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Fix 'Not Authorized To Perform Sts:AssumeRoleWithWebIdentity'

11 min read 11-15- 2024
Fix 'Not Authorized To Perform Sts:AssumeRoleWithWebIdentity'

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When you're working with AWS (Amazon Web Services), you might encounter the frustrating error message: "Not Authorized to Perform sts:AssumeRoleWithWebIdentity". This issue arises when you try to assume an IAM (Identity and Access Management) role using a web identity token but lack the necessary permissions. In this comprehensive guide, we will explore the causes of this error and how you can fix it, ensuring that your applications work smoothly and securely.

Understanding the Error Message

The error message "Not Authorized to Perform sts:AssumeRoleWithWebIdentity" typically indicates that the AWS service or user does not have permission to assume the specified role using a web identity. Web identity federation allows users to sign in to your application using their existing accounts from providers like Google, Facebook, or Amazon.

When an application tries to assume a role with the credentials from a web identity provider, it must have the correct permissions set in the IAM policies. If those permissions are missing or incorrect, you will receive this error.

Key Components of sts:AssumeRoleWithWebIdentity

Before diving into the solutions, let’s take a moment to understand the key components involved in sts:AssumeRoleWithWebIdentity:

  • IAM Roles: These are AWS identities with specific permissions that can be assumed by users or services.
  • Web Identity Tokens: These are tokens provided by identity providers (IdPs) after a user logs in, which can be used to authenticate with AWS.
  • STS (Security Token Service): A service that allows you to request temporary security credentials for AWS accounts and users.

Common Causes of the Error

Understanding the potential reasons for this error can help you quickly diagnose and resolve the issue. Here are some common causes:

  1. Missing Role Trust Policy: The role you are trying to assume must have a trust policy that allows the identity provider to assume it.

  2. Insufficient Permissions: The role being assumed needs to be explicitly permitted in your IAM policy for it to be assumed successfully.

  3. Incorrect Identity Token: If the web identity token provided is invalid or expired, it will lead to authentication failures.

  4. Incorrectly Configured Identity Provider: Ensure that the identity provider is set up correctly in the AWS Management Console.

  5. Session Name Issues: The session name provided when assuming the role might not meet the requirements specified in the IAM policies.

Important Note

"Always ensure your AWS IAM policies follow the principle of least privilege, giving users only the permissions they absolutely need."

How to Fix the Error

Now that we’ve outlined the causes, let’s discuss how you can fix the "Not Authorized to Perform sts:AssumeRoleWithWebIdentity" error.

Step 1: Check the Trust Policy of the IAM Role

The first step in troubleshooting the error is to verify the trust policy associated with the IAM role. Ensure that the role’s trust relationship is configured to allow the web identity provider to assume the role.

Here's how to check and modify the trust policy:

  1. Go to the IAM Management Console.
  2. Navigate to Roles and select the role you want to check.
  3. Under the Trust Relationships tab, click on Edit Trust Relationship.
  4. Ensure that the policy allows the relevant web identity provider (like Facebook or Google) to assume the role.

Here’s an example trust policy for a role that allows users authenticated through Google:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Federated": "accounts.google.com"
            },
            "Action": "sts:AssumeRoleWithWebIdentity",
            "Condition": {
                "StringEquals": {
                    "accounts.google.com:sub": "YOUR-GOOGLE-ID"
                }
            }
        }
    ]
}

Step 2: Validate IAM Permissions

The next step is to validate the IAM permissions associated with the role. Ensure that the role includes permissions for sts:AssumeRoleWithWebIdentity. You may need to add or update policies.

Here’s how to do this:

  1. Go to the IAM Management Console.
  2. Navigate to Policies and select the policy that is attached to the role.
  3. Ensure the policy has the following action:
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "sts:AssumeRoleWithWebIdentity",
            "Resource": "arn:aws:iam::ACCOUNT-ID:role/ROLE-NAME"
        }
    ]
}

Step 3: Verify the Identity Token

If the permissions and trust policy look correct, the next step is to verify the identity token being passed to AWS.

  • Ensure that the token is valid and not expired.
  • Check that the token is correctly formatted.

Step 4: Review the Identity Provider Configuration

Ensure that the identity provider is properly configured in the AWS Management Console:

  1. Go to Identity Providers in the IAM Management Console.
  2. Check that the identity provider you are using (e.g., Google, Facebook) is correctly configured.

Step 5: Check for Session Name Restrictions

When assuming the role, you may also need to specify a session name. Ensure that the session name adheres to any restrictions specified in your IAM policies.

The session name should:

  • Be unique across sessions.
  • Consist of 2 to 64 characters.

Step 6: Testing and Verification

After making the changes, it’s crucial to test the functionality to ensure that the error no longer appears.

A Sample Testing Workflow:

  1. Try to log in through the identity provider again.
  2. Execute the sts:AssumeRoleWithWebIdentity call.
  3. Confirm whether you can now access the resources associated with the assumed role.

Troubleshooting Checklist

To summarize, here’s a troubleshooting checklist you can follow:

<table> <tr> <th>Step</th> <th>Action</th> </tr> <tr> <td>1</td> <td>Check the trust policy of the IAM role</td> </tr> <tr> <td>2</td> <td>Validate IAM permissions for sts:AssumeRoleWithWebIdentity</td> </tr> <tr> <td>3</td> <td>Verify the identity token for validity</td> </tr> <tr> <td>4</td> <td>Review the identity provider configuration</td> </tr> <tr> <td>5</td> <td>Check session name restrictions</td> </tr> <tr> <td>6</td> <td>Test and verify the changes made</td> </tr> </table>

Additional Resources and Best Practices

For further information, consider reviewing the following AWS documentation:

By ensuring that you follow the principle of least privilege and implementing best practices, you can maintain a secure AWS environment while effectively managing permissions for your applications.

Conclusion

The "Not Authorized to Perform sts:AssumeRoleWithWebIdentity" error can be frustrating, but with a systematic approach, it can be resolved. By carefully reviewing trust policies, IAM permissions, identity tokens, and provider configurations, you can ensure your AWS applications function seamlessly. Always remember to test your configurations and maintain security best practices as you build and scale your applications. With these steps, you should be able to handle this issue effectively and continue to leverage the power of AWS in your projects.

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