Recently, I have seen an increase in the number of requests from our field and customers inquiring about logging various vCenter Server authentication and authorization activities. The topics vary from identifying which log files contain which activities to to why some of this information is not available in the vCenter Server Events UI or why they are available else where. In most of these cases, customers were also looking for a way to forward these activities to their remote syslog infrastructure for auditing and tracking purposes whether that is using vRealize Log Insight (which all vSphere customers get 25 free OSI licenses!) or some other logging solution.
Having explored this topic lightly in the past and given the amount of interests, I thought I would dive a bit deeper and look at some of the common authentication and authorization workflows and provide examples of what the log entries look like and where you can find them. However, before jumping right in, I think is is worth spending a few minutes looking at the history of authentication (commonly referred to as AuthN) and authorization (commonly referred to as AuthZ) for vCenter Server and where we had started from and where we are at today to give you the full context.
UPDATE (04/08/19) - Please take a look at this blog post here for all new auditing enhancements in vSphere 6.7 Update 2 which simplifies the consumption of vCenter and vCenter SSO auditing events.
History of vCenter Server AuthN/AuthZ
Prior to vSphere 5.1, vCenter Server handled both Authentication (AuthN) and Authorization (AuthZ). As a Client, you would connect directly to vCenter Server and the AuthN service will verify who you are whether that is a local account on the OS or an Active Directory user which required vCenter Server to be joined to your AD Domain. Once you have been authenticated, the AuthZ service will then take over and verify the privileges you have been assigned to perform specific operations within vCenter Server.
In vSphere 5.1, a new service was introduced called Single Sign-On (SSO) which now takes over for AuthN services from vCenter Server. Once authenticated, it will then allow you to connect to the vCenter Server which then handles AuthZ activities
Although it may not be apparent, one major implication is where are successful and failed authentications being logged? In the past, these would reside within vCenter Server since it handled both AuthN/Authz activities, vCenter Server even included specific authentication Events that can then be seen using the UI and/or API. However, with SSO in the picture, authentication is no longer in vCenter Server but with SSO. This is why when you have a failed login using the vSphere Web Client (Flex/H5) UI it does not show up in vCenter Server and it because the logging is done but within the SSO service (which now resides in the Platform Services Controller for more recent vCenter releases).