From 8d679cab600ab3dd946856229296739859caf364 Mon Sep 17 00:00:00 2001
From: tsousa111 <tiagao2001@hotmail.com>
Date: Tue, 20 Feb 2024 19:31:56 +0000
Subject: [PATCH] Q1 e Q2 acabadas

Signed-off-by: tsousa111 <tiagao2001@hotmail.com>
---
 TPs/TP02/py/cfich_chacha20.py       | 49 +++++++++++++++++------------
 TPs/TP02/py/chacha20_int_attck.py   | 30 ++++++++++++++++++
 TPs/TP02/py/input.txt.enc.attck     |  1 +
 TPs/TP02/py/input.txt.enc.attck.dec |  1 +
 4 files changed, 61 insertions(+), 20 deletions(-)
 create mode 100755 TPs/TP02/py/chacha20_int_attck.py
 create mode 100644 TPs/TP02/py/input.txt.enc.attck
 create mode 100644 TPs/TP02/py/input.txt.enc.attck.dec

diff --git a/TPs/TP02/py/cfich_chacha20.py b/TPs/TP02/py/cfich_chacha20.py
index fc233bf..dde5418 100755
--- a/TPs/TP02/py/cfich_chacha20.py
+++ b/TPs/TP02/py/cfich_chacha20.py
@@ -3,6 +3,7 @@
 from cryptography.hazmat.primitives.ciphers import Cipher, algorithms
 import sys
 import os
+import argparse
 
 def setup(key_file):
     f = open(key_file,"wb")
@@ -31,7 +32,7 @@ def encrypt(input_file, key_file):
 
 def decrypt(input_file,key_file):
     fkey = open(key_file,"rb")
-    inp = open(f"{input_file}.enc","rb")
+    inp = open(f"{input_file}","rb")
     out = open(f"{input_file}.dec","wb")
 
     key = fkey.read()
@@ -50,33 +51,41 @@ def decrypt(input_file,key_file):
     out.close()
 
 def main():
-    args = sys.argv[1:]
-    if len(args) == 0:
-        sys.exit("Needs at least 2 arguments, use help.")
+    parser = argparse.ArgumentParser(
+        description="Program to perform operations using ChaCha20 cipher on files",
+    )
 
-    match args[0]:
+    subparsers = parser.add_subparsers(dest="operation", help="Operation to perform")
+
+    # Setup subcommand
+    setup_parser = subparsers.add_parser("setup", help="Setup a key file")
+    setup_parser.add_argument("fkey", help="File to contain the appropriate key for the ChaCha20 cipher")
+
+    # Encrypt subcommand
+    enc_parser = subparsers.add_parser("enc", help="Encrypt a file")
+    enc_parser.add_argument("fich", help="File to be encrypted")
+    enc_parser.add_argument("fkey", help="File containing the key for the ChaCha20 cipher")
+
+    # Decrypt subcommand
+    dec_parser = subparsers.add_parser("dec", help="Decrypt a file")
+    dec_parser.add_argument("fich", help="File to be decrypted")
+    dec_parser.add_argument("fkey", help="File containing the key for the ChaCha20 cipher")
+
+    args = parser.parse_args()
+    match args.operation:
         case "setup":
-            if len(args) != 2:
-                print("Number of arguments is incorrect for setup option")
-            key_file = args[1]
+            key_file = args.fkey
             setup(key_file)
         case "enc":
-            if len(args) != 3:
-                print("Number of arguments is incorrect for enc option")
-            input_file = args[1]
-            key_file = args[2]
+            input_file = args.fich
+            key_file = args.fkey
             encrypt(input_file,key_file)
         case "dec":
-            if len(args) != 3:
-                print("Number of arguments is incorrect for dec option")
-            input_file = args[1]
-            key_file = args[2]
+            input_file = args.fich
+            key_file = args.fkey
             decrypt(input_file,key_file)
-
         case "help":
-            print("skill issue")
-        case _:
-            print(f"{args[1]} is not an option, use help")
+            parser.print_help()
 
 if __name__ == "__main__":
     main()
diff --git a/TPs/TP02/py/chacha20_int_attck.py b/TPs/TP02/py/chacha20_int_attck.py
new file mode 100755
index 0000000..60ad33c
--- /dev/null
+++ b/TPs/TP02/py/chacha20_int_attck.py
@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+
+import sys
+
+def attack(fctxt, pos, plainAtPos, newPlainAtPos):
+    f = open(fctxt,"rb")
+    ciphertext = f.read()
+    f.close()
+
+    plainAtPos = plainAtPos.encode()
+    newPlainAtPos = newPlainAtPos.encode()
+    txt_len = len(plainAtPos)
+    diff = bytes([a ^ b for (a,b) in zip(plainAtPos,newPlainAtPos)])
+    cipher_diff = bytes([a ^ b for (a,b) in zip(diff,ciphertext[pos:pos+txt_len])])
+
+    new_ciphertext = ciphertext[:pos] + cipher_diff + ciphertext[pos+txt_len:]
+
+    with open(fctxt+".attck","wb") as f:
+        f.write(new_ciphertext)
+
+def main():
+    argv = sys.argv[1:]
+    argc = len(argv)
+    if argc < 3 or argc > 5:
+        sys.exit("Needs 4 arguments <fctxt> <pos> <ptxtAtPos> <newPtxtAtPos>")
+
+    attack(argv[0],int(argv[1]),argv[2],argv[3])
+
+if __name__ == "__main__":
+    main()
diff --git a/TPs/TP02/py/input.txt.enc.attck b/TPs/TP02/py/input.txt.enc.attck
new file mode 100644
index 0000000..be9036e
--- /dev/null
+++ b/TPs/TP02/py/input.txt.enc.attck
@@ -0,0 +1 @@
+�[n�"[v�շ�2S�.[n{V��#��쁻
\ No newline at end of file
diff --git a/TPs/TP02/py/input.txt.enc.attck.dec b/TPs/TP02/py/input.txt.enc.attck.dec
new file mode 100644
index 0000000..4059da1
--- /dev/null
+++ b/TPs/TP02/py/input.txt.enc.attck.dec
@@ -0,0 +1 @@
+vegan é fixe!!!