Re: [PATCH] scripts/selinux: modernize mdp

From: Dominick Grift <dominick.grift@defensec.nl>
To: selinux@vger.kernel.org
Subject: Re: [PATCH] scripts/selinux: modernize mdp
Date: Wed, 20 Feb 2019 15:47:42 +0100	[thread overview]
Message-ID: <20190220144742.GB10412@brutus.lan> (raw)
In-Reply-To: <20190220140922.GA10412@brutus.lan>

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?

> 
> > 
> > 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
> > 
> 
> -- 
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> Dominick Grift

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Dominick Grift