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feat(esp_tee): Restrict REE access to TEE-owned secure storage keys

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This commit is contained in:
Laukik Hase
2026-09-03 12:15:31 +05:30
parent 6a605263e8
commit a1bc64d14e
13 changed files with 170 additions and 45 deletions
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components/esp_tee/scripts/esp_tee_sec_stg_keygen/README.md
+3 -1
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@@ -18,6 +18,8 @@ options:
-o, --output OUTPUT output binary file name
-i, --input INPUT input key file (.pem for ecdsa, .bin for aes)
--write-once make key persistent - cannot be modified or deleted once written
--tee-only mark key as owned exclusively by the TEE - the REE cannot use, generate or clear it
-h, --help Show this message and exit
```
### ECDSA Keys
@@ -31,7 +33,7 @@ python esp_tee_sec_stg_keygen.py -k ecdsa_p192 -o ecdsa_p192_k0.bin
```bash
openssl ecparam -name prime256v1 -genkey -noout -out ecdsa_p256.pem
python esp_tee_sec_stg_keygen.py -k ecdsa_p256 -o ecdsa_p256_k1.bin -i ecdsa_p256.pem --write-once
python esp_tee_sec_stg_keygen.py -k ecdsa_p256 -o ecdsa_p256_k1.bin -i ecdsa_p256.pem --write-once --tee-only
```
### AES-256 Key
components/esp_tee/scripts/esp_tee_sec_stg_keygen/esp_tee_sec_stg_keygen.py
+10
View File
@@ -32,6 +32,7 @@ class KeyType(Enum):
class Flags(IntFlag):
NONE = 0x00000000
WRITE_ONCE = 0x00000001
TEE_ONLY = 0x00000002
# === Key Generators ===
@@ -113,6 +114,11 @@ def parse_args() -> argparse.Namespace:
action='store_true',
help='make key persistent - cannot be modified or deleted once written',
)
parser.add_argument(
'--tee-only',
action='store_true',
help='mark key as owned exclusively by the TEE - the REE cannot use, generate or clear it',
)
return parser.parse_args()
@@ -123,12 +129,16 @@ def main() -> None:
flags = Flags.NONE
if args.write_once:
flags |= Flags.WRITE_ONCE
if args.tee_only:
flags |= Flags.TEE_ONLY
print(f'[+] Generating key of type: {key_type.name} (value: {key_type.value})')
if args.input:
print(f'[+] Using user-provided key file: {args.input}')
if args.write_once:
print('[+] WRITE_ONCE flag is set')
if args.tee_only:
print('[+] TEE_ONLY flag is set')
key_data = generate_key_data(key_type, flags, args.input)
components/esp_tee/subproject/components/attestation/esp_att_utils_crypto.c
+2
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@@ -46,6 +46,8 @@ static esp_err_t gen_ecdsa_keypair_secp256r1(esp_att_ecdsa_keypair_t *keypair)
esp_tee_sec_storage_key_cfg_t key_cfg = {
.id = (const char *)(ESP_ATT_TK_KEY_ID),
.type = ESP_SEC_STG_KEY_ECDSA_SECP256R1,
/* The attestation key must never be usable from the REE */
.flags = SEC_STORAGE_FLAG_TEE_ONLY,
};
esp_err_t err = esp_tee_sec_storage_gen_key(&key_cfg);
components/esp_tee/subproject/components/tee_sec_storage/include/esp_tee_sec_storage.h
+23 -1
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@@ -16,12 +16,19 @@ extern "C" {
#include "esp_err.h"
#include "esp_bit_defs.h"
#define MAX_ECDSA_SUPPORTED_KEY_LEN 32 /*!< Maximum supported size for the ECDSA key */
#include "sdkconfig.h"
#if CONFIG_SECURE_TEE_SEC_STG_SUPPORT_SECP384R1_SIGN
#define MAX_ECDSA_SUPPORTED_KEY_LEN 48 /*!< Maximum supported size for the ECDSA key (SECP384R1) */
#else
#define MAX_ECDSA_SUPPORTED_KEY_LEN 32 /*!< Maximum supported size for the ECDSA key (SECP256R1) */
#endif /* CONFIG_SECURE_TEE_SEC_STG_SUPPORT_SECP384R1_SIGN */
#define MAX_AES_SUPPORTED_KEY_LEN 32 /*!< Maximum supported size for the AES key */
#define AES_GCM_SUPPORTED_IV_LEN 12 /*!< Supported IV length for AES-GCM operations */
#define SEC_STORAGE_FLAG_NONE 0 /*!< No flags */
#define SEC_STORAGE_FLAG_WRITE_ONCE BIT(0) /*!< Data can only be written once */
#define SEC_STORAGE_FLAG_TEE_ONLY BIT(1) /*!< Key is owned exclusively by the TEE */
/**
* @brief Enum to represent the type of key stored in the secure storage
@@ -94,6 +101,21 @@ typedef struct {
* @return esp_err_t ESP_OK on success, appropriate error code otherwise.
*/
esp_err_t esp_tee_sec_storage_init(void);
/**
* @brief Check whether a key ID is owned exclusively by the TEE
*
* A key is TEE-owned if either:
* - it refers to the reserved TEE attestation key
* (`CONFIG_SECURE_TEE_ATT_KEY_STR_ID`); this also blocks the REE from
* "squatting" the ID before the TEE creates the key, or
* - the stored key carries the ::SEC_STORAGE_FLAG_TEE_ONLY flag.
*
* @param key_id NULL-terminated key identifier string (may be NULL)
*
* @return true if the key is TEE-owned (REE access must be denied), false otherwise
*/
bool esp_tee_sec_storage_is_key_tee_owned(const char *key_id);
#endif
/**
components/esp_tee/subproject/components/tee_sec_storage/tee_sec_storage.c
+23
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@@ -211,6 +211,29 @@ static esp_err_t secure_storage_read(const char *key_id, void *data, size_t *len
return nvs_get_blob(tee_nvs_hdl, key_id, data, len);
}
bool esp_tee_sec_storage_is_key_tee_owned(const char *key_id)
{
if (key_id == NULL) {
return false;
}
bool is_att_key = false, is_tee_only = false;
esp_err_t err = ESP_FAIL;
#if CONFIG_SECURE_TEE_ATTESTATION
is_att_key = (strncmp(key_id, CONFIG_SECURE_TEE_ATT_KEY_STR_ID, NVS_KEY_NAME_MAX_SIZE) == 0);
#endif
sec_stg_key_t keyctx = {};
size_t keyctx_len = sizeof(keyctx);
err = secure_storage_read(key_id, (void *)&keyctx, &keyctx_len);
is_tee_only = (err == ESP_OK) && ((keyctx.flags & SEC_STORAGE_FLAG_TEE_ONLY) != 0);
mbedtls_platform_zeroize(&keyctx, sizeof(keyctx));
return (is_att_key || is_tee_only);
}
/* ---------------------------------------------- Interface APIs ------------------------------------------------- */
esp_err_t esp_tee_sec_storage_init(void)
components/esp_tee/subproject/main/core/esp_secure_services.c
+11 -4
View File
@@ -545,17 +545,24 @@ int _ss_esp_tee_ota_end(void)
*/
esp_err_t _ss_esp_tee_sec_storage_clear_key(const char *key_id)
{
bool valid_arg = !esp_tee_sec_storage_is_key_tee_owned(key_id);
if (!valid_arg) {
return ESP_ERR_INVALID_ARG;
}
ESP_FAULT_ASSERT(valid_arg);
return esp_tee_sec_storage_clear_key(key_id);
}
esp_err_t _ss_esp_tee_sec_storage_gen_key(const esp_tee_sec_storage_key_cfg_t *cfg)
{
bool valid_addr = esp_tee_buf_in_ree(cfg, sizeof(esp_tee_sec_storage_key_cfg_t));
if (!valid_addr) {
bool valid_arg = esp_tee_buf_in_ree(cfg, sizeof(esp_tee_sec_storage_key_cfg_t)) &&
!(cfg->flags & SEC_STORAGE_FLAG_TEE_ONLY) &&
!esp_tee_sec_storage_is_key_tee_owned(cfg->id);
if (!valid_arg) {
return ESP_ERR_INVALID_ARG;
}
ESP_FAULT_ASSERT(valid_addr);
ESP_FAULT_ASSERT(valid_arg);
return esp_tee_sec_storage_gen_key(cfg);
}
components/esp_tee/subproject/main/core/esp_secure_services_iram.c
+27 -27
View File
@@ -193,67 +193,67 @@ void _ss_wdt_hal_deinit(wdt_hal_context_t *hal)
*/
esp_err_t _ss_esp_tee_sec_storage_ecdsa_sign(const esp_tee_sec_storage_key_cfg_t *cfg, const uint8_t *hash, size_t hlen, esp_tee_sec_storage_ecdsa_sign_t *out_sign)
{
bool valid_addr = (esp_tee_buf_in_ree(cfg, sizeof(esp_tee_sec_storage_key_cfg_t)) &&
esp_tee_buf_in_ree(hash, hlen) &&
esp_tee_buf_in_ree(out_sign, sizeof(esp_tee_sec_storage_ecdsa_sign_t)));
if (!valid_addr) {
bool valid_arg = (esp_tee_buf_in_ree(cfg, sizeof(esp_tee_sec_storage_key_cfg_t)) &&
esp_tee_buf_in_ree(hash, hlen) &&
esp_tee_buf_in_ree(out_sign, sizeof(esp_tee_sec_storage_ecdsa_sign_t)) &&
!esp_tee_sec_storage_is_key_tee_owned(cfg->id));
if (!valid_arg) {
return ESP_ERR_INVALID_ARG;
}
ESP_FAULT_ASSERT(valid_addr);
ESP_FAULT_ASSERT(valid_arg);
return esp_tee_sec_storage_ecdsa_sign(cfg, hash, hlen, out_sign);
}
esp_err_t _ss_esp_tee_sec_storage_ecdsa_get_pubkey(const esp_tee_sec_storage_key_cfg_t *cfg, esp_tee_sec_storage_ecdsa_pubkey_t *out_pubkey)
{
bool valid_addr = (esp_tee_buf_in_ree(cfg, sizeof(esp_tee_sec_storage_key_cfg_t)) &&
esp_tee_buf_in_ree(out_pubkey, sizeof(esp_tee_sec_storage_ecdsa_pubkey_t)));
if (!valid_addr) {
bool valid_arg = (esp_tee_buf_in_ree(cfg, sizeof(esp_tee_sec_storage_key_cfg_t)) &&
esp_tee_buf_in_ree(out_pubkey, sizeof(esp_tee_sec_storage_ecdsa_pubkey_t)) &&
!esp_tee_sec_storage_is_key_tee_owned(cfg->id));
if (!valid_arg) {
return ESP_ERR_INVALID_ARG;
}
ESP_FAULT_ASSERT(valid_addr);
ESP_FAULT_ASSERT(valid_arg);
return esp_tee_sec_storage_ecdsa_get_pubkey(cfg, out_pubkey);
}
esp_err_t _ss_esp_tee_sec_storage_aead_encrypt(esp_tee_sec_storage_aead_ctx_t *ctx, uint8_t *tag, size_t tag_len, uint8_t *output)
{
bool valid_addr = (esp_tee_buf_in_ree(ctx, sizeof(esp_tee_sec_storage_aead_ctx_t)) &&
esp_tee_buf_in_ree(ctx->input, ctx->input_len) &&
esp_tee_buf_in_ree(ctx->iv, AES_GCM_SUPPORTED_IV_LEN) &&
esp_tee_buf_in_ree(tag, tag_len) &&
esp_tee_buf_in_ree(output, ctx->input_len));
bool valid_arg = (esp_tee_buf_in_ree(ctx, sizeof(esp_tee_sec_storage_aead_ctx_t)) &&
esp_tee_buf_in_ree(ctx->input, ctx->input_len) &&
esp_tee_buf_in_ree(tag, tag_len) &&
esp_tee_buf_in_ree(output, ctx->input_len) &&
!esp_tee_sec_storage_is_key_tee_owned(ctx->key_id));
if (ctx->aad_len != 0) {
valid_addr &= esp_tee_buf_in_ree(ctx->aad, ctx->aad_len);
valid_arg &= esp_tee_buf_in_ree(ctx->aad, ctx->aad_len);
}
if (!valid_addr) {
if (!valid_arg) {
return ESP_ERR_INVALID_ARG;
}
ESP_FAULT_ASSERT(valid_addr);
ESP_FAULT_ASSERT(valid_arg);
return esp_tee_sec_storage_aead_encrypt(ctx, tag, tag_len, output);
}
esp_err_t _ss_esp_tee_sec_storage_aead_decrypt(const esp_tee_sec_storage_aead_ctx_t *ctx, const uint8_t *tag, size_t tag_len, uint8_t *output)
{
bool valid_addr = (esp_tee_buf_in_ree(ctx, sizeof(esp_tee_sec_storage_aead_ctx_t)) &&
esp_tee_buf_in_ree(ctx->input, ctx->input_len) &&
esp_tee_buf_in_ree(ctx->iv, AES_GCM_SUPPORTED_IV_LEN) &&
esp_tee_buf_in_ree(tag, tag_len) &&
esp_tee_buf_in_ree(output, ctx->input_len));
bool valid_arg = (esp_tee_buf_in_ree(ctx, sizeof(esp_tee_sec_storage_aead_ctx_t)) &&
esp_tee_buf_in_ree(ctx->input, ctx->input_len) &&
esp_tee_buf_in_ree(tag, tag_len) &&
esp_tee_buf_in_ree(output, ctx->input_len) &&
!esp_tee_sec_storage_is_key_tee_owned(ctx->key_id));
if (ctx->aad_len != 0) {
valid_addr &= esp_tee_buf_in_ree(ctx->aad, ctx->aad_len);
valid_arg &= esp_tee_buf_in_ree(ctx->aad, ctx->aad_len);
}
if (!valid_addr) {
if (!valid_arg) {
return ESP_ERR_INVALID_ARG;
}
ESP_FAULT_ASSERT(valid_addr);
ESP_FAULT_ASSERT(valid_arg);
return esp_tee_sec_storage_aead_decrypt(ctx, tag, tag_len, output);
}
components/esp_tee/test_apps/tee_cli_app/main/tee_srv_sec_str.c
+1 -1
View File
@@ -219,7 +219,7 @@ static int tee_sec_stg_gen_key(int argc, char **argv)
err = esp_tee_sec_storage_clear_key(cfg.id);
if (err != ESP_OK && err != ESP_ERR_NOT_FOUND) {
ESP_LOGE(TAG, "Failed to clear key %d!", cfg.id);
ESP_LOGE(TAG, "Failed to clear key %s!", cfg.id);
goto exit;
}
components/esp_tee/test_apps/tee_cli_app/pytest_tee_cli.py
+1 -5
View File
@@ -1,4 +1,4 @@
# SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
# SPDX-FileCopyrightText: 2024-2026 Espressif Systems (Shanghai) CO LTD
# SPDX-License-Identifier: Apache-2.0
import hashlib
import http.server
@@ -134,10 +134,6 @@ def test_tee_cli_attestation(dut: Dut) -> None:
dut.expect('ESP-TEE: Secure services demonstration', timeout=30)
time.sleep(1)
att_key_id = dut.app.sdkconfig.get('SECURE_TEE_ATT_KEY_STR_ID')
dut.write(f'tee_sec_stg_gen_key {att_key_id} 1')
dut.expect(r'Generated ECDSA_SECP256R1 key with ID (\S+)', timeout=30)
# Get the Entity Attestation token from TEE and verify its signature
dut.write('tee_att_info')
dut.expect(r'Attestation token - Length: (\d+)', timeout=30)
components/esp_tee/test_apps/tee_test_fw/conftest.py
+2
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@@ -289,6 +289,7 @@ class TEESerial(IdfSerial):
'type': 'ecdsa_p256',
'input': 'ecdsa_p256_key.pem',
'write_once': True,
'tee_only': True,
'b64': (
'LS0tLS1CRUdJTiBFQyBQUklWQVRFIEtFWS0tLS0tCk1IY0NBUUVFSUlNU1VpUktHaVZjSTIvbUZFekI3eXRIOVJj'
'd0wyUThkNDhONHNFUHFYc0RvQW9HQ0NxR1NNNDkKQXdFSG9VUURRZ0FFSkYxYXRZQUxrdnB4cCt4N3c1dmVPQ1Vj'
@@ -349,6 +350,7 @@ class TEESerial(IdfSerial):
[sys.executable, ESP_TEE_SEC_STG_KEYGEN, '-k', entry['type'], '-o', str(tmp_dir / f'{entry["key"]}.bin')]
+ (['-i', entry['input']] if entry['input'] else [])
+ (['--write-once'] if entry['write_once'] else [])
+ (['--tee-only'] if entry.get('tee_only') else [])
for entry in self.KEY_DEFS
]
components/esp_tee/test_apps/tee_test_fw/main/test_esp_tee_sec_stg.c
+61 -4
View File
@@ -1,5 +1,5 @@
/*
* SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
* SPDX-FileCopyrightText: 2024-2026 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
@@ -327,6 +327,38 @@ TEST_CASE("Test TEE Secure Storage - Null Pointer and Zero Length", "[sec_storag
TEST_ESP_OK(esp_tee_sec_storage_clear_key(key_cfg.id));
}
#if CONFIG_SECURE_TEE_ATTESTATION
TEST_CASE("Test TEE Secure Storage - Attestation key is not REE-accessible", "[sec_storage]")
{
const char *att_key_id = CONFIG_SECURE_TEE_ATT_KEY_STR_ID;
esp_tee_sec_storage_key_cfg_t key_cfg = {
.id = att_key_id,
.type = ESP_SEC_STG_KEY_ECDSA_SECP256R1
};
uint8_t digest[SHA256_DIGEST_SZ];
esp_fill_random(digest, sizeof(digest));
TEST_ESP_ERR(ESP_ERR_INVALID_ARG, esp_tee_sec_storage_gen_key(&key_cfg));
TEST_ESP_ERR(ESP_ERR_INVALID_ARG, esp_tee_sec_storage_clear_key(att_key_id));
esp_tee_sec_storage_ecdsa_sign_t sign = {};
esp_tee_sec_storage_ecdsa_pubkey_t pubkey = {};
TEST_ESP_ERR(ESP_ERR_INVALID_ARG, esp_tee_sec_storage_ecdsa_sign(&key_cfg, digest, sizeof(digest), &sign));
TEST_ESP_ERR(ESP_ERR_INVALID_ARG, esp_tee_sec_storage_ecdsa_get_pubkey(&key_cfg, &pubkey));
uint8_t data[31], tag[12];
esp_tee_sec_storage_aead_ctx_t aead_ctx = {
.key_id = att_key_id,
.input = data,
.input_len = sizeof(data),
};
TEST_ESP_ERR(ESP_ERR_INVALID_ARG, esp_tee_sec_storage_aead_encrypt(&aead_ctx, tag, sizeof(tag), data));
TEST_ESP_ERR(ESP_ERR_INVALID_ARG, esp_tee_sec_storage_aead_decrypt(&aead_ctx, tag, sizeof(tag), data));
}
#endif
TEST_CASE("Test TEE Secure Storage - WRITE_ONCE keys", "[sec_storage]")
{
const char *key_id = "key_id_test_wo";
@@ -346,6 +378,22 @@ TEST_CASE("Test TEE Secure Storage - WRITE_ONCE keys", "[sec_storage]")
TEST_ESP_ERR(ESP_ERR_INVALID_STATE, esp_tee_sec_storage_clear_key(key_cfg.id));
}
TEST_CASE("Test TEE Secure Storage - TEE_ONLY keys", "[sec_storage]")
{
const char *key_id = "key_id_tee_only";
esp_tee_sec_storage_key_cfg_t key_cfg = {
.id = key_id,
.type = ESP_SEC_STG_KEY_ECDSA_SECP256R1,
.flags = SEC_STORAGE_FLAG_TEE_ONLY,
};
esp_err_t err = esp_tee_sec_storage_clear_key(key_cfg.id);
TEST_ASSERT_TRUE(err == ESP_OK || err == ESP_ERR_NOT_FOUND);
TEST_ESP_ERR(ESP_ERR_INVALID_ARG, esp_tee_sec_storage_gen_key(&key_cfg));
TEST_ESP_ERR(ESP_ERR_NOT_FOUND, esp_tee_sec_storage_clear_key(key_cfg.id));
}
static void test_aead_encrypt_decrypt(const char *key_id, const uint8_t *input, size_t len)
{
uint8_t *ciphertext = heap_caps_malloc(len, MALLOC_CAP_8BIT | MALLOC_CAP_INTERNAL);
@@ -425,9 +473,19 @@ TEST_CASE("Test TEE Secure Storage - Host-generated keys", "[sec_storage_host_ke
uint32_t token_len = 0;
TEST_ESP_OK(esp_tee_att_generate_token(0xA1B2C3D4, 0x0FACADE0, (const char *)ESP_ATT_TK_PSA_CERT_REF,
token_buf, ESP_ATT_TK_BUF_SIZE, &token_len));
free(token_buf);
#endif
#endif /* CONFIG_SECURE_TEE_ATTESTATION */
esp_tee_sec_storage_key_cfg_t attest_cfg = {
.id = attest_key_id,
.type = ESP_SEC_STG_KEY_ECDSA_SECP256R1,
};
esp_tee_sec_storage_ecdsa_sign_t attest_sign = {0};
esp_tee_sec_storage_ecdsa_pubkey_t attest_pubkey = {0};
TEST_ESP_ERR(ESP_ERR_INVALID_ARG, esp_tee_sec_storage_ecdsa_sign(&attest_cfg, msg_digest, SHA256_DIGEST_SZ, &attest_sign));
TEST_ESP_ERR(ESP_ERR_INVALID_ARG, esp_tee_sec_storage_ecdsa_get_pubkey(&attest_cfg, &attest_pubkey));
TEST_ESP_ERR(ESP_ERR_INVALID_ARG, esp_tee_sec_storage_clear_key(attest_key_id));
}
#if CONFIG_MBEDTLS_TEE_SEC_STG_ECDSA_SIGN
@@ -470,7 +528,6 @@ static void test_ecdsa_sign(mbedtls_ecp_group_id gid)
mbedtls_mpi_init(&s);
mbedtls_ecdsa_context ecdsa_context;
mbedtls_ecdsa_init(&ecdsa_context);
TEST_ASSERT_MBEDTLS_OK(mbedtls_ecp_group_load(&ecdsa_context.MBEDTLS_PRIVATE(grp), gid));