Why does an "access denied" error occur during object operations?

When you perform operations such as listing, reading, or writing objects, the result is an error 403 Access Denied.

You receive the following error message when you perform operations on an IBM Cloud Object Storage bucket:

Error: AccessDenied: Access Denied status code: 403

Or you might experience symptoms such as the following:

• Failure to access a bucket or objects
• AccessDenied errors during API or CLI operations
• Successful connection to the Object Storage endpoint but operation denied

Access Denied errors that occur during bucket operations are often caused by missing or insufficient permissions or by network access restrictions.

Use the following steps to troubleshoot and resolve the error and ensure that your access to IBM Cloud Object Storage works as expected:

1. Verify permissions

   1. Begin by identifying the service ID or user credentials used for the operation.
   2. Review the IAM policies assigned to the service ID or to the user. You can view assigned IAM policies in the IBM Cloud console or by using the CLI.
   3. Confirm that the credentials have appropriate roles for the Object Storage instance, such as Writer or Manager. Ensure that the roles are sufficient for the required operations, such as Writer or higher.
   4. If you enabled fine-grained access controls, verify that the credentials allow operations on the specific bucket or objects.
   5. Update or adjust the assigned policies as needed.

   For more information about Identity and Access Management (IAM) roles, see Getting Started with IAM.

2. Validate tokens and endpoints

   1. Check that you correctly generated the IAM token. Make sure that the token is valid for accessing Object Storage resources.
   2. Confirm that the endpoint being accessed matches the token's scope, either private or public.
   3. If you operate within a private network, verify that you are using the private endpoints. An example of a private endpoint value is https://s3.private.us-south.cloud-object-storage.appdomain.cloud/.

3. Check network access controls

   Validate that network access policies, including context-based restrictions, allow the client to reach the necessary endpoints. To learn more, see Restricting access by network context.

   • If you use context-based restrictions (CBR) with Object Storage buckets, ensure that the source IP address, VPC subnet, or other attributes are permitted.
   • Validate that firewall rules or VPC access groups allow outbound access to Object Storage endpoints.

4. Perform manual validation to isolate the issue

   Manual validation can help you to isolate authorization issues from application-level misconfigurations. To perform a manual validation, use these steps:

   1. Obtain a new IAM token using a method appropriate for your task (for example, API Key or IAM authentication).
   2. Using cURL or another tool, manually send a request to the Object Storage endpoint.
   3. Validate that the expected response is returned without access errors.

To minimize the occurrence of 403 Access Denied errors, consider a regular review of the following items:

• Review IAM policies and assigned roles: Perform periodic audits of IAM policies to ensure that users, service IDs, and API keys have only the necessary permissions required for their operations.
• Audit context-based restrictions (CBR): Regularly review CBR rules to verify that valid sources, such as trusted IP ranges or VPC subnets, continue to have access to Object Storage endpoints because infrastructure changes over time.
• Monitor access logs and authorization events: Continuously monitor Object Storage access logs and IAM authorization logs for denied requests, anomalies, or unexpected access attempts that could indicate configuration issues or security risks.
• Update security practices and service configurations: Stay informed about the latest IBM Cloud Object Storage security enhancements and IAM best practices. See Monitoring notifications and status for options. Apply recommended updates and improvements to ensure compliance and optimal access control.