/roles/my-application \
        service_account_name="my-application@example.com"
    
  4. Grant "my-application" access to its creds at ad/creds/my-application using an auth method like AppRole.

» FAQ

» What if someone directly rotates an Active Directory password that Vault is managing?

If an administrator at your company rotates a password that Vault is managing, the next time an application asks Vault for that password, Vault won't know it.

To maintain that application's up-time, Vault will need to return to a state of knowing the password. Vault will generate a new password, update it, and return it to the application(s) asking for it. This all occurs automatically, without human intervention.

Thus, we wouldn't recommend that administrators directly rotate the passwords for accounts that Vault is managing. This may lead to behavior the administrator wouldn't expect, like finding very quickly afterwards that their new password has already been changed.

The password ttl on a role can be updated at any time to ensure that the responsibility of updating passwords can be left to Vault, rather than requiring manual administrator updates.

» Why does Vault return the last password in addition to the current one?

Active Directory promises eventual consistency, which means that new passwords may not be propagated to all instances immediately. To deal with this, Vault returns the current password with the last password if it's known. That way, if a new password isn't fully operational, the last password can also be used.

» API

The Active Directory secrets engine has a full HTTP API. Please see the Active Directory secrets engine API for more details.