Setting up a SAML provider as an identity pool IdP

With Amazon Cognito identity pools, you can authenticate users with identity providers (IdPs) through SAML 2.0. You can use an IdP that supports SAML with Amazon Cognito to provide a simple onboarding flow for your users. Your SAML-supporting IdP specifies the IAM roles that your users can assume. This way, different users can receive different sets of permissions.

Configuring your identity pool for a SAML IdP

The following steps describe how to configure your identity pool to use a SAML-based IdP.

Note

Before you configure your identity pool to support a SAML provider, first configure the SAML IdP in the IAM console. For more information, see Integrating third-party SAML solution providers with AWS in the IAM User Guide.

To add a SAML identity provider (IdP)

1. Choose Identity pools from the Amazon Cognito console. Select an identity pool.

2. Choose the User access tab.

3. Select Add identity provider.

4. Choose SAML.

5. Choose a SAML identity provider from the IAM IdPs in your AWS account. If you want to add a new SAML provider, choose Create new provider to navigate to the IAM console.

6. To set the role that Amazon Cognito requests when it issues credentials to users who have authenticated with this provider, configure Role settings.

   1. You can assign users from that IdP the Default role that you set up when you configured your Authenticated role, or you can Choose role with rules.

      1. If you chose Choose role with rules, enter the source Claim from your user's authentication, the Operator that you want to compare the claim by, the Value that will cause a match to this role choice, and the Role that you want to assign when the Role assignment matches. Select Add another to create an additional rule based on a different condition.

      2. Choose a Role resolution. When your user's claims don't match your rules, you can deny credentials or issue credentials for your Authenticated role.

7. To change the principal tags that Amazon Cognito assigns when it issues credentials to users who have authenticated with this provider, configure Attributes for access control.

   1. To apply no principal tags, choose Inactive.

   2. To apply principal tags based on sub and aud claims, choose Use default mappings.

   3. To create your own custom schema of attributes to principal tags, choose Use custom mappings. Then enter a Tag key that you want to source from each Claim that you want to represent in a tag.

8. Select Save changes.

Configuring your SAML IdP

After you create the SAML provider, configure your SAML IdP to add relying party trust between your IdP and AWS. With many IdPs, you can specify a URL that the IdP can use to read relying party information and certificates from an XML document. For AWS, you can use https://signin.aws.amazon.com/static/saml-metadata.xml. The next step is to configure the SAML assertion response from your IdP to populate the claims that AWS needs. For details on the claim configuration, see Configuring SAML assertions for authentication response.

When your SAML IdP includes more than one signing certificate in SAML metadata, at sign-in your user pool determines that the SAML assertion is valid if it matches any certificate in the SAML metadata.

Customizing your user role with SAML

When you use SAML with Amazon Cognito Identity, you can customize the role for the end user. Amazon Cognito only supports the enhanced flow with the SAML-based IdP. You don't need to specify an authenticated or unauthenticated role for the identity pool to use a SAML-based IdP. The https://aws.amazon.com/SAML/Attributes/Role claim attribute specifies one or more pairs of comma -delimited role and provider ARN. These are the roles that the user can assume. You can configure the SAML IdP to populate the role attributes based on the user attribute information available from the IdP. If you receive multiple roles in the SAML assertion, populate the optional customRoleArn parameter when you call getCredentialsForIdentity. The user assumes this customRoleArn if the role matches one in the claim in the SAML assertion.

Authenticating users with a SAML IdP

To federate with the SAML-based IdP, determine the URL where the user initiates the login. AWS federation uses IdP-initiated login. In AD FS 2.0, the URL takes the form of https://<fqdn>/adfs/ls/IdpInitiatedSignOn.aspx?loginToRp=urn:amazon:webservices.

To add support for your SAML IdP in Amazon Cognito, first authenticate users with your SAML identity provider from your iOS or Android application. The code that you use to integrate and authenticate with the SAML IdP is specific to SAML providers. After you authenticate your user, you can use Amazon Cognito APIs to provide the resulting SAML assertion to Amazon Cognito Identity .

You can't repeat, or replay, a SAML assertion in the Logins map of your identity pool API request. A replayed SAML assertion has an assertion ID that duplicates the ID of an earlier API request. API operations that can accept a SAML assertion in the Logins map include GetId, GetCredentialsForIdentity, GetOpenIdToken, and GetOpenIDTokenForDeveloperIdentity. You can replay a SAML assertion ID one time per API request in an identity pool authentication flow. For example, you can supply the same SAML assertion in a GetId request and a subsequent GetCredentialsForIdentity request, but not in a second GetId request.

Android

If you use the Android SDK, you can populate the logins map with the SAML assertion as follows.

Map logins = new HashMap();
logins.put("arn:aws:iam::aws account id:saml-provider/name", "base64 encoded assertion response");
// Now this should be set to CognitoCachingCredentialsProvider object.
CognitoCachingCredentialsProvider credentialsProvider = new CognitoCachingCredentialsProvider(context, identity pool id, region);
credentialsProvider.setLogins(logins);
// If SAML assertion contains multiple roles, resolve the role by setting the custom role
credentialsProvider.setCustomRoleArn("arn:aws:iam::aws account id:role/customRoleName");
// This should trigger a call to the Amazon Cognito service to get the credentials.
credentialsProvider.getCredentials();

iOS

If you are using the iOS SDK, you can provide the SAML assertion in AWSIdentityProviderManager as follows.

- (AWSTask<NSDictionary<NSString*,NSString*> *> *) logins {
    //this is hardcoded for simplicity, normally you would asynchronously go to your SAML provider 
    //get the assertion and return the logins map using a AWSTaskCompletionSource
    return [AWSTask taskWithResult:@{@"arn:aws:iam::aws account id:saml-provider/name":@"base64 encoded assertion response"}];
}
 
// If SAML assertion contains multiple roles, resolve the role by setting the custom role.
// Implementing this is optional if there is only one role.
- (NSString *)customRoleArn {
    return @"arn:aws:iam::accountId:role/customRoleName";
}