michaelh/zephyr
1
0
Fork 0
Code Releases Activity

security: Additional option for stack canaries

Browse source 
Previously, when stack canaries were enabled, Zephyr applied this
protection to all functions. This commit introduces a new option that
allows stack canary protection to be applied selectively to specific
functions based on certain criteria.

Signed-off-by: Flavio Ceolin <flavio.ceolin@gmail.com>
This commit is contained in:
Flavio Ceolin 2024-11-25 13:58:40 -08:00 • committed by Benjamin Cabé
commit 82ace41da4
9 changed files with 47 additions and 18 deletions
Download patch file Download diff file Expand all files Collapse all files

2
CMakeLists.txt
View file

@ -175,6 +175,8 @@ endif()
# @Intent: Set compiler flags to detect general stack overflows across all functions
if(CONFIG_STACK_CANARIES)
zephyr_compile_options($<TARGET_PROPERTY:compiler,security_canaries>)
elseif(CONFIG_STACK_CANARIES_STRONG)
zephyr_compile_options($<TARGET_PROPERTY:compiler,security_canaries_strong>)
endif()
# @Intent: Obtain compiler optimizations flags and store in variables

1
cmake/compiler/arcmwdt/compiler_flags.cmake
View file

@ -168,6 +168,7 @@ set_compiler_property(PROPERTY imacros -imacros)
# Security canaries.
#no support of -mstack-protector-guard=global"
set_compiler_property(PROPERTY security_canaries -fstack-protector-all)
set_compiler_property(PROPERTY security_canaries_strong -fstack-protector-strong)
#no support of _FORTIFY_SOURCE"
set_compiler_property(PROPERTY security_fortify_compile_time)

1
cmake/compiler/compiler_flags_template.cmake
View file

@ -92,6 +92,7 @@ set_compiler_property(PROPERTY coverage)
# Security canaries flags.
set_compiler_property(PROPERTY security_canaries)
set_compiler_property(PROPERTY security_canaries_strong)
set_compiler_property(PROPERTY security_fortify_compile_time)
set_compiler_property(PROPERTY security_fortify_run_time)

3
cmake/compiler/gcc/compiler_flags.cmake
View file

@ -168,12 +168,15 @@ set_compiler_property(PROPERTY coverage -fprofile-arcs -ftest-coverage -fno-inli
# Security canaries.
set_compiler_property(PROPERTY security_canaries -fstack-protector-all)
set_compiler_property(PROPERTY security_canaries_strong -fstack-protector-strong)
# Only a valid option with GCC 7.x and above, so let's do check and set.
if(CONFIG_STACK_CANARIES_TLS)
check_set_compiler_property(APPEND PROPERTY security_canaries -mstack-protector-guard=tls)
check_set_compiler_property(APPEND PROPERTY security_canaries_strong -mstack-protector-guard=tls)
else()
check_set_compiler_property(APPEND PROPERTY security_canaries -mstack-protector-guard=global)
check_set_compiler_property(APPEND PROPERTY security_canaries_global -mstack-protector-guard=global)
endif()

2
kernel/CMakeLists.txt
View file

@ -140,7 +140,7 @@ set_target_properties(
__ZEPHYR_SUPERVISOR__
)
target_sources_ifdef(CONFIG_STACK_CANARIES kernel PRIVATE compiler_stack_protect.c)
target_sources_ifdef(CONFIG_REQUIRES_STACK_CANARIES kernel PRIVATE compiler_stack_protect.c)
target_sources_ifdef(CONFIG_SYS_CLOCK_EXISTS kernel PRIVATE timeout.c timer.c)
target_sources_ifdef(CONFIG_ATOMIC_OPERATIONS_C kernel PRIVATE atomic_c.c)
target_sources_ifdef(CONFIG_MMU kernel PRIVATE mmu.c)

38
kernel/Kconfig
View file

@ -869,25 +869,47 @@ config XIP
menu "Security Options"
config STACK_CANARIES
bool "Compiler stack canaries"
depends on ENTROPY_GENERATOR || TEST_RANDOM_GENERATOR
select NEED_LIBC_MEM_PARTITION if !STACK_CANARIES_TLS
config REQUIRES_STACK_CANARIES
bool
help
This option enables compiler stack canaries.
Hidden option to signal that software stack protection is required.
choice
prompt "Stack canaries protection options"
optional
help
If stack canaries are supported by the compiler, it will emit
extra code that inserts a canary value into the stack frame when
a function is entered and validates this value upon exit.
Stack corruption (such as that caused by buffer overflow) results
in a fatal error condition for the running entity.
Enabling this option can result in a significant increase
in footprint and an associated decrease in performance.
Enabling this option, depending on the level chosen, can result in a
significant increase in footprint and a corresponding decrease in performance.
If stack canaries are not supported by the compiler an error
will occur at build time.
if STACK_CANARIES
config STACK_CANARIES
bool "Maximum protection available"
depends on ENTROPY_GENERATOR || TEST_RANDOM_GENERATOR
select NEED_LIBC_MEM_PARTITION if !STACK_CANARIES_TLS
select REQUIRES_STACK_CANARIES
help
This option enables compiler stack canaries for all functions.
config STACK_CANARIES_STRONG
bool "Strong protection"
depends on ENTROPY_GENERATOR || TEST_RANDOM_GENERATOR
select NEED_LIBC_MEM_PARTITION if !STACK_CANARIES_TLS
select REQUIRES_STACK_CANARIES
help
This option enables compiler stack canaries in functions that call alloca,
functions that have local array definitiion or have references to local
frame addresses.
endchoice
if REQUIRES_STACK_CANARIES
config STACK_CANARIES_TLS
bool "Stack canaries using thread local storage"

2
kernel/compiler_stack_protect.c
View file

@ -10,7 +10,7 @@
*
* This module provides functions to support compiler stack protection
* using canaries. This feature is enabled with configuration
* CONFIG_STACK_CANARIES=y.
* CONFIG_STACK_CANARIES=y or CONFIG_STACK_CANARIES_STRONG=y.
*
* When this feature is enabled, the compiler generated code refers to
* function __stack_chk_fail and global variable __stack_chk_guard.

8
kernel/init.c
View file

@ -289,13 +289,13 @@ void z_bss_zero_pinned(void)
}
#endif /* CONFIG_LINKER_USE_PINNED_SECTION */
#ifdef CONFIG_STACK_CANARIES
#ifdef CONFIG_REQUIRES_STACK_CANARIES
#ifdef CONFIG_STACK_CANARIES_TLS
extern Z_THREAD_LOCAL volatile uintptr_t __stack_chk_guard;
#else
extern volatile uintptr_t __stack_chk_guard;
#endif /* CONFIG_STACK_CANARIES_TLS */
#endif /* CONFIG_STACK_CANARIES */
#endif /* CONFIG_REQUIRES_STACK_CANARIES */
/* LCOV_EXCL_STOP */
@ -778,13 +778,13 @@ FUNC_NORETURN void z_cstart(void)
#endif
z_sys_init_run_level(INIT_LEVEL_PRE_KERNEL_2);
#ifdef CONFIG_STACK_CANARIES
#ifdef CONFIG_REQUIRES_STACK_CANARIES
uintptr_t stack_guard;
z_early_rand_get((uint8_t *)&stack_guard, sizeof(stack_guard));
__stack_chk_guard = stack_guard;
__stack_chk_guard <<= 8;
#endif /* CONFIG_STACK_CANARIES */
#endif /* CONFIG_REQUIRES_STACK_CANARIES */
#ifdef CONFIG_TIMING_FUNCTIONS_NEED_AT_BOOT
timing_init();

8
kernel/xip.c
View file

@ -10,13 +10,13 @@
#include <kernel_internal.h>
#include <zephyr/linker/linker-defs.h>
#ifdef CONFIG_STACK_CANARIES
#ifdef CONFIG_REQUIRES_STACK_CANARIES
#ifdef CONFIG_STACK_CANARIES_TLS
extern Z_THREAD_LOCAL volatile uintptr_t __stack_chk_guard;
#else
extern volatile uintptr_t __stack_chk_guard;
#endif /* CONFIG_STACK_CANARIES_TLS */
#endif /* CONFIG_STACK_CANARIES */
#endif /* CONFIG_REQUIRES_STACK_CANARIES */
/**
* @brief Copy the data section from ROM to RAM
@ -49,7 +49,7 @@ void z_data_copy(void)
data_copy_xip_relocation();
#endif /* CONFIG_CODE_DATA_RELOCATION */
#ifdef CONFIG_USERSPACE
#ifdef CONFIG_STACK_CANARIES
#ifdef CONFIG_REQUIRES_STACK_CANARIES
/* stack canary checking is active for all C functions.
* __stack_chk_guard is some uninitialized value living in the
* app shared memory sections. Preserve it, and don't make any
@ -70,6 +70,6 @@ void z_data_copy(void)
#else
z_early_memcpy(&_app_smem_start, &_app_smem_rom_start,
_app_smem_end - _app_smem_start);
#endif /* CONFIG_STACK_CANARIES */
#endif /* CONFIG_REQUIRES_STACK_CANARIES */
#endif /* CONFIG_USERSPACE */
}