HumHub Documentation (unofficial)

Permissions

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

(Optional) You can pass inline or managed session policies ^3 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 policy Amazon Resource Names (ARNs) to use as managed session policies. The plaintext 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 Amazon Web Services 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 ^4 in the IAM User Guide.

When you create a role, you create two policies: a role trust policy that specifies who can assume the role, and a permissions policy that specifies what can be done with the role. You specify the trusted principal that is allowed to assume the role in the role trust policy.

To assume a role from a different account, your Amazon Web Services 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 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.

To allow a user to assume a role in the same account, you can do either of the following:

• Attach a policy to the user that allows the user to call AssumeRole (as long as the role's trust policy trusts the account).
• Add the user as a principal directly in the role's trust policy.

You can do either because the role’s trust policy acts as an IAM resource-based policy. When a resource-based policy grants access to a principal in the same account, no additional identity-based policy is required. For more information about trust policies and resource-based policies, see IAM Policies ^5 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 ^6 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 ^7 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 ^8 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 Amazon Web Services 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 ^9 in the IAM User Guide guide.

To use MFA with AssumeRole, you pass values for the SerialNumber and TokenCode parameters. The SerialNumber value identifies the user's hardware or virtual MFA device. The TokenCode is the time-based one-time password (TOTP) that the MFA device produces.

For mobile applications, we recommend that you use Amazon Cognito. You can use Amazon Cognito with the Amazon Web Services SDK for iOS Developer Guide ^2 and the Amazon Web Services SDK for Android Developer Guide ^3 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 identity pools ^4 in Amazon Cognito Developer Guide.

Calling AssumeRoleWithWebIdentity does not require the use of Amazon Web Services security credentials. Therefore, you can distribute an application (for example, on mobile devices) that requests temporary security credentials without including long-term Amazon Web Services credentials in the application. You also don't need to deploy server-based proxy services that use long-term Amazon Web Services 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 ^5 and Comparing the Amazon Web Services STS API operations ^6 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 Amazon Web Services 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 ^7 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 ^8 in the IAM User Guide.

Permissions

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

(Optional) You can pass inline or managed session policies ^9 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 policy Amazon Resource Names (ARNs) to use as managed session policies. The plaintext 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 Amazon Web Services 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 ^10 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 ^11 in the IAM User Guide.

You can pass up to 50 session tags. The plaintext 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 ^12 in the IAM User Guide.

An Amazon Web Services conversion compresses the passed inline session policy, managed policy ARNs, and session tags into a packed binary format that has a separate limit. Your request can fail for this limit even if your plaintext 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 ^13 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 ^14 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 CloudTrail logs. The entry includes the Subject ! ^15 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 ^16.

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 ^17 and Federation Through a Web-based Identity Provider ^18.
• Web Identity Federation Playground ^19. 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 Amazon Web Services.
• Amazon Web Services SDK for iOS Developer Guide ^20 and Amazon Web Services SDK for Android Developer Guide ^21. 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 ^22. 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.

No permissions are required to perform this operation. If an administrator attaches a policy to your identity that explicitly denies access to the sts:GetCallerIdentity action, you can still perform this operation. Permissions are not required because the same information is returned when access is denied. To view an example response, see I Am Not Authorized to Perform: iam:DeleteVirtualMFADevice ^1 in the IAM User Guide.