On Thu, Feb 26, 2015 at 12:55 PM, Serge E. Hallyn [off-list ref] wrote:
On Thu, Feb 26, 2015 at 12:51:57PM -0800, Andy Lutomirski wrote:
quoted
On Thu, Feb 26, 2015 at 12:34 PM, Serge E. Hallyn [off-list ref] wrote:
quoted
On Thu, Feb 26, 2015 at 02:13:00PM -0600, Christoph Lameter wrote:
quoted
On Thu, 26 Feb 2015, Serge E. Hallyn wrote:
quoted
Andrew Morgan was against that. What if we changed
pE' = pP' & (fE | pA)
to
if (pA)
pE' = pP' & fE
else
pE' = pP'
Same problem as before. The ambient bits will not be set in pE'.
And what if I weren't scatterbrained and we did
if (pA)
pE' = pP'
else
pE' = pP' & fE
All pP' bits would be set in pE'.
That seems reasonable to me, except for my paranoia:
What if there's a program with CAP_DAC_OVERRIDE in fP and fE set to
the empty set (i.e. the magic effective bit cleared), and the program
relies on that. A malicious user has CAP_NET_BIND and sets pA =
CAP_NET_BIND. Boom!
If we changed that to if (pA') and zeroed pA if fP is non-empty then
this problem goes away.
Hm, the problem is that then the empty pA is inherited by children.
I do see that any program with fP set should probably run with only
what it requested. Would
if (pA && is_empty(fP))
pE' = pP'
else
pE' = pP' & fE
help? Or are you worried about a program with fP set which then
executes other programs?
The particular worry I expressed there was just about pE.
I'm still extremely nervous about allowing nonempty pA to propagate to
setuid or nonzero fP programs. It's less obviously dangerous if pA is
never a superset of pP, but it could still cause problems with setuid
programs that execute intentionally deprivileged helpers.
--Andy