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OpenLDAP Secrets Engine

The OpenLDAP secret engine allows management of LDAP entry passwords as well as dynamic creation of credentials. This engine supports interacting with Active Directory which is compatible with LDAP v3.

This plugin currently supports LDAP v3.

Quick Setup

  1. Enable the OpenLDAP secret engine:

    $ vault secrets enable openldap

    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 OpenLDAP to generate passwords:

    $ vault write openldap/config \
    binddn=$USERNAME \
    bindpass=$PASSWORD \
    url=ldaps://138.91.247.105

    Note: it's recommended a dedicated entry management account be created specifically for Vault.

  3. Rotate the root password so only Vault knows the credentials:

    $ vault write -f openldap/rotate-root

    Note: it's not possible to retrieve the generated password once rotated by Vault. It's recommended a dedicated entry management account be created specifically for Vault.

Password Generation

This engine previously allowed configuration of the length of the password that is generated when rotating credentials. This mechanism was deprecated in Vault 1.5 in favor of password policies. This means the length field should no longer be used. The following password policy can be used to mirror the same behavior that the length field provides:

length=<length>
rule "charset" {
  charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
}

Static Roles

Setup

  1. Configure a static role that maps a name in Vault to an entry in OpenLDAP. Password rotation settings will be managed by this role.

    $ vault write openldap/static-role/hashicorp \
    dn='uid=hashicorp,ou=users,dc=hashicorp,dc=com' \
    username='hashicorp' \
    rotation_period="24h"

  2. Request credentials for the "hashicorp" role:

    $ vault read openldap/static-cred/hashicorp

LDAP Password Policy

The OpenLDAP secret engine does not hash or encrypt passwords prior to modifying values in LDAP. This behavior can cause plaintext passwords to be stored in LDAP.

To avoid having plaintext passwords stored, the LDAP server should be configured with an LDAP password policy (ppolicy, not to be confused with a Vault password policy). A ppolicy can enforce rules such as hashing plaintext passwords by default.

The following is an example of an LDAP password policy to enforce hashing on the data information tree (DIT) dc=hashicorp,dc=com:

dn: cn=module{0},cn=config
changetype: modify
add: olcModuleLoad
olcModuleLoad: ppolicy
 
dn: olcOverlay={2}ppolicy,olcDatabase={1}mdb,cn=config
changetype: add
objectClass: olcPPolicyConfig
objectClass: olcOverlayConfig
olcOverlay: {2}ppolicy
olcPPolicyDefault: cn=default,ou=pwpolicies,dc=hashicorp,dc=com
olcPPolicyForwardUpdates: FALSE
olcPPolicyHashCleartext: TRUE
olcPPolicyUseLockout: TRUE

Schema

The OpenLDAP Secret Engine supports three different schemas: openldap (default), racf and ad.

OpenLDAP

By default the OpenLDAP Secret Engine assumes the entry password is stored in userPassword. The following object classes provide userPassword:

Resource Access Control Facility (RACF)

For managing IBM's Resource Access Control Facility (RACF) security system, the secret engine must be configured to use the schema racf.

Generated passwords must be 8 characters or less to support RACF. The length of the password can be configured using a password policy:

$ vault write openldap/config \
    binddn=$USERNAME \
    bindpass=$PASSWORD \
    url=ldaps://138.91.247.105 \
    schema=racf \
    password_policy=racf_password_policy

Active Directory (AD)

For managing Active Directory instances, the secret engine must be configured to use the schema ad.

$ vault write openldap/config \
    binddn=$USERNAME \
    bindpass=$PASSWORD \
    url=ldaps://138.91.247.105 \
    schema=ad

Password Rotation

Passwords can be managed in two ways:

  • automatic time based rotation, and
  • manual rotation.

Auto Password Rotation

Passwords will automatically be rotated based on the rotation_period configured in the static role (minimum of 5 seconds). When requesting credentials for a static role, the response will include the time before the next rotation (ttl).

Auto-rotation is currently only supported for static roles. The binddn account used by Vault should be rotated using the rotate-root endpoint to generate a password only Vault will know.

Manual Rotation

Static roles can be manually rotated using the rotate-role endpoint. When manually rotated the rotation period will start over.

Deleting Static Roles

Passwords are not rotated upon deletion of a static role. The password should be manually rotated prior to deleting the role or revoking access to the static role.

Dynamic Credentials

Setup

Dynamic credentials can be configured by calling the /role/:role_name endpoint:

$ vault write openldap/role/dynamic-role \
  creation_ldif=@/path/to/creation.ldif \
  deletion_ldif=@/path/to/deletion.ldif \
  rollback_ldif=@/path/to/rollback.ldif \
  default_ttl=1h \
  max_ttl=24h

Note: The rollback_ldif argument is optional, but recommended. The statements within rollback_ldif will be executed if the creation fails for any reason. This ensures any entities are removed in the event of a failure.

To generate credentials:

$ vault read openldap/creds/dynamic-role
Key                    Value
---                    -----
lease_id               openldap/creds/dynamic-role/HFgd6uKaDomVMvJpYbn9q4q5
lease_duration         1h
lease_renewable        true
distinguished_names    [cn=v_token_dynamic-role_FfH2i1c4dO_1611952635,ou=users,dc=learn,dc=example]
password               xWMjkIFMerYttEbzfnBVZvhRQGmhpAA0yeTya8fdmDB3LXDzGrjNEPV2bCPE9CW6
username               v_token_testrole_FfH2i1c4dO_1611952635

The distinguished_names field is an array of DNs that are created from the creation_ldif statements. If more than one LDIF entry is included, the DN from each statement will be included in this field. Each entry in this field corresponds to a single LDIF statement. No de-duplication occurs and order is maintained.

LDIF Entries

User account management is provided through LDIF entries. The LDIF entries may be a base64-encoded version of the LDIF string. The string will be parsed and validated to ensure that it adheres to LDIF syntax. A good reference for proper LDIF syntax can be found here.

Some important things to remember when crafting your LDIF entries:

  • There should not be any trailing spaces on any line, including empty lines
  • Each modify block needs to be preceded with an empty line
  • Multiple modifications for a dn can be defined in a single modify block. Each modification needs to close with a single dash (-)

Active Directory (AD)

For Active Directory, there are a few additional details that are important to remember:

To create a user programmatically in AD, you first add a user object and then modify that user to provide a password and enable the account.

  • Passwords in AD are set using the unicodePwd field. This must be proceeded by two (2) colons (::).

  • When setting a password programmatically in AD, the following criteria must be met:

    • The password must be enclosed in double quotes (" ")
    • The password must be in UTF16LE format
    • The password must be base64-encoded
    • Additional details can be found here

  • Once a user's password has been set, it can be enabled. AD uses the userAccountControl field for this purpose:

    • To enable the account, set userAccountControl to 512
    • You will likely also want to disable AD's password expiration for this dynamic user account. The userAccountControl value for this is: 65536
    • userAccountControl flags are cumulative, so to set both of the above two flags, add up the two values (512 + 65536 = 66048): set userAccountControl to 66048
    • See here for details on userAccountControl flags

sAMAccountName is a common field when working with AD users. It is used to provide compatibility with legacy Windows NT systems and has a limit of 20 characters. Keep this in mind when defining your username_template. See here for additional details.

With regard to adding dynamic users to groups, AD doesn't let you directly modify a user's memberOf attribute. The member attribute of a group and memberOf attribute of a user are linked attributes. Linked attributes are forward link/back link pairs, with the forward link able to be modified. In the case of AD group membership, the group's member attribute is the forward link. In order to add a newly-created dynamic user to a group, we also need to issue a modify request to the desired group and update the group membership with the new user.

Active Directory LDIF Example

The various *_ldif parameters are templates that use the go template language. A complete LDIF example for creating an Active Directory user account is provided here for reference:

dn: CN={{.Username}},OU=HashiVault,DC=adtesting,DC=lab
changetype: add
objectClass: top
objectClass: person
objectClass: organizationalPerson
objectClass: user
userPrincipalName: {{.Username}}@adtesting.lab
sAMAccountName: {{.Username}}

dn: CN={{.Username}},OU=HashiVault,DC=adtesting,DC=lab
changetype: modify
replace: unicodePwd
unicodePwd::{{ printf "%q" .Password | utf16le | base64 }}
-
replace: userAccountControl
userAccountControl: 66048
-

dn: CN=test-group,OU=HashiVault,DC=adtesting,DC=lab
changetype: modify
add: member
member: CN={{.Username}},OU=HashiVault,DC=adtesting,DC=lab
-

API

The OpenLDAP secrets engine has a full HTTP API. Please see the OpenLDAP secrets engine API docs for more details.

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