LDAP Additions in GitLab EE
This is a continuation of the main LDAP documentation, detailing LDAP features specific to GitLab Enterprise Edition.
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.
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, and 389 Server. GitLab Enterprise Edition includes enhanced integration, including group membership syncing.
Use-cases
- User Sync: Once a day, GitLab will update users against LDAP
- Group Sync: Once an hour, GitLab will update group membership based on LDAP group members
User Sync
Once per day, GitLab will run a worker to check and update GitLab users against LDAP.
The process will execute 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 1
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 will be created on first sign in.
Group Sync
If your LDAP supports the memberof
property, GitLab will add the user to any
new groups they might be added to when the user logs in. That way they don't need
to wait for the hourly sync to be granted access to the groups that they are in
in LDAP.
If group_base
is set in LDAP configuration, a group sync process will run
every hour, on the hour. 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
Edit /etc/gitlab/gitlab.rb
:
gitlab_rails['ldap_servers'] = YAML.load <<-EOS
main:
# snip...
group_base: ou=groups,dc=example,dc=com
EOS
Reconfigure GitLab for the changes to take effect.
Source configuration
Edit /home/git/gitlab/config/gitlab.yml
:
production:
ldap:
servers:
main:
# snip...
group_base: ou=groups,dc=example,dc=com
Restart GitLab for the changes to take effect.
To take advantage of group sync, group owners or masters will need to create an LDAP group link in their group Settings -> LDAP Groups page. Multiple LDAP groups can be linked with a single GitLab group. When the link is created, an access level/role is specified (Guest, Reporter, Developer, Master, or Owner).
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 alongsideadmin_group
. Also, only specify the CN of the admin group, as opposed to the full DN.
Omnibus configuration
Edit /etc/gitlab/gitlab.rb
:
gitlab_rails['ldap_servers'] = YAML.load <<-EOS
main:
# snip...
group_base: ou=groups,dc=example,dc=com
admin_group: my_admin_group
EOS
Reconfigure GitLab for the changes to take effect.
Source configuration
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
Restart GitLab for the changes to take effect.
External Groups
Note: External Groups configuration is only available in GitLab EE Version 8.9 and above.
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
gitlab_rails['ldap_servers'] = YAML.load <<-EOS
main:
# snip...
external_groups: ['interns', 'contractors']
EOS
Reconfigure GitLab for the changes to take effect.
Source configuration
production:
ldap:
servers:
main:
# snip...
external_groups: ['interns', 'contractors']
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
and memberuid
. This means group sync supports, at
least, LDAP groups with object class groupOfNames
, posixGroup
, and
groupOfUniqueName
. 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 membership will only be resolved if the nested group also falls within the configured
group_base
. For example, if GitLab sees a nested group with DNcn=nested_group,ou=special_groups,dc=example,dc=com
but the configuredgroup_base
isou=groups,dc=example,dc=com
,cn=nested_group
will be 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 basebase
, scope 'base object', and a filter depending on whetheruser_filter
is set. Filter may be(uid=<uid_from_group>)
or a joining ofuser_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 20,000 LDAP users, 11,000 LDAP groups and 1,000 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
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:
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'
User DN has changed
When an LDAP user is created in GitLab, their LDAP DN is stored for later reference.
If GitLab cannot find a user by their DN, it will attempt to fallback to finding the user by their email. If the lookup is successful, GitLab will update the stored DN to the new value.
User is not being added to a group
Sometimes you may think a particular user should be added to a GitLab group via LDAP group sync, but for some reason it's not happening. There are several things to check to debug the situation.
- Ensure LDAP configuration has a
group_base
specified. This configuration is required for group sync to work properly. - Ensure the correct LDAP group link is added to the GitLab group. Check group links by visiting the GitLab group, then Settings dropdown -> LDAP groups.
- Check that the user has an LDAP identity
- Sign in to GitLab as an administrator user.
- Navigate to Admin area -> Users.
- Search for the user
- Open the user, by clicking on their name. Do not click 'Edit'.
- Navigate to the Identities tab. There should be an LDAP identity with an LDAP DN as the 'Identifier'.
If all of the above looks good, jump in to a little more advanced debugging. Often, the best way to learn more about why group sync is behaving a certain way is to enable debug logging. There is verbose output that details every step of the sync.
-
Start a Rails console
# For Omnibus installations sudo gitlab-rails console # For installations from source sudo -u git -H bundle exec rails console production
-
Set the log level to debug (only for this session):
Rails.logger.level = Logger::DEBUG
-
Choose a GitLab group to test with. This group should have an LDAP group link already configured. If the output is
nil
, the group could not be found. If a bunch of group attributes are output, your group was found successfully.group = Group.find_by(name: 'my_group') # Output => #<Group:0x007fe825196558 id: 1234, name: "my_group"...>
-
Run a group sync for this particular group.
EE::Gitlab::LDAP::Sync::Group.execute_all_providers(group)
Look through the output of the sync. See example log output below for more information about the output.
-
If you still aren't able to see why the user isn't being added, query the LDAP group directly to see what members are listed. Still in the Rails console, run the following query:
adapter = Gitlab::LDAP::Adapter.new('ldapmain') # If `main` is the LDAP provider ldap_group = EE::Gitlab::LDAP::Group.find_by_cn('group_cn_here', adapter) # Output => #<EE::Gitlab::LDAP::Group:0x007fcbdd0bb6d8
-
Query the LDAP group's member DNs and see if the user's DN is in the list. One of the DNs 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.
ldap_group.member_dns # Output => ["uid=john,ou=people,dc=example,dc=com", "uid=mary,ou=people,dc=example,dc=com"]
-
Some LDAP servers don't store members by DN. Rather, they use UIDs instead. If you didn't see results from the last query, try querying by UIDs instead.
ldap_group.member_uids # Output => ['john','mary']
Example log output
The output of the last command will be very verbose, but contains lots of helpful information. For the most part you can ignore log entries that are SQL statements.
Indicates the point where syncing actually begins:
Started syncing all providers for 'my_group' group
The follow entry shows an array of all user DNs GitLab sees in the LDAP server. Note that these are the users for a single LDAP group, not a GitLab group. If you have multiple LDAP groups linked to this GitLab group, you will 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.
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 will 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 'Master' and 50 is 'Owner'
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 has changed to update the user's LDAP identity.
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 once the user signs in for
the first time.
Finally, the following entry says syncing has finished for this group:
Finished syncing all providers for 'my_group' group
-
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://ctogonewild.com/2009/09/03/bitmask-searches-in-ldap/ for more information.↩