How Can I Fix the Not Authorized To Perform Sts:AssumeRoleWithWebIdentity Error?

Encountering the error message “Not Authorized To Perform Sts:Assumerolewithwebidentity” can be a perplexing roadblock for developers and cloud users working with AWS Identity and Access Management (IAM). This issue often arises when applications or services attempt to assume a role using web identity federation but lack the necessary permissions or configurations. Understanding the root causes and implications of this error is crucial for maintaining secure and seamless access to AWS resources.

At its core, the error signals a permissions or trust relationship problem within the AWS Security Token Service (STS) workflow. When an application tries to exchange a web identity token for temporary AWS credentials, the process hinges on precise IAM role settings and policies. Without proper authorization, the STS denies the request, triggering the “Not Authorized” message. This scenario is common in environments leveraging federated authentication methods such as Amazon Cognito, OpenID Connect (OIDC), or third-party identity providers.

Delving into this topic reveals the intricate balance between security and accessibility in cloud identity management. By exploring the typical causes and best practices for resolving the “Not Authorized To Perform Sts:Assumerolewithwebidentity” error, readers can gain valuable insights into optimizing their AWS IAM configurations and ensuring smooth, secure role assumption workflows.

Common Causes of the Not Authorized Error

The `Not Authorized To Perform Sts:AssumeRoleWithWebIdentity` error typically arises when there are issues related to permissions, trust relationships, or configuration mismatches in AWS IAM roles and policies. Understanding these root causes is critical for effective troubleshooting.

One frequent cause is the absence of a proper trust relationship policy that allows the identity provider to assume the role. The role must explicitly trust the web identity token issuer, such as Amazon Cognito, Google, or any OpenID Connect (OIDC) provider. Without this, the STS service will deny the assume role request.

Another common issue is the lack of necessary permissions in the IAM role’s policy or the user’s policy trying to perform the `sts:AssumeRoleWithWebIdentity` action. Both the role and the caller must have the appropriate permissions for the operation to succeed.

Misconfiguration in the web identity token itself can also cause this error. If the token is expired, invalid, or not correctly signed by a trusted provider, AWS will reject the request.

Finally, incorrect role ARN or session name parameters provided in the assume role call can lead to authorization failures. These parameters must be precise and correctly formatted.

Key Components to Verify

When troubleshooting this error, it’s essential to verify the following components systematically:

• Trust Policy of the IAM Role: Confirm that the role’s trust policy includes the correct web identity provider as a trusted entity.
• IAM Permissions: Ensure both the role and the identity performing the assume role action have `sts:AssumeRoleWithWebIdentity` permissions.
• Web Identity Token Validity: Check that the token is valid, unexpired, and issued by a recognized identity provider.
• Correct Role ARN and Session Name: Validate that the parameters used in the assume role API call are accurate and correctly formatted.

Example of an IAM Trust Policy for Web Identity

The trust policy defines which entities can assume the IAM role. For a web identity provider, the trust policy typically looks like this:

“`json
{
“Version”: “2012-10-17”,
“Statement”: [
{
“Effect”: “Allow”,
“Principal”: {
“Federated”: “arn:aws:iam::123456789012:oidc-provider/token.actions.githubusercontent.com”
},
“Action”: “sts:AssumeRoleWithWebIdentity”,
“Condition”: {
“StringEquals”: {
“token.actions.githubusercontent.com:aud”: “sts.amazonaws.com”
}
}
}
]
}
“`

This policy allows the OIDC provider `token.actions.githubusercontent.com` to assume the role, but only when the audience (`aud`) claim equals `sts.amazonaws.com`.

Permissions Required for AssumeRoleWithWebIdentity

The permissions related to the `sts:AssumeRoleWithWebIdentity` action can be divided between the role’s trust policy and the IAM policies attached to the user or service making the request. The following table summarizes the key permissions:

In many cases, the caller may not need explicit permissions if the role’s trust policy allows the federated principal, but it’s a best practice to grant least privilege permissions explicitly.

Best Practices for Avoiding Authorization Errors

To minimize the occurrence of authorization errors related to `sts:AssumeRoleWithWebIdentity`, consider the following best practices:

• Use Fine-Grained Trust Policies: Limit trust relationships to only necessary identity providers and conditions.
• Regularly Rotate and Validate Tokens: Ensure tokens used for authentication are always valid and refreshed as needed.
• Grant Minimal Necessary Permissions: Apply least privilege principles both in trust policies and IAM permissions.
• Audit Role and Policy Changes: Use AWS CloudTrail or similar logging to monitor changes in IAM roles and policies.
• Test Role Assumption Separately: Validate the assume role operation with tools like AWS CLI to isolate issues from application code.

Common Troubleshooting Commands

Using AWS CLI commands can help verify role assumption permissions and trust relationships. Examples include:

• Checking the role’s trust policy:

“`bash
aws iam get-role –role-name YourRoleName –query ‘Role.AssumeRolePolicyDocument’ –output json
“`

• Attempting to assume the role with a web identity token (replace placeholders accordingly):

“`bash
aws sts assume-role-with-web-identity –role-arn arn:aws:iam::123456789012:role/YourRoleName –role-session-name session1 –web-identity-token file://token.jwt
“`

• Validating current permissions for the user:

“`bash
aws iam simulate-principal-policy –policy-source-arn arn:aws:iam::123456789012:user/YourUserName –action-names sts:AssumeRoleWithWebIdentity
“`

These commands aid in pinpointing permission or trust policy issues that cause the authorization failure.

Understanding the `Not Authorized To Perform Sts:AssumeRoleWithWebIdentity` Error

The error message `Not Authorized To Perform Sts:AssumeRoleWithWebIdentity` indicates that the AWS Security Token Service (STS) has denied a request to assume an IAM role via web identity federation. This typically occurs during authentication flows involving identity providers such as Amazon Cognito, Google, or Facebook, where an application exchanges a web identity token for temporary AWS credentials.

This error is a clear sign of insufficient permissions or misconfigurations in either the IAM role’s trust policy or the calling entity’s permissions. Addressing this requires a detailed understanding of how STS AssumeRoleWithWebIdentity operates and the associated authorization mechanisms.

Common Causes of the Authorization Failure

Several factors can cause this specific authorization failure:

• Missing or incorrect trust relationship: The IAM role’s trust policy must explicitly allow the identity provider and the appropriate audience (aud) to assume the role.
• Lack of permissions to call STS:AssumeRoleWithWebIdentity: The caller’s IAM user or role may lack permissions to invoke this STS action.
• Invalid or expired web identity token: The provided token must be valid and not expired.
• Incorrect role ARN or session name: Passing incorrect parameters can lead to authorization errors.
• Identity provider misconfiguration: The configured provider must match the token’s issuer.

Verifying and Correcting IAM Role Trust Policy

The trust policy for the IAM role controls which entities can assume the role. For `AssumeRoleWithWebIdentity`, the trust policy must specify the web identity provider as a principal and conditions that validate the token.

A typical trust policy structure is:

{
  "Federated": "accounts.google.com"
}

"Action": "sts:AssumeRoleWithWebIdentity"

{
  "StringEquals": {
    "accounts.google.com:aud": "YOUR_CLIENT_ID"
  }
}

Best Practices:

• Confirm that the `Federated` principal matches the token issuer.
• Ensure the `aud` condition corresponds to the client ID or audience expected by the identity provider.
• Avoid wildcard principals or overly permissive conditions to maintain security.

Ensuring Caller Permissions for STS Operations

The entity invoking `AssumeRoleWithWebIdentity` (often an application or service role) must have explicit permission to perform this operation. This permission is granted in an IAM policy attached to the caller.

Example IAM policy snippet:

“`json
{
“Version”: “2012-10-17”,
“Statement”: [
{
“Effect”: “Allow”,
“Action”: “sts:AssumeRoleWithWebIdentity”,
“Resource”: “arn:aws:iam::123456789012:role/YourRoleName”
}
]
}
“`

Checklist:

• Verify the policy is attached to the correct IAM user, role, or service principal.
• Confirm the resource ARN matches the IAM role being assumed.
• Avoid overly broad permissions; scope permissions to the minimum necessary role ARNs.

Validating the Web Identity Token

The token passed to `AssumeRoleWithWebIdentity` must be valid and issued by a supported identity provider. Common validation steps include:

• Checking token expiration timestamps to ensure the token is active.
• Verifying the token issuer (`iss`) matches the expected identity provider.
• Confirming the token audience (`aud`) aligns with the client ID or app ID configured in AWS.
• Ensuring token format is correct (usually a JWT).

If the token fails validation, STS will not authorize the request, resulting in the error.

Troubleshooting Parameter Issues in AssumeRoleWithWebIdentity API Calls

Proper parameters are essential when calling `AssumeRoleWithWebIdentity`. Key parameters include:

Parameter	Description	Common Issues
RoleArn	ARN of the IAM role to assume	Typographical errors or incorrect account numbers cause failure
RoleSessionName	Name for the assumed role session	Must be unique per session; invalid characters may cause errors
WebIdentityToken	Token from the identity provider	Expired or Expert Perspectives on Resolving Not Authorized To Perform Sts:Assumerolewithwebidentity Errors Dr. Melissa Chen (Cloud Security Architect, SecureCloud Solutions). The “Not Authorized To Perform Sts:Assumerolewithwebidentity” error typically indicates a misconfiguration in IAM roles or trust policies. It is crucial to verify that the identity provider is correctly associated with the role’s trust relationship and that the permissions explicitly allow the sts:AssumeRoleWithWebIdentity action. Additionally, ensuring that the token provided by the web identity provider is valid and unexpired is essential to prevent authorization failures. Rajiv Patel (AWS Infrastructure Engineer, GlobalTech Innovations). From an operational standpoint, this error often arises when the IAM role’s trust policy does not include the correct web identity provider ARN or when the role’s permissions lack the necessary sts:AssumeRoleWithWebIdentity action. It is best practice to audit the trust relationships regularly and use AWS CloudTrail logs to trace failed assume role attempts, which can pinpoint the exact cause of authorization denials. Elena Garcia (Identity and Access Management Specialist, CloudGuard Consulting). Addressing this authorization issue requires a thorough review of both the IAM role’s trust policy and the permissions granted to the federated user or application. Misaligned audience claims or incorrect token formats from the web identity provider can also trigger this error. Implementing automated validation of tokens and continuous monitoring of policy changes can significantly reduce the occurrence of sts:AssumeRoleWithWebIdentity authorization failures. Frequently Asked Questions (FAQs) What does the error “Not Authorized To Perform Sts:AssumeRoleWithWebIdentity” mean? This error indicates that the AWS Identity and Access Management (IAM) entity attempting to assume a role using web identity federation lacks the necessary permissions or trust relationship to perform the `sts:AssumeRoleWithWebIdentity` action. Which IAM policies are required to resolve the “Not Authorized To Perform Sts:AssumeRoleWithWebIdentity” error? The IAM role must have a trust policy that explicitly allows the web identity provider to assume the role, and the calling entity must have permission to invoke `sts:AssumeRoleWithWebIdentity` on that role. How can I verify the trust relationship for a role used with web identity federation? Check the role’s trust policy in the AWS Management Console or via the AWS CLI to ensure it includes a statement allowing the specific web identity provider (e.g., Amazon Cognito, Google, or Facebook) to assume the role. Can incorrect role ARN or web identity token cause this authorization error? Yes, providing an incorrect role ARN or an invalid/expired web identity token can lead to authorization failures, including the “Not Authorized” error. What steps should I take if I encounter this error during an application’s authentication flow? Review the IAM role’s trust policy, confirm the web identity provider configuration, validate the token integrity, and ensure the calling entity has permissions to perform `sts:AssumeRoleWithWebIdentity`. Is it necessary to configure the identity provider in AWS IAM before using AssumeRoleWithWebIdentity? Yes, the identity provider must be registered in IAM and properly configured in the role’s trust policy to allow federated users to assume the role using web identity tokens. The error “Not Authorized To Perform Sts:Assumerolewithwebidentity” typically indicates an issue with AWS Identity and Access Management (IAM) permissions when attempting to assume a role using web identity federation. This error arises when the AWS Security Token Service (STS) denies the request because the calling entity lacks the necessary permissions or the trust relationship between the identity provider and the AWS role is improperly configured. Understanding the underlying cause requires careful examination of IAM policies, trust policies, and the identity provider setup. Resolving this error involves ensuring that the IAM role’s trust policy explicitly allows the web identity provider to assume the role, and that the calling entity has permission to invoke the `sts:AssumeRoleWithWebIdentity` action. Additionally, the token provided by the identity provider must be valid and correctly formatted. Proper configuration of these elements is critical to enable secure and seamless federated access to AWS resources. Key takeaways include the importance of validating IAM role trust relationships, verifying that the correct permissions are granted, and ensuring the identity provider integration is properly established. Addressing these factors not only resolves the “Not Authorized To Perform Sts:Assumerolewithwebidentity” error but also strengthens the security posture of federated access Author Profile Barbara Hernandez Barbara Hernandez is the brain behind A Girl Among Geeks a coding blog born from stubborn bugs, midnight learning, and a refusal to quit. With zero formal training and a browser full of error messages, she taught herself everything from loops to Linux. Her mission? Make tech less intimidating, one real answer at a time. Barbara writes for the self-taught, the stuck, and the silently frustrated offering code clarity without the condescension. What started as her personal survival guide is now a go-to space for learners who just want to understand what the docs forgot to mention. Latest entries July 5, 2025WordPressHow Can You Speed Up Your WordPress Website Using These 10 Proven Techniques? July 5, 2025PythonShould I Learn C++ or Python: Which Programming Language Is Right for Me? July 5, 2025Hardware Issues and RecommendationsIs XFX a Reliable and High-Quality GPU Brand? July 5, 2025Stack Overflow QueriesHow Can I Convert String to Timestamp in Spark Using a Module?