Resource Access Management:FAQ about RAM roles and STS tokens

Why do I get the "You are not authorized..." error when calling AssumeRole?

When you call the AssumeRole API operation, you might receive the following error message:

Error message: You are not authorized to do this action. You should be authorized by RAM.

This error can occur for the following reasons:

• You are calling the operation as the Alibaba Cloud account.

  The AssumeRole API operation cannot be called by an Alibaba Cloud account. You must call it as a RAM user or role.

• The calling identity does not have permissions to assume the role.

  To grant the necessary permissions, attach the AliyunSTSAssumeRoleAccess policy or a custom policy to the calling identity (the RAM user or role making the call). The custom policy must include a statement with the Allow effect on the sts:AssumeRole action. For an example, see Policy example.

• The role's trust policy does not include the calling identity as a principal.

  Update the trust policy of the target role to allow the calling identity to assume it. For more information, see Modify the trust policy of a RAM role.

Who can call the AssumeRole API operation?

The AssumeRole API operation, which is used to obtain temporary security credentials for a RAM role, can only be called by a RAM user or role. It cannot be called by an Alibaba Cloud account.

What types of RAM roles are there and who can assume them?

RAM provides the following role types based on the principal:

How do I restrict a specific RAM user from assuming a specific RAM role?

1. Update the RAM role's trust policy.

   In the trust policy of the RAM role, use the Principal element to specify the RAM user that is allowed to assume the role. In the policy, replace <account-id> with the ID of your Alibaba Cloud account, and <user-name> with the name of the RAM user. For more information, see Modify the trust policy of a RAM role.

   Policy example:

   {
       "Statement": [
           {
               "Action": "sts:AssumeRole",
               "Effect": "Allow",
               "Principal": {
                   "RAM": [
                       "acs:ram::<account-id>:user/<user-name>"
                   ]
               }
           }
       ],
       "Version": "1"
   }

2. Grant the RAM user permission to assume the role.

   Attach the AliyunSTSAssumeRoleAccess policy or a custom policy to the RAM user. A custom policy allows you to restrict which roles the user can assume.

   In the custom policy, use the Resource element to specify the ARN of the RAM role that can be assumed. In the policy, replace <account-id> with the ID of your Alibaba Cloud account, and <role-name> with the name of the RAM role. For more information, see Create a custom policy and Grant permissions to a RAM user.

   Policy example:

   {
       "Statement": [
           {
               "Action": "sts:AssumeRole",
               "Effect": "Allow",
               "Resource": "acs:ram:*:<account-id>:role/<role-name>"
           }
       ],
       "Version": "1"
   }

How do I view the ARN of a RAM role?

1. Log on to the RAM console.

2. In the left-side navigation pane, choose Identities > Roles.

3. Click the name of the target RAM role.

4. In the Basic Information section, find and copy the role's ARN.

Are there API request limits for STS?

The AssumeRole API operation is throttled at 100 requests per second. This limit applies to the entire Alibaba Cloud account, including all RAM users and roles within it.

If you exceed this limit, STS returns one of the following error messages:

• Error messages

  Error code	Error message
  Throttling.Api	Request was denied due to api flow control.
  Throttling.User	Request was denied due to user flow control.
  Throttling	Request was denied due to flow control.

• A 302 status code

If you receive these errors, reduce your request rate. If your application requires a higher request rate, you can request a quota increase by submitting a ticket. If your application requires a higher request rate, you can request a quota increase by submitting a ticket.

What are the permission limits of an STS token?

The permissions of an STS token are the intersection of the role's identity-based policies and the session policy that you pass in the Policy parameter of the AssumeRole call.

How long is an STS token valid?

By default, an STS token is valid for 3,600 seconds (1 hour). You can specify a duration from a minimum of 900 seconds (15 minutes) to a maximum defined by the role's maximum session duration setting.

Are multiple STS tokens for the same role valid simultaneously?

Yes. Multiple STS tokens for the same role can be valid at the same time. Each token is valid until it expires, and creating a new token does not affect existing ones.

What do I do if an STS token is leaked?

If you suspect that an STS token has been compromised, you can immediately invalidate all active tokens for that RAM role. To do this, you must either remove all permissions from the role or delete it entirely.

1. Log on to the RAM console.

2. To revoke permissions, detach all policies from the RAM role.

   For more information, see Revoke permissions from a RAM role.

3. To revoke permissions, delete the RAM role.

   For more information, see Delete a RAM role.

   This action immediately invalidates all unexpired STS tokens for that role.

If you still need to use the RAM role, you can create a new role with the same name and attach the same policies to it.

Is there a maximum length for an STS token?

No. The length of STS tokens is variable. In your code, do not make assumptions about the maximum length of a token. Always allow for tokens of variable length.