solved 1

4/level2/flag.txt

@@ -0,0 +1 @@
+hacklab{thanks_mario_but_the_flag_is_on_another_server}

4/level2/level2.c

@@ -0,0 +1,22 @@
+// gcc -o level2 -no-pie -fno-stack-protector level2.c
+#include <stdio.h>
+#include <unistd.h>
+
+void win() {
+  char *argv[2];
+  argv[0] = "/bin/sh";
+  argv[1] = NULL;
+  execve(argv[0], argv, NULL);
+}
+
+int main(int argc, char **argv) {
+  // Disable output buffering. Not part of the challenge.
+  setvbuf(stdout, NULL, _IONBF, 0);
+  setvbuf(stdin, NULL, _IONBF, 0);
+
+  char buffer[32];
+  puts("What do you want to talk about?");
+  fgets(buffer, 320, stdin);
+  puts("Bye.");
+  return 0;
+}