AWS SDK Version 3 for .NET
API Reference

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Returns a set of temporary security credentials for users who have been authenticated in a mobile or web application with a web identity provider, such as 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 and the AWS SDK for Android to uniquely identify a user and supply the user with a consistent identity throughout the lifetime of an application.

To learn more about Amazon Cognito, see Amazon Cognito Overview in the AWS SDK for Android Developer Guide 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, and without deploying 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 APIs that produce temporary credentials, see Requesting Temporary Security Credentials and Comparing the AWS STS APIs 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 APIs.

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 operations but 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.

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 service's GetFederationToken or GetSessionToken APIs.

Optionally, you can pass an IAM access policy to this operation. If you choose not to pass a policy, the temporary security credentials that are returned by the operation have the permissions that are defined in the access policy of the role that is being assumed. If you pass a policy to this operation, the temporary security credentials that are returned by the operation have the permissions that are allowed by both the access policy of the role that is being assumed, and the policy that you pass. This gives you a way to further restrict the permissions for the resulting temporary security credentials. You cannot use the passed policy to grant permissions that are in excess of those allowed by the access policy of the role that is being assumed. For more information, see Permissions for AssumeRole, AssumeRoleWithSAML, and AssumeRoleWithWebIdentity in the IAM User Guide.

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:


For .NET Core, PCL and Unity this operation is only available in asynchronous form. Please refer to AssumeRoleWithWebIdentityAsync.

Namespace: Amazon.SecurityToken
Assembly: AWSSDK.SecurityToken.dll
Version: 3.x.y.z


public abstract AssumeRoleWithWebIdentityResponse AssumeRoleWithWebIdentity(
         AssumeRoleWithWebIdentityRequest request
Type: Amazon.SecurityToken.Model.AssumeRoleWithWebIdentityRequest

Container for the necessary parameters to execute the AssumeRoleWithWebIdentity service method.

Return Value
The response from the AssumeRoleWithWebIdentity service method, as returned by SecurityTokenService.


ExpiredTokenException The web identity token that was passed is expired or is not valid. Get a new identity token from the identity provider and then retry the request.
IDPCommunicationErrorException The request could not be fulfilled because the non-AWS identity provider (IDP) that was asked to verify the incoming identity token could not be reached. This is often a transient error caused by network conditions. Retry the request a limited number of times so that you don't exceed the request rate. If the error persists, the non-AWS identity provider might be down or not responding.
IDPRejectedClaimException The identity provider (IdP) reported that authentication failed. This might be because the claim is invalid. If this error is returned for the AssumeRoleWithWebIdentity operation, it can also mean that the claim has expired or has been explicitly revoked.
InvalidIdentityTokenException The web identity token that was passed could not be validated by AWS. Get a new identity token from the identity provider and then retry the request.
MalformedPolicyDocumentException The request was rejected because the policy document was malformed. The error message describes the specific error.
PackedPolicyTooLargeException The request was rejected because the policy document was too large. The error message describes how big the policy document is, in packed form, as a percentage of what the API allows.
RegionDisabledException STS is not activated in the requested region for the account that is being asked to generate credentials. The account administrator must use the IAM console to activate STS in that region. For more information, see Activating and Deactivating AWS STS in an AWS Region in the IAM User Guide.


To assume a role as an OpenID Connect-federated user

var response = client.AssumeRoleWithWebIdentity(new AssumeRoleWithWebIdentityRequest 
    DurationSeconds = 3600,
    ProviderId = "",
    RoleArn = "arn:aws:iam::123456789012:role/FederatedWebIdentityRole",
    RoleSessionName = "app1",
    WebIdentityToken = "Atza%7CIQEBLjAsAhRFiXuWpUXuRvQ9PZL3GMFcYevydwIUFAHZwXZXXXXXXXXJnrulxKDHwy87oGKPznh0D6bEQZTSCzyoCtL_8S07pLpr0zMbn6w1lfVZKNTBdDansFBmtGnIsIapjI6xKR02Yc_2bQ8LZbUXSGm6Ry6_BG7PrtLZtj_dfCTj92xNGed-CrKqjG7nPBjNIL016GGvuS5gSvPRUxWES3VYfm1wl7WTI7jn-Pcb6M-buCgHhFOzTQxod27L9CqnOLio7N3gZAGpsp6n1-AJBOCJckcyXe2c6uD0srOJeZlKUm2eTDVMf8IehDVI0r1QOnTV6KzzAI3OY87Vd_cVMQ"

AssumedRoleUser assumedRoleUser = response.AssumedRoleUser;
string audience = response.Audience;
Credentials credentials = response.Credentials;
integer packedPolicySize = response.PackedPolicySize;
string provider = response.Provider;
string subjectFromWebIdentityToken = response.SubjectFromWebIdentityToken;


Version Information

.NET Framework:
Supported in: 4.5, 4.0, 3.5

Portable Class Library:
Supported in: Windows Store Apps
Supported in: Windows Phone 8.1
Supported in: Xamarin Android
Supported in: Xamarin iOS (Unified)
Supported in: Xamarin.Forms

Supported Versions: 4.6 and above
Supported Platforms: Android, iOS, Standalone

See Also