Date: Fri, 05 Feb 2010 11:40:50 +0200 From: George Mamalakis <mamalos@eng.auth.gr> To: freebsd-stable <freebsd-stable@freebsd.org> Subject: Kerberized NFSv3 incorrect behavior Message-ID: <4B6BE7A2.6000402@eng.auth.gr>
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Dear all, I am running FBSD8-STABLE on an nfsv3 server and an nfsv3 client. My configuration is based on http://code.google.com/p/macnfsv4/wiki/FreeBSD8KerberizedNFSSetup. My goal is to share filesystems securely through kerberos authentication. Everything works fine, until I try to kdestroy my tickets or kinit to some other user, where the system insists to think that I am the user that initially obtained their ticket. To be more extensive, my story is as follows: nfs server: /etc/rc.conf: rpcbind_enable="YES" mountd_flags="-e" nfs_server_enable="YES" nfs_client_enable="YES" gssd_enable="YES" and the kernel is compiled with: options KGSSAPI device crypto my /etc/exports contains: /exports -alldirs -sec=krb5 nfs client: /etc/rc.conf: rpcbind_enable="YES" nfs_client_enable="YES" gssd_enable="YES" on both client and server the /etc/krb5.conf contains: [libdefaults] default_realm = EXAMPLE.COM [realms] EXAMPLE.COM = { kdc = kdc.example.com admin_server = kdc.example.com kpasswd_server = kdc.example.com } [domain_realm] kdc.example.com = EXAMPLE.COM .kdc.example.com = EXAMPLE.COM .example.com = EXAMPLE.COM example.com = EXAMPLE.COM and both client and server have the correct entries about each other (and themselves) in their /etc/hosts, so heimdal works just fine. Both client and server have their respective keytabs stored in /etc/krb5.keytab, and I use two users in my example (that both exist in both systems with the same uid,gid): mamalos and testakis. So, when I mount the exported filesystem on the client giving: # mount -o nvfsv3,sec=krb5 server.example.com:/exports /mnt # mount /dev/da0s1a on / (ufs, local, soft-updates) devfs on /dev (devfs, local, multilabel) server.example.com:/exports on /mnt (nfs) and try to access the share: # ls /mnt ls: mnt: Permission denied I get the error I am expecting, since root does not have any kerberos tickets assigned, yet. Let's see what happens when I kinit as mamalos: # klist Credentials cache: FILE:/tmp/krb5cc_0 Principal: mamalos@EXAMPLE.COM Issued Expires Principal Feb 5 11:20:49 Feb 5 21:20:47 krbtgt/EXAPMLE.COM@EXAMPLE.COM # ls -la /mnt/ total 8 drwxr-xr-x 4 root wheel - 512 4 Feb 19:03 ./ drwxr-xr-x 21 root wheel - 512 3 Feb 11:27 ../ drwx------ 2 mamalos wheel - 512 5 Feb 11:11 mamalos/ drwx------ 2 testakis wheel - 512 4 Feb 19:06 testakis/ # touch /mnt/mamalos/myfile # ls -la /mnt/mamalos/myfile rw-r--r-- 1 mamalos wheel - 0 5 Feb 11:22 /mnt/mamalos/myfile Which is the exact behavior that is expected. Now when I kdestroy: # kdestroy # klist klist: No ticket file: /tmp/krb5cc_0 # touch /mnt/mamalos/myfilethatshouldnotbe # ls -la /mnt/mamalos/myfilethatshouldnotbe -rw-r--r-- 1 mamalos wheel - 0 5 Feb 11:24 /mnt/mamalos/myfilethatshouldnotbe And I can do everything in that share as if I were still mamalos, even though I kdestroyed my kerberos ticket. The same thing will happen even if I kinit to testakis after that. klist shows testakis' ticket this time, but I am not allowed to access (rwx) tetakis' files/folders, and I still have full control over mamalos' files and folders. In order to be able to do something as testakis, I have to unmount the share and remount it while having testakis' ticket (or having no ticket at all, and giving kinit testakis after mounting the share). I am not an NFS expert, but I suppose that this behavior is not the one to be expected, except if I am missing some fundamental information about kerberized NFS that explains it. Even so, it would be quite unwise to behave so, since even if the users kdestroys their tickets, they have still all permissions as when they obtained their ticket. Thank you all in advance, looking forward to an answer, kind regards, mamalos -- George Mamalakis IT Officer Electrical and Computer Engineer (Aristotle Un. of Thessaloniki), MSc (Imperial College of London) Department of Electrical and Computer Engineering Faculty of Engineering Aristotle University of Thessaloniki phone number : +30 (2310) 994379
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