Yes, yes I know there are no real passwords or even hashes in that file on modern systems. However, I am quite curious if this is a good, easy way to totally lock down a system from everyone and what would break first. I don't have a spare system, but it sure sounds like a fun experiment. Has anyone tried this?
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This is pretty interesting from the point of view where you might want to build a system where your users are unable to lookup the usernames of other users.– paceyNov 9, 2010 at 17:44
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And according to pacey (below) also unable to lookup their own names as well!– AllenNov 9, 2010 at 19:48
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2 Answers
Just for you I tried it :-)
Any user will be able to login like normal. This is because login runs with root privileges. After being logged in the user won't have access to /etc/passwd which might cause problems with userland applications.
The first thing you might notice is that the shell cannot read your username which produce a prompt like
I have no name!@vs245042:~$
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+1 just for trying it for me. I'm surprised that your system wasn't totally borked. Does it really say "I have no name!" or are you just paraphrasing? Which distro/version did you try?– User1Nov 9, 2010 at 19:47
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I tried this on a Debian 4.0 machine with bash as login shell. It is not paraphrased it's copied from terminal.– paceyNov 9, 2010 at 20:27
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1Also, ls will only show UID and GID in numeric form. ~<username> won't expand either. Nov 10, 2010 at 3:11
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Wow. If you didn't know that someone did a chmod, how would you ever figure out what happened?– User1Nov 10, 2010 at 15:49
Setup an auditctl on /etc/passwd and see what tries to access it:
auditctl -w /etc/passwd -p war
Then afterwards analyse the output of:
ausearch -f /etc/passwd
See what's trying to access it, if it's all root processes then you're fine.
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1That's a cool idea. Is there a way to config
auditctlto only log non-root users?– User1Nov 9, 2010 at 21:07