unit-test/keystore: simplify mocking of random AES IV

`random_32_bytes()` is used for multiple purposes, e.g. creating a
seed, creating random IVs, etc.

In combination with cmocka, this makes it difficult to write and
maintain unit tests.

This commit allows to mock the IV specifically without affecting other
uses of random_32_bytes().

Author: benma

src/cipher/cipher.c

@@ -22,6 +22,10 @@
 #include <util.h>
 #include <wally_crypto.h>
 
+#ifdef TESTING
+#include <mock_cipher.h>
+#endif
+
 #define N_BLOCK (16U)
 // Used to sanity-check input to avoid large stack allocations
 #define CIPHER_MAX_ALLOC (200U)
@@ -65,7 +69,11 @@ static bool _aes_encrypt(
     }
 
     uint8_t iv[32] = {0}; // only 16 bytes needed for IV.
+#ifdef TESTING
+    cipher_mock_iv(iv);
+#else
     random_32_bytes(iv);
+#endif
     memcpy(out, iv, N_BLOCK);
 
     AES256_CBC_ctx ctx = {0};

test/unit-test/CMakeLists.txt

@@ -61,6 +61,7 @@ add_library(bitbox_objects
   ${CTAES-SOURCES}
   ${ETHEREUM-SOURCES}
   framework/mock_blocking.c
+  framework/mock_cipher.c
   framework/mock_screen.c
   framework/mock_screen_stack.c
   framework/mock_memory.c
@@ -234,7 +235,7 @@ set(TEST_LIST
    salt
    "-Wl,--wrap=memory_get_salt_root"
    cipher
-   "-Wl,--wrap=random_32_bytes"
+   "-Wl,--wrap=cipher_mock_iv"
    util
    ""
    workflow_blocking

test/unit-test/framework/includes/mock_cipher.h

@@ -0,0 +1,22 @@
+// Copyright 2023 Shift Crypto AG
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef _MOCK_CIPHER_H_
+#define _MOCK_CIPHER_H_
+
+#include <stdint.h>
+
+void cipher_mock_iv(uint8_t* iv_out);
+
+#endif

test/unit-test/framework/includes/mock_memory.h

@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#ifndef _MOCK_MOCK_H_
-#define _MOCK_MOCK_H_
+#ifndef _MOCK_MEMORY_H_
+#define _MOCK_MEMORY_H_
 
 #include <stdbool.h>
 #include <stdint.h>

test/unit-test/framework/mock_cipher.c

@@ -0,0 +1,22 @@
+// Copyright 2023 Shift Crypto AG
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <string.h>
+
+#include <mock_cipher.h>
+
+void cipher_mock_iv(uint8_t* iv_out)
+{
+    memset(iv_out, 'a', 32);
+}

test/unit-test/test_cipher.c

@@ -21,9 +21,9 @@
 #include <stdlib.h>
 #include <string.h>
 
-void __wrap_random_32_bytes(uint8_t* buf)
+void __wrap_cipher_mock_iv(uint8_t* iv_out)
 {
-    memcpy(buf, (const uint8_t*)mock(), 32);
+    memcpy(iv_out, (const uint8_t*)mock(), 32);
 }
 
 typedef struct {
@@ -3839,7 +3839,7 @@ static void _test_cipher_aes_hmac_encrypt(void** state)
         const test_t* test = &_tests[i];
         uint8_t rand_mock[32] = {0};
         memcpy(rand_mock, test->iv, 16);
-        will_return(__wrap_random_32_bytes, rand_mock);
+        will_return(__wrap_cipher_mock_iv, rand_mock);
         size_t cipher_len = test->msg_len + 64;
         uint8_t cipher[cipher_len];
         assert_true(

test/unit-test/test_keystore.c

@@ -57,8 +57,6 @@ static uint8_t _mock_bip39_seed[64] = {
     0x33, 0x33, 0x33, 0x33, 0x33, 0x33, 0x33, 0x33, 0x44, 0x44, 0x44, 0x44, 0x44, 0x44, 0x44, 0x44,
 };
 
-const uint8_t _aes_iv[32] = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
-
 static const uint32_t _keypath[] = {
     44 + BIP32_INITIAL_HARDENED_CHILD,
     0 + BIP32_INITIAL_HARDENED_CHILD,
@@ -259,9 +257,6 @@ static void _test_keystore_secp256k1_sign(void** state)
 static void _expect_encrypt_and_store_seed(void)
 {
     will_return(__wrap_memory_is_initialized, false);
-
-    // For the AES IV:
-    will_return(__wrap_random_32_bytes, _aes_iv);
 }
 
 static void _test_keystore_encrypt_and_store_seed(void** state)