The selinux repo has more up to date and digestible documentation: https://github.com/SELinuxProject/selinux/tree/master/secilc/docs > On Sep 11, 2018, at 2:49 PM, Ted Toth <txtoth@xxxxxxxxx> wrote: > > Yes I too noticed the translate permission but couldn't find any info related to it intended purpose. Regarding CIL unfortunately I have zero experience with it but I've installed the compiler and started reading through https://github.com/SELinuxProject/cil/wiki (any other pointers to useful info would be appreciated). I have written lots of policy would it be possible to add a class/permissions/mlsconstraints in an old-fashion policy module? > > On Tue, Sep 11, 2018 at 1:27 PM Stephen Smalley <sds@xxxxxxxxxxxxx> wrote: > On 09/11/2018 10:41 AM, Stephen Smalley wrote: > > On 09/10/2018 06:30 PM, Ted Toth wrote: > >> mcstrans mcscolor.c also uses the same logic I'd been using to check > >> dominance so this too will no longer function as expected on el7. Do > >> you any suggestions for doing a 'generic' (one not tied to a specific > >> resource class) dominance check in lieu of context contains? > > > > You should probably define your own permission with its own constraint > > to avoid depending on the base policy's particular constraint > > definitions. Certainly for your own code. For mcstrans, mcscolor > > probably ought to be switched to using at least a separate permission in > > the context class if not its own class to avoid overloading the meaning > > with pam_selinux's usage (or vice versa, but likely harder to change > > pam_selinux at this point). > > > > It is possible to define an entirely new class, its permissions, and its > > mls constraints via a CIL module IIUC, without needing to change the > > base policy. > > > > I don't think you can add a permission to an existing class via a CIL > > module currently, unfortunately, so you can't just extend the context > > class without modifying the base policy. So it may be easier to define > > an entirely new class. > > > > The class and permission ought to be specific to the usage. For > > example, mcstrans could have its own class (mcstrans) with its own > > permissions (e.g. color_match or color_use or ...) that abstract away > > the logical check being performed. Dominance checks performed for > > different reasons ought to use different permissions so that one can > > distinguish what TE pairs are allowed them. > > > > Your code could likewise define and use its own class and permission. > > > > Does that make sense? > > BTW, I noticed there is another permission ("translate") defined in the > context class and its constraint is ((h1 dom h2) or (t1 == > mlstranslate)). I would have guessed that it was intended as a > front-end service check over what processes could request context > translations from mcstrans or what contexts they could translate, but I > don't see it being used in mcstrans anywhere. Is this a legacy thing > from early setransd/mcstransd days? There is a TODO comment in mcstrans > process_request() that suggests there was an intent to perform a > dominance check between the requester context and the specified context, > but that's not implemented. Appears to be allowed in current policy for > all domains to the setrans_t domain itself. > > > > >> > >> Ted > >> > >> On Mon, Sep 10, 2018 at 1:19 PM Ted Toth <txtoth@xxxxxxxxx > >> <mailto:txtoth@xxxxxxxxx>> wrote: > >> > >> Understood, thanks. > >> > >> On Mon, Sep 10, 2018 at 12:46 PM Stephen Smalley <sds@xxxxxxxxxxxxx > >> <mailto:sds@xxxxxxxxxxxxx>> wrote: > >> > >> On 09/10/2018 01:13 PM, Ted Toth wrote: > >> > We currently have code running on el6 that does a MLS > >> dominance check by > >> > calling security_compute_av_raw with the security object class > >> > SECCLASS_CONTEXT with permission CONTEXT__CONTAINS as you can > >> see in the > >> > python code below. When I run this code on el6 s1 dominates > >> s0 however > >> > when I run the same code on el7 s1 does not dominate s0. On > >> both systems > >> > the file read dominance check works as expected. Can anyone > >> help me > >> > understand why the context contains check does not work the > >> same on both > >> > systems? > >> > >> That would depend entirely on how the constraint is written in > >> the > >> policy. I assume this is with the -mls policy on both? seinfo > >> --constrain | grep -C1 context would show you the constraint > >> in the > >> kernel policy. > >> > >> Looks like refpolicy defines it as: > >> mlsconstrain context contains > >> (( h1 dom h2 ) and ( l1 domby l2)); > >> > >> The 2nd part of the constraint was introduced by: > >> commit 4c365f4a6a6f933dd13b0127e03f832c6a6cf8fc > >> Author: Harry Ciao <qingtao.cao@xxxxxxxxxxxxx > >> <mailto:qingtao.cao@xxxxxxxxxxxxx>> > >> Date: Tue Feb 15 10:16:32 2011 +0800 > >> > >> l1 domby l2 for contains MLS constraint > >> > >> As identified by Stephan Smalley, the current MLS > >> constraint for the > >> contains permission of the context class should consider > >> the current > >> level of a user along with the clearance level so that > >> mls_systemlow > >> is no longer considered contained in mls_systemhigh. > >> > >> Signed-off-by: Harry Ciao <qingtao.cao@xxxxxxxxxxxxx > >> <mailto:qingtao.cao@xxxxxxxxxxxxx>> > >> > >> This was to prevent a user from logging in at a level below their > >> authorized range, in the unusual scenario where the user's low > >> level was > >> not s0/systemlow. > >> > >> > > >> > Ted > >> > > >> > > >> > >> --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- > >> > >> > > >> > import selinux > >> > > >> > SECCLASS_CONTEXT = selinux.string_to_security_class("context") > >> > CONTEXT__CONTAINS = > >> selinux.string_to_av_perm(SECCLASS_CONTEXT, "contains") > >> > SECCLASS_FILE = selinux.string_to_security_class("file") > >> > FILE__READ = selinux.string_to_av_perm(SECCLASS_FILE, "read") > >> > > >> > raw_con1 = "user_u:user_r:user_t:s1" > >> > raw_con2 = "user_u:user_r:user_t:s0" > >> > > >> > avd = selinux.av_decision() > >> > selinux.avc_reset() > >> > try: > >> > rc = selinux.security_compute_av_raw(raw_con1, raw_con2, > >> > SECCLASS_CONTEXT, CONTEXT__CONTAINS, avd) > >> > if rc < 0: > >> > print("selinux.security_compute_av_raw failed for %s > >> %s" % > >> > (raw_con1, raw_con2)) > >> > if (avd.allowed & CONTEXT__CONTAINS) == > >> CONTEXT__CONTAINS: > >> > print("%s dominates %s" % (raw_con1, raw_con2)) > >> > else: > >> > print("%s does not dominate %s" % (raw_con1, > >> raw_con2)) > >> > except OSError, ex: > >> > print "exception calling > >> selinux.security_compute_av_raw", ex > >> > > >> > avd = selinux.av_decision() > >> > selinux.avc_reset() > >> > try: > >> > rc = selinux.security_compute_av_raw(raw_con1, raw_con2, > >> > SECCLASS_FILE, FILE__READ, avd) > >> > if rc < 0: > >> > print("selinux.security_compute_av_raw failed for %s > >> %s" % > >> > (raw_con1, raw_con2)) > >> > if (avd.allowed & FILE__READ) == FILE__READ: > >> > print("%s dominates %s" % (raw_con1, raw_con2)) > >> > else: > >> > print("%s does not dominate %s" % (raw_con1, > >> raw_con2)) > >> > > >> > except OSError: > >> > print "exception calling > >> selinux.security_compute_av_raw", ex > >> > > >> > > >> > > >> > _______________________________________________ > >> > Selinux mailing list > >> > Selinux@xxxxxxxxxxxxx <mailto:Selinux@xxxxxxxxxxxxx> > >> > To unsubscribe, send email to Selinux-leave@xxxxxxxxxxxxx > >> <mailto:Selinux-leave@xxxxxxxxxxxxx>. > >> > To get help, send an email containing "help" to > >> Selinux-request@xxxxxxxxxxxxx > >> <mailto:Selinux-request@xxxxxxxxxxxxx>. > >> > > >> > > > > _______________________________________________ > Selinux mailing list > Selinux@xxxxxxxxxxxxx > To unsubscribe, send email to Selinux-leave@xxxxxxxxxxxxx. > To get help, send an email containing "help" to Selinux-request@xxxxxxxxxxxxx. _______________________________________________ Selinux mailing list Selinux@xxxxxxxxxxxxx To unsubscribe, send email to Selinux-leave@xxxxxxxxxxxxx. 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