Azure automation error “Client assertion contains invalid signature” – Time to renew your Automation account certificate

I was just recently playing with some Azure runbooks and noticed that one of my automation accounts, that I had selected to execute some of that automation, wasn’t working properly.

I had a Virtual Machine scheduled to boot at a specific time and that wasn’t happening. So this was what I did to troubleshoot it.

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In the Azure Portal, I went to “All Resources”, filtered by “Automation Accounts” and clicked in the Automation Account that was supposed to be running that runbook.

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I was able to immediately see that something wasn’t OK, as you can see above the automation account is showing that the certificates for both the “Run as Account” and the “Classic Run As Account”, are expired. Nevertheless, the job statistics is telling me that 4 jobs were ran and all with success. Odd, right? So lets investigate further.

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In the Automation Account menu I went to Process Automation > Jobs, to try and understand what jobs were executed. As you can see the 4 jobs are there, but were they executed with success?

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I clicked in one of the jobs. The status was “completed” but browsing to the “Errors” tab you could easily see it failed. “Client assertion contains an invalid signature” was the error.

So lets jump to the quick fix. Renew the automation account certificates.

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Back to the automation account > overview page, clicked in the link to resolve the issue and renewed both certificates.

And that’s it, problem solved.

Lessons learned: make sure your automation account is functional and don’t always trust the job statistics shown in the portal.