sys/psa_crypto: wipe temporary private key copies from stack

RIOT-OS · Sep 28, 2023 · 7ff1059 · 7ff1059
1 parent 2c51651
commit 7ff1059
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Showing 3 changed files with 18 additions and 7 deletions.
diff --git a/pkg/driver_cryptocell_310/psa_cryptocell_310/ecc_common.c b/pkg/driver_cryptocell_310/psa_cryptocell_310/ecc_common.c
@@ -21,6 +21,7 @@
 #include "psa_error.h"
 #include "psa_cryptocell_310_ecc_common.h"
 #include "cryptocell_310_util.h"
+#include "string_utils.h"
 
 #define ENABLE_DEBUG    0
 #include "debug.h"
@@ -67,6 +68,7 @@ psa_status_t cryptocell_310_common_ecc_generate_key_pair(uint8_t *priv_key_buffe
         return CRYS_to_psa_error(ret);
     }
 
+    explicit_bzero(&priv_key, sizeof(priv_key));
     return PSA_SUCCESS;
 }
 
@@ -89,7 +91,7 @@ psa_status_t cryptocell_310_common_ecc_sign(const uint8_t *priv_key,
     ret = CRYS_ECPKI_BuildPrivKey(pDomain, priv_key, priv_key_size, &user_priv_key);
     if (ret != CRYS_OK) {
         DEBUG("CRYS_ECPKI_BuildPrivKey failed with %s\n", cryptocell310_status_to_humanly_readable(ret));
-        return CRYS_to_psa_error(ret);
+        goto done;
     }
 
     cryptocell_310_enable();
@@ -99,10 +101,12 @@ psa_status_t cryptocell_310_common_ecc_sign(const uint8_t *priv_key,
     cryptocell_310_disable();
     if (ret != CRYS_OK) {
         DEBUG("CRYS_ECDSA_Sign failed with %s\n", cryptocell310_status_to_humanly_readable(ret));
-        return CRYS_to_psa_error(ret);
+        goto done;
     }
 
-    return PSA_SUCCESS;
+done:
+    explicit_bzero(&user_priv_key, sizeof(user_priv_key));
+    return CRYS_to_psa_error(ret);
 }
 
 psa_status_t cryptocell_310_common_ecc_verify(const uint8_t *pub_key,

diff --git a/pkg/driver_cryptocell_310/psa_cryptocell_310/ecc_ed25519.c b/pkg/driver_cryptocell_310/psa_cryptocell_310/ecc_ed25519.c
@@ -21,6 +21,7 @@
 #include "crys_ec_edw_api.h"
 #include "psa_error.h"
 #include "cryptocell_310_util.h"
+#include "string_utils.h"
 
 #define ENABLE_DEBUG    0
 #include "debug.h"
@@ -49,13 +50,15 @@ psa_status_t psa_generate_ecc_ed25519_key_pair( uint8_t *priv_key_buffer,
     cryptocell_310_disable();
     if (ret != CRYS_OK) {
         DEBUG("CRYS_ECEDW_KeyPair failed with %s\n", cryptocell310_status_to_humanly_readable(ret));
-        return CRYS_to_psa_error(ret);
+        goto done;
     }
 
     memcpy(priv_key_buffer, secret_key, CRYS_ECEDW_ORD_SIZE_IN_BYTES);
     memcpy(pub_key_buffer, &secret_key[CRYS_ECEDW_ORD_SIZE_IN_BYTES], CRYS_ECEDW_MOD_SIZE_IN_BYTES);
 
-    return PSA_SUCCESS;
+done:
+    explicit_bzero(&secret_key, sizeof(secret_key));
+    return CRYS_to_psa_error(ret);
 }
 
 psa_status_t psa_ecc_ed25519_sign_message(const uint8_t *priv_key_buffer,
@@ -91,10 +94,12 @@ psa_status_t psa_ecc_ed25519_sign_message(const uint8_t *priv_key_buffer,
     cryptocell_310_disable();
     if (ret != CRYS_OK) {
         DEBUG("CRYS_ECEDW_Sign failed with %s\n", cryptocell310_status_to_humanly_readable(ret));
-        return CRYS_to_psa_error(ret);
+        goto done;
     }
 
-    return PSA_SUCCESS;
+done:
+    explicit_bzero(&secret_key, sizeof(secret_key));
+    return CRYS_to_psa_error(ret);
 
     (void)signature_size;
 }

diff --git a/pkg/driver_cryptocell_310/psa_cryptocell_310/error_conversion.c b/pkg/driver_cryptocell_310/psa_cryptocell_310/error_conversion.c
@@ -23,6 +23,8 @@
 psa_status_t CRYS_to_psa_error(CRYSError_t error)
 {
     switch (error) {
+    case CRYS_OK:
+        return PSA_SUCCESS;
     case CRYS_HASH_ILLEGAL_OPERATION_MODE_ERROR:
     case CRYS_HASH_IS_NOT_SUPPORTED:
         return PSA_ERROR_NOT_SUPPORTED;