How to: Secure Connection Strings When Using Data Source Controls

https://docs.microsoft.com/en-us/previous-versions/dotnet/netframework-3.0/dx0f3cf2(v=vs.85)

When working with data source controls it is recommended that you centralize the location of your connection strings by storing them in the application's Web.config file. This simplifies the management of connection strings by making them available to all of the ASP.NET pages in a Web application. In addition, you do not need to modify numerous individual pages if your connection string information changes. Finally, you can improve the security of sensitive information stored in a connection string, such as the database name, user name, password, and so on, by encrypting the connection string section of the Web.config file using protected configuration.

This topic describes how to store connection strings in the connectionStrings configuration section in the Web.config file, and how to use the command-line .NET Framework tool to encrypt connection strings for additional security.

To store a connection string in the Web.config file

Open the Web.config file for your application. If a Web.config file does not already exist, create a text file named Web.config and add the following content:

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<?xml version="1.0"?>

<configuration

        xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0">

    <appSettings/>

    <system.web>

    </system.web>

</configuration>

In the configuration element, create a new element named connectionStrings, as shown in the following example:

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<?xml version="1.0"?>

<configuration

        xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0">

    <connectionStrings>    </connectionStrings>

    <appSettings/>

    <system.web>

    </system.web>

</configuration>

In the connectionStrings element, create an add element for each connection string you will use in your Web application. Include the attributes shown in the following table.

Attribute	Description
name	A name for this connection string configuration object. This name will be used by data source controls and other features to reference the connection string information.
connectionString	The connection string to the data source.
providerName	The namespace of the NET Framework data provider to use for this connection, such as System.Data.SqlClient, System.Data.OleDb or System.Data.Odbc.

A completed connectionStrings element might look like the following example:

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<connectionStrings>

  <add

    name="NorthwindConnection"

    connectionString="Data Source=localhost;Integrated Security=SSPI;Initial Catalog=Northwind;" />

</connectionStrings>

Save and close the Web.config file.

You can now reference the connection string for your data source control by referring to the name you specified for the name attribute.
In the ConnectionString attribute for your data source control, use the connection string expression syntax to reference the connection information from the Web.config file.

The following example shows a SqlDataSource control in which the connection string is read from the Web.config file:

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```
<asp:SqlDataSource ID="ProductsDataSource" Runat="server"

    SelectCommand="SELECT * from Products"

    ConnectionString="<%$ ConnectionStrings: NorthwindConnection %>"

</asp:SqlDataSource>
```

To encrypt connection string information stored in the Web.config file

At the Windows command line, run the ASP.NET IIS registration tool (aspnet_regiis.exe) with the following options:

The -pe option, passing it the string "connectionStrings" to encrypt the connectionStrings element.
The -app option, passing it the name of your application.

The aspnet_regiis.exe tool is located in the %systemroot%\Microsoft.NET\Framework\versionNumber folder.

The following example shows how to encrypt the connectionStrings section of the Web.config file for an application named SampleApplication:

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aspnet_regiis -pe "connectionStrings" -app "/SampleApplication"

When the command has finished, you can view the contents of the Web.config file. The connectionStringsconfiguration section will contain encrypted information instead of a clear-text connection string, as shown in the following example:

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<configuration>

   <connectionStrings configProtectionProvider="RsaProtectedConfigurationProvider">

      <EncryptedData Type="http://www.w3.org/2001/04/xmlenc#Element"

         xmlns="http://www.w3.org/2001/04/xmlenc#">

         <EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#tripledes-cbc" />

         <KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">

            <EncryptedKey xmlns="http://www.w3.org/2001/04/xmlenc#">

               <EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-1_5" />

               <KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">

                  <KeyName>RSA Key

                  </KeyName>

               </KeyInfo>

               <CipherData>

                  <CipherValue>WcFEbDX8VyLfAsVK8g6hZVAG1674ZFc1kWH0BoazgOwdBfinhcAmQmnIn0oHtZ5tO2EXGl+dyh10giEmO9NemH4YZk+iMIln+ItcEay9CGWMXSen9UQLpcQHQqMJErZiPK4qPZaRWwqckLqriCl9X8x9OE7jKIsO2Ibapwj+1Jo=

                  </CipherValue>

               </CipherData>

            </EncryptedKey>

         </KeyInfo>

         <CipherData>

            <CipherValue>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

            </CipherValue>

         </CipherData>

      </EncryptedData>

   </connectionStrings>

</configuration>

Leave the command prompt open for later steps.

Determine the user account or identity under which ASP.NET runs by retrieving the current WindowsIdentity name.

The following example shows one way to determine the WindowsIdentity name:

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<%@ Page Language="C#" %>

<%

Response.Write(System.Security.Principal.WindowsIdentity.GetCurrent().Name);

%>

Note
By default, on Windows Server 2003 with impersonation for an ASP.NET application disabled in the Web.config file, the identity under which the application runs is the NETWORK SERVICE account. On other versions of Windows, ASP.NET runs under the local ASPNET account.

The user account or identity under which ASP.NET runs must have read access to the encryption key used to encrypt and decrypt sections of the Web.config file. This procedure assumes that your Web site is configured with the default RsaProtectedConfigurationProvider specified in the Machine.config file named "RsaProtectedConfigurationProvider". The RSA key container used by the default RsaProtectedConfigurationProvider is named "NetFrameworkConfigurationKey".

At the command prompt, run the aspnet_regiis.exe tool with the following options:
- The -pa option, passing it the name of the RSA key container for the default RsaProtectedConfigurationProvider.
- The identity of your ASP.Net application, as determined in the preceding step.
The following example shows how to grant the NETWORK SERVICE account access to the machine-level "NetFrameworkConfigurationKey" RSA key container:

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```
aspnet_regiis -pa "NetFrameworkConfigurationKey" "NT AUTHORITY\NETWORK SERVICE"
```
To decrypt the encrypted Web.config file contents, run the aspnet_regiis.exe tool with the -pd option. The syntax is the same as encrypting Web.config file contents with the -pe option except that you do not specify a protected configuration provider. The appropriate provider is identified in the configProtectionProvider attribute for the protected section.

The following example shows how to decrypt the connectionStrings element of ASP.NET application SampleApplication.

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```
aspnet_regiis -pd "connectionStrings" -app "/SampleApplication"
```