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fix(esp_tee): Validate the stack pointer at the privilege switch boundary

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This commit is contained in:
Laukik Hase
2026-07-09 11:50:42 +05:30
parent 6a9c44fe7e
commit 773761abb8
6 changed files with 142 additions and 55 deletions
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32
components/esp_tee/subproject/main/arch/riscv/esp_tee_asm_utils.inc
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@@ -221,3 +221,35 @@
1:
#endif
.endm
/**
* VALIDATE_REE_SP
* Validate an REE-supplied sp before the TEE stores through it. The TEE region is
* at the bottom of SRAM, so a valid REE frame [sp - framesz, sp) must lie in the
* band above it and below the peripheral window: [SOC_S_DRAM_END, SOC_PERIPHERAL_LOW].
* An out-of-bound sp will lead to a fault.
*
* With chk_priv (default) the check is skipped unless the trap came from U-mode;
* pass chk_priv=0 where the U-mode origin is already guaranteed (ecall-from-U).
*
* TODO: Revisit these bounds for high-performance RISC-V SoCs (e.g. ESP32-P4,
* ESP32-S31) with different memory maps than current ESP-TEE targets.
*
* Clobbers: \tx
*/
.macro VALIDATE_REE_SP framesz, tx, chk_priv=1
.if \chk_priv
/* Skip validation unless the previous privilege (mstatus.MPP) was U-mode */
csrr \tx, mstatus
srli \tx, \tx, MSTATUS_MPP_SHIFT
andi \tx, \tx, (MSTATUS_MPP >> MSTATUS_MPP_SHIFT)
bnez \tx, 1f
.endif
li \tx, (SOC_S_DRAM_END + \framesz)
bltu sp, \tx, _tee_sp_reject /* frame would dip into the TEE (or sub-TEE) region */
li \tx, SOC_PERIPHERAL_LOW
bltu \tx, sp, _tee_sp_reject /* sp at/above the peripheral window */
.if \chk_priv
1:
.endif
.endm

72
components/esp_tee/subproject/main/arch/riscv/esp_tee_vectors_clic.S
View File

@@ -25,6 +25,8 @@
.equ ECALL_M_MODE, 0xb
.equ CSR_UINTTHRESH, 0x047
.equ CSR_MINTTHRESH, 0x347
.equ MCAUSE_EXCCODE_SHIFT, 20
.equ MSTATUS_MPP_SHIFT, 11
.global esp_tee_global_interrupt_handler
.global esp_tee_service_dispatcher
@@ -55,6 +57,10 @@ _ns_sp_min:
_ns_sp_max:
.word 0
.global _ns_int_rtn
_ns_int_rtn:
.word 0
.section .exception_vectors.text, "ax"
/* Exception handler. */
@@ -62,28 +68,23 @@ _ns_sp_max:
.global _tee_panic_handler
.type _tee_panic_handler, @function
_tee_exception_handler:
/* Backup t0, t1 on the stack before using it */
addi sp, sp, -16
sw t0, 0(sp)
sw t1, 4(sp)
/* Backup t0 before using it */
csrw mscratch, t0
/* Read mcause */
/* Check whether the exception is an M-mode/U-mode ecall */
csrr t0, mcause
li t1, VECTORS_MCAUSE_REASON_MASK
and t0, t0, t1
slli t0, t0, MCAUSE_EXCCODE_SHIFT
srli t0, t0, MCAUSE_EXCCODE_SHIFT
addi t0, t0, -ECALL_M_MODE
beqz t0, _machine_ecall /* M-mode ecall */
addi t0, t0, (ECALL_M_MODE - ECALL_U_MODE)
beqz t0, _user_ecall /* U-mode ecall */
/* Check whether the exception is an M-mode ecall */
li t1, ECALL_M_MODE
beq t0, t1, _machine_ecall
/* Validate a U-mode-origin sp before the handler stores/dumps through it */
VALIDATE_REE_SP RV_STK_FRMSZ, t0
/* Check whether the exception is an U-mode ecall */
li t1, ECALL_U_MODE
beq t0, t1, _user_ecall
/* Restore t0, t1 from the stack */
lw t0, 0(sp)
lw t1, 4(sp)
addi sp, sp, 16
/* Restore t0 */
csrr t0, mscratch
_tee_panic_handler:
/* Not an ecall, proceed to the panic handler */
@@ -147,6 +148,12 @@ _return_from_exception:
restore_general_regs RV_STK_FRMSZ
mret
/* Fault if the sp given by the REE is found to be out-of-bounds */
_tee_sp_reject:
csrr t0, mscratch
la sp, _tee_stack
j _tee_panic_handler
.size _tee_exception_handler, .-_tee_exception_handler
/* ECALL handler. */
@@ -211,14 +218,15 @@ _skip_ctx_restore:
/* U-mode ecall handler */
_user_ecall:
/* Check whether we are returning after servicing an U-mode interrupt */
lui t0, RTNVAL
csrrw t1, mscratch, zero
beq t0, t1, _rtn_from_ns_int
la t0, _ns_int_rtn
lw t0, 0(t0)
bnez t0, _rtn_from_ns_int
/* Restore t0, t1 from the stack */
lw t0, 0(sp)
lw t1, 4(sp)
addi sp, sp, 16
/* Reject an sp whose frame would be out-of-bounds */
VALIDATE_REE_SP CONTEXT_SIZE, t0, 0
/* Restore t0 */
csrr t0, mscratch
/* This point is reached when a secure service call is issued from the REE */
/* Save register context and mepc */
@@ -272,6 +280,10 @@ _2:
/* This point is reached after servicing a U-mode interrupt occurred
* while executing a secure service */
_rtn_from_ns_int:
/* Consume the U-mode-interrupt-return sentinel (checked in _user_ecall). */
la t0, _ns_int_rtn
sw zero, 0(t0)
/* Disable the U-mode interrupt delegation */
li t0, INTMTX_SIG_IDX_ASSERT_IN_SEC_REG
li t1, TEE_PASS_INUM + CLIC_EXT_INTR_NUM_OFFSET
@@ -415,8 +427,9 @@ _4:
fence
/* Set a flag to identify the next U2M switch would be after handling a U-mode interrupt */
lui t0, RTNVAL
csrw mscratch, t0
la t0, _ns_int_rtn
li t1, RTNVAL
sw t1, 0(t0)
STACK_GUARD_POST_SWITCH t3 1 _ns_sp_min _ns_sp_max
@@ -435,6 +448,11 @@ _4:
.global _tee_s_intr_handler
.type _tee_s_intr_handler, @function
_tee_s_intr_handler:
/* Check sp if trapped from U-mode */
csrw mscratch, t0
VALIDATE_REE_SP RV_STK_FRMSZ, t0
csrr t0, mscratch /* restore the preempted t0 */
/* Start by saving the general purpose registers and the PC value before
* the interrupt happened. */
save_general_regs RV_STK_FRMSZ

70
components/esp_tee/subproject/main/arch/riscv/esp_tee_vectors_plic.S
View File

@@ -23,6 +23,7 @@
.equ RTNVAL, 0xc0de
.equ ECALL_U_MODE, 0x8
.equ ECALL_M_MODE, 0xb
.equ MSTATUS_MPP_SHIFT, 11
/* NOTE: INTWDT timeout, Cache error and Stack protection interrupts
* trigger the panic handler before reset, so they don't need to be delegated. */
.equ TEE_INTR_DELEG_BASE, ((1U << TEE_SECURE_INUM) | (1U << ETS_INT_WDT_INUM) | (1U << ETS_CACHEERR_INUM))
@@ -60,6 +61,10 @@ _ns_sp_min:
_ns_sp_max:
.word 0
.global _ns_int_rtn
_ns_int_rtn:
.word 0
.section .exception_vectors.text, "ax"
/* Exception handler. */
@@ -67,28 +72,22 @@ _ns_sp_max:
.global _tee_panic_handler
.type _tee_exception_handler, @function
_tee_exception_handler:
/* Backup t0, t1 on the stack before using it */
addi sp, sp, -16
sw t0, 0(sp)
sw t1, 4(sp)
/* Backup t0 before using it */
csrw mscratch, t0
/* Read mcause */
/* Check whether the exception is an M-mode/U-mode ecall */
csrr t0, mcause
li t1, VECTORS_MCAUSE_REASON_MASK
and t0, t0, t1
andi t0, t0, VECTORS_MCAUSE_REASON_MASK
addi t0, t0, -ECALL_M_MODE
beqz t0, _machine_ecall /* M-mode ecall */
addi t0, t0, (ECALL_M_MODE - ECALL_U_MODE)
beqz t0, _user_ecall /* U-mode ecall */
/* Check whether the exception is an M-mode ecall */
li t1, ECALL_M_MODE
beq t0, t1, _machine_ecall
/* Validate a U-mode-origin sp before the handler stores/dumps through it */
VALIDATE_REE_SP RV_STK_FRMSZ, t0
/* Check whether the exception is an U-mode ecall */
li t1, ECALL_U_MODE
beq t0, t1, _user_ecall
/* Restore t0, t1 from the stack */
lw t0, 0(sp)
lw t1, 4(sp)
addi sp, sp, 16
/* Restore t0 */
csrr t0, mscratch
_tee_panic_handler:
/* Not an ecall, proceed to the panic handler */
@@ -143,6 +142,12 @@ _return_from_exception:
restore_general_regs RV_STK_FRMSZ
mret
/* Fault if the sp given by the REE is found to be out-of-bounds */
_tee_sp_reject:
csrr t0, mscratch
la sp, _tee_stack
j _tee_panic_handler
.size _tee_exception_handler, .-_tee_exception_handler
/* ECALL handler. */
@@ -203,14 +208,15 @@ _skip_ctx_restore:
/* U-mode ecall handler */
_user_ecall:
/* Check whether we are returning after servicing an U-mode interrupt */
lui t0, RTNVAL
csrrw t1, mscratch, zero
beq t0, t1, _rtn_from_ns_int
la t0, _ns_int_rtn
lw t0, 0(t0)
bnez t0, _rtn_from_ns_int
/* Restore t0, t1 from the stack */
lw t0, 0(sp)
lw t1, 4(sp)
addi sp, sp, 16
/* Reject an sp whose frame would be out-of-bounds */
VALIDATE_REE_SP CONTEXT_SIZE, t0, 0
/* Restore t0 */
csrr t0, mscratch
/* This point is reached when a secure service call is issued from the REE */
/* Save register context and mepc */
@@ -260,6 +266,10 @@ _process_ecall:
/* This point is reached after servicing a U-mode interrupt occurred
* while executing a secure service */
_rtn_from_ns_int:
/* Consume the U-mode-interrupt-return sentinel (checked in _user_ecall). */
la t0, _ns_int_rtn
sw zero, 0(t0)
/* Disable the U-mode interrupt delegation */
csrwi mideleg, 0
@@ -341,8 +351,9 @@ _tee_ns_intr_handler:
fence
/* Set a flag to identify the next U2M switch would be after handling a U-mode interrupt */
lui t0, RTNVAL
csrw mscratch, t0
la t0, _ns_int_rtn
li t1, RTNVAL
sw t1, 0(t0)
/* Enable the U-mode interrupt delegation (except for the TEE secure interrupt) */
li t0, TEE_INTR_DELEG_MASK
@@ -365,6 +376,11 @@ _tee_ns_intr_handler:
.global _tee_s_intr_handler
.type _tee_s_intr_handler, @function
_tee_s_intr_handler:
/* Check sp if trapped from U-mode */
csrw mscratch, t0
VALIDATE_REE_SP RV_STK_FRMSZ, t0
csrr t0, mscratch /* restore the preempted t0 */
/* Start by saving the general purpose registers and the PC value before
* the interrupt happened. */
save_general_regs RV_STK_FRMSZ

2
components/esp_tee/test_apps/tee_test_fw/main/CMakeLists.txt
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@@ -1,6 +1,6 @@
idf_build_get_property(idf_path IDF_PATH)
set(priv_requires bootloader_support esp_driver_gptimer esp_tee esp_timer mbedtls spi_flash)
set(priv_requires bootloader_support esp_driver_gptimer esp_system esp_tee esp_timer mbedtls spi_flash)
# Test FW related
list(APPEND priv_requires nvs_flash test_utils unity)
# TEE related

20
components/esp_tee/test_apps/tee_test_fw/main/test_esp_tee_panic.c
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@@ -29,6 +29,7 @@
#include "unity.h"
#include "esp_tee.h"
#include "esp_private/hw_stack_guard.h"
#include "secure_service_num.h"
#define ALIGN_DOWN_TO_MMU_PAGE_SIZE(addr) ((addr) & ~((SOC_MMU_PAGE_SIZE) - 1))
@@ -229,6 +230,25 @@ TEST_CASE("Test REE-TEE isolation: DROM-W1", "[exception]")
TEST_FAIL_MESSAGE("Exception should have been generated");
}
TEST_CASE("Test REE-TEE isolation: Corrupted SP", "[exception]")
{
uintptr_t atk_sp = (uintptr_t)&_iram_start - 0x100;
/* Disable U-mode interrupts so the tick cannot preempt before the ecall */
__asm__ volatile("csrci ustatus, 0x1\n\t" : : : "memory");
/* Stop the REE-owned HW stack guard, as a malicious REE could */
#if CONFIG_ESP_SYSTEM_HW_STACK_GUARD
esp_hw_stack_guard_monitor_stop();
#endif
/* Cross into the TEE with the doctored sp; the handler rejects it and panics */
__asm__ volatile("mv sp, %0\n\t"
"ecall\n\t" : : "r"(atk_sp) : "memory");
TEST_FAIL_MESSAGE("Exception should have been generated");
}
static void do_stack_overflow(int depth, volatile uint8_t *sink)
{
if (depth == -1) {

1
components/esp_tee/test_apps/tee_test_fw/tee_exception_test_map.py
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@@ -23,6 +23,7 @@ _BASE_CONFIG = {
'DROM-R1': 'Load access fault',
'DROM-W1': 'Store access fault',
'MMU-spillover': 'Illegal instruction',
'Corrupted SP': 'Environment call from U-mode',
},
'apm_violation': {
'eFuse': 'APM - Space exception',