[refpolicy] [PATCH v1 5/5] Udev's tables (run data) is stored in directories

[sven.vermeulen@siphos.be (Sven Vermeulen)]

On Wed, Aug 29, 2012 at 09:37:55PM +0200, Dominick Grift wrote:
> > -# create udev database in /dev/.udevdb
> > -allow udev_t udev_tbl_t:file manage_file_perms;
> > +allow udev_t udev_tbl_t:dir relabelto;
> > +manage_dirs_pattern(udev_t, udev_tbl_t, udev_tbl_t)
> > +manage_files_pattern(udev_t, udev_tbl_t, udev_tbl_t)
> > +manage_lnk_files_pattern(udev_t, udev_tbl_t, udev_tbl_t)
> > +
> >  dev_filetrans(udev_t, udev_tbl_t, file)
> 
> This doesnt make sense to me.
> 
> First we had:
> 
> allow udev_t udev_tbl_t:file manage_file_perms;
> dev_filetrans(udev_t, udev_tbl_t, file)
> 
> with these specs:
> 
> /dev/\.udev(/.*)? --	gen_context(system_u:object_r:udev_tbl_t,s0)
> /dev/\.udevdb	--	gen_context(system_u:object_r:udev_tbl_t,s0)
> /dev/udev\.tbl	--	gen_context(system_u:object_r:udev_tbl_t,s0)
> 
> What does this tell me?
> 
> Well there shouldnt be any dirs and symlinks with type udev_tbl_t.
> 
> Only files. dirs and lnk_files should be device_t.

Well, the udev code (looking at udev-182 here) has the code for relabeling
in it. For instance, when copy_dev_dir is called, it has

#v+
                        udev_selinux_setfscreateconat(udev, dirfd(dir_to), dent->d_name, S_IFDIR|0755);
                        mkdirat(dirfd(dir_to), dent->d_name, 0755);
                        udev_selinux_resetfscreatecon(udev);
#v-

I believe this is the source, but I'm no master in this. I mainly based
myself on the denials and errors I got. If I put in an "auditallow" to show
this, this is the result:

#v+
testsys ~ # grep grant /var/log/avc.log
Aug 29 21:51:23 testsys kernel: [    3.339771] type=1400 audit(1346269880.338:6): avc:  granted  { create } for  pid=1162
comm="systemd-udevd" name="data" scontext=system_u:system_r:udev_t tcontext=system_u:object_r:udev_tbl_t tclass=dir
#v-

This, btw, is for the /var/run/udev/data location, and the file contexts for
udev does hold this as a udev_tbl_t currently:

#v+
testsys ~ # grep udev_tbl_t udev.fc
/dev/\.udev(/.*)? --    gen_context(system_u:object_r:udev_tbl_t,s0)
/dev/\.udevdb   --      gen_context(system_u:object_r:udev_tbl_t,s0)
/dev/udev\.tbl  --      gen_context(system_u:object_r:udev_tbl_t,s0)
/var/run/udev(/.*)?     gen_context(system_u:object_r:udev_tbl_t,s0)
#v-

(last line)

Wkr,
	Sven Vermeulen