RC4 KSA per shuffling opcodes

assembler/assembler.py

@@ -56,7 +56,7 @@ class VMAssembler:
 
     def __init__(self, key):
         self.assembled_code = bytearray()
-        self.define_ops(key)
+        self.encrypt_ops(key)
 
     def parse(self, instruction):
         action = getattr(self, "{}".format(instruction.opcode.method))
@@ -179,15 +179,20 @@ class VMAssembler:
         self.assembled_code += opcode.uint8()
         return
 
-    def define_ops(self, key):
+    def encrypt_ops(self, key):
         key_ba = bytearray(key, 'utf-8')
         olds = copy.deepcopy(ops)
-        for b in key_ba:
-            for op_com in ops:
-                op_com.set_value(rol(b ^ op_com.value, b % 8, 8))
-        for i in ops:
-            for j in ops:
-                j.set_value(rol(j.value, i.value % 8, 8))
+        
+        # RC4 KSA! :-P
+        arr = [i for i in range(256)]
+        j = 0
+        for i in range(len(arr)):
+            j = (j + arr[i] + key_ba[i % len(key)]) % len(arr)
+            arr[i], arr[j] = arr[j], arr[i]
+        
+        for i, o in enumerate(ops):
+            o.set_value(arr[i])
+            
         for o, n in zip(olds, ops):
             print("{} : {}->{}".format(o.name, hex(o.value), hex(n.value)))
 

vm/vm.cpp

@@ -9,18 +9,26 @@ unsigned rol(unsigned x, int L, int N) {
   return (x << L) | (lsbs >> (N - L));
 }
 
-void VM::defineOpcodes(uint8_t *key) {
-  uint32_t i, j, keysize;
+void VM::encryptOpcodes(uint8_t *key) {
+  uint8_t arr[256];
+  uint32_t i, j, tmp, keysize;
   keysize = strlen((char *)key);
-  for (i = 0; i < keysize; i++) {
-    for (j = 0; j < NUM_OPS; j++) {
-      OPS[j] = rol(key[i] ^ OPS[j], key[i] % 8, 8);
+
+  /*
+  RC4 KSA! :-D
+  */
+  for (i = 0; i < 256; i++) {
+    arr[i] = i;
   }
+  j = 0;
+  for (i = 0; i < 256; i++) {
+    j = (j + arr[i] + key[i % keysize]) % 256;
+    tmp = arr[i];
+    arr[i] = arr[j];
+    arr[j] = tmp;
   }
   for (i = 0; i < NUM_OPS; i++) {
-    for (j = 0; j < NUM_OPS; j++) {
-      OPS[j] = rol(OPS[j], OPS[i] % 8, 8);
-    }
+    OPS[i] = arr[i];
   }
 #ifdef DBG
   //#TODO ASSEGNARE I NOMI AGLI OPCODES
@@ -135,7 +143,7 @@ VM::VM(uint8_t *key) {
   DBG_SUCC(("Creating VM without code.\n"));
   as.allocate();
   initVariables();
-  defineOpcodes(key);
+  encryptOpcodes(key);
 }
 
 VM::VM(uint8_t *key, uint8_t *code, uint32_t codesize) {
@@ -144,7 +152,7 @@ VM::VM(uint8_t *key, uint8_t *code, uint32_t codesize) {
     as.insCode(code, codesize);
   }
   initVariables();
-  defineOpcodes(key);
+  encryptOpcodes(key);
 }
 
 void VM::initVariables(void) {

vm/vm.h

@@ -23,7 +23,7 @@ private:
   // FUNCTIONS
   ///////////////////////
   void initVariables(void);
-  void defineOpcodes(uint8_t *key);
+  void encryptOpcodes(uint8_t *key);
   /*
   DBG UTILS
   */