Re: Context settings after ssh login

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On 10/6/10 3:29 AM, "imsand@xxxxxxxxx" <imsand@xxxxxxxxx> wrote:

>> On 10/05/2010 11:43 PM, imsand@xxxxxxxxx wrote:
>>>> On 10/05/2010 06:38 AM, imsand@xxxxxxxxx wrote:
>>>>>> On 10/04/2010 11:30 PM, imsand@xxxxxxxxx wrote:
>>>>>>>> On 10/04/2010 01:03 AM, imsand@xxxxxxxxx wrote:
>>>>>>>>> Hello
>>>>>>>>> 
>>>>>>>>> I'm working on SUSE SLES11SP1 and encounter the following problem.
>>>>>>>>> Setting the context of the User after ssh login doesn't work if
>>>>>>>>> the
>>>>>>>>> SELinux Username and the Linux Username aren't identical.
>>>>>>>>> 
>>>>>>>>> --------------
>>>>>>>>> Here is an example (SElinux User=mat_u, Linux User=mat_u):
>>>>>>>>> Oct  4 09:41:54 testsrv.example sshd[15829]: Accepted
>>>>>>>>> keyboard-interactive/pam for mat_u from 131.102.233.125 port 54714
>>>>>>>>> ssh2
>>>>>>>>> Oct  4 09:41:54 testsrv.example sshd[15829]:
>>>>>>>>> pam_selinux(sshd:session):
>>>>>>>>> Open Session
>>>>>>>>> Oct  4 09:41:54 testsrv.example sshd[15829]:
>>>>>>>>> pam_selinux(sshd:session):
>>>>>>>>> Open Session
>>>>>>>>> Oct  4 09:41:54 testsrv.example sshd[15829]:
>>>>>>>>> pam_selinux(sshd:session):
>>>>>>>>> Username= mat_u SELinux User = user_u Level= (null)
>>>>>>>>> Oct  4 09:41:54 testsrv.example sshd[15829]:
>>>>>>>>> pam_selinux(sshd:session):
>>>>>>>>> set mat_u security context to user_u:user_r:user_t
>>>>>>>>> Oct  4 09:41:54 testsrv.example sshd[15829]:
>>>>>>>>> pam_selinux(sshd:session):
>>>>>>>>> set mat_u key creation context to user_u:user_r:user_t
>>>>>>>>> ---
>>>>>>>>> mat_u@xxxxxxxxxxxxxxx:~>     id
>>>>>>>>> uid=6575(mat_u) gid=100(users)
>>>>>>>>> groups=16(dialout),33(video),100(users)
>>>>>>>>> context=mat_u:staff_r:staff_t
>>>>>>>>> mat_u@xxxxxxxxxxxxxxx:~>     newrole -r sysadm_r
>>>>>>>>> mat_u@xxxxxxxxxxxxxxx:~>     id
>>>>>>>>> uid=6575(mat_u) gid=100(users)
>>>>>>>>> groups=16(dialout),33(video),100(users)
>>>>>>>>> context=mat_u:sysadm_r:sysadm_t
>>>>>>>>> --------------------
>>>>>>>>> 
>>>>>>>>> So, this is okey. The user's context after login is
>>>>>>>>> "mat_u:staff_r:staff_t"
>>>>>>>>> 
>>>>>>>>> But, if the Linux User is different from the SELinux User, the
>>>>>>>>> default
>>>>>>>>> user's will be chosen instead.
>>>>>>>>> 
>>>>>>>>> Here is the example (SELinux User=mat_u, Linux User=mat):
>>>>>>>>> ---------------------
>>>>>>>>> Oct  4 09:46:22 testsrv.example sshd[16185]: Accepted
>>>>>>>>> keyboard-interactive/pam for mat from 131.102.233.125 port 54726
>>>>>>>>> ssh2
>>>>>>>>> Oct  4 09:46:22 testsrv.example sshd[16185]:
>>>>>>>>> pam_selinux(sshd:session):
>>>>>>>>> Open Session
>>>>>>>>> Oct  4 09:46:22 testsrv.example sshd[16185]:
>>>>>>>>> pam_selinux(sshd:session):
>>>>>>>>> Open Session
>>>>>>>>> Oct  4 09:46:22 testsrv.example sshd[16185]:
>>>>>>>>> pam_selinux(sshd:session):
>>>>>>>>> Username= mat SELinux User = mat_u Level= (null)
>>>>>>>>> Oct  4 09:46:22 testsrv.example sshd[16185]:
>>>>>>>>> pam_selinux(sshd:session):
>>>>>>>>> set mat security context to mat_u:staff_r:staff_t
>>>>>>>>> Oct  4 09:46:22 testsrv.example sshd[16185]:
>>>>>>>>> pam_selinux(sshd:session):
>>>>>>>>> set mat key creation context to mat_u:staff_r:staff_t
>>>>>>>>> ---
>>>>>>>>> mat_u@xxxxxxxxxxxxxxx:~>     id
>>>>>>>>> uid=6575(mat) gid=100(users)
>>>>>>>>> groups=16(dialout),33(video),100(users)
>>>>>>>>> context=user_u:user_r:user_t
>>>>>>>>> 
>>>>>>>>> mat_u@xxxxxxxxxxxxxxx:~>     newrole -r sysadm_r
>>>>>>>>> user_u:sysadm_r:sysadm_t is not a valid context
>>>>>>>>> ---------------------
>>>>>>>>> 
>>>>>>>>> As you can see, the pam_selinux module recognizes that the new
>>>>>>>>> context
>>>>>>>>> should be "mat_u:staff_r:staff_t", but for some reason the real
>>>>>>>>> context
>>>>>>>>> is
>>>>>>>>> user_u:user_r:user_t. Changing the context with newrole doesn't
>>>>>>>>> work
>>>>>>>>> either...
>>>>>>>>> 
>>>>>>>>> The user mappings should be okey:
>>>>>>>>> ------
>>>>>>>>> semanage user -l | grep mat
>>>>>>>>> mat_u           staff_r sysadm_r
>>>>>>>>> testsrv.example:~ # semanage login -l | grep mat
>>>>>>>>> mat
>>>>>>>>> -------
>>>>>>>>> 
>>>>>>>>> Any idea out there? Do I miss something?
>>>>>>>>> kind regards
>>>>>>>>> Matthias
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> --
>>>>>>>>> This message was distributed to subscribers of the selinux mailing
>>>>>>>>> list.
>>>>>>>>> If you no longer wish to subscribe, send mail to
>>>>>>>>> majordomo@xxxxxxxxxxxxx
>>>>>>>>> with
>>>>>>>>> the words "unsubscribe selinux" without quotes as the message.
>>>>>>>>> 
>>>>>>>> 
>>>>>>>> you can specify the context in
>>>>>>>> /etc/selinux/policy/contexts/users/whatroleyouused
>>>>>>>> (under sshd) I normally set user_r:user_t:s0
>>>>>>>> 
>>>>>>>> 
>>>>>>>> Justin P. Mattock
>>>>>>>> 
>>>>>>>> --
>>>>>>>> This message was distributed to subscribers of the selinux mailing
>>>>>>>> list.
>>>>>>>> If you no longer wish to subscribe, send mail to
>>>>>>>> majordomo@xxxxxxxxxxxxx
>>>>>>>> with
>>>>>>>> the words "unsubscribe selinux" without quotes as the message.
>>>>>>>> 
>>>>>>> 
>>>>>>> The file looks like:
>>>>>>> cat /etc/selinux/refpolicy/contexts/users/mat_u
>>>>>>> system_r:local_login_t  staff_r:staff_t sysadm_r:sysadm_t
>>>>>>> system_r:remote_login_t  staff_r:staff_t
>>>>>>> system_r:sshd_t   staff_r:staff_t sysadm_r:sysadm_t
>>>>>>> system_r:crond_t  staff_r:cronjob_t
>>>>>>> system_r:xdm_t   staff_r:staff_t
>>>>>>> staff_r:staff_su_t  staff_r:staff_t
>>>>>>> staff_r:staff_sudo_t  staff_r:staff_t
>>>>>>> sysadm_r:sysadm_su_t  sysadm_r:sysadm_t
>>>>>>> sysadm_r:sysadm_sudo_t  sysadm_r:sysadm_t
>>>>>>> 
>>>>>>> So, theoretical this should be okey, isn't it?
>>>>>>> And as you can see in the log from above (set mat key creation
>>>>>>> context
>>>>>>> to
>>>>>>> mat_u:staff_r:staff_t) it "tries" to switch to staff but for some
>>>>>>> reason
>>>>>>> it doesn't work..
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>> 
>>>>>> if your sshd'ing and the context is staff_r:staff_t then it's
>>>>>> correct,
>>>>>> I
>>>>>> usually change this to user_r:user_t just cause I'm paranoid.
>>>>>> Also there is some options that you can set in /etc/pam.d to do other
>>>>>> checks etc..
>>>>>> 
>>>>>> Justin P. Mattock
>>>>>> 
>>>>> no it's not and that't the problem:)
>>>>> If I sshd'ing with mat_u it's always "user_r:user_t" even
>>>>> "staff_r:staff_t" is specified (see above). But it's correct if the
>>>>> selinux and linux users are named equaly (mat in the example).
>>>>> It seems that something with the context settings and usermapping
>>>>> isn't
>>>>> correct. Do you see the problem?
>>>>> 
>>>>> 
>>>> 
>>>> 
>>>> Somewhere in the policy it is set to default to user_r for sshd, I dont
>>>> think there is a boolean(but could be wrong)for that feature. maybe
>>>> it's
>>>> reading the default_contexts file which is set to use user_r:user_t
>>>> instead of reading mat_u for sshd(staff_r:staff_t)
>>>> 
>>>> Justin P. Mattock
>>>> 
>>>> 
>>> Unfortunately I can't see a rule doing this. The curious thing is, that
>>> it
>>> works if the selinux user and the linux user are equivalent (both
>>> mat_u).
>>> But it does NOT work if it is mat (linux user) and mapped to mat_u
>>> (selinux user).
>>> 
>>> 
>> 
>> 
>> hmm.. something seems configured wrong, what OS are you using? do you
>> have semanage login/user -l set up correctly?
>> 
>> over here I build the policy from git, normally edit policy/users (add)
>> gen_user(name,system_u, sysadm_r staff_r user_r, s0, s0 -
>> mls_systemhigh, mcs_allcats)
>> 
>> then after the policy is built and installed/loaded I do
>> semanage login -a -s name name (create name in contexts/users)
>> (or skip the above and just use semanage -a -s user_u name)
>> 
>> seems sshd works with the given context I specify(user_r) then if I want
>> to add more options I adjust /etc/pam.d/*
>> 
>> Justin P. Mattock
>> 
> Thanks for your reply.
> I'm using SLES 11 SP1. It wouldn't be the first bug regarding SELinux on
> this distro... ;)
> Here is what I've done so far.
> - Downloaded the latest reference policy from tresys
> - Compiled and installed it on my sles 11.1
> - 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
> "cp /etc/selinux/refpolicy/contexts/user/staff_u
> /etc/selinux/refpolicy/contexts/user/mat_u"
> - set boolean for sysadm ssh login to true: "setsebool -P ssh_sysadm_login
> on"
> 
> Do you know good debug options for tracing where it stucks?
> 
When debugging login-type programs figuring out the context to transition
to, there are a couple of simple useful utilities in libselinux/utils. These
are getconlist and getdefaultcon. Most distros won't install these (as
they're just debugging tools), but you can build them yourself out of the
tree.

getconlist will print out the contexts returned by
get_ordered_context_list(), which are all the reachable contexts. This could
tell you if the problem is that the context you're trying to transition to
is for some reason unreachable.

getdefaultcon can tell you (in verbose mode) the default seuser and level
returned by getseuserbyname() and the default context returned by
get_default_context_with_rolelevel()/get_default_context_with_level(). If
the seuser is wrong, then you know something's going wrong in
getseuserbyname().

I hope that helps.

Thanks,
Chad Sellers


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