About SAML 2.0-based federation

To configure your organization's IdP and AWS to trust each other

1. Register AWS as a service provider (SP) with the IdP of your organization. Use the SAML metadata document from https:// region-code .signin.aws.amazon.com/static/saml-metadata.xml

   For a list of possible region-code values, see the Region column in AWS Sign-In endpoints .

   You can optionally use the SAML metadata document from https://signin.aws.amazon.com/static/saml-metadata.xml

   Using your organization's IdP, you generate an equivalent metadata XML file that can describe your IdP as an IAM identity provider in AWS. It must include the issuer name, a creation date, an expiration date, and keys that AWS can use to validate authentication responses (assertions) from your organization.

   In the IAM console, you create a SAML identity provider entity. As part of this process, you upload the SAML metadata document that was produced by the IdP in your organization in Step 2 . For more information, see Creating IAM SAML identity providers .

   In IAM, you create one or more IAM roles. In the role's trust policy, you set the SAML provider as the principal, which establishes a trust relationship between your organization and AWS. The role's permission policy establishes what users from your organization are allowed to do in AWS. For more information, see Creating a role for a third-party Identity Provider (federation) .

   Note

   SAML IDPs used in a role trust policy must be in the same account that the role is in.

   In your organization's IdP, you define assertions that map users or groups in your organization to the IAM roles. Note that different users and groups in your organization might map to different IAM roles. The exact steps for performing the mapping depend on what IdP you're using. In the earlier scenario of an Amazon S3 folder for users, it's possible that all users will map to the same role that provides Amazon S3 permissions. For more information, see Configuring SAML assertions for the authentication response .

   If your IdP enables SSO to the AWS console, then you can configure the maximum duration of the console sessions. For more information, see Enabling SAML 2.0 federated users to access the AWS Management Console .

   Note

   The AWS implementation of SAML 2.0 federation does not support encrypted SAML assertions between the IAM identity provider and AWS. However, the traffic between the customer's systems and AWS is transmitted over an encrypted (TLS) channel.

   In the application that you're creating, you call the AWS Security Token Service AssumeRoleWithSAML API, passing it the ARN of the SAML provider you created in Step 3 , the ARN of the role to assume that you created in Step 4 , and the SAML assertion about the current user that you get from your IdP. AWS makes sure that the request to assume the role comes from the IdP referenced in the SAML provider.

   For more information, see AssumeRoleWithSAML in the AWS Security Token Service API Reference .

   If the request is successful, the API returns a set of temporary security credentials, which your application can use to make signed requests to AWS. Your application has information about the current user and can access user-specific folders in Amazon S3, as described in the previous scenario.

   Overview of the role to allow SAML-federated access to your AWS resources

   The role or roles that you create in IAM define what federated users from your organization are allowed to do in AWS. When you create the trust policy for the role, you specify the SAML provider that you created earlier as the Principal . You can additionally scope the trust policy with a Condition to allow only users that match certain SAML attributes to access the role. For example, you can specify that only users whose SAML affiliation is staff (as asserted by https://openidp.feide.no) are allowed to access the role, as illustrated by the following sample policy:

   "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Principal": { "Federated": "arn:aws:iam:: account-id :saml-provider/ExampleOrgSSOProvider"}, "Action": "sts:AssumeRoleWithSAML", "Condition": { "StringEquals": { "saml:aud": "https://signin.aws.amazon.com/saml", "saml:iss": "https://openidp.feide.no" "ForAllValues:StringLike": { "saml:edupersonaffiliation": ["staff"]}

   Note

   SAML IDPs used in a role trust policy must be in the same account that the role is in.

   For more information about the SAML keys that you can check in a policy, see Available keys for SAML-based AWS STS federation .

   You can include regional endpoints for the saml:aud attribute at https:// region-code .signin.aws.amazon.com/static/saml-metadata.xml . For a list of possible region-code values, see the Region column in AWS Sign-In endpoints .

   For the permission policy in the role, you specify permissions as you would for any role. For example, if users from your organization are allowed to administer Amazon Elastic Compute Cloud instances, you must explicitly allow Amazon EC2 actions in the permissions policy, such as those in the AmazonEC2FullAccess managed policy.

   Uniquely identifying users in SAML-based federation

   When you create access policies in IAM, it's often useful to be able to specify permissions based on the identity of users. For example, for users who have been federated using SAML, an application might want to keep information in Amazon S3 using a structure like this:

   myBucket/app1/user1
   myBucket/app1/user2
   myBucket/app1/user3

   You can create the bucket ( myBucket ) and folder ( app1 ) through the Amazon S3 console or the AWS CLI, since those are static values. However, the user-specific folders ( user1 , user2 , user3 , etc.) have to be created at run time using code, since the value that identifies the user isn't known until the first time the user signs in through the federation process.

   To write policies that reference user-specific details as part of a resource name, the user identity has to be available in SAML keys that can be used in policy conditions. The following keys are available for SAML 2.0–based federation for use in IAM policies. You can use the values returned by the following keys to create unique user identifiers for resources like Amazon S3 folders.

   saml:namequalifier . A hash value based on the concatenation of the Issuer response value ( saml:iss ) and a string with the AWS account ID and the friendly name (the last part of the ARN) of the SAML provider in IAM. The concatenation of the account ID and friendly name of the SAML provider is available to IAM policies as the key saml:doc . The account ID and provider name must be separated by a '/' as in "123456789012/provider_name". For more information, see the saml:doc key at Available keys for SAML-based AWS STS federation .

   The combination of NameQualifier and Subject can be used to uniquely identify a federated user. The following pseudocode shows how this value is calculated. In this pseudocode + indicates concatenation, SHA1 represents a function that produces a message digest using SHA-1, and Base64 represents a function that produces Base-64 encoded version of the hash output.

   Base64 ( SHA1 ( "https://example.com/saml" + "123456789012" + "/MySAMLIdP"

   For more information about the policy keys that are available for SAML-based federation, see Available keys for SAML-based AWS STS federation .

   saml:sub (string). This is the subject of the claim, which includes a value that uniquely identifies an individual user within an organization (for example, _cbb88bf52c2510eabe00c1642d4643f41430fe25e3 ).

   saml:sub_type (string). This key can be persistent , transient , or the full Format URI from the Subject and NameID elements used in your SAML assertion. A value of persistent indicates that the value in saml:sub is the same for a user across all sessions. If the value is transient , the user has a different saml:sub value for each session. For information about the NameID element's Format attribute, see Configuring SAML assertions for the authentication response .

   The following example shows a permission policy that uses the preceding keys to grant permissions to a user-specific folder in Amazon S3. The policy assumes that the Amazon S3 objects are identified using a prefix that includes both saml:namequalifier and saml:sub . Notice that the Condition element includes a test to be sure that saml:sub_type is set to persistent . If it is set to transient , the saml:sub value for the user can be different for each session, and the combination of values should not be used to identify user-specific folders.

   "Version": "2012-10-17", "Statement": { "Effect": "Allow", "Action": [ "s3:GetObject", "s3:PutObject", "s3:DeleteObject" "Resource": [ "arn:aws:s3:::exampleorgBucket/backup/$ { saml:namequalifier}/$ { saml:sub}", "arn:aws:s3:::exampleorgBucket/backup/$ { saml:namequalifier}/$ { saml:sub}/*" "Condition": { "StringEquals": { "saml:sub_type": "persistent"}}