[Samba] Pam_mount not working with "sec=krb5"

Ole Traupe ole.traupe at tu-berlin.de
Tue Nov 3 16:18:44 UTC 2015

Am 03.11.2015 um 16:44 schrieb buhorojo:
> On 03/11/15 10:56, Ole Traupe wrote:
>>>> I mean, putting the key in the keytab looks like a security risk to 
>>>> me.
>>> In what way does it appear any more of a risk than having the keys 
>>> which you have there already? Even if someone steals the keytab, 
>>> they're gonna be hard pressed to crack the key in the few hours 
>>> before the tgt expires. Do you have very sensitive data maybe?
>> Ok. And maybe I misunderstood something: I thought the key would be 
>> valid indefinitely, while the ticket expires. But then there is the 
>> Ticket-Granting-Ticket (TGT). And if also the TGT expires after a few 
>> hours, for how long will a share mounted with "sec=krb5,multiuser" be 
>> accessible to the user?
> Hi
> The upcall will maintain the validity of the mount for as long as it 
> is accessed, so maybe a better question would be how long a ticket 
> does your kdc issue for a user. The latter will be the determining 
> factor, not the upcall.

Up to 7 days if renewed within 24h, if I understand correctly 
(ticket_lifetime = 24h,  renew_lifetime = 7d).

Thanks for the clarification!

>> I am sorry for all these dummy questions, but I really find this 
>> matter hard to understand.
>> Thank you very much for your help!
>>>> Would be nice if you could use kerberos on the fly.
>>> You _are_ using it on the fly.The tgt is obtained without any 
>>> interaction on the part of the user.
>>>> Unfortunately, I don't find such a detailed log in /var/log/messages.
>>>>>> Also, if the user is not mounting his home share, but somebody 
>>>>>> else, this _other_ user will be the owner of newly created files 
>>>>>> and folders, right
>>>>> No. With multiuser, acl and permissions are respected. If the user 
>>>>> would normally be the owner of newly created files, then he will 
>>>>> be also over cifs.
>>>> Great, that sounds exactly as I would like it to be.
>>>>> One other thing, you need a recent version of cifs utils (we don't 
>>>>> think Centos has) 
>>>> Mine is cifs-utils.x86_64    4.8.1-20.el6
>>> We can confirm it works with 6.2.
>>> HTH
>> Thanks. So migrating the server to CentOS 7 would be advised here if 
>> one is afraid of bad interactions of Samba 3.1 with later (and 
>> potentially buggy) experimental cifs-utils versions for CentOS 6.
> We think that the only way with cifs on Centos is to get the source 
> and build it. If the rest of it is working but the upcalls are not 
> then keep with what you have, uninstall the cifs utils making sure the 
> binaries have been removed and are not at a non-standard location, 
> then make install.

So there will be no conflict with other samba components such as in 

And sorry for the typo, it is Samba 3.6.

> Good luck and HTH

Again, thank you very much!

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