New subject: ssh passwordless with sssd-1.12.5 problem!!

30 Jul 2015


      Hi again,
After implementing the recommended change my setup seemed to work fine with passwordless SSH and kerberized NFS4.
Unexpectedly, after  credentials expired  (I got the message "key expired" !),  I can't  mount home directory at all, not only in ssh session, but also  login locally to the client workstation.
After client reboot, access to users NFS homedir is lost as well.
Does the [plugin] change in krb5.conf could have  impact on nfs service too?
[plugins]
localauth = {
         module=sssd:/usr/lib/x86_64-linux- gnu/sssd/modules/sssd_krb5_localauth_plugin.so
         enable_only = sssd
         }
I noticed that SSH session  uses in-MEMORY cache ; NFS server is setup with ccache in /tmp
If I compare ssh<->nfs sessions it seems that user's principal credentials never get through to the server.
(successful ssh session in the previous mail).
What is wrong?
------nfs session (rpc.svcgssd) on server------- 
entering poll
leaving poll
handling null request
svcgssd_limit_krb5_enctypes: Calling gss_set_allowable_enctypes with 7 enctypes from the kernel
[6404] 1438257362.977400: Decrypted AP-REQ with server principal nfs/nfssrv.adm.c.sdu.dk@A.C.REALM: aes256-cts/0F5A
[6404] 1438257362.977427: AP-REQ ticket: LNX-LEIA$@A.C.REALM -> nfs/nfssrv.adm.c.sdu.dk@A.C.REALM, session key aes256-cts/DD8F
[6404] 1438257362.978032: Negotiated enctype based on authenticator: aes256-cts
[6404] 1438257362.978057: Authenticator contains subkey: aes256-cts/0652
[6404] 1438257362.978106: Creating AP-REP, time 1438257362.982778, subkey aes256-cts/41C3, seqnum 738956702
sname = LNX-LEIA$@A.C.REALM
DEBUG: serialize_krb5_ctx: lucid version!
prepare_krb5_rfc4121_buffer: protocol 1
prepare_krb5_rfc4121_buffer: serializing key with enctype 18 and size 32
doing downcall
mech: krb5, hndl len: 4, ctx len 52, timeout: 1438293240 (35878 from now), clnt: <null>, uid: -1, gid: -1, num aux grps: 0:
sending null reply
best
Longina
...
-----Oprindelig meddelelse-----
Fra: sssd-users-bounces@lists.fedorahosted.org [mailto:sssd-users-
bounces@lists.fedorahosted.org] På vegne af Longina Przybyszewska
Sendt: 14. juli 2015 17:08
Til: 'End-user discussions about the System Security Services Daemon'
Emne: Re: [SSSD-users] ssh passwordless with sssd-1.12.5
Hi again,
Thanks - it seems to work!
I am not sure if k5login directory and .k5login play any role in success - I need
to check it out.
First, I put k5login entries into krb5.conf on both, client and server, and tried
ssh - It didn't work, I was asked for password.
[krb5.conf] on both.
...
k5login_directory = /usr/share/ssh/%u
k5login_authoritative  = true
ignore_acceptor_hostname = true
...
.....
[Kerberos part of output from " KRB5_TRACE=/tmp/1.txt /usr/sbin/sshd -D -
d -d -d "]
less 1.txt
[2863] 1436879405.741004: Decrypted AP-REQ with server principal
LX101$@A.C.REALM: aes256-cts/2CCB [2863] 1436879405.741095: AP-REQ
ticket: longina@N.C.REALM-> LX101$@A.C.REALM, session key aes256-
cts/2E16 [2863] 1436879405.799281: Negotiated enctype based on
authenticator: aes256-cts [2863] 1436879405.799314: Authenticator contains
subkey: aes256-cts/1399 [2863] 1436879405.799475: Resolving unique ccache
of type MEMORY [2863] 1436879405.799493: Initializing MEMORY:pvs4jFN
with default princ longina@N.C.REALM [2863] 1436879405.799504: Removing
longina@N.C.REALM-> krbtgt/N.C.REALM@N.C.REALM from
MEMORY:pvs4jFN [2863] 1436879405.799514: Storing longina@N.C.REALM->
krbtgt/N.C.REALM@N.C.REALM in MEMORY:pvs4jFN [2863]
1436879405.799566: Creating AP-REP, time 1436879405.736646, subkey
aes256-cts/7528, seqnum 774738294
[2863] 1436879405.804209: Destroying ccache MEMORY:pvs4jFN
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
After adding to krb5.conf on server [plugins] as you suggested - I could login
without passwd .
The difference is in the last line of KRB -part of  output:
[plugins]
    localauth = {
    module=sssd:/usr/lib/x86_64-linux-

gnu/sssd/modules/sssd_krb5_localauth_plugin.so
        enable_only = sssd
        }
.....
[3534] 1436884067.287402: Decrypted AP-REQ with server principal
lx101$@A.C.REALM: aes256-cts/2CCB [3534] 1436884067.287447: AP-REQ
ticket: longina@N.C.REALM -> lx101$@A.C.REALM, session key aes256-
cts/2E16 [3534] 1436884067.358812: Negotiated enctype based on
authenticator: aes256-cts [3534] 1436884067.358841: Authenticator contains
subkey: aes256-cts/3DE0 [3534] 1436884067.359004: Resolving unique ccache
of type MEMORY [3534] 1436884067.359023: Initializing MEMORY:pJb8FBS
with default princ longina@N.C.REALM [3534] 1436884067.359035: Removing
longina@N.C.REALM -> krbtgt/N.C.REALM@N.C.REALM from
MEMORY:pJb8FBS [3534] 1436884067.359045: Storing longina@N.C.REALM ->
krbtgt/N.C.REALM@N.C.REALM in MEMORY:pJb8FBS [3534]
1436884067.359101: Creating AP-REP, time 1436884067.280266, subkey
aes256-cts/4AD9, seqnum 458315653
[3534] 1436884067.630732: Initializing
FILE:/tmp/krb5cc_10002_4NMbBVHudH with default princ
longina@N.C.REALM
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
I must say, that "localauth" is not mentioned in manual for krb5.conf, but
works! Impossible  to figure out by myself!
Thank you very much  for help.
Mvh
Longina
...
-----Oprindelig meddelelse-----
Fra: sssd-users-bounces@lists.fedorahosted.org [mailto:sssd-users-
bounces@lists.fedorahosted.org] På vegne af Sumit Bose
Sendt: 13. juli 2015 09:57
Til: End-user discussions about the System Security Services Daemon
Emne: Re: [SSSD-users] ssh passwordless with sssd-1.12.5
On Fri, Jul 10, 2015 at 04:50:39PM +0000, Longina Przybyszewska wrote:
...
Hi,
.k5login doesn't help . Homedir is mounted with sec=krb5 and not
accessible on ssh server side Until  get validated krb principal
credentials -
which seems to be my problem.
You can use k5login_directory in krb5.conf to use a different
directory for testing.
...
I have noticed , I have no libpam-krb5 module in PAM I have
libpam-sss  module, which seems to be enough to deal with krb
principals for NFS-mounts and GUI logins  and ssh logins with passwd.
With SSSD I can login as 'longina' to machine from @A.C.REALM domain
and
get my Kerberos  TGT for principal longina@N.C.REALM.
...
Trying SSH - Service tickets nfs/fqdn@A.C.REALM and
host/fqdn@A.C.REALM seem to be ok but user not accepted without
passwd.
...
SSH should talk to SSSD through PAM , well?
In general yes, but for GSSAPI authentication sshd has to do the
Kerberos ticket validation on it's own. With recent versions of MIT
Kerberos SSSD can help with the principal to username mapping. If your
krb5.conf man page says anything about a localauth plugin you can try
to add something like
[plugins]
 localauth = {
  module = sssd:/usr/lib/sssd/modules/sssd_krb5_localauth_plugin.so
  enable_only = sssd
to your krb5.conf. Please note that you have to say 'enable_only =
sssd, k5login' is you want to use .k5login files as well.
If authentication and user mapping is done and was successful sshd
will do the PAM based access control with the help of SSSD.
bye,
Sumit
...
Best,
Longina
...
-----Oprindelig meddelelse-----
Fra: sssd-users-bounces@lists.fedorahosted.org [mailto:sssd-users-
bounces@lists.fedorahosted.org] På vegne af Sumit Bose
Sendt: 10. juli 2015 10:22
Til: End-user discussions about the System Security Services
Daemon
Emne: Re: [SSSD-users] ssh passwordless with sssd-1.12.5
On Thu, Jul 09, 2015 at 04:06:05PM +0000, Longina Przybyszewska
wrote:
...
...
...
...
Hi,
I have SSSD setup with AD as  auth/id provider  in multi domain
trust realm,
and POSIX attributes in AD for users.
...
With this setup users can use short names (short names  match
sSAMaccount name in AD user object)) for login and get access to
...
their  homedir ,NFS mounted with Kerberos security.
The "short user names" are unique  across domains in realm.
Setup works fine, even after recently made possible sssd upgrade
to 1.12.5
(all Linux clients run Ubuntu LTS).
...
We would like to establish passwordless ssh between all
AD-integrated
clients - and have problems.
...
The important detail is, that all machines are in one domain,
while
users
...
...
can be   from other domains inclusive, machine's domain .
...
Until now, passwordless ssh is possible when user and machine
are from
the same domain .
...
Users from domains other than machines's own domain , are asked
for
passwd.
...
All  tickets for host and  nfs service in user's cache seems to be ok.
After debugging ssh/sshd session it seems that connection ssh< -
-> sshd
fails on  user  authorization.
...
Any ideas?
Ssh client side  debug:
[9537] 1436450526.619393: Got service principal
host/lnx.a.c.realm@A.C.REALM [9537] 1436450526.621139: ccselect
can't find appropriate cache for server principal
host/lnx.a.c.realm@A.C.REALM [9537] 1436450526.621254: Getting
credentials longina@N.C.REALM -> host/lnx.a.c.realm@A.C.REALM
using ccache FILE:/tmp/krb5cc_XXXXX_CN76dg [9537]
1436450526.621355:
...
...
...
Retrieving longina@N.C.REALM -> host/lnx.a.c.realm@A.C.REALM
from FILE:/tmp/krb5cc_XXXXX_CN76dg with result: 0/Success [9537]
1436450526.621490: Creating authenticator for longina@N.C.REALM
-> host/lnx.a.c.realm@A.C.REALM, seqnum 1059254370, subkey
aes256-cts/4255, session key aes256-cts/2F16
debug2: we sent a gssapi-with-mic packet, wait for reply
debug1: Authentications that can continue:
publickey,gssapi-keyex,gssapi-with-mic,password
[9537] 1436450526.623050: Convert service host (service with
host as
instance) on host lnx.a.c.realmto principal [9537] 1436450526.624716:
Remote host after forward canonicalization: lnx.a.c.realm [9537]
1436450526.624760: Remote host after reverse DNS processing:
lnx.a.c.realm [9537] 1436450526.624793: Got service principal
host/lnx.a.c.realm@A.C.REALM [9537] 1436450526.626601: ccselect
can't find appropriate cache for server principal
host/lnx.a.c.realm@A.C.REALM [9537] 1436450526.626719: Getting
credentials longina@N.C.REALM -> host/lnx.a.c.realm@A.C.REALM
using ccache FILE:/tmp/krb5cc_XXXXX_CN76dg [9537]
1436450526.626821:
...
...
...
Retrieving longina@N.C.REALM -> host/lnx.a.c.realm@A.C.REALM
from FILE:/tmp/krb5cc_XXXXX_CN76dg with result: 0/Success [9537]
1436450526.626984: Getting credentials longina@N.C.REALM ->
host/lnx.a.c.realm@A.C.REALM using ccache
FILE:/tmp/krb5cc_XXXXX_CN76dg [9537] 1436450526.627067:
Retrieving longina@N.C.REALM -> host/lnx.a.c.realm@A.C.REALM
from FILE:/tmp/krb5cc_XXXXX_CN76dg with result: 0/Success [9537]
1436450526.627162: Creating authenticator for longina@N.C.REALM
-> host/lnx.a.c.realm@A.C.REALM, seqnum 778106202, subkey
aes256-cts/CBE6, session key aes256-cts/2F16
debug2: we sent a gssapi-with-mic packet, wait for reply
debug1: Authentications that can continue:
publickey,gssapi-keyex,gssapi-with-mic,password
debug2: we did not send a packet, disable method
debug3: authmethod_lookup publickey
sshd server side debug:
....
debug2: input_userauth_request: setting up authctxt for longina
[preauth]
debug3: mm_start_pam entering [preauth]
debug3: mm_request_send entering: type 100 [preauth]
debug3: mm_inform_authserv entering [preauth]
debug3: mm_request_send entering: type 4 [preauth]
debug2: input_userauth_request: try method none [preauth]
debug3: userauth_finish: failure partial=0 next
methods="publickey,gssapi-keyex,gssapi-with-mic,password"
[preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 100
debug1: PAM: initializing for "longina"
debug1: PAM: setting PAM_RHOST to "10.80.8.108"
debug1: PAM: setting PAM_TTY to "ssh"
debug2: monitor_read: 100 used once, disabling now
debug3: mm_request_receive entering
debug3: monitor_read: checking request 4
debug3: mm_answer_authserv: service=ssh-connection, style=,
role=
debug2: monitor_read: 4 used once, disabling now
debug1: userauth-request for user longina service ssh-connection
method gssapi-with-mic [preauth]
debug1: attempt 1 failures 0 [preauth]
debug2: input_userauth_request: try method gssapi-with-mic
[preauth]
debug3: mm_request_send entering: type 42 [preauth]
debug3: mm_request_receive_expect entering: type 43 [preauth]
debug3: mm_request_receive entering [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 42
debug3: mm_request_send entering: type 43 Postponed
gssapi-with-mic for longina from 10.80.8.108 port 53479 ssh2
[preauth]
debug3: mm_request_send entering: type 44 [preauth]
debug3: mm_request_receive_expect entering: type 45 [preauth]
debug3: mm_request_send entering: type 47 Failed gssapi-with-mic
for longina from 10.80.8.108 port 53479 ssh2
debug3: mm_ssh_gssapi_userok: user not authenticated [preauth]
Chances are that mapping the Kerberos principal to the local user
name
fails.
...
...
Since the Kerberos ticket only contains the Kerberos principal and
it is not desirable that any user with a valid Kerberos ticket can
log in as any local user the Kerberos client library has to do
some mapping between the Kerberos principal and the local user
name.
...
...
...
There are various mapping schemes available. For testing
(especially since I'm not too familiar with Kerberos on Ubuntu) I
would recommend to create a .k5login file in the home directory of
the user you want to log in as. The .k5login file should contain
the Kerberos principal which should be allowed to log in as this
user, e.g. longina@N.C.REALM in your case (please note that
Kerberos is case-sensitive). Please check permissions on .k5login
as well, only the
user itself should be able to access it.
...
...
If this works but you don't want to add a .k5login file for every
user please tell me which Kerberos version is used on your Ubuntu
system to see which other schemes are available.
HTH
bye,
Sumit

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Re: [SSSD-users] ssh passwordless with sssd-1.12.5 problem!!

Ssh client side debug:

sshd server side debug:

Ssh client side debug:

sshd server side debug: