Messages in this thread | | | Date | Thu, 30 Aug 2007 16:42:33 +0200 (CEST) | From | Jan Engelhardt <> | Subject | Re: NFS4 authentification / fsuid |
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On Aug 30 2007 10:29, Trond Myklebust wrote: >On Thu, 2007-08-30 at 16:12 +0200, Jan Engelhardt wrote: >> >> with NFS3, there is this 'root hole', i.e. any person who has a root >> account (perhaps by use of a laptop) can mount an export (let's say this >> export had the "root_squash" option), and still have a look at the user >> files, because he can locally setuid() into another user. >> >> So I was looking for alternatives. CIFS is my favorite candidate, but it >> has a few issues right now. So does sshfs and about everything I have >> come across. Since I remember NFS4 can use KRB5 authentification, my >> question is, will the NFS(4) server process run with an fsuid equal to >> the user that authenticated? > >NFSv3 should work fine with krb5 too, but that won't solve your problem >with setuid: kerberos saves the TGT in a file on /tmp, so root can still >suid and grab your cred (and the same goes for CIFS).
Hm? I do not see this problem with CIFS. The user may have local root, but on the server, he only has his non-root account on the server, and as such, can only operate on the server using this non-root fsuid. Did I miss something? (Especially the /dev/mem thing is not quite clear to me.)
>BTW: even when this task is done, a creative root can still find ways to >subvert the security (he can read /dev/mem, replace the kernel with a >compromised one, ....). The bottom line is that if you can't trust root, >don't even log in.
Jan -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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