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.
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.
Please note that MinIO will only access the AD/LDAP server over TLS. If a self-signed certificate is being used, the certificate can be added to MinIO's certificates directory, so it can be trusted by the server.
An example setup for development or experimentation:
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:
| *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_GROUP_SEARCH_FILTER** and **MINIO_IDENTITY_LDAP_GROUP_SEARCH_BASE_DN** environment variables support substitution of the *username* and *usernamedn* variables only.
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/):
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`.
Access policies may be configured on a group or on a user directly. Access policies are first defined on the MinIO server using IAM policy JSON syntax. The `mc` tool is used to issue the necessary commands.
**Note that by default no policy is set on a user**. Thus even if they successfully authenticate with AD/LDAP credentials, they have no access to object storage as the default access policy is to deny all access.
To define a new policy, you can use the [AWS policy generator](https://awspolicygen.s3.amazonaws.com/policygen.html). Copy the policy into a text file `mypolicy.json` and issue the command like so:
```sh
mc admin policy add myminio mypolicy mypolicy.json
```
To assign the policy to a user or group, use:
```sh
mc admin policy set myminio mypolicy user=james
```
```sh
mc admin policy set myminio mypolicy group=bigdatausers
```
**Please note that when AD/LDAP is configured, MinIO will not support long term users defined internally.** Only AD/LDAP users are allowed. In addition to this, the server will not support operations on users or groups using `mc admin user` or `mc admin group` commands except `mc admin user info` and `mc admin group info` to list set policies for users and groups. This is because users and groups are defined externally in AD/LDAP.
Is AD/LDAP username to login. Application must ask user for this value to successfully obtain rotating access credentials from AssumeRoleWithLDAPIdentity.
| Params | Value |
| :-- | :-- |
| *Type* | *String* |
| *Length Constraints* | *Minimum length of 2. Maximum length of 2048.* |
Is AD/LDAP username password to login. Application must ask user for this value to successfully obtain rotating access credentials from AssumeRoleWithLDAPIdentity.
| Params | Value |
| :-- | :-- |
| *Type* | *String* |
| *Length Constraints* | *Minimum length of 4. Maximum length of 2048.* |
Indicates STS API version information, the only supported value is '2011-06-15'. This value is borrowed from AWS STS API documentation for compatibility reasons.
An IAM policy in JSON format that you want to use as an inline session policy. This parameter is optional. Passing policies to this operation returns new temporary credentials. The resulting session's permissions are the intersection of the canned policy name and the policy set here. You cannot use this policy to grant more permissions than those allowed by the canned policy name being assumed.
| Params | Value |
| :-- | :-- |
| *Type* | *String* |
| *Valid Range* | *Minimum length of 1. Maximum length of 2048.* |
XML response for this API is similar to [AWS STS AssumeRoleWithWebIdentity](https://docs.aws.amazon.com/STS/latest/APIReference/API_AssumeRoleWithWebIdentity.html#API_AssumeRoleWithWebIdentity_ResponseElements)
XML error response for this API is similar to [AWS STS AssumeRoleWithWebIdentity](https://docs.aws.amazon.com/STS/latest/APIReference/API_AssumeRoleWithWebIdentity.html#API_AssumeRoleWithWebIdentity_Errors)
