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Synchronizing Users from OpenLDAP

Last Updated: January 16th, 2020

Learn how to synchronize Duo users and groups from your existing OpenLDAP directory.


Import Duo user information directly from your on-premises OpenLDAP directory into Duo with Duo Security's Directory Sync feature. Directory attributes that may be populated include name, email address, phone numbers, and group memberships.

The Directory Sync feature is part of the Duo Beyond, Duo Access, and Duo MFA plans.

Directory Sync Updates Existing Users

Before executing any OpenLDAP synchronization with Duo, understand the effect that synchronization can have on accounts with the same name. Suppose that you already have some Duo users, and one or more of these users have the same username on your OpenLDAP server. Performing a synchronization will cause the existing Duo users' information to be merged with, and in some cases overwritten by the OpenLDAP information, such as email addresses in Duo changing to match the value stored in the synced directory.

Likewise, if you are doing OpenLDAP synchronization from multiple directories and there are non-unique usernames among those directories, there will be only one Duo user with that username, and each sync will update that Duo user with different information.

The same potential conflict applies to Duo groups. If an existing Duo group has the same name as a synced group, the synced group will overwrite the group information and membership in Duo.

Multiple syncs with different source directories that use non-unique group or user names may also produce undesired results, as each sync process will overwrite the group or user with different information.


Prerequisites necessary for OpenLDAP synchronization are as follows:

  • OpenLDAP server hostname or IP address, LDAP or LDAPS port, and base DN.
  • LDAPS or STARTTLS information and CA certificate for providing local network security, if desired.
  • A Windows 2012 or later, or modern Linux system (CentOS, Ubuntu, Red Hat) for running the Duo Authentication Proxy software.
  • Duo Authentication Proxy v2.6.0 or later (installation steps below).

In addition to the items above, Duo's OpenLDAP sync also has these directory requirements:

  • Synced groups must have the groupOfNames object class.
  • Synced groups must list their members by DN (directoryName) via the member attribute.
  • Synced groups must have a cn attribute, used as the Duo group name after import.
  • Synced groups must also have the attributes entrydn (used as the distinguished name) and entryuuid (the group unique identifier).
  • Synced users must list group memberships by DN using the memberOf attribute (via the memberOf overlay).
  • Synced users must have the organizationalPerson object class.

Verify that your OpenLDAP directory satisfies all the class and attribute requirements before attempting the sync. LDAP variants other than OpenLDAP may require additional configuration or modules to provide the necessary attributes to Duo.

Set Up Synchronization

Role required: Owner, Administrator, or User Manager.

Add the Directory

To start setting up Directory Sync:

  1. Log in to the Duo Admin Panel and click Users in the left side bar. Then click Directory Sync on the submenu or click the Directory Sync link on the "Users" page.

  2. Click the OpenLDAP tab heading, and then click the Add New OpenLDAP Sync button.

  3. Enter the basic Directory Information required to create the OpenLDAP directory in Duo.

    Directory name

    Enter a descriptive name for the directory.


    The IP address or hostname of your directory server.


    The port on which to contact your directory server. The typical port for unsecured LDAP or STARTTLS is 389, and LDAPS is usually 636.

    Authentication type

    Select the type of authentication the Authentication Proxy will use to connect to your directory server. One of:

      Integrated - Performs SSPI authentication.
    • NTLMv1 - Performs Windows NTLMv1 authentication. If you select this option you'll need to enter the NTLM domain and NTLM workstation names on the new directory page in the Admin Panel, and also specify the username and password used to connect to your directory server when you configure your Duo Authentication Proxy server.
    • NTLMv2 - Performs Windows NTLMv2 authentication. If you select this option you'll need to enter the NTLM domain and NTLM workstation names on the new directory page in the Admin Panel, and also specify the username and password used to connect to your directory server when you configure your Duo Authentication Proxy server.
    • Plain - Performs basic authentication. This option provides the widest compatibility. You will specify the username and password used to connect to your directory when you configure your Duo Authentication Proxy server. We recommend using secure LDAPS or STARTTLS to protect sensitive credentials if you select this option.

    OpenLDAP Basic Directory Information

  4. Enter the Directory Sync settings for your OpenLDAP directory.

    Base DN

    The base DN should be a level in your directory structure above both the users and groups you plan to synchronize.

    Example: OU=CorpUsers,DC=domain,DC=local

    Enrollment email

    Select the Send enrollment email to synced users option if you want an enrollment link email sent automatically to imported users when the sync process completes. Only users who are imported from Active Directory with active status, a valid email address, and who do not already have any registered authentication devices in Duo receive an enrollment link via email.

    The enrollment link sent when the sync first imports a user is valid for 30 days. Duo sends an emailed enrollment reminder if the user hasn't yet completed enrollment after two days, and then a second reminder if the user remains unenrolled eight days after the first reminder.

    If the user does not complete the enrollment process after 30 days has elapsed, the original enrollment link expires and a new enrollment link is generated at the next sync and sent to the user. This entire 30 day cycle repeats until the user completes Duo enrollment.

    The contents of the enrollment email subject and body can be changed on the global Settings page. The enrollment email body should contain the placeholder text "<enrollment-link>", which will be replaced by the link to the enrollment page when the email is sent.

    If your organization uses e-mail filtering, be sure to whitelist the sender

    Import phones

    Enable this option if you want Directory Sync to create phones for imported users.

    When you check the Import phones for users in this directory option, two additional input fields appear: Phone 1 attribute and Phone 1 attribute. Enter the name of the OpenLDAP user attribute that contains telephone information (telephoneNumber in the example configuration below).

    If left disabled, phone information will not be imported or updated from OpenLDAP.

    International phone numbers stored in your source directory must be prefixed with + and the country code, e.g. +4401617150105 for a UK number.

    If you enable both the "Enrollment email" and "Import phones" options, enrollment links are only sent to users who do not have phone information populated in OpenLDAP.

    Import notes

    Enable this option if you want Directory Sync to import information from your directory into the Duo users' notes field.

    When you check the Import notes for users option, the additional input field Notes attribute appears. Enter the name of the OpenLDAP user attribute that contains the information you want to appear in the Duo Notes field for users (description in the example configuration below).

    If left disabled, notes will not be imported or updated from OpenLDAP.

    OpenLDAP Directory Sync Settings

  5. Configure which OpenLDAP attributes Duo imports in the Directory Attribute Customization section.


    The source attribute for the Duo username. The attribute selected should match the primary authentication login name your users submit to Duo. This attribute cannot be customized after the first directory synchronization occurs. The uid attribute commonly contains an OpenLDAP username.

    Username Alias 1 through Username Alias 4

    Optionally specify directory attributes to import as additional usernames for each Duo user. For example, if the Username source attribute is uid and Username Alias 1 is set to mail, then the resulting Duo user may log in with either username format while consuming a single Duo user license.

    Be sure to choose directory attributes that have unique values (email address, employee ID, etc.). Unlike the Username, the attributes used for username aliases may be changed after the first directory synchronization.

    Full Name

    The source attribute for the Duo user's full display name. This attribute may be one that you also specified as a username alias (like mail or cn), but is not used for authentication.


    The source attribute for a Duo user's email address, such as mail. If you choose to send enrollment emails to synced users, this is the address used.

    This attribute is not used for authentication. If your user need to authenticate to Duo using their email addresses, configure mail as a username alias attribute as well.

    OpenLDAP Custom Attribute Settings

  6. When finished entering these initial fields, click Add Directory to create the new directory in Duo and expose additional configuration options.

Duo Beyond and Duo Access Plan Users: Global Policy settings affect access to the enrollment portal. Do not apply any global restrictions that could prevent user enrollment if you chose to send enrollment emails. For example, if you configure the User Location policy setting to deny access to a country, then the policy will also block any of your users who attempt to enroll in Duo from that country via a bulk enrollment link. The New User Policy setting for the enrollment portal is always "Require Enrollment".

Configure Additional Options

Add Additional Directory Servers

Once you save the directory you can add additional LDAP servers. Duo selects any one of the servers in the list as the target when performing a sync. In the Directory Information section, click Add backup server and enter your additional OpenLDAP server IP or hostname and port information.

OpenLDAP Backup Server

If you decommission any of your directory servers be sure to return to Duo and remove it from the list.

Secure LDAP Communications

Additional configuration options for securing connectivity between the Duo Authentication Proxy and your directory server appear in the Directory Sync Settings section after initial creation.

You may adjust the Transport type setting (CLEAR, LDAPS, or STARTTLS). This determines how the connection between the Duo Authentication Proxy software and the OpenLDAP directory server is encrypted, if at all. Connectivity between the Duo Authentication Proxy software and the Duo Security cloud services are always HTTPS secured with SSL and is not affected by this setting.

If you selected Plain authentication for this directory, please avoid CLEAR and switch to a secure transport type to protect your directory server lookup credentials.

The SSL verify hostname option requires that the OpenLDAP directory's SSL certificate subject "common name" or "issued to" and the server hostname you entered when setting up your directory need to match. For instance, if the OpenLDAP SSL certificate is issued to ldap.acme.corp and you entered the IP of that server when setting up the directory in Duo instead of the hostname ldap.acme.corp. If you then enable this option, the connection between your Authentication Proxy and your directory server fails with the message "The directory server credentials were rejected".

In order to secure LDAP connections to your OpenLDAP directory server using LDAPS or STARTTLS protocols, you'll need the PEM formatted certificate from the certificate authority (CA) that issued your directory server's SSL certificate.

Open the issuing CA certificate in a text editor. Copy the file contents (including the BEGIN and END wrapper) and paste into the SSL CA certs field on your OpenLDAP directory configuration page. You may need to export all the certs (such as root CA and intermediate CA) in the certification path and paste them all into this page.

OpenLDAP Directory Secure Communications

When you have completed configuring backup servers or additional security settings that are relevant for your environment, click the Save Directory button at the bottom of the page.

Duo Authentication Proxy

The next step after saving the directory settings is to install the Duo Authentication Proxy software on a machine that can connect to both Duo's cloud service and to your LDAP server. Before proceeding, you should locate (or set up) a system in your environment on which you will install the Duo Authentication Proxy. This host needs LDAP connectivity to your directory server (ports 389/636 or whichever ports accept OpenLDAP binds), as well as HTTPS/443 connectivity to Duo.

If you are already running an Authentication Proxy server in your environment, you can also use that host for directory synchronization.

The minimum Authentication Proxy version for OpenLDAP synchronization is 2.6.0.

Connectivity Requirements

This application communicates with Duo's service on TCP port 443. Firewall configurations that restrict outbound access to Duo's service with rules using destination IP addresses or IP address ranges aren't recommended, since these may change over time to maintain our service's high availability. If your organization requires IP-based rules, please review this Duo KB article.

Install the Duo Authentication Proxy

Locate (or set up) a system on which you will install the Duo Authentication Proxy. The proxy supports Windows and Linux systems (in particular, we recommend Windows Server 2012 R2 or later, Red Hat Enterprise Linux 6 or later, CentOS 6 or later, or Debian 6 or later).

The Duo Authentication Proxy can be installed on a physical or virtual host. We recommend a system with at least 1 CPU, 200 MB disk space, and 4 GB RAM (although 1 GB RAM is usually sufficient).

  1. Download the most recent Authentication Proxy for Windows from Note that the actual filename will reflect the version e.g. duoauthproxy-3.2.1.exe. View checksums for Duo downloads here.
  2. Launch the Authentication Proxy installer on the target Windows server as a user with administrator rights and follow the on-screen prompts.
  1. Ensure that Perl, Python 2.6 or 2.7 (including development headers and libraries), and a compiler toolchain are installed. On most recent RPM-based distributions — like Fedora, RedHat Enterprise, and CentOS — you can install these by running (as root):

    $ yum install gcc make python-devel libffi-devel perl zlib-devel

    On Debian-derived systems, install these dependencies by running (as root):

    $ apt-get install build-essential python-dev libffi-dev perl zlib1g-dev
  2. Download the most recent Authentication Proxy for Unix from Depending on your download method, the actual filename may reflect the version e.g. duoauthproxy-3.2.1-src.tgz. View checksums for Duo downloads here.

  3. Extract the Authentication Proxy files and build it as follows:

    $ tar xzf duoauthproxy-latest-src.tgz
    $ cd duoauthproxy-version-src
    $ make
  4. Install the authentication proxy (as root):

    $ cd duoauthproxy-build
    $ ./install

    Follow the prompts to complete the installation. The installer creates a user to run the proxy service and a group to own the log directory and files. You can accept the default user and group names or enter your own.

If you ever need to uninstall the proxy, run /opt/duoauthproxy/uninstall.

Configure the Proxy

After the installation completes, you will need to configure the proxy.

The Duo Authentication Proxy configuration file is named authproxy.cfg, and is located in the conf subdirectory of the proxy installation. With default installation paths, the proxy configuration file will be located at /opt/duoauthproxy/conf/authproxy.cfg on Linux, C:\Program Files (x86)\Duo Security Authentication Proxy\conf\authproxy.cfg for Windows (64-bit) and C:\Program Files\Duo Security Authentication Proxy\conf\authproxy.cfg for Windows (32-bit).

Download the Authentication Proxy authproxy.cfg file for your OpenLDAP directory sync by clicking the Duo Authentication Proxy Config link in step 2 of the Duo Authentication Proxy section of the directory properties page.

The configuration file is formatted as a simple INI file. Section headings appear as:


Individual properties beneath a section appear as:


A first time Authentication Proxy install may include an existing authproxy.cfg with some example content. For the purposes of these instructions, however, you should delete the existing sample content and paste in the information from the authproxy.cfg file download from the directory properties page.

The authproxy.cfg file for OpenLDAP Directory Sync contains a [cloud] section with the following properties:

Integrated authentication

Field Value
ikey your integration key
skey your secret key
api_host your API hostname (i.e.,

NTLMv1, NTLMv2, or Plain authentication

Field Value
ikey Your integration key.
skey Your secret key.
api_host Your API hostname (i.e.,
service_account_username The account used to bind to OpenLDAP. This account needs read-only access to your directory. You may need to specify this as the full LDAP DN of your service account e.g. uid=duosync,ou=people,o=acme.
service_account_password The directory password for the service_account_username user.

Add the information from your downloaded authproxy.cfg to your Authentication Proxy server configuration file. Make sure to save your configuration file when done.

To configure an existing Authentication Proxy server for directory sync, simply append the [cloud] section of the config file downloaded from the Duo Admin Panel directory properties page to the current authproxy.cfg file located in the Duo Security Authentication Proxy conf folder. Save the configuration file then restart the Duo Authentication Proxy service. Note that there can only be one [cloud] section in the authproxy.cfg file.

Here's a sample authproxy.cfg file for Plain authentication:


Encrypting Passwords

When running the Authentication Proxy on Windows, you may encrypt the directory user password stored in the [cloud] section if you do not want to store them as plain text. Use the authproxy_passwd.exe program, which can be found in the bin directory of your Authentication Proxy installation.

c:\>"C:\Program Files (x86)\Duo Security Authentication Proxy\bin\authproxy_passwd.exe"
Re-enter password:

Copy and paste the output into your configuration file as and remove any line breaks. You may find it easier to redirect the command output to a file and then open the file in Notepad.


The encrypted password is specific to the server where it was generated, and will not work if copied to a different machine. If you have multiple Authentication Proxy servers with the same service account specified, be sure to run authproxy_passwd.exe separately on each one.

Here's a sample authproxy.cfg file for Plain authentication with an encrypted password:


Start the Proxy

To start the Duo Authentication Proxy service on Windows, launch an Administrator command prompt and run:

net start duoauthproxy

Or, open the "Services" console (services.msc), locate the "Duo Security Authentication Proxy Service" in the list of services and click on it to select, and then click the start button.

To start the Duo Authentication Proxy on Linux, run:

/opt/duoauthproxy/bin/authproxyctl start


View video guides for proxy deployment at the Authentication Proxy Overview or see the Authentication Proxy Reference Guide for additional configuration options.

Choose Groups

After setting up the Duo Authentication Proxy software, the next step in OpenLDAP synchronization is to select which groups should be synchronized from the AD server to Duo.

Once the Duo Authentication Proxy service is running, click the refresh this page link in section 3 Choose Groups on the directory properties page to initiate the connection between the Duo service and the Authentication Proxy server.

If the directory properties page indicates the new directory is connected to Duo Authentication Proxy and you click in the Groups box, you should see a list of OpenLDAP groups that are available. If you don't see any of your groups listed, review the previous setup steps (especially the Base DN) and correct your configuration.

Once you see a list of groups, click to select the desired group or groups to sync, then click Save Groups. If you start typing a group name in the box the list of available groups will match the filter. You can select up to 400 groups to sync from the source directory. Members of the groups you choose here will be synced into Duo.

Nested groups are supported; Duo sync imports users from groups nested within your sync group, but creates only the top level group in Duo (the group explicitly selected for directory sync), with all nested group members as direct members of that Duo group.

Choose Directory Groups

If the base DN you specified when setting up the directory has more than 10,000 groups below it, you'll see a message stating this is the case, along with an Advanced Search button.

Advanced Search

Click Advanced Search to open the search dialog. Enter all or part of the distinguished name (DN) for a group you want to sync with Duo and then click Search. Click on your desired sync groups in the search results to select then, then click Select group(s). This adds the selected groups to your directory configuration and closes advanced search.

Choose Directory Groups by Distinguished Name

You can repeat the search step until all your required groups have been added to the directory sync configuration. Click Save Groups when done.

Perform the Sync

Once you have configured the directory settings, installed the Duo Authentication Proxy software, and chosen the groups to synchronize, you are ready to perform the initial synchronization with your directory.

The Sync Now button appears in the upper right hand corner of the Duo Admin Panel after all three directory configuration steps have been completed successfully.

If you wish, you can click Sync Now immediately to begin importing users from your directory into Duo. When the directory sync completes, Duo reports its success to you. Otherwise, Directory Sync runs automatically once a day (at a set time chosen at random). You can always return to the Duo Admin Panel to initiate a manual sync.

Individual User Sync from the Duo Admin Panel

Role required: Owner, Administrator, User Manager, or Help Desk.

When you just need to import information for a few users from OpenLDAP you can use the individual user sync feature instead of syncing the entire directory. For example, you may have a new employee account in OpenLDAP who needs a corresponding Duo account. Syncing these individual user accounts updates Duo immediately.

Type a single user name in the box at the top of the directory's properties page and click the Sync This User button. The user must be a member of an AD group specified in the "Choose Groups" section of your directory's configuration. If you try to sync an individual user who is not a member of a selected group then no update occurs (and an existing user just removed from a synced group in the source directory gets disabled in Duo but won't be put into the Trash with "Pending Deletion" status).

You can also perform an individual sync on an existing Duo user by visiting that user's properties page in the Duo Admin Panel and clicking the Sync this user link at the top-right.

When initiated, the individual user sync verifies that the user is a member of a group currently synced with Duo and then imports information for that user into Duo. If the user doesn't already exist in Duo, the sync creates them using the information imported from the source directory. If you enabled the option to send enrollment emails when adding the directory and the new user has the email address attribute populated, then a new user created by the individual user sync receives an emailed enrollment link.

Individual user sync updates an existing user with information from the source directory. The sync can change attribute values (except the username), modify group memberships, or disable the user in Duo if they are disabled in the source directory.

If you run an individual user sync against a user that is no longer a member of any group synced into Duo, then the sync marks the user for deletion.

Individual User Sync using Admin API

Use the AdminAPI directory key from the "Directory Settings" section of the page to perform a sync operation on an individual user using Duo's Admin API.

User Enrollment and Activation

After adding new users to Duo through OpenLDAP synchronization, your next step is to have them activate their Duo access (if you chose not to send enrollment emails to synced users when creating your directory in Duo). Because a phone created by directory sync defaults to the "Generic Smartphone" platform, on the Users page you'll see a notification bar indicating that users have not yet activated the Duo Mobile smartphone app. This bar provides a link to click to send these users activation links.

For more information on user activation, see Activating Duo Mobile After Enrollment.

If you did choose to send enrollment emails to synced users automatically, the Pending Enrollments table shows which users created by directory sync (or bulk enrollment) have not yet completed enrolling their 2FA devices in Duo, along with the user's email address and the expiration date for the enrollment link previously sent. If you need to send the user another copy of the enrollment link email, click the Resend button. Resending the email does not change the current enrollment link's expiration date.

Managing Synced Users

Updating Synced User Information

User attributes synced from an external directory cannot be edited in Duo via the Admin Panel, Admin API, or CSV import. This includes Duo username and username aliases, full name, email address, phone numbers (if you chose to import phones), notes, and group memberships. Changes to these user attributes should be made in the external directory and then synced over to Duo.

Bypass Status for Synced Users

Users synced from an external directory may have bypass status assigned individually or at the group level. See the Using Groups and User Status Administration documentation for more information.

Disabled Status for Synced Users

Admins can't disable individual Duo users managed by directory sync from the Duo Admin Panel, Admin API, or CSV import. Directory sync disables users removed from the selected synced groups and puts those users in the Trash "Pending Deletion" when a full sync runs. A single-user sync disabled users removed from the sync groups (and the next full sync moves the users into the Trash).

You can restore the disabled Duo account to active status by adding the account back to the synced group in the source directory and running a sync.

You may disable a group of synced users by changing the status of that group to Disabled. This prevents any user who is a member of that group from logging in with Duo, regardless of that individual user's status. See the Using Groups and Group Status Administration documentation for more information.

Deleting Synced Users

You may not delete a synced user from Duo as long as directory sync is actively managing that user. If a synced directory user is removed from all external directory groups that sync to Duo (or if the user account is deleted from the source directory), the user's status changes to "Pending Deletion" at the next full directory sync or individual sync for that user, and the user can no longer authenticate to Duo. The user's properties are read-only and you are no longer billed for that user.

Locate users pending deletion in the Trash view, accessed by clicking the Trash count shown at the top of the Users page.

Users in Trash Pending Deletion

If the user marked for deletion is not reconnected to an external directory account via the sync within seven days the user is automatically deleted from Duo. The user's properties show the target date for deletion. A Duo admin can manually delete a synced user from the Trash via the Permanently Delete link at any time during those seven days.

User in Trash

Frequently Asked Questions

Be sure to review frequently asked questions and answers before using Duo's OpenLDAP synchronization.


Need some help? Take a look at the OpenLDAP Sync Frequently Asked Questions (FAQ) page or try searching our OpenLDAP Sync Knowledge Base articles or Community discussions. For further assistance, contact Support.