how to mount shares as a user without mount.cifs setuid
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From: Jeff Layton on 8 Apr 2010 07:30 On Thu, 8 Apr 2010 00:45:20 -0400 Chris Smith <smb_77(a)chrissmith.org> wrote: > On Wed, Apr 7, 2010 at 9:39 PM, Jeff Layton <jlayton(a)samba.org> wrote: > > Yes, we added a patch a while back to make it such that mount.cifs > > would not allow itself to run as a setuid root program unless it that > > check was compiled out. > > > > This was done due to a rather constant stream of "security issues" that > > were brought about when people installed mount.cifs setuid root. Since > > it had never been vetted for security, we really had no other choice to > > communicate that installing it setuid root was unsafe. > > Not the place for it so the inquiry is only rhetorical. > How can you equate adding a patch preventing a sysadmin from using an > app as designed to communicating? Communication is one thing, > handcuffs are another. > Our hand was forced. After repeatedly telling people who were installing it setuid root "don't do that", we continued to get CVE's reported from people who continued to use it that way and expected us to treat the problem as a security issue. Our fix was somewhat heavy-handed, but we absolutely had to make it clear that it wasn't safe to install mount.cifs in that fashion. The patch to remove that check was trivial (simply change one #define in the code), but required the person building the program to consciously override our warnings. The Debian package maintainer wisely chose not to do so. In any case, the point is somewhat moot now. The current mount.cifs that ships in cifs-utils no longer prevents installation as a setuid root program. -- Jeff Layton <jlayton(a)samba.org> -- To unsubscribe from this list go to the following URL and read the instructions: https://lists.samba.org/mailman/options/samba
From: Nico Kadel-Garcia on 8 Apr 2010 08:00 On Thu, Apr 8, 2010 at 12:45 AM, Chris Smith <smb_77(a)chrissmith.org> wrote: > On Wed, Apr 7, 2010 at 9:39 PM, Jeff Layton <jlayton(a)samba.org> wrote: >> Yes, we added a patch a while back to make it such that mount.cifs >> would not allow itself to run as a setuid root program unless it that >> check was compiled out. >> >> This was done due to a rather constant stream of "security issues" that >> were brought about when people installed mount.cifs setuid root. Since >> it had never been vetted for security, we really had no other choice to >> communicate that installing it setuid root was unsafe. > > Not the place for it so the inquiry is only rhetorical. > How can you equate adding a patch preventing a sysadmin from using an > app as designed to communicating? Communication is one thing, > handcuffs are another. It doesn't stop a sysadmin. Sysadmins have root privileges and do not need setuid for this. Sysadmins can also manipulate automount or /etc/fstab to allow far more controlled mounting. This isn't "handcuffs". It's a seatbelt. -- To unsubscribe from this list go to the following URL and read the instructions: https://lists.samba.org/mailman/options/samba
From: Jeff Layton on 8 Apr 2010 08:20 On Thu, 08 Apr 2010 00:37:30 -0400 Gary Dale <garydale(a)rogers.com> wrote: > Jeff Layton wrote: > > On Wed, 07 Apr 2010 16:44:47 -0400 > > Gary Dale <garydale(a)rogers.com> wrote: > > > > > >> I'm running Debian/Squeeze on an AMD64 system. For some reason they have > >> recently stopped shipping mount.cifs with the setuid bit set. > >> > > > > That would be because it was horribly unsecure. > > > > > >> Now it > >> appears that they have changed the internal settings to prevent it from > >> running setuid. This means that I can't define the share in fstab with > >> "user" and connect from my Linux user account. Mounting smb/cifs shares > >> seems to be blocked except for root. > >> > >> > > > > Yes, we added a patch a while back to make it such that mount.cifs > > would not allow itself to run as a setuid root program unless it that > > check was compiled out. > > > > This was done due to a rather constant stream of "security issues" that > > were brought about when people installed mount.cifs setuid root. Since > > it had never been vetted for security, we really had no other choice to > > communicate that installing it setuid root was unsafe. > > > > > >> Presumably this has been done for security reasons. However, I can't > >> currently do much with my network shares unless I'm root because the > >> shares and all the files are owned by root:root. This is despite the > >> fstab setting username=<my windows account name> and I get prompted for > >> the password. That only seems to be used for connecting to the share, > >> not for the permissions. > >> > >> My Debian box hasn't joined a domain - I'm just using local accounts. I > >> mainly have the domain for some Windows boxes used by my family. > >> > >> How do I mount an smb/cifs share as a normal user without running > >> mount.cifs? Or if I have to mount the share as root, how can I get > >> reasonable access to the shares? > >> > >> > > > > You need to set the uid=/gid= options when mounting. When it's run by a > > non-root user, /bin/mount adds these options automatically. > > > Except that when I run mount as a non-root user, I get the error about > mount.cifs not being setuid. This is generated from the user option in > fstab. If I remove the user option, I am told that only root can mount > the share. Thus my problem that normal users cannot mount smbfs/cifs > shares. This appears to be reserved now only for root. > Sorry, I should have been more clear. The uid=/gid= options will just fix the ownership issues if you do the mount as root. It won't allow the mount to be performed by a non-privileged user. > > It's also worthwhile to note that I've recently re-enabled the ability > > to run mount.cifs as a setuid root program in the latest cifs-utils > > release: > > > > http://linux-cifs.samba.org/cifs-utils/ > > > > ...you may want to switch to using that instead if you need the ability > > to use mount.cifs in this way. > > > I would except that Debian/Squeeze has its own repositories that I'd > prefer to stick with. Hopefully they'll catch up shortly. > > While the ability to run mount.cifs setuid again is appreciated, how > does that fit in with the "horribly unsecure" reasoning that led to it > being removed? The code has been substantially reworked and should be far safer than it was previously. It does privilege separation now such that the bulk of the mount process is performed as an unprivileged user, and if linked against the right libs, with capabilities pruned to the minimum. At this point, I'd say it's safe enough that we no longer need to restrict it from being installed setuid root. As always, you should weigh carefully whether to do so in your own environment and packages. FWIW, I have no plans to make the Fedora cifs-utils package install mount.cifs setuid root. Part of the reason for that is that no one has requested it. -- Jeff Layton <jlayton(a)samba.org> -- To unsubscribe from this list go to the following URL and read the instructions: https://lists.samba.org/mailman/options/samba
From: Gary Dale on 8 Apr 2010 12:10 Nico Kadel-Garcia wrote: > On Thu, Apr 8, 2010 at 12:45 AM, Chris Smith <smb_77(a)chrissmith.org> wrote: > >> On Wed, Apr 7, 2010 at 9:39 PM, Jeff Layton <jlayton(a)samba.org> wrote: >> >>> Yes, we added a patch a while back to make it such that mount.cifs >>> would not allow itself to run as a setuid root program unless it that >>> check was compiled out. >>> >>> This was done due to a rather constant stream of "security issues" that >>> were brought about when people installed mount.cifs setuid root. Since >>> it had never been vetted for security, we really had no other choice to >>> communicate that installing it setuid root was unsafe. >>> >> Not the place for it so the inquiry is only rhetorical. >> How can you equate adding a patch preventing a sysadmin from using an >> app as designed to communicating? Communication is one thing, >> handcuffs are another. >> > > It doesn't stop a sysadmin. Sysadmins have root privileges and do not > need setuid for this. Sysadmins can also manipulate automount or > /etc/fstab to allow far more controlled mounting. > > This isn't "handcuffs". It's a seatbelt. > I'm not sure I can agree with you on that. When I setuid to allow a user to mount their own shares, they can do it. If I set up fstab to mount shares as root using specific uid and gid values, then the users don't see their correct permissions. That's a straightjacket, not a seatbelt. Now perhaps I'm missing something, but I have no trouble with users mounting nfs shares. The idea that users can't mount cifs shares strikes me as odd and an unnecessary impediment. -- To unsubscribe from this list go to the following URL and read the instructions: https://lists.samba.org/mailman/options/samba
From: Christian PERRIER on 8 Apr 2010 14:00
Quoting Gary Dale (garydale(a)rogers.com): > Now perhaps I'm missing something, but I have no trouble with users > mounting nfs shares. The idea that users can't mount cifs shares > strikes me as odd and an unnecessary impediment. How about turning the binary we provide in Debian to setuid on the systems where you want it to be this way, by using dpkg-statoverride(8)? -- To unsubscribe from this list go to the following URL and read the instructions: https://lists.samba.org/mailman/options/samba |