Access X509 Certificate store with unmanaged C++ - c++

Question

Does anyone know how I would do the equivalent of the below C# code using unmanaged C++ i.e. query a certificate from the X509 certificate store by thumbprint?
var store = new X509Store(StoreName.My, StoreLocation.LocalMachine);
store.Open(OpenFlags.ReadOnly);
var allCerts = store.Certificates;
foreach (var certificate in from X509Certificate2 certificate in allCerts
where certificate.Thumbprint != null
&& certificate.Thumbprint.Equals(thumbprint, StringComparison.OrdinalIgnoreCase)
select certificate)
{
return certificate;
}
Thanks in advance
Dave

Answer 1

In order to accomplish what you want, you'll have to look into the Win32 CryptAPI library. It won't be as easy as .NET. Look into CertOpenStore and CertFindCertificateInStore.
You'll need to open a certificate store and pass it into CertFindCertificateStore, creating a structure to hold whatever criteria you want to use to find your certificate. You can use a serial number, signature, etc.
HCERTSTORE hSysStore = NULL;
PCCERT_CONTEXT pDesiredCert = NULL;
if(hSysStore = CertOpenStore(
CERT_STORE_PROV_SYSTEM, // The store provider type
0, // The encoding type is
// not needed
NULL, // Use the default HCRYPTPROV
CERT_SYSTEM_STORE_CURRENT_USER, // Set the store location in a
// registry location
L"MY" // The store name as a Unicode
// string
))
{
//We have our store, let's do stuff with it
if (pDesiredCert = CertFindCertificateInStore(.....) { ..... }
}
else
{
//Error stuff
}
You will need to #include <Wincrypt.h> and #include <windows.h>

Answer 2

The code from CertFindCertificateInStore. will not work on newer systems. On newer versions of Windows the certificate's name or subject are in Unicode format which uses 2 bytes for each character. The folowing line:
LPCSTR lpszCertSubject = (LPCSTR) "Cert_subject_1";
has to be change into:
LPCWSTR lpszCertSubject = (LPCWSTR ) L"Cert_subject_1";
or
LPCTSTR lpszCertSubject = (LPCTSTR ) _T"Cert_subject_1"; // add #include <tchar.h>
depending on what you need.