private static SafeProvOrNCryptKeyHandle TryGetCertificatePrivateKey(X509Certificate2 cert, bool silent, out Exception exception)
{
CryptAcquireCertificatePrivateKeyFlags flags =
CryptAcquireCertificatePrivateKeyFlags.CRYPT_ACQUIRE_USE_PROV_INFO_FLAG
| CryptAcquireCertificatePrivateKeyFlags.CRYPT_ACQUIRE_COMPARE_KEY_FLAG
// Note: Using CRYPT_ACQUIRE_ALLOW_NCRYPT_KEY_FLAG rather than CRYPT_ACQUIRE_PREFER_NCRYPT_KEY_FLAG because wrapping an NCrypt wrapper over CAPI keys unconditionally
// causes some legacy features (such as RC4 support) to break.
| CryptAcquireCertificatePrivateKeyFlags.CRYPT_ACQUIRE_ALLOW_NCRYPT_KEY_FLAG;
if (silent)
{
flags |= CryptAcquireCertificatePrivateKeyFlags.CRYPT_ACQUIRE_SILENT_FLAG;
}
bool mustFree;
using (SafeCertContextHandle hCertContext = cert.CreateCertContextHandle())
{
IntPtr hKey;
CryptKeySpec keySpec;
if (!Interop.Crypt32.CryptAcquireCertificatePrivateKey(hCertContext, flags, IntPtr.Zero, out hKey, out keySpec, out mustFree))
{
exception = Marshal.GetHRForLastWin32Error().ToCryptographicException();
return null;
}
// We need to know whether we got back a CRYPTPROV or NCrypt handle. Unfortunately, NCryptIsKeyHandle() is a prohibited api on UWP.
// Fortunately, CryptAcquireCertificatePrivateKey() is documented to tell us which one we got through the keySpec value.
bool isNCrypt;
switch (keySpec)
{
case CryptKeySpec.AT_KEYEXCHANGE:
case CryptKeySpec.AT_SIGNATURE:
isNCrypt = false;
break;
case CryptKeySpec.CERT_NCRYPT_KEY_SPEC:
isNCrypt = true;
break;
default:
// As of this writing, we've exhausted all the known values of keySpec. We have no idea what kind of key handle we got so
// play it safe and fail fast.
throw new NotSupportedException(SR.Format(SR.Cryptography_Cms_UnknownKeySpec, keySpec));
}
SafeProvOrNCryptKeyHandleUwp hProvOrNCryptKey = new SafeProvOrNCryptKeyHandleUwp(hKey, ownsHandle: mustFree, isNcrypt: isNCrypt);
exception = null;
return hProvOrNCryptKey;
}
}
