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stev0
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File Decryption not working properly

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Wrote myself a small password management utility that is supposed to support encryption of a master password file. Everything seems to work fine, and no exceptions are thrown during the entire encrypt/decrypt operation. However upon trying to parse data from the resulting decryption, a Unexpected end of file has occurred. The following elements are not closed: Account. Line 6, position 10, exception is thrown.

When looking at the decrypted XML file in web browser, it only shows the first </Account> node, all other nodes did not make it out of the decryption process. I've attached the code segment below....where did I screw the pooch?


public partial class Form1 : Form
    {
        public string fileName = "passfile.xml";
        public DataSet ds = new DataSet("Account List");
        public DataTable accounts = new DataTable("Accounts");
        public Form1()
        {
            InitializeComponent();
            accountGroupsBox.Enabled = false;
            menuStrip1.Enabled = false;
            button2.Enabled = false;
            Types type = new Types();
            this.accountGroupsBox.Items.AddRange(type.accountTypes);
            accounts.Columns.AddRange(new DataColumn[] {
                new DataColumn("Username"),
                new DataColumn("Password"),
                new DataColumn("Description")});
         
            
            dataGridView1.DataSource = accounts;
            dataGridView1.Columns["Username"].FillWeight = 25;
            dataGridView1.Columns["Password"].FillWeight = 25;
            dataGridView1.Columns["Description"].FillWeight = 50;


        }

        private void addNewPasswordToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Form2 addAccount = new Form2(this);
            addAccount.Show();
        }

        private void S_Click(object sender, EventArgs e)
        {
            accountGroupsBox.Enabled = true;
            menuStrip1.Enabled = true;
            button2.Enabled = true;
            label2.Text = "Interface Unlocked";
        }

        private void accountGroupsBox_SelectedIndexChanged(object sender, EventArgs e)
        {
            accounts.Clear();
            try
            {
                XmlDocument doc = new XmlDocument();
                doc.Load(fileName);


                foreach (XmlNode node in doc.GetElementsByTagName("Account"))
                {
                    if (node["AccountType"].InnerText == accountGroupsBox.SelectedItem.ToString())
                    {
                        DataRow row = accounts.Rows.Add(
                        node["Username"].InnerText,
                        node["Password"].InnerText,
                        node["Description"].InnerText);
                    }
                }

            }
            catch (FileLoadException ex)
            {
                MessageBox.Show(ex.ToString(), "Error!", MessageBoxButtons.OK);
            }
        }
        public void Encrypt()
        {   
            string temp = Path.GetTempFileName();
            string path = System.IO.Path.GetDirectoryName(Application.ExecutablePath);
            byte[] pword = Encoding.UTF8.GetBytes(textBox1.Text);
            byte[] hash = SHA256.Create().ComputeHash(pword);
            byte[] iv = MD5.Create().ComputeHash(pword);
            byte[] key = hash;

            using(FileStream fsInput = new FileStream(fileName, FileMode.Open, FileAccess.Read))
            using(SymmetricAlgorithm alg = Aes.Create())
            using(ICryptoTransform enc = alg.CreateEncryptor(key, iv))
            using (FileStream fsOutput = new FileStream(temp, FileMode.Create, FileAccess.Write))
            using (CryptoStream cs = new CryptoStream(fsOutput, enc, CryptoStreamMode.Write))
            {
              
                
                    byte[] byteInput = new byte[fsInput.Length - 1];
                    fsInput.Read(byteInput, 0, byteInput.Length);
                    cs.Write(byteInput, 0, byteInput.Length);

                   
                    
            }
            FileInfo old = new FileInfo(fileName);
            FileInfo newer = new FileInfo(temp);
            old.Delete();
            newer.MoveTo(Path.Combine(path, fileName));
       
        }
        public void Decrypt()
        {
            string temp = Path.GetTempFileName();
            string path = System.IO.Path.GetDirectoryName(Application.ExecutablePath);
            byte[] pword = Encoding.UTF8.GetBytes(textBox1.Text);
            byte[] hash = SHA256.Create().ComputeHash(pword);
            byte[] iv = MD5.Create().ComputeHash(pword);
            byte[] key = hash;

            using(FileStream fsInput = new FileStream(fileName, FileMode.Open, FileAccess.Read))
            using(SymmetricAlgorithm alg = Aes.Create())
            using(ICryptoTransform enc = alg.CreateDecryptor(key, iv))
            using (CryptoStream cs = new CryptoStream(fsInput, enc, CryptoStreamMode.Read))
            {
                StreamWriter sw = new StreamWriter(temp);
                sw.Write(new StreamReader(cs).ReadToEnd());
                sw.Flush();
                sw.Close();

            }
            FileInfo encrypted = new FileInfo(fileName);
            FileInfo decrypted = new FileInfo(temp);
            encrypted.Delete();
            decrypted.MoveTo(Path.Combine(path, fileName));
        }

file encryption xml
  • asked one year ago
  • edited one year ago
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last answered one year ago

1 answers

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I'm an idiot. What I had originally posted was all wrong. It was wrong because I didn't encrypt correctly which caused all the problems. The key was to allow the CryptoStream to close (and therefore flush its buffers) before interpreting the data. I didn't and I imagine your code does the same. Try flushing your CryptoStream at the end of the block to see if that fixes it.

public void Encrypt()
{
    string temp = Path.GetTempFileName();
    string path = System.IO.Path.GetDirectoryName(Environment.CurrentDirectory);
    byte[] pword = Encoding.UTF8.GetBytes(PASSWORD);
    byte[] hash = SHA256.Create().ComputeHash(pword);
    byte[] iv = MD5.Create().ComputeHash(pword);
    byte[] key = hash;

    using (FileStream fsInput = new FileStream(PATH, FileMode.Open, FileAccess.Read))
    using (SymmetricAlgorithm alg = Aes.Create())
    using (ICryptoTransform enc = alg.CreateEncryptor(key, iv))
    using (FileStream fsOutput = new FileStream(temp, FileMode.Create, FileAccess.Write))
    using (CryptoStream cs = new CryptoStream(fsOutput, enc, CryptoStreamMode.Write))
    {
        byte[] byteInput = new byte[fsInput.Length];
        fsInput.Read(byteInput, 0, byteInput.Length);
        cs.Write(byteInput, 0, byteInput.Length);
        cs.Flush();
    }
    FileInfo old = new FileInfo(PATH);
    FileInfo newer = new FileInfo(temp);
    old.Delete();
    newer.MoveTo(Path.Combine(path, PATH));
}



I'll leave a now 100% working code I had put earlier for your reference. I wrote up an Encryption class to handle the encryption and decryption of data based on a password. This program also tests it. You're free to use it if you wish.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using System.IO;
using System.Security.Cryptography;

namespace EncryptionTest
{
    public static class Encryptor
    {
        private static readonly SymmetricAlgorithm _algorithm = Aes.Create();

        private static void CreateKeyIV(string password, out byte[] key, out byte[] iv)
        {
            Rfc2898DeriveBytes db = new Rfc2898DeriveBytes(password, Encoding.Unicode.GetBytes(password));
            key = db.GetBytes(_algorithm.KeySize / 8);
            iv = db.GetBytes(_algorithm.BlockSize / 8);
        }

        public static byte[] Encrypt(string password, string plaintext)
        {
            byte[] key, iv;
            CreateKeyIV(password, out key, out iv);
            using (MemoryStream encrypted = new MemoryStream())
            {
                using (CryptoStream enc = new CryptoStream(encrypted, _algorithm.CreateEncryptor(key, iv), CryptoStreamMode.Write))
                using (StreamWriter writer = new StreamWriter(enc))
                    writer.Write(plaintext);
                return encrypted.ToArray();
            }
        }

        public static string Decrypt(string password, byte[] ciphertext)
        {
            byte[] key, iv;
            CreateKeyIV(password, out key, out iv);
            using (MemoryStream encrypted = new MemoryStream(ciphertext))
            using (CryptoStream dec = new CryptoStream(encrypted, _algorithm.CreateDecryptor(key, iv), CryptoStreamMode.Read))
            using (StreamReader reader = new StreamReader(dec))
            {
                try
                {
                    return reader.ReadToEnd();
                }
                catch (CryptographicException)
                {
                    throw new CryptographicException("Invalid password.");
                }
            }
        }

        public static bool TryDecrypt(string password, byte[] ciphertext, out string decoded)
        {
            try
            {
                decoded = Decrypt(password, ciphertext);
                return true;
            }
            catch (CryptographicException)
            {
                decoded = String.Empty;
                return false;
            }
        }
    }

    class Program
    {
        const string PATH = @"..\..\Program.cs";
        const string PASSWORD = "foobar";

        static void Main(string[] args)
        {
            string plaintext = File.ReadAllText(PATH);

            Console.WriteLine("Original Text:");
            Console.Write(plaintext);
            Console.WriteLine();

            byte[] ciphertext = Encryptor.Encrypt(PASSWORD, plaintext);

            // print ciphertext in 32 byte blocks
            int blockSize = 32;
            var q = from i in Enumerable.Range(0, (int)Math.Ceiling((double)ciphertext.Length / blockSize))
                    let block = ciphertext.Skip(i * blockSize).Take(blockSize)
                    select String.Join("", block.Select(b => b.ToString("X2")).ToArray());
            Console.WriteLine("Encrypted Data:");
            foreach (string line in q)
                Console.WriteLine(line);
            Console.WriteLine();

            string decoded;
            // try bad password
            Console.Write("Trying To Decrypt With Bad Password: ");
            if (Encryptor.TryDecrypt(PASSWORD + "x", ciphertext, out decoded))
            {
                Console.WriteLine("PASSED!");
                Console.WriteLine("Decrypted Text:");
                Console.Write(decoded);
                Console.WriteLine();
            }
            else
            {
                Console.WriteLine("FAILED!");
                Console.WriteLine();
            }

            // print decrypted data
            Console.Write("Trying To Decrypt With Good Password: ");
            if (Encryptor.TryDecrypt(PASSWORD, ciphertext, out decoded))
            {
                Console.WriteLine("PASSED!");
                Console.WriteLine("Decrypted Text:");
                Console.Write(decoded);
                Console.WriteLine();
            }
            else
            {
                Console.WriteLine("FAILED!");
                Console.WriteLine();
            }

            Console.Write("Decrypting With Bad Password: ");
            decoded = Encryptor.Decrypt(PASSWORD + "x", ciphertext); // fail
            Console.WriteLine("Decrypted Text:");
            Console.Write(decoded);
            Console.WriteLine();

            Console.Write("Press any key to continue . . . ");
            Console.ReadKey(true);
            Console.WriteLine();
        }
    }
}


[edit]
Fixed++.

  • answered one year ago by:

    Jeff1203
    538
  • edited one year ago
(x)
stev0
45

Wasnt sure which site to catch you on. Like I noted earlier, the flushing thing is working nicely. Based on the example you've put here, I understand what the encryption class is doing, but its not clear to me how I would modify this for what I'm trying to do. I figure the entire encryption part shouldnt be changed, I would just change the portions that output the decrypted data to the Console to instead direct the output into the Temp file and do the move/rename like I've been doing?

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