[Freeipa-users] 'Preauthentication failed' with SSSD in ipa_server_mode

Fri Mar 20 13:33:03 UTC 2015

On 03/20/2015 08:05 AM, Alexander Bokovoy wrote:
> On Fri, 20 Mar 2015, Bobby Prins wrote:
>>> On Fri, 20 Mar 2015, Sumit Bose wrote:
>>>> On Fri, Mar 20, 2015 at 11:44:43AM +0100, Bobby Prins wrote:
>>>>> On Thu, Mar 19, 2015 at 04:46:44PM +0100, Bobby Prins wrote:
>>>>> >> Hi there,
>>>>> >>
>>>>> >> I'm currently trying to use the 'AD Trust for Legacy Clients'
>>>>> >> freeIPA setup (described here:
>>>>> >> http://www.freeipa.org/images/0/0d/FreeIPA33-legacy-clients.pdf)
>>>>> >> to be able to autenticate AIX 7.1 clients against an AD domain
>>>>> >> using LDAP. After the trust was created all seems to work well
>>>>> >> on the freeIPA server. I can also do a lookup of AD users and
>>>>> >> groups on an AIX test server.
>>>>> >>
>>>>> >> But as soon as I want to log in on the AIX system I get an SSSD 
>>>>> error on the freeIPA server in krb5_child.log (debug_level = 10):
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.590260: AS 
>>>>> key obtained for encrypted timestamp: aes256-cts/2F5D
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.590326: 
>>>>> Encrypted timestamp (for 1426778442.525165): plain 
>>>>> 301AA011180F32303135303331393135323034325AA105020308036D, 
>>>>> encrypted 
>>>>> 9B3299264F09E50D63D84B385A09A4C64D44116A02B58FFF12830B39F88722CD9B792F5ABA0653578DE9138B91D29C17C197453D8B8A5E7A
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.590349: 
>>>>> Preauth module encrypted_timestamp (2) (flags=1) returned: 0/Success
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.590360: 
>>>>> Produced preauth for next request: 2
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.590384: 
>>>>> Sending request (238 bytes) to EXAMPLE.CORP
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.591325: 
>>>>> Resolving hostname dct020.example.corp.
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.591889: 
>>>>> Sending initial UDP request to dgram 192.168.143.1:88
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.636127: 
>>>>> Received answer from dgram 192.168.143.1:88
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.636626: 
>>>>> Response was not from master KDC
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.636667: 
>>>>> Received error from KDC: -1765328360/Preauthentication failed
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.636698: 
>>>>> Preauth tryagain input types: 16, 14, 19, 2
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.636728: 
>>>>> Retrying AS request with master KDC
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.636741: 
>>>>> Getting initial credentials for BPrins at EXAMPLE.CORP
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [sss_child_krb5_trace_cb] (0x4000): [12775] 1426778442.636787: 
>>>>> Sending request (160 bytes) to EXAMPLE.CORP (master)
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [get_and_save_tgt] (0x0020): 979: [-1765328360][Preauthentication 
>>>>> failed]
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [map_krb5_error] (0x0020): 1040: [-1765328360][Preauthentication 
>>>>> failed]
>>>>> >> (Thu Mar 19 16:20:42 2015) [[sssd[krb5_child[12775]]]] 
>>>>> [k5c_send_data] (0x0200): Received error code 1432158214
>>>>> >>
>>>>> >> If I do the same with 'KRB5_TRACE=/dev/stderr kinit 
>>>>> BPrins at EXAMPLE.CORP':
>>>>> >> [12299] 1426773524.361785: AS key obtained for encrypted 
>>>>> timestamp: aes256-cts/B997
>>>>> >> [12299] 1426773524.361850: Encrypted timestamp (for 
>>>>> 1426773524.277583): plain 
>>>>> 301AA011180F32303135303331393133353834345AA1050203043C4F, 
>>>>> encrypted 
>>>>> ED9CF995617740C4B14DB9CC84187E3505B664FE5C0AD16D19477E912F5400FB2C4665A090E3A37CD749535B3C80595809E14D15CB3527C0
>>>>> >> [12299] 1426773524.361876: Preauth module encrypted_timestamp 
>>>>> (2) (flags=1) returned: 0/Success
>>>>> >> [12299] 1426773524.361880: Produced preauth for next request: 2
>>>>> >> [12299] 1426773524.361901: Sending request (238 bytes) to 
>>>>> EXAMPLE.CORP
>>>>> >> [12299] 1426773524.363002: Resolving hostname dct020.EXAMPLE.corp.
>>>>> >> [12299] 1426773524.363841: Sending initial UDP request to dgram 
>>>>> 192.168.141.1:88
>>>>> >> [12299] 1426773524.368089: Received answer from dgram 
>>>>> 192.168.141.1:88
>>>>> >> [12299] 1426773524.368482: Response was not from master KDC
>>>>> >> [12299] 1426773524.368500: Received error from KDC: 
>>>>> -1765328332/Response too big for UDP, retry with TCP
>>>>> >> [12299] 1426773524.368506: Request or response is too big for 
>>>>> UDP; retrying with TCP
>>>>> >> [12299] 1426773524.368511: Sending request (238 bytes) to 
>>>>> EXAMPLE.CORP (tcp only)
>>>>> >> [12299] 1426773524.368953: Resolving hostname dct030.EXAMPLE.corp.
>>>>> >> [12299] 1426773524.370056: Initiating TCP connection to stream 
>>>>> 192.168.143.5:88
>>>>> >> [12299] 1426773524.375140: Sending TCP request to stream 
>>>>> 192.168.143.5:88
>>>>> >> [12299] 1426773524.383801: Received answer from stream 
>>>>> 192.168.143.5:88
>>>>> >> [12299] 1426773524.384237: Response was not from master KDC
>>>>> >> [12299] 1426773524.384263: Processing preauth types: 19
>>>>> >> [12299] 1426773524.384271: Selected etype info: etype 
>>>>> aes256-cts, salt "EXAMPLE.CORPBPrins", params ""
>>>>> >> [12299] 1426773524.384275: Produced preauth for next request: 
>>>>> (empty)
>>>>> >> [12299] 1426773524.384282: AS key determined by preauth: 
>>>>> aes256-cts/B997
>>>>> >> [12299] 1426773524.384329: Decrypted AS reply; session key is: 
>>>>> rc4-hmac/39AB
>>>>> >> [12299] 1426773524.384333: FAST negotiation: unavailable
>>>>> >> [12299] 1426773524.384357: Initializing 
>>>>> KEYRING:persistent:0:krb_ccache_rhX3V4v with default princ 
>>>>> BPrins at EXAMPLE.CORP
>>>>> >> [12299] 1426773524.384400: Removing BPrins at EXAMPLE.CORP -> 
>>>>> krbtgt/EXAMPLE.CORP at EXAMPLE.CORP from 
>>>>> KEYRING:persistent:0:krb_ccache_rhX3V4v
>>>>> >> [12299] 1426773524.384407: Storing BPrins at EXAMPLE.CORP -> 
>>>>> krbtgt/EXAMPLE.CORP at EXAMPLE.CORP in 
>>>>> KEYRING:persistent:0:krb_ccache_rhX3V4v
>>>>> >> [12299] 1426773524.384469: Storing config in 
>>>>> KEYRING:persistent:0:krb_ccache_rhX3V4v for 
>>>>> krbtgt/EXAMPLE.CORP at EXAMPLE.CORP: pa_type: 2
>>>>> >> [12299] 1426773524.384484: Removing BPrins at EXAMPLE.CORP -> 
>>>>> krb5_ccache_conf_data/pa_type/krbtgt\/EXAMPLE.CORP\@EXAMPLE.CORP at X-CACHECONF: 
>>>>> from KEYRING:persistent:0:krb_ccache_rhX3V4v
>>>>> >> [12299] 1426773524.384492: Storing BPrins at EXAMPLE.CORP -> 
>>>>> krb5_ccache_conf_data/pa_type/krbtgt\/EXAMPLE.CORP\@EXAMPLE.CORP at X-CACHECONF: 
>>>>> in KEYRING:persistent:0:krb_ccache_rhX3V4v
>>>>> >>
>>>>> >> Any ideas?
>>>>> >
>>>>> >Can you log in to the IPA server as this user? If yes I would assume
>>>>> >that the password gets garbled somewhere on the way from AIX 
>>>>> through the
>>>>> >IPA machinery to SSSD. Does the password contain some special 
>>>>> characters
>>>>> >which some LDAP processing calls might want the escape?
>>>>> >
>>>>> >bye,
>>>>> >Sumit
>>>>> >
>>>>> Yes, I can login with the account on the IPA server without any
>>>>> problems. I tried it with different password to rule out problems
>>>>> with special characters. Finally I did a tcpdump on the IPA server.
>>>>> The AIX server sends the word 'INCORRECT' to the IPA server instead
>>>>> of the password. So I guess I have to do some more configuration
>>>>> checks on the AIX server.
>>>>
>>>> Thank you for the feedback.
>>>>
>>>> Just a wild guess, since you were able to see anything in the 
>>>> tcpdump I
>>>> guess an unencrypted connection is used. Maybe AIX prevents that the
>>>> password is send via a clear text connection?
>>> It is openssh behavior. It sends INCORRECT line as part of the password
>>> when there is no valid shell for that user to login.
>>>
>>> OpenSSH validates content of 'struct passwd' returned for the user,
>>> including checks on whether shell is there as an executable file. This
>>> check fails and user is considered 'invalid'. Still, OpenSSH competes
>>> PAM authentication, making sure the password field is filled with
>>> specially constructed string "\b\n\r\177INCORRECT", to ensure there is
>>> registered failed login attempt.
>> Wow, thanks for that! If I do a lsuser/ldapsearch on the AIX host the
>> shell/loginShell is missing for AD users. The admin IPA user has this
>> attribute set and I can log in with that account. Can this be solved on
>> the IPA server?
> In FreeIPA 4.1 (Fedora 21+ or RHEL7.1) you can do set shell separately
> for each AD user using ID Views:
>
> ipa idoverrideuser-add 'Default Trust View' 'AD\User' --shell /bin/ksh
>
> Compat tree and SSSD on RHEL7.1/Fedora21 should take default trust view
> into account for AD users.
>
Once we are out of the woods here it would be really nice to have a blog 
or a wiki page about how to configure AIX clients properly to leverage 
trusts including this interesting aspect related to the shell.
Bobby would you be able to share this information?

-- 
Thank you,
Dmitri Pal

Sr. Engineering Manager IdM portfolio
Red Hat, Inc.