Samba and krb5.conf

[Kenny Dinh]

> Set the environment variable KRB5_CONFIG to another file in the samba
> unit file/startup script ?

I'm not sure I understood this approach.  Could you help elaborate?  Are
you referring to Samba4/InitScript or the /etc/rc.d/init.d/smb script file?
My understanding is that smbd is run as a service so all environment
variables such as KRB5_CONFIG will be discarded.


On Fri, Apr 17, 2015 at 3:02 PM, Simo <simo at samba.org> wrote:

> On Fri, 2015-04-17 at 14:16 -0700, Kenny Dinh wrote:
> > Richard,
> >
> > It is possible to run the conflicting application in a container, but I
> > cannot prevent future applications.
> >
> > I will look into the alternative method, make the kerberos libraries
> linked
> > to Samba use a different location of krb5.conf rather than
> /etc/krb5.conf.
> > I have been looking at the wrong place all this time.
> >
> > Thanks for the pointer!
> > ~Kenny
>
> Set the environment variable KRB5_CONFIG to another file in the samba
> unit file/startup script ?
>
> Simo.
>
> > On Fri, Apr 17, 2015 at 2:02 PM, Richard Sharpe <
> realrichardsharpe at gmail.com
> > > wrote:
> >
> > > On Fri, Apr 17, 2015 at 1:09 PM, Kenny Dinh <kdinh at peaxy.net> wrote:
> > > > Greeting,
> > > >
> > > > We are using Samba 4.1.13 on CentOS and was having issue
> authenticating
> > > > user that was created in a subdomain.
> > > >
> > > > We found out that another application had updated the /etc/krb5.conf
> to
> > > > match its need, and Samba was not happy about it.  When we deleted
> the
> > > > /etc/krb5.conf, Samba was able to authenticate user from a subdomain
> > > > (smbclient //localhost/share -U<subdomain>\\<user>%<password>)
> > > >
> > > > Note that SAMBA4_USES_HEIMDAL was not defined.
> > > > This is my smb.conf
> > > >
> > > > # net conf list
> > > > [global]
> > > > idmap config *:backend = tdb
> > > > idmap config *:range = 1000000-100000000
> > > > idmap config *:script = /usr/mydir/bin/idmap
> > > > workgroup = REPUBLIC
> > > > realm = REPUBLIC.WINDC
> > > > security = ads
> > > > netbios name = testbox1
> > > > log level = 10
> > > >
> > > > [blah]
> > > > path = /
> > > > comment = sdakjhkjh
> > > > guest ok = no
> > > > read only = no
> > > > browseable = yes
> > > >
> > > > I noticed that the code path went
> > > > through create_local_private_krb5_conf_for_domain() function and
> created
> > > > its own krb5.conf.  Toward the end of the function, the code also
> set the
> > > > KRB5_CONFIG environment variable to "
> > > > /var/lib/samba/smb_krb5/krb5.conf.REPUBLIC"
> > > >
> > > > Here's a snippet of the log:
> > > > /var/log/samba/log.smbd:[2015/04/17 10:19:25.083196,  5, pid=9003,
> > > > effective(0, 0), real(0, 0)]
> > > >
> > >
> ../source3/libads/kerberos.c:925(create_local_private_krb5_conf_for_domain)
> > > > /var/log/samba/log.smbd:  create_local_private_krb5_conf_for_domain:
> > > wrote
> > > > file /var/lib/samba/smb_krb5/krb5.conf.REPUBLIC with realm
> REPUBLIC.WINDC
> > > > KDC list = kdc = 10.0.3.1
> > > >
> > > > I searched through samba code for krb5.conf and found that
> > > > "krb5_config_file" in source4\heimdal\lib\krb5\constants.c seems to
> be
> > > the
> > > > only place that make use of krb5.conf files location.  Also the
> function
> > > > where "krb5_config_file" is used in krb5_init_context() defined in
> > > > source4\heimdal\lib\krb5\context.c.  However, it seems that the code
> was
> > > > never executed.  I place additional DEBUG message in that code path
> but
> > > > none appear.
> > > >
> > > > This is the variable I was referring to.
> > > > KRB5_LIB_VARIABLE const char *krb5_config_file =
> > > >
> > > > It seems Samba expects the default location for krb5.conf to be
> located
> > > at
> > > > /etc/krb5.conf.  However, I couldn't find the location in the code
> where
> > > > Samba is looking for /etc/krb5.conf.  Another thing that confuses me
> is
> > > why
> > > > does Samba look into /etc/krb5.conf when it was already creating its
> own
> > > > krb5.conf file.
> > > >
> > > > My goal is to prevent Samba from looking at /etc/krb5.conf to avoid
> > > > conflicts between Samba and any other applications that would modify
> > > > /etc/krb5.conf.
> > > >
> > > > Could someone point me to the code to do that?
> > >
> > > It's likely the kerberos libraries that are looking in that file.
> > > Samba really works best if you tell it to use DNS to look up services
> > > and realms, so an empty krb5.conf file works.
> > >
> > > However, if you need a krb5.conf for another application, is it
> > > possible to run that application in a jail or container?
> > >
> > > Alternatively, you might have to make the kerberos libraries linked to
> > > Samba use a different location or not use krb5.conf.
> > >
> > > --
> > > Regards,
> > > Richard Sharpe
> > > (何以解憂？唯有杜康。--曹操)
> > >
>
>
> --
> Simo Sorce
>
>