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FindPrivateKey

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It can be difficult to find the location and name of the private key file associated with a specific X.509 certificate in the certificate store. The FindPrivateKey.exe tool facilitates this process.

X.509 certificates are installed by an Administrator or any user in the machine. However the certificate may be accessed by a service running under a different account (for example the ASPNET on Windows XP or the NETWORK SERVICE accounts on Windows Server 2003).

This account may not have access to the private key file because the certificate was not installed by it originally. The FindPrivateKey tool gives you the location of a given X.509 Certificate's private key file. You can add permissions or remove permissions to this file once you know the location of the particular X.509 certificates' private key file.

The samples that use certificates for security use the FindPrivateKey tool in the Setup.bat file. Once the private key file has been found you can use other tools such as Cacls.exe to set the appropriate access rights onto the file.

When running a Windows Communication Foundation (WCF) service under a user account, such as a self-hosted executable, you should ensure that the user account has read-only access to the file. When running a WCF service under Internet Information Services (IIS) the default accounts that the service runs under are the ASPNET on Windows XP or the NETWORK SERVICE on Windows Server 2003, which by default do not have access to the private key file.

Examples

When accessing a certificate for which the process does not have read privilege you see an exception message similar to the following example.

System.ArgumentException was unhandled
Message="The certificate 'CN=localhost' must have a private key that is capable of key exchange.  The process must have access rights for the private key."
Source="System.ServiceModel"

When this occurs use the FindPrivateKey tool to find the private key file and then set the access right for the process that the service is running under. For example, this can be done with the Cacls.exe tool as shown in the following example.

cacls.exe "C:\Documents and Settings\All Users\Application Data\Microsoft\Crypto\RSA\MachineKeys\8aeda5eb81555f14f8f9960745b5a40d_38f7de48-5ee9-452d-8a5a-92789d7110b1" /E /G "NETWORK SERVICE":R

To build the FindPrivateKey project

  1. Open Windows Explorer and navigate to the language-specific subdirectory under the directory location where you installed the sample.

  2. Double-click the .sln file icon to open the file in Visual Studio.

  3. In the Build menu, select Rebuild Solution. The client program files are built to client\bin and the service program files are built to service\bin.

  4. Building the solution generates the file: FindPrivateKey.exe.

Conventions—Command Line Entries

"[option]" represents an optional set of parameters.

"{option}" represents a mandatory set of parameters.

"option1 | option2" represents a choice between sets of options.

"<value>" represents a parameter value to be entered.

Usage

FindPrivateKey <storeName> <storeLocation> [{ {-n <subjectName>} | {-t <thumbprint>} } [-f | -d | -a]]

 

Where:

       <subjectName> The subject name of the certificate
       <thumbprint>  The thumbprint of the certificate (You can use the Certmgr.exe tool to find this)
       -f            output file name only
       -d            output directory only
       -a            output absolute file name

If no parameters are specified at the command prompt then this help text is displayed.

Examples

This example finds the filename of the certificate with a subject name of "CN=localhost", in the Personal store of the Current User.FindPrivateKey My CurrentUser -n "CN=localhost".

This example finds the filename of the certificate with a subject name of "CN=localhost", in the Personal store of the Current and output the full directory path.

User.FindPrivateKey My CurrentUser -n "CN=localhost" -a

This example finds the filename of the certificate with a thumbprint of "03 33 98 63 d0 47 e7 48 71 33 62 64 76 5c 4c 9d 42 1d 6b 52", in the Personal store of the Local Computer.

FindPrivateKey My LocalMachine -t "03 33 98 63 d0 47 e7 48 71 33 62 64 76 5c 4c 9d 42 1d 6b 52" –c
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