Giorgos Keramidas wrote:
On 2006-03-04 09:00, Kovesdan Gabor <[EMAIL PROTECTED]> wrote:
Giorgos Keramidas wrote:
On 2006-03-04 00:44, Kovesdan Gabor <[EMAIL PROTECTED]> wrote:
Hello,
look at this:
[EMAIL PROTECTED] w
12:41AM up 82 days, 10:05, 0 users, load averages: 0.00, 0.00, 0.00
USER TTY FROM LOGIN@ IDLE WHAT
[EMAIL PROTECTED]
Where am I? :) I don't know exactly how it happened, but I'll
investigate, I have an idea and I'll report if I find out.
Some programs may tweak wtmp to `hide' users that are actively logged
in. One program that I know can do this is screen(1). Hitting ``^A L''
here, between successive `w' invocations, I can see this:
[EMAIL PROTECTED]:/root# w
2:04AM up 2:10, 1 user, load averages: 0.07, 0.16, 0.19
USER TTY FROM LOGIN@ IDLE WHAT
[EMAIL PROTECTED]:/root# w
2:05AM up 2:11, 2 users, load averages: 0.03, 0.14, 0.17
USER TTY FROM LOGIN@ IDLE WHAT
root pts/0 :0:S.0 2:05AM - w
[EMAIL PROTECTED]:/root#
And what do the other logged in users see?
Only what `w' can see too.
With my method I can completely hide, nobody can see me logged in.
What is your method? I haven't seen any description of how *you* ended
up not being logged in. Are you using screen(1) or another program that
tweaks /var/log/wtmp? Which program? Have you found out why your login
seems record in wtmp was marked as logged out?
Here's my method:
http://www.freebsd.org/cgi/query-pr.cgi?pr=94060
So I think it might be an opportunity to abusing. I'll send a PR soon,
I just wanted to know before if somebody already knows about this
trick.
I don't think this is a bug. The permissions of ``/var/log/wtmp'' are:
$ ls -ld /var/log/wtmp
-rw-r--r-- 1 root wheel - 8052 Mar 4 16:51 /var/log/wtmp
What a bug about this would report is that set-user-id programs, like
screen(1), can do all sorts of nasty things if abused. This isn't
exactly a bug, but common knowledge.
- Giorgos
/bin/login is suid, too. Can't screen and login be modified somehow to
take care of this issue?
Gabor Kovesdan
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