abstract the securelevel implementation details from the checking
code. The call in -CURRENT accepts a struct ucred--in -STABLE, it
will accept struct proc. This facilitates the upcoming commit of
per-jail securelevel support. The calls will also generate a
kernel printf if the calls are made with NULL ucred/proc pointers:
generally speaking, there are few instances of this, and they should
be fixed.
o Update p_candebug() to use securelevel_gt(); future updates to the
remainder of the kernel tree will be committed soon.
Obtained from: TrustedBSD Project
Note ALL MODULES MUST BE RECOMPILED
make the kernel aware that there are smaller units of scheduling than the
process. (but only allow one thread per process at this time).
This is functionally equivalent to teh previousl -current except
that there is a thread associated with each process.
Sorry john! (your next MFC will be a doosie!)
Reviewed by: peter@freebsd.org, dillon@freebsd.org
X-MFC after: ha ha ha ha
by renaming it to kern.security.suser_enabled. This makes the name
consistent with other use: "permitted" now refers to a specific right
or privilege, whereas "enabled" refers to a feature. As this hasn't
been MFC'd, and using this destroys a running system currently, I believe
the user base of the sysctl will not be too unhappy.
o While I'm at it, un-staticize and export the supporting variable, as it
will be used by kern_cap.c shortly.
Obtained from: TrustedBSD Project
of debugging the current process when that is in conflict with other
restrictions (such as jail, unprivileged_procdebug_permitted, etc).
o This corrects anomolies in the behavior of
kern.security.unprivileged_procdebug_permitted when using truss and
ktrace. The theory goes that this is now safe to use.
Obtained from: TrustedBSD Project
MIB entries.
o Relocate kern.suser_permitted to kern.security.suser_permitted.
o Introduce new kern.security.unprivileged_procdebug_permitted, which
(when set to 0) prevents processes without privilege from performing
a variety of inter-process debugging activities. The default is 1,
to provide current behavior.
This feature allows "hardened" systems to disable access to debugging
facilities, which have been associated with a number of past security
vulnerabilities. Previously, while procfs could be unmounted, other
in-kernel facilities (such as ptrace()) were still available. This
setting should not be modified on normal development systems, as it
will result in frustration. Some utilities respond poorly to
failing to get the debugging access they require, and error response
by these utilities may be improved in the future in the name of
beautification.
Note that there are currently some odd interactions with some
facilities, which will need to be resolved before this should be used
in production, including odd interactions with truss and ktrace.
Note also that currently, tracing is permitted on the current process
regardless of this flag, for compatibility with previous
authorization code in various facilities, but that will probably
change (and resolve the odd interactions).
Obtained from: TrustedBSD Project
The p_can(...) construct was a premature (and, it turns out,
awkward) abstraction. The individual calls to p_canxxx() better
reflect differences between the inter-process authorization checks,
such as differing checks based on the type of signal. This has
a side effect of improving code readability.
o Replace direct credential authorization checks in ktrace() with
invocation of p_candebug(), while maintaining the special case
check of KTR_ROOT. This allows ktrace() to "play more nicely"
with new mandatory access control schemes, as well as making its
authorization checks consistent with other "debugging class"
checks.
o Eliminate "privused" construct for p_can*() calls which allowed the
caller to determine if privilege was required for successful
evaluation of the access control check. This primitive is currently
unused, and as such, serves only to complicate the API.
Approved by: ({procfs,linprocfs} changes) des
Obtained from: TrustedBSD Project
real uid, saved uid, real gid, and saved gid to ucred, as well as the
pcred->pc_uidinfo, which was associated with the real uid, only rename
it to cr_ruidinfo so as not to conflict with cr_uidinfo, which
corresponds to the effective uid.
o Remove p_cred from struct proc; add p_ucred to struct proc, replacing
original macro that pointed.
p->p_ucred to p->p_cred->pc_ucred.
o Universally update code so that it makes use of ucred instead of pcred,
p->p_ucred instead of p->p_pcred, cr_ruidinfo instead of p_uidinfo,
cr_{r,sv}{u,g}id instead of p_*, etc.
o Remove pcred0 and its initialization from init_main.c; initialize
cr_ruidinfo there.
o Restruction many credential modification chunks to always crdup while
we figure out locking and optimizations; generally speaking, this
means moving to a structure like this:
newcred = crdup(oldcred);
...
p->p_ucred = newcred;
crfree(oldcred);
It's not race-free, but better than nothing. There are also races
in sys_process.c, all inter-process authorization, fork, exec, and
exit.
o Remove sigio->sio_ruid since sigio->sio_ucred now contains the ruid;
remove comments indicating that the old arrangement was a problem.
o Restructure exec1() a little to use newcred/oldcred arrangement, and
use improved uid management primitives.
o Clean up exit1() so as to do less work in credential cleanup due to
pcred removal.
o Clean up fork1() so as to do less work in credential cleanup and
allocation.
o Clean up ktrcanset() to take into account changes, and move to using
suser_xxx() instead of performing a direct uid==0 comparision.
o Improve commenting in various kern_prot.c credential modification
calls to better document current behavior. In a couple of places,
current behavior is a little questionable and we need to check
POSIX.1 to make sure it's "right". More commenting work still
remains to be done.
o Update credential management calls, such as crfree(), to take into
account new ruidinfo reference.
o Modify or add the following uid and gid helper routines:
change_euid()
change_egid()
change_ruid()
change_rgid()
change_svuid()
change_svgid()
In each case, the call now acts on a credential not a process, and as
such no longer requires more complicated process locking/etc. They
now assume the caller will do any necessary allocation of an
exclusive credential reference. Each is commented to document its
reference requirements.
o CANSIGIO() is simplified to require only credentials, not processes
and pcreds.
o Remove lots of (p_pcred==NULL) checks.
o Add an XXX to authorization code in nfs_lock.c, since it's
questionable, and needs to be considered carefully.
o Simplify posix4 authorization code to require only credentials, not
processes and pcreds. Note that this authorization, as well as
CANSIGIO(), needs to be updated to use the p_cansignal() and
p_cansched() centralized authorization routines, as they currently
do not take into account some desirable restrictions that are handled
by the centralized routines, as well as being inconsistent with other
similar authorization instances.
o Update libkvm to take these changes into account.
Obtained from: TrustedBSD Project
Reviewed by: green, bde, jhb, freebsd-arch, freebsd-audit
follows: the effective uid of p1 (subject) must equal the real, saved,
and effective uids of p2 (object), p2 must not have undergone a
credential downgrade. A subject with appropriate privilege may override
these protections.
In the future, we will extend these checks to require that p1 effective
group membership must be a superset of p2 effective group membership.
Obtained from: TrustedBSD Project
other "system" header files.
Also help the deprecation of lockmgr.h by making it a sub-include of
sys/lock.h and removing sys/lockmgr.h form kernel .c files.
Sort sys/*.h includes where possible in affected files.
OK'ed by: bde (with reservations)
modify the scheduling properties of processes with a different real
uid but the same effective uid (i.e., daemons, et al). (note: these
cases were previously commented out, so this does not change the
compiled code at al)
Obtained from: TrustedBSD Project
semantics don't: in practice, both policy and semantics permit
loop-back debugging operations, only it's just a subset of debugging
operations (i.e., a proc can open its own /dev/mem), and that's at a
higher layer.
and non-P_SUGID cases, simplify p_cansignal() logic so that the
P_SUGID masking of possible signals is independent from uid checks,
removing redundant code and generally improving readability.
Reviewed by: tmm
Obtained from: TrustedBSD Project
the ability of unprivileged processes to deliver arbitrary signals
to daemons temporarily taking on unprivileged effective credentials
when P_SUGID is not set on the target process:
Removed:
(p1->p_cred->cr_ruid != ps->p_cred->cr_uid)
(p1->p_ucred->cr_uid != ps->p_cred->cr_uid)
o Replace two "allow this" exceptions in p_cansignal() restricting
the ability of unprivileged processes to deliver arbitrary signals
to daemons temporarily taking on unprivileged effective credentials
when P_SUGID is set on the target process:
Replaced:
(p1->p_cred->p_ruid != p2->p_ucred->cr_uid)
(p1->p_cred->cr_uid != p2->p_ucred->cr_uid)
With:
(p1->p_cred->p_ruid != p2->p_ucred->p_svuid)
(p1->p_ucred->cr_uid != p2->p_ucred->p_svuid)
o These changes have the effect of making the uid-based handling of
both P_SUGID and non-P_SUGID signal delivery consistent, following
these four general cases:
p1's ruid equals p2's ruid
p1's euid equals p2's ruid
p1's ruid equals p2's svuid
p1's euid equals p2's svuid
The P_SUGID and non-P_SUGID cases can now be largely collapsed,
and I'll commit this in a few days if no immediate problems are
encountered with this set of changes.
o These changes remove a number of warning cases identified by the
proc_to_proc inter-process authorization regression test.
o As these are new restrictions, we'll have to watch out carefully for
possible side effects on running code: they seem reasonable to me,
but it's possible this change might have to be backed out if problems
are experienced.
Submitted by: src/tools/regression/security/proc_to_proc/testuid
Reviewed by: tmm
Obtained from: TrustedBSD Project
ability of unprivileged processes to modify the scheduling properties
of daemons temporarily taking on unprivileged effective credentials.
These cases (p1->p_cred->p_ruid == p2->p_ucred->cr_uid) and
(p1->p_ucred->cr_uid == p2->p_ucred->cr_uid), respectively permitting
a subject process to influence the scheduling of a daemon if the subject
process has the same real uid or effective uid as the daemon's effective
uid. This removes a number of the warning cases identified by the
proc_to_proc iner-process authorization regression test.
o As these are new restrictions, we'll have to watch out carefully for
possible side effects on running code: they seem reasonable to me,
but it's possible this change might have to be backed out if problems
are experienced.
Reported by: src/tools/regression/security/proc_to_proc/testuid
Obtained from: TrustedBSD Project
p_can(...P_CAN_SEE...) to getpgid(), getsid(), and setpgid(),
blocking these operations on processes that should not be visible
by the requesting process. Required to reduce information leakage
in MAC environments.
Obtained from: TrustedBSD Project
from signal authorization checking.
o p_cansignal() takes three arguments: subject process, object process,
and signal number, unlike p_cankill(), which only took into account
the processes and not the signal number, improving the abstraction
such that CANSIGNAL() from kern_sig.c can now also be eliminated;
previously CANSIGNAL() special-cased the handling of SIGCONT based
on process session. privused is now deprecated.
o The new p_cansignal() further limits the set of signals that may
be delivered to processes with P_SUGID set, and restructures the
access control check to allow it to be extended more easily.
o These changes take into account work done by the OpenBSD Project,
as well as by Robert Watson and Thomas Moestl on the TrustedBSD
Project.
Obtained from: TrustedBSD Project
toggle the P_SUGID bit explicitly, rather than relying on it being
set implicitly by other protection and credential logic. This feature
is introduced to support inter-process authorization regression testing
by simplifying userland credential management allowing the easy
isolation and reproduction of authorization events with specific
security contexts. This feature is enabled only by "options REGRESSION"
and is not intended to be used by applications. While the feature is
not known to introduce security vulnerabilities, it does allow
processes to enter previously inaccessible parts of the credential
state machine, and is therefore disabled by default. It may not
constitute a risk, and therefore in the future pending further analysis
(and appropriate need) may become a published interface.
Obtained from: TrustedBSD Project
ps_showallprocs such that if superuser is present to override process
hiding, the search falls through [to success]. When additional
restrictions are placed on process visibility, such as MAC, new clauses
will be placed above the return(0).
Obtained from: TrustedBSD Project
two subject ucreds. Unlike p_cansee(), u_cansee() doesn't have
process lock requirements, only valid ucred reference requirements,
so is prefered as process locking improves. For now, back p_cansee()
into u_cansee(), but eventually p_cansee() will go away.
Reviewed by: jhb, tmm
Obtained from: TrustedBSD Project
credential structure, ucred (cr->cr_prison).
o Allow jail inheritence to be a function of credential inheritence.
o Abstract prison structure reference counting behind pr_hold() and
pr_free(), invoked by the similarly named credential reference
management functions, removing this code from per-ABI fork/exit code.
o Modify various jail() functions to use struct ucred arguments instead
of struct proc arguments.
o Introduce jailed() function to determine if a credential is jailed,
rather than directly checking pointers all over the place.
o Convert PRISON_CHECK() macro to prison_check() function.
o Move jail() function prototypes to jail.h.
o Emulate the P_JAILED flag in fill_kinfo_proc() and no longer set the
flag in the process flags field itself.
o Eliminate that "const" qualifier from suser/p_can/etc to reflect
mutex use.
Notes:
o Some further cleanup of the linux/jail code is still required.
o It's now possible to consider resolving some of the process vs
credential based permission checking confusion in the socket code.
o Mutex protection of struct prison is still not present, and is
required to protect the reference count plus some fields in the
structure.
Reviewed by: freebsd-arch
Obtained from: TrustedBSD Project
mtx_enter(lock, type) becomes:
mtx_lock(lock) for sleep locks (MTX_DEF-initialized locks)
mtx_lock_spin(lock) for spin locks (MTX_SPIN-initialized)
similarily, for releasing a lock, we now have:
mtx_unlock(lock) for MTX_DEF and mtx_unlock_spin(lock) for MTX_SPIN.
We change the caller interface for the two different types of locks
because the semantics are entirely different for each case, and this
makes it explicitly clear and, at the same time, it rids us of the
extra `type' argument.
The enter->lock and exit->unlock change has been made with the idea
that we're "locking data" and not "entering locked code" in mind.
Further, remove all additional "flags" previously passed to the
lock acquire/release routines with the exception of two:
MTX_QUIET and MTX_NOSWITCH
The functionality of these flags is preserved and they can be passed
to the lock/unlock routines by calling the corresponding wrappers:
mtx_{lock, unlock}_flags(lock, flag(s)) and
mtx_{lock, unlock}_spin_flags(lock, flag(s)) for MTX_DEF and MTX_SPIN
locks, respectively.
Re-inline some lock acq/rel code; in the sleep lock case, we only
inline the _obtain_lock()s in order to ensure that the inlined code
fits into a cache line. In the spin lock case, we inline recursion and
actually only perform a function call if we need to spin. This change
has been made with the idea that we generally tend to avoid spin locks
and that also the spin locks that we do have and are heavily used
(i.e. sched_lock) do recurse, and therefore in an effort to reduce
function call overhead for some architectures (such as alpha), we
inline recursion for this case.
Create a new malloc type for the witness code and retire from using
the M_DEV type. The new type is called M_WITNESS and is only declared
if WITNESS is enabled.
Begin cleaning up some machdep/mutex.h code - specifically updated the
"optimized" inlined code in alpha/mutex.h and wrote MTX_LOCK_SPIN
and MTX_UNLOCK_SPIN asm macros for the i386/mutex.h as we presently
need those.
Finally, caught up to the interface changes in all sys code.
Contributors: jake, jhb, jasone (in no particular order)
1) mpsafe (protect the refcount with a mutex).
2) reduce duplicated code by removing the inlined crdup() from crcopy()
and make crcopy() call crdup().
3) use M_ZERO flag when allocating initial structs instead of calling bzero
after allocation.
4) expand the size of the refcount from a u_short to an u_int, by using
shorts we might have an overflow.
Glanced at by: jake
could debug processes after the commit that introduced the typo.
Security is good, but security is not always the same as turning things
off :-).
PR: kern/22711
Obtained from: brooks@one-eyed-alien.net
in the p_candebug() function. Synchronize with sef's CHECKIO()
macro from the old procfs, which seems to be a good source of security
checks.
Obtained from: TrustedBSD Project
chgsbsize(), which are called rather frequently and may be called from an
interrupt context in the case of chgsbsize(). Instead, do the hash table
lookup and maintenance when credentials are changed, which is a lot less
frequent. Add pointers to the uidinfo structures to the ucred and pcred
structures for fast access. Pass a pointer to the credential to chgproccnt()
and chgsbsize() instead of passing the uid. Add a reference count to the
uidinfo structure and use it to decide when to free the structure rather
than freeing the structure when the resource consumption drops to zero.
Move the resource tracking code from kern_proc.c to kern_resource.c. Move
some duplicate code sequences in kern_prot.c to separate helper functions.
Change KASSERTs in this code to unconditional tests and calls to panic().
kern.ps_showallprocs. Apparently got lost in the merge process from
the capability patches. Now fixed.
Submitted by: jdp
Obtained from: TrustedBSD Project
int p_can(p1, p2, operation, privused)
which allows specification of subject process, object process,
inter-process operation, and an optional call-by-reference privused
flag, allowing the caller to determine if privilege was required
for the call to succeed. This allows jail, kern.ps_showallprocs and
regular credential-based interaction checks to occur in one block of
code. Possible operations are P_CAN_SEE, P_CAN_SCHED, P_CAN_KILL,
and P_CAN_DEBUG. p_can currently breaks out as a wrapper to a
series of static function checks in kern_prot, which should not
be invoked directly.
o Commented out capabilities entries are included for some checks.
o Update most inter-process authorization to make use of p_can() instead
of manual checks, PRISON_CHECK(), P_TRESPASS(), and
kern.ps_showallprocs.
o Modify suser{,_xxx} to use const arguments, as it no longer modifies
process flags due to the disabling of ASU.
o Modify some checks/errors in procfs so that ENOENT is returned instead
of ESRCH, further improving concealment of processes that should not
be visible to other processes. Also introduce new access checks to
improve hiding of processes for procfs_lookup(), procfs_getattr(),
procfs_readdir(). Correct a bug reported by bp concerning not
handling the CREATE case in procfs_lookup(). Remove volatile flag in
procfs that caused apparently spurious qualifier warnigns (approved by
bde).
o Add comment noting that ktrace() has not been updated, as its access
control checks are different from ptrace(), whereas they should
probably be the same. Further discussion should happen on this topic.
Reviewed by: bde, green, phk, freebsd-security, others
Approved by: bde
Obtained from: TrustedBSD Project
time being, the ASU accounting flag will no longer be available, but
may be reinstituted in the future once authorization have been redone.
As it is, the kernel went through contortions in access control to
avoid calling suser, which always set the flag. This will also allow
suser to accept const struct *{cred, proc} arguments.
Reviewed by: bde, green, phk, freebsd-security, others
Approved by: bde
Obtained from: TrustedBSD Project
1) while allocating a uidinfo struct malloc is called with M_WAITOK,
it's possible that while asleep another process by the same user
could have woken up earlier and inserted an entry into the uid
hash table. Having redundant entries causes inconsistancies that
we can't handle.
fix: do a non-waiting malloc, and if that fails then do a blocking
malloc, after waking up check that no one else has inserted an entry
for us already.
2) Because many checks for sbsize were done as "test then set" in a non
atomic manner it was possible to exceed the limits put up via races.
fix: instead of querying the count then setting, we just attempt to
set the count and leave it up to the function to return success or
failure.
3) The uidinfo code was inlining and repeating, lookups and insertions
and deletions needed to be in their own functions for clarity.
Reviewed by: green
kern_prot, which cleans up some namespace issues
o Don't need a special handler to limit un-setting, as suser is used to
protect suser_permitted, making it one-way by definition.
Suggested by: bde
returning anything but EPERM.
o suser is enabled by default; once disabled, cannot be reenabled
o To be used in alternative security models where uid0 does not connote
additional privileges
o Should be noted that uid0 still has some additional powers as it
owns many important files and executables, so suffers from the same
fundamental security flaws as securelevels. This is fixed with
MAC integrity protection code (in progress)
o Not safe for consumption unless you are *really* sure you don't want
things like shutdown to work, et al :-)
Obtained from: TrustedBSD Project
