LDAP secrets engine

The LDAP secrets engine provides management of LDAP credentials as well as dynamic creation of credentials. It supports integration with implementations of the LDAP v3 protocol, including OpenLDAP, Active Directory, and IBM Resource Access Control Facility (RACF).

The secrets engine has three primary features:

• Static Credentials
• Dynamic Credentials
• Service Account Check-Out

Setup

1. Enable the LDAP secret engine:

   $ vault secrets enable ldap
   

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   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 LDAP to generate passwords:

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

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   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 ldap/rotate-root
   

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   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.

Schemas

The LDAP Secret Engine supports three different schemas:

• openldap (default)
• racf
• ad

OpenLDAP

By default, the LDAP Secret Engine assumes the entry password is stored in userPassword. There are many object classes that provide userPassword including for example:

• organization
• organizationalUnit
• organizationalRole
• inetOrgPerson
• person
• posixAccount

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 ldap/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 ldap/config \
    binddn=$USERNAME \
    bindpass=$PASSWORD \
    url=ldaps://138.91.247.105 \
    schema=ad

Static credentials

Setup

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

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

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2. Request credentials for the "hashicorp" role:

   $ vault read ldap/static-cred/hashicorp
   

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Password rotation

Passwords can be managed in two ways:

• automatic time based rotation
• 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 ldap/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

To generate credentials:

$ vault read ldap/creds/dynamic-role
Key                    Value
---                    -----
lease_id               ldap/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
-

Service account Check-Out

Service account check-out provides a library of service accounts that can be checked out by a person or by machines. Vault will automatically rotate the password each time a service account is checked in. Service accounts can be voluntarily checked in, or Vault will check them in when their lending period (or, "ttl", in Vault's language) ends.

The service account check-out functionality works with various schemas, including OpenLDAP, Active Directory, and RACF. In the following usage example, the secrets engine is configured to manage a library of service accounts in an Active Directory instance.

First we'll need to enable the LDAP secrets engine and tell it how to securely connect to an AD server.

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

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

Our next step is to designate a set of service accounts for check-out.

$ vault write ldap/library/accounting-team \
    service_account_names=fizz@example.com,buzz@example.com \
    ttl=10h \
    max_ttl=20h \
    disable_check_in_enforcement=false

In this example, the service account names of fizz@example.com and buzz@example.com have already been created on the remote AD server. They've been set aside solely for Vault to handle. The ttl is how long each check-out will last before Vault checks in a service account, rotating its password during check-in. The max_ttl is the maximum amount of time it can live if it's renewed. These default to 24h, and both use duration format strings. Also by default, a service account must be checked in by the same Vault entity or client token that checked it out. However, if this behavior causes problems, set disable_check_in_enforcement=true.

When a library of service accounts has been created, view their status at any time to see if they're available or checked out.

$ vault read ldap/library/accounting-team/status
Key                 Value
---                 -----
buzz@example.com    map[available:true]
fizz@example.com    map[available:true]

To check out any service account that's available, simply execute:

$ vault write -f ldap/library/accounting-team/check-out
Key                     Value
---                     -----
lease_id                ldap/library/accounting-team/check-out/EpuS8cX7uEsDzOwW9kkKOyGW
lease_duration          10h
lease_renewable         true
password                ?@09AZKh03hBORZPJcTDgLfntlHqxLy29tcQjPVThzuwWAx/Twx4a2ZcRQRqrZ1w
service_account_name    fizz@example.com

If the default ttl for the check-out is higher than needed, set the check-out to last for a shorter time by using:

$ vault write ldap/library/accounting-team/check-out ttl=30m
Key                     Value
---                     -----
lease_id                ldap/library/accounting-team/check-out/gMonJ2jB6kYs6d3Vw37WFDCY
lease_duration          30m
lease_renewable         true
password                ?@09AZerLLuJfEMbRqP+3yfQYDSq6laP48TCJRBJaJu/kDKLsq9WxL9szVAvL/E1
service_account_name    buzz@example.com

This can be a nice way to say, "Although I can have a check-out for 24 hours, if I haven't checked it in after 30 minutes, I forgot or I'm a dead instance, so you can just check it back in."

If no service accounts are available for check-out, Vault will return a 400 Bad Request.

$ vault write -f ldap/library/accounting-team/check-out
Error writing data to ldap/library/accounting-team/check-out: Error making API request.

URL: POST http://localhost:8200/v1/ldap/library/accounting-team/check-out
Code: 400. Errors:

* No service accounts available for check-out.

To extend a check-out, renew its lease.

$ vault lease renew ldap/library/accounting-team/check-out/0C2wmeaDmsToVFc0zDiX9cMq
Key                Value
---                -----
lease_id           ldap/library/accounting-team/check-out/0C2wmeaDmsToVFc0zDiX9cMq
lease_duration     10h
lease_renewable    true

Renewing a check-out means its current password will live longer, since passwords are rotated anytime a password is checked in either by a caller, or by Vault because the check-out ttl ends.

To check a service account back in for others to use, call:

$ vault write -f ldap/library/accounting-team/check-in
Key          Value
---          -----
check_ins    [fizz@example.com]

Most of the time this will just work, but if multiple service accounts are checked out by the same caller, Vault will need to know which one(s) to check in.

$ vault write ldap/library/accounting-team/check-in service_account_names=fizz@example.com
Key          Value
---          -----
check_ins    [fizz@example.com]

To perform a check-in, Vault verifies that the caller should be able to check in a given service account. To do this, Vault looks for either the same entity ID used to check out the service account, or the same client token.

If a caller is unable to check in a service account, or simply doesn't try, Vault will check it back in automatically when the ttl expires. However, if that is too long, service accounts can be forcibly checked in by a highly privileged user through:

$ vault write -f ldap/library/manage/accounting-team/check-in
Key          Value
---          -----
check_ins    [fizz@example.com]

Or, alternatively, revoking the secret's lease has the same effect.

$ vault lease revoke ldap/library/accounting-team/check-out/PvBVG0m7pEg2940Cb3Jw3KpJ
All revocation operations queued successfully!

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"
}

LDAP password policy

The LDAP 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

API

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