Date: Fri, 17 Dec 2004 09:53:15 -0500 From: Bill Vermillion <bv@wjv.com> To: freebsd-security@freebsd.org Subject: Re: Strange command histories in hacked shell history Message-ID: <20041217145315.GB68582@wjv.com> In-Reply-To: <20041217120138.7A89116A4D2@hub.freebsd.org> References: <20041217120138.7A89116A4D2@hub.freebsd.org>
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> Message: 1 > Date: Thu, 16 Dec 2004 20:31:05 +0800 > From: Ganbold <ganbold@micom.mng.net> > Subject: Strange command histories in hacked shell server Just a minor comment on one portion of your message. [All deleted except the pertinent part - wjv] > Machine is configured in such way that everyone can create an account itself. > Some user dir permissions: > ... > drwxr-xr-x 2 root wheel 512 Mar 29 2004 new > drwx------ 3 tamiraad unix 512 Apr 9 2004 tamiraad > drwxr-xr-x 6 tsgan tsgan 1024 Dec 16 17:51 tsgan > drwx------ 4 tugstugi unix 512 Dec 13 20:34 tugstugi > drwxr-xr-x 5 unix unix 512 Dec 13 12:37 unix > ... > User should log on as new with password new to create an account. > Accounting is enabled and kern.securelevel is set to 2. Only one > account 'tsgan' is in wheel group and only tsgan gan become root > using su. I've asked others before and never got a real answer on the design of 'su' which to my way of thinking has a security hold that shold be fixed. su checks the EUID of the user to see if they are in 'wheel' to enable them to su to root. It would seem to me it should use the UID. In your case if the 'tsgan' account does not have a secure password, and some breaches the 'tsgan' account in any manner, such as a SUID tsgan as I see it, then that user who cracked the 'tsgan' account can su to root. So in your case there is the possibility that someone else su'ed to 'tsgan' and then su'ed to root. Can anyone explain why su does not use the UID from the login instead of the EUID ? It strikes me as a security hole, but I'm no security expert so explanations either way would be welcomed. Bill -- Bill Vermillion - bv @ wjv . com
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