Bug 4982 - New server security defaults (i.e. lanman auth = No) lead to deletion of the LM passwd hash on the very first login (to a recent version) from an OS/2 client
New server security defaults (i.e. lanman auth = No) lead to deletion of the...
Status: RESOLVED FIXED
Product: Samba 3.2
Classification: Unclassified
Component: User & Group Accounts
3.2.0
All OS/2
: P3 regression
: ---
Assigned To: Gerald (Jerry) Carter
Samba QA Contact
:
Depends on:
Blocks:
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Reported: 2007-09-19 21:31 UTC by Guenter Kukkukk
Modified: 2007-09-27 23:25 UTC (History)
3 users (show)

See Also:


Attachments
Set the smbpasswd backend to return "not implemented" for the update_login_account (1.57 KB, patch)
2007-09-27 18:39 UTC, Gerald (Jerry) Carter
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Description Guenter Kukkukk 2007-09-19 21:31:12 UTC
Hi all,

i post that here, so it's not getting lost. :-)

Most of the background info has already been posted - see:
http://lists.samba.org/archive/samba-technical/2007-September/055549.html

During handling of reply_sesssetup_and_X () the LM password hash is deleted,
so no further logins will succeed, until a new password is (manually) supplied.

Tried to debug that behaviour with my really very limited knowledge
of the 'whole samba auth specifics' - just somewhat followed and analysed the
call tree... and gave up after hours.

I see no easy solution to avoid the LM hash deletion - probably
a more experienced developer could.

Just some notes from abartlet on irc:

09/19/07  5:33:50 <abartlet> the issue is that once an OS/2 client accesses the server, it reads in the password, sets the lanman password to NULL (to ensure it is not used), then finds the client can't authenticate
09/19/07  5:34:08 <abartlet> so, it calls pdb_update_sam_account() to ensure updated 'bad password count' is written
09/19/07  5:34:22 <abartlet> which writes out the XXXX password
09/19/07  5:34:43 <abartlet> all of the steps make sense on their own, but in sequence, it kills your LM passwords

If no solution is found - that behaviour should be noted in the release notes!

In networks, where lanman auth clients are running,
   lanman auth = Yes
should be added *explicitly* to the [global] section of smb.conf
_before_ such a new samba version is installed and started!

Btw - also the implications of the new "client lanman auth = No" should
be described.

Cheers, Guenter
Comment 1 Andrew Bartlett 2007-09-20 23:19:45 UTC
This is a tricky one.  We need to have a way to update the bad password count (if we should count a disabled LM-only login as such) without calling pdb_update_sam_account().

Comment 2 Gerald (Jerry) Carter 2007-09-27 18:39:03 UTC
Created attachment 2932 [details]
Set the smbpasswd backend to return "not implemented" for the update_login_account

Please test.  Thanks.
Comment 3 Guenter Kukkukk 2007-09-27 22:24:17 UTC
Hi Jerry,

did test your patch against
  - passdb backend = smbpasswd
  - passdb backend = tdbsam
  - ??? (not tested)

All seems to work fine now!  :-)

The Lanman hash is no longer _deleted_ (!) - but the
legacy clients now get "access denied" (as expected) - which 
should be noted in the upcoming release notes!
Admins which have legacy clients inside their network should
now explicitely add
   lanman auth = Yes
to smb.conf!

Same with new default
  client lanman auth = No

Admins which have legacy _SERVERS_ inside their network should
now explicitely add
     client lanman auth = Yes
to smb.conf

Otherwise, all samba client tools - and mounting smbfs and cifs -
would not work anymore against legacy servers!

Cheers, Guenter
Comment 4 Gerald (Jerry) Carter 2007-09-27 22:50:06 UTC
(In reply to comment #3)
> Hi Jerry,
> 
> did test your patch against
>   - passdb backend = smbpasswd
>   - passdb backend = tdbsam
>   - ??? (not tested)
> 
> All seems to work fine now!  :-)

Cool.

> 
> The Lanman hash is no longer _deleted_ (!) - but the
> legacy clients now get "access denied" (as expected) - which 
> should be noted in the upcoming release notes!

Already there.