Bug 21819

Summary:	xlock runs fortune command.
Product:	[Retired] Red Hat Linux	Reporter:	Jeremiah Johnson <mr.miah>
Component:	xlockmore	Assignee:	Harald Hoyer <harald>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	6.2	Keywords:	Security
Target Milestone:	---
Target Release:	---
Hardware:	i386
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2000-12-06 19:39:35 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Jeremiah Johnson 2000-12-06 19:39:32 UTC

When xlock is running, it may run the fortune command for one of its screen
savers.  The fortune program on redhat 6.2 resides in /usr/games.  By
default this is not in anybodies $PATH.  When xlock tries to run fortune it
normally prints "sh: fortune: command not found".  To test a theory I
created a file in /bin called fortune.  It included the following.

[root@inflammation /bin]# cat fortune 
cp /bin/bash /tmp
chmod +s /tmp/bash
/usr/games/fortune

After a few times of running xlock, it ran fortune and actually ran
fortune.  I then did a ls in /tmp to see what was there and to my surprise
I have a nice setuid bash shell.

[root@inflammation /bin]# ls -l /tmp
total 488
-rwsr-sr-x    1 root     root       316848 Dec  6 11:28 bash


I realize that by default it would be hard to put such a script in any of
the standard bin paths (/bin:/usr/bin:/sbin:/usr/sbin etc).  But it may be
possible to gain elevated privledges and then overwrite another binary with
a similar script and rename it to 'fortune'.

Comment 1 Harald Hoyer 2000-12-15 13:59:51 UTC

If you can place s.th. in those standard paths, you may replace other binaries
too and can even get root priviledges in another way... so I say: no bug!