<s>
System	B-Operating_System
Integrity	I-Operating_System
Protection	I-Operating_System
(	O
SIP	O
,	O
sometimes	O
referred	O
to	O
as	O
rootless	O
)	O
is	O
a	O
security	O
feature	O
of	O
Apple	O
's	O
macOS	B-Application
operating	B-General_Concept
system	I-General_Concept
introduced	O
in	O
OS	B-Operating_System
X	I-Operating_System
El	I-Operating_System
Capitan	I-Operating_System
(	O
2015	O
)	O
(	O
OS	B-Operating_System
X	I-Operating_System
10.11	I-Operating_System
)	O
.	O
</s>
<s>
It	O
comprises	O
a	O
number	O
of	O
mechanisms	O
that	O
are	O
enforced	O
by	O
the	O
kernel	B-Operating_System
.	O
</s>
<s>
A	O
centerpiece	O
is	O
the	O
protection	O
of	O
system-owned	O
files	B-General_Concept
and	O
directories	B-Operating_System
against	O
modifications	O
by	O
processes	O
without	O
a	O
specific	O
"	O
entitlement	O
"	O
,	O
even	O
when	O
executed	O
by	O
the	O
root	B-Application
user	I-Application
or	O
a	O
user	O
with	O
root	B-Application
privileges	I-Application
(	O
sudo	B-Device
)	O
.	O
</s>
<s>
Apple	O
says	O
that	O
the	O
root	B-Application
user	I-Application
can	O
be	O
a	O
significant	O
risk	O
factor	O
to	O
the	O
system	O
's	O
security	O
,	O
especially	O
on	O
systems	O
with	O
a	O
single	O
user	O
account	O
on	O
which	O
that	O
user	O
is	O
also	O
the	O
administrator	O
.	O
</s>
<s>
Apple	O
says	O
that	O
System	B-Operating_System
Integrity	I-Operating_System
Protection	I-Operating_System
is	O
a	O
necessary	O
step	O
to	O
ensure	O
a	O
high	O
level	O
of	O
security	O
.	O
</s>
<s>
In	O
one	O
of	O
the	O
WWDC	O
developer	O
sessions	O
,	O
Apple	O
engineer	O
Pierre-Olivier	O
Martel	O
described	O
unrestricted	O
root	B-Application
access	I-Application
as	O
one	O
of	O
the	O
remaining	O
weaknesses	O
of	O
the	O
system	O
,	O
saying	O
that	O
"[any]	O
piece	O
of	O
malware	O
is	O
one	O
password	O
or	O
vulnerability	O
away	O
from	O
taking	O
full	O
control	O
of	O
the	O
device	O
"	O
.	O
</s>
<s>
He	O
stated	O
that	O
most	O
installations	O
of	O
macOS	B-Application
have	O
only	O
one	O
user	O
account	O
that	O
necessarily	O
carries	O
administrative	O
credentials	O
with	O
it	O
,	O
which	O
means	O
that	O
most	O
users	O
can	O
grant	O
root	B-Application
access	I-Application
to	O
any	O
program	O
that	O
asks	O
for	O
it	O
.	O
</s>
<s>
Restricting	O
the	O
power	O
of	O
root	O
is	O
not	O
unprecedented	O
on	O
macOS	B-Application
.	O
</s>
<s>
For	O
instance	O
,	O
versions	O
of	O
macOS	B-Application
prior	O
to	O
Mac	B-Application
OS	I-Application
X	I-Application
Leopard	I-Application
enforce	O
of	O
securelevel	B-Operating_System
,	O
a	O
security	O
feature	O
that	O
originates	O
in	O
BSD	B-Operating_System
and	O
its	O
derivatives	O
upon	O
which	O
macOS	B-Application
is	O
partially	O
based	O
.	O
</s>
<s>
System	B-Operating_System
Integrity	I-Operating_System
Protection	I-Operating_System
comprises	O
the	O
following	O
mechanisms	O
:	O
</s>
<s>
Protection	O
of	O
contents	O
and	O
file-system	O
permissions	O
of	O
system	B-General_Concept
files	I-General_Concept
and	O
directories	B-Operating_System
;	O
</s>
<s>
Protection	O
of	O
processes	O
against	O
code	O
injection	O
,	O
runtime	O
attachment	O
(	O
like	O
debugging	O
)	O
and	O
DTrace	B-Application
;	O
</s>
<s>
Protection	O
against	O
unsigned	O
kernel	B-Application
extensions	I-Application
(	O
"	O
kexts	B-Application
"	O
)	O
.	O
</s>
<s>
System	B-Operating_System
Integrity	I-Operating_System
Protection	I-Operating_System
protects	O
system	B-General_Concept
files	I-General_Concept
and	O
directories	B-Operating_System
that	O
are	O
flagged	O
for	O
protection	O
.	O
</s>
<s>
This	O
happens	O
either	O
by	O
adding	O
an	O
extended	B-Application
file	I-Application
attribute	I-Application
to	O
a	O
file	O
or	O
directory	O
,	O
by	O
adding	O
the	O
file	O
or	O
directory	O
to	O
or	O
both	O
.	O
</s>
<s>
Among	O
the	O
protected	O
directories	B-Operating_System
are	O
:	O
,	O
,	O
,	O
(	O
but	O
not	O
)	O
.	O
</s>
<s>
The	O
symbolic	O
links	O
from	O
,	O
and	O
to	O
,	O
and	O
are	O
also	O
protected	O
,	O
although	O
the	O
target	O
directories	B-Operating_System
are	O
not	O
themselves	O
protected	O
.	O
</s>
<s>
The	O
kernel	B-Operating_System
,	O
XNU	B-Operating_System
,	O
stops	O
all	O
processes	O
without	O
specific	O
entitlements	O
from	O
modifying	O
the	O
permissions	O
and	O
contents	O
of	O
flagged	O
files	B-General_Concept
and	O
directories	B-Operating_System
and	O
also	O
prevents	O
code	O
injection	O
,	O
runtime	O
attachment	O
and	O
DTrace	B-Application
with	O
respect	O
to	O
protected	O
executables	B-Application
.	O
</s>
<s>
Since	O
OS	B-Device
X	I-Device
Yosemite	I-Device
,	O
kernel	B-Application
extensions	I-Application
,	O
such	O
as	O
drivers	B-Application
,	O
have	O
to	O
be	O
code-signed	O
with	O
a	O
particular	O
Apple	O
entitlement	O
.	O
</s>
<s>
The	O
kernel	B-Operating_System
refuses	O
to	O
boot	B-Operating_System
if	O
unsigned	O
extensions	O
are	O
present	O
,	O
showing	O
the	O
user	O
a	O
prohibition	O
sign	O
instead	O
.	O
</s>
<s>
This	O
mechanism	O
,	O
called	O
"	O
kext	B-Operating_System
signing	I-Operating_System
"	O
,	O
was	O
integrated	O
into	O
System	B-Operating_System
Integrity	I-Operating_System
Protection	I-Operating_System
.	O
</s>
<s>
System	B-Operating_System
Integrity	I-Operating_System
Protection	I-Operating_System
will	O
also	O
sanitize	O
certain	O
environmental	O
variables	O
when	O
calling	O
system	O
programs	O
when	O
SIP	O
is	O
in	O
effect	O
.	O
</s>
<s>
The	O
directories	B-Operating_System
protected	O
by	O
SIP	O
by	O
default	O
include	O
:	O
</s>
<s>
/Applications	O
is	O
protected	O
for	O
apps	O
that	O
are	O
pre-installed	O
with	O
Mac	B-Application
OS	I-Application
,	O
such	O
as	O
Calendar	O
,	O
Photos	O
,	O
Safari	O
,	O
Terminal	B-Application
,	O
Console	O
,	O
App	O
Store	O
,	O
and	O
Notes	O
.	O
</s>
<s>
System	B-Operating_System
Integrity	I-Operating_System
Protection	I-Operating_System
can	O
only	O
be	O
disabled	O
(	O
either	O
wholly	O
or	O
partly	O
)	O
from	O
outside	O
of	O
the	O
system	B-Application
partition	I-Application
.	O
</s>
<s>
To	O
that	O
end	O
,	O
Apple	O
provides	O
the	O
command-line	B-Device
utility	I-Device
which	O
can	O
be	O
executed	O
from	O
a	O
Terminal	B-Application
window	O
within	O
the	O
recovery	B-Operating_System
system	I-Operating_System
or	O
a	O
bootable	B-Operating_System
macOS	B-Application
installation	O
disk	O
,	O
which	O
adds	O
a	O
boot	B-Operating_System
argument	O
to	O
the	O
device	O
's	O
NVRAM	B-General_Concept
.	O
</s>
<s>
This	O
applies	O
the	O
setting	O
to	O
all	O
of	O
the	O
installations	O
of	O
El	O
Capitan	O
or	O
macOS	B-Operating_System
Sierra	I-Operating_System
on	O
the	O
device	O
.	O
</s>
<s>
Upon	O
installation	O
of	O
macOS	B-Application
,	O
the	O
installer	O
moves	O
any	O
unknown	O
components	O
within	O
flagged	O
system	O
directories	B-Operating_System
to	O
.	O
</s>
<s>
By	O
preventing	O
write	O
access	O
to	O
system	O
directories	B-Operating_System
,	O
the	O
system	B-General_Concept
file	I-General_Concept
and	O
directory	O
permissions	O
are	O
maintained	O
automatically	O
during	O
Apple	O
software	O
updates	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
permissions	B-Operating_System
repair	I-Operating_System
is	O
not	O
available	O
in	O
Disk	B-Application
Utility	I-Application
and	O
the	O
corresponding	O
operation	O
.	O
</s>
<s>
Reception	O
of	O
System	B-Operating_System
Integrity	I-Operating_System
Protection	I-Operating_System
has	O
been	O
mixed	O
.	O
</s>
<s>
Macworld	O
expressed	O
the	O
concern	O
that	O
Apple	O
could	O
take	O
full	O
control	O
away	O
from	O
users	O
and	O
developers	O
in	O
future	O
releases	O
and	O
move	O
the	O
security	O
policy	O
of	O
macOS	B-Application
slowly	O
toward	O
that	O
of	O
Apple	O
's	O
mobile	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
iOS	B-Application
,	O
whereupon	O
the	O
installation	O
of	O
many	O
utilities	O
and	O
modifications	O
requires	O
jailbreaking	B-Application
.	O
</s>
<s>
Some	O
applications	O
and	O
drivers	B-Application
will	O
not	O
work	O
to	O
their	O
full	O
extent	O
or	O
cannot	O
be	O
operated	O
at	O
all	O
unless	O
the	O
feature	O
is	O
disabled	O
,	O
either	O
temporarily	O
or	O
permanently	O
.	O
</s>
<s>
However	O
,	O
they	O
also	O
remarked	O
that	O
by	O
far	O
most	O
users	O
,	O
including	O
power	B-General_Concept
users	I-General_Concept
,	O
will	O
not	O
have	O
a	O
reason	O
to	O
turn	O
the	O
feature	O
off	O
,	O
saying	O
that	O
there	O
are	O
"	O
almost	O
no	O
downsides	O
"	O
to	O
it	O
.	O
</s>
