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MinIO AD/LDAP Integration

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

User provides their AD/LDAP username and password to the STS API.
MinIO logs-in to the AD/LDAP server as the user - if the login succeeds the user is authenticated.
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.
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.
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:

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:

$ 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'

API Request Parameters

LDAPUsername

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.
Required	Yes

LDAPPassword

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.
Required	Yes

Version

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.

Params	Value
Type	String
Required	Yes

Policy

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.
Required	No

Response Elements

XML response for this API is similar to AWS STS AssumeRoleWithWebIdentity

Errors

XML error response for this API is similar to AWS STS AssumeRoleWithWebIdentity

Sample Request

http://minio.cluster:9000?Action=AssumeRoleWithLDAPIdentity&LDAPUsername=foouser&LDAPPassword=foouserpassword&Version=2011-06-15

Sample Response

<?xml version="1.0" encoding="UTF-8"?>
<AssumeRoleWithLDAPIdentityResponse xmlns="https://sts.amazonaws.com/doc/2011-06-15/">
  <AssumeRoleWithLDAPIdentityResult>
    <AssumedRoleUser>
      <Arn/>
      <AssumeRoleId/>
    </AssumedRoleUser>
    <Credentials>
      <AccessKeyId>Y4RJU1RNFGK48LGO9I2S</AccessKeyId>
      <SecretAccessKey>sYLRKS1Z7hSjluf6gEbb9066hnx315wHTiACPAjg</SecretAccessKey>
      <Expiration>2019-08-08T20:26:12Z</Expiration>
      <SessionToken>eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJhY2Nlc3NLZXkiOiJZNFJKVTFSTkZHSzQ4TEdPOUkyUyIsImF1ZCI6IlBvRWdYUDZ1Vk80NUlzRU5SbmdEWGo1QXU1WWEiLCJhenAiOiJQb0VnWFA2dVZPNDVJc0VOUm5nRFhqNUF1NVlhIiwiZXhwIjoxNTQxODExMDcxLCJpYXQiOjE1NDE4MDc0NzEsImlzcyI6Imh0dHBzOi8vbG9jYWxob3N0Ojk0NDMvb2F1dGgyL3Rva2VuIiwianRpIjoiYTBiMjc2MjktZWUxYS00M2JmLTg3MzktZjMzNzRhNGNkYmMwIn0.ewHqKVFTaP-j_kgZrcOEKroNUjk10GEp8bqQjxBbYVovV0nHO985VnRESFbcT6XMDDKHZiWqN2vi_ETX_u3Q-w</SessionToken>
    </Credentials>
  </AssumeRoleWithLDAPIdentity>
  <ResponseMetadata/>
</AssumeRoleWithLDAPIdentityResponse>

Testing

$ export MINIO_ACCESS_KEY=minio
$ export MINIO_SECRET_KEY=minio123
$ export MINIO_IDENTITY_LDAP_SERVER_ADDR='ldaps://my.ldap-active-dir-server.com:636'
$ export MINIO_IDENTITY_LDAP_USERNAME_FORMAT='cn=${username},cn=users,dc=minioad,dc=local'
$ export MINIO_IDENTITY_LDAP_GROUP_SEARCH_BASE_DN='dc=minioad,dc=local'
$ export MINIO_IDENTITY_LDAP_GROUP_SEARCH_FILTER='(&(objectclass=group)(member=${usernamedn}))'
$ export MINIO_IDENTITY_LDAP_GROUP_NAME_ATTRIBUTE='cn'
$ minio server ~/test

$ go run ldap.go -u foouser -p foopassword

##### Credentials
{
        "accessKey": "NUIBORZYTV2HG2BMRSXR",
        "secretKey": "qQlP5O7CFPc5m5IXf1vYhuVTFj7BRVJqh0FqZ86S",
        "expiration": "2018-08-21T17:10:29-07:00",
        "sessionToken": "eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJhY2Nlc3NLZXkiOiJOVUlCT1JaWVRWMkhHMkJNUlNYUiIsImF1ZCI6IlBvRWdYUDZ1Vk80NUlzRU5SbmdEWGo1QXU1WWEiLCJhenAiOiJQb0VnWFA2dVZPNDVJc0VOUm5nRFhqNUF1NVlhIiwiZXhwIjoxNTM0ODk2NjI5LCJpYXQiOjE1MzQ4OTMwMjksImlzcyI6Imh0dHBzOi8vbG9jYWxob3N0Ojk0NDMvb2F1dGgyL3Rva2VuIiwianRpIjoiNjY2OTZjZTctN2U1Ny00ZjU5LWI0MWQtM2E1YTMzZGZiNjA4In0.eJONnVaSVHypiXKEARSMnSKgr-2mlC2Sr4fEGJitLcJF_at3LeNdTHv0_oHsv6ZZA3zueVGgFlVXMlREgr9LXA"
}

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