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ASP.NET Application Deployment Best Practices - Part 1

by Steve Syfuhs / September 16, 2009 04:00 PM

Over the last few months I have been collecting best practices for deploying ASP.NET applications to production.  The intent was to create a document that described the necessary steps needed to deploy consistent, reliable, secure applications that are easily maintainable for administrators.  The result was an 11 page document.  I would like to take a couple excerpts from it and essentially list what I believe to be key requirements for production applications.

The key is consistency.

  • Generate new encryption keys

The benefit to doing this is that internal hashing and encrypting schemes use different keys between applications. If an application is compromised, the private keys that can get recovered will have no effect on other applications. This is most important in applications that use Forms Authentication such as the member’s section. This Key Generator app is using built-in .NET key generation code in the RNGCryptoServiceProvider.

  • Version and give Assemblies Strong Names

Use AssemblyInfo.cs file:

[assembly: AssemblyTitle("NameSpace.Based.AssemblyTitle")]
[assembly: AssemblyDescription("This is My Awesome Assembly…")]
[assembly: AssemblyConfiguration("")]
[assembly: AssemblyCompany("My Awesome Company")]
[assembly: AssemblyProduct("ApplicationName")]
[assembly: AssemblyCopyright("Copyright © 2009")]
[assembly: AssemblyTrademark("TM Application Name")]
[assembly: AssemblyCulture("en-CA")]

Strong names and versioning is the backbone of .NET assemblies. It helps distinguish between different versions of assemblies, and provides copyright attributes to code we have written internally. This is especially helpful if we decide to sell any of our applications.

  • Deploy Shared Assemblies to the GAC
    • Assemblies such as common controls
    • gacutil.exe -I "g:\dev\published\myApp\bin\myAssembly.dll"

If any assemblies are created that get used across multiple applications they should be deployed to the GAC (Global Assembly Cache). Examples of this could be Data Access Layers, or common controls such as the Telerik controls. The benefit to doing this is that we will not have multiple copies of the same DLL in different applications. A requirement of doing this is that the assembly must be signed and use a multipart name.

  • Pre-Compile Site: [In Visual Studio] Build > Publish Web Site

Any application that is in production should be running in a compiled state. What this means is that any application should not have any code-behind files or App_Code class files on the servers. This will limit damage if our servers are compromised, as the attacker will not be able to modify the source.

  • Encrypt SQL Connections and Connection Strings

Encrypt SQL Connection Strings

Aspnet_regiis.exe -pe connectionStrings -site myWebSite -app /myWebApp

Encrypt SQL Connections

Add ‘Encrypt=True’ to all connection strings before encrypting

SQL Connections contain sensitive data such as username/password combinations for access to database servers. These connection strings are stored in web.config files which are stored in plain-text on the server. If malicious users access these files they will have credentials to access the servers. Encrypting the strings will prevent the ability to read the config section.

However, encrypting the connection string is only half of the issue. SQL transactions are transmitted across the network in plain-text. Sensitive data could be acquired if a network sniffer was running on a compromised web server. SQL Connections should also be encrypted using SSL Certificates.

  • Use key file generated by Strong Name Tool:

C:\Program Files\Microsoft SDKs\Windows\v7.0A\bin\sn.exe

“sn.exe -k g:\dev\path\to\app\myAppKey.snk”

Signing an assembly provides validation that the code is ours. It will also allow for GAC deployment by giving the assembly a signature. The key file should be unique to each application, and should be kept in a secure location.

  • Set retail=”true” in machine.config

<configuration>

<system.web>

<deployment retail="true"/>

</system.web>

</configuration>

In a production environment applications do not want to show exception errors or trace messages. Setting the retail property to true is simple way to turn off debugging, tracing, and force the application to use friendly error pages.

In part 2 I continue my post on more best practices for deployment to a production environment.

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Steve is a renaissance kid when it comes to technology. He spends his time in the security stack.