Proprietary telnet daemon fails login when SELinux is enabled

[Dave Stoner]

I apologise in advance for asking questions which I feel I should have
been able to answer from sources on the internet. If you could possibly
give me some pointers on where to look it would be so much appreciated.

 

My system is centos 6.2 - 

Linux MyHostName 2.6.32-220.el6.x86_64 #1 SMP Tue Dec 6 19:48:22

GMT 2011 x86_64 x86_64 x86_64 GNU/Linux

 

SELinux mode is set 'enforced'.

 

I have a proprietary telnet daemon which upon a telnet to port 52000, is
started OK when SELinux is disabled. But when it is enabled the same
telnet results in /var/log/audit/audit.log showing:

 

type=USER_LOGIN msg=audit(1343048458.345:69): user pid=2536 uid=0
auid=799 ses=7 subj=system_u:system_r:inetd_t:s0-s0:c0.c1023
msg='op=login id=799 exe="/bin/login" hostname=0.0.0.0 addr=0.0.0.0
termi

nal=pts/2 res=success'

 

A normal telnet gives a message similar to above, my telnet adds the
following:

 

type=AVC msg=audit(1343048458.353:70): avc:  denied  { entrypoint } for
pid=2543 comm="login" path="/bin/bash" dev=sda2 ino=135083
scontext=unconfined_u:system_r:qmail_tcp_env_t:s0-s0:c0.c1023 tconte

xt=system_u:object_r:shell_exec_t:s0 tclass=file

 

I believe I can create a policy to overcome this using audit2allow, i.e.
it comes up with:

 

module mypola 1.0;

 

require {

        type qmail_tcp_env_t;

        type shell_exec_t;

        class file entrypoint;

}

 

#============= qmail_tcp_env_t ==============

allow qmail_tcp_env_t shell_exec_t:file entrypoint;

 

But it seems to me what I ought to be doing is somehow to get my daemon
to run with a domain of 'remote_logon_t' as is used by the standard
telnet daemon, as here:

 

type=USER_LOGIN msg=audit(1343058924.928:212): user pid=3759 uid=0
auid=799 ses=29 subj=system_u:system_r:remote_login_t:s0-s0:c0.c1023
msg='op=login id=799 exe="/bin/login" hostname=localhost addr=::

1 terminal=pts/2 res=success'

 

This is unfamiliar territory and any hints or pointers would really be
appreciated.

 

Dave.

 

 

Dave Stoner

Principal Systems Architect
Northgate Reality

Direct:    [phone] - VPN: 872 2071

www.northgate-is.com/reality <http://www.northgate-is.com/reality>  

 


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Limited .Registered in England no. 1587537  -  Moorepay Limited.  Registered in England
no. 891686  - First Business Support Limited. Registered in England no. 3056267 - 
Registered Office: Peoplebuilding 2, Peoplebuilding Estate, Maylands Avenue, Hemel
Hempstead, Hertfordshire HP2 4NW 
 
Northgate Managed Services Limited (NI).  Registered in Northern Ireland no. NI032979  - 
LearnServe Limited (NI).  Registered in Northern Ireland no. NI043825
Registered Office: Hillview House, 61 Church Road, Newtownabbey, Co. Antrim, BT36 7LQ 

-----------------------------------------------------------------------------------------

[Ted Toth]

You could try using the exist telnet policy in ref policy by chconing
your executable to telnetd_exec_t. However depending on what your
custom telnet daemon does you may still get AVCs.

Ted

On Thu, Jul 26, 2012 at 8:10 AM, Dave Stoner
<dave.stoner(a)northgate-is.com&gt; wrote:
>  I apologise in advance for asking questions which I feel I should
> have been
>  able to answer from sources on the internet. If you could possibly give me
>  some pointers on where to look it would be so much appreciated.
>
>
>
>  My system is centos 6.2 –
>
>  Linux MyHostName 2.6.32-220.el6.x86_64 #1 SMP Tue Dec 6 19:48:22
>
>  GMT 2011 x86_64 x86_64 x86_64 GNU/Linux
>
>
>
>  SELinux mode is set ‘enforced’.
>
>
>
>  I have a proprietary telnet daemon which upon a telnet to port 52000, is
>  started OK when SELinux is disabled. But when it is enabled the same telnet
>  results in /var/log/audit/audit.log showing:
>
>
>
>  type=USER_LOGIN msg=audit(1343048458.345:69): user pid=2536 uid=0 auid=799
>  ses=7 subj=system_u:system_r:inetd_t:s0-s0:c0.c1023 msg='op=login id=799
>  exe="/bin/login" hostname=0.0.0.0 addr=0.0.0.0 termi
>
>  nal=pts/2 res=success'
>
>
>
>  A normal telnet gives a message similar to above, my telnet adds the
>  following:
>
>
>
>  type=AVC msg=audit(1343048458.353:70): avc:  denied  { entrypoint } for
>  pid=2543 comm="login" path="/bin/bash" dev=sda2 ino=135083
>  scontext=unconfined_u:system_r:qmail_tcp_env_t:s0-s0:c0.c1023 tconte
>
>  xt=system_u:object_r:shell_exec_t:s0 tclass=file
>
>
>
>  I believe I can create a policy to overcome this using audit2allow, i.e. it
>  comes up with:
>
>
>
>  module mypola 1.0;
>
>
>
>  require {
>
>          type qmail_tcp_env_t;
>
>          type shell_exec_t;
>
>          class file entrypoint;
>
>  }
>
>
>
>  #============= qmail_tcp_env_t ==============
>
>  allow qmail_tcp_env_t shell_exec_t:file entrypoint;
>
>
>
>  But it seems to me what I ought to be doing is somehow to get my daemon to
>  run with a domain of ‘remote_logon_t’ as is used by the standard telnet
>  daemon, as here:
>
>
>
>  type=USER_LOGIN msg=audit(1343058924.928:212): user pid=3759 uid=0 auid=799
>  ses=29 subj=system_u:system_r:remote_login_t:s0-s0:c0.c1023 msg='op=login
>  id=799 exe="/bin/login" hostname=localhost addr=::
>
>  1 terminal=pts/2 res=success'
>
>
>
>  This is unfamiliar territory and any hints or pointers would really be
>  appreciated.
>
>
>
>  Dave.
>
>
>
>
>
>  Dave Stoner
>
>  Principal Systems Architect
>  Northgate Reality
>
>  Direct:    [phone] - VPN: 872 2071
>
>  www.northgate-is.com/reality
>
>
>
>
>  ________________________________
>
>  This email is sent on behalf of Northgate Information Solutions Limited and
>  its associated companies ("Northgate") and is strictly confidential and
>  intended solely for the addressee(s).
>
>   If you are not the intended recipient of this email you must: (i) not
>  disclose, copy or distribute its contents to any other person nor use its
>  contents in any way or you may be acting unlawfully;  (ii) contact Northgate
>  immediately on [phone] quoting the name of the sender and the
>  addressee then delete it from your system.
>
>   Northgate has taken reasonable precautions to ensure that no viruses are
>  contained in this email, but does not accept any responsibility once this
>  email has been transmitted.  You should scan attachments (if any) for
>  viruses.
>
>   Northgate Information Solutions Limited. Registered in England no. 06442582
>  -  Northgate Information Solutions UK Limited. Registered in England no.
>  968498  -  NorthgateArinso UK Limited. Registered in England no. 1587537  -
>  Moorepay Limited.  Registered in England no. 891686  - First Business
>  Support Limited. Registered in England no. 3056267 -   Registered Office:
>  Peoplebuilding 2, Peoplebuilding Estate, Maylands Avenue, Hemel Hempstead,
>  Hertfordshire HP2 4NW
>
>   Northgate Managed Services Limited (NI).  Registered in Northern Ireland
>  no. NI032979  -  LearnServe Limited (NI).  Registered in Northern Ireland
>  no. NI043825 Registered Office: Hillview House, 61 Church Road,
>  Newtownabbey, Co. Antrim, BT36 7LQ
>
>  ________________________________
>
>
>  --
>  selinux mailing list
>  selinux(a)lists.fedoraproject.org
>  https://admin.fedoraproject.org/mailman/listinfo/selinux

[Tristan Santore]

On 26/07/12 14:52, Ted Toth wrote:
>  You could try using the exist telnet policy in ref policy by
> chconing
>  your executable to telnetd_exec_t. However depending on what your
>  custom telnet daemon does you may still get AVCs.
>  
>  Ted
>  
>  On Thu, Jul 26, 2012 at 8:10 AM, Dave Stoner
>  <dave.stoner(a)northgate-is.com&gt; wrote:
> > I apologise in advance for asking questions which I feel I should have been
> > able to answer from sources on the internet. If you could possibly give me
> > some pointers on where to look it would be so much appreciated.
> >
> >
> >
> > My system is centos 6.2 –
> >
> > Linux MyHostName 2.6.32-220.el6.x86_64 #1 SMP Tue Dec 6 19:48:22
> >
> > GMT 2011 x86_64 x86_64 x86_64 GNU/Linux
> >
> >
> >
> > SELinux mode is set ‘enforced’.
> >
> >
> >
> > I have a proprietary telnet daemon which upon a telnet to port 52000, is
> > started OK when SELinux is disabled. But when it is enabled the same telnet
> > results in /var/log/audit/audit.log showing:
> >
> >
> >
> > type=USER_LOGIN msg=audit(1343048458.345:69): user pid=2536 uid=0 auid=799
> > ses=7 subj=system_u:system_r:inetd_t:s0-s0:c0.c1023 msg='op=login id=799
> > exe="/bin/login" hostname=0.0.0.0 addr=0.0.0.0 termi
> >
> > nal=pts/2 res=success'
> >
> >
> >
> > A normal telnet gives a message similar to above, my telnet adds the
> > following:
> >
> >
> >
> > type=AVC msg=audit(1343048458.353:70): avc:  denied  { entrypoint } for
> > pid=2543 comm="login" path="/bin/bash" dev=sda2 ino=135083
> > scontext=unconfined_u:system_r:qmail_tcp_env_t:s0-s0:c0.c1023 tconte
> >
> > xt=system_u:object_r:shell_exec_t:s0 tclass=file
> >
> >
> >
> > I believe I can create a policy to overcome this using audit2allow, i.e. it
> > comes up with:
> >
> >
> >
> > module mypola 1.0;
> >
> >
> >
> > require {
> >
> >         type qmail_tcp_env_t;
> >
> >         type shell_exec_t;
> >
> >         class file entrypoint;
> >
> > }
> >
> >
> >
> > #============= qmail_tcp_env_t ==============
> >
> > allow qmail_tcp_env_t shell_exec_t:file entrypoint;
> >
> >
> >
> > But it seems to me what I ought to be doing is somehow to get my daemon to
> > run with a domain of ‘remote_logon_t’ as is used by the standard telnet
> > daemon, as here:
> >
> >
> >
> > type=USER_LOGIN msg=audit(1343058924.928:212): user pid=3759 uid=0 auid=799
> > ses=29 subj=system_u:system_r:remote_login_t:s0-s0:c0.c1023 msg='op=login
> > id=799 exe="/bin/login" hostname=localhost addr=::
> >
> > 1 terminal=pts/2 res=success'
> >
> >
> >
> > This is unfamiliar territory and any hints or pointers would really be
> > appreciated.
> >
> >
> >
> > Dave.
> >
> >
> >
> >
> >
> > Dave Stoner
> >
> > Principal Systems Architect
> > Northgate Reality
> >
> > Direct:    [phone] - VPN: 872 2071
> >
> > www.northgate-is.com/reality
> >
> >
> >
> >
> > ________________________________
> >
> > This email is sent on behalf of Northgate Information Solutions Limited and
> > its associated companies ("Northgate") and is strictly confidential and
> > intended solely for the addressee(s).
> >
> >  If you are not the intended recipient of this email you must: (i) not
> > disclose, copy or distribute its contents to any other person nor use its
> > contents in any way or you may be acting unlawfully;  (ii) contact Northgate
> > immediately on [phone] quoting the name of the sender and the
> > addressee then delete it from your system.
> >
> >  Northgate has taken reasonable precautions to ensure that no viruses are
> > contained in this email, but does not accept any responsibility once this
> > email has been transmitted.  You should scan attachments (if any) for
> > viruses.
> >
> >  Northgate Information Solutions Limited. Registered in England no. 06442582
> > -  Northgate Information Solutions UK Limited. Registered in England no.
> > 968498  -  NorthgateArinso UK Limited. Registered in England no. 1587537  -
> > Moorepay Limited.  Registered in England no. 891686  - First Business
> > Support Limited. Registered in England no. 3056267 -   Registered Office:
> > Peoplebuilding 2, Peoplebuilding Estate, Maylands Avenue, Hemel Hempstead,
> > Hertfordshire HP2 4NW
> >
> >  Northgate Managed Services Limited (NI).  Registered in Northern Ireland
> > no. NI032979  -  LearnServe Limited (NI).  Registered in Northern Ireland
> > no. NI043825 Registered Office: Hillview House, 61 Church Road,
> > Newtownabbey, Co. Antrim, BT36 7LQ
> >
> > ________________________________
> >
> >
> > --
> > selinux mailing list
> > selinux(a)lists.fedoraproject.org
> > https://admin.fedoraproject.org/mailman/listinfo/selinux
>  --
>  selinux mailing list
>  selinux(a)lists.fedoraproject.org
>  https://admin.fedoraproject.org/mailman/listinfo/selinux 
Maybe this will help you
as a starting guide.

http://docs.fedoraproject.org/en-US/Fedora/13/html/SELinux_FAQ/index.html

http://docs.fedoraproject.org/en-US/Fedora/13/html/Security-Enhanced_Linu...

There are details there how to obtain denials and make a custom policy.


Regards,
Tristan


-- 
Tristan Santore BSc MBCS
TS4523-RIPE
Network and Infrastructure Operations
InterNexusConnect
Mobile [phone]
Tristan.Santore(a)internexusconnect.net

Former Thawte Notary
(Please note: Thawte has closed its WoT programme down,
and I am therefore no longer able to accredit trust)

For Fedora related issues, please email me at:
TSantore(a)fedoraproject.org

[Dominick Grift]

On Thu, 2012-07-26 at 08:52 -0500, Ted Toth wrote:
>  You could try using the exist telnet policy in ref policy by
> chconing
>  your executable to telnetd_exec_t. However depending on what your
>  custom telnet daemon does you may still get AVCs.
>  
>  Ted 
I agree. i am not familiar with telnet but it might also need
pam/pam_selinux to tell telnet in what context the user should log in.

[Dave Stoner]

Many thanks to you all on this subject. The Fedora SELinux User Guide suggested by
Tristan:

http://docs.fedoraproject.org/en-US/Fedora/13/html/Security-Enhanced_Linu...

was particularly useful, wish I had found that a week earlier. Coverage of the policy
language at:

http://selinuxproject.org/page/PolicyLanguage

Was useful. And the suggestions for applying the telnetd_exec_t type to my executable took
me forward. I then ran into other problems, like write access to files. It seems to me at
this time that I need to set up profiles for the whole of our comms product which looks
like being a project for the next release unfortunately.

Once again, thanks for your assistance.

Dave. 

On Thu, 2012-07-26 at 08:52 -0500, Ted Toth wrote:
>  You could try using the exist telnet policy in ref policy by chconing
>
>  your executable to telnetd_exec_t. However depending on what your 
>  custom telnet daemon does you may still get AVCs.
>  
>  Ted
>  
I agree. i am not familiar with telnet but it might also need pam/pam_selinux to tell
telnet in what context the user should log in.

--
selinux mailing list
selinux(a)lists.fedoraproject.org
https://admin.fedoraproject.org/mailman/listinfo/selinux

-----------------------------------------------------------------------------------------
This email is sent on behalf of Northgate Information Solutions Limited and its associated
companies ("Northgate") and is strictly confidential and intended solely for the
addressee(s).  
 
If you are not the intended recipient of this email you must: (i) not disclose, copy or
distribute its contents to any other person nor use its contents in any way or you may be
acting unlawfully;  (ii) contact Northgate immediately on [phone] quoting the
name of the sender and the addressee then delete it from your system.
 
Northgate has taken reasonable precautions to ensure that no viruses are contained in this
email, but does not accept any responsibility once this email has been transmitted.  You
should scan attachments (if any) for viruses.
 
Northgate Information Solutions Limited. Registered in England no. 06442582  -  Northgate
Information Solutions UK Limited. Registered in England no. 968498  -  NorthgateArinso UK
Limited .Registered in England no. 1587537  -  Moorepay Limited.  Registered in England
no. 891686  - First Business Support Limited. Registered in England no. 3056267 - 
Registered Office: Peoplebuilding 2, Peoplebuilding Estate, Maylands Avenue, Hemel
Hempstead, Hertfordshire HP2 4NW 
 
Northgate Managed Services Limited (NI).  Registered in Northern Ireland no. NI032979  - 
LearnServe Limited (NI).  Registered in Northern Ireland no. NI043825
Registered Office: Hillview House, 61 Church Road, Newtownabbey, Co. Antrim, BT36 7LQ 

-----------------------------------------------------------------------------------------