Proper size and initialisation for array data

src/http.c

@@ -639,7 +639,28 @@ int auth_log_in(struct tunnel *tunnel)
 	char portal[64] = { '\0' };
 	char magic[32] = {'\0' };
 	char peer[32]  = { '\0' };
-	char data[9 + 3 * USERNAME_SIZE + 12 + 3 * PASSWORD_SIZE + 7 + 3 * REALM_SIZE + 7 + 1];
+#define OFV_MAX(a, b) ((a) > (b) ? a : b)
+	char data[OFV_MAX(
+	                  // username=USERNAME&realm=REALM&ajax=1&redir=%%2Fremote%%2Findex&just_logged_in=1
+	                  (
+	                          sizeof("username=") +
+	                          3 * USERNAME_SIZE +
+	                          sizeof("realm=") +
+	                          3 * REALM_SIZE +
+	                          sizeof("ajax=1&redir=%%2Fremote%%2Findex&just_logged_in=1")
+	                  ),
+	                  // "username=USERNAME&credential=PASSWORD&realm=REALM&ajax=1
+	                  (
+	                          sizeof("username=") +
+	                          3 * USERNAME_SIZE +
+	                          sizeof("realm=") +
+	                          3 * REALM_SIZE +
+	                          sizeof("credential=") +
+	                          3 * PASSWORD_SIZE +
+	                          sizeof("ajax=1")
+	                  )
+	          )] = { '\0' };
+#undef OFV_MAX
 	char token[128], tokenresponse[256], tokenparams[320];
 	char action_url[1024] = { '\0' };
 	char *res = NULL;
@@ -651,7 +672,6 @@ int auth_log_in(struct tunnel *tunnel)
 	tunnel->cookie[0] = '\0';
 
 	if (username[0] == '\0' && tunnel->config->password[0] == '\0') {
-		snprintf(data, sizeof(data), "");
 		ret = http_request(tunnel, "GET", "/remote/login",
 		                   data, &res, &response_size);
 	} else {