On 24/01/16 15:50, Dag-Erling Smørgrav wrote:
Slawa Olhovchenkov <s...@zxy.spb.ru> writes:
Can you do some small discurs about ssh+kerberos?
I am try to use FreeBSD with $HOME over kerberoized NFS.
For kerberoized NFS gssd need to find cache file "called
/tmp/krb5cc_<uid>, where <uid> is the effective uid for the RPC
caller" (from `man gssd`).

sshd contrary create cache file for received ticket called
/tmp/krb5cc_XXXXXXX (random string, created by krb5_cc_new_unique). Is
this strong security  requirement or [FreeBSD/upstream] can be patched
(or introduce option) to use /tmp/krb5cc_<uid> as cache file for
received ticket?

I wasn't aware of that.  It should be easy to patch, but in the
meantime, you can try something like this in .bashrc or whatever:

krb5cc_uid="/tmp/krb5cc_$(id -u)"
if [ -n "${KRB5CCNAME}" -a "${KRB5CCNAME}" != "${krb5ccuid}" ] ; then
         if mv "${KRB5CCNAME}" "${krb5ccuid}" ; then
                 export KRB5CCNAME="${krb5ccuid}"
                 echo "Unable to rename krb5 credential cache" >&2
unset krb5ccuid

If $KRB5CCNAME is set during PAM session setup than the pam_exec module might allow a reliable implementation along those lines:

  - Stop if $KRBCCNAME is invalid (klist -t)
  - Stop if /tmp/krb5cc_$UID is already valid and has enough time left
  - Copy the ticket to /tmp and rename it to /tmp/krb5cc_$UID.

Keep in mind that this approach leaves valid tickets in /tmp after the SSH session ends while OpenSSH normally does its best to tie forwarded tickets to a SSH session.
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