Cambiata key

This reverts commit 0ac0e08c9e.

INSTRUCTION_SET.md

@@ -1,333 +0,0 @@
-# Architecture
-
-Pasticciotto uses the Harvard Architecture meaning its code is separated from its data and also from its stack. This allowed me to materialize my idea for the **PoliCTF** challenge: I could run the code the partecipants assembled without any hassle!
-![Structure]
-
-There are 8 general purpose registers (`R0` to `S3`) with `S0 -> S3` being "scratch" ones. There is a `RP` register (Return Pointer) and obviously the `IP` (Instruction Pointer).
-
-# Opcode encryption
-
-The VM needs a decryption key to run: the opcodes are "encrypted" with the key by the assembler. The encryption algorithm is the `RC4` key scheduling shuffle. Once the values are shuffled, the `opcodes` are assigned according to their definition order.
-
-```python
-key_ba = bytearray(key, 'utf-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])
-```
-
-# Instruction set
-The instruction set I come out wants to be "RISC"-oriented but I have to admit that it is more "CISC"-oriented *(Confusing Instruction Set Computer)*.
-Also, since I decided that every instruction had to be 4 chars long, some name adaptation may have encountered some quality issue... (yes, `POP`, I'm looking at you)
-
-**The syntax used is the Intel one!**
-
-There **three types** of instructions:
-1. with 2 operands (*imm2reg*, *reg2imm*, *byt2reg*, *reg2reg*)
-2. with 1 operand
-3. with no operand at all (*single*)
-
-![Instruction]
-## MOVI
-```
-Full name: MOVe Immediate to register
-Usage: MOVI R0, 0x00
-Effect: R0 contains the value 0x00
-```
-## MOVR
-```
-Full name: MOVe Register to register
-Usage: MOVR R1, R0
-Effect: R0 is copied into R1
-```
-## LODI
-```
-Full name: LOaD Immediate offset @ data section to register
-Usage: LODI R0, 0x0
-Effect: R0 contains data[0x0]
-```
-## LODR
-```
-Full name: LOaD offset in Register @ data section to register
-Usage: LODR R1, R0
-Effect: R1 contains data[R1]
-```
-## STRI
-```
-Full name: SToRe @ immediate offset in data section from register
-Usage: STRI 0x0, R0
-Effect: data[0x0] contains R0
-```
-## STRR
-```
-Full name: SToRe @ offset of Register in data section from register
-Usage: STRR R1, R0
-Effect: data[R1] contains R0
-```
-## ADDI
-```
-Full name: ADD Immediate to register
-Usage: ADDI R0, 0x1
-Effect: R0 is incremented by 0x1
-```
-## ADDR
-```
-Full name: ADD Register to register
-Usage: ADDR R1, R0
-Effect: R1 is incremented by R0
-```
-## SUBI
-```
-Full name: SUBstract Immediate from register
-Usage: SUBI R0, 0x1
-Effect: R0 is decremented by 0x1
-```
-## SUBR
-```
-Full name: SUBstract Register from register
-Usage: SUBR R1, R0
-Effect: R1 is decremented by R0
-```
-## ANDB
-```
-Full name:
-Usage:
-Effect: 
-```
-## ANDW
-```
-Full name:
-Usage:
-Effect: 
-```
-## ANDR
-```
-Full name:
-Usage:
-Effect: 
-```
-## YORB
-```
-Full name:
-Usage:
-Effect: 
-```
-## YORW
-```
-Full name:
-Usage:
-Effect: 
-```
-## YORR
-```
-Full name:
-Usage:
-Effect: 
-```
-## XORB
-```
-Full name:
-Usage:
-Effect: 
-```
-## XORW
-```
-Full name:
-Usage:
-Effect: 
-```
-## XORR
-```
-Full name:
-Usage:
-Effect: 
-```
-## NOTR
-```
-Full name:
-Usage:
-Effect: 
-```
-## MULI
-```
-Full name:
-Usage:
-Effect: 
-```
-## MULR
-```
-Full name:
-Usage:
-Effect: 
-```
-## DIVI
-```
-Full name:
-Usage:
-Effect: 
-```
-## DIVR
-```
-Full name:
-Usage:
-Effect: 
-```
-## SHLI
-```
-Full name:
-Usage:
-Effect: 
-```
-## SHLR
-```
-Full name:
-Usage:
-Effect: 
-```
-## SHRI
-```
-Full name:
-Usage:
-Effect: 
-```
-## SHRR
-```
-Full name:
-Usage:
-Effect: 
-```
-## PUSH
-```
-Full name:
-Usage:
-Effect: 
-```
-## POOP
-```
-Full name:
-Usage:
-Effect: 
-```
-## CMPB
-```
-Full name:
-Usage:
-Effect: 
-```
-## CMPW
-```
-Full name:
-Usage:
-Effect: 
-```
-## CMPR
-```
-Full name:
-Usage:
-Effect: 
-```
-## JMPI
-```
-Full name: JuMP to Immediate
-Usage: JMPI 0x00
-Effect: Unconditional jump to 0x00
-```
-## JMPR
-```
-Full name: JuMP to Register
-Usage: JMPR R0
-Effect: Unconditional jump to R0
-```
-## JPAI
-```
-Full name: JumP if Above to Immediate
-Usage: JPAI 0x00
-Effect: Jumps to code[0x00] according to last comparison
-```
-## JPAR
-```
-Full name: JumP if Above to Register
-Usage: JPAR R0
-Effect: Jumps to code[R0] according to last comparison
-```
-## JPBI
-```
-Full name: JumP if Below or equal to Immediate
-Usage: JPBI 0x00
-Effect: Jumps to code[0x00] according to last comparison
-```
-## JPBR
-```
-Full name: JumP if Below or equal to Register
-Usage: JPBR R0
-Effect: Jumps to code[R0] according to last comparison
-```
-## JPEI
-```
-Full name: JumP if Equal to Immediate
-Usage: JPEI 0x00
-Effect: Jumps to code[0x00] according to last comparison
-```
-## JPER
-```
-Full name: JumP if Equal to Register
-Usage: JPER R0
-Effect: Jumps to code[R0] according to last comparison
-```
-## JPNI
-```
-Full name: JumP if Not equal to Immediate
-Usage: JPNI 0x00
-Effect: Jumps to code[0x00] according to last comparison
-```
-## JPNR
-```
-Full name: JumP if Not equal to Register
-Usage: JPNR R0
-Effect: Jumps to code[R0] according to last comparison
-```
-## CALL
-```
-Full name: CALL function
-Usage: CALL *function*
-Effect: Saves the next instruction address into RP and jumps to the start of the function
-```
-## RETN
-```
-Full name: RETurN
-Usage: RETN
-Effect: Restores the RP into the IP and jumps to the IP 
-```
-## SHIT
-```
-Full name: Well...
-Usage: SHIT
-Effect: Halts the execution
-```
-## NOPE
-```
-Full name: NOP(e)
-Usage: NOPE
-Effect: Does nothing for an instruction
-```
-## GRMN
-```
-Full name: GeRMaNo
-Usage: GRMN
-Effect: Sets every register (excluding IP and RP) to GG
-```
-## DEBG
-```
-Full name: DEBuG
-Usage: DEBG
-Effect: Prints the status of every register and the flags
-```
-
-[Instruction]: ./res/instruction.png
-[Structure]: ./res/structure.png

README.md

@@ -1,47 +1 @@
-![Pasticciotto]
+VM con ISA diversi e bytecode generati casualmente.
-
-# What is this?
-Pasticciotto is a virtual machine which can be used to obfuscate code. It was developed for the **PoliCTF 17** as a reversing challenge.
-
-I wanted to experiment with VM obfuscation since it was a topic that caught my attention while reversing challenges for various CTFs. So, I decided to write one **from scratch** in order to understand better how instruction set architectures are implemented! 
-
-The design and the implementation behind Pasticciotto are not state-of-the-art but hey, it works!
-
-# What about the challenge?
-I do not want to spoil the challenge for those that haven't completed it yet. Check out some write-up online!
-
-# Instruction set
-Check out the file [INSTRUCTION_SET.MD](IS) to understand how the VM works and which operations it can do! Watch out for some spoilers if you haven't completed the challenge though!
-
-# Why "Pasticciotto"?
-In Italian, "Pasticciotto" has two meanings! 
-
-The first one is **"little mess"** which perfectly describes how I put up this project. The second one is a typical dessert from Southern Italy, Salento! It's filled with cream! Yum!
-
-# Contributions
-
-Any contribution is **very** welcome! Feel free to open issues and pull requests!
-
-
-# License
-```
-Copyright 2017 Giulio De Pasquale
-
-Permission is hereby granted, free of charge, to any person obtaining a copy of this 
-software and associated documentation files (the "Software"), to deal in the Software 
-without restriction, including without limitation the rights to use, copy, modify, merge, 
-publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons 
-to whom the Software is furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all copies or 
-substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
-INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR 
-PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE 
-FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR 
-OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
-DEALINGS IN THE SOFTWARE.
-```
-[Pasticciotto]: ./res/pasticciotto.png
-[IS]: ./INSTRUCTION_SET.md

assembler/assembler.py

@@ -55,7 +55,7 @@ class VMAssembler:
         self.data = data
         self.assembled_code = bytearray()
         self.functions = []
-        self.encrypt_ops(key)
+        self.decrypt_ops(key)
         self.parse_functions()
         self.resolve_functions_offsets()
         self.resolve_symbols()
@@ -252,7 +252,7 @@ class VMAssembler:
         self.assembled_code += opcode.uint8()
         return
 
-    def encrypt_ops(self, key):
+    def decrypt_ops(self, key):
         key_ba = bytearray(key, 'utf-8')
         olds = copy.deepcopy(ops)
 

polictf/pasticciotto_server.cpp

@@ -1,81 +0,0 @@
-#include "../vm/vm.h"
-#include "../vm/debug.h"
-#include <fstream>
-#include <iostream>
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <time.h>
-#include <unistd.h>
-
-#define KEYLEN 15
-#define CODESIZE 0x300
-#define DATAKEYLEN 30
-
-void gen_random(uint8_t *s, const int len) {
-  srand(time(NULL));
-  static const char alphanum[] = "0123456789"
-                                 "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-                                 "abcdefghijklmnopqrstuvwxyz";
-  for (int i = 0; i < len; ++i) {
-    s[i] = alphanum[rand() % (sizeof(alphanum) - 1)];
-  }
-
-  s[len] = 0;
-}
-
-unsigned char encrypted_data[] = {
-    0xcc, 0x8d, 0x5a, 0xcc, 0x73, 0xb5, 0xf2, 0xa3, 0xf3, 0x92,
-    0xa8, 0x8f, 0x2f, 0xf1, 0x3e, 0xf4, 0x69, 0x00, 0x4a, 0xcb,
-    0xed, 0xc4, 0x57, 0x9b, 0xf6, 0x9a, 0x78, 0x46, 0x83, 0xe9};
-unsigned int encrypted_data_len = 30;
-
-int main(int argc, char *argv[]) {
-  uint8_t *key = new uint8_t[KEYLEN], *decdatasec = new uint8_t[DATAKEYLEN],
-          *flag = new uint8_t[DATAKEYLEN];
-  uint8_t *clientcode;
-  uint8_t i;
-  uint32_t clientcodesize, bytesread;
-  FILE *datap, *flagp;
-
-  gen_random(key, KEYLEN);
-  printf("Use this: \"%s\"\n", key);
-  printf("How much data are you sending me?\n");
-  scanf("%d", &clientcodesize);
-  printf("Go ahead then!\n");
-  clientcode = new uint8_t[clientcodesize];
-  bytesread = read(0, clientcode, clientcodesize);
-  if (bytesread != clientcodesize) {
-    printf("ERROR! Couldn't read everything!\n");
-    exit(1);
-  }
-  VM vm(key, clientcode, clientcodesize);
-  vm.as.insData(encrypted_data, encrypted_data_len);
-  vm.run();
-
-  datap = fopen("./res/decrypteddatasection.txt", "r");
-  if (datap == NULL) {
-      printf("Couldn't open decrypteddatasection.txt!\n");
-      exit(1);
-  }
-  fscanf(datap, "%s", decdatasec);
-  fclose(datap);
-
-  for (i = 0; i < DATAKEYLEN; i++) {
-    if (vm.as.data[i] != decdatasec[i]) {
-        DBG_INFO(("Checking data[%d]..\n", i));
-      printf("Nope!\n");
-      exit(1);
-    }
-  }
-
-  flagp = fopen("./res/flag.txt", "r");
-  if (flagp == NULL) {
-      printf("Couldn't open flag.txt!\n");
-      exit(1);
-  }
-  fscanf(flagp, "%s", flag);
-  fclose(flagp);
-  printf("Congratulations!\nThe flag is: %s\n", flag);
-  return 0;
-}

polictf/res/decrypteddatasection.txt

@@ -1 +0,0 @@
-TheDataSectionHasBeenEncrypted

polictf/res/flag.txt

@@ -1 +0,0 @@
-PoliCTF17{DajeFunziona}

test/tea-encrypt.c

@@ -11,15 +11,15 @@ void encrypt(uint16_t *v) {
   uint16_t k1 = 0x7065; // "pe"
   uint16_t k2 = 0x7275; // "ru"
   uint16_t k3 = 0x6e73; // "ns"
-  // printf("v0: 0x%x, v1: 0x%x\n", v0, v1);
+  printf("v0: 0x%x, v1: 0x%x\n", v0, v1);
   for (i = 0; i < 128; i++) {
     sum += delta;
     v0 += ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
     v1 += ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
-    // printf("Intermediate v0: 0x%x | v1: 0x%x\n", v0, v1);
+    //printf("Intermediate v0: 0x%x | v1: 0x%x\n", v0, v1);
   }
-  // printf("SUM: 0x%x\n", sum);
+  printf("SUM: 0x%x\n", sum);
-  // printf("v0: 0x%x, v1: 0x%x\n", v0, v1);
+  printf("v0: 0x%x, v1: 0x%x\n", v0, v1);
   v[0] = v0;
   v[1] = v1;
 }
@@ -35,10 +35,13 @@ int main(int argc, char *argv[]) {
   buf = (uint8_t *)malloc(buflen);
   memcpy(buf, argv[1], buflen);
   for (i = 0; i < buflen; i++) {
+    printf("----\n");
     encrypt((uint16_t *)&buf[i]);
   }
+  printf("Result:\n");
   for (i = 0; i < buflen; i++) {
-    printf("%c", buf[i]);
+    printf("%02x", buf[i]);
   }
+  printf("\n");
   return 0;
 }

vm/vm.h

@@ -18,6 +18,7 @@ private:
   uint16_t regs[0xb];
   flags_t flags;
 
+  VMAddrSpace as;
   ////////////////////////
   // FUNCTIONS
   ///////////////////////
@@ -81,7 +82,6 @@ private:
 public:
   VM(uint8_t *key);
   VM(uint8_t *key, uint8_t *code, uint32_t codesize);
-  VMAddrSpace as;
   void status(void);
   void run();
 };