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GoalBook - A Hybrid Smart Client

, 25 Sep 2009
A WPF hybrid smart client that synchronises your goals with the Toodledo online To-do service.
Prize winner in Competition "Smart Client Article Contest"
GoalBook.zip
GoalBook
Dependencies
CAG WPF 2
Microsoft.Practices.Composite.dll
Microsoft.Practices.Composite.Presentation.dll
Microsoft.Practices.Composite.UnityExtensions.dll
Microsoft.Practices.ObjectBuilder2.dll
Microsoft.Practices.ServiceLocation.dll
Microsoft.Practices.Unity.dll
vssver2.scc
CSLA
Csla.dll
Csla.XmlSerializers.dll
vssver2.scc
Infragistics
Infragistics3.Wpf.DataPresenter.v9.1.Express.dll
Infragistics3.Wpf.Editors.v9.1.Express.dll
Infragistics3.Wpf.v9.1.Express.dll
vssver2.scc
WPFToolkit
vssver2.scc
WPFToolkit.dll
GoalBook.Controls
CheckedList
vssver2.scc
Properties
vssver2.scc
vssver2.scc
GoalBook.Goals
GoalBook.Goals.csproj.user
Properties
vssver2.scc
Views
vssver2.scc
vssver2.scc
GoalBook.Infrastructure
Comparers
vssver2.scc
Constants
vssver2.scc
Controls
Converters
vssver2.scc
Enums
vssver2.scc
Events
vssver2.scc
GoalBook.Infrastructure.csproj.user
Helpers
vssver2.scc
Interfaces
vssver2.scc
ObjectModel
vssver2.scc
Printing
vssver2.scc
Properties
vssver2.scc
vssver2.scc
GoalBook.Notes
GoalBook.Notes.csproj.user
Properties
vssver2.scc
Resources
arrow_redo.png
arrow_undo.png
cut.png
page_copy.png
paste_plain.png
text_bold.png
text_indent.png
text_indent_remove.png
text_italic.png
text_list_bullets.png
text_list_numbers.png
vssver2.scc
world_link.png
Views
vssver2.scc
vssver2.scc
GoalBook.Public
Encryption
vssver2.scc
HtmlConverter
vssver2.scc
HtmlParser
vssver2.scc
Misc
vssver2.scc
Properties
vssver2.scc
vssver2.scc
GoalBook.Shell
App.ico
Commands
vssver2.scc
GoalBook.Shell.csproj.user
Journal.ico
Journal48.ico
Misc
vssver2.scc
Modules
vssver2.scc
Properties
licenses.licx
vssver2.scc
Resources
arrow_refresh.png
arrow_undo.png
checked.gif
cross.png
disk.png
email.png
erase.png
error.png
exclamation.png
flag_red.png
group.png
help.png
information.png
magnifier.png
page_red.png
pencil.png
printer.png
user.png
vssver2.scc
Wave.jpg
world.png
world_link.png
Services
vssver2.scc
Splash.png
Views
vssver2.scc
vssver2.scc
Windows
vssver2.scc
GoalBook.snk
GoalBook.Synchronisation
Events
vssver2.scc
Properties
vssver2.scc
ToodleDo
vssver2.scc
vssver2.scc
GoalBook.Tasks
Controls
vssver2.scc
Properties
vssver2.scc
Views
vssver2.scc
vssver2.scc
vssver2.scc
///////////////////////////////////////////////////////////////////////////////
//
//  Copyright (C) 2003 Obviex(TM). 
//  
//  EXAMPLE USE
//  string text = "Hello, world!";
//  string entropy = null;
//  string description;

//  // Call DPAPI to encrypt data with user-specific key.
//  string encrypted = DPAPI.Encrypt(   DPAPI.KeyType.UserKey,
//                                      text,
//                                      entropy,
//                                      "My Data");


//  // Call DPAPI to decrypt data.
//  string decrypted = DPAPI.Decrypt(   encrypted,
//                                      entropy,
//                                      out description);

using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Text;

namespace GoalBook.Public.Encryption
{
    /// <summary>
    /// Encrypts and decrypts data using DPAPI functions.
    /// </summary>
    public class DPAPI
    {
        // Wrapper for DPAPI CryptProtectData function.
        [DllImport("crypt32.dll",
                    SetLastError = true,
                    CharSet = System.Runtime.InteropServices.CharSet.Auto)]
        private static extern
            bool CryptProtectData(ref DATA_BLOB pPlainText,
                                        string szDescription,
                                    ref DATA_BLOB pEntropy,
                                        IntPtr pReserved,
                                    ref CRYPTPROTECT_PROMPTSTRUCT pPrompt,
                                        int dwFlags,
                                    ref DATA_BLOB pCipherText);

        // Wrapper for DPAPI CryptUnprotectData function.
        [DllImport("crypt32.dll",
                    SetLastError = true,
                    CharSet = System.Runtime.InteropServices.CharSet.Auto)]
        private static extern
            bool CryptUnprotectData(ref DATA_BLOB pCipherText,
                                    ref string pszDescription,
                                    ref DATA_BLOB pEntropy,
                                        IntPtr pReserved,
                                    ref CRYPTPROTECT_PROMPTSTRUCT pPrompt,
                                        int dwFlags,
                                    ref DATA_BLOB pPlainText);

        // BLOB structure used to pass data to DPAPI functions.
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        internal struct DATA_BLOB
        {
            public int cbData;
            public IntPtr pbData;
        }

        // Prompt structure to be used for required parameters.
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        internal struct CRYPTPROTECT_PROMPTSTRUCT
        {
            public int cbSize;
            public int dwPromptFlags;
            public IntPtr hwndApp;
            public string szPrompt;
        }

        // Wrapper for the NULL handle or pointer.
        static private IntPtr NullPtr = ((IntPtr)((int)(0)));

        // DPAPI key initialization flags.
        private const int CRYPTPROTECT_UI_FORBIDDEN = 0x1;
        private const int CRYPTPROTECT_LOCAL_MACHINE = 0x4;

        /// <summary>
        /// Initializes empty prompt structure.
        /// </summary>
        /// <param name="ps">
        /// Prompt parameter (which we do not actually need).
        /// </param>
        private static void InitPrompt(ref CRYPTPROTECT_PROMPTSTRUCT ps)
        {
            ps.cbSize = Marshal.SizeOf(
                                      typeof(CRYPTPROTECT_PROMPTSTRUCT));
            ps.dwPromptFlags = 0;
            ps.hwndApp = NullPtr;
            ps.szPrompt = null;
        }

        /// <summary>
        /// Initializes a BLOB structure from a byte array.
        /// </summary>
        /// <param name="data">
        /// Original data in a byte array format.
        /// </param>
        /// <param name="blob">
        /// Returned blob structure.
        /// </param>
        private static void InitBLOB(byte[] data, ref DATA_BLOB blob)
        {
            // Use empty array for null parameter.
            if (data == null)
                data = new byte[0];

            // Allocate memory for the BLOB data.
            blob.pbData = Marshal.AllocHGlobal(data.Length);

            // Make sure that memory allocation was successful.
            if (blob.pbData == IntPtr.Zero)
                throw new Exception(
                    "Unable to allocate data buffer for BLOB structure.");

            // Specify number of bytes in the BLOB.
            blob.cbData = data.Length;

            // Copy data from original source to the BLOB structure.
            Marshal.Copy(data, 0, blob.pbData, data.Length);
        }

        // Flag indicating the type of key. DPAPI terminology refers to
        // key types as user store or machine store.
        public enum KeyType { UserKey = 1, MachineKey };

        // It is reasonable to set default key type to user key.
        private static KeyType defaultKeyType = KeyType.UserKey;

        /// <summary>
        /// Calls DPAPI CryptProtectData function to encrypt a plaintext
        /// string value with a user-specific key. This function does not
        /// specify data description and additional entropy.
        /// </summary>
        /// <param name="plainText">
        /// Plaintext data to be encrypted.
        /// </param>
        /// <returns>
        /// Encrypted value in a base64-encoded format.
        /// </returns>
        public static string Encrypt(string plainText)
        {
            return Encrypt(defaultKeyType, plainText, String.Empty,
                            String.Empty);
        }

        /// <summary>
        /// Calls DPAPI CryptProtectData function to encrypt a plaintext
        /// string value. This function does not specify data description
        /// and additional entropy.
        /// </summary>
        /// <param name="keyType">
        /// Defines type of encryption key to use. When user key is
        /// specified, any application running under the same user account
        /// as the one making this call, will be able to decrypt data.
        /// Machine key will allow any application running on the same
        /// computer where data were encrypted to perform decryption.
        /// Note: If optional entropy is specifed, it will be required
        /// for decryption.
        /// </param>
        /// <param name="plainText">
        /// Plaintext data to be encrypted.
        /// </param>
        /// <returns>
        /// Encrypted value in a base64-encoded format.
        /// </returns>
        public static string Encrypt(KeyType keyType, string plainText)
        {
            return Encrypt(keyType, plainText, String.Empty,
                            String.Empty);
        }

        /// <summary>
        /// Calls DPAPI CryptProtectData function to encrypt a plaintext
        /// string value. This function does not specify data description.
        /// </summary>
        /// <param name="keyType">
        /// Defines type of encryption key to use. When user key is
        /// specified, any application running under the same user account
        /// as the one making this call, will be able to decrypt data.
        /// Machine key will allow any application running on the same
        /// computer where data were encrypted to perform decryption.
        /// Note: If optional entropy is specifed, it will be required
        /// for decryption.
        /// </param>
        /// <param name="plainText">
        /// Plaintext data to be encrypted.
        /// </param>
        /// <param name="entropy">
        /// Optional entropy which - if specified - will be required to
        /// perform decryption.
        /// </param>
        /// <returns>
        /// Encrypted value in a base64-encoded format.
        /// </returns>
        public static string Encrypt(KeyType keyType,
                                     string plainText,
                                     string entropy)
        {
            return Encrypt(keyType, plainText, entropy, String.Empty);
        }

        /// <summary>
        /// Calls DPAPI CryptProtectData function to encrypt a plaintext
        /// string value.
        /// </summary>
        /// <param name="keyType">
        /// Defines type of encryption key to use. When user key is
        /// specified, any application running under the same user account
        /// as the one making this call, will be able to decrypt data.
        /// Machine key will allow any application running on the same
        /// computer where data were encrypted to perform decryption.
        /// Note: If optional entropy is specifed, it will be required
        /// for decryption.
        /// </param>
        /// <param name="plainText">
        /// Plaintext data to be encrypted.
        /// </param>
        /// <param name="entropy">
        /// Optional entropy which - if specified - will be required to
        /// perform decryption.
        /// </param>
        /// <param name="description">
        /// Optional description of data to be encrypted. If this value is
        /// specified, it will be stored along with encrypted data and
        /// returned as a separate value during decryption.
        /// </param>
        /// <returns>
        /// Encrypted value in a base64-encoded format.
        /// </returns>
        public static string Encrypt(KeyType keyType,
                                     string plainText,
                                     string entropy,
                                     string description)
        {
            // Make sure that parameters are valid.
            if (plainText == null) plainText = String.Empty;
            if (entropy == null) entropy = String.Empty;

            // Call encryption routine and convert returned bytes into
            // a base64-encoded value.
            return Convert.ToBase64String(
                    Encrypt(keyType,
                            Encoding.UTF8.GetBytes(plainText),
                            Encoding.UTF8.GetBytes(entropy),
                            description));
        }

        /// <summary>
        /// Calls DPAPI CryptProtectData function to encrypt an array of
        /// plaintext bytes.
        /// </summary>
        /// <param name="keyType">
        /// Defines type of encryption key to use. When user key is
        /// specified, any application running under the same user account
        /// as the one making this call, will be able to decrypt data.
        /// Machine key will allow any application running on the same
        /// computer where data were encrypted to perform decryption.
        /// Note: If optional entropy is specifed, it will be required
        /// for decryption.
        /// </param>
        /// <param name="plainTextBytes">
        /// Plaintext data to be encrypted.
        /// </param>
        /// <param name="entropyBytes">
        /// Optional entropy which - if specified - will be required to
        /// perform decryption.
        /// </param>
        /// <param name="description">
        /// Optional description of data to be encrypted. If this value is
        /// specified, it will be stored along with encrypted data and
        /// returned as a separate value during decryption.
        /// </param>
        /// <returns>
        /// Encrypted value.
        /// </returns>
        public static byte[] Encrypt(KeyType keyType,
                                     byte[] plainTextBytes,
                                     byte[] entropyBytes,
                                     string description)
        {
            // Make sure that parameters are valid.
            if (plainTextBytes == null) plainTextBytes = new byte[0];
            if (entropyBytes == null) entropyBytes = new byte[0];
            if (description == null) description = String.Empty;

            // Create BLOBs to hold data.
            DATA_BLOB plainTextBlob = new DATA_BLOB();
            DATA_BLOB cipherTextBlob = new DATA_BLOB();
            DATA_BLOB entropyBlob = new DATA_BLOB();

            // We only need prompt structure because it is a required
            // parameter.
            CRYPTPROTECT_PROMPTSTRUCT prompt =
                                      new CRYPTPROTECT_PROMPTSTRUCT();
            InitPrompt(ref prompt);

            try
            {
                // Convert plaintext bytes into a BLOB structure.
                try
                {
                    InitBLOB(plainTextBytes, ref plainTextBlob);
                }
                catch (Exception ex)
                {
                    throw new Exception(
                        "Cannot initialize plaintext BLOB.", ex);
                }

                // Convert entropy bytes into a BLOB structure.
                try
                {
                    InitBLOB(entropyBytes, ref entropyBlob);
                }
                catch (Exception ex)
                {
                    throw new Exception(
                        "Cannot initialize entropy BLOB.", ex);
                }

                // Disable any types of UI.
                int flags = CRYPTPROTECT_UI_FORBIDDEN;

                // When using machine-specific key, set up machine flag.
                if (keyType == KeyType.MachineKey)
                    flags |= CRYPTPROTECT_LOCAL_MACHINE;

                // Call DPAPI to encrypt data.
                bool success = CryptProtectData(ref plainTextBlob,
                                                    description,
                                                ref entropyBlob,
                                                    IntPtr.Zero,
                                                ref prompt,
                                                    flags,
                                                ref cipherTextBlob);
                // Check the result.
                if (!success)
                {
                    // If operation failed, retrieve last Win32 error.
                    int errCode = Marshal.GetLastWin32Error();

                    // Win32Exception will contain error message corresponding
                    // to the Windows error code.
                    throw new Exception(
                        "CryptProtectData failed.", new Win32Exception(errCode));
                }

                // Allocate memory to hold ciphertext.
                byte[] cipherTextBytes = new byte[cipherTextBlob.cbData];

                // Copy ciphertext from the BLOB to a byte array.
                Marshal.Copy(cipherTextBlob.pbData,
                                cipherTextBytes,
                                0,
                                cipherTextBlob.cbData);

                // Return the result.
                return cipherTextBytes;
            }
            catch (Exception ex)
            {
                throw new Exception("DPAPI was unable to encrypt data.", ex);
            }
            // Free all memory allocated for BLOBs.
            finally
            {
                if (plainTextBlob.pbData != IntPtr.Zero)
                    Marshal.FreeHGlobal(plainTextBlob.pbData);

                if (cipherTextBlob.pbData != IntPtr.Zero)
                    Marshal.FreeHGlobal(cipherTextBlob.pbData);

                if (entropyBlob.pbData != IntPtr.Zero)
                    Marshal.FreeHGlobal(entropyBlob.pbData);
            }
        }

        /// <summary>
        /// Calls DPAPI CryptUnprotectData to decrypt ciphertext bytes.
        /// This function does not use additional entropy and does not
        /// return data description.
        /// </summary>
        /// <param name="cipherText">
        /// Encrypted data formatted as a base64-encoded string.
        /// </param>
        /// <returns>
        /// Decrypted data returned as a UTF-8 string.
        /// </returns>
        /// <remarks>
        /// When decrypting data, it is not necessary to specify which
        /// type of encryption key to use: user-specific or
        /// machine-specific; DPAPI will figure it out by looking at
        /// the signature of encrypted data.
        /// </remarks>
        public static string Decrypt(string cipherText)
        {
            string description;

            return Decrypt(cipherText, String.Empty, out description);
        }

        /// <summary>
        /// Calls DPAPI CryptUnprotectData to decrypt ciphertext bytes.
        /// This function does not use additional entropy.
        /// </summary>
        /// <param name="cipherText">
        /// Encrypted data formatted as a base64-encoded string.
        /// </param>
        /// <param name="description">
        /// Returned description of data specified during encryption.
        /// </param>
        /// <returns>
        /// Decrypted data returned as a UTF-8 string.
        /// </returns>
        /// <remarks>
        /// When decrypting data, it is not necessary to specify which
        /// type of encryption key to use: user-specific or
        /// machine-specific; DPAPI will figure it out by looking at
        /// the signature of encrypted data.
        /// </remarks>
        public static string Decrypt(string cipherText,
                                     out string description)
        {
            return Decrypt(cipherText, String.Empty, out description);
        }

        /// <summary>
        /// Calls DPAPI CryptUnprotectData to decrypt ciphertext bytes.
        /// </summary>
        /// <param name="cipherText">
        /// Encrypted data formatted as a base64-encoded string.
        /// </param>
        /// <param name="entropy">
        /// Optional entropy, which is required if it was specified during
        /// encryption.
        /// </param>
        /// <param name="description">
        /// Returned description of data specified during encryption.
        /// </param>
        /// <returns>
        /// Decrypted data returned as a UTF-8 string.
        /// </returns>
        /// <remarks>
        /// When decrypting data, it is not necessary to specify which
        /// type of encryption key to use: user-specific or
        /// machine-specific; DPAPI will figure it out by looking at
        /// the signature of encrypted data.
        /// </remarks>
        public static string Decrypt(string cipherText,
                                         string entropy,
                                     out string description)
        {
            // Make sure that parameters are valid.
            if (entropy == null) entropy = String.Empty;

            return Encoding.UTF8.GetString(
                        Decrypt(Convert.FromBase64String(cipherText),
                                    Encoding.UTF8.GetBytes(entropy),
                                out description));
        }

        /// <summary>
        /// Calls DPAPI CryptUnprotectData to decrypt ciphertext bytes.
        /// </summary>
        /// <param name="cipherTextBytes">
        /// Encrypted data.
        /// </param>
        /// <param name="entropyBytes">
        /// Optional entropy, which is required if it was specified during
        /// encryption.
        /// </param>
        /// <param name="description">
        /// Returned description of data specified during encryption.
        /// </param>
        /// <returns>
        /// Decrypted data bytes.
        /// </returns>
        /// <remarks>
        /// When decrypting data, it is not necessary to specify which
        /// type of encryption key to use: user-specific or
        /// machine-specific; DPAPI will figure it out by looking at
        /// the signature of encrypted data.
        /// </remarks>
        public static byte[] Decrypt(byte[] cipherTextBytes,
                                         byte[] entropyBytes,
                                     out string description)
        {
            // Create BLOBs to hold data.
            DATA_BLOB plainTextBlob = new DATA_BLOB();
            DATA_BLOB cipherTextBlob = new DATA_BLOB();
            DATA_BLOB entropyBlob = new DATA_BLOB();

            // We only need prompt structure because it is a required
            // parameter.
            CRYPTPROTECT_PROMPTSTRUCT prompt =
                                      new CRYPTPROTECT_PROMPTSTRUCT();
            InitPrompt(ref prompt);

            // Initialize description string.
            description = String.Empty;

            try
            {
                // Convert ciphertext bytes into a BLOB structure.
                try
                {
                    InitBLOB(cipherTextBytes, ref cipherTextBlob);
                }
                catch (Exception ex)
                {
                    throw new Exception(
                        "Cannot initialize ciphertext BLOB.", ex);
                }

                // Convert entropy bytes into a BLOB structure.
                try
                {
                    InitBLOB(entropyBytes, ref entropyBlob);
                }
                catch (Exception ex)
                {
                    throw new Exception(
                        "Cannot initialize entropy BLOB.", ex);
                }

                // Disable any types of UI. CryptUnprotectData does not
                // mention CRYPTPROTECT_LOCAL_MACHINE flag in the list of
                // supported flags so we will not set it up.
                int flags = CRYPTPROTECT_UI_FORBIDDEN;

                // Call DPAPI to decrypt data.
                bool success = CryptUnprotectData(ref cipherTextBlob,
                                                  ref description,
                                                  ref entropyBlob,
                                                      IntPtr.Zero,
                                                  ref prompt,
                                                      flags,
                                                  ref plainTextBlob);

                // Check the result.
                if (!success)
                {
                    // If operation failed, retrieve last Win32 error.
                    int errCode = Marshal.GetLastWin32Error();

                    // Win32Exception will contain error message corresponding
                    // to the Windows error code.
                    throw new Exception(
                        "CryptUnprotectData failed.", new Win32Exception(errCode));
                }

                // Allocate memory to hold plaintext.
                byte[] plainTextBytes = new byte[plainTextBlob.cbData];

                // Copy ciphertext from the BLOB to a byte array.
                Marshal.Copy(plainTextBlob.pbData,
                             plainTextBytes,
                             0,
                             plainTextBlob.cbData);

                // Return the result.
                return plainTextBytes;
            }
            catch (Exception ex)
            {
                throw new Exception("DPAPI was unable to decrypt data.", ex);
            }
            // Free all memory allocated for BLOBs.
            finally
            {
                if (plainTextBlob.pbData != IntPtr.Zero)
                    Marshal.FreeHGlobal(plainTextBlob.pbData);

                if (cipherTextBlob.pbData != IntPtr.Zero)
                    Marshal.FreeHGlobal(cipherTextBlob.pbData);

                if (entropyBlob.pbData != IntPtr.Zero)
                    Marshal.FreeHGlobal(entropyBlob.pbData);
            }
        }
    }
}

//
// END OF FILE
///////////////////////////////////////////////////////////////////////////////

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License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Mark Brownsword
Software Developer (Senior)
Australia Australia
I've been working as a software developer since 2000 and hold a Bachelor of Business degree from The Open Polytechnic of New Zealand. Computers are for people and I aim to build applications for people that they would want to use.

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