[Bug 676525] Re: mount.cifs cannot mount with kerberos

[Penelope Fudd]

I think I see the source of the problem....

When I do this:

# sudo strace -fo/tmp/a -p $$ &
# sudo mount -t cifs -o username=me,rw,uid=me,gid=mygroup,port=445,sec=krb5,creduid=/tmp/krb5cc_1000 \\\\server.example.com\\home\\me /mnt/me
mount error(22): Invalid argument
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)
# kill %1
# grep krb5cc /tmp/a
8619  access("/tmp/krb5cc_1000", R_OK) = 0
8619  open("/tmp/krb5cc_1000", O_RDONLY) = 3
# grep ' mount(' /tmp/a
8618  mount("\\\\server.example.com\\home\\me", ".", "cifs", 0, "ip=1.2.3.4,unc=\\\\server.example."...) = -1 EINVAL (Invalid argument)
# dmesg | grep CIFS
[ 4634.121902] CIFS: Unknown mount option "creduid=/tmp/krb5cc_1000"

When I don't used 'creduid=', the mount command returns:
   mount error(126): Required key not available
   Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)
and the strace output shows that it doesn't try accessing /tmp/krb5cc_* at all.

When I instead try 'cruid=1000', the same error occurs, and again, no
/tmp/krb5cc_* files are being accessed.

In short, I think that either the cifs kernel module needs to allow the
creduid option, or the mount.cifs program needs to strip it out before
calling mount().  After that, I don't know what else has to happen;
perhaps both creduid= and cruid= need to be specified?  Or perhaps
creduid= needs to be renamed to kccf= (kerberos cached credentials file,
a name pulled out of a hat)?

Hopefully someone finally makes cifs+kerberos work from /etc/fstab or
/etc/pam.d so that it can be mounted when I log in, without having to
enter my password again.

Thanks!

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https://bugs.launchpad.net/bugs/676525

Title:
  mount.cifs cannot mount with kerberos

Status in cifs-utils package in Ubuntu:
  Confirmed

Bug description:
  Binary package hint: cifs-utils

  Please tell me if this is the wrong channel.  I have put this in the
  ubuntu forum with no reply here:

  http://ubuntuforums.org/showthread.php?t=1623107

  From the thread:

  mount.cifs used to be able to work with kerberos tickets so long as I
  changed the binary to suid root. I understand why this may have fallen
  out of favour but since Meerkat, I am unable to get mount.cifs to
  mount using kerberos and sudo.

  # Non sudo mount.cifs with/without suid root
  $ mount.cifs //server/share/directory ~/central -o sec=krb5
  mount.cifs: permission denied: no match for /home/CauserC/central found in /etc/fstab

  # Sudo mount.cifs with/without suid root
  $ sudo mount.cifs  //server/share/directory ~/central -o sec=krb5
  mount error(126): Required key not available

  I do definitely have a kerberos ticket, and both klist and "sudo
  klist" show it to me.

  Now, it does work if I do a "sudo kinit $USERNAME." Then a sudo
  mount.cifs mounts the share no problem. This is obviously less than
  ideal because it involves typing in a password again, and subsequent
  non sudo klists result in:

  $ klist
  klist: Credentials cache permissions incorrect while setting cache flags (ticket cache FILE:/tmp/krb5cc_10009_8ZePnt)

  I'm tempted to file this as a bug report but wanted to check in here
  first to make sure that I'm not doing anything stupid. As I say, I
  never tried this in Lucid as suid root worked fine.

  Any help appreciated

  Chris

  ProblemType: Bug
  DistroRelease: Ubuntu 10.10
  Package: smbfs 2:4.5-2
  ProcVersionSignature: Ubuntu 2.6.35-22.35-generic-pae 2.6.35.4
  Uname: Linux 2.6.35-22-generic-pae i686
  NonfreeKernelModules: nvidia
  Architecture: i386
  Date: Wed Nov 17 15:20:14 2010
  InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100429)
  ProcEnviron:
   PATH=(custom, user)
   LANG=en_GB.UTF-8
   SHELL=/bin/bash
  SourcePackage: cifs-utils

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