Re: [PATCH] scripts/selinux: modernize mdp

[Stephen Smalley <stephen.smalley@gmail.com>]

On Wed, Feb 20, 2019 at 9:48 AM Dominick Grift
<dominick.grift@defensec.nl> wrote:
>
> On Wed, Feb 20, 2019 at 03:09:22PM +0100, Dominick Grift wrote:
> > On Wed, Feb 20, 2019 at 01:33:54PM +0100, Dominick Grift wrote:
> > > The MDP example no longer works on modern systems.
> > >
> > > Add support for devtmpfs. This is required by login programs to relabel terminals.
> > > Compile the policy with deny_unknown allow status to anticipate user space object managers in core components such as systemd.
> > > Add default seusers mapping and failsafe context for the SELinux PAM module.
> >
> > There are a couple more possible improvements that i have identified:
> >
> > Fail gracefully if checkpolicy does not exist
> > Run setfiles with -F. There *might* be one scenario where this might be a good idea. Where the filesystem is labeled with invalid contexts but where SELinux is disabled.
> > In that case setfiles will reset, but only types (I suppose)
>
> This also does not make sense to me:
>
>         if [ -f /sbin/setfiles ]; then
>            SF="/usr/setfiles"
>
> I think "-f /usr/setfiles" was meant here? I suppose `which setfiles` only searches "PATH", and so it wouldnt find /usr/setfiles.
> But then, who uses /usr/setfiles?

No one AFAIK. So I agree that this does not make sense.  Might have
been a broken attempt to support either /sbin/setfiles or
/usr/sbin/setfiles as the install location of setfiles, since that did
change at some point.

>
> >
> > >
> > > Signed-off-by: Dominick Grift <dominick.grift@defensec.nl>
> > > ---
> > >  scripts/selinux/install_policy.sh | 6 +++++-
> > >  scripts/selinux/mdp/mdp.c         | 1 +
> > >  2 files changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/scripts/selinux/install_policy.sh b/scripts/selinux/install_policy.sh
> > > index 0b86c47baf7d..334fcf8903d5 100755
> > > --- a/scripts/selinux/install_policy.sh
> > > +++ b/scripts/selinux/install_policy.sh
> > > @@ -20,14 +20,18 @@ CP=`which checkpolicy`
> > >  VERS=`$CP -V | awk '{print $1}'`
> > >
> > >  ./mdp policy.conf file_contexts
> > > -$CP -o policy.$VERS policy.conf
> > > +$CP -U allow -o policy.$VERS policy.conf
> > >
> > >  mkdir -p /etc/selinux/dummy/policy
> > >  mkdir -p /etc/selinux/dummy/contexts/files
> > >
> > > +echo "__default__:user_u" > /etc/selinux/dummy/seusers
> > > +echo "base_r:base_t" > /etc/selinux/dummy/contexts/failsafe_context
> > > +
> > >  cp file_contexts /etc/selinux/dummy/contexts/files
> > >  cp dbus_contexts /etc/selinux/dummy/contexts
> > >  cp policy.$VERS /etc/selinux/dummy/policy
> > > +
> > >  FC_FILE=/etc/selinux/dummy/contexts/files/file_contexts
> > >
> > >  if [ ! -d /etc/selinux ]; then
> > > diff --git a/scripts/selinux/mdp/mdp.c b/scripts/selinux/mdp/mdp.c
> > > index 073fe7537f6c..cf06d5694cbc 100644
> > > --- a/scripts/selinux/mdp/mdp.c
> > > +++ b/scripts/selinux/mdp/mdp.c
> > > @@ -131,6 +131,7 @@ int main(int argc, char *argv[])
> > >
> > >     fprintf(fout, "fs_use_trans mqueue user_u:base_r:base_t;\n");
> > >     fprintf(fout, "fs_use_trans devpts user_u:base_r:base_t;\n");
> > > +   fprintf(fout, "fs_use_trans devtmpfs user_u:base_r:base_t;\n");
> > >     fprintf(fout, "fs_use_trans hugetlbfs user_u:base_r:base_t;\n");
> > >     fprintf(fout, "fs_use_trans tmpfs user_u:base_r:base_t;\n");
> > >     fprintf(fout, "fs_use_trans shm user_u:base_r:base_t;\n");
> > > --
> > > 2.21.0.rc1
> > >
> >
> > --
> > Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
> > https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
> > Dominick Grift
>
> --
> Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
> https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
> Dominick Grift