Re: error: ssh_selinux_getctxbyname: Failed to get default SELinux security context

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On Wed, Sep 29, 2010 at 09:26:26AM +0200, imsand@xxxxxxxxx wrote:
> > On Tue, Sep 28, 2010 at 03:51:11PM +0200, imsand@xxxxxxxxx wrote:
> >> > On Tue, Sep 28, 2010 at 01:56:13PM +0200, imsand@xxxxxxxxx wrote:
> >> >> > On 28/09/10 08:24, imsand@xxxxxxxxx wrote:
> >> >> >> Hello
> >> >> >>
> >> >> >> I get the following error when I try to log in through ssh (even
> >> if
> >> >> >> selinux is in permissive mode!!!):
> >> >> >>
> >> >> >> Sep 28 09:01:32 stvlx05.test.ch sshd[12614]: Accepted
> >> >> >> keyboard-interactive/pam for mat from 131.102.233.127 port 58912
> >> ssh2
> >> >> >> Sep 28 09:01:32 stvlx05.test.admin.ch kernel: [60557.252750]
> >> >> type=1400
> >> >> >> audit(1285657292.298:286): avc:  denied  { audit_control } for
> >> >> >> pid=12614
> >> >> >> comm="sshd" capability=30  scontext=system_u:system_r:sysadm_t
> >> >> >> tcontext=system_u:system_r:sysadm_t tclass=capability
> >> >> >> Sep 28 09:01:32 stvlx05.test.ch sshd[12621]: error:
> >> >> >> ssh_selinux_getctxbyname: Failed to get default SELinux security
> >> >> context
> >> >> >> for mat
> >> >> >> Sep 28 09:01:32 stvlx05.test.ch sshd[12614]: error:
> >> >> >> ssh_selinux_getctxbyname: Failed to get default SELinux security
> >> >> context
> >> >> >> for mat
> >> >> >> Sep 28 09:01:32 stvlx05.test.ch sshd[12614]: error:
> >> >> >> ssh_selinux_setup_pty:
> >> >> >> security_compute_relabel: Invalid argument
> >> >> >>
> >> >> >> I already went through this post:
> >> >> >> http://www.nsa.gov/research/selinux/list-archive/0910/30906.shtml
> >> but
> >> >> I
> >> >> >> can't figure out the exact problem.
> >> >> >>
> >> >> >> Here is what I've done so far:
> >> >> >> - Downloaded the latest reference policy from tresys:
> >> >> >> http://oss.tresys.com/files/refpolicy/refpolicy-2.20100524.tar.bz2
> >> >> >> - Compiled and installed it on my sles 11.1
> >> >> >> - set selinux into permissive mode: (so far so good.. :))
> >> >> >> sestatus
> >> >> >> SELinux status:                 enabled
> >> >> >> SELinuxfs mount:                /selinux
> >> >> >> Current mode:                   permissive
> >> >> >> Mode from config file:          permissive
> >> >> >> Policy version:                 24
> >> >> >> Policy from config file:        refpolicy
> >> >> >> - Add selinux user "mat_u": semanage user -R "staff_r system_r" -P
> >> >> user
> >> >> >> -a
> >> >> >> mat_u
> >> >> >> - Add linux user " mat": useradd mat
> >> >> >> - Set password for "mat": passwd mat
> >> >> >> - User mapping: semanage login -s mat_u -a mat
> >> >> >> - add security context for "mat_u" by copying staff_u's context
> >> >> (don't
> >> >> >> know if that's needed??!): cp
> >> >> >> /etc/selinux/refpolicy/contexts/user/staff_u
> >> >> >> /etc/selinux/refpolicy/contexts/user/mat_u
> >> >> >> - set boolean for sysadm ssh login to true (don't know if thats
> >> >> >> needed?!):
> >> >> >> setsebool ssh_sysadm_login on
> >> >> >>
> >> >> >> In other posts I've read something about sepermit.conf and
> >> >> >> namespace.conf
> >> >> >> but these files don't exist on my system. What about these files?
> >> Do
> >> >> I
> >> >> >> need them?
> >> >> >> What's wrong on my system?
> >> >> >> Why it's not possible to login even if selinux is in permissive
> >> mode?
> >> >> >> Any suggestions?
> >> >> >
> >> >> > I'd start by trying to figure out why sshd isn't running in sshd_t
> >> (it
> >> >> > seems to be running in sysadm_t).
> >> >> >
> >> >> > Paul.
> >> >> > --
> >> >> > selinux mailing list
> >> >> > selinux@xxxxxxxxxxxxxxxxxxxxxxx
> >> >> > https://admin.fedoraproject.org/mailman/listinfo/selinux
> >> >> >
> >> >>
> >> >> Yes, sshd is running in sysadm_t:
> >> >>
> >> >> # ps axZ | grep sshd
> >> >> system_u:system_r:sysadm_t       3632 ?        Ss     0:00
> >> >> /usr/sbin/sshd
> >> >> -o PidFile=/var/run/sshd.init.pi
> >> >>
> >> >> # ls -Z /usr/sbin/sshd
> >> >> system_u:object_r:sshd_exec_t /usr/sbin/sshd
> >> >>
> >> >> Don't know why it's not sshd_t. I didn't modified something. It's a
> >> >> standard installation of sles11 with the default reference policy
> >> from
> >> >> tresys.
> >> >>
> >> >> Maybe this code snippet from policy/modules/services/ssh.te is
> >> >> responsible
> >> >> for that:
> >> >> ## <desc>
> >> >> ## <p>
> >> >> ## Allow ssh logins as sysadm_r:sysadm_t
> >> >> ## </p>
> >> >> ## </desc>
> >> >> gen_tunable(ssh_sysadm_login, true)
> >> >>
> >> >> Any ideas?
> >> >
> >> > Do you have boolean init_upstart set to on? if not try setting it to
> >> on.
> >> > I do not believe ssh_sysadm_login boolean works currently but i may be
> >> > mistaken.
> >
> > ssh_sysadm_login DOES actually work you just need to specify your role on
> > login...
> >
> I suppose to edit /etc/selinux/refpolicy/src/policy/config/local.users for
> doing so!? I added "user mat roles { sysadm_r };" rebuild & load the
> policy. But after login the the context is still "user_u:user_r:user_t".
> the user should be able to change the role to sysadm_r:
> ----
> semanage user -l
> SELinux User    SELinux Roles
> mat_u           staff_r sysadm_r
> ----
> Doing it explicitly does not work either:
> ----
> newrole -r staff_r
> user_u:staff_r:staff_t is not a valid context
> ----
> Don't know why. Restricted by a special policy?

Yes restricted by constraints. user_u is designed to not be allowed to role transition.
First you much achieve that you login with the staff_u identity (and staff_r role, staff_t domain)

I am not sure why youre login identity is user_u and not staff_u. Have you:

semanage login -a -s mat_u mat
semanage login -l | grep mat 
> 
> 
> --
> selinux mailing list
> selinux@xxxxxxxxxxxxxxxxxxxxxxx
> https://admin.fedoraproject.org/mailman/listinfo/selinux

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