Question

I have an application which is making use of the RSACryptoServiceProvider to decrypt some data using a known private key (stored in a variable).

When the IIS Application Pool is configured to use Network Service, everything runs fine.

However, when we configure the IIS Application Pool to run the code under a different Identity, we get the following:

System.Security.Cryptography.CryptographicException: The system cannot find the file specified.

   at System.Security.Cryptography.Utils.CreateProvHandle(CspParameters parameters, Boolean randomKeyContainer)
   at System.Security.Cryptography.RSACryptoServiceProvider.ImportParameters(RSAParameters parameters)
   at System.Security.Cryptography.RSA.FromXmlString(String xmlString)

The code is something like this:

byte[] input; 
byte[] output; 
string private_key_xml; 

var provider = new System.Cryptography.RSACryptoServiceProvider(this.m_key.Key_Size);
provider.FromXmlString(private_key_xml); // Fails Here when Application Pool Identity != Network Service

ouput = provider.Decrypt(input, false); // False = Use PKCS#1 v1.5 Padding

There are resources which attempt to answer it by stating that you should give the user read access to the machine key store – however there is no definitive answer to solve this issue.

Environment: IIS 6.0, Windows Server 2003 R2, .NET 3.5 SP1

Answer 1

Indeed you need to work a code like this

CspParameters _cpsParameter;
RSACryptoServiceProvider RSAProvider;

_cpsParameter = new CspParameters();
_cpsParameter.Flags = CspProviderFlags.UseMachineKeyStore;

RSAProvider = new RSACryptoServiceProvider(1024, _cpsParameter); 

The following users need access to the folder: C:\Documents and Settings\All Users\Application data\Microsoft\Crypto\RSA\MachineKeys

1. IIS user account (anonymmous)
2. The user account you use to impersonate your application in the web.config settings.

So now it is working fine for me.