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Duo can be integrated with almost any device or system that supports using LDAP for authentication. In this type of configuration, users will receive an automatic push or phone callback during login. Users who need to use a passcode have the option to append it to their existing password when logging in.

Supported Devices

Duo can be integrated with most devices and systems that support LDAP for authentication.

First Steps

To integrate Duo with your LDAP device, you will need to install a local proxy service on a machine within your network. Before proceeding, you should 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).

Then you'll need to:

  1. Sign up for a Duo account.
  2. Log in to the Duo Admin Panel and navigate to Applications.
  3. Click Protect an Application and locate LDAP Proxy in the applications list. Click Protect this Application to get your integration key, secret key, and API hostname. See Getting Started for help.
Connectivity Requirements

This integration communicates with Duo's service on TCP port 443. Also, we do not recommend locking down your firewall to individual IP addresses, since these may change over time to maintain our service's high availability.

Install the Duo Authentication Proxy

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 https://dl.duosecurity.com/duoauthproxy-latest.exe. Note that the actual filename will reflect the version e.g. duoauthproxy-2.5.4.exe.
  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 OpenSSL, 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 openssl-devel python-devel libffi-devel

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

    $ apt-get install build-essential libssl-dev python-dev libffi-dev

    To ensure that your Python version will work with the Authentication Proxy, run:

    $ python --version

    If the output does not say "Python 2.6.x" or "Python 2.7.x", first take note that many distributions can support multiple versions of python simultaneously. If your python installation does not appear to be a supported version, try replacing "python" in the above command with "python2.6" or "python2.7". If neither of these work, then you will need to install a different version of Python. You may need to search additional repositories for your distribution (e.g. for Centos or Red Hat Enterprise Linux, Extra Packages for Enterprise Linux), or build Python from source.

  2. Download the most recent Authentication Proxy for Unix from https://dl.duosecurity.com/duoauthproxy-latest-src.tgz. Depending on your download method, the actual filename may reflect the version e.g. duoauthproxy-2.5.4-src.tgz.

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

    $ tar xzf duoauthproxy-latest-src.tgz
    $ cd duoauthproxy-version-src
    $ export PYTHON=python_command
    $ make
    Where python_command is the command to run a Python 2.6 or Python 2.7 interpreter (e.g. "python", "python2.6", "python2.7").
  4. Install the authentication proxy (as root):

    $ cd duoauthproxy-build
    $ ./install

    Follow the prompts to complete the installation.

    The proxy listensfor connections on ports 389 and 636 by default. Privileged ports below 1024 are reserved for the root user. Therefore, the proxy will not start if you choose any user account other than "root" to run under during installation.

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:

Platform Default Configuration Path
Windows (64-bit) C:\Program Files (x86)\Duo Security Authentication Proxy\conf\authproxy.cfg
Windows (32-bit) C:\Program Files\Duo Security Authentication Proxy\conf\authproxy.cfg
Linux /opt/duoauthproxy/conf/authproxy.cfg

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

[section]

Individual properties beneath a section appear as:

name=value

The Authentication Proxy may include an existing authproxy.cfg with some example content. For the purposes of these instructions, however, you should delete the existing content and start with a blank text file. We recommend using WordPad or another text editor instead of Notepad when editing the config file on Windows.

Configure the Proxy for Your Primary Authenticator

In this step, you'll set up the Proxy's primary authenticator — the system which will validate users' existing passwords. In most cases, this means configuring the Proxy to communicate with Active Directory.

Active Directory

To use Active Directory as your primary authenticator, add an [ad_client] section to the top of your config file. Add the following properties to the section:

Required

host The hostname or IP address of your domain controller.
service_account_username The username of a domain member account that has permission to bind to your Active Directory and perform searches. We recommend creating a service account that has read-only access.
service_account_password The password corresponding to service_account_username. If you're on Windows and would like to encrypt this password, see Encrypting Passwords in the full Authentication Proxy documentation.
search_dn

The LDAP distinguished name (DN) of an Active Directory container or organizational unit (OU) containing all of the users you wish to permit to log in. For example:

search_dn=DC=example,DC=com

Optional

host_2 The hostname or IP address of a secondary/fallback domain controller. You can add additional domain controllers as host_3, host_4, etc.
security_group_dn

To further restrict access, specify the LDAP distinguished name (DN) of a security group that contains the users who should be able to log in. Other users will not pass primary authentication. For example:

security_group_dn=CN=DuoVPNUsers,OU=Groups,DC=example,DC=com

For example:

[ad_client]
host=1.2.3.4
host_2=1.2.3.5
service_account_username=duoservice
service_account_password=password1
search_dn=DC=example,DC=com
security_group_dn=CN=DuoVPNUsers,OU=Groups,DC=example,DC=com

For advanced Active Directory configuration, see the full Authentication Proxy documentation.

Configure the Proxy As a LDAP Server

Next, you need to set up the Authentication Proxy to handle LDAP authentication requests. To do so, create a ldap_server_auto section with the following properties:

Required

ikey Your integration key.
skey Your secret key.
api_host Your API hostname (i.e. api-XXXXXXXX.duosecurity.com)
client

The mechanism that the Authentication Proxy should use to perform primary authentication. This should correspond with a "client" section elsewhere in the config file.

"ad_client" Use Active Directory for primary authentication. Make sure you have an [ad_client] section configured.

This parameter is optional if you only have one "client" section. If you have multiple, each "server" section should specify which "client" to use.

Optional

failmode Either "safe" or "secure":
"safe" In the event that Duo's service cannot be contacted, users' authentication attempts will be permitted if primary authentication succeeds. (Default)
"secure" In the event that Duo's service cannot be contacted, all users' authentication attempts will be rejected.
ssl_key_path

Path to PEM-formatted SSL/TLS private key. Both ssl_key_path and ssl_cert_path must be specified to listen for STARTTLS or LDAPS requests.

ssl_cert_path

Path to PEM-formatted SSL/TLS server certificate. Both ssl_key_path and ssl_cert_path must be specified to listen for STARTTLS or LDAPS requests.

exempt_primary_bind

If set to "true" (the default) then multi-factor authentication will not be performed for the first successful LDAP authentication in each connection. Use this if the device using the Authentication Proxy first connects as a service user and then authenticates the user who is logging in.

exempt_ou_1

Specify either the DN of a single user or an OU. Multi-factor authentication will not be required for these users. Set this option if the device using the Authentication Proxy first connects as a service user, disconnects, and then authenticates the user who is logging in with a separate LDAP connection. The exemptions should cover those service user(s).

A completed config file, using Active Directory as the primary authenticator, should look something like:

[ad_client]
host=1.2.3.4  
service_account_username=duoservice  
service_account_password=password1  
search_dn=cn=Users,dc=example,dc=com  

[ldap_server_auto]
client=ad_client
ikey=DIXXXXXXXXXXXXXXXXXX
skey=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
api_host=api-XXXXXXXX.duosecurity.com
failmode=safe  
ssl_key_path=ldap_server.key  
ssl_cert_path=ldap_server.pem

Make sure to save your configuration file when done.

Note

See the AuthProxy Reference Guide for additional AuthProxy LDAP configuration options.

Start the Proxy

Open an Administrator command prompt and run:

net start DuoAuthProxy

Alternatvely, open the Windows Services console (services.msc), locate "Duo Security Authentication Proxy Service" in the list of services, and click the Start Service button.

If the service starts successfully, Authentication Proxy service output is written to the authproxy.log file, which can be found in the log subdirectory.

If you see an error saying that the "service could not be started", open the Application Event Viewer and look for an Error from the source "DuoAuthProxy". The traceback may include a "ConfigError" that can help you find the source of the issue.

Stop and restart the Authentication Proxy service by either clicking the Restart Service button in the Windows Services console or issuing these commands from an Administrator command prompt:

net stop DuoAuthProxy & net start DuoAuthProxy

Open a root shell and run:

# /opt/duoauthproxy/bin/authproxyctl start

To ensure the proxy started successfully, run:

# /opt/duoauthproxy/bin/authproxyctl status

Authentication Proxy service output is written to the authproxy.log file, which can be found in the log subdirectory.

To stop and restart the Authentication Proxy, open a root shell and run:

# /opt/duoauthproxy/bin/authproxyctl restart

If you modify your authproxy.cfg configuration after initial setup, you'll need to stop and restart the Duo Authentication Proxy service or process for your change to take effect.

Configure Your LDAP Client(s)

Once the proxy is up and running, you need to configure your LDAP clients to use it for authentication.

In your clients' settings, set the LDAP server to the IP address or host name of your Duo authentication proxy. Set the LDAP server port to 636 to secure the connection with SSL.

The service user name and service password configured on the LDAP client(s) should be the same as it would be if you were configured to connect directly to the AD or LDAP server.

If your clients allow you to configure the LDAP timeout, set them to values such that the clients will not give up for at least 60 seconds. This is necessary if your users choose to use Duo's out-of-band factors (phone callback, push) to log in, as the authentication proxy will not be able to respond to a LDAP authentication request until the user responds to the authentication challenge. If your clients do not allow you to configure the LDAP timeout behavior, then your users may be unable to authenticate with Duo's out-of-band factors.

Test Your Setup

To test your setup, attempt to log in to your newly-configured system. When you enter your username and password, you will receive an automatic push or phone callback. Alternatively you can add a comma (",") to the end of your password, followed by a Duo passcode.

For example, given a username 'bob', with password 'password123' and a Duo passcode '123456', you would enter:

username: bob
password: password123,123456

In addition, you may also enter the name of an out-of-band factor in lieu of a passcode. You may choose from the following factor names:

push Perform Duo Push authentication
You can use Duo Push if you've installed Duo Mobile and added your account to it
phone Perform phone callback authentication
sms Send a new batch of SMS passcodes
Your authentication attempt will be denied. You can then authenticate with one of the newly-delivered passcodes.

Returning to the previous example, if you wanted to use Duo Push (rather than a passcode) to authenticate, you would enter:

username: bob
password: password123,push

You can also specify a number after the factor name if you have more than one device enrolled. So you can enter phone2 or push2 if you have two phones enrolled.

Troubleshooting

Need some help? Take a look at our LDAP Knowledge Base articles or Community discussions. For further assistance, contact Support.

Network Diagram

  1. Primary authentication initiated to application or service
  2. Application or service send authentication request to Duo Security’s authentication proxy
  3. Primary authentication using Active Directory
  4. Duo authentication proxy connection established to Duo Security over TCP port 443
  5. Secondary authentication via Duo Security’s service
  6. Duo authentication proxy receives authentication response
  7. Application or service access granted

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