[SSSD] [PATCH] Do not try to set password when authtok_length is zero

Ondrej Kos okos at redhat.com
Wed Jul 17 17:17:13 UTC 2013


On 07/17/2013 06:47 PM, Jakub Hrozek wrote:
> On Wed, Jul 17, 2013 at 02:04:16PM +0200, Ondrej Kos wrote:
>> On 07/16/2013 08:10 PM, Jakub Hrozek wrote:
>>> On Tue, Jul 09, 2013 at 11:15:09PM +0200, Jakub Hrozek wrote:
>>>> On Fri, Jun 28, 2013 at 02:23:01PM +0200, Lukas Slebodnik wrote:
>>>>> On (24/06/13 17:04), Ondrej Kos wrote:
>>>>>> The problem here wasn't in returned error code, but in faultly read
>>>>>> DBUS message, due to condition in sss_authtok_set_string.
>>>>>>
>>>>>> When password is empty, it passes 0 as length, which is
>>>>>> misinterpreted, and the function tries to determine the length of
>>>>>> string by itself, reaching over boundaries of authtok string.
>>>>>>
>>>>>> trac issue: https://fedorahosted.org/sssd/ticket/1814
>>>>>>
>>>>>> Patch is attached
>>>>>>
>>>>>> Ondra
>>>>>
>>>>> We found out that it is right approach (after long discussion :-)
>>>>>
>>>>> ACK
>>>>
>>>> The approach might be good but on entering a blank password I'm getting
>>>> "System Error" with this patch, while without the patch I was getting
>>>> "Authentication failure". PAM_AUTH_ERR is the correct return code for
>>>> this use case.
>>>
>>> Hi,
>>>
>>> Ondra asked me to re-test atop the current git HEAD. Here is what I see
>>> when I type "su - jhrozek" and then just type "Enter":
>>>
>>> [sssd[be[redhat.com]]] [be_pam_handler] (0x0100): Got request with the following data
>>> [sssd[be[redhat.com]]] [pam_print_data] (0x0100): command: PAM_AUTHENTICATE
>>> [sssd[be[redhat.com]]] [pam_print_data] (0x0100): domain: redhat.com
>>> [sssd[be[redhat.com]]] [pam_print_data] (0x0100): user: jhrozek
>>> [sssd[be[redhat.com]]] [pam_print_data] (0x0100): service: su-l
>>> [sssd[be[redhat.com]]] [pam_print_data] (0x0100): tty: pts/20
>>> [sssd[be[redhat.com]]] [pam_print_data] (0x0100): ruser: jhrozek
>>> [sssd[be[redhat.com]]] [pam_print_data] (0x0100): rhost:
>>> [sssd[be[redhat.com]]] [pam_print_data] (0x0100): authtok type: 0
>>> [sssd[be[redhat.com]]] [pam_print_data] (0x0100): newauthtok type: 0
>>> [sssd[be[redhat.com]]] [pam_print_data] (0x0100): priv: 0
>>> [sssd[be[redhat.com]]] [pam_print_data] (0x0100): cli_pid: 22305
>>> [sssd[be[redhat.com]]] [krb5_pam_handler] (0x1000): Wait queue of user [jhrozek] is empty, running request immediately.
>>> [sssd[be[redhat.com]]] [krb5_auth_send] (0x0020): Wrong authtok type for user [jhrozek]. Expected [1], got [0]
>>> [sssd[be[redhat.com]]] [check_wait_queue] (0x1000): Wait queue for user [jhrozek] is empty.
>>> [sssd[be[redhat.com]]] [be_pam_handler_callback] (0x0100): Backend returned: (0, 4, <NULL>) [Success]
>>> [sssd[be[redhat.com]]] [be_pam_handler_callback] (0x0100): Sending result [4][redhat.com]
>>> [sssd[be[redhat.com]]] [be_pam_handler_callback] (0x0100): Sent result [4][redhat.com]
>>>
>>>
>>> 4 == System Error
>>> _______________________________________________
>>> sssd-devel mailing list
>>> sssd-devel at lists.fedorahosted.org
>>> https://lists.fedorahosted.org/mailman/listinfo/sssd-devel
>>>
>>
>> Hi,
>>
>> Now I see what you meant, new patches rebased on top of current master are
>> attached.
>>
>> The third patch replaces mutiple calls of sss_authtok_get_type with variable
>> and single call, just a small refactoring.
>>
>> Ondra
>>
>> --
>> Ondrej Kos
>> Associate Software Engineer
>> Identity Management - SSSD
>> Red Hat Czech
>
> [PATCH 1/3] Do not try to set password when authtok_length is zero
> Ack
>
>>  From 3968df17f835a8dac892b3756f2a4f35a86a0baa Mon Sep 17 00:00:00 2001
>> From: Ondrej Kos <okos at redhat.com>
>> Date: Wed, 17 Jul 2013 13:42:57 +0200
>> Subject: [PATCH 2/3] KRB: Handle empty password gracefully
>>
>> https://fedorahosted.org/sssd/ticket/1814
>>
>> Return authentication error when empty password is passed.
>> ---
>>   src/providers/krb5/krb5_auth.c | 13 +++++++++++++
>>   1 file changed, 13 insertions(+)
>>
>> diff --git a/src/providers/krb5/krb5_auth.c b/src/providers/krb5/krb5_auth.c
>> index 22495f57079d979b6c3484acf916ecc0736292d1..5b4d4abb6c9f97cac394853d73eb4e5f8b045c44 100644
>> --- a/src/providers/krb5/krb5_auth.c
>> +++ b/src/providers/krb5/krb5_auth.c
>> @@ -495,6 +495,19 @@ struct tevent_req *krb5_auth_send(TALLOC_CTX *mem_ctx,
>>           case SSS_PAM_AUTHENTICATE:
>>           case SSS_PAM_CHAUTHTOK:
>>               if (sss_authtok_get_type(pd->authtok) != SSS_AUTHTOK_TYPE_PASSWORD) {
>> +                /* handle empty password gracefully */
>> +                if (sss_authtok_get_type(pd->authtok) == SSS_AUTHTOK_TYPE_EMPTY &&
>> +                    sss_authtok_get_size(pd->authtok) == 0) {
>
> The second part is not needed, empty authtok cannot have size != 0 by
> definiton.
>
>> +
>> +                    DEBUG(SSSDBG_CRIT_FAILURE,
>> +                          ("Illegal zero-length authtok for user [%s]\n",
>> +                           pd->user));
>> +                    state->pam_status = PAM_AUTH_ERR;
>> +                    state->dp_err = DP_ERR_OK;
>> +                    ret = EOK;
>> +                    goto done;
>> +                }
>> +
>>                   DEBUG(SSSDBG_CRIT_FAILURE,
>>                         ("Wrong authtok type for user [%s]. " \
>>                          "Expected [%d], got [%d]\n", pd->user,
>> --
>> 1.8.1.4
>>
>
>>  From e9f44ae4e487b0cddfb676c7f52bcef9780c4393 Mon Sep 17 00:00:00 2001
>> From: Ondrej Kos <okos at redhat.com>
>> Date: Wed, 17 Jul 2013 13:58:36 +0200
>> Subject: [PATCH 3/3] KRB: Replace multiple calls with variable
>
> Meh, the compiler would optimize the call anyway :-) But in general I'm
> not opposed.
> _______________________________________________
> sssd-devel mailing list
> sssd-devel at lists.fedorahosted.org
> https://lists.fedorahosted.org/mailman/listinfo/sssd-devel
>

Resending all three patches, modified and rebased.

Ondra


-- 
Ondrej Kos
Associate Software Engineer
Identity Management - SSSD
Red Hat Czech
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