lkml.org 
[lkml]   [2009]   [Jul]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH -v3 1/3] Capabilities: move cap_file_mmap to commoncap.c
    From
    Date
    On Thu, 2009-07-30 at 13:50 -0400, Eric Paris wrote:
    > On Thu, 2009-07-30 at 11:58 -0400, Stephen Smalley wrote:
    > > On Thu, 2009-07-30 at 10:54 -0500, Serge E. Hallyn wrote:
    > > > Quoting Eric Paris (eparis@redhat.com):
    > > > > On Thu, 2009-07-30 at 00:14 -0500, Serge E. Hallyn wrote:
    > > > > > Quoting Eric Paris (eparis@redhat.com):
    > > > > > > Currently we duplicate the mmap_min_addr test in cap_file_mmap and in
    > > > > > > security_file_mmap if !CONFIG_SECURITY. This patch moves cap_file_mmap
    > > > > > > into commoncap.c and then calls that function directly from
    > > > > > > security_file_mmap ifndef CONFIG_SECURITY like all of the other capability
    > > > > > > checks are done.
    > > > > >
    > > > > > It also
    > > > > >
    > > > > > 1. changes the return value in error case from -EACCES to
    > > > > > -EPERM
    > > > > > 2. no onger sets PF_SUPERPRIV in t->flags if the capability
    > > > > > is used.
    > > > > >
    > > > > > Do we care about these?
    > > > >
    > > > > Personally, not really, but I'll gladly put them back if you care. #2
    > > > > seems more interesting to me than number 1. I actually kinda like
    > > > > getting EPERM from caps rather than EACCES since them I know if I was
    > > > > denied by selinux or by caps.....
    > > > >
    > > > > -Eric
    > > >
    > > > Yup, I asked bc I didn't particularly care myself.
    > > >
    > > > I think I agree with you about -EPERM being better anyway. However I
    > > > (now) think in this case PF_SUPERPRIV definately should be set, as this
    > > > is a clear use of a capability to do something that couldn't have been
    > > > done without it.
    > >
    > > On a related but different note, we should consider all current uses of
    > > cap_capable(), as they represent capability checks that will not be
    > > subject to a further restrictive check by other security modules. In
    > > this case and in the vm_enough_memory case, that is intentional, but not
    > > so clear for other uses in commoncap.c.
    >
    > Most of commoncap.c is called either as a secondary hook from the active
    > lsm (aka selinux calls the commoncap.c functions) or in the !
    > CONFIG_SECURITY case.
    >
    > I'll audit this afternoon to see which of them might not fit these
    > rules....

    That isn't what I meant. Most of the commoncap functions call capable()
    rather than directly calling cap_capable(), thereby causing:
    - PF_SUPERPRIV to be set, and
    - The primary security module (e.g. SELinux) to apply its own
    restrictive check.

    That is useful as it allows SELinux or AppArmor or TOMOYO to veto e.g.
    CAP_SYS_PTRACE without replicating the same logic within its own hook.

    The current exceptions are:
    cap_inh_is_capped() called from cap_capset(),
    cap_task_prctl() in the PR_SET_SECUREBITS case,
    cap_vm_enough_memory(),
    cap_file_mmap() after your patch.

    The latter two are indeed cases where we made a conscious choice that
    SELinux would not apply its capability check against policy. But the
    first two are unclear to me.

    --
    Stephen Smalley
    National Security Agency



    \
     
     \ /
      Last update: 2009-07-30 21:45    [W:0.024 / U:91.504 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site