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linux/security/Kconfig
Linus Torvalds aefcf2f4b5 Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 
Pull kernel lockdown mode from James Morris:
 "This is the latest iteration of the kernel lockdown patchset, from
  Matthew Garrett, David Howells and others.

  From the original description:

    This patchset introduces an optional kernel lockdown feature,
    intended to strengthen the boundary between UID 0 and the kernel.
    When enabled, various pieces of kernel functionality are restricted.
    Applications that rely on low-level access to either hardware or the
    kernel may cease working as a result - therefore this should not be
    enabled without appropriate evaluation beforehand.

    The majority of mainstream distributions have been carrying variants
    of this patchset for many years now, so there's value in providing a
    doesn't meet every distribution requirement, but gets us much closer
    to not requiring external patches.

  There are two major changes since this was last proposed for mainline:

   - Separating lockdown from EFI secure boot. Background discussion is
     covered here: https://lwn.net/Articles/751061/

   -  Implementation as an LSM, with a default stackable lockdown LSM
      module. This allows the lockdown feature to be policy-driven,
      rather than encoding an implicit policy within the mechanism.

  The new locked_down LSM hook is provided to allow LSMs to make a
  policy decision around whether kernel functionality that would allow
  tampering with or examining the runtime state of the kernel should be
  permitted.

  The included lockdown LSM provides an implementation with a simple
  policy intended for general purpose use. This policy provides a coarse
  level of granularity, controllable via the kernel command line:

    lockdown={integrity|confidentiality}

  Enable the kernel lockdown feature. If set to integrity, kernel features
  that allow userland to modify the running kernel are disabled. If set to
  confidentiality, kernel features that allow userland to extract
  confidential information from the kernel are also disabled.

  This may also be controlled via /sys/kernel/security/lockdown and
  overriden by kernel configuration.

  New or existing LSMs may implement finer-grained controls of the
  lockdown features. Refer to the lockdown_reason documentation in
  include/linux/security.h for details.

  The lockdown feature has had signficant design feedback and review
  across many subsystems. This code has been in linux-next for some
  weeks, with a few fixes applied along the way.

  Stephen Rothwell noted that commit 9d1f8be5cf ("bpf: Restrict bpf
  when kernel lockdown is in confidentiality mode") is missing a
  Signed-off-by from its author. Matthew responded that he is providing
  this under category (c) of the DCO"

* 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (31 commits)
  kexec: Fix file verification on S390
  security: constify some arrays in lockdown LSM
  lockdown: Print current->comm in restriction messages
  efi: Restrict efivar_ssdt_load when the kernel is locked down
  tracefs: Restrict tracefs when the kernel is locked down
  debugfs: Restrict debugfs when the kernel is locked down
  kexec: Allow kexec_file() with appropriate IMA policy when locked down
  lockdown: Lock down perf when in confidentiality mode
  bpf: Restrict bpf when kernel lockdown is in confidentiality mode
  lockdown: Lock down tracing and perf kprobes when in confidentiality mode
  lockdown: Lock down /proc/kcore
  x86/mmiotrace: Lock down the testmmiotrace module
  lockdown: Lock down module params that specify hardware parameters (eg. ioport)
  lockdown: Lock down TIOCSSERIAL
  lockdown: Prohibit PCMCIA CIS storage when the kernel is locked down
  acpi: Disable ACPI table override if the kernel is locked down
  acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down
  ACPI: Limit access to custom_method when the kernel is locked down
  x86/msr: Restrict MSR access when the kernel is locked down
  x86: Lock down IO port access when the kernel is locked down
  ...
2019-09-28 08:14:15 -07:00

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# SPDX-License-Identifier: GPL-2.0-only
#
# Security configuration
#
menu "Security options"
source "security/keys/Kconfig"
config SECURITY_DMESG_RESTRICT
bool "Restrict unprivileged access to the kernel syslog"
default n
help
This enforces restrictions on unprivileged users reading the kernel
syslog via dmesg(8).
If this option is not selected, no restrictions will be enforced
unless the dmesg_restrict sysctl is explicitly set to (1).
If you are unsure how to answer this question, answer N.
config SECURITY
bool "Enable different security models"
depends on SYSFS
depends on MULTIUSER
help
This allows you to choose different security modules to be
configured into your kernel.
If this option is not selected, the default Linux security
model will be used.
If you are unsure how to answer this question, answer N.
config SECURITY_WRITABLE_HOOKS
depends on SECURITY
bool
default n
config SECURITYFS
bool "Enable the securityfs filesystem"
help
This will build the securityfs filesystem. It is currently used by
various security modules (AppArmor, IMA, SafeSetID, TOMOYO, TPM).
If you are unsure how to answer this question, answer N.
config SECURITY_NETWORK
bool "Socket and Networking Security Hooks"
depends on SECURITY
help
This enables the socket and networking security hooks.
If enabled, a security module can use these hooks to
implement socket and networking access controls.
If you are unsure how to answer this question, answer N.
config PAGE_TABLE_ISOLATION
bool "Remove the kernel mapping in user mode"
default y
depends on (X86_64 || X86_PAE) && !UML
help
This feature reduces the number of hardware side channels by
ensuring that the majority of kernel addresses are not mapped
into userspace.
See Documentation/x86/pti.rst for more details.
config SECURITY_INFINIBAND
bool "Infiniband Security Hooks"
depends on SECURITY && INFINIBAND
help
This enables the Infiniband security hooks.
If enabled, a security module can use these hooks to
implement Infiniband access controls.
If you are unsure how to answer this question, answer N.
config SECURITY_NETWORK_XFRM
bool "XFRM (IPSec) Networking Security Hooks"
depends on XFRM && SECURITY_NETWORK
help
This enables the XFRM (IPSec) networking security hooks.
If enabled, a security module can use these hooks to
implement per-packet access controls based on labels
derived from IPSec policy. Non-IPSec communications are
designated as unlabelled, and only sockets authorized
to communicate unlabelled data can send without using
IPSec.
If you are unsure how to answer this question, answer N.
config SECURITY_PATH
bool "Security hooks for pathname based access control"
depends on SECURITY
help
This enables the security hooks for pathname based access control.
If enabled, a security module can use these hooks to
implement pathname based access controls.
If you are unsure how to answer this question, answer N.
config INTEL_TXT
bool "Enable Intel(R) Trusted Execution Technology (Intel(R) TXT)"
depends on HAVE_INTEL_TXT
help
This option enables support for booting the kernel with the
Trusted Boot (tboot) module. This will utilize
Intel(R) Trusted Execution Technology to perform a measured launch
of the kernel. If the system does not support Intel(R) TXT, this
will have no effect.
Intel TXT will provide higher assurance of system configuration and
initial state as well as data reset protection. This is used to
create a robust initial kernel measurement and verification, which
helps to ensure that kernel security mechanisms are functioning
correctly. This level of protection requires a root of trust outside
of the kernel itself.
Intel TXT also helps solve real end user concerns about having
confidence that their hardware is running the VMM or kernel that
it was configured with, especially since they may be responsible for
providing such assurances to VMs and services running on it.
See <http://www.intel.com/technology/security/> for more information
about Intel(R) TXT.
See <http://tboot.sourceforge.net> for more information about tboot.
See Documentation/x86/intel_txt.rst for a description of how to enable
Intel TXT support in a kernel boot.
If you are unsure as to whether this is required, answer N.
config LSM_MMAP_MIN_ADDR
int "Low address space for LSM to protect from user allocation"
depends on SECURITY && SECURITY_SELINUX
default 32768 if ARM || (ARM64 && COMPAT)
default 65536
help
This is the portion of low virtual memory which should be protected
from userspace allocation. Keeping a user from writing to low pages
can help reduce the impact of kernel NULL pointer bugs.
For most ia64, ppc64 and x86 users with lots of address space
a value of 65536 is reasonable and should cause no problems.
On arm and other archs it should not be higher than 32768.
Programs which use vm86 functionality or have some need to map
this low address space will need the permission specific to the
systems running LSM.
config HAVE_HARDENED_USERCOPY_ALLOCATOR
bool
help
The heap allocator implements __check_heap_object() for
validating memory ranges against heap object sizes in
support of CONFIG_HARDENED_USERCOPY.
config HARDENED_USERCOPY
bool "Harden memory copies between kernel and userspace"
depends on HAVE_HARDENED_USERCOPY_ALLOCATOR
imply STRICT_DEVMEM
help
This option checks for obviously wrong memory regions when
copying memory to/from the kernel (via copy_to_user() and
copy_from_user() functions) by rejecting memory ranges that
are larger than the specified heap object, span multiple
separately allocated pages, are not on the process stack,
or are part of the kernel text. This kills entire classes
of heap overflow exploits and similar kernel memory exposures.
config HARDENED_USERCOPY_FALLBACK
bool "Allow usercopy whitelist violations to fallback to object size"
depends on HARDENED_USERCOPY
default y
help
This is a temporary option that allows missing usercopy whitelists
to be discovered via a WARN() to the kernel log, instead of
rejecting the copy, falling back to non-whitelisted hardened
usercopy that checks the slab allocation size instead of the
whitelist size. This option will be removed once it seems like
all missing usercopy whitelists have been identified and fixed.
Booting with "slab_common.usercopy_fallback=Y/N" can change
this setting.
config HARDENED_USERCOPY_PAGESPAN
bool "Refuse to copy allocations that span multiple pages"
depends on HARDENED_USERCOPY
depends on EXPERT
help
When a multi-page allocation is done without __GFP_COMP,
hardened usercopy will reject attempts to copy it. There are,
however, several cases of this in the kernel that have not all
been removed. This config is intended to be used only while
trying to find such users.
config FORTIFY_SOURCE
bool "Harden common str/mem functions against buffer overflows"
depends on ARCH_HAS_FORTIFY_SOURCE
help
Detect overflows of buffers in common string and memory functions
where the compiler can determine and validate the buffer sizes.
config STATIC_USERMODEHELPER
bool "Force all usermode helper calls through a single binary"
help
By default, the kernel can call many different userspace
binary programs through the "usermode helper" kernel
interface. Some of these binaries are statically defined
either in the kernel code itself, or as a kernel configuration
option. However, some of these are dynamically created at
runtime, or can be modified after the kernel has started up.
To provide an additional layer of security, route all of these
calls through a single executable that can not have its name
changed.
Note, it is up to this single binary to then call the relevant
"real" usermode helper binary, based on the first argument
passed to it. If desired, this program can filter and pick
and choose what real programs are called.
If you wish for all usermode helper programs are to be
disabled, choose this option and then set
STATIC_USERMODEHELPER_PATH to an empty string.
config STATIC_USERMODEHELPER_PATH
string "Path to the static usermode helper binary"
depends on STATIC_USERMODEHELPER
default "/sbin/usermode-helper"
help
The binary called by the kernel when any usermode helper
program is wish to be run. The "real" application's name will
be in the first argument passed to this program on the command
line.
If you wish for all usermode helper programs to be disabled,
specify an empty string here (i.e. "").
source "security/selinux/Kconfig"
source "security/smack/Kconfig"
source "security/tomoyo/Kconfig"
source "security/apparmor/Kconfig"
source "security/loadpin/Kconfig"
source "security/yama/Kconfig"
source "security/safesetid/Kconfig"
source "security/lockdown/Kconfig"
source "security/integrity/Kconfig"
choice
prompt "First legacy 'major LSM' to be initialized"
default DEFAULT_SECURITY_SELINUX if SECURITY_SELINUX
default DEFAULT_SECURITY_SMACK if SECURITY_SMACK
default DEFAULT_SECURITY_TOMOYO if SECURITY_TOMOYO
default DEFAULT_SECURITY_APPARMOR if SECURITY_APPARMOR
default DEFAULT_SECURITY_DAC
help
This choice is there only for converting CONFIG_DEFAULT_SECURITY
in old kernel configs to CONFIG_LSM in new kernel configs. Don't
change this choice unless you are creating a fresh kernel config,
for this choice will be ignored after CONFIG_LSM has been set.
Selects the legacy "major security module" that will be
initialized first. Overridden by non-default CONFIG_LSM.
config DEFAULT_SECURITY_SELINUX
bool "SELinux" if SECURITY_SELINUX=y
config DEFAULT_SECURITY_SMACK
bool "Simplified Mandatory Access Control" if SECURITY_SMACK=y
config DEFAULT_SECURITY_TOMOYO
bool "TOMOYO" if SECURITY_TOMOYO=y
config DEFAULT_SECURITY_APPARMOR
bool "AppArmor" if SECURITY_APPARMOR=y
config DEFAULT_SECURITY_DAC
bool "Unix Discretionary Access Controls"
endchoice
config LSM
string "Ordered list of enabled LSMs"
default "lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor" if DEFAULT_SECURITY_SMACK
default "lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo" if DEFAULT_SECURITY_APPARMOR
default "lockdown,yama,loadpin,safesetid,integrity,tomoyo" if DEFAULT_SECURITY_TOMOYO
default "lockdown,yama,loadpin,safesetid,integrity" if DEFAULT_SECURITY_DAC
default "lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor"
help
A comma-separated list of LSMs, in initialization order.
Any LSMs left off this list will be ignored. This can be
controlled at boot with the "lsm=" parameter.
If unsure, leave this as the default.
source "security/Kconfig.hardening"
endmenu
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