Tool: added VM Test

- includes a tiny demo for decoding secret messages

lib/include/lvm.h

@@ -4,7 +4,9 @@
 /* Laika VM:
         This is an obfuscation technique where vital code can be executed in a
     stack-based VM, inlined into the function. The VM instruction-set is fairly
-    simple, see the OP_* for avaliable opcodes and their expected arguments.
+    simple, see the OP_* enum for avaliable opcodes and their expected arguments.
+    The VM is turing-complete, however the instruction-set has been curated to 
+    fit this specific use case.
 */
 
 #include <inttypes.h>
@@ -44,8 +46,9 @@ enum {
     OP_EXIT,
     OP_LOADCONST, /* stk_indx[uint8_t] = const_indx[uint8_t] */
     OP_PUSHLIT, /* stk_indx[uint8_t].i = uint8_t */
-    OP_READ, /* stk_indx[uint8_t] = *(int8_t*)stk_indx[uint8_t] */
-    OP_WRITE, /* *(uint8_t*)stk_indx[uint8_t] = stk_indx[uint8_t] */
+    OP_READ, /* stk_indx[uint8_t].i = *(int8_t*)stk_indx[uint8_t] */
+    OP_WRITE, /* *(uint8_t*)stk_indx[uint8_t].ptr = stk_indx[uint8_t].i */
+    OP_INCPTR, /* stk_indx[uint8_t].ptr++ */
 
     /* arithmetic */
     OP_ADD, /* stk_indx[uint8_t] = stk_indx[uint8_t] + stk_indx[uint8_t] */
@@ -102,6 +105,11 @@ LAIKA_FORCEINLINE void laikaV_execute(struct sLaikaV_vm *vm) {
                 *(uint8_t*)vm->stack[ptr].ptr = vm->stack[indx].i;
                 break;
             }
+            case OP_INCPTR: {
+                uint8_t ptr = READBYTE;
+                vm->stack[ptr].ptr++;
+                break;
+            }
             case OP_ADD: BINOP(+);
             case OP_SUB: BINOP(-);
             case OP_MUL: BINOP(*);

tools/CMakeLists.txt

@@ -1,3 +1,4 @@
 cmake_minimum_required(VERSION 3.10)
 
 add_subdirectory(genkey)
+add_subdirectory(vmtest)

tools/vmtest/CMakeLists.txt

@@ -0,0 +1,14 @@
+cmake_minimum_required(VERSION 3.10)
+
+project(vmTest VERSION 1.0)
+
+# Put CMake targets (ALL_BUILD/ZERO_CHECK) into a folder
+set_property(GLOBAL PROPERTY USE_FOLDERS ON)
+
+# compile vmTest
+file(GLOB_RECURSE VMTESTSOURCE ${CMAKE_CURRENT_SOURCE_DIR}/src/**.c)
+add_executable(vmTest ${VMTESTSOURCE})
+target_link_libraries(vmTest PUBLIC LaikaLib)
+
+# add the 'DEBUG' preprocessor definition if we're compiling as Debug
+target_compile_definitions(vmTest PUBLIC "$<$<CONFIG:Debug>:DEBUG>")

tools/vmtest/src/main.c

@@ -0,0 +1,46 @@
+#include <stdio.h>
+#include <string.h>
+
+#include "lvm.h"
+#include "lbox.h"
+
+/* VM BOX Demo:
+    A secret message has been xor'd, this tiny bytecode chunk decodes 'data' into 
+    'unlockedData'. Obviously you wouldn't want a key this simple, more obfuscation
+    would be good (byte swapping, revolving xor key, etc.)
+*/ 
+
+int main(int argv, char **argc) {
+    uint8_t data[] = {
+        0x96, 0xBB, 0xB2, 0xB2, 0xB1, 0xFE, 0x89, 0xB1,
+        0xAC, 0xB2, 0xBA, 0xFF, 0xDE, 0x20, 0xEA, 0xBA, 
+        0xCE, 0xEA, 0xFC, 0x01, 0x9C, 0x23, 0x4D, 0xEE
+    };
+
+    struct sLaikaB_box box = {
+        {0}, /* reserved */
+        { /* stack layout:
+                [0] - unlockedData (ptr)
+                [1] - data (ptr)
+                [2] - key (uint8_t)
+                [3] - working data (uint8_t)
+         */
+            LAIKA_MAKE_VM_IAB(OP_LOADCONST, 0, 0),
+            LAIKA_MAKE_VM_IAB(OP_LOADCONST, 1, 1),
+            LAIKA_MAKE_VM_IAB(OP_PUSHLIT, 2, 0xDE),
+            /* LOOP_START */
+            LAIKA_MAKE_VM_IAB(OP_READ, 3, 1), /* load data into working data */
+            LAIKA_MAKE_VM_IABC(OP_XOR, 3, 3, 2), /* xor data with key */
+            LAIKA_MAKE_VM_IAB(OP_WRITE, 0, 3), /* write data to unlockedData */
+            LAIKA_MAKE_VM_IA(OP_INCPTR, 0),
+            LAIKA_MAKE_VM_IA(OP_INCPTR, 1),
+            LAIKA_MAKE_VM_IAB(OP_TESTJMP, 3, -17), /* exit loop on null terminator */
+            OP_EXIT
+        }
+    };
+
+    laikaB_unlock(&box, data);
+    printf("%s\n", box.unlockedData);
+    laikaB_lock(&box);
+    return 0;
+}