After working with the larger SELinux-based distros for several
years, we're finally at a place where we can disable the SELinux
runtime disable functionality. The existing kernel deprecation
notice explains the functionality and why we want to remove it:
The selinuxfs "disable" node allows SELinux to be disabled at
runtime prior to a policy being loaded into the kernel. If
disabled via this mechanism, SELinux will remain disabled until
the system is rebooted.
The preferred method of disabling SELinux is via the "selinux=0"
boot parameter, but the selinuxfs "disable" node was created to
make it easier for systems with primitive bootloaders that did not
allow for easy modification of the kernel command line.
Unfortunately, allowing for SELinux to be disabled at runtime makes
it difficult to secure the kernel's LSM hooks using the
"__ro_after_init" feature.
It is that last sentence, mentioning the '__ro_after_init' hardening,
which is the real motivation for this change, and if you look at the
diffstat you'll see that the impact of this patch reaches across all
the different LSMs, helping prevent tampering at the LSM hook level.
From a SELinux perspective, it is important to note that if you
continue to disable SELinux via "/etc/selinux/config" it may appear
that SELinux is disabled, but it is simply in an uninitialized state.
If you load a policy with `load_policy -i`, you will see SELinux
come alive just as if you had loaded the policy during early-boot.
It is also worth noting that the "/sys/fs/selinux/disable" file is
always writable now, regardless of the Kconfig settings, but writing
to the file has no effect on the system, other than to display an
error on the console if a non-zero/true value is written.
Finally, in the several years where we have been working on
deprecating this functionality, there has only been one instance of
someone mentioning any user visible breakage. In this particular
case it was an individual's kernel test system, and the workaround
documented in the deprecation notice ("selinux=0" on the kernel
command line) resolved the issue without problem.
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
We originally promised that the SELinux 'checkreqprot' functionality
would be removed no sooner than June 2021, and now that it is March
2023 it seems like it is a good time to do the final removal. The
deprecation notice in the kernel provides plenty of detail on why
'checkreqprot' is not desirable, with the key point repeated below:
This was a compatibility mechanism for legacy userspace and
for the READ_IMPLIES_EXEC personality flag. However, if set to
1, it weakens security by allowing mappings to be made executable
without authorization by policy. The default value of checkreqprot
at boot was changed starting in Linux v4.4 to 0 (i.e. check the
actual protection), and Android and Linux distributions have been
explicitly writing a "0" to /sys/fs/selinux/checkreqprot during
initialization for some time.
Along with the official deprecation notice, we have been discussing
this on-list and directly with several of the larger SELinux-based
distros and everyone is happy to see this feature finally removed.
In an attempt to catch all of the smaller, and DIY, Linux systems
we have been writing a deprecation notice URL into the kernel log,
along with a growing ssleep() penalty, when admins enabled
checkreqprot at runtime or via the kernel command line. We have
yet to have anyone come to us and raise an objection to the
deprecation or planned removal.
It is worth noting that while this patch removes the checkreqprot
functionality, it leaves the user visible interfaces (kernel command
line and selinuxfs file) intact, just inert. This should help
prevent breakages with existing userspace tools that correctly, but
unnecessarily, disable checkreqprot at boot or runtime. Admins
that attempt to enable checkreqprot will be met with a removal
message in the kernel log.
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Deprecate setting the SELinux checkreqprot tunable to 1 via kernel
parameter or /sys/fs/selinux/checkreqprot. Setting it to 0 is left
intact for compatibility since Android and some Linux distributions
do so for security and treat an inability to set it as a fatal error.
Eventually setting it to 0 will become a no-op and the kernel will
stop using checkreqprot's value internally altogether.
checkreqprot was originally introduced as a compatibility mechanism
for legacy userspace and the READ_IMPLIES_EXEC personality flag.
However, if set to 1, it weakens security by allowing mappings to be
made executable without authorization by policy. The default value
for the SECURITY_SELINUX_CHECKREQPROT_VALUE config option was changed
from 1 to 0 in commit 2a35d196c1 ("selinux: change
CONFIG_SECURITY_SELINUX_CHECKREQPROT_VALUE default") and both Android
and Linux distributions began explicitly setting
/sys/fs/selinux/checkreqprot to 0 some time ago.
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
selinuxfs was originally mounted on /selinux, and various docs and
kconfig help texts referred to nodes under it. In Linux 3.0,
/sys/fs/selinux was introduced as the preferred mount point for selinuxfs.
Fix all the old references to /selinux/ to /sys/fs/selinux/.
While we are there, update the description of the selinux boot parameter
to reflect the fact that the default value is always 1 since
commit be6ec88f41 ("selinux: Remove SECURITY_SELINUX_BOOTPARAM_VALUE")
and drop discussion of runtime disable since it is deprecated.
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Deprecate the CONFIG_SECURITY_SELINUX_DISABLE functionality. The
code was originally developed to make it easier for Linux
distributions to support architectures where adding parameters to the
kernel command line was difficult. Unfortunately, supporting runtime
disable meant we had to make some security trade-offs when it came to
the LSM hooks, as documented in the Kconfig help text:
NOTE: selecting this option will disable the '__ro_after_init'
kernel hardening feature for security hooks. Please consider
using the selinux=0 boot parameter instead of enabling this
option.
Fortunately it looks as if that the original motivation for the
runtime disable functionality is gone, and Fedora/RHEL appears to be
the only major distribution enabling this capability at build time
so we are now taking steps to remove it entirely from the kernel.
The first step is to mark the functionality as deprecated and print
an error when it is used (what this patch is doing). As Fedora/RHEL
makes progress in transitioning the distribution away from runtime
disable, we will introduce follow-up patches over several kernel
releases which will block for increasing periods of time when the
runtime disable is used. Finally we will remove the option entirely
once we believe all users have moved to the kernel cmdline approach.
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Translating a context struct to string can be quite slow, especially if
the context has a lot of category bits set. This can cause quite
noticeable performance impact in situations where the translation needs
to be done repeatedly. A common example is a UNIX datagram socket with
the SO_PASSSEC option enabled, which is used e.g. by systemd-journald
when receiving log messages via datagram socket. This scenario can be
reproduced with:
cat /dev/urandom | base64 | logger &
timeout 30s perf record -p $(pidof systemd-journald) -a -g
kill %1
perf report -g none --pretty raw | grep security_secid_to_secctx
Before the caching introduced by this patch, computing the context
string (security_secid_to_secctx() function) takes up ~65% of
systemd-journald's CPU time (assuming a context with 1024 categories
set and Fedora x86_64 release kernel configs). After this patch
(assuming near-perfect cache hit ratio) this overhead is reduced to just
~2%.
This patch addresses the issue by caching a certain number (compile-time
configurable) of recently used context strings to speed up repeated
translations of the same context, while using only a small amount of
memory.
The cache is integrated into the existing sidtab table by adding a field
to each entry, which when not NULL contains an RCU-protected pointer to
a cache entry containing the cached string. The cache entries are kept
in a linked list sorted according to how recently they were used. On a
cache miss when the cache is full, the least recently used entry is
removed to make space for the new entry.
The patch migrates security_sid_to_context_core() to use the cache (also
a few other functions where it was possible without too much fuss, but
these mostly use the translation for logging in case of error, which is
rare).
Link: https://bugzilla.redhat.com/show_bug.cgi?id=1733259
Cc: Michal Sekletar <msekleta@redhat.com>
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>
Tested-by: Stephen Smalley <sds@tycho.nsa.gov>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
[PM: lots of merge fixups due to collisions with other sidtab patches]
Signed-off-by: Paul Moore <paul@paul-moore.com>
This replaces the reverse table lookup and reverse cache with a
hashtable which improves cache-miss reverse-lookup times from
O(n) to O(1)* and maintains the same performance as a reverse
cache hit.
This reduces the time needed to add a new sidtab entry from ~500us
to 5us on a Pixel 3 when there are ~10,000 sidtab entries.
The implementation uses the kernel's generic hashtable API,
It uses the context's string represtation as the hash source,
and the kernels generic string hashing algorithm full_name_hash()
to reduce the string to a 32 bit value.
This change also maintains the improvement introduced in
commit ee1a84fdfe ("selinux: overhaul sidtab to fix bug and improve
performance") which removed the need to keep the current sidtab
locked during policy reload. It does however introduce periodic
locking of the target sidtab while converting the hashtable. Sidtab
entries are never modified or removed, so the context struct stored
in the sid_to_context tree can also be used for the context_to_sid
hashtable to reduce memory usage.
This bug was reported by:
- On the selinux bug tracker.
BUG: kernel softlockup due to too many SIDs/contexts #37https://github.com/SELinuxProject/selinux-kernel/issues/37
- Jovana Knezevic on Android's bugtracker.
Bug: 140252993
"During multi-user performance testing, we create and remove users
many times. selinux_android_restorecon_pkgdir goes from 1ms to over
20ms after about 200 user creations and removals. Accumulated over
~280 packages, that adds a significant time to user creation,
making perf benchmarks unreliable."
* Hashtable lookup is only O(1) when n < the number of buckets.
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Reported-by: Stephen Smalley <sds@tycho.nsa.gov>
Reported-by: Jovana Knezevic <jovanak@google.com>
Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>
Tested-by: Stephen Smalley <sds@tycho.nsa.gov>
[PM: subj tweak, removed changelog from patch description]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Add SPDX license identifiers to all Make/Kconfig files which:
- Have no license information of any form
These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:
GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
In preparation for removing CONFIG_DEFAULT_SECURITY, this removes the
soon-to-be redundant SECURITY_SELINUX_BOOTPARAM_VALUE. Since explicit
ordering via CONFIG_LSM or "lsm=" will define whether an LSM is enabled or
not, this CONFIG will become effectively ignored, so remove it. However,
in order to stay backward-compatible with "security=selinux", the enable
variable defaults to true.
Signed-off-by: Kees Cook <keescook@chromium.org>
Subsequent patches will add RO hardening to LSM hooks, however, SELinux
still needs to be able to perform runtime disablement after init to handle
architectures where init-time disablement via boot parameters is not feasible.
Introduce a new kernel configuration parameter CONFIG_SECURITY_WRITABLE_HOOKS,
and a helper macro __lsm_ro_after_init, to handle this case.
Signed-off-by: James Morris <james.l.morris@oracle.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Kees Cook <keescook@chromium.org>
Remove the SECURITY_SELINUX_POLICYDB_VERSION_MAX Kconfig option
Per: https://github.com/SELinuxProject/selinux/wiki/Kernel-Todo
This was only needed on Fedora 3 and 4 and just causes issues now,
so drop it.
The MAX and MIN should just be whatever the kernel can support.
Signed-off-by: William Roberts <william.c.roberts@intel.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Change the SELinux checkreqprot default value to 0 so that SELinux
performs access control checking on the actual memory protections
used by the kernel and not those requested by the application.
Signed-off-by: Paul Moore <pmoore@redhat.com>
This patch is the first step towards removing the old "compat_net" code from
the kernel. Secmark, the "compat_net" replacement was first introduced in
2.6.18 (September 2006) and the major Linux distributions with SELinux support
have transitioned to Secmark so it is time to start deprecating the "compat_net"
mechanism. Testing a patched version of 2.6.28-rc6 with the initial release of
Fedora Core 5 did not show any problems when running in enforcing mode.
This patch adds an entry to the feature-removal-schedule.txt file and removes
the SECURITY_SELINUX_ENABLE_SECMARK_DEFAULT configuration option, forcing
Secmark on by default although it can still be disabled at runtime. The patch
also makes the Secmark permission checks "dynamic" in the sense that they are
only executed when Secmark is configured; this should help prevent problems
with older distributions that have not yet migrated to Secmark.
Signed-off-by: Paul Moore <paul.moore@hp.com>
Acked-by: James Morris <jmorris@namei.org>
Update the SELinux entry in MAINTAINERS and drop the obsolete information
from the selinux Kconfig help text.
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Introduce the concept of a permissive type. A new ebitmap is introduced to
the policy database which indicates if a given type has the permissive bit
set or not. This bit is tested for the scontext of any denial. The bit is
meaningless on types which only appear as the target of a decision and never
the source. A domain running with a permissive type will be allowed to
perform any action similarly to when the system is globally set permissive.
Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Add a new policy capabilities bitmap to SELinux policy version 22. This bitmap
will enable the security server to query the policy to determine which features
it supports.
Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>
Introduces support for policy version 21. This version of the binary
kernel policy allows for defining range transitions on security classes
other than the process security class. As always, backwards compatibility
for older formats is retained. The security class is read in as specified
when using the new format, while the "process" security class is assumed
when using an older policy format.
Signed-off-by: Darrel Goeddel <dgoeddel@trustedcs.com>
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Enable configuration of SELinux maximum supported policy version to support
legacy userland (init) that does not gracefully handle kernels that support
newer policy versions two or more beyond the installed policy, as in FC3
and FC4.
[bunk@stusta.de: improve Kconfig help text]
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add new per-packet access controls to SELinux, replacing the old
packet controls.
Packets are labeled with the iptables SECMARK and CONNSECMARK targets,
then security policy for the packets is enforced with these controls.
To allow for a smooth transition to the new controls, the old code is
still present, but not active by default. To restore previous
behavior, the old controls may be activated at runtime by writing a
'1' to /selinux/compat_net, and also via the kernel boot parameter
selinux_compat_net. Switching between the network control models
requires the security load_policy permission. The old controls will
probably eventually be removed and any continued use is discouraged.
With this patch, the new secmark controls for SElinux are disabled by
default, so existing behavior is entirely preserved, and the user is
not affected at all.
It also provides a config option to enable the secmark controls by
default (which can always be overridden at boot and runtime). It is
also noted in the kconfig help that the user will need updated
userspace if enabling secmark controls for SELinux and that they'll
probably need the SECMARK and CONNMARK targets, and conntrack protocol
helpers, although such decisions are beyond the scope of kernel
configuration.
Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Make SELinux depend on AUDIT as it requires the basic audit support to log
permission denials at all. Note that AUDITSYSCALL remains optional for
SELinux, although it can be useful in providing further information upon
denials.
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Make SELinux depend on SECURITY_NETWORK (which depends on SECURITY), as it
requires the socket hooks for proper operation even in the local case.
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
