sudo login cache is retained even after user logs out

[StephanBeal]

When running sudo 2x in a short period, the second attempt uses cached credentials. That's all fine and good, but watch this:

[stephan@cheyenne:~/tmp]$ ssh imat-dev
stephan@infomat-dev:~$ sudo su -
root@infomat-dev:~#

Summary:

a) i sudo'd to root. i was asked for a password, as expected.
b) i finished my work and logged out from root, then logged off of the remote system.
c) A few moments later i logged in again to the remote system and did 'sudo su -'.
d) i expected to be asked for my password, but the old credentials from my _previous_ login were reused.

IMO the credentials should be invalidated if the user logs out. The current behaviour is highly questionable. i would rather it not cache at all than to keep the cache valid after i log out.

ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: sudo 1.7.2p7-1ubuntu2.1
ProcVersionSignature: Ubuntu 2.6.35-28.50-generic 2.6.35.11
Uname: Linux 2.6.35-28-generic x86_64
NonfreeKernelModules: fglrx
Architecture: amd64
Date: Tue Jun 28 15:45:13 2011
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release amd64 (20101007)
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: sudo

[Marc Deslauriers (mdeslaur)]

Thanks for taking the time to report this bug and helping to make Ubuntu better. This is not a bug, but rather expected behavior:
https://wiki.ubuntu.com/SecurityTeam/FAQ#Sudo

Please feel free to report any other bugs you may find.

[Alex (chewytree)]

sudo is designed to keep a "ticket" valid for 15 minutes after you use your password the first time. This is configurable.

Please read man sudoers:

timestamp_timeout
    Number of minutes that can elapse before sudo will ask
    for a passwd again. The default is 15. Set this to 0
    to always prompt for a password. If set to a value
    less than 0 the user’s timestamp will never expire.
    This can be used to allow users to create or delete
    their own timestamps via sudo -v and sudo -k respec‐
    tively.

[StephanBeal (sgbeal)]

i understand that the behaviour of having a timeout is expected (i wrote that in my ticket). What's not expected is that even though i log out, the cache remains valid.

[Micah Gersten (micahg)]

This was actually fixed in natty as 1.7.3 enabled clearing the catch on logout for pseudo ttys with per tty tickets enabled and 1.7.4 enabled per tty tickets by default.

[StephanBeal (sgbeal)]

Fair enough.

Bad for me, though - i back-rev'd from natty to maverick because natty completely destroyed my productivity (but that's another story for another forum).