RSACryptoServiceProvider CryptographicException System Cannot Find the File Specified under ASP.NET

Posted by Will Hughes on Stack Overflow See other posts from Stack Overflow or by Will Hughes
Published on 2009-07-09T09:48:10Z Indexed on 2010/04/29 23:17 UTC
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Filed under:

ASP.NET

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applicationpool

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.NET

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cryptography

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

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