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fix: prevent NULL valuestring dereference in cJSONUtils_ApplyPatches #1033

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fix: prevent NULL valuestring dereference in cJSONUtils_ApplyPatches #1033

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6 changes: 3 additions & 3 deletions cJSON_Utils.c
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Original file line number Diff line number Diff line change
Expand Up @@ -742,7 +742,7 @@ enum patch_operation { INVALID, ADD, REMOVE, REPLACE, MOVE, COPY, TEST };
static enum patch_operation decode_patch_operation(const cJSON * const patch, const cJSON_bool case_sensitive)
{
cJSON *operation = get_object_item(patch, "op", case_sensitive);
if (!cJSON_IsString(operation))
if (!cJSON_IsString(operation) || (operation->valuestring == NULL))
{
return INVALID;
}
Expand Down Expand Up @@ -815,7 +815,7 @@ static int apply_patch(cJSON *object, const cJSON *patch, const cJSON_bool case_
int status = 0;

path = get_object_item(patch, "path", case_sensitive);
if (!cJSON_IsString(path))
if (!cJSON_IsString(path) || (path->valuestring == NULL))
{
/* malformed patch. */
status = 2;
Expand Down Expand Up @@ -906,7 +906,7 @@ static int apply_patch(cJSON *object, const cJSON *patch, const cJSON_bool case_
if ((opcode == MOVE) || (opcode == COPY))
{
cJSON *from = get_object_item(patch, "from", case_sensitive);
if (!cJSON_IsString(from))
if (!cJSON_IsString(from) || (from->valuestring == NULL))
{
/* missing "from" for copy/move. */
status = 4;
Expand Down
55 changes: 55 additions & 0 deletions tests/misc_utils_tests.c
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Original file line number Diff line number Diff line change
Expand Up @@ -70,11 +70,66 @@ static void cjson_utils_functions_shouldnt_crash_with_null_pointers(void)
cJSON_Delete(item);
}

static void cjson_utils_apply_patches_should_reject_null_valuestring(void)
{
/* A cJSON_String item can have a NULL valuestring (e.g. when created with
* cJSON_CreateStringReference(NULL)). The JSON patch code checks the "op",
* "path" and "from" fields with cJSON_IsString() and then dereferences
* valuestring. Such patches must be rejected with an error code instead of
* crashing on the NULL valuestring. */

/* NULL "op" valuestring */
{
cJSON *object = cJSON_CreateObject();
cJSON *patches = cJSON_CreateArray();
cJSON *patch = cJSON_CreateObject();
cJSON_AddItemToObject(patch, "op", cJSON_CreateStringReference(NULL));
cJSON_AddItemToObject(patch, "path", cJSON_CreateString(""));
cJSON_AddItemToObject(patch, "value", cJSON_CreateNumber(1));
cJSON_AddItemToArray(patches, patch);
TEST_ASSERT_TRUE_MESSAGE(0 != cJSONUtils_ApplyPatches(object, patches), "NULL \"op\" valuestring should be rejected.");
TEST_ASSERT_TRUE_MESSAGE(0 != cJSONUtils_ApplyPatchesCaseSensitive(object, patches), "NULL \"op\" valuestring should be rejected.");
cJSON_Delete(object);
cJSON_Delete(patches);
}

/* NULL "path" valuestring */
{
cJSON *object = cJSON_CreateObject();
cJSON *patches = cJSON_CreateArray();
cJSON *patch = cJSON_CreateObject();
cJSON_AddItemToObject(patch, "op", cJSON_CreateString("remove"));
cJSON_AddItemToObject(patch, "path", cJSON_CreateStringReference(NULL));
cJSON_AddItemToArray(patches, patch);
TEST_ASSERT_TRUE_MESSAGE(0 != cJSONUtils_ApplyPatches(object, patches), "NULL \"path\" valuestring should be rejected.");
TEST_ASSERT_TRUE_MESSAGE(0 != cJSONUtils_ApplyPatchesCaseSensitive(object, patches), "NULL \"path\" valuestring should be rejected.");
cJSON_Delete(object);
cJSON_Delete(patches);
}

/* NULL "from" valuestring */
{
cJSON *object = cJSON_CreateObject();
cJSON *patches = cJSON_CreateArray();
cJSON *patch = cJSON_CreateObject();
cJSON_AddItemToObject(object, "a", cJSON_CreateNumber(1));
cJSON_AddItemToObject(patch, "op", cJSON_CreateString("move"));
cJSON_AddItemToObject(patch, "path", cJSON_CreateString("/b"));
cJSON_AddItemToObject(patch, "from", cJSON_CreateStringReference(NULL));
cJSON_AddItemToArray(patches, patch);
TEST_ASSERT_TRUE_MESSAGE(0 != cJSONUtils_ApplyPatches(object, patches), "NULL \"from\" valuestring should be rejected.");
TEST_ASSERT_TRUE_MESSAGE(0 != cJSONUtils_ApplyPatchesCaseSensitive(object, patches), "NULL \"from\" valuestring should be rejected.");
cJSON_Delete(object);
cJSON_Delete(patches);
}
}

int main(void)
{
UNITY_BEGIN();

RUN_TEST(cjson_utils_functions_shouldnt_crash_with_null_pointers);
RUN_TEST(cjson_utils_apply_patches_should_reject_null_valuestring);

return UNITY_END();
}