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From: Andrew Bartlett on 22 Apr 2010 07:20
On Mon, 2010-04-19 at 16:46 +0200, Marcel Ritter wrote:
> Hi,
>
> during my tests to use Samba4 as a kdc for kerberized NFS,
> I found a bug in the KDC code, when generating a principal
> without pac (e.g. with msktutil and option --no-pac), that
> causes Samba4 to crash:
>
> Running the following command on one of the client machines
>
> msktutil -c --upn nfs/testa.linex.org -h testa.linex.org
> --computer-name testa-service-nfs --server s4-dc1.linex.org --no-pac
>
> results in this gdb backtrace on the samba4 dc (s4-dc1.linex.org):
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x00000000005e82e6 in samba_make_krb5_pac ()
> Current language: auto; currently asm
> (gdb) bt
> #0 0x00000000005e82e6 in samba_make_krb5_pac ()
> #1 0x00000000004ce243 in samba_wdc_get_pac ()
> #2 0x000000000059290b in _kdc_pac_generate ()
> #3 0x0000000000588055 in _kdc_as_rep ()
> #4 0x00000000005922ec in kdc_as_req ()
> #5 0x000000000059258e in krb5_kdc_process_krb5_request ()
> #6 0x00000000005fc1dc in kdc_process ()
> #7 0x00000000005fc4bb in kdc_tcp_call_loop ()
> ...
>
> Looking at the code, the error is quite easy to find:
>
> source4/kdc/wdc-samba4.c: krb5_error_code samba_wdc_get_pac()
> calls
>
> 1.) source4/kdc/pac-glue.c: samba_kdc_get_pac_blob()
>
> /* The user account may be set not to want the PAC */
> ...
> *_pac_blob = NULL;
>
> and then calls
>
> 2. source4/kdc/pac-glue.c: samba_make_krb5_pac()
> which tries to use uninitalized "pac_blob" and segfaults
>
>
> A simple patch is attached that solved the problem for me.

somehow, the patch didn't make it to the list. Can you make it with git
format-patch (if possible) and attach it to a bug, or mail it to me. I
would be delighted to include it in the tree, or otherwise fix this
bug.

(Sorry for the slow response, I normally expect Samba4 questions on
samba-technical during this alpha phase).

Thanks!

Andrew Bartlett

--
Andrew Bartlett http://samba.org/~abartlet/
Authentication Developer, Samba Team http://samba.org
Samba Developer, Cisco Inc.
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