A couple weeks ago, the support desk where I work got a call about a user being unable to log into our system. We’ll call her Jane Doe. Jane could log into email, the campus network, ANYTHING except our student ‘portal’. Which is weird, because all those things authenticate against an Active Directory server.
Further, she was getting an unusual error message complaining about the LDAP mapping. The help desk took her through the usual troubleshooting steps - making sure she wasn’t mistyping her password, having her change her password, et cetera. But they got stymied, so they brought it to my attention.
I’m a database guy mainly, but I also do some software administration, and a little development. (We’re a small shop, we all wear a lot of hats.) So I take a look at it.
We sometimes see the LDAP message if there’s a defect with a student’s record in a particular table in our student information database. So that’s where I go first - and everything looks good. If our students change their password through the ‘portal’, then I (as DBA) can see those passwords for about a week afterwards in another table, so I looked her up, got her password, and tried her login myself.
It worked.
No error whatsoever. To my mind, that confirmed that the behind the scenes software was working correctly, that the user was either making a mistake, or had some local computer configuration problem. I tried her login from a PC set up to come into our network from the outside, like hers - still worked. We got her to try it on a different PC - still didn’t work for her. She even gave her sister her login information - and her SISTER was able to get in successfully.
So it seemed the problem was with the user. But I couldn’t think of what she could do to get THAT message - she should get ‘invalid username or password’ if she mistyped something. We verified her password didn’t contain any special characters that might trip up authentication - just letters and numbers.
So the helpdesk started trying to look for any malware that might be tripping her up on her home PCs, and I went on to think about other work, until today. One of our network guys was talking about an unrelated issue while within earshot of my office, and mentioned case-sensitivity - which gave me the lightbulb.
I’d considered her getting the case sensitivity wrong on her password, but what about her username? Our assigned usernames only use lowercase letters. AD won’t care about the capitalization, but since it has to compare to a string value in an Oracle table to do the matching - that could cause what we’re seeing. I quickly verified by trying my own login credentials, with the first letter of my username capitalized.
Bingo!
Some days, I love my job. 
