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Can anyone help me with decrypting an XML file?

  • 24-09-2010 11:02am
    #1
    Atomic Pineapple
    Registered Users, Registered Users 2 Posts: 18,272 ✭✭✭✭


    I am trying to to download and decrypt an encrypted XML file.

    I have implemented the download part and have tested with an unencrypted file and it works fine.

    However I now need to be able to download an XML file that has been encrypted using AES and the key "XXXX"

    So I am only concerned with decryption as the encryption on the XML file is already done.

    Here is my code so far:
    public NodeList getXMLDoc(){
        URL url;
        NodeList nl = null;

        try{
            String xmlFeed = context.getString(R.string.xml_feed);
            try {
                url = new URL(xmlFeed);
                URLConnection urlConnection;
                urlConnection = url.openConnection();   
                HttpURLConnection httpConnection = (HttpURLConnection) urlConnection;   
                int responseCode = httpConnection.getResponseCode();

                if(responseCode == HttpURLConnection.HTTP_OK){

                    String bytes = toHex("XXXX");
                    SecretKeySpec skeySpec = new SecretKeySpec(toByte(bytes), "AES");
                    try {
                        c.init(Cipher.DECRYPT_MODE, skeySpec);
                        //c.doFinal();
                    } catch (InvalidKeyException e) {
                        e.printStackTrace();
                    }
                    InputStream in = httpConnection.getInputStream();
                    CipherInputStream cis = new CipherInputStream(in, c);
                    DocumentBuilderFactory dbf;
                    dbf = DocumentBuilderFactory.newInstance();
                    DocumentBuilder db = dbf.newDocumentBuilder();

                    Document dom = db.parse(cis);

                    Element docEle = dom.getDocumentElement();

                    nl = docEle.getElementsByTagName(TAG_CHAR);

                    }       
            }
            catch (MalformedURLException e) {

                e.printStackTrace();
            }
            catch (IOException e) {

                e.printStackTrace();
            } catch (ParserConfigurationException e) {

                e.printStackTrace();
            } catch (SAXException e) {

                e.printStackTrace();
            }
            }
            finally{

            }
        return nl;
    }
    At the minute I am trying to decrypt the whole file using CipherInputStream is this the correct approach?

    My code above gives me the following exception:
    WARN/System.err(5274): java.io.IOException: last block incomplete in decryption

    Is this a setup error or what might be causing this error?

    Are there any tutorials on how to decrypt an XML file in Android/Java?

    Am I going in the right direction as to how to decrypt the file or is my code completely wrong?
    Tagged:


Comments

  • #2
    Atomic Pineapple
    Registered Users, Registered Users 2 Posts: 18,272 ✭✭✭✭Atomic Pineapple


    Updated Code:
    public NodeList getRoutingDoc(){
        URL url;
        NodeList nl = null;

        try{
            String xmlFeed = context.getString(R.string.xml_feed) + IMEI + ".xml";
            try {
                url = new URL(xmlFeed);
                URLConnection urlConnection;
                urlConnection = url.openConnection();    
                HttpURLConnection httpConnection = (HttpURLConnection) urlConnection;    
                int responseCode = httpConnection.getResponseCode();

                if(responseCode == HttpURLConnection.HTTP_OK){
                    String bytes = toHex("XXXX");
                    Key skeySpec = new SecretKeySpec(toByte(bytes), "AES");

                    InputStream in = httpConnection.getInputStream();
                    System.out.println(toByte(bytes));
                    Cipher c = Cipher.getInstance("AES/CFB8/NoPadding");
                    c.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(toByte(bytes)));
                    CipherInputStream cis = new CipherInputStream(in, c);
                    cis.read(new byte[16]);
                    BufferedReader br = new BufferedReader(new InputStreamReader(cis));
                    System.out.println("Got message");
                    System.out.println(br.readLine());

                    DocumentBuilderFactory dbf;
                    dbf = DocumentBuilderFactory.newInstance();
                    DocumentBuilder db = dbf.newDocumentBuilder();

                    Document dom = db.parse(in);
                    //cis.close();
                    Element docEle = dom.getDocumentElement();

                    nl = docEle.getElementsByTagName(TAG_CHAR);

                    }        
            }
            catch (MalformedURLException e) {

                e.printStackTrace();
            }
            catch (IOException e) {

                e.printStackTrace();
            } catch (ParserConfigurationException e) {

                e.printStackTrace();
            } catch (SAXException e) {

                e.printStackTrace();
            } catch (InvalidKeyException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (InvalidAlgorithmParameterException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (NoSuchAlgorithmException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (NoSuchPaddingException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            }
            finally{

            }
        return nl;
    }



    I have updated my code to the latest version I have.

    I am now using the CipherInputStream properly I think and getting the file in but the System.out.println gives me the following output:
    INFO/System.out(7880): &#239;&#191;&#189;=k&#239;&#191;&#189;KV&#239;&#191;&#189;a&#239;&#191;&#189;&#239;&#191;&#189;_|F&#239;&#191;&#189;&#239;&#191;&#189;(# -&#239;&#191;&#189;&#209;.&#239;&#191;&#189;&#239;&#191;&#189;u&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;n&#239;&#191;&#189;|&#239;&#191;&#189;&#239;&#191;&#189;~&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;9&#239;&#191;&#189;<&#195;*&#239;&#191;&#189;|T&#239;&#191;&#189;&#239;&#191;&#189;sUW&#199;&#8240;&#239;&#191;&#189;9&#239;&#191;&#189;qeo&#239;&#191;&#189;M%&#239;&#191;&#189;t&#239;&#191;&#189;V&#239;&#191;&#189;V&#239;&#191;&#189;3Q"&#239;&#191;&#189;    T&#239;&#191;&#189;Yq?&#239;&#191;&#189;&#239;&#191;&#189;E&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;H%fo&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;M&#239;&#191;&#189;un&#239;&#191;&#189;&#239;&#191;&#189;-&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#200;&#8220;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;<d&#239;&#191;&#189;&#239;&#191;&#189;{&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;{&#239;&#191;&#189;!&#239;&#191;&#189;[&&#239;&#191;&#189;&#239;&#191;&#189;%&#239;&#191;&#189;&#239;&#191;&#189;M&#239;&#191;&#189;.&#239;&#191;&#189;jq+&#239;&#191;&#189;&#239;&#191;&#189;,&#239;&#191;&#189;b&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189; &#239;&#191;&#189;&#239;&#191;&#189;~&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;)&#239;&#191;&#189;&#239;&#191;&#189;*&#220;&#168;)&#239;&#191;&#189;&#239;&#191;&#189;>&#239;&#191;&#189;&#239;&#191;&#189;i&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;b&#239;&#191;&#189;_"&#239;&#191;&#189;&#239;&#191;&#189;F)&#239;&#191;&#189;`"&#239;&#191;&#189;

    So it looks as if its no decrypting it at all or not decrypting it properly??

    Can anyone see what I am doing wrong?


  • #3
    amen
    Registered Users, Registered Users 2 Posts: 2,781 ✭✭✭amen


    not a java head but are you trying to decrypt the file as you get stream/download it ?

    if so download and save first and the decrypt it.


  • #4
    Atomic Pineapple
    Registered Users, Registered Users 2 Posts: 18,272 ✭✭✭✭Atomic Pineapple


    amen wrote: »
    not a java head but are you trying to decrypt the file as you get stream/download it ?

    if so download and save first and the decrypt it.

    Thanks, I changed it so now I download the file first.

    Then run the following:
    Cipher c = Cipher.getInstance("AES/CFB8/NoPadding");
 c.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(toByte(bytes)));
CipherInputStream cis = new CipherInputStream(new FileInputStream(enc_File), c);
 cis.read(new byte[16]);
BufferedReader br = new BufferedReader(new InputStreamReader(cis));
 Log.d("XXXX", br.readLine());

    But it still doesn't seem to be decoding the file, my log prints out the same sort of junk as before:
    &#239;&#191;&#189;=k&#239;&#191;&#189;KV&#239;&#191;&#189;a&#239;&#191;&#189;&#239;&#191;&#189;_|F&#239;&#191;&#189;&#239;&#191;&#189;(# -&#239;&#191;&#189;&#209;.&#239;&#191;&#189;&#239;&#191;&#189;u&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;n&#239;&#191;&#189;|&#239;&#191;&#189;&#239;&#191;&#189;~&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;9&#239;&#191;&#189;<&#195;*&#239;&#191;&#189;|T&#239;&#191;&#189;&#239;&#191;&#189;sUW&#199;&#8240;&#239;&#191;&#189;9&#239;&#191;&#189;qeo&#239;&#191;&#189;M%&#239;&#191;&#189;t&#239;&#191;&#189;V&#239;&#191;&#189;V&#239;&#191;&#189;3Q"&#239;&#191;&#189;    T&#239;&#191;&#189;Yq?&#239;&#191;&#189;&#239;&#191;&#189;E&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;H%fo&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;M&#239;&#191;&#189;un&#239;&#191;&#189;&#239;&#191;&#189;-&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#200;&#8220;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;<d&#239;&#191;&#189;&#239;&#191;&#189;{&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;{&#239;&#191;&#189;!&#239;&#191;&#189;[&&#239;&#191;&#189;&#239;&#191;&#189;%&#239;&#191;&#189;&#239;&#191;&#189;M&#239;&#191;&#189;.&#239;&#191;&#189;jq+&#239;&#191;&#189;&#239;&#191;&#189;,&#239;&#191;&#189;b&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189; &#239;&#191;&#189;&#239;&#191;&#189;~&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;)&#239;&#191;&#189;&#239;&#191;&#189;*&#220;&#168;)&#239;&#191;&#189;&#239;&#191;&#189;>&#239;&#191;&#189;&#239;&#191;&#189;i&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;b&#239;&#191;&#189;_"&#239;&#191;&#189;&#239;&#191;&#189;F)&#239;&#191;&#189;`"&#239;&#191;&#189;


  • #5
    Atomic Pineapple
    Registered Users, Registered Users 2 Posts: 18,272 ✭✭✭✭Atomic Pineapple


    Another update:

    I have changed the code to test encryption first and then decryption so the code is now as follows:
    Cipher c = Cipher.getInstance("AES/CFB8/NoPadding");
	    				
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(keyFile));
oos.writeObject(skeySpec);
	    				
c.init(Cipher.ENCRYPT_MODE, skeySpec);
CipherOutputStream cos = new CipherOutputStream(new FileOutputStream(testFile), c);
PrintWriter pw = new PrintWriter(new OutputStreamWriter(cos));
pw.println("Stand and unfold yourself");
pw.close();
oos.writeObject(c.getIV());
oos.close(); 

c.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(toByte(bytes)));
CipherInputStream cis = new CipherInputStream(new FileInputStream(testFile), c);
Log.d("XXXX", br.readLine());

    This log now prints out the following:
    DEBUG/(13642): &#239;&#191;&#189;l&#239;&#191;&#189;&#197;&#8364;&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189;&#213;*(&#239;&#191;&#189;&#239;&#191;&#189;&#239;&#191;&#189; yourself

    So it looks like its decoding the last part of it but not the rest?

    Any ideas?


  • #6
    jmcc
    Registered Users, Registered Users 2 Posts: 7,521 ✭✭✭jmcc


    How is the file being saved? Could there be an issue with how the webserver serves the file (binary rather than text)? What is apparently decrypted is sufficiently non-random enough to look like an xml file that's been improperly encoded initially. The word 'yourself' is also 8 characters. Is there a chance that you have a short read situation where only some of the input data is being read and processed? I don't know Java well enough to debug the code but look at how the initial data is encrypted (padding etc).

    Regards...jmcc


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