From 8423d2407237598ad640e9a87f00ab414e1d17a4 Mon Sep 17 00:00:00 2001
From: vms <michail.vms@gmail.com>
Date: Wed, 21 Aug 2019 14:28:50 +0200
Subject: [PATCH] add some hardering

---
 backend-c/src/main.c  | 22 ++++++++++++++++++----
 backend-c/src/model.c |  9 +++++++++
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/backend-c/src/main.c b/backend-c/src/main.c
index 331009c..2eb9464 100644
--- a/backend-c/src/main.c
+++ b/backend-c/src/main.c
@@ -12,7 +12,15 @@ const char *fetch_posts_request(const json_t *json);
 
 bool isInited = 0;
 
-const char *invoke(char *str, int length) {
+/**
+ * Executes given request and returns result in as a pointer to the following structure:
+ * | result size (4 bytes, le)| result (size bytes) |.
+ *
+ * @param request a pointer to the supplied request in JSON format
+ * @param request_size a size of the supplied sql request
+ * @return a pointer to the struct contains result_size and result
+ */
+ const char *invoke(char *request, int request_size) {
     // initialize SQLite by creating schema
     if(0 == isInited) {
         create_scheme();
@@ -23,7 +31,7 @@ const char *invoke(char *str, int length) {
     const unsigned int pool_size = sizeof pool / sizeof *pool;
 
     // try to parse json and extract action field
-    const json_t *json = json_create(str, pool, pool_size);
+    const json_t *json = json_create(request, pool, pool_size);
     if(!json) {
         const char error[] = "Mailformed json given";
         return prepare_response(error, sizeof error);
@@ -49,8 +57,11 @@ const char *invoke(char *str, int length) {
     } else if(0 == strcmp(action, "Fetch")) {
         result = fetch_posts_request(json);
     } else {
-        // no suitable action given
-        char *error = (char *)malloc(1024);
+        // no suitable action is given
+        char *error = malloc(1024);
+        if(0 == error) {
+            return 0;
+        }
         const int error_size = snprintf(error, 1024, "%s given as the action field, but only `Post` and `Fetch` are supported", action);
         result = prepare_response(error, error_size);
         free(error);
@@ -139,6 +150,9 @@ const char *fetch_posts_request(const json_t *json) {
 
     const int result_len = strlen(result) + 100;
     char *result_out = malloc(result_len);
+    if(0 == result_out) {
+        return 0;
+    }
 
     const int result_out_len = snprintf(result_out, result_len, "{ posts: \"%s\" }", result);
 
diff --git a/backend-c/src/model.c b/backend-c/src/model.c
index cfcea26..6308be0 100644
--- a/backend-c/src/model.c
+++ b/backend-c/src/model.c
@@ -17,6 +17,9 @@ char *add_post(const char *username, int username_length, const char *message, i
     // at now wasm-ld has 1024 bytes for stack permission by default - that why dynamic allocation here
     const int request_size = username_length + message_length + 50;
     char *add_sql = (char *)malloc(request_size);
+    if(0 == add_sql) {
+        return 0;
+    }
 
     const int add_sql_length = snprintf(add_sql, request_size, "INSERT INTO messages VALUES(\"%s\", \"%s\")", message, username);
     if(add_sql_length < 0) {
@@ -29,6 +32,9 @@ char *add_post(const char *username, int username_length, const char *message, i
 char *get_all_posts(int offset, int count) {
     // at now wasm-ld has 1024 bytes for stack permission by default - that why dynamic allocation here
     char *get_sql = (char *)malloc(256);
+    if(0 == get_sql) {
+        return 0;
+    }
 
     const int get_sql_length = snprintf(get_sql, 256,
             "SELECT json_group_array("
@@ -47,6 +53,9 @@ char *get_posts_by_username(const char *username, int username_length, int offse
     // at now wasm-ld has 1024 bytes for stack permission by default - that why dynamic allocation here
     const int request_size = username_length + 300;
     char *get_sql = (char *)malloc(request_size);
+    if(0 == get_sql) {
+        return 0;
+    }
 
     const int add_sql_length = snprintf(get_sql, request_size,
             "SELECT json_group_array("