oss-sec mailing list archives
utmp reliability?
From: Marcus Meissner <meissner () suse de>
Date: Thu, 14 May 2009 20:33:49 +0200
Hi, While debugging a problem for a customer of us I found that UTMP entries are not generated reliably and utmp entry creation starts to fail on higher loads/more users or more utmp activity. Reason is that glibc locks the UTMP file on write/read with a 1 second timeout, and if that 1 second timeout triggers no entry is written. Sadly without any indication of failure if you use login(3) or pututline(3). :( I am wondering if handling UTMP should be more reliable or if at least error reporting should happen. Making it reliable will make it possible to DoS any kind of logins / terminal opens of course, but make it easier on app writers using utmp. (Yes, I know the really reliable way is Audit, but this is not user readable.) Ciao, Marcus
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