vPB2VP5t

1 public static void decrypt(File inputFile, final String outputFileName, User currentUser) throws IOException, NoSuchAlgorithmException, NoSuchProviderException, NoSuchPaddingException, InvalidKeyException, ShortBufferException, IllegalBlockSizeException,  ParserConfigurationException, SAXException, InvalidAlgorithmParameterException, BadPaddingException{
2        SecretKey sessionKey = null;
3        String algorithm, ciphermode;
4        int keySize, blockSize;
5        byte[] encryptedFile;
6        byte[] iv;
7        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
8        DocumentBuilder builder = factory.newDocumentBuilder();
9        Document doc = builder.parse(inputFile);
10        doc.getDocumentElement().normalize();
11        NodeList nList = doc.getElementsByTagName("User");
12        boolean userFound = false;
13        for (int i = 0; i < nList.getLength(); i++) {
14            if (nList.item(i).getFirstChild().getNextSibling().getTextContent().equals(currentUser.getName())){
15                sessionKey = decryptSessionKey(nList.item(i).getFirstChild().getNextSibling().getNextSibling().getNextSibling().getTextContent().getBytes(),currentUser.getPrivateKey());
16                userFound = true;
17                break;
18            }
19        }
20        if (!userFound){
21            sessionKey = generateSessionKey();
22        }
23        
24        algorithm = doc.getElementsByTagName("Algorithm").item(0).getTextContent();
25        keySize = Integer.parseInt(doc.getElementsByTagName("KeySize").item(0).getTextContent());
26        blockSize = Integer.parseInt(doc.getElementsByTagName("BlockSize").item(0).getTextContent());
27        ciphermode = doc.getElementsByTagName("CipherMode").item(0).getTextContent();
28        iv = Base64.getDecoder().decode(doc.getElementsByTagName("IV").item(0).getTextContent().getBytes());
29        encryptedFile = Base64.getDecoder().decode(doc.getElementsByTagName("Content").item(0).getTextContent().getBytes());
30        
31        //byte[] input = Files.readAllBytes(inputFile.toPath());
32        Cipher cipher = Cipher.getInstance(algorithm+"/"+ciphermode+"/PKCS5Padding");
33        
34        if (!"ECB".equals(ciphermode)){
35            IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
36            cipher.init(Cipher.DECRYPT_MODE, sessionKey, ivParameterSpec);
37        } else {
38            cipher.init(Cipher.DECRYPT_MODE, sessionKey);
39        } 
40        byte[] plainText = new byte[cipher.getOutputSize(blockSize)];
41        int ptLength = cipher.update(encryptedFile, 0, blockSize, plainText, 0);
42        try{
43            ptLength += cipher.doFinal(plainText, ptLength);   
44        } catch (BadPaddingException e){
45            return;
46        }
47        Files.write(new File(inputFile.toPath().getParent().toFile(),outputFileName).toPath(), plainText);
48        
49    }