STS Identity Policy-based Authorization Reference

IAM provides system-defined identity policies to define typical cloud service permissions. You can also create custom identity policies using the actions supported by cloud services for more refined access control.

In addition to IAM, the Organizations service also provides Service Control Policies (SCPs) to set access control policies.

SCPs do not actually grant any permissions to an entity. They only set the permissions boundary for the entity. When SCPs are attached to an organizational unit (OU) or a member account, the SCPs do not directly grant permissions to that OU or member account. Instead, the SCPs only determine what permissions are available for that member account or those member accounts under that OU. The granted permissions can be applied only if they are allowed by the SCPs.

To learn more about how IAM is different from Organizations for access control, see How IAM Is Different from Organizations for Access Control?.

This section describes the elements used by IAM custom identity policies and Organizations SCPs. The elements include actions, resources, and conditions.

For details about how to use these elements to edit an IAM custom identity policy, see Creating a Custom Identity Policy.
For details about how to use these elements to edit a custom SCP, see Creating an SCP.

Actions

Actions are specific operations that are allowed or denied in an identity policy.

The Access Level column describes how the action is classified (List, Read, or Write). This classification helps you understand the level of access that an action grants when you use it in an identity policy.
The Resource Type column indicates whether the action supports resource-level permissions.
- You can use a wildcard (*) to indicate all resource types. If this column is empty (-), the action does not support resource-level permissions and you must specify all resources ("*") in your identity policy statements.
- If this column includes a resource type, you must specify the URN in the Resource element of your identity policy statements.
- Required resources are marked with asterisks (*) in the table. If you specify a resource in a statement using this action, then it must be of this type.
For details about the resource types defined by STS, see Resources.
The Condition Key column contains keys that you can specify in the Condition element of an identity policy statement.
- If the Resource Type column has values for an action, the condition key takes effect only for the listed resource types.
- If the Resource Type column is empty (-) for an action, the condition key takes effect for all resources that action supports.
- If the Condition Key column is empty (-) for an action, the action does not support any condition keys.
For details about the condition keys defined by STS, see Conditions.
The Alias column lists the policy actions that are configured in identity policies. With these actions, you can use APIs for policy-based authorization. For details, see Policies and Identity Policies.

The following table lists the actions that you can define in identity policy statements for STS.

**Table 1** Actions supported by STS
Action	Description	Access Level	Resource Type (*: required)	Condition Key	Alias
sts:agencies:assume	Grants permission to obtain a set of temporary credentials that you can use to access resources that you might not normally have access to.	Write	agency *	g:ResourceTag/<tag-key>	-
sts:agencies:assume		Write	-	sts:ExternalId sts:SourceIdentity sts:TransitiveTagKeys sts:AgencySessionName g:RequestTag/<tag-key> g:TagKeys g:SourceAccount g:SourceUrn	-
sts::decodeAuthorizationMessage	Grants permission to decode additional information about the authorization status of a request from an encoded message returned in response to a request.	Write	-	-	-
sts::setSourceIdentity	Grants permission to set a source identity on a STS session.	Write	agency *	g:ResourceTag/<tag-key>	-
sts::setSourceIdentity		Write	-	sts:SourceIdentity	-
sts::tagSession	Grants permission to add tags to a STS session.	Tagging	agency *	g:ResourceTag/<tag-key>	-
sts::tagSession	Grants permission to add tags to a STS session.	Tagging	-	sts:TransitiveTagKeys g:RequestTag/<tag-key> g:TagKeys	-
sts::createServiceBearerToken	Grants permission to get the service bearer token.	Write	-	sts:DurationTime sts:ServiceName	-

Each API of STS usually supports one or more actions. Table 2 lists the supported actions and dependencies.

**Table 2** Actions and dependencies supported by STS APIs
API	Action	Dependencies
POST /v5/agencies/assume	sts:agencies:assume	sts::tagSession sts::setSourceIdentity
POST /v5/decode-authorization-message	sts::decodeAuthorizationMessage	-

Resources

A resource type indicates the resources that an identity policy applies to. If you specify a resource type for any action in Table 3, the resource URN must be specified in the identity policy statements using that action, and the identity policy applies only to resources of this type. If no resource type is specified, the Resource element is marked with an asterisk (*) and the identity policy applies to all resources. You can also set condition keys in an identity policy to define resource types.

The following table lists the resource types that you can define in identity policy statements for STS.

**Table 3** Resource types supported by STS
Resource Type	URN
agency	iam::<account-id>:agency:<agency-name-with-path>
assumed-agency	sts::<account-id>:assumed-agency:<agency-name>/<session-name>

Conditions

Condition Key Overview

A Condition element lets you specify conditions for when an identity policy is in effect. It contains condition keys and operators.

The condition key that you specify can be a global condition key or a service-specific condition key.
- Global condition keys (with the g: prefix) apply to all actions. Cloud services do not need to provide user identity information. Instead, the system automatically obtains such information and authenticates users. For details, see Global Condition Keys.
- Service-specific condition keys (with the abbreviation of a service name plus a colon as the prefix, for example, sts) apply only to operations of the xx service. For details, see Table 4.
- The number of values associated with a condition key in the request context of an API call makes the condition key single-valued or multivalued. Single-valued condition keys have at most one value in the request context of an API call. Multivalued condition keys can have multiple values in the request context of an API call. For example, a request can originate from at most one VPC endpoint, so g:SourceVpce is a single-valued condition key. You can tag resources and include multiple tag key-value pairs in a request, so g:TagKeys is a multivalued condition key.
A condition operator, condition key, and a condition value together constitute a complete condition statement. An identity policy can be applied only when its request conditions are met. For supported condition operators, see operators.

Service-specific condition keys supported by STS

The following table lists the condition keys that you can define in identity policies for STS. You can include these condition keys to specify conditions for when your identity policy is in effect.

**Table 4** Service-specific condition keys supported by STS
Service-specific Condition Key	Type	Single-valued/Multivalued	Description
sts:ExternalId	string	Single-valued	Filters access by the external ID that is passed in the request.
sts:SourceIdentity	string	Single-valued	Filters access by the source identity that is passed in the request.
sts:TransitiveTagKeys	string	Multivalued	Filters access by the transitive tag keys that are passed in the request.
sts:AgencySessionName	string	Single-valued	Filters access by the agency session name required when you assume an agency.
sts:DurationTime	numeric	Single-valued	Filters access by the duration times when you create a bearer token.
sts:ServiceName	string	Single-valued	Filters access by the service name when you create a bearer token.