How to Resolve the "Invalid Signature" Error in Mattermost when requesting a Trial License

Problem

When attempting to request a trial license for your Mattermost server, you might encounter an error that looks like the following in the server logs:

"msg":"Invalid signature","caller":"utils/license.go:100","error":"crypto/rsa: verification error"

This error typically occurs while validating the digital signature of the license being applied to your Mattermost server. It indicates that the signature of the license file cannot be verified against the public key used by the Mattermost server, suggesting either a mismatch between the license file and the server's expectation or an issue with the server's configuration settings related to the Cloud Service (CWS).

Solution

To resolve the "crypto/rsa: verification error" when requesting a trial license for your Mattermost server, follow these steps, focusing on ensuring the correct configuration settings for the Cloud Service are applied:

1. Verify Configuration Settings: First, confirm that your config.json file contains the correct Cloud Service settings. The relevant section should look like this:

   {
       "CloudSettings": {
           "CWSURL": "https://customers.mattermost.com",
           "CWSAPIURL": "https://portal.internal.prod.cloud.mattermost.com",
           "CWSMock": false
       }
   }  

   These settings direct your Mattermost server to communicate with the correct Cloud Service endpoints for license verification and trial license requests.
2. Restart Mattermost Server: After verifying or updating your configuration settings, restart your Mattermost server to apply the changes. A restart is necessary for the server to reload its configuration and apply the new settings.
3. Request Trial License Again: With the correct settings in place and after restarting your Mattermost server, try requesting the trial license again. The server should now be able to communicate properly with the Cloud Service's endpoints, and the license verification should succeed.
4. Check Server Logs: If you encounter further issues, check the server logs again for any error messages. If the same error persists, it may indicate a deeper issue with the Cloud Service's response or with the Mattermost server's ability to process the license information.
5. Contact Support: If you're unable to resolve the issue following the above steps, consider reaching out to Mattermost Support for further assistance. Provide them with the error message and any relevant logs to help expedite the troubleshooting process.