Bug 65412 - wall(1) over-trusts utmp contents
wall(1) over-trusts utmp contents
Product: Red Hat Linux
Classification: Retired
Component: SysVinit (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Bill Nottingham
David Lawrence
: Security
Depends On:
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Reported: 2002-05-23 10:03 EDT by Matthew Kirkwood
Modified: 2014-03-16 22:27 EDT (History)
1 user (show)

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Fixed In Version:
Doc Type: Bug Fix
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Last Closed: 2002-06-12 01:26:23 EDT
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RHEL 7.3 requirements from Atomic Host:
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Description Matthew Kirkwood 2002-05-23 10:03:24 EDT
wall can be tricked into sending its messages to any file or device.

Try this:

1. Login on the tty1
2. Run:
   # sed 's%tty1%port%g' </var/run/utmp > ut2
   # mv ut2 /var/run/utmp
3. Reboot

Clearly, other programs should ensure that nobody can mess with utmp, but I
think that wall should be fixed to refuse to send messages to anything but a tty.
Comment 1 Bill Nottingham 2002-07-18 21:33:43 EDT
isatty() added in 2.84-5; thanks!

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