f5509cc18d
This is the start of porting PAX_USERCOPY into the mainline kernel. This
is the first set of features, controlled by CONFIG_HARDENED_USERCOPY. The
work is based on code by PaX Team and Brad Spengler, and an earlier port
from Casey Schaufler. Additional non-slab page tests are from Rik van Riel.
This patch contains the logic for validating several conditions when
performing copy_to_user() and copy_from_user() on the kernel object
being copied to/from:
- address range doesn't wrap around
- address range isn't NULL or zero-allocated (with a non-zero copy size)
- if on the slab allocator:
- object size must be less than or equal to copy size (when check is
implemented in the allocator, which appear in subsequent patches)
- otherwise, object must not span page allocations (excepting Reserved
and CMA ranges)
- if on the stack
- object must not extend before/after the current process stack
- object must be contained by a valid stack frame (when there is
arch/build support for identifying stack frames)
- object must not overlap with kernel text
Signed-off-by: Kees Cook <keescook@chromium.org>
Tested-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Tested-by: Michael Ellerman <mpe@ellerman.id.au>
6.6 KiB
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 SECURITYFS bool "Enable the securityfs filesystem" help This will build the securityfs filesystem. It is currently used by the TPM bios character driver and IMA, an integrity provider. It is not used by SELinux or SMACK.
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 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/intel_txt.txt 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 HAVE_ARCH_HARDENED_USERCOPY bool help The architecture supports CONFIG_HARDENED_USERCOPY by calling check_object_size() just before performing the userspace copies in the low level implementation of copy_to_user() and copy_from_user().
config HARDENED_USERCOPY bool "Harden memory copies between kernel and userspace" depends on HAVE_ARCH_HARDENED_USERCOPY select BUG 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 allocates 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.
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/integrity/Kconfig
choice prompt "Default security module" 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
Select the security module that will be used by default if the
kernel parameter security= is not specified.
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 DEFAULT_SECURITY string default "selinux" if DEFAULT_SECURITY_SELINUX default "smack" if DEFAULT_SECURITY_SMACK default "tomoyo" if DEFAULT_SECURITY_TOMOYO default "apparmor" if DEFAULT_SECURITY_APPARMOR default "" if DEFAULT_SECURITY_DAC
endmenu