Foundations of Cyber Security II

Update to the binary of Exercise 06

Geschrieben am 24.05.2019 15:39 von Jonas Bushart

We were informed of a problem with the exercise 06. The problem manifest itself in receiving fewer bytes then send to the server by the client.

The problem happens if the uplink connection of the client is not quick enough and not all the data arrives at the same time. Then the server only reads and returns partial data. To fix the issue, we updated the binary to wait one second, to allow all data to be read at the same time.

--- a/exercises/exercise06/code/bufoverflow.c
+++ b/exercises/exercise06/code/bufoverflow.c
@@ -58,6 +58,7 @@ void echo_everyone() {

         if (pid == 0) { /* child */
             alarm(30);
+            sleep(1);
             echo_client(client_sock);
             shutdown(client_sock, SHUT_RDWR);
             close(client_sock);

The updated source code and binary can be downloaded from the Materials section.