---
stage: Software Supply Chain Security
group: Authentication
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://handbook.gitlab.com/handbook/product/ux/technical-writing/#assignments
---

# Troubleshooting LDAP

DETAILS:
**Tier:** Free, Premium, Ultimate
**Offering:** Self-managed

If you are an administrator, use the following information to troubleshoot LDAP.

## Common Problems & Workflows

### Connection

#### Connection refused

If you're getting `Connection Refused` error messages when attempting to
connect to the LDAP server, review the LDAP `port` and `encryption` settings
used by GitLab. Common combinations are `encryption: 'plain'` and `port: 389`,
or `encryption: 'simple_tls'` and `port: 636`.

#### Connection times out

If GitLab cannot reach your LDAP endpoint, you see a message like this:

```plaintext
Could not authenticate you from Ldapmain because "Connection timed out - user specified timeout".
```

If your configured LDAP provider and/or endpoint is offline or otherwise
unreachable by GitLab, no LDAP user is able to authenticate and sign-in.
GitLab does not cache or store credentials for LDAP users to provide authentication
during an LDAP outage.

Contact your LDAP provider or administrator if you are seeing this error.

#### Referral error

If you see `LDAP search error: Referral` in the logs, or when troubleshooting
LDAP Group Sync, this error may indicate a configuration problem. The LDAP
configuration `/etc/gitlab/gitlab.rb` (Omnibus) or `config/gitlab.yml` (source)
is in YAML format and is sensitive to indentation. Check that `group_base` and
`admin_group` configuration keys are indented 2 spaces past the server
identifier. The default identifier is `main` and an example snippet looks like
the following:

```yaml
main: # 'main' is the GitLab 'provider ID' of this LDAP server
  label: 'LDAP'
  host: 'ldap.example.com'
  ...
  group_base: 'cn=my_group,ou=groups,dc=example,dc=com'
  admin_group: 'my_admin_group'
```

#### Query LDAP

DETAILS:
**Tier:** Premium, Ultimate
**Offering:** Self-managed

The following allows you to perform a search in LDAP using the rails console.
Depending on what you're trying to do, it may make more sense to query [a user](#query-a-user-in-ldap)
or [a group](#query-a-group-in-ldap) directly, or even [use `ldapsearch`](#ldapsearch) instead.

```ruby
adapter = Gitlab::Auth::Ldap::Adapter.new('ldapmain')
options = {
    # :base is required
    # use .base or .group_base
    base: adapter.config.group_base,

    # :filter is optional
    # 'cn' looks for all "cn"s under :base
    # '*' is the search string - here, it's a wildcard
    filter: Net::LDAP::Filter.eq('cn', '*'),

    # :attributes is optional
    # the attributes we want to get returned
    attributes: %w(dn cn memberuid member submember uniquemember memberof)
}
adapter.ldap_search(options)
```

When using OIDs in the filter, replace `Net::LDAP::Filter.eq` with `Net::LDAP::Filter.construct`:

```ruby
adapter = Gitlab::Auth::Ldap::Adapter.new('ldapmain')
options = {
    # :base is required
    # use .base or .group_base
    base: adapter.config.base,

    # :filter is optional
    # This filter includes OID 1.2.840.113556.1.4.1941
    # It will search for all direct and nested members of the group gitlab_grp in the LDAP directory
    filter: Net::LDAP::Filter.construct("(memberOf:1.2.840.113556.1.4.1941:=CN=gitlab_grp,DC=example,DC=com)"),

    # :attributes is optional
    # the attributes we want to get returned
    attributes: %w(dn cn memberuid member submember uniquemember memberof)
}
adapter.ldap_search(options)
```

For examples of how this is run,
[review the `Adapter` module](https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/lib/ee/gitlab/auth/ldap/adapter.rb).

### User sign-ins

#### No users are found

If [you've confirmed](#ldap-check) that a connection to LDAP can be
established but GitLab doesn't show you LDAP users in the output, one of the
following is most likely true:

- The `bind_dn` user doesn't have enough permissions to traverse the user tree.
- The users don't fall under the [configured `base`](index.md#configure-ldap).
- The [configured `user_filter`](index.md#set-up-ldap-user-filter) blocks access to the users.

In this case, you con confirm which of the above is true using
[ldapsearch](#ldapsearch) with the existing LDAP configuration in your
`/etc/gitlab/gitlab.rb`.

#### Users cannot sign-in

A user can have trouble signing in for any number of reasons. To get started,
here are some questions to ask yourself:

- Does the user fall under the [configured `base`](index.md#configure-ldap) in
  LDAP? The user must fall under this `base` to sign in.
- Does the user pass through the [configured `user_filter`](index.md#set-up-ldap-user-filter)?
  If one is not configured, this question can be ignored. If it is, then the
  user must also pass through this filter to be allowed to sign in.
  - Refer to our documentation on [debugging the `user_filter`](#debug-ldap-user-filter).

If the above are both okay, the next place to look for the problem is
the logs themselves while reproducing the issue.

- Ask the user to sign in and let it fail.
- [Look through the output](#gitlab-logs) for any errors or other
  messages about the sign-in. You may see one of the other error messages on
  this page, in which case that section can help resolve the issue.

If the logs don't lead to the root of the problem, use the
[rails console](#rails-console) to [query this user](#query-a-user-in-ldap)
to see if GitLab can read this user on the LDAP server.

It can also be helpful to
[debug a user sync](#sync-all-users) to
investigate further.

#### Users see an error "Invalid login or password."

> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/438144) in GitLab 16.10.

If users see this error, it might be because they are trying to sign in using the **Standard** sign-in form instead of the **LDAP** sign-in form.

To resolve, ask the user to enter their LDAP username and password into the **LDAP** sign-in form.

#### Invalid credentials on sign-in

If that the sign-in credentials used are accurate on LDAP, ensure the following
are true for the user in question:

- Make sure the user you are binding with has enough permissions to read the user's
  tree and traverse it.
- Check that the `user_filter` is not blocking otherwise valid users.
- Run [an LDAP check command](#ldap-check) to make sure that the LDAP settings
  are correct and [GitLab can see your users](#no-users-are-found).

#### Access denied for your LDAP account

There is [a bug](https://gitlab.com/gitlab-org/gitlab/-/issues/235930) that
may affect users with [Auditor level access](../../auditor_users.md). When
downgrading from Premium/Ultimate, Auditor users who try to sign in
may see the following message: `Access denied for your LDAP account`.

We have a workaround, based on toggling the access level of affected users:

1. On the left sidebar, at the bottom, select **Admin**.
1. Select **Overview > Users**.
1. Select the name of the affected user.
1. In the upper-right corner, select **Edit**.
1. Change the user's access level from `Regular` to `Administrator` (or vice versa).
1. At the bottom of the page, select **Save changes**.
1. In the upper-right corner, select **Edit** again.
1. Restore the user's original access level (`Regular` or `Administrator`)
   and select **Save changes** again.

The user should now be able to sign in.

#### Email has already been taken

A user tries to sign in with the correct LDAP credentials, is denied access,
and the [production.log](../../logs/index.md#productionlog) shows an error that looks like this:

```plaintext
(LDAP) Error saving user <USER DN> (email@example.com): ["Email has already been taken"]
```

This error is referring to the email address in LDAP, `email@example.com`. Email
addresses must be unique in GitLab and LDAP links to a user's primary email (as opposed
to any of their possibly-numerous secondary emails). Another user (or even the
same user) has the email `email@example.com` set as a secondary email, which
is throwing this error.

We can check where this conflicting email address is coming from using the
[rails console](#rails-console). In the console, run the following:

```ruby
# This searches for an email among the primary AND secondary emails
user = User.find_by_any_email('email@example.com')
user.username
```

This shows you which user has this email address. One of two steps must be taken here:

- To create a new GitLab user/username for this user when signing in with LDAP,
  remove the secondary email to remove the conflict.
- To use an existing GitLab user/username for this user to use with LDAP,
  remove this email as a secondary email and make it a primary one so GitLab
  associates this profile to the LDAP identity.

The user can do either of these steps
[in their profile](../../../user/profile/index.md#access-your-user-profile) or an administrator can do it.

#### Projects limit errors

The following errors indicate that a limit or restriction is activated, but an associated data
field contains no data:

- `Projects limit can't be blank`.
- `Projects limit is not a number`.

To resolve this:

1. On the left sidebar, at the bottom, select **Admin**.
1. Select **Settings > General**.
1. Expand both of the following:
   - **Account and limit**.
   - **Sign-up restrictions**.
1. Check, for example, the **Default projects limit** or **Allowed domains for sign-ups**
   fields and ensure that a relevant value is configured.

#### Debug LDAP user filter

[`ldapsearch`](#ldapsearch) allows you to test your configured
[user filter](index.md#set-up-ldap-user-filter)
to confirm that it returns the users you expect it to return.

```shell
ldapsearch -H ldaps://$host:$port -D "$bind_dn" -y bind_dn_password.txt  -b "$base" "$user_filter" sAMAccountName
```

- Variables beginning with a `$` refer to a variable from the LDAP section of
  your configuration file.
- Replace `ldaps://` with `ldap://` if you are using the plain authentication method.
  Port `389` is the default `ldap://` port and `636` is the default `ldaps://`
  port.
- We are assuming the password for the `bind_dn` user is in `bind_dn_password.txt`.

#### Sync all users

DETAILS:
**Tier:** Premium, Ultimate
**Offering:** Self-managed

The output from a manual [user sync](ldap_synchronization.md#user-sync) can show you what happens when
GitLab tries to sync its users against LDAP. Enter the [rails console](#rails-console)
and then run:

```ruby
Rails.logger.level = Logger::DEBUG

LdapSyncWorker.new.perform
```

Next, [learn how to read the output](#example-console-output-after-a-user-sync).

##### Example console output after a user sync

DETAILS:
**Tier:** Premium, Ultimate
**Offering:** Self-managed

The output from a [manual user sync](#sync-all-users) is very verbose, and a
single user's successful sync can look like this:

```shell
Syncing user John, email@example.com
  Identity Load (0.9ms)  SELECT  "identities".* FROM "identities" WHERE "identities"."user_id" = 20 AND (provider LIKE 'ldap%') LIMIT 1
Instantiating Gitlab::Auth::Ldap::Person with LDIF:
dn: cn=John Smith,ou=people,dc=example,dc=com
cn: John Smith
mail: email@example.com
memberof: cn=admin_staff,ou=people,dc=example,dc=com
uid: John

  UserSyncedAttributesMetadata Load (0.9ms)  SELECT  "user_synced_attributes_metadata".* FROM "user_synced_attributes_metadata" WHERE "user_synced_attributes_metadata"."user_id" = 20 LIMIT 1
   (0.3ms)  BEGIN
  Namespace Load (1.0ms)  SELECT  "namespaces".* FROM "namespaces" WHERE "namespaces"."owner_id" = 20 AND "namespaces"."type" IS NULL LIMIT 1
  Route Load (0.8ms)  SELECT  "routes".* FROM "routes" WHERE "routes"."source_id" = 27 AND "routes"."source_type" = 'Namespace' LIMIT 1
  Ci::Runner Load (1.1ms)  SELECT "ci_runners".* FROM "ci_runners" INNER JOIN "ci_runner_namespaces" ON "ci_runners"."id" = "ci_runner_namespaces"."runner_id" WHERE "ci_runner_namespaces"."namespace_id" = 27
   (0.7ms)  COMMIT
   (0.4ms)  BEGIN
  Route Load (0.8ms)  SELECT "routes".* FROM "routes" WHERE (LOWER("routes"."path") = LOWER('John'))
  Namespace Load (1.0ms)  SELECT  "namespaces".* FROM "namespaces" WHERE "namespaces"."id" = 27 LIMIT 1
  Route Exists (0.9ms)  SELECT  1 AS one FROM "routes" WHERE LOWER("routes"."path") = LOWER('John') AND "routes"."id" != 50 LIMIT 1
  User Update (1.1ms)  UPDATE "users" SET "updated_at" = '2019-10-17 14:40:59.751685', "last_credential_check_at" = '2019-10-17 14:40:59.738714' WHERE "users"."id" = 20
```

There's a lot here, so let's go over what could be helpful when debugging.

First, GitLab looks for all users that have previously
signed in with LDAP and iterate on them. Each user's sync starts with
the following line that contains the user's username and email, as they
exist in GitLab now:

```shell
Syncing user John, email@example.com
```

If you don't find a particular user's GitLab email in the output, then that
user hasn't signed in with LDAP yet.

Next, GitLab searches its `identities` table for the existing
link between this user and the configured LDAP providers:

```sql
  Identity Load (0.9ms)  SELECT  "identities".* FROM "identities" WHERE "identities"."user_id" = 20 AND (provider LIKE 'ldap%') LIMIT 1
```

The identity object has the DN that GitLab uses to look for the user
in LDAP. If the DN isn't found, the email is used instead. We can see that
this user is found in LDAP:

```shell
Instantiating Gitlab::Auth::Ldap::Person with LDIF:
dn: cn=John Smith,ou=people,dc=example,dc=com
cn: John Smith
mail: email@example.com
memberof: cn=admin_staff,ou=people,dc=example,dc=com
uid: John
```

If the user wasn't found in LDAP with either the DN or email, you may see the
following message instead:

```shell
LDAP search error: No Such Object
```

...in which case the user is blocked:

```shell
  User Update (0.4ms)  UPDATE "users" SET "state" = $1, "updated_at" = $2 WHERE "users"."id" = $3  [["state", "ldap_blocked"], ["updated_at", "2019-10-18 15:46:22.902177"], ["id", 20]]
```

After the user is found in LDAP, the rest of the output updates the GitLab
database with any changes.

#### Query a user in LDAP

This tests that GitLab can reach out to LDAP and read a particular user.
It can expose potential errors connecting to and/or querying LDAP
that may seem to fail silently in the GitLab UI.

```ruby
Rails.logger.level = Logger::DEBUG

adapter = Gitlab::Auth::Ldap::Adapter.new('ldapmain') # If `main` is the LDAP provider
Gitlab::Auth::Ldap::Person.find_by_uid('<uid>', adapter)
```

### Group memberships

DETAILS:
**Tier:** Premium, Ultimate
**Offering:** Self-managed

#### Memberships not granted

Sometimes you may think a particular user should be added to a GitLab group through
LDAP group sync, but for some reason it's not happening. You can check several
things to debug the situation.

- Ensure LDAP configuration has a `group_base` specified.
  [This configuration](ldap_synchronization.md#group-sync) is required for group sync to work properly.
- Ensure the correct [LDAP group link is added to the GitLab group](ldap_synchronization.md#add-group-links).
- Check that the user has an LDAP identity:
  1. Sign in to GitLab as an administrator user.
  1. On the left sidebar, at the bottom, select **Admin**.
  1. On the left sidebar, select **Overview > Users**.
  1. Search for the user.
  1. Open the user by selecting their name. Do not select **Edit**.
  1. Select the **Identities** tab. There should be an LDAP identity with
     an LDAP DN as the `Identifier`. If not, this user hasn't signed in with
     LDAP yet and must do so first.
- You've waited an hour or [the configured interval](ldap_synchronization.md#adjust-ldap-group-sync-schedule) for
  the group to sync. To speed up the process, either go to the GitLab group **Manage > Members**
  and press **Sync now** (sync one group) or [run the group sync Rake task](../../raketasks/ldap.md#run-a-group-sync)
  (sync all groups).

If all of the above looks good, jump in to a little more advanced debugging in
the rails console.

1. Enter the [rails console](#rails-console).
1. Choose a GitLab group to test with. This group should have an LDAP group link
   already configured.
1. [Enable debug logging, find the above GitLab group, and sync it with LDAP](#sync-one-group).
1. Look through the output of the sync. See [example log output](#example-console-output-after-a-group-sync)
   for how to read the output.
1. If you still aren't able to see why the user isn't being added, [query the LDAP group directly](#query-a-group-in-ldap)
   to see what members are listed.
1. Is the user's DN or UID in one of the lists from the above output? One of the DNs or
   UIDs here should match the 'Identifier' from the LDAP identity checked earlier. If it doesn't,
   the user does not appear to be in the LDAP group.

#### Cannot add service account user to group when LDAP sync is enabled

When LDAP sync is enabled for a group, you cannot use the "invite" dialog to invite new group members.

To resolve this issue in GitLab 16.8 and later, you can invite service accounts to and remove them from a group using the [group members API endpoints](../../../api/members.md#add-a-member-to-a-group-or-project).

#### Administrator privileges not granted

When [Administrator sync](ldap_synchronization.md#administrator-sync) has been configured
but the configured users aren't granted the correct administrator privileges, confirm
the following are true:

- A [`group_base` is also configured](ldap_synchronization.md#group-sync).
- The configured `admin_group` in the `gitlab.rb` is a CN, rather than a DN or an array.
- This CN falls under the scope of the configured `group_base`.
- The members of the `admin_group` have already signed into GitLab with their LDAP
  credentials. GitLab only grants administrator access to the users whose
  accounts are already connected to LDAP.

If all the above are true and the users are still not getting access,
[run a manual group sync](#sync-all-groups) in the rails console and
[look through the output](#example-console-output-after-a-group-sync) to see what happens when
GitLab syncs the `admin_group`.

#### Sync now button stuck in the UI

The **Sync now** button on the **Group > Members** page of a group can become stuck. The button becomes stuck after it is pressed and the page is reloaded. The button then
cannot be selected again.

The **Sync now** button can become stuck for many reasons and requires debugging for specific cases. The following are two possible causes and possible solutions to the problem.

##### Invalid memberships

The **Sync now** button becomes stuck if some of the group's members or requesting members are invalid. You can track progress on improving the visibility of this problem in
a [relevant issue](https://gitlab.com/gitlab-org/gitlab/-/issues/348226). You can use a [Rails console](#rails-console) to confirm if this problem is causing the **Sync now**
button to be stuck:

```ruby
# Find the group in question
group = Group.find_by(name: 'my_gitlab_group')

# Look for errors on the Group itself
group.valid?
group.errors.map(&:full_messages)

# Look for errors among the group's members and requesters
group.requesters.map(&:valid?)
group.requesters.map(&:errors).map(&:full_messages)
group.members.map(&:valid?)
group.members.map(&:errors).map(&:full_messages)
```

A displayed error can identify the problem and point to a solution. For example, the Support Team has seen the following error:

```ruby
irb(main):018:0> group.members.map(&:errors).map(&:full_messages)
=> [["The member's email address is not allowed for this group. Go to the group's &#39;Settings &gt; General&#39; page, and check &#39;Restrict membership by email domain&#39;."]]
```

This error showed that an Administrator chose to [restrict group membership by email domain](../../../user/group/access_and_permissions.md#restrict-group-access-by-domain),
but there was a typo in the domain. After the domain setting was fixed, the **Sync now** button functioned again.

##### Missing LDAP configuration on Sidekiq nodes

The **Sync now** button becomes stuck when GitLab is scaled over multiple nodes and the LDAP configuration is missing from
[the `/etc/gitlab/gitlab.rb` on the nodes running Sidekiq](../../sidekiq/index.md#configure-ldap-and-user-or-group-synchronization).
In this case, the Sidekiq jobs seem to disappear.

LDAP is required on the Sidekiq nodes because LDAP has multiple jobs that are
run asynchronously that require a local LDAP configuration:

- [User sync](ldap_synchronization.md#user-sync).
- [Group sync](ldap_synchronization.md#group-sync).

You can test whether missing LDAP configuration is the problem by running [the Rake task to check LDAP](#ldap-check)
on each node that is running Sidekiq. If LDAP is set up correctly on this node, it connects to the LDAP server and returns users.

To solve this issue, [configure LDAP](../../sidekiq/index.md#configure-ldap-and-user-or-group-synchronization) on the Sidekiq nodes.
When configured, run [the Rake task to check LDAP](#ldap-check) to confirm
that the GitLab node can connect to LDAP.

#### Sync all groups

NOTE:
To sync all groups manually when debugging is unnecessary,
[use the Rake task](../../raketasks/ldap.md#run-a-group-sync) instead.

The output from a manual [group sync](ldap_synchronization.md#group-sync) can show you what happens
when GitLab syncs its LDAP group memberships against LDAP. Enter the [rails console](#rails-console)
and then run:

```ruby
Rails.logger.level = Logger::DEBUG

LdapAllGroupsSyncWorker.new.perform
```

Next, [learn how to read the output](#example-console-output-after-a-group-sync).

##### Example console output after a group sync

Like the output from the user sync, the output from the
[manual group sync](#sync-all-groups) is also very verbose. However, it contains lots
of helpful information.

Indicates the point where syncing actually begins:

```shell
Started syncing 'ldapmain' provider for 'my_group' group
```

The following entry shows an array of all user DNs GitLab sees in the LDAP server.
These DNs are the users for a single LDAP group, not a GitLab group. If
you have multiple LDAP groups linked to this GitLab group, you see multiple
log entries like this - one for each LDAP group. If you don't see an LDAP user
DN in this log entry, LDAP is not returning the user when we do the lookup.
Verify the user is actually in the LDAP group.

```shell
Members in 'ldap_group_1' LDAP group: ["uid=john0,ou=people,dc=example,dc=com",
"uid=mary0,ou=people,dc=example,dc=com", "uid=john1,ou=people,dc=example,dc=com",
"uid=mary1,ou=people,dc=example,dc=com", "uid=john2,ou=people,dc=example,dc=com",
"uid=mary2,ou=people,dc=example,dc=com", "uid=john3,ou=people,dc=example,dc=com",
"uid=mary3,ou=people,dc=example,dc=com", "uid=john4,ou=people,dc=example,dc=com",
"uid=mary4,ou=people,dc=example,dc=com"]
```

Shortly after each of the above entries, you see a hash of resolved member
access levels. This hash represents all user DNs GitLab thinks should have
access to this group, and at which access level (role). This hash is additive,
and more DNs may be added, or existing entries modified, based on additional
LDAP group lookups. The very last occurrence of this entry should indicate
exactly which users GitLab believes should be added to the group.

NOTE:
10 is `Guest`, 20 is `Reporter`, 30 is `Developer`, 40 is `Maintainer`
and 50 is `Owner`.

```shell
Resolved 'my_group' group member access: {"uid=john0,ou=people,dc=example,dc=com"=>30,
"uid=mary0,ou=people,dc=example,dc=com"=>30, "uid=john1,ou=people,dc=example,dc=com"=>30,
"uid=mary1,ou=people,dc=example,dc=com"=>30, "uid=john2,ou=people,dc=example,dc=com"=>30,
"uid=mary2,ou=people,dc=example,dc=com"=>30, "uid=john3,ou=people,dc=example,dc=com"=>30,
"uid=mary3,ou=people,dc=example,dc=com"=>30, "uid=john4,ou=people,dc=example,dc=com"=>30,
"uid=mary4,ou=people,dc=example,dc=com"=>30}
```

It's not uncommon to see warnings like the following. These indicate that GitLab
would have added the user to a group, but the user could not be found in GitLab.
Usually this is not a cause for concern.

If you think a particular user should already exist in GitLab, but you're seeing
this entry, it could be due to a mismatched DN stored in GitLab. See
[User DN and email have changed](#user-dn-and-email-have-changed) to update the user's LDAP identity.

```shell
User with DN `uid=john0,ou=people,dc=example,dc=com` should have access
to 'my_group' group but there is no user in GitLab with that
identity. Membership will be updated when the user signs in for
the first time.
```

Finally, the following entry says syncing has finished for this group:

```shell
Finished syncing all providers for 'my_group' group
```

When all the configured group links have been synchronized, GitLab looks
for any Administrators or External users to sync:

```shell
Syncing admin users for 'ldapmain' provider
```

The output looks similar to what happens with a single group, and then
this line indicates the sync is finished:

```shell
Finished syncing admin users for 'ldapmain' provider
```

If [administrator sync](ldap_synchronization.md#administrator-sync) is not configured, you see a message
stating as such:

```shell
No `admin_group` configured for 'ldapmain' provider. Skipping
```

#### Sync one group

[Syncing all groups](#sync-all-groups) can produce a lot of noise in the output, which can be
distracting when you're only interested in troubleshooting the memberships of
a single GitLab group. In that case, here's how you can just sync this group
and see its debug output:

```ruby
Rails.logger.level = Logger::DEBUG

# Find the GitLab group.
# If the output is `nil`, the group could not be found.
# If a bunch of group attributes are in the output, your group was found successfully.
group = Group.find_by(name: 'my_gitlab_group')

# Sync this group against LDAP
EE::Gitlab::Auth::Ldap::Sync::Group.execute_all_providers(group)
```

The output is similar to
[that you get from syncing all groups](#example-console-output-after-a-group-sync).

#### Query a group in LDAP

When you'd like to confirm that GitLab can read a LDAP group and see all its members,
you can run the following:

```ruby
# Find the adapter and the group itself
adapter = Gitlab::Auth::Ldap::Adapter.new('ldapmain') # If `main` is the LDAP provider
ldap_group = EE::Gitlab::Auth::Ldap::Group.find_by_cn('group_cn_here', adapter)

# Find the members of the LDAP group
ldap_group.member_dns
ldap_group.member_uids
```

#### LDAP synchronization does not remove group creator from group

[LDAP synchronization](ldap_synchronization.md) should remove an LDAP group's creator
from that group, if that user does not exist in the group. If running LDAP synchronization
does not do this:

1. Add the user to the LDAP group.
1. Wait until LDAP group synchronization has finished running.
1. Remove the user from the LDAP group.

### User DN and email have changed

If both the primary email **and** the DN change in LDAP, GitLab cannot identify the correct LDAP record of a user. As a
result, GitLab blocks that user. So that GitLab can find the LDAP record, update the user's existing GitLab profile with
at least either:

- The new primary email.
- DN values.

The following script updates the emails for all provided users so they aren't blocked or unable to access their accounts.

NOTE:
The following script requires that any new accounts with the new
email address are removed first. Email addresses must be unique in GitLab.

Go to the [rails console](#rails-console) and then run:

```ruby
# Each entry must include the old username and the new email
emails = {
  'ORIGINAL_USERNAME' => 'NEW_EMAIL_ADDRESS',
  ...
}

emails.each do |username, email|
  user = User.find_by_username(username)
  user.email = email
  user.skip_reconfirmation!
  user.save!
end
```

You can then [run a UserSync](#sync-all-users) to sync the latest DN
for each of these users.

## Could not authenticate from AzureActivedirectoryV2 because "Invalid grant"

When converting from LDAP to SAML you might get an error in Azure that states the following:

```plaintext
Authentication failure! invalid_credentials: OAuth2::Error, invalid_grant.
```

This issue occurs when both of the following are true:

- LDAP identities still exist for users after SAML has been configured for those users.
- You disable LDAP for those users.

You would receive both LDAP and Azure metadata in the logs, which generates the error in Azure.

The workaround for a single user is to remove the LDAP identity from the user in **Admin > Identities**.

To remove multiple LDAP identities, use either of the workarounds for the [`Could not authenticate you from Ldapmain because "Unknown provider"` error](#could-not-authenticate-you-from-ldapmain-because-unknown-provider).

## `Could not authenticate you from Ldapmain because "Unknown provider"`

You can receive the following error when authenticating with an LDAP server:

```plaintext
Could not authenticate you from Ldapmain because "Unknown provider (ldapsecondary). available providers: ["ldapmain"]".
```

This error is caused when using an account that previously authenticated with an LDAP server that is renamed or removed from your GitLab configuration. For example:

- Initially, `main` and `secondary` are set in `ldap_servers` in GitLab configuration.
- The `secondary` setting is removed or renamed to `main`.
- A user attempting to sign in has an `identify` record for `secondary`, but that is no longer configured.

Use the [Rails console](../../operations/rails_console.md) to list affected users and check what LDAP servers they have identities for:

```ruby
ldap_identities = Identity.where(provider: "ldapsecondary")
ldap_identities.each do |identity|
  u=User.find_by_id(identity.user_id)
  ui=Identity.where(user_id: identity.user_id)
  puts "user: #{u.username}\n   #{u.email}\n   last activity: #{u.last_activity_on}\n   #{identity.provider} ID: #{identity.id} external: #{identity.extern_uid}"
  puts "   all identities:"
  ui.each do |alli|
    puts "    - #{alli.provider} ID: #{alli.id} external: #{alli.extern_uid}"
  end
end;nil
```

You can solve this error in two ways.

### Rename references to the LDAP server

This solution is suitable when the LDAP servers are replicas of each other, and the affected users should be able to sign in using a configured LDAP server.
For example, if a load balancer is now used to manage LDAP high availability and a separate secondary sign-in option is no longer needed.

NOTE:
If the LDAP servers aren't replicas of each other, this solution stops affected users from being able to sign in.

To [rename references to the LDAP server](../../raketasks/ldap.md#other-options) that is no longer configured, run:

```shell
sudo gitlab-rake gitlab:ldap:rename_provider[ldapsecondary,ldapmain]
```

### Remove the `identity` records that relate to the removed LDAP server

Prerequisites:

- Ensure that `auto_link_ldap_user` is enabled.

With this solution, after the identity is deleted, affected users can sign in with the
configured LDAP servers and a new `identity` record is created by GitLab.

Because the LDAP server that was removed was `ldapsecondary`, in a [Rails console](../../operations/rails_console.md), delete all the `ldapsecondary` identities:

```ruby
ldap_identities = Identity.where(provider: "ldapsecondary")
ldap_identities.each do |identity|
  puts "Destroying identity: #{identity.id} #{identity.provider}: #{identity.extern_uid}"
  identity.destroy!
rescue => e
  puts 'Error generated when destroying identity:\n ' + e.to_s
end; nil
```

## Expired license causes errors with multiple LDAP servers

Using [multiple LDAP servers](index.md#use-multiple-ldap-servers) requires a valid license. An expired license can
cause:

- `502` errors in the web interface.
- The following error in logs (the actual strategy name depends on the name configured in `/etc/gitlab/gitlab.rb`):

  ```plaintext
  Could not find a strategy with name `Ldapsecondary'. Please ensure it is required or explicitly set it using the :strategy_class option. (Devise::OmniAuth::StrategyNotFound)
  ```

To resolve this error, you must apply a new license to the GitLab instance without the web interface:

1. Remove or comment out the GitLab configuration lines for all non-primary LDAP servers.
1. [Reconfigure GitLab](../../restart_gitlab.md#reconfigure-a-linux-package-installation) so that it temporarily uses only one LDAP server.
1. Enter the [Rails console and add the license key](../../../administration/license_file.md#add-a-license-through-the-console).
1. Re-enable the additional LDAP servers in the GitLab configuration and reconfigure GitLab again.

## Users are being removed from group and re-added again

If a user has been added to a group during group sync, and removed at the next sync, and this has happened repeatedly, make sure that the user doesn't have
multiple or redundant LDAP identities.

If one of those identities was added for an older LDAP provider that is no longer in use, [remove the `identity` records that relate to the removed LDAP server](#remove-the-identity-records-that-relate-to-the-removed-ldap-server).

## Debugging Tools

### LDAP check

The [Rake task to check LDAP](../../raketasks/ldap.md#check) is a valuable tool
to help determine whether GitLab can successfully establish a connection to
LDAP and can get so far as to even read users.

If a connection can't be established, it is likely either because of a problem
with your configuration or a firewall blocking the connection.

- Ensure you don't have a firewall blocking the
  connection, and that the LDAP server is accessible to the GitLab host.
- Look for an error message in the Rake check output, which may lead to your LDAP configuration to
  confirm that the configuration values (specifically `host`, `port`, `bind_dn`, and
  `password`) are correct.
- Look for [errors](#connection) in [the logs](#gitlab-logs) to further debug connection failures.

If GitLab can successfully connect to LDAP but doesn't return any
users, [see what to do when no users are found](#no-users-are-found).

### GitLab logs

If a user account is blocked or unblocked due to the LDAP configuration, a
message is [logged to `application_json.log`](../../logs/index.md#application_jsonlog).

If there is an unexpected error during an LDAP lookup (configuration error,
timeout), the sign-in is rejected and a message is [logged to `production.log`](../../logs/index.md#productionlog).

### ldapsearch

`ldapsearch` is a utility that allows you to query your LDAP server. You can
use it to test your LDAP settings and ensure that the settings you're using
get you the results you expect.

When using `ldapsearch`, be sure to use the same settings you've already
specified in your `gitlab.rb` configuration so you can confirm what happens
when those exact settings are used.

Running this command on the GitLab host also helps confirm that there's no
obstruction between the GitLab host and LDAP.

For example, consider the following GitLab configuration:

```shell
gitlab_rails['ldap_servers'] = YAML.load <<-'EOS' # remember to close this block with 'EOS' below
   main: # 'main' is the GitLab 'provider ID' of this LDAP server
     label: 'LDAP'
     host: '127.0.0.1'
     port: 389
     uid: 'uid'
     encryption: 'plain'
     bind_dn: 'cn=admin,dc=ldap-testing,dc=example,dc=com'
     password: 'Password1'
     active_directory: true
     allow_username_or_email_login: false
     block_auto_created_users: false
     base: 'dc=ldap-testing,dc=example,dc=com'
     user_filter: ''
     attributes:
       username: ['uid', 'userid', 'sAMAccountName']
       email:    ['mail', 'email', 'userPrincipalName']
       name:       'cn'
       first_name: 'givenName'
       last_name:  'sn'
     group_base: 'ou=groups,dc=ldap-testing,dc=example,dc=com'
     admin_group: 'gitlab_admin'
EOS
```

You would run the following `ldapsearch` to find the `bind_dn` user:

```shell
ldapsearch -D "cn=admin,dc=ldap-testing,dc=example,dc=com" \
  -w Password1 \
  -p 389 \
  -h 127.0.0.1 \
  -b "dc=ldap-testing,dc=example,dc=com"
```

The `bind_dn`, `password`, `port`, `host`, and `base` are all
identical to what's configured in the `gitlab.rb`.

#### Use ldapsearch with `start_tls` encryption

The previous example performs an LDAP test in plaintext to port 389. If you are using [`start_tls` encryption](index.md#basic-configuration-settings), in
the `ldapsearch` command include:

- The `-Z` flag.
- The FQDN of the LDAP server.

You must include these because, during TLS negotiation, the FQDN of the LDAP server is evaluated against its certificate:

```shell
ldapsearch -D "cn=admin,dc=ldap-testing,dc=example,dc=com" \
  -w Password1 \
  -p 389 \
  -h "testing.ldap.com" \
  -b "dc=ldap-testing,dc=example,dc=com" -Z
```

#### Use ldapsearch with `simple_tls` encryption

If you are using [`simple_tls` encryption](index.md#basic-configuration-settings) (usually on port 636), include the following in the `ldapsearch` command:

- The LDAP server FQDN with the `-H` flag and the port.
- The full constructed URI.

```shell
ldapsearch -D "cn=admin,dc=ldap-testing,dc=example,dc=com" \
  -w Password1 \
  -H "ldaps://testing.ldap.com:636" \
  -b "dc=ldap-testing,dc=example,dc=com"
```

For more information, see the [official `ldapsearch` documentation](https://linux.die.net/man/1/ldapsearch).

### Using **AdFind** (Windows)

You can use the [`AdFind`](https://learn.microsoft.com/en-us/archive/technet-wiki/7535.adfind-command-examples) utility (on Windows based systems) to test that your LDAP server is accessible and authentication is working correctly. AdFind is a freeware utility built by [Joe Richards](https://www.joeware.net/freetools/tools/adfind/index.htm).

**Return all objects**

You can use the filter `objectclass=*` to return all directory objects.

```shell
adfind -h ad.example.org:636 -ssl -u "CN=GitLabSRV,CN=Users,DC=GitLab,DC=org" -up Password1 -b "OU=GitLab INT,DC=GitLab,DC=org" -f (objectClass=*)
```

**Return single object using filter**

You can also retrieve a single object by **specifying** the object name or full **DN**. In this example we specify the object name only `CN=Leroy Fox`.

```shell
adfind -h ad.example.org:636 -ssl -u "CN=GitLabSRV,CN=Users,DC=GitLab,DC=org" -up Password1 -b "OU=GitLab INT,DC=GitLab,DC=org" -f "(&(objectcategory=person)(CN=Leroy Fox))"
```

### Rails console

WARNING:
It is very easy to create, read, modify, and destroy data with the rails
console. Be sure to run commands exactly as listed.

The rails console is a valuable tool to help debug LDAP problems. It allows you to
directly interact with the application by running commands and seeing how GitLab
responds to them.

For instructions about how to use the rails console, refer to this
[guide](../../operations/rails_console.md#starting-a-rails-console-session).

#### Enable debug output

This provides debug output that shows what GitLab is doing and with what.
This value is not persisted, and is only enabled for this session in the Rails console.

To enable debug output in the rails console, [enter the rails console](#rails-console) and run:

```ruby
Rails.logger.level = Logger::DEBUG
```

#### Get all error messages associated with groups, subgroups, members, and requesters

Collect error messages associated with groups, subgroups, members, and requesters. This
captures error messages that may not appear in the Web interface. This can be especially helpful
for troubleshooting issues with [LDAP group sync](ldap_synchronization.md#group-sync)
and unexpected behavior with users and their membership in groups and subgroups.

```ruby
# Find the group and subgroup
group = Group.find_by_full_path("parent_group")
subgroup = Group.find_by_full_path("parent_group/child_group")

# Group and subgroup errors
group.valid?
group.errors.map(&:full_messages)

subgroup.valid?
subgroup.errors.map(&:full_messages)

# Group and subgroup errors for the members AND requesters
group.requesters.map(&:valid?)
group.requesters.map(&:errors).map(&:full_messages)
group.members.map(&:valid?)
group.members.map(&:errors).map(&:full_messages)
group.members_and_requesters.map(&:errors).map(&:full_messages)

subgroup.requesters.map(&:valid?)
subgroup.requesters.map(&:errors).map(&:full_messages)
subgroup.members.map(&:valid?)
subgroup.members.map(&:errors).map(&:full_messages)
subgroup.members_and_requesters.map(&:errors).map(&:full_messages)
```