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RSE: BL2: Add multi sign support for MCUBOOT_HW_KEY
By default MCUBOOT_IMAGE_MULTI_SIG_SUPPORT is set to OFF, maintaining the existing single-signature behavior. When enabled, RSE secure image is also signed with additional ROTPK key. And both the signaures are verified during boot. This patch works with changes to mcuboot for multi-signature support (PR: mcu-tools/mcuboot#2305) Signed-off-by: Maulik Patel <[email protected]> Change-Id: Ic72d1dcfa3f3ada6c4d275281122f6d919a2d8e1
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‎bl2/ext/mcuboot/keys.c‎

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Original file line numberDiff line numberDiff line change
@@ -526,9 +526,11 @@ struct bootutil_key bootutil_keys[1] = {
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const int bootutil_key_cnt = 1;
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int boot_retrieve_public_key_hash(uint8_t image_index,
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uint8_t key_index,
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uint8_t *public_key_hash,
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size_t *key_hash_size)
531532
{
533+
(void) key_index;
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return tfm_plat_get_rotpk_hash(image_index,
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public_key_hash,
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(uint32_t *)key_hash_size);

‎platform/ext/target/arm/rse/common/CMakeLists.txt‎

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Original file line numberDiff line numberDiff line change
@@ -425,6 +425,9 @@ target_compile_definitions(platform_bl2
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$<$<BOOL:${PLATFORM_HOST_HAS_SCP}>:PLATFORM_HOST_HAS_SCP>
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$<$<BOOL:${RSE_USE_SDS_LIB}>:RSE_USE_SDS_LIB>
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$<$<BOOL:${RSE_BL2_ENABLE_IMAGE_STAGING}>:RSE_BL2_ENABLE_IMAGE_STAGING>
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$<$<BOOL:${MCUBOOT_IMAGE_MULTI_SIG_SUPPORT}>:MCUBOOT_IMAGE_MULTI_SIG_SUPPORT>
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$<$<BOOL:${MCUBOOT_ROTPK_SIGN_POLICY}>:MCUBOOT_ROTPK_SIGN_POLICY>
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MCUBOOT_ROTPK_MAX_KEYS_PER_IMAGE=${MCUBOOT_ROTPK_MAX_KEYS_PER_IMAGE}
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)
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target_compile_options(platform_bl2

‎platform/ext/target/arm/rse/common/bl2/rse_bl2_rotpk.c‎

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Original file line numberDiff line numberDiff line change
@@ -5,11 +5,14 @@
55
*
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*/
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#include <assert.h>
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#include <stdint.h>
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#include "tfm_plat_otp.h"
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#include <bootutil/sign_key.h>
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#include "rse_rotpk_mapping.h"
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#include "rse_rotpk_policy.h"
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#include "tfm_plat_crypto_keys.h"
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#ifdef MCUBOOT_HW_KEY
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static enum tfm_plat_err_t get_rotpk_hash(enum tfm_otp_element_id_t id,
@@ -41,7 +44,15 @@ struct bootutil_key bootutil_keys[1] = {
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.len = &pub_key_len,
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},
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};
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#ifdef MCUBOOT_IMAGE_MULTI_SIG_SUPPORT
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#define MAX_KEYS_PER_IMAGE MCUBOOT_ROTPK_MAX_KEYS_PER_IMAGE
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const int bootutil_key_cnt = MCUBOOT_IMAGE_NUMBER * MAX_KEYS_PER_IMAGE;
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#else
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const int bootutil_key_cnt = 1;
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#endif /* MCUBOOT_IMAGE_MULTI_SIG_SUPPORT */
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#ifndef MCUBOOT_IMAGE_MULTI_SIG_SUPPORT
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static enum tfm_plat_err_t get_otp_id(uint32_t image_index,
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enum tfm_otp_element_id_t *otp_id)
@@ -64,9 +75,11 @@ static enum tfm_plat_err_t get_otp_id(uint32_t image_index,
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}
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int boot_retrieve_public_key_hash(uint8_t image_index,
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uint8_t key_index,
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uint8_t *public_key_hash,
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size_t *key_hash_size)
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{
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(void)key_index;
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enum tfm_otp_element_id_t otp_id;
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enum tfm_plat_err_t err;
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@@ -78,6 +91,101 @@ int boot_retrieve_public_key_hash(uint8_t image_index,
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return get_rotpk_hash(otp_id, public_key_hash, key_hash_size);
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}
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#else
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static enum tfm_bl2_key_policy_t rse_policy_to_bl2_policy(enum rse_rotpk_policy policy)
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{
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switch(policy) {
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case RSE_ROTPK_POLICY_SIG_OPTIONAL:
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return TFM_BL2_KEY_MIGHT_SIGN;
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case RSE_ROTPK_POLICY_SIG_REQUIRED:
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return TFM_BL2_KEY_MUST_SIGN;
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default:
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assert(0 && "Invalid RSE ROTPK policy");
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return (enum tfm_bl2_key_policy_t)policy;
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}
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}
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/* Since for MCUBOOT_HW_KEY, key has is attached to the image, so inorder to
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* to identify the key policy after the signature is verified in mcuboot,
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* policy associated with the key is stored statically while the hash is matched
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*/
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static enum tfm_bl2_key_policy_t key_policy;
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int bl2_otp_get_key_policy(enum tfm_otp_element_id_t otp_id,
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enum tfm_bl2_key_policy_t *key_policy)
116+
{
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enum tfm_plat_err_t err;
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enum rse_rotpk_policy rse_policy;
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err = rse_rotpk_get_policy(otp_id, &rse_policy);
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if (err != TFM_PLAT_ERR_SUCCESS) {
122+
return -1;
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}
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*key_policy = rse_policy_to_bl2_policy(rse_policy);
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return 0;
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}
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int boot_retrieve_public_key_hash(uint8_t image_index,
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uint8_t key_index,
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uint8_t *public_key_hash,
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size_t *key_hash_size)
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{
135+
int rc;
136+
enum tfm_otp_element_id_t otp_id;
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switch (key_index) {
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case 0:
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/* Check CM key */
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otp_id = rse_cm_get_bl2_rotpk(image_index);
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break;
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case 1:
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/* Check DM key */
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otp_id = rse_dm_get_bl2_rotpk(image_index);
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break;
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default:
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/* Invalid key_index: only two keys are supported */
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return -1;
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}
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if (otp_id != PLAT_OTP_ID_INVALID) {
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rc = get_rotpk_hash(otp_id, public_key_hash, key_hash_size);
154+
if (rc != TFM_PLAT_ERR_SUCCESS) {
155+
return -1;
156+
}
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/* Get the key policy */
159+
rc = bl2_otp_get_key_policy(otp_id, &key_policy);
160+
if (rc != 0) {
161+
return -1;
162+
}
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}
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return 0;
166+
}
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int boot_plat_check_key_policy(bool valid_sig, psa_key_id_t key,
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bool *key_might_sign, bool *key_must_sign,
170+
uint8_t *key_must_sign_count)
171+
{
172+
(void)key;
173+
#ifndef MCUBOOT_ROTPK_SIGN_POLICY
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/* By default key policy is a MUST SIGN */
175+
key_policy = TFM_BL2_KEY_MUST_SIGN;
176+
#endif /* !MCUBOOT_ROTPK_SIGN_POLICY */
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178+
if (key_policy == TFM_BL2_KEY_MIGHT_SIGN) {
179+
*key_might_sign |= valid_sig;
180+
} else {
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*key_must_sign_count += 1;
182+
*key_might_sign |= valid_sig;
183+
*key_must_sign &= valid_sig;
184+
}
185+
return 0;
186+
}
187+
#endif /* !MCUBOOT_IMAGE_MULTI_SIG_SUPPORT */
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#else
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83191
/**

‎platform/ext/target/arm/rse/common/config.cmake‎

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Original file line numberDiff line numberDiff line change
@@ -126,6 +126,7 @@ set(CONFIG_BOOT_RAM_LOAD ON CACHE BOOL "Whether
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set(RSE_USE_HOST_FLASH ON CACHE BOOL "Enable RSE using the host flash.")
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set(RSE_LOAD_NS_IMAGE ON CACHE BOOL "Whether to load an RSE NSPE image")
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set(RSE_BL2_ENABLE_IMAGE_STAGING OFF CACHE BOOL "Whether to enable staging of the images to be loaded by BL2")
129+
set(MCUBOOT_IMAGE_MULTI_SIG_SUPPORT OFF CACHE BOOL "Whether to enable multi-signature support in MCUBoot")
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######################### Provisioning #########################################
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‎platform/ext/target/arm/rse/common/subplatform_pal_default_config/rse_rotpk_config.h‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -52,8 +52,8 @@ enum rse_host_rotpk_id {
5252
(RSE_ROTPK_DM_BL1_AMOUNT ? DM_ROTPK_BL1_0 : PLAT_OTP_ID_INVALID - PLAT_OTP_ID_DM_ROTPK)
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5454
#define RSE_DM_OTP_ID_FOR_BL2_IMAGE(id) \
55-
(RSE_ROTPK_DM_BL2_AMOUNT && \
56-
(id) == 1 ? DM_ROTPK_BL2_0 : PLAT_OTP_ID_INVALID - PLAT_OTP_ID_DM_ROTPK)
55+
((RSE_ROTPK_DM_BL2_AMOUNT && \
56+
((id) == 0 || (id) == 1)) ? DM_ROTPK_BL2_0 : PLAT_OTP_ID_INVALID - PLAT_OTP_ID_DM_ROTPK)
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5858
#define RSE_DM_OTP_ID_FOR_HOST(id) \
5959
(RSE_ROTPK_DM_HOST_AMOUNT ? DM_ROTPK_HOST_0 + (id) : PLAT_OTP_ID_INVALID - PLAT_OTP_ID_DM_ROTPK)

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