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change(esp_tee): Force non-deterministic ECDSA signing for TEE secure storage keys

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This commit is contained in:
Laukik Hase
2026-07-03 17:19:17 +05:30
parent 4812dbd2d8
commit 427dc875b9
4 changed files with 45 additions and 23 deletions
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6
components/esp_tee/subproject/components/tee_sec_storage/tee_sec_storage.c
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@@ -575,11 +575,9 @@ esp_err_t esp_tee_sec_storage_ecdsa_sign(const esp_tee_sec_storage_key_cfg_t *cf
psa_set_key_type(&key_attributes, PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_SECP_R1));
psa_set_key_usage_flags(&key_attributes, PSA_KEY_USAGE_SIGN_HASH | PSA_KEY_USAGE_EXPORT | PSA_KEY_USAGE_VERIFY_HASH);
psa_algorithm_t ecdsa_alg = PSA_ALG_ECDSA(PSA_ALG_SHA_256);
#if CONFIG_MBEDTLS_ECDSA_DETERMINISTIC
ecdsa_alg = PSA_ALG_DETERMINISTIC_ECDSA(PSA_ALG_SHA_256);
#endif
/* ECDSA signatures over TEE secure-storage keys are compulsorily non-deterministic */
psa_algorithm_t ecdsa_alg = PSA_ALG_ECDSA(PSA_ALG_SHA_256);
psa_set_key_algorithm(&key_attributes, ecdsa_alg);

52
components/esp_tee/test_apps/tee_test_fw/main/test_esp_tee_sec_stg.c
View File

@@ -145,6 +145,43 @@ TEST_CASE("Test TEE Secure Storage - Sign-verify (ecdsa_secp256r1)", "[sec_stora
}
}
TEST_CASE("Test TEE Secure Storage - Signatures are non-deterministic (ecdsa_secp256r1)", "[sec_storage]")
{
const size_t sig_len = 2 * ECDSA_SECP256R1_KEY_LEN;
uint8_t msg_digest[SHA256_DIGEST_SZ];
esp_fill_random(msg_digest, sizeof(msg_digest));
esp_tee_sec_storage_key_cfg_t key_cfg = {
.id = "ecdsa_nondet",
.type = ESP_SEC_STG_KEY_ECDSA_SECP256R1
};
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_OK(esp_tee_sec_storage_gen_key(&key_cfg));
esp_tee_sec_storage_ecdsa_pubkey_t pubkey = {};
TEST_ESP_OK(esp_tee_sec_storage_ecdsa_get_pubkey(&key_cfg, &pubkey));
uint8_t signatures[MAX_SEC_STG_ITER][2 * ECDSA_SECP256R1_KEY_LEN];
for (unsigned int i = 0; i < MAX_SEC_STG_ITER; i++) {
esp_tee_sec_storage_ecdsa_sign_t sign = {};
TEST_ESP_OK(esp_tee_sec_storage_ecdsa_sign(&key_cfg, msg_digest, sizeof(msg_digest), &sign));
TEST_ESP_OK(verify_ecdsa_sign(key_cfg.type, msg_digest, sizeof(msg_digest), &pubkey, &sign));
for (unsigned int j = 0; j < i; j++) {
TEST_ASSERT_TRUE_MESSAGE(memcmp(sign.signature, signatures[j], sig_len) != 0,
"ECDSA signature repeated - deterministic signing detected");
}
memcpy(signatures[i], sign.signature, sig_len);
}
TEST_ESP_OK(esp_tee_sec_storage_clear_key(key_cfg.id));
}
#if CONFIG_SECURE_TEE_SEC_STG_SUPPORT_SECP384R1_SIGN
TEST_CASE("Test TEE Secure Storage - Sign-verify (ecdsa_secp384r1)", "[sec_storage]")
{
@@ -686,21 +723,6 @@ static void test_ecdsa_sign(esp_ecdsa_curve_t curve)
TEST_ASSERT_EQUAL_HEX32(PSA_SUCCESS, status);
TEST_ASSERT_EQUAL(signature_len, 2 * key_len);
#if CONFIG_MBEDTLS_ECDSA_DETERMINISTIC
uint8_t signature_det_verify[2 * ECDSA_SECP384R1_KEY_LEN];
size_t signature_det_verify_len = 0;
status = psa_sign_hash(priv_key_id,
alg,
sha, sha_len,
signature_det_verify, 2 * key_len,
&signature_det_verify_len);
TEST_ASSERT_EQUAL_HEX32(PSA_SUCCESS, status);
TEST_ASSERT_EQUAL(signature_det_verify_len, signature_len);
TEST_ASSERT_EQUAL_HEX8_ARRAY(signature, signature_det_verify, signature_len);
#endif
psa_set_key_type(&pub_key_attr, PSA_KEY_TYPE_ECC_PUBLIC_KEY(PSA_ECC_FAMILY_SECP_R1));
psa_set_key_bits(&pub_key_attr, key_len * 8);
psa_set_key_usage_flags(&pub_key_attr, PSA_KEY_USAGE_VERIFY_HASH);

6
components/mbedtls/esp_tee/esp_tee_mbedtls_config.h
View File

@@ -61,12 +61,10 @@
#endif
#define PSA_WANT_ECC_SECP_R1_256 1
#ifdef CONFIG_MBEDTLS_ECDSA_DETERMINISTIC
#define PSA_WANT_ALG_DETERMINISTIC_ECDSA 1
#else
/* ECDSA signatures over TEE secure-storage keys are compulsorily
* non-deterministic (randomized nonce) */
#undef PSA_WANT_ALG_DETERMINISTIC_ECDSA
#undef MBEDTLS_HMAC_DRBG_C
#endif
#if SOC_SHA_SUPPORTED
#define ESP_SHA_DRIVER_ENABLED

4
components/mbedtls/port/psa_driver/esp_ecdsa/psa_crypto_driver_esp_ecdsa.c
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@@ -1003,6 +1003,10 @@ psa_status_t esp_ecdsa_opaque_sign_hash_complete(
#if CONFIG_MBEDTLS_TEE_SEC_STG_ECDSA_SIGN
if (key_source == ESP_ECDSA_KEY_SOURCE_TEE) {
/* TEE key path */
if (PSA_ALG_ECDSA_IS_DETERMINISTIC(operation->alg)) {
ESP_LOGW(TAG, "Deterministic ECDSA unsupported for TEE keys; using randomized nonce");
}
const char *tee_key_id = NULL;
uint8_t stored_curve;