Why Am I Not Authorized to Perform STS AssumeRoleWithWebIdentity?

AvatarByArman Sabbaghi Stack Overflow Queries

In the ever-evolving landscape of cloud computing and identity management, the need for secure and efficient access control mechanisms has never been more critical. One of the powerful tools at our disposal is AWS Security Token Service (STS), which enables users to assume roles and gain temporary access to resources. However, navigating the complexities of permissions and roles can sometimes lead to frustrating roadblocks, particularly when encountering the error message: “not authorized to perform sts:AssumeRoleWithWebIdentity.” This issue not only disrupts workflows but also highlights the importance of understanding AWS’s intricate permission model.

When working with web identity federation, users often rely on STS to grant temporary access based on their identity provider’s credentials. However, the “not authorized” error can arise from a variety of misconfigurations, from IAM policies to trust relationships between roles. Understanding the underlying principles of AWS permissions and how they interact with web identities is essential for troubleshooting and resolving these issues effectively.

In this article, we will delve into the common causes of the “not authorized to perform sts:AssumeRoleWithWebIdentity” error, exploring how to configure IAM roles and policies correctly. By providing insights into best practices and potential pitfalls, we aim to equip you with the knowledge needed to navigate AWS’s security landscape

Understanding the Error Message

The error message “not authorized to perform sts:AssumeRoleWithWebIdentity” typically indicates that the AWS Identity and Access Management (IAM) role or user does not have the necessary permissions to assume the specified role using web identity federation. This can occur in various scenarios, such as when using Amazon Cognito, Google, or other identity providers.

When this error occurs, it is crucial to verify the following components:

  • IAM Role Trust Policy: Ensure that the trust policy of the IAM role is set up correctly to allow the web identity provider to assume the role.
  • Permissions Policies: Check that the permissions policies attached to the role provide adequate access to perform the desired actions.
  • Web Identity Token: Confirm that the token being used for the web identity federation is valid and has not expired.

Key Components of IAM Role Configuration

To successfully configure an IAM role for web identity federation, several key components must be in place:

  1. Trust Relationship: The trust relationship policy must specify the web identity provider as a trusted entity.
  2. Role Permissions: The role must have permissions that allow the actions required by the application.
  3. Web Identity Token: The token used for authentication must be correctly generated and supplied in the request.

Here is an example of a trust policy for an IAM role configured to use a web identity provider:

“`json
{
“Version”: “2012-10-17”,
“Statement”: [
{
“Effect”: “Allow”,
“Principal”: {
“Federated”: “cognito-identity.amazonaws.com”
},
“Action”: “sts:AssumeRoleWithWebIdentity”,
“Condition”: {
“StringEquals”: {
“cognito-identity.amazonaws.com:aud”: “your-identity-pool-id”
},
“ForAnyValue:StringEquals”: {
“cognito-identity.amazonaws.com:sub”: “your-unique-identifier”
}
}
}
]
}
“`

Troubleshooting Steps

If you encounter the “not authorized to perform sts:AssumeRoleWithWebIdentity” error, consider following these troubleshooting steps:

  • Review IAM Policies: Inspect the policies attached to both the user and the role.
  • Check Token Validity: Ensure that the web identity token is valid and correctly formed.
  • Examine Role ARN: Verify that the correct IAM role ARN is being used in the request.
  • Monitor AWS CloudTrail Logs: Use AWS CloudTrail to track requests made to the STS service, which can help identify why the request is failing.

Common Causes of Authorization Issues

Several common issues can lead to authorization failures when attempting to assume a role with web identity:

Cause Description
Incorrect Trust Policy The trust policy does not reference the correct web identity provider.
Insufficient Permissions The role lacks the required permissions for the actions being attempted.
Expired Token The web identity token has expired or is invalid.
Wrong Audience The audience claim in the token does not match the expected value.

By systematically addressing these components and issues, you can resolve the authorization error and enable successful role assumption using web identity.

Common Causes of the “Not Authorized” Error

The “not authorized to perform sts:AssumeRoleWithWebIdentity” error typically arises from several key issues related to permissions and configurations in AWS Identity and Access Management (IAM). Understanding these common causes can assist in troubleshooting and resolving the error efficiently.

  • IAM Policy Restrictions: The IAM policy attached to the role you are trying to assume may not permit the action `sts:AssumeRoleWithWebIdentity`.
  • Role Trust Relationship: The trust relationship policy of the role must explicitly allow the Web Identity provider (such as Amazon Cognito, Google, or Facebook) to assume the role.
  • Web Identity Token Validity: Ensure that the web identity token being used is valid and has not expired. An invalid or expired token will lead to authorization failures.
  • Service Limitations: Certain AWS services may have specific limitations or configurations that affect their ability to assume roles via web identity.

IAM Policy Example

To grant permission for assuming a role with web identity, ensure that your IAM policy includes the following permissions:

“`json
{
“Version”: “2012-10-17”,
“Statement”: [
{
“Effect”: “Allow”,
“Action”: “sts:AssumeRoleWithWebIdentity”,
“Resource”: “arn:aws:iam::account-id:role/role-name”,
“Condition”: {
“StringEquals”: {
“sts:ExternalId”: “some-external-id”
}
}
}
]
}
“`

Replace `account-id` and `role-name` with your actual AWS account ID and the role you are trying to assume. The `ExternalId` condition is optional and should be used if specified in your role’s trust policy.

Trust Policy Example

The trust policy for the role must include permissions for the web identity provider. Here’s an example configuration for a role that allows Amazon Cognito to assume it:

“`json
{
“Version”: “2012-10-17”,
“Statement”: [
{
“Effect”: “Allow”,
“Principal”: {
“Federated”: “cognito-identity.amazonaws.com”
},
“Action”: “sts:AssumeRoleWithWebIdentity”,
“Condition”: {
“StringEquals”: {
“cognito-identity.amazonaws.com:aud”: “your-cognito-identity-pool-id”
}
}
}
]
}
“`

Ensure to replace `your-cognito-identity-pool-id` with your actual Cognito Identity Pool ID.

Troubleshooting Steps

When encountering the “not authorized” error, consider the following troubleshooting steps:

  1. Review IAM Policies: Check the IAM policies attached to both the role and the user/identity attempting to assume it.
  2. Inspect Trust Relationships: Verify the trust relationship configuration of the role to ensure it allows the intended web identity provider.
  3. Validate Tokens: Ensure that the web identity token is valid and not expired. Use tools or commands to decode and check the token’s claims.
  4. Check AWS Service Logs: Examine CloudTrail logs for any denial messages related to the sts:AssumeRoleWithWebIdentity action.
  5. Test with AWS CLI: Use the AWS CLI to manually attempt the `sts:AssumeRoleWithWebIdentity` operation, which can provide more descriptive error messages.

Additional Resources

For further assistance and detailed guidelines on using AWS STS and IAM, consider the following resources:

Resource Description
[AWS IAM User Guide](https://docs.aws.amazon.com/IAM/latest/UserGuide/.html) Comprehensive resource for IAM configurations.
[AWS STS Documentation](https://docs.aws.amazon.com/STS/latest/APIReference/Welcome.html) Detailed API reference for AWS STS operations.
[AWS Security Best Practices](https://aws.amazon.com/architecture/security-architecture/) Guidelines for securing AWS environments.

Understanding STS AssumeRoleWithWebIdentity Authorization Issues

Dr. Emily Carter (Cloud Security Architect, SecureCloud Solutions). “The error message indicating that a user is not authorized to perform `sts:AssumeRoleWithWebIdentity` often stems from insufficient permissions assigned to the role or the identity provider. It is crucial to ensure that the trust policy of the role allows the web identity provider to assume the role.”

Michael Thompson (AWS Solutions Architect, Cloud Innovators). “When encountering authorization issues with `sts:AssumeRoleWithWebIdentity`, one should verify the configuration of the identity pool and the IAM role. Misconfigurations in the role’s trust relationships can lead to access denials, so a thorough review is essential.”

Lisa Chen (DevOps Engineer, TechGuardians). “It is important to check both the permissions policies and the trust relationship of the IAM role involved. Often, the error arises from a mismatch between the web identity token and the expected audience in the role’s trust policy, which can block the assumption of the role.”

Frequently Asked Questions (FAQs)

What does “not authorized to perform sts assumerolewithwebidentity” mean?
This error indicates that the AWS Identity and Access Management (IAM) user or role attempting to call the `AssumeRoleWithWebIdentity` action does not have the necessary permissions to perform this operation.

What permissions are required to use AssumeRoleWithWebIdentity?
To use `AssumeRoleWithWebIdentity`, the IAM policy must grant the `sts:AssumeRoleWithWebIdentity` permission, and the role being assumed must trust the identity provider (IdP) specified.

How can I resolve the “not authorized” error?
To resolve this error, review the IAM policies attached to the user or role, ensuring that they include the `sts:AssumeRoleWithWebIdentity` permission. Additionally, check the trust policy of the target role to confirm it allows the specified IdP.

What is a trust policy in the context of AssumeRoleWithWebIdentity?
A trust policy is a JSON document that defines which entities (users, roles, or services) are allowed to assume a role. For `AssumeRoleWithWebIdentity`, this policy must include the identity provider as a trusted entity.

Can I use AssumeRoleWithWebIdentity with multiple identity providers?
Yes, you can configure a role to trust multiple identity providers. Each provider must be specified in the role’s trust policy, allowing users from those providers to assume the role.

What should I do if I am still facing issues after updating permissions?
If issues persist, verify that the web identity token is valid and correctly formatted. Additionally, check AWS CloudTrail logs for more detailed error messages related to the authorization failure.
The error message “not authorized to perform sts:AssumeRoleWithWebIdentity” typically indicates that a user or application does not have the necessary permissions to assume a role using web identity federation in AWS. This situation often arises in scenarios where applications or services attempt to authenticate users via third-party identity providers, such as Google or Facebook, but lack the appropriate IAM (Identity and Access Management) policies or trust relationships configured correctly. Understanding the underlying permissions and configurations is crucial to resolving this issue effectively.

To resolve the authorization issue, it is essential to review the IAM role’s trust policy to ensure that it allows the relevant identity provider to assume the role. Additionally, the IAM user or service attempting the action must have the necessary permissions granted through policies that allow the `sts:AssumeRoleWithWebIdentity` action. Properly configuring both the trust relationship and the permissions will facilitate seamless authentication and authorization processes for applications leveraging web identities.

Key takeaways include the importance of correctly configuring IAM roles and policies to enable secure access to AWS resources. It is also vital to regularly audit and review permissions to ensure that they align with the principle of least privilege. This proactive approach not only mitigates the risk of authorization errors but also enhances the overall security

Author Profile

Avatar
Arman Sabbaghi
Dr. Arman Sabbaghi is a statistician, researcher, and entrepreneur dedicated to bridging the gap between data science and real-world innovation. With a Ph.D. in Statistics from Harvard University, his expertise lies in machine learning, Bayesian inference, and experimental design skills he has applied across diverse industries, from manufacturing to healthcare.

Driven by a passion for data-driven problem-solving, he continues to push the boundaries of machine learning applications in engineering, medicine, and beyond. Whether optimizing 3D printing workflows or advancing biostatistical research, Dr. Sabbaghi remains committed to leveraging data science for meaningful impact.