Building Secure ASP.NET Applications: Authentication, Authorization, and Secure Communication
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J.D. Meier, Alex Mackman, Michael Dunner, and Srinath Vasireddy
Microsoft Corporation
Published: November 2002
Last Revised: January 2006
Applies to:
- .NET Framework 1.1
See the "patterns & practices Security Guidance for Applications Index" for links to additional security resources.
See the Landing Page for a starting point and complete overview of Building Secure ASP.NET Applications.
Summary: Applications may choose to store encrypted data such as connection strings and account credentials in the Windows registry. This How To shows you how to store and retrieve encrypted strings in the registry. (7 printed pages)
Notes
Summary of Steps Step 1. Store the Encrypted Data in the Registry
Step 2. Create an ASP.NET Web Application
Additional Resources
The registry represents one possible location for an application to store database connection strings. Although individual registry keys can be secured with Windows access control lists (ACLs), for added security you should store encrypted connection strings.
This How To describes how to store an encrypted database connection string in the registry and retrieve it from an ASP.NET Web application. It uses the generic encryption and decryption managed class library created in How To: Create an Encryption Library in .NET 1.1, which can be found in Reference section of this guide.
If you have not already created the encryption class library assembly, do so before continuing with the current How To.
For more information about other locations and ways of securely storing database connection strings, see Storing Database Connection Strings Securely in Chapter 12, "Data Access Security."
The connection string, initialization vector and key used for encryption will be stored in the registry as named values beneath the following registry key.
HKEY_LOCAL_MACHINE\Software\TestApplication
The initialization vector and key must be stored in order to allow the connection string to be decrypted.
This How To includes the following steps:
- Step 1. Store the Encrypted Data in the Registry
- Step 2. Create an ASP.NET Web Application
This procedure creates a Windows application that will be used to encrypt a sample database string and store it in the registry.
To store the encrypted data in the registry
Start Visual Studio .NET and create a new C# Windows project called EncryptionTestApp.
Add an assembly reference to the Encryption.dll assembly.
To create this assembly, you must perform the steps described in How To: Create an Encryption Library in .NET 1.1 in the Reference section of this guide.
Add the following using statements to the top of Form1.cs beneath the existing using statements.
using Encryption; using System.Text; using Microsoft.Win32;
Add the controls in Table 1 to Form1 and arrange them as illustrated in Figure 1.
Table 1. EncryptionTestApp controls
Control Text ID Label Connection String: TextBox txtConnectionString Label Key: TextBox txtKey Label Initialization Vector: TextBox txtInitializationVector Label Encrypted String TextBox txtEncryptedString Label Decrypted String TextBox txtDecryptedString Button Encrypt btnEncrypt Button Decrypt btnDecrypt Button Write Registry Data btnWriteRegistryData Figure 1. Encryption Test Harness dialog box
Set the Text property of txtConnectionString to
"Server=local; database=pubs; uid=Bob; pwd=Password"
Set the Text property of txtKey to
"0123456789012345"
The key length is 16 bytes to suite the Triple DES encryption algorithm.
Although the key used in this example is simple, ideally you should use complex keys. Use the RNGCryptoServiceProvider or PasswordDeriveBytes class for generating complex keys.
Set the Text property of Form1 to
"Encryption Test Harness"
Double-click the Encrypt button to create a button click event handler and add the following code to the event handler.
try { // Create the encryptor object, specifying 3DES as the // encryption algorithm Encryptor enc = new Encryptor(EncryptionAlgorithm.TripleDes); // Get the connection string as a byte array byte[] plainText = Encoding.ASCII.GetBytes(txtConnectionString.Text); byte[] key = Encoding.ASCII.GetBytes(txtKey.Text); // Perform the encryption byte[] cipherText = enc.Encrypt(plainText, key); // Store the intialization vector, as this will be required // for decryption txtInitializationVector.Text = Encoding.ASCII.GetString(enc.IV); // Display the encrypted string txtEncryptedString.Text = Convert.ToBase64String(cipherText); } catch(Exception ex) { MessageBox.Show("Exception encrypting: " + ex.Message, "Encryption "); }
Return to Form1 in Designer mode and double-click the Decrypt button to create a button click event handler.
Add the following code to the Decrypt button event handler.
try { // Set up the Decryptor object Decryptor dec = new Decryptor(EncryptionAlgorithm.TripleDes); // Set the Initialization Vector dec.IV = Encoding.ASCII.GetBytes(txtInitializationVector.Text); byte[] key = Encoding.ASCII.GetBytes(txtKey.Text); // Perform the decryption byte[] plainText = dec.Decrypt(Convert.FromBase64String( txtEncryptedString.Text), key); // Display the decrypted string. txtDecryptedString.Text = Encoding.ASCII.GetString(plainText); } catch(Exception ex) { MessageBox.Show("Exception decrypting. " + ex.Message, "Encryption Test Harness"); }
Return to Form1 in Designer mode and double-click the Write Registry Data button to create a button click event handler.
Add the following code to the event handler.
// Create registry key and named values RegistryKey rk = Registry.LocalMachine.OpenSubKey("Software",true); rk = rk.CreateSubKey("TestApplication"); // Write encrypted string, initialization vector and key to the registry rk.SetValue("connectionString",txtEncryptedString.Text); rk.SetValue("initVector", Encoding.ASCII.GetBytes(txtInitializationVector.Text)); rk.SetValue("key", Encoding.ASCII.GetBytes( txtKey.Text)); MessageBox.Show("The data has been successfully written to the registry");
Run the application, and then click Encrypt.
The encrypted connection string is displayed in the EncryptedString field.
Click Decrypt.
The original string is displayed in the DecryptedString field.
Click WriteRegistryData.
In the message box, click OK.
Run regedit.exe and view the contents of the following key.
HKLM\Software\TestApplication
Confirm that encoded values are present for the connectionString, initVector and key named values.
Close regedit and the test harness application.
This procedure develops a simple ASP.NET Web application that will retrieve the encrypted connection string from the registry and decrypt it. By default, the ASP.NET process identity used by the Web application will not have access to the registry. Access will need to be explicitly granted.
To create an ASP.NET application
Create a new Visual C# ASP.NET Web Application called EncryptionWebApp.
Add an assembly reference to the Encryption.dll assembly.
To create this assembly, you must perform the steps described in How To: Create an Encryption Library in .NET 1.1 in the Reference section of this guide.
Open Webform1.aspx.cs and add the following using statements at the top of the file beneath the existing using statements.
using Encryption; using System.Text; using Microsoft.Win32;
Add the controls listed in Table 2 to WebForm1.aspx.
Table 2: WebForm1.aspx controls
Control Text ID Label lblEncryptedString Label lblDecryptedString Button Get Connection String btnGetConnectionString Double-click the Get Connection String button to create a button click event handler.
Add the following code to the event handler.
RegistryKey rk = Registry.LocalMachine.OpenSubKey( @"Software\TestApplication",false); lblEncryptedString.Text = (string)rk.GetValue("connectionString"); string initVector = (string)rk.GetValue("initVector"); string strKey = (string)rk.GetValue("key"); Decryptor dec = new Decryptor(EncryptionAlgorithm.TripleDes ); dec.IV = Convert.FromBase64String(initVector); // Decrypt the string byte[] plainText = dec.Decrypt(Convert.FromBase64String( lblEncryptedString.Text), Convert.FromBase64String(strKey)); lblDecryptedString.Text = Encoding.ASCII.GetString(plainText);
On the Build menu, click BuildSolution.
Right-click Webform1.aspx in Solution Explorer, and then click View in Browser.
Click Get Connection String.
The encrypted and decrypted connection strings are displayed on the Web form.
For more information, see How To: Create an Encryption Library in the Reference section of this guide.
Retired Content |
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This content is outdated and is no longer being maintained. It is provided as a courtesy for individuals who are still using these technologies. This page may contain URLs that were valid when originally published, but now link to sites or pages that no longer exist. |