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

Fri Mar 20 12:05:00 UTC 2015

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.

-- 
/ Alexander Bokovoy