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AssumeRoleWithWebIdentity

Introduction

Calling AssumeRoleWithWebIdentity does not require the use of MinIO default credentials. Therefore, you can distribute an application (for example, on mobile devices) that requests temporary security credentials without including MinIO default credentials in the application. Instead, the identity of the caller is validated by using a JWT id_token from the web identity provider. The temporary security credentials returned by this API consists of an access key, a secret key, and a security token. Applications can use these temporary security credentials to sign calls to MinIO API operations.

By default, the temporary security credentials created by AssumeRoleWithWebIdentity last for one hour. However, use the optional DurationSeconds parameter to specify the duration of the credentials. This value varies from 900 seconds (15 minutes) up to the maximum session duration of 365 days.

Access Control Policies

MinIO's AssumeRoleWithWebIdentity supports specifying access control policies in two ways:

Role Policy (Recommended): When specified, all users authenticating via this API are authorized to (only) use the specified role policy. The policy to associate with such users is specified when configuring OpenID provider in the server, via the role_policy configuration parameter or the MINIO_IDENTITY_OPENID_ROLE_POLICY environment variable. The value is a comma-separated list of IAM access policy names already defined in the server. In this situation, the server prints a role ARN at startup that must be specified as a RoleARN API request parameter in the STS AssumeRoleWithWebIdentity API call.
id_token claims: When the role policy is not configured, MinIO looks for a specific claim in the id_token (JWT) returned by the OpenID provider. The default claim is policy and can be overridden by the claim_name configuration parameter or the MINIO_IDENTITY_OPENID_CLAIM_NAME environment variable. The claim value can be a string (comma-separated list) or an array of IAM access policy names defined in the server. A RoleARN API request parameter must not be specified in the STS AssumeRoleWithWebIdentity API call.

API Request Parameters

WebIdentityToken

The OAuth 2.0 id_token that is provided by the web identity provider. Application must get this token by authenticating the user who is using your application with a web identity provider before the application makes an AssumeRoleWithWebIdentity call.

Params	Value
Type	String
Length Constraints	Minimum length of 4. Maximum length of 2048.
Required	Yes

WebIdentityAccessToken (MinIO Extension)

There are situations when identity provider does not provide user claims in id_token instead it needs to be retrieved from UserInfo endpoint, this extension is only useful in this scenario. This is rare so use it accordingly depending on your Identity provider implementation. access_token is available as part of the OIDC authentication flow similar to id_token.

Params	Value
Type	String
Required	No

RoleARN

The role ARN to use. This must be specified if and only if the web identity provider is configured with a role policy.

Params	Value
Type	String
Required	No

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

DurationSeconds

The duration, in seconds. The value can range from 900 seconds (15 minutes) up to 365 days. If value is higher than this setting, then operation fails. By default, the value is set to 3600 seconds. If no DurationSeconds is specified expiry seconds is obtained from WebIdentityToken.

Params	Value
Type	Integer
Valid Range	Minimum value of 900. Maximum value of 31536000.
Required	No

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 `POST` Request

http://minio.cluster:9000?Action=AssumeRoleWithWebIdentity&DurationSeconds=3600&WebIdentityToken=eyJ4NXQiOiJOVEF4Wm1NeE5ETXlaRGczTVRVMVpHTTBNekV6T0RKaFpXSTRORE5sWkRVMU9HRmtOakZpTVEiLCJraWQiOiJOVEF4Wm1NeE5ETXlaRGczTVRVMVpHTTBNekV6T0RKaFpXSTRORE5sWkRVMU9HRmtOakZpTVEiLCJhbGciOiJSUzI1NiJ9.eyJhdWQiOiJQb0VnWFA2dVZPNDVJc0VOUm5nRFhqNUF1NVlhIiwiYXpwIjoiUG9FZ1hQNnVWTzQ1SXNFTlJuZ0RYajVBdTVZYSIsImlzcyI6Imh0dHBzOlwvXC9sb2NhbGhvc3Q6OTQ0M1wvb2F1dGgyXC90b2tlbiIsImV4cCI6MTU0MTgwOTU4MiwiaWF0IjoxNTQxODA1OTgyLCJqdGkiOiI2Y2YyMGIwZS1lNGZmLTQzZmQtYTdiYS1kYTc3YTE3YzM2MzYifQ.Jm29jPliRvrK6Os34nSK3rhzIYLFjE__zdVGNng3uGKXGKzP3We_i6NPnhA0szJXMOKglXzUF1UgSz8MctbaxFS8XDusQPVe4LkB_45hwBm6TmBxzui911nt-1RbBLN_jZIlvl2lPrbTUH5hSn9kEkph6seWanTNQpz9tNEoVa6R_OX3kpJqxe8tLQUWw453A1JTwFNhdHa6-f1K8_Q_eEZ_4gOYINQ9t_fhTibdbkXZkJQFLop-Jwoybi9s4nwQU_dATocgcufq5eCeNItQeleT-23lGxIz0X7CiJrJynYLdd-ER0F77SumqEb5iCxhxuf4H7dovwd1kAmyKzLxpw&Version=2011-06-15

Sample Response

<?xml version="1.0" encoding="UTF-8"?>
<AssumeRoleWithWebIdentityResponse xmlns="https://sts.amazonaws.com/doc/2011-06-15/">
  <AssumeRoleWithWebIdentityResult>
    <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>
  </AssumeRoleWithWebIdentityResult>
  <ResponseMetadata/>
</AssumeRoleWithWebIdentityResponse>

Using WebIdentity API

export MINIO_ROOT_USER=minio
export MINIO_ROOT_PASSWORD=minio123
export MINIO_IDENTITY_OPENID_CONFIG_URL=https://accounts.google.com/.well-known/openid-configuration
export MINIO_IDENTITY_OPENID_CLIENT_ID="843351d4-1080-11ea-aa20-271ecba3924a"
# Optional: Allow to specify the requested OpenID scopes (OpenID only requires the `openid` scope)
#export MINIO_IDENTITY_OPENID_SCOPES="openid,profile,email"
minio server /mnt/export

or using mc

mc admin config get myminio identity_openid
identity_openid config_url=https://accounts.google.com/.well-known/openid-configuration client_id=843351d4-1080-11ea-aa20-271ecba3924a

Testing with an example

Visit Google Developer Console under Project, APIs, Credentials to get your OAuth2 client credentials. Add http://localhost:8080/oauth2/callback as a valid OAuth2 Redirect URL.

$ go run web-identity.go -cid 204367807228-ok7601k6gj1pgge7m09h7d79co8p35xx.apps.googleusercontent.com -csec XsT_PgPdT1nO9DD45rMLJw7G
2018/12/26 17:49:36 listening on http://localhost:8080/

NOTE: for a reasonable test outcome, make sure the assumed user has at least permission/policy to list all buckets. That policy would look like below:

{
  "version": "2012-10-17",
  "statement": [
    {
      "effect": "Allow",
      "action": [
        "s3:ListAllMyBuckets"
      ],
      "resource": [
        "arn:aws:s3:::*"
      ]
    }
  ]
}

Authorization Flow

Visit http://localhost:8080, login will direct the user to the Google OAuth2 Auth URL to obtain a permission grant.
The redirection URI (callback handler) receives the OAuth2 callback, verifies the state parameter, and obtains a Token.
Using the id_token the callback handler further talks to Google OAuth2 Token URL to obtain an JWT id_token.
Once obtained the JWT id_token is further sent to STS endpoint i.e MinIO to retrieve temporary credentials.
Temporary credentials are displayed on the browser upon successful retrieval.

Using MinIO Console

To support WebIdentity based login for MinIO Console, set openid configuration and restart MinIO

mc admin config set myminio identity_openid config_url="<CONFIG_URL>" client_id="<client_identifier>"

mc admin service restart myminio

Sample URLs for Keycloak are

config_url - http://localhost:8080/auth/realms/demo/.well-known/openid-configuration

JWT token returned by the Identity Provider should include a custom claim for the policy, this is required to create a STS user in MinIO. The name of the custom claim could be either policy or <NAMESPACE_PREFIX>policy. If there is no namespace then claim_prefix can be ingored. For example if the custom claim name is https://min.io/policy then, claim_prefix should be set as https://min.io/.

Open MinIO Console and click Login with SSO
The user will be redirected to the Identity Provider login page
Upon successful login on Identity Provider page the user will be automatically logged into MinIO Console.

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