General LDAP Setup

GitLab integrates with LDAP to support user authentication.

This integration works with most LDAP-compliant directory servers, including:

  • Microsoft Active Directory
  • Apple Open Directory
  • Open LDAP
  • 389 Server

GitLab Enterprise Editions (EE) include enhanced integration, including group membership syncing as well as multiple LDAP servers support.

Note: Microsoft Active Directory Trusts are not supported.

Overview

LDAP stands for Lightweight Directory Access Protocol, which is a standard application protocol for accessing and maintaining distributed directory information services over an Internet Protocol (IP) network.

Security

GitLab assumes that LDAP users:

  • Are not able to change their LDAP mail, email, or userPrincipalName attributes. An LDAP user who is allowed to change their email on the LDAP server can potentially take over any account on your GitLab server.
  • Have unique email addresses, otherwise it is possible for LDAP users with the same email address to share the same GitLab account.

We recommend against using LDAP integration if your LDAP users are allowed to change their ‘mail’, ‘email’ or ‘userPrincipalName’ attribute on the LDAP server or share email addresses.

User deletion

If a user is deleted from the LDAP server, they will be blocked in GitLab as well. Users will be immediately blocked from logging in. However, there is an LDAP check cache time of one hour (see note) which means users that are already logged in or are using Git over SSH will still be able to access GitLab for up to one hour. Manually block the user in the GitLab Admin Area to immediately block all access.

Note: GitLab Enterprise Edition Starter supports a configurable sync time.

Git password authentication

LDAP-enabled users can always authenticate with Git using their GitLab username or email and LDAP password, even if password authentication for Git is disabled in the application settings.

Enabling LDAP sign-in for existing GitLab users

When a user signs in to GitLab with LDAP for the first time, and their LDAP email address is the primary email address of an existing GitLab user, then the LDAP DN will be associated with the existing user. If the LDAP email attribute is not found in GitLab’s database, a new user is created.

In other words, if an existing GitLab user wants to enable LDAP sign-in for themselves, they should check that their GitLab email address matches their LDAP email address, and then sign into GitLab via their LDAP credentials.

Google Secure LDAP

Introduced in GitLab 11.9.

Google Cloud Identity provides a Secure LDAP service that can be configured with GitLab for authentication and group sync. See Google Secure LDAP for detailed configuration instructions.

Configuration

To enable LDAP integration you need to add your LDAP server settings in /etc/gitlab/gitlab.rb or /home/git/gitlab/config/gitlab.yml for Omnibus GitLab and installations from source respectively.

There is a Rake task to check LDAP configuration. After configuring LDAP using the documentation below, see LDAP check Rake task for information on the LDAP check Rake task.

Note: The encryption value simple_tls corresponds to ‘Simple TLS’ in the LDAP library. start_tls corresponds to StartTLS, not to be confused with regular TLS. Normally, if you specify simple_tls it will be on port 636, while start_tls (StartTLS) would be on port 389. plain also operates on port 389. Removed values: tls was replaced with start_tls and ssl was replaced with simple_tls.
Note: LDAP users must have an email address set, regardless of whether it is used to log in.

Example Configurations

Omnibus Configuration

gitlab_rails['ldap_enabled'] = true
gitlab_rails['prevent_ldap_sign_in'] = false
gitlab_rails['ldap_servers'] = {
'main' => {
  'label' => 'LDAP',
  'host' =>  'ldap.mydomain.com',
  'port' => 389,
  'uid' => 'sAMAccountName',
  'encryption' => 'simple_tls',
  'verify_certificates' => true,
  'bind_dn' => '_the_full_dn_of_the_user_you_will_bind_with',
  'password' => '_the_password_of_the_bind_user',
  'encryption' => 'plain',
  'verify_certificates' => true,
  'tls_options' => {
    'ca_file' => '',
    'ssl_version' => '',
    'ciphers' => '',
    'cert' => '',
    'key' => ''
  },
  'timeout' => 10,
  'active_directory' => true,
  'allow_username_or_email_login' => false,
  'block_auto_created_users' => false,
  'base' => 'dc=example,dc=com',
  'user_filter' => '',
  'attributes' => {
    'username' => ['uid', 'userid', 'sAMAccountName'],
    'email' => ['mail', 'email', 'userPrincipalName'],
    'name' => 'cn',
    'first_name' => 'givenName',
    'last_name' => 'sn'
  },
  'lowercase_usernames' => false,

  # EE Only
  'group_base' => '',
  'admin_group' => '',
  'external_groups' => [],
  'sync_ssh_keys' => false
  }
}

Source Configuration

production:
  # snip...
  ldap:
    enabled: false
    prevent_ldap_sign_in: false
    servers:
      main:
        label: 'LDAP'
        ...

Basic Configuration Settings

Setting Description Required Examples
label A human-friendly name for your LDAP server. It will be displayed on your login page. yes 'Paris' or 'Acme, Ltd.'
host IP address or domain name of your LDAP server. yes 'ldap.mydomain.com'
port The port to connect with on your LDAP server. Always an integer, not a string. yes 389 or 636 (for SSL)
uid LDAP attribute for username. Should be the attribute, not the value that maps to the uid. yes 'sAMAccountName', 'uid', 'userPrincipalName'
bind_dn The full DN of the user you will bind with. no 'america\momo' or 'CN=Gitlab,OU=Users,DC=domain,DC=com'
password The password of the bind user. no 'your_great_password'
encryption Encryption method. The method key is deprecated in favor of encryption. yes 'start_tls' or 'simple_tls' or 'plain'
verify_certificates Enables SSL certificate verification if encryption method is start_tls or simple_tls. Defaults to true. no boolean
timeout Set a timeout, in seconds, for LDAP queries. This helps avoid blocking a request if the LDAP server becomes unresponsive. A value of 0 means there is no timeout. no 10 or 30
active_directory This setting specifies if LDAP server is Active Directory LDAP server. For non-AD servers it skips the AD specific queries. If your LDAP server is not AD, set this to false. no boolean
allow_username_or_email_login If enabled, GitLab will ignore everything after the first @ in the LDAP username submitted by the user on login. If you are using uid: 'userPrincipalName' on ActiveDirectory you need to disable this setting, because the userPrincipalName contains an @. no boolean
block_auto_created_users To maintain tight control over the number of active users on your GitLab installation, enable this setting to keep new users blocked until they have been cleared by the admin (default: false). no boolean
base Base where we can search for users. yes 'ou=people,dc=gitlab,dc=example' or 'DC=mydomain,DC=com'
user_filter Filter LDAP users. Format: RFC 4515 Note: GitLab does not support omniauth-ldap’s custom filter syntax. no '(employeeType=developer)' or '(&(objectclass=user)(|(samaccountname=momo)(samaccountname=toto)))'
lowercase_usernames If lowercase_usernames is enabled, GitLab will lower case the username. no boolean

SSL Configuration Settings

Setting Description Required Examples
ca_file Specifies the path to a file containing a PEM-format CA certificate, e.g. if you need to use an internal CA. no '/etc/ca.pem'
ssl_version Specifies the SSL version for OpenSSL to use, if the OpenSSL default is not appropriate. no 'TLSv1_1'
ciphers Specific SSL ciphers to use in communication with LDAP servers. no 'ALL:!EXPORT:!LOW:!aNULL:!eNULL:!SSLv2'
cert Client certificate no '-----BEGIN CERTIFICATE----- <REDACTED> -----END CERTIFICATE -----'
key Client private key no '-----BEGIN PRIVATE KEY----- <REDACTED> -----END PRIVATE KEY -----'

Attribute Configuration Settings

LDAP attributes that GitLab will use to create an account for the LDAP user. The specified attribute can either be the attribute name as a string (e.g. 'mail'), or an array of attribute names to try in order (e.g. ['mail', 'email']). Note that the user’s LDAP login will always be the attribute specified as uid above.

Setting Description Required Examples
username The username will be used in paths for the user’s own projects (like gitlab.example.com/username/project) and when mentioning them in issues, merge request and comments (like @username). If the attribute specified for username contains an email address, the GitLab username will be the part of the email address before the @. no ['uid', 'userid', 'sAMAccountName']
email LDAP attribute for user email. no ['mail', 'email', 'userPrincipalName']
name LDAP attribute for user display name. If no full name could be found at the attribute specified for name, the full name is determined using the attributes specified for first_name and last_name. no 'cn' or 'displayName'
first_name LDAP attribute for user first name. no 'givenName'
last_name LDAP attribute for user last name. no 'sn'

LDAP Sync Configuration Settings

Setting Description Required Examples
group_base Base used to search for groups. no 'ou=groups,dc=gitlab,dc=example'
admin_group The CN of a group containing GitLab administrators. Note: Not cn=administrators or the full DN. no 'administrators'
external_groups An array of CNs of groups containing users that should be considered external. Note: Not cn=interns or the full DN. no ['interns', 'contractors']
sync_ssh_keys The LDAP attribute containing a user’s public SSH key. no 'sshPublicKey' or false if not set

Set up LDAP user filter

If you want to limit all GitLab access to a subset of the LDAP users on your LDAP server, the first step should be to narrow the configured base. However, it is sometimes necessary to filter users further. In this case, you can set up an LDAP user filter. The filter must comply with RFC 4515.

Omnibus configuration

gitlab_rails['ldap_servers'] = {
'main' => {
  # snip...
  'user_filter' => '(employeeType=developer)'
  }
}

Source configuration

production:
  ldap:
    servers:
      main:
        # snip...
        user_filter: '(employeeType=developer)'

If you want to limit access to the nested members of an Active Directory group, you can use the following syntax:

(memberOf:1.2.840.113556.1.4.1941:=CN=My Group,DC=Example,DC=com)

For more information about this “LDAP_MATCHING_RULE_IN_CHAIN” filter, see the following Microsoft Search Filter Syntax document. Support for nested members in the user filter should not be confused with group sync nested groups support.

Please note that GitLab does not support the custom filter syntax used by OmniAuth LDAP.

Escaping special characters

The user_filter DN can contain special characters. For example:

  • A comma:

    OU=GitLab, Inc,DC=gitlab,DC=com
    
  • Open and close brackets:

    OU=Gitlab (Inc),DC=gitlab,DC=com
    

    These characters must be escaped as documented in RFC 4515.

  • Escape commas with \2C. For example:

    OU=GitLab\2C Inc,DC=gitlab,DC=com
    
  • Escape open and close brackets with \28 and \29, respectively. For example:

    OU=Gitlab \28Inc\29,DC=gitlab,DC=com
    

Enabling LDAP username lowercase

Some LDAP servers, depending on their configurations, can return uppercase usernames. This can lead to several confusing issues such as creating links or namespaces with uppercase names.

GitLab can automatically lowercase usernames provided by the LDAP server by enabling the configuration option lowercase_usernames. By default, this configuration option is false.

Omnibus configuration

  1. Edit /etc/gitlab/gitlab.rb:

    gitlab_rails['ldap_servers'] = {
    'main' => {
      # snip...
      'lowercase_usernames' => true
      }
    }
    
  2. Reconfigure GitLab for the changes to take effect.

Source configuration

  1. Edit config/gitlab.yaml:

    production:
      ldap:
        servers:
          main:
            # snip...
            lowercase_usernames: true
    
  2. Restart GitLab for the changes to take effect.

Disable LDAP web sign in

It can be useful to prevent using LDAP credentials through the web UI when an alternative such as SAML is preferred. This allows LDAP to be used for group sync, while also allowing your SAML identity provider to handle additional checks like custom 2FA.

When LDAP web sign in is disabled, users will not see a LDAP tab on the sign in page. This does not disable using LDAP credentials for Git access.

Omnibus configuration

  1. Edit /etc/gitlab/gitlab.rb:

    gitlab_rails['prevent_ldap_sign_in'] = true
    
  2. Reconfigure GitLab for the changes to take effect.

Source configuration

  1. Edit config/gitlab.yaml:

    production:
      ldap:
        prevent_ldap_sign_in: true
    
  2. Restart GitLab for the changes to take effect.

Encryption

TLS Server Authentication

There are two encryption methods, simple_tls and start_tls.

For either encryption method, if setting verify_certificates: false, TLS encryption is established with the LDAP server before any LDAP-protocol data is exchanged but no validation of the LDAP server’s SSL certificate is performed.

Limitations

TLS Client Authentication

Not implemented by Net::LDAP.

You should disable anonymous LDAP authentication and enable simple or SASL authentication. The TLS client authentication setting in your LDAP server cannot be mandatory and clients cannot be authenticated with the TLS protocol.

Multiple LDAP servers

With GitLab Enterprise Edition Starter, you can configure multiple LDAP servers that your GitLab instance will connect to.

To add another LDAP server:

  1. Duplicate the settings under the main configuration.
  2. Edit them to match the additional LDAP server.

Be sure to choose a different provider ID made of letters a-z and numbers 0-9. This ID will be stored in the database so that GitLab can remember which LDAP server a user belongs to.

Multiple LDAP Servers Login

Based on the example illustrated on the image above, our gitlab.rb configuration would look like:

gitlab_rails['ldap_enabled'] = true
gitlab_rails['ldap_servers'] = {
'main' => {
  'label' => 'GitLab AD',
  'host' =>  'ad.example.org',
  'port' => 636,
  ...
  },

'secondary' => {
  'label' => 'GitLab Secondary AD',
  'host' =>  'ad-secondary.example.net',
  'port' => 636,
  ...
  },

'tertiary' => {
  'label' => 'GitLab Tertiary AD',
  'host' =>  'ad-tertiary.example.net',
  'port' => 636,
  ...
  }
  
}
Note: Any number of LDAP servers can be configured. However, make sure to use a unique naming convention for the label section of each entry as this will be the display name of the tab shown on the sign-in page.

User sync

Once per day, GitLab runs a worker to check and update GitLab users against LDAP.

The process executes the following access checks:

  • Ensure the user is still present in LDAP.
  • If the LDAP server is Active Directory, ensure the user is active (not blocked/disabled state). This will only be checked if active_directory: true is set in the LDAP configuration.
Note: In Active Directory, a user is marked as disabled/blocked if the user account control attribute (userAccountControl:1.2.840.113556.1.4.803) has bit 2 set. See https://ctovswild.com/2009/09/03/bitmask-searches-in-ldap/ for more information.

The user will be set to ldap_blocked state in GitLab if the above conditions fail. This means the user will not be able to login or push/pull code.

The process will also update the following user information:

  • Email address.
  • If sync_ssh_keys is set, SSH public keys.
  • If Kerberos is enabled, Kerberos identity.
Note: The LDAP sync process updates existing users while new users are created on first sign in.

Adjusting LDAP user sync schedule

Note: These are cron formatted values. You can use a crontab generator to create these values, for example http://www.crontabgenerator.com/.

By default, GitLab will run a worker once per day at 01:30 a.m. server time to check and update GitLab users against LDAP.

You can manually configure LDAP user sync times by setting the following configuration values. The example below shows how to set LDAP user sync to run once every 12 hours at the top of the hour.

Omnibus installations

  1. Edit /etc/gitlab/gitlab.rb:

    gitlab_rails['ldap_sync_worker_cron'] = "0 */12 * * *"
    
  2. Reconfigure GitLab for the changes to take effect.

Source installations

  1. Edit config/gitlab.yaml:

    cron_jobs:
      ldap_sync_worker_cron:
        "0 */12 * * *"
    
  2. Restart GitLab for the changes to take effect.

Group Sync

If your LDAP supports the memberof property, when the user signs in for the first time GitLab will trigger a sync for groups the user should be a member of. That way they don’t need to wait for the hourly sync to be granted access to their groups and projects.

A group sync process will run every hour on the hour, and group_base must be set in LDAP configuration for LDAP synchronizations based on group CN to work. This allows GitLab group membership to be automatically updated based on LDAP group members.

The group_base configuration should be a base LDAP ‘container’, such as an ‘organization’ or ‘organizational unit’, that contains LDAP groups that should be available to GitLab. For example, group_base could be ou=groups,dc=example,dc=com. In the config file it will look like the following.

Omnibus configuration

  1. Edit /etc/gitlab/gitlab.rb:

    gitlab_rails['ldap_servers'] = {
    'main' => {
      # snip...
      'group_base' => 'ou=groups,dc=example,dc=com',
      }
    }
    
  2. Apply your changes to GitLab.

Source configuration

  1. Edit /home/git/gitlab/config/gitlab.yml:

    production:
      ldap:
        servers:
          main:
            # snip...
            group_base: ou=groups,dc=example,dc=com
    
  2. Restart GitLab for the changes to take effect.

To take advantage of group sync, group owners or maintainers will need to create one or more LDAP group links.

For information on adding group links via CNs and filters, refer to the GitLab groups documentation.

Administrator sync

As an extension of group sync, you can automatically manage your global GitLab administrators. Specify a group CN for admin_group and all members of the LDAP group will be given administrator privileges. The configuration will look like the following.

Note: Administrators will not be synced unless group_base is also specified alongside admin_group. Also, only specify the CN of the admin group, as opposed to the full DN.

Omnibus configuration

  1. Edit /etc/gitlab/gitlab.rb:

    gitlab_rails['ldap_servers'] = {
    'main' => {
      # snip...
      'group_base' => 'ou=groups,dc=example,dc=com',
      'admin_group' => 'my_admin_group',
      }
    }
    
  2. Apply your changes to GitLab.

Source configuration

  1. Edit /home/git/gitlab/config/gitlab.yml:

    production:
      ldap:
        servers:
          main:
            # snip...
            group_base: ou=groups,dc=example,dc=com
            admin_group: my_admin_group
    
  2. Restart GitLab for the changes to take effect.

Global group memberships lock

“Lock memberships to LDAP synchronization” setting allows instance administrators to lock down user abilities to invite new members to a group.

When enabled, the following applies:

  • Only administrator can manage memberships of any group including access levels.
  • Users are not allowed to share project with other groups or invite members to a project created in a group.

To enable it you need to:

  1. Enable LDAP
  2. Navigate to (admin) Admin Area > Settings -> Visibility and access controls.
  3. Make sure the “Lock memberships to LDAP synchronization” checkbox is enabled.

Adjusting LDAP group sync schedule

Note: These are cron formatted values. You can use a crontab generator to create these values, for example Crontab Generator.

By default, GitLab runs a group sync process every hour, on the hour.

Important: It’s recommended that you do not start the sync process too frequently as this could lead to multiple syncs running concurrently. This is primarily a concern for installations with a large number of LDAP users. Please review the LDAP group sync benchmark metrics to see how your installation compares before proceeding.

You can manually configure LDAP group sync times by setting the following configuration values. The example below shows how to set group sync to run once every 2 hours at the top of the hour.

Omnibus installations

  1. Edit /etc/gitlab/gitlab.rb:

    gitlab_rails['ldap_group_sync_worker_cron'] = "0 */2 * * * *"
    
  2. Reconfigure GitLab for the changes to take effect.

Source installations

  1. Edit config/gitlab.yaml:

    cron_jobs:
      ldap_group_sync_worker_cron:
          "*/30 * * * *"
    
  2. Restart GitLab for the changes to take effect.

External groups

Using the external_groups setting will allow you to mark all users belonging to these groups as external users. Group membership is checked periodically through the LdapGroupSync background task.

Omnibus configuration

  1. Edit /etc/gitlab/gitlab.rb:

    gitlab_rails['ldap_servers'] = {
    'main' => {
      # snip...
      'external_groups' => ['interns', 'contractors'],
      }
    }
    
  2. Apply your changes to GitLab.

Source configuration

  1. Edit config/gitlab.yaml:

    production:
      ldap:
        servers:
          main:
            # snip...
            external_groups: ['interns', 'contractors']
    
  2. Restart GitLab for the changes to take effect.

Group sync technical details

There is a lot going on with group sync ‘under the hood’. This section outlines what LDAP queries are executed and what behavior you can expect from group sync.

Group member access will be downgraded from a higher level if their LDAP group membership changes. For example, if a user has ‘Owner’ rights in a group and the next group sync reveals they should only have ‘Developer’ privileges, their access will be adjusted accordingly. The only exception is if the user is the last owner in a group. Groups need at least one owner to fulfill administrative duties.

Supported LDAP group types/attributes

GitLab supports LDAP groups that use member attributes:

  • member
  • submember
  • uniquemember
  • memberof
  • memberuid.

This means group sync supports, at least, LDAP groups with the following object classes: groupOfNames, posixGroup, and groupOfUniqueNames.

Other object classes should work fine as long as members are defined as one of the mentioned attributes. This also means GitLab supports Microsoft Active Directory, Apple Open Directory, Open LDAP, and 389 Server. Other LDAP servers should work, too.

Active Directory also supports nested groups. Group sync will recursively resolve membership if active_directory: true is set in the configuration file.

Note: Nested group memberships are resolved only if the nested group is found within the configured group_base. For example, if GitLab sees a nested group with DN cn=nested_group,ou=special_groups,dc=example,dc=com but the configured group_base is ou=groups,dc=example,dc=com, cn=nested_group is ignored.

Queries

  • Each LDAP group is queried a maximum of one time with base group_base and filter (cn=<cn_from_group_link>).
  • If the LDAP group has the memberuid attribute, GitLab will execute another LDAP query per member to obtain each user’s full DN. These queries are executed with base base, scope ‘base object’, and a filter depending on whether user_filter is set. Filter may be (uid=<uid_from_group>) or a joining of user_filter.

Benchmarks

Group sync was written to be as performant as possible. Data is cached, database queries are optimized, and LDAP queries are minimized. The last benchmark run revealed the following metrics:

For 20000 LDAP users, 11000 LDAP groups and 1000 GitLab groups with 10 LDAP group links each:

  • Initial sync (no existing members assigned in GitLab) took 1.8 hours
  • Subsequent syncs (checking membership, no writes) took 15 minutes

These metrics are meant to provide a baseline and performance may vary based on any number of factors. This was a pretty extreme benchmark and most instances will not have near this many users or groups. Disk speed, database performance, network and LDAP server response time will affect these metrics.

Troubleshooting

Please see our administrator guide to troubleshooting LDAP.