# MinIO AD/LDAP Integration [![Slack](https://slack.min.io/slack?type=svg)](https://slack.min.io)

MinIO provides a custom STS API that allows integration with LDAP
based corporate environments. The flow is as follows:

1. User provides their AD/LDAP username and password to the STS API.
2. MinIO logs-in to the AD/LDAP server as the user - if the login
   succeeds the user is authenticated.
3. MinIO then queries the AD/LDAP server for a list of groups that the
   user is a member of.
   - This is done via a customizable AD/LDAP search query.
4. MinIO then generates temporary credentials for the user storing the
   list of groups in a cryptographically secure session token. The
   temporary access key, secret key and session token are returned to
   the user.
5. The user can now use these credentials to make requests to the
   MinIO server.

The administrator will associate IAM access policies with each group
and if required with the user too. The MinIO server then evaluates
applicable policies on a user (these are the policies associated with
the groups along with the policy on the user if any) to check if the
request should be allowed or denied.

## Configuring AD/LDAP on MinIO

LDAP configuration is designed to be simple for the MinIO administrator.

The full path of a user DN (Distinguished Name)
(e.g. `uid=johnwick,cn=users,cn=accounts,dc=minio,dc=io`) is
configured as a format string in the
**MINIO_IDENTITY_LDAP_USERNAME_FORMAT** environment variable. This
allows an AD/LDAP user to not specify this whole string in the AD/LDAP STS
API. Instead the user only needs to specify the username portion
(i.e. `johnwick` in this example) that will be substituted into the
format string configured on the server.

MinIO can be configured to find the groups of a user from AD/LDAP by
specifying the **MINIO_IDENTITY_LDAP_GROUP_SEARCH_FILTER** and
**MINIO_IDENTITY_LDAP_GROUP_NAME_ATTRIBUTE** environment
variables. When a user logs in via the STS API, the MinIO server
queries the AD/LDAP server with the given search filter and extracts the
given attribute from the search results. These values represent the
groups that the user is a member of. On each access MinIO applies the
IAM policies attached to these groups in MinIO.

LDAP is configured via the following environment variables:

| Variable                                     | Required?                 | Purpose                                                |
|----------------------------------------------|---------------------------|--------------------------------------------------------|
| **MINIO_IDENTITY_LDAP_SERVER_ADDR**          | **YES**                   | AD/LDAP server address                                 |
| **MINIO_IDENTITY_LDAP_USERNAME_FORMAT**      | **YES**                   | Format of full username DN                             |
| **MINIO_IDENTITY_LDAP_GROUP_SEARCH_BASE_DN** | **NO**                    | Base DN in AD/LDAP hierarchy to use in search requests |
| **MINIO_IDENTITY_LDAP_GROUP_SEARCH_FILTER**  | **NO**                    | Search filter to find groups of a user                 |
| **MINIO_IDENTITY_LDAP_GROUP_NAME_ATTRIBUTE** | **NO**                    | Attribute of search results to use as group name       |
| **MINIO_IDENTITY_LDAP_STS_EXPIRY_DURATION**  | **NO** (default: "1h")    | STS credentials validity duration                      |
| **MINIO_IDENTITY_LDAP_TLS_SKIP_VERIFY**      | **NO** (default: "false") | Disable TLS certificate verification                   |

Please note that MinIO will only access the AD/LDAP server over TLS.

An example setup for development or experimentation:

``` shell
export MINIO_IDENTITY_LDAP_SERVER_ADDR=myldapserver.com:636
export MINIO_IDENTITY_LDAP_USERNAME_FORMAT="uid=${username},cn=accounts,dc=myldapserver,dc=com"
export MINIO_IDENTITY_LDAP_GROUP_SEARCH_BASE_DN="dc=myldapserver,dc=com"
export MINIO_IDENTITY_LDAP_GROUP_SEARCH_FILTER="(&(objectclass=groupOfNames)(member=${usernamedn}))"
export MINIO_IDENTITY_LDAP_GROUP_NAME_ATTRIBUTE="cn"
export MINIO_IDENTITY_LDAP_STS_EXPIRY_DURATION=60
export MINIO_IDENTITY_LDAP_TLS_SKIP_VERIFY=true
```

### Variable substitution in AD/LDAP configuration strings

In the configuration values described above, some values support
runtime substitutions. The substitution syntax is simply
`${variable}` - this substring is replaced with the (string) value of
`variable`. The following substitutions will be available:

| Variable     | Example Runtime Value                          | Description                                                                                                                                  |
|--------------|------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------|
| *username*   | "james"                                        | The AD/LDAP username of a user.                                                                                                                 |
| *usernamedn* | "uid=james,cn=accounts,dc=myldapserver,dc=com" | The AD/LDAP username DN of a user. This is constructed from the AD/LDAP user DN format string provided to the server and the actual AD/LDAP username. |

The **MINIO_IDENTITY_LDAP_USERNAME_FORMAT** environment variable
supports substitution of the *username* variable only.

The **MINIO_IDENTITY_LDAP_GROUP_SEARCH_FILTER** and
**MINIO_IDENTITY_LDAP_GROUP_SEARCH_BASE_DN** environment variables
support substitution of the *username* and *usernamedn* variables
only.

## Notes on configuring with Microsoft Active Directory (AD)

The LDAP STS API also works with Microsoft AD and can be configured
as above. The following are some notes on determining the values of
the configuration parameters described above.

Once LDAP over TLS is enabled on AD, test access to LDAP works by running a
sample search query with the `ldapsearch` utility from
[OpenLDAP](https://openldap.org/):

```shell
$ ldapsearch -H ldaps://my.ldap-active-dir-server.com -D "username@minioad.local" -x -w 'secretpassword' -b "dc=minioad,dc=local"
...

# John, Users, minioad.local
dn: CN=John,CN=Users,DC=minioad,DC=local
...

# hpc, Users, minioad.local
dn: CN=hpc,CN=Users,DC=minioad,DC=local
objectClass: top
objectClass: group
cn: hpc
...
member: CN=John,CN=Users,DC=minioad,DC=local
...
```

The lines with "..." represent skipped content not shown here from brevity.

Based on the output above, we see that the username format variable looks like
`cn=${username},cn=users,dc=minioad,dc=local`.

The group search filter looks like
`(&(objectclass=group)(member=${usernamedn}))` and the group name attribute is
clearly `cn`.

Thus the key configuration parameters look like:

```
MINIO_IDENTITY_LDAP_SERVER_ADDR='ldaps://my.ldap-active-dir-server.com:636'
MINIO_IDENTITY_LDAP_USERNAME_FORMAT='cn=${username},cn=users,dc=minioad,dc=local'
MINIO_IDENTITY_LDAP_GROUP_SEARCH_BASE_DN='dc=minioad,dc=local'
MINIO_IDENTITY_LDAP_GROUP_SEARCH_FILTER='(&(objectclass=group)(member=${usernamedn}))'
MINIO_IDENTITY_LDAP_GROUP_NAME_ATTRIBUTE='cn'
```
