Another LDAP authentication

LDAP Authentication for Nginx, Kubernetes ingress controller (Nginx), HAProxy (haproxy-auth-request) or any webserver/reverse proxy with authorization based on the result of a subrequest.

Another LDAP Authentication is an implementation of the ldap-auth-daemon services described in the official blog from Nginx in the following article.

Another LDAP Authentication it's prepared to run inside a Docker container, also you can run the Python script without the Docker container.

Features

• Supports ldap and ldaps.
• Provide a cache for users and groups, you can set the cache expiration in minutes.
• Supports validation by groups, regex in groups are supported.
• Supports TLS via self-signed certificate.
• Supports configuration via headers or via environment variables.
• Supports HTTP response headers such as username and matched groups.
• Brute force protection.
• Log format in Plain-Text or JSON.

Diagram

Available configurations parameters

The parameters can be sent via environment variables or via HTTP headers, also you can combine them.

The parameter LDAP_SEARCH_FILTER support variable expansion with the username, you can do something like this (sAMAccountName={username}) and {username} is going to be replaced by the username typed in the login form.

The parameter LDAP_BIND_DN support variable expansion with the username, you can do something like this {username}@TESTMYLDAP.com or UID={username},OU=PEOPLE,DC=TESTMYLDAP,DC=COM and {username} is going to be replaced by the username typed in the login form.

All values type are string.

Environment variables

Key	Default	Values	Description	Example
LDAP_ENDPOINT			LDAP URL with the protocol and the port number.	ldaps://testmyldap.com:636
LDAP_MANAGER_DN_USERNAME			Username to bind and search in the LDAP tree.	CN=john,OU=Administrators,DC=TESTMYLDAP,DC=COM
LDAP_MANAGER_PASSWORD			Password for the bind user.
LDAP_SEARCH_BASE				DC=TESTMYLDAP,DC=COM
LDAP_SEARCH_FILTER			Filter for search, for Microsoft Active Directory usually you can use sAMAccountName.	(sAMAccountName={username})
LDAP_BIND_DN	{username}		Depends on your LDAP server the binding structure can change. This field support variable expansion for the username.	{username}@TESTMYLDAP.com or UID={username},OU=PEOPLE,DC=TESTMYLDAP,DC=COM
LDAP_ALLOWED_USERS (Optional)			Support a list separated by commas.	'diego,john,s-master'
LDAP_ALLOWED_GROUPS (Optional)			Supports regular expressions, and support a list separated by commas.	'DevOps production environment', 'Developers .* environment'
LDAP_ALLOWED_GROUPS_CONDITIONAL	and	and, or	Conditional to match all the groups in the list or just one of them.	or
LDAP_ALLOWED_GROUPS_CASE_SENSITIVE	enabled	enabled, disabled	Enabled or disabled case sensitive groups matches.	disabled
LDAP_ALLOWED_GROUPS_USERS_CONDITIONAL	or	and, or	Conditional to match user and at least one group in the list, or one of the two	and
CACHE_EXPIRATION	5		Cache expiration time in minutes.	10
LOG_LEVEL	INFO	INFO, WARNING, ERROR	Logger level.	DEBUG
LOG_FORMAT	TEXT	TEXT, JSON	Output format of the logger.	JSON
LDAP_HTTPS_SUPPORT	disabled	enabled, disabled	Enabled or disabled HTTPS support with self signed certificate.
BRUTE_FORCE_PROTECTION	disabled	enabled, disabled	Enabled or disabled Brute force protection per IP.
BRUTE_FORCE_EXPIRATION	10		Brute force expiration time in seconds per IP.
BRUTE_FORCE_FAILURES	3		Number of failures before the IP is blocked.

HTTP request headers

The variables send via HTTP headers take precedence over environment variables.

• Ldap-Endpoint
• Ldap-Manager-Dn-Username
• Ldap-Manager-Password
• Ldap-Bind-DN
• Ldap-Search-Base
• Ldap-Search-Filter
• Ldap-Allowed-Users
• Ldap-Allowed-Groups
• Ldap-Allowed-Groups-Case-Sensitive
• Ldap-Allowed-Groups-Conditional

HTTP response headers

• x-username Contains the authenticated username
• x-groups Contains the username matches groups

Installation and configuration

The easy way to use Another LDAP Authentication is running as a Docker container and set the parameters via environment variables.

Step 1 - Run as a Docker container

Change the environment variables with your setup.

docker run -d \
    -e LDAP_ENDPOINT='ldaps://testmyldap.com:636' \
    -e LDAP_MANAGER_DN_USERNAME='CN=john-service-user,OU=Administrators,DC=TESTMYLDAP,DC=COM' \
    -e LDAP_MANAGER_PASSWORD='MasterpasswordNoHack123' \
    -e LDAP_BIND_DN='{username}@TESTMYLDAP.COM' \
    -e LDAP_SEARCH_BASE='DC=TESTMYLDAP,DC=COM' \
    -e LDAP_SEARCH_FILTER='(sAMAccountName={username})' \
    -e LOG_FORMAT='JSON' \
    -p 9000:9000 \
    --name another_ldap_auth \
    dignajar/another-ldap-auth:latest

Another LDAP Authentication now is running on http://localhost:9000.

Test it via curl:

curl -vvv http://localhost:9000 -u diego:mypassword

Output from ALDAP:

{"date": "2021-05-21 10:06:52", "level": "INFO", "objectName": "Cache", "ip": "192.168.0.10", "referrer": null, "message": "User not found in the cache.", "username": "diego"}
{"date": "2021-05-21 10:06:52", "level": "INFO", "objectName": "Aldap", "ip": "192.168.0.10", "referrer": null, "message": "Authenticating user.", "username": "diego", "finalUsername": "diego"}
{"date": "2021-05-21 10:06:53", "level": "INFO", "objectName": "Aldap", "ip": "192.168.0.10", "referrer": null, "message": "Authentication successful.", "username": "diego", "elapsedTime": "0.22335"}
{"date": "2021-05-21 10:06:53", "level": "INFO", "objectName": "Cache", "ip": "192.168.0.10", "referrer": null, "message": "Adding user to the cache.", "username": "diego"}
192.168.0.10 - - [21/May/2021 10:06:53] "GET / HTTP/1.1" 200 -

Remember you can enable self-signed certificate from Flask via the environment variable LDAP_HTTPS_SUPPORT=="enabled".

Step 2 - Nginx configuration

Nginx use the module ngx_http_auth_request_module to do the subrequest.

The following example shows how to configure Nginx that is running in the same machine as Another LDAP Authentication. The backend /private/ includes the authentication request to /another_ldap_auth.

location /private/ {
    auth_request /another_ldap_auth;
    # ...
    # Here you private site
}

location = /another_ldap_auth {
    internal;
    proxy_pass_request_body off;
    proxy_set_header Content-Length "";
    proxy_pass http://localhost:9000;
}

Now you can access to your website wich is going to be something like this http://myserver.com/private/ and Nginx will request you to write the username and password.

Deploy to Kubernetes with Nginx ingress controller

Get the K8s manifests from the folder /kubernetes.

The manifests for K8s helps to deploy Another LDAP Authentication in the namespace ingress-nginx and expose the service in the cluster at the following address https://another-ldap-auth.ingress-nginx.

Please change the environment variables from the manifest and the secret for the bind username.

After you have running Another LDAP Authentication in your Kubernetes, you can modify the ingress manifest from the application you want to protect.

You can remove the comment # and send headers as variables such as Matching groups.

---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: demo-webserver
  namespace: demo
  annotations:
    nginx.ingress.kubernetes.io/auth-url: https://another-ldap-auth.ingress-nginx

    # nginx.ingress.kubernetes.io/auth-snippet: |
    #   proxy_set_header Ldap-Allowed-Groups "<SOME GROUP>";
    #   proxy_set_header Ldap-Allowed-Groups-Conditional "or";
spec:
  rules:
  - host: demo.local
    http:
      paths:
      - path: /
        backend:
          serviceName: demo-webserver
          servicePort: 80

Brute Force protection

Brute force protection is blocking user IP, please read this article to know the limitations about blocking IPs

• https://owasp.org/www-community/controls/Blocking_Brute_Force_Attacks

Known limitations

• Parameters via headers need to be escaped, for example, you can not send parameters such as $1 or $test because Nginx is applying variable expansion.

Breaking changes from v1.x to v2.x

• LDAP_REQUIRED_GROUPS renamed to LDAP_ALLOWED_USERS
• LDAP_REQUIRED_GROUPS_CONDITIONAL renamed to LDAP_ALLOWED_GROUPS_CONDITIONAL
• LDAP_REQUIRED_GROUPS_CASE_SENSITIVE renamed to LDAP_ALLOWED_GROUPS_CASE_SENSITIVE
• LDAP_SERVER_DOMAIN removed and replace by LDAP_BIND_DN