aws_sts

AWS Security Token Service

The AWS Security Token Service (STS) is a web service that enables you to request temporary, limited-privilege credentials for AWS Identity and Access Management (IAM) users or for users that you authenticate (federated users). This guide provides descriptions of the STS API. For more detailed information about using this service, go to Temporary Security Credentials.

For information about setting up signatures and authorization through the API, go to Signing AWS API Requests in the AWS General Reference. For general information about the Query API, go to Making Query Requests in Using IAM. For information about using security tokens with other AWS products, go to AWS Services That Work with IAM in the IAM User Guide.

If you're new to AWS and need additional technical information about a specific AWS product, you can find the product's technical documentation at http://aws.amazon.com/documentation/.

Endpoints

By default, AWS Security Token Service (STS) is available as a global service, and all AWS STS requests go to a single endpoint at https://sts.amazonaws.com. Global requests map to the US East (N. Virginia) region. AWS recommends using Regional AWS STS endpoints instead of the global endpoint to reduce latency, build in redundancy, and increase session token validity. For more information, see Managing AWS STS in an AWS Region in the IAM User Guide.

Most AWS Regions are enabled for operations in all AWS services by default. Those Regions are automatically activated for use with AWS STS. Some Regions, such as Asia Pacific (Hong Kong), must be manually enabled. To learn more about enabling and disabling AWS Regions, see Managing AWS Regions in the AWS General Reference. When you enable these AWS Regions, they are automatically activated for use with AWS STS. You cannot activate the STS endpoint for a Region that is disabled. Tokens that are valid in all AWS Regions are longer than tokens that are valid in Regions that are enabled by default. Changing this setting might affect existing systems where you temporarily store tokens. For more information, see Managing Global Endpoint Session Tokens in the IAM User Guide.

After you activate a Region for use with AWS STS, you can direct AWS STS API calls to that Region. AWS STS recommends that you provide both the Region and endpoint when you make calls to a Regional endpoint. You can provide the Region alone for manually enabled Regions, such as Asia Pacific (Hong Kong). In this case, the calls are directed to the STS Regional endpoint. However, if you provide the Region alone for Regions enabled by default, the calls are directed to the global endpoint of https://sts.amazonaws.com.

To view the list of AWS STS endpoints and whether they are active by default, see Writing Code to Use AWS STS Regions in the IAM User Guide.

Recording API requests

STS supports AWS CloudTrail, which is a service that records AWS calls for your AWS account and delivers log files to an Amazon S3 bucket. By using information collected by CloudTrail, you can determine what requests were successfully made to STS, who made the request, when it was made, and so on.

If you activate AWS STS endpoints in Regions other than the default global endpoint, then you must also turn on CloudTrail logging in those Regions. This is necessary to record any AWS STS API calls that are made in those Regions. For more information, see Turning On CloudTrail in Additional Regions in the AWS CloudTrail User Guide.

AWS Security Token Service (STS) is a global service with a single endpoint at https://sts.amazonaws.com. Calls to this endpoint are logged as calls to a global service. However, because this endpoint is physically located in the US East (N. Virginia) Region, your logs list us-east-1 as the event Region. CloudTrail does not write these logs to the US East (Ohio) Region unless you choose to include global service logs in that Region. CloudTrail writes calls to all Regional endpoints to their respective Regions. For example, calls to sts.us-east-2.amazonaws.com are published to the US East (Ohio) Region and calls to sts.eu-central-1.amazonaws.com are published to the EU (Frankfurt) Region.

Summary

Functions

• assume_role(Client, Input)
  Returns a set of temporary security credentials that you can use to access AWS resources that you might not normally have access to.
• assume_role(Client, Input, Options)
• assume_role_with_s_a_m_l(Client, Input)
  Returns a set of temporary security credentials for users who have been authenticated via a SAML authentication response.
• assume_role_with_s_a_m_l(Client, Input, Options)
• assume_role_with_web_identity(Client, Input)
  Returns a set of temporary security credentials for users who have been authenticated in a mobile or web application with a web identity provider.
• assume_role_with_web_identity(Client, Input, Options)
• decode_authorization_message(Client, Input)
  Decodes additional information about the authorization status of a request from an encoded message returned in response to an AWS request.
• decode_authorization_message(Client, Input, Options)
• get_access_key_info(Client, Input)
  Returns the account identifier for the specified access key ID.
• get_access_key_info(Client, Input, Options)
• get_caller_identity(Client, Input)
  Returns details about the IAM user or role whose credentials are used to call the operation.
• get_caller_identity(Client, Input, Options)
• get_federation_token(Client, Input)
  Returns a set of temporary security credentials (consisting of an access key ID, a secret access key, and a security token) for a federated user.
• get_federation_token(Client, Input, Options)
• get_session_token(Client, Input)
  Returns a set of temporary credentials for an AWS account or IAM user.
• get_session_token(Client, Input, Options)

Functions

Returns a set of temporary security credentials that you can use to access AWS resources that you might not normally have access to. These temporary credentials consist of an access key ID, a secret access key, and a security token. Typically, you use AssumeRole within your account or for cross-account access. For a comparison of AssumeRole with other API operations that produce temporary credentials, see Requesting Temporary Security Credentials and Comparing the AWS STS API operations in the IAM User Guide.

You cannot use AWS account root user credentials to call AssumeRole. You must use credentials for an IAM user or an IAM role to call AssumeRole. For cross-account access, imagine that you own multiple accounts and need to access resources in each account. You could create long-term credentials in each account to access those resources. However, managing all those credentials and remembering which one can access which account can be time consuming. Instead, you can create one set of long-term credentials in one account. Then use temporary security credentials to access all the other accounts by assuming roles in those accounts. For more information about roles, see IAM Roles in the IAM User Guide.

Session Duration

By default, the temporary security credentials created by AssumeRole last for one hour. However, you can use the optional DurationSeconds parameter to specify the duration of your session. You can provide a value from 900 seconds (15 minutes) up to the maximum session duration setting for the role. This setting can have a value from 1 hour to 12 hours. To learn how to view the maximum value for your role, see View the Maximum Session Duration Setting for a Role in the IAM User Guide. The maximum session duration limit applies when you use the AssumeRole* API operations or the assume-role* CLI commands. However the limit does not apply when you use those operations to create a console URL. For more information, see Using IAM Roles in the IAM User Guide.

Permissions

The temporary security credentials created by AssumeRole can be used to make API calls to any AWS service with the following exception: You cannot call the AWS STS GetFederationToken or GetSessionToken API operations.

(Optional) You can pass inline or managed session policies to this operation. You can pass a single JSON policy document to use as an inline session policy. You can also specify up to 10 managed policies to use as managed session policies. The plain text that you use for both inline and managed session policies can't exceed 2,048 characters. Passing policies to this operation returns new temporary credentials. The resulting session's permissions are the intersection of the role's identity-based policy and the session policies. You can use the role's temporary credentials in subsequent AWS API calls to access resources in the account that owns the role. You cannot use session policies to grant more permissions than those allowed by the identity-based policy of the role that is being assumed. For more information, see Session Policies in the IAM User Guide.

To assume a role from a different account, your AWS account must be trusted by the role. The trust relationship is defined in the role's trust policy when the role is created. That trust policy states which accounts are allowed to delegate that access to users in the account.

A user who wants to access a role in a different account must also have permissions that are delegated from the user account administrator. The administrator must attach a policy that allows the user to call AssumeRole for the ARN of the role in the other account. If the user is in the same account as the role, then you can do either of the following:

• Attach a policy to the user (identical to the previous user in a different account).

• Add the user as a principal directly in the role's trust policy.

In this case, the trust policy acts as an IAM resource-based policy. Users in the same account as the role do not need explicit permission to assume the role. For more information about trust policies and resource-based policies, see IAM Policies in the IAM User Guide.

Tags

(Optional) You can pass tag key-value pairs to your session. These tags are called session tags. For more information about session tags, see Passing Session Tags in STS in the IAM User Guide.

An administrator must grant you the permissions necessary to pass session tags. The administrator can also create granular permissions to allow you to pass only specific session tags. For more information, see Tutorial: Using Tags for Attribute-Based Access Control in the IAM User Guide.

You can set the session tags as transitive. Transitive tags persist during role chaining. For more information, see Chaining Roles with Session Tags in the IAM User Guide.

Using MFA with AssumeRole

(Optional) You can include multi-factor authentication (MFA) information when you call AssumeRole. This is useful for cross-account scenarios to ensure that the user that assumes the role has been authenticated with an AWS MFA device. In that scenario, the trust policy of the role being assumed includes a condition that tests for MFA authentication. If the caller does not include valid MFA information, the request to assume the role is denied. The condition in a trust policy that tests for MFA authentication might look like the following example.

"Condition": {"Bool": {"aws:MultiFactorAuthPresent": true}}

For more information, see Configuring MFA-Protected API Access in the IAM User Guide guide.

Returns a set of temporary security credentials for users who have been authenticated via a SAML authentication response. This operation provides a mechanism for tying an enterprise identity store or directory to role-based AWS access without user-specific credentials or configuration. For a comparison of AssumeRoleWithSAML with the other API operations that produce temporary credentials, see Requesting Temporary Security Credentials and Comparing the AWS STS API operations in the IAM User Guide.

The temporary security credentials returned by this operation consist of an access key ID, a secret access key, and a security token. Applications can use these temporary security credentials to sign calls to AWS services.

Session Duration

By default, the temporary security credentials created by AssumeRoleWithSAML last for one hour. However, you can use the optional DurationSeconds parameter to specify the duration of your session. Your role session lasts for the duration that you specify, or until the time specified in the SAML authentication response's SessionNotOnOrAfter value, whichever is shorter. You can provide a DurationSeconds value from 900 seconds (15 minutes) up to the maximum session duration setting for the role. This setting can have a value from 1 hour to 12 hours. To learn how to view the maximum value for your role, see View the Maximum Session Duration Setting for a Role in the IAM User Guide. The maximum session duration limit applies when you use the AssumeRole* API operations or the assume-role* CLI commands. However the limit does not apply when you use those operations to create a console URL. For more information, see Using IAM Roles in the IAM User Guide.

Permissions

The temporary security credentials created by AssumeRoleWithSAML can be used to make API calls to any AWS service with the following exception: you cannot call the STS GetFederationToken or GetSessionToken API operations.

(Optional) You can pass inline or managed session policies to this operation. You can pass a single JSON policy document to use as an inline session policy. You can also specify up to 10 managed policies to use as managed session policies. The plain text that you use for both inline and managed session policies can't exceed 2,048 characters. Passing policies to this operation returns new temporary credentials. The resulting session's permissions are the intersection of the role's identity-based policy and the session policies. You can use the role's temporary credentials in subsequent AWS API calls to access resources in the account that owns the role. You cannot use session policies to grant more permissions than those allowed by the identity-based policy of the role that is being assumed. For more information, see Session Policies in the IAM User Guide.

Calling AssumeRoleWithSAML does not require the use of AWS security credentials. The identity of the caller is validated by using keys in the metadata document that is uploaded for the SAML provider entity for your identity provider.

Calling AssumeRoleWithSAML can result in an entry in your AWS CloudTrail logs. The entry includes the value in the NameID element of the SAML assertion. We recommend that you use a NameIDType that is not associated with any personally identifiable information (PII). For example, you could instead use the persistent identifier (urn:oasis:names:tc:SAML:2.0:nameid-format:persistent). Tags

(Optional) You can configure your IdP to pass attributes into your SAML assertion as session tags. Each session tag consists of a key name and an associated value. For more information about session tags, see Passing Session Tags in STS in the IAM User Guide.

You can pass up to 50 session tags. The plain text session tag keys can’t exceed 128 characters and the values can’t exceed 256 characters. For these and additional limits, see IAM and STS Character Limits in the IAM User Guide.

An AWS conversion compresses the passed session policies and session tags into a packed binary format that has a separate limit. Your request can fail for this limit even if your plain text meets the other requirements. The PackedPolicySize response element indicates by percentage how close the policies and tags for your request are to the upper size limit. You can pass a session tag with the same key as a tag that is attached to the role. When you do, session tags override the role's tags with the same key.

An administrator must grant you the permissions necessary to pass session tags. The administrator can also create granular permissions to allow you to pass only specific session tags. For more information, see Tutorial: Using Tags for Attribute-Based Access Control in the IAM User Guide.

You can set the session tags as transitive. Transitive tags persist during role chaining. For more information, see Chaining Roles with Session Tags in the IAM User Guide.

SAML Configuration

Before your application can call AssumeRoleWithSAML, you must configure your SAML identity provider (IdP) to issue the claims required by AWS. Additionally, you must use AWS Identity and Access Management (IAM) to create a SAML provider entity in your AWS account that represents your identity provider. You must also create an IAM role that specifies this SAML provider in its trust policy.

For more information, see the following resources:

• About SAML 2.0-based Federation in the IAM User Guide.

• Creating SAML Identity Providers in the IAM User Guide.

• Configuring a Relying Party and Claims in the IAM User Guide.

• Creating a Role for SAML 2.0 Federation in the IAM User Guide.

Returns a set of temporary security credentials for users who have been authenticated in a mobile or web application with a web identity provider. Example providers include Amazon Cognito, Login with Amazon, Facebook, Google, or any OpenID Connect-compatible identity provider.

For mobile applications, we recommend that you use Amazon Cognito. You can use Amazon Cognito with the AWS SDK for iOS Developer Guide and the AWS SDK for Android Developer Guide to uniquely identify a user. You can also supply the user with a consistent identity throughout the lifetime of an application. To learn more about Amazon Cognito, see Amazon Cognito Overview in AWS SDK for Android Developer Guide and Amazon Cognito Overview in the AWS SDK for iOS Developer Guide. Calling AssumeRoleWithWebIdentity does not require the use of AWS security credentials. Therefore, you can distribute an application (for example, on mobile devices) that requests temporary security credentials without including long-term AWS credentials in the application. You also don't need to deploy server-based proxy services that use long-term AWS credentials. Instead, the identity of the caller is validated by using a token from the web identity provider. For a comparison of AssumeRoleWithWebIdentity with the other API operations that produce temporary credentials, see Requesting Temporary Security Credentials and Comparing the AWS STS API operations in the IAM User Guide.

The temporary security credentials returned by this API consist of an access key ID, a secret access key, and a security token. Applications can use these temporary security credentials to sign calls to AWS service API operations.

Session Duration

By default, the temporary security credentials created by AssumeRoleWithWebIdentity last for one hour. However, you can use the optional DurationSeconds parameter to specify the duration of your session. You can provide a value from 900 seconds (15 minutes) up to the maximum session duration setting for the role. This setting can have a value from 1 hour to 12 hours. To learn how to view the maximum value for your role, see View the Maximum Session Duration Setting for a Role in the IAM User Guide. The maximum session duration limit applies when you use the AssumeRole* API operations or the assume-role* CLI commands. However the limit does not apply when you use those operations to create a console URL. For more information, see Using IAM Roles in the IAM User Guide.

Permissions

The temporary security credentials created by AssumeRoleWithWebIdentity can be used to make API calls to any AWS service with the following exception: you cannot call the STS GetFederationToken or GetSessionToken API operations.

(Optional) You can pass inline or managed session policies to this operation. You can pass a single JSON policy document to use as an inline session policy. You can also specify up to 10 managed policies to use as managed session policies. The plain text that you use for both inline and managed session policies can't exceed 2,048 characters. Passing policies to this operation returns new temporary credentials. The resulting session's permissions are the intersection of the role's identity-based policy and the session policies. You can use the role's temporary credentials in subsequent AWS API calls to access resources in the account that owns the role. You cannot use session policies to grant more permissions than those allowed by the identity-based policy of the role that is being assumed. For more information, see Session Policies in the IAM User Guide.

Tags

(Optional) You can configure your IdP to pass attributes into your web identity token as session tags. Each session tag consists of a key name and an associated value. For more information about session tags, see Passing Session Tags in STS in the IAM User Guide.

You can pass up to 50 session tags. The plain text session tag keys can’t exceed 128 characters and the values can’t exceed 256 characters. For these and additional limits, see IAM and STS Character Limits in the IAM User Guide.

An AWS conversion compresses the passed session policies and session tags into a packed binary format that has a separate limit. Your request can fail for this limit even if your plain text meets the other requirements. The PackedPolicySize response element indicates by percentage how close the policies and tags for your request are to the upper size limit. You can pass a session tag with the same key as a tag that is attached to the role. When you do, the session tag overrides the role tag with the same key.

An administrator must grant you the permissions necessary to pass session tags. The administrator can also create granular permissions to allow you to pass only specific session tags. For more information, see Tutorial: Using Tags for Attribute-Based Access Control in the IAM User Guide.

You can set the session tags as transitive. Transitive tags persist during role chaining. For more information, see Chaining Roles with Session Tags in the IAM User Guide.

Identities

Before your application can call AssumeRoleWithWebIdentity, you must have an identity token from a supported identity provider and create a role that the application can assume. The role that your application assumes must trust the identity provider that is associated with the identity token. In other words, the identity provider must be specified in the role's trust policy.

Calling AssumeRoleWithWebIdentity can result in an entry in your AWS CloudTrail logs. The entry includes the Subject of the provided Web Identity Token. We recommend that you avoid using any personally identifiable information (PII) in this field. For example, you could instead use a GUID or a pairwise identifier, as suggested in the OIDC specification. For more information about how to use web identity federation and the AssumeRoleWithWebIdentity API, see the following resources:

• Using Web Identity Federation API Operations for Mobile Apps and Federation Through a Web-based Identity Provider.

• Web Identity Federation Playground. Walk through the process of authenticating through Login with Amazon, Facebook, or Google, getting temporary security credentials, and then using those credentials to make a request to AWS.

• AWS SDK for iOS Developer Guide and AWS SDK for Android Developer Guide. These toolkits contain sample apps that show how to invoke the identity providers. The toolkits then show how to use the information from these providers to get and use temporary security credentials.

• Web Identity Federation with Mobile Applications. This article discusses web identity federation and shows an example of how to use web identity federation to get access to content in Amazon S3.

Decodes additional information about the authorization status of a request from an encoded message returned in response to an AWS request.

For example, if a user is not authorized to perform an operation that he or she has requested, the request returns a Client.UnauthorizedOperation response (an HTTP 403 response). Some AWS operations additionally return an encoded message that can provide details about this authorization failure.

Only certain AWS operations return an encoded authorization message. The documentation for an individual operation indicates whether that operation returns an encoded message in addition to returning an HTTP code. The message is encoded because the details of the authorization status can constitute privileged information that the user who requested the operation should not see. To decode an authorization status message, a user must be granted permissions via an IAM policy to request the DecodeAuthorizationMessage (sts:DecodeAuthorizationMessage) action.

The decoded message includes the following type of information:

• Whether the request was denied due to an explicit deny or due to the absence of an explicit allow. For more information, see Determining Whether a Request is Allowed or Denied in the IAM User Guide.

• The principal who made the request.

• The requested action.

• The requested resource.

• The values of condition keys in the context of the user's request.

Returns the account identifier for the specified access key ID.

Access keys consist of two parts: an access key ID (for example, AKIAIOSFODNN7EXAMPLE) and a secret access key (for example, wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY). For more information about access keys, see Managing Access Keys for IAM Users in the IAM User Guide.

When you pass an access key ID to this operation, it returns the ID of the AWS account to which the keys belong. Access key IDs beginning with AKIA are long-term credentials for an IAM user or the AWS account root user. Access key IDs beginning with ASIA are temporary credentials that are created using STS operations. If the account in the response belongs to you, you can sign in as the root user and review your root user access keys. Then, you can pull a credentials report to learn which IAM user owns the keys. To learn who requested the temporary credentials for an ASIA access key, view the STS events in your CloudTrail logs in the IAM User Guide.

Returns details about the IAM user or role whose credentials are used to call the operation.

Returns a set of temporary security credentials (consisting of an access key ID, a secret access key, and a security token) for a federated user. A typical use is in a proxy application that gets temporary security credentials on behalf of distributed applications inside a corporate network. You must call the GetFederationToken operation using the long-term security credentials of an IAM user. As a result, this call is appropriate in contexts where those credentials can be safely stored, usually in a server-based application. For a comparison of GetFederationToken with the other API operations that produce temporary credentials, see Requesting Temporary Security Credentials and Comparing the AWS STS API operations in the IAM User Guide.

You can create a mobile-based or browser-based app that can authenticate users using a web identity provider like Login with Amazon, Facebook, Google, or an OpenID Connect-compatible identity provider. In this case, we recommend that you use Amazon Cognito or AssumeRoleWithWebIdentity. For more information, see Federation Through a Web-based Identity Provider in the IAM User Guide. You can also call GetFederationToken using the security credentials of an AWS account root user, but we do not recommend it. Instead, we recommend that you create an IAM user for the purpose of the proxy application. Then attach a policy to the IAM user that limits federated users to only the actions and resources that they need to access. For more information, see IAM Best Practices in the IAM User Guide.

Session duration

The temporary credentials are valid for the specified duration, from 900 seconds (15 minutes) up to a maximum of 129,600 seconds (36 hours). The default session duration is 43,200 seconds (12 hours). Temporary credentials that are obtained by using AWS account root user credentials have a maximum duration of 3,600 seconds (1 hour).

Permissions

You can use the temporary credentials created by GetFederationToken in any AWS service except the following:

• You cannot call any IAM operations using the AWS CLI or the AWS API.

• You cannot call any STS operations except GetCallerIdentity.

You must pass an inline or managed session policy to this operation. You can pass a single JSON policy document to use as an inline session policy. You can also specify up to 10 managed policies to use as managed session policies. The plain text that you use for both inline and managed session policies can't exceed 2,048 characters.

Though the session policy parameters are optional, if you do not pass a policy, then the resulting federated user session has no permissions. When you pass session policies, the session permissions are the intersection of the IAM user policies and the session policies that you pass. This gives you a way to further restrict the permissions for a federated user. You cannot use session policies to grant more permissions than those that are defined in the permissions policy of the IAM user. For more information, see Session Policies in the IAM User Guide. For information about using GetFederationToken to create temporary security credentials, see GetFederationToken—Federation Through a Custom Identity Broker.

You can use the credentials to access a resource that has a resource-based policy. If that policy specifically references the federated user session in the Principal element of the policy, the session has the permissions allowed by the policy. These permissions are granted in addition to the permissions granted by the session policies.

Tags

(Optional) You can pass tag key-value pairs to your session. These are called session tags. For more information about session tags, see Passing Session Tags in STS in the IAM User Guide.

An administrator must grant you the permissions necessary to pass session tags. The administrator can also create granular permissions to allow you to pass only specific session tags. For more information, see Tutorial: Using Tags for Attribute-Based Access Control in the IAM User Guide.

Returns a set of temporary credentials for an AWS account or IAM user. The credentials consist of an access key ID, a secret access key, and a security token. Typically, you use GetSessionToken if you want to use MFA to protect programmatic calls to specific AWS API operations like Amazon EC2 StopInstances. MFA-enabled IAM users would need to call GetSessionToken and submit an MFA code that is associated with their MFA device. Using the temporary security credentials that are returned from the call, IAM users can then make programmatic calls to API operations that require MFA authentication. If you do not supply a correct MFA code, then the API returns an access denied error. For a comparison of GetSessionToken with the other API operations that produce temporary credentials, see Requesting Temporary Security Credentials and Comparing the AWS STS API operations in the IAM User Guide.

Session Duration

The GetSessionToken operation must be called by using the long-term AWS security credentials of the AWS account root user or an IAM user. Credentials that are created by IAM users are valid for the duration that you specify. This duration can range from 900 seconds (15 minutes) up to a maximum of 129,600 seconds (36 hours), with a default of 43,200 seconds (12 hours). Credentials based on account credentials can range from 900 seconds (15 minutes) up to 3,600 seconds (1 hour), with a default of 1 hour.

Permissions

The temporary security credentials created by GetSessionToken can be used to make API calls to any AWS service with the following exceptions:

• You cannot call any IAM API operations unless MFA authentication information is included in the request.

• You cannot call any STS API except AssumeRole or GetCallerIdentity.

We recommend that you do not call GetSessionToken with AWS account root user credentials. Instead, follow our best practices by creating one or more IAM users, giving them the necessary permissions, and using IAM users for everyday interaction with AWS. The credentials that are returned by GetSessionToken are based on permissions associated with the user whose credentials were used to call the operation. If GetSessionToken is called using AWS account root user credentials, the temporary credentials have root user permissions. Similarly, if GetSessionToken is called using the credentials of an IAM user, the temporary credentials have the same permissions as the IAM user.