Occam’s razor – it is futile to do with more things that which can be done with fewer – is colloquially rendered as “the simplest solution is the most likely”. We had multiple tickets opened today for authentication failures on an Apache web server. Each malfunctioning site uses LDAP authentication and authorization against an Oracle Unified Directory. Nothing in the error logs. The service account from the Apache configuration can log in and query the directory from the box using ldapsearch, so the account is valid and there is nothing in the OUD preventing access from this particular host.
That’s a puzzler, and I was about to take down a lot of web sites to reload the service with its log level set to debug. Not even sure what made me do it, but I went out to the groups and looked at their member lists. Oops. Something had gone wrong with the identity management platform and employee accounts had been cleared from the groups (all of the contractors were still members, which made it even stranger). Added a few people back into groups appropriate for their position, voila they could log into their site again.
No idea how the identity management group restored the memberships, but verifying people who should have been members (who had been members and had done nothing to remove their memberships) were actually members of the group saved a lot of time running through debug logs. Sometimes the simplest answer is the most likely.