Date: Wed, 10 Feb 1999 11:22:44 -0600 From: Dan Nelson <dnelson@emsphone.com> To: Philippe CASIDY <pcasidy@worldnet.fr> Cc: gjb@comkey.com.au, freebsd-questions@FreeBSD.ORG Subject: Re: Mounting CDROM (or removable media) by users Message-ID: <19990210112243.A47243@dan.emsphone.com> In-Reply-To: <199902101635.RAA03064@greatoak.home>; from "Philippe CASIDY" on Wed Feb 10 17:35:55 GMT 1999 References: <19990210001221.19077.qmail@alpha.comkey.com.au> <199902101635.RAA03064@greatoak.home>
next in thread | previous in thread | raw e-mail | index | archive | help
In the last episode (Feb 10), Philippe CASIDY said: > You example is not very revelant because you are comparing two > different system and it is very easy to find a workaround. Anyway, I > like the sudo feature because as far as I understand, you can easily > choose who can or cannot mount a device. > > I just want to know what is the technical reason why by default, only > root can mount the cdrom. Because an unscrupulous user could insert a CDrom with a setuid-root sh binary and become root, or they could create a character device with [major,minor] of [2,1] (i.e. /dev/kmem) with world-write permissions, and become root by twiddling the kernel memory. Or they could insert a cdrom/floppy with an intentionally invalid filesystem on it and panic the system. If you limit mount() access to people who are already root, this isn't a problem. You could alter the mount() syscall to force "noexec, nosuid, nodev" whenever a non-root user tries to mount anything, but don't come running to us when he goes and mounts a cdrom on top of /bin or /tmp or something :) The best solution to the "user wants to mount a floppy/cdrom" problem is make a sudo wrapper that mounts a device in a predetermined place, with the noexec, nosuid, and nodev flags turned on, and provide a separate wrapper for unmounting. -Dan Nelson dnelson@emsphone.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?19990210112243.A47243>