internal static ECParameters ExportNamedCurveParameters(CngKey key, bool includePrivateParameters)
{
byte[] ecBlob = ExportKeyBlob(key, includePrivateParameters);
// We now have a buffer laid out as follows:
// BCRYPT_ECCKEY_BLOB header
// byte[cbKey] Q.X
// byte[cbKey] Q.Y
// -- Private only --
// byte[cbKey] D
ECParameters ecParams = new ECParameters();
KeyBlobMagicNumber magic = (KeyBlobMagicNumber)BitConverter.ToInt32(ecBlob, 0);
// Check the magic value in the key blob header. If the blob does not have the required magic,
// then throw a CryptographicException.
CheckMagicValueOfKey(magic, includePrivateParameters);
unsafe
{
// Fail-fast if a rogue provider gave us a blob that isn't even the size of the blob header.
if (ecBlob.Length < sizeof(BCRYPT_ECCKEY_BLOB))
throw ErrorCode.E_FAIL.ToCryptographicException();
fixed(byte *pEcBlob = ecBlob)
{
BCRYPT_ECCKEY_BLOB *pBcryptBlob = (BCRYPT_ECCKEY_BLOB *)pEcBlob;
int offset = sizeof(BCRYPT_ECCKEY_BLOB);
ecParams.Q = new ECPoint
{
X = Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbKey),
Y = Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbKey)
};
if (includePrivateParameters)
{
ecParams.D = Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbKey);
}
}
}
ecParams.Curve = ECCurve.CreateFromFriendlyName(key.GetCurveName());
return(ecParams);
}
internal static void ExportParameters(
CngKey key,
bool includePrivateParameters,
ref ECParameters ecparams)
{
string curveName = key.GetCurveName();
if (string.IsNullOrEmpty(curveName))
{
byte[] fullKeyBlob = ECCng.ExportFullKeyBlob(key, includePrivateParameters);
ECCng.ExportPrimeCurveParameters(ref ecparams, fullKeyBlob, includePrivateParameters);
}
else
{
byte[] keyBlob = ECCng.ExportKeyBlob(key, includePrivateParameters);
ECCng.ExportNamedCurveParameters(ref ecparams, keyBlob, includePrivateParameters);
ecparams.Curve = ECCurve.CreateFromFriendlyName(curveName);
}
}
/// <summary>
/// Exports the key used by the ECC object into an <see cref="ECParameters"/> object.
/// If the key was created as a named curve, the Curve property will contain named curve parameters
/// otherwise it will contain explicit parameters.
/// </summary>
/// <exception cref="CryptographicException">
/// if there was an issue obtaining the curve values.
/// </exception>
/// <returns>The key and named curve parameters used by the ECC object.</returns>
public override ECParameters ExportParameters()
{
using (CngKey key = Import())
{
ECParameters ecparams = default;
string? curveName = key.GetCurveName(out _);
if (string.IsNullOrEmpty(curveName))
{
byte[] fullKeyBlob = ECCng.ExportFullKeyBlob(key, includePrivateParameters: false);
ECCng.ExportPrimeCurveParameters(ref ecparams, fullKeyBlob, includePrivateParameters: false);
}
else
{
byte[] keyBlob = ECCng.ExportKeyBlob(key, includePrivateParameters: false);
ECCng.ExportNamedCurveParameters(ref ecparams, keyBlob, includePrivateParameters: false);
ecparams.Curve = ECCurve.CreateFromFriendlyName(curveName);
}
return(ecparams);
}
}
internal static byte[] ExportKeyBlob(
CngKey key,
bool includePrivateParameters,
out CngKeyBlobFormat format,
out string?curveName)
{
curveName = key.GetCurveName(out _);
bool forceGenericBlob = false;
if (string.IsNullOrEmpty(curveName))
{
// Normalize curveName to null.
curveName = null;
forceGenericBlob = true;
format = includePrivateParameters ?
CngKeyBlobFormat.EccFullPrivateBlob :
CngKeyBlobFormat.EccFullPublicBlob;
}
else
{
format = includePrivateParameters ?
CngKeyBlobFormat.EccPrivateBlob :
CngKeyBlobFormat.EccPublicBlob;
}
byte[] blob = key.Export(format);
// Importing a known NIST curve as explicit parameters NCryptExportKey may
// cause it to export with the dwMagic of the known curve and a generic blob body.
// This combination can't be re-imported. So correct the dwMagic value to allow it
// to import.
if (forceGenericBlob)
{
FixupGenericBlob(blob);
}
return(blob);
}
