ECDsaX509SignatureGenerator.cs

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using System.Formats.Asn1;
using Internal.Cryptography;
 
namespace System.Security.Cryptography.X509Certificates;
 
internal sealed class ECDsaX509SignatureGenerator : X509SignatureGenerator
{
    private readonly ECDsa _key;
 
    internal ECDsaX509SignatureGenerator(ECDsa key)
    {
        _key = key;
    }
 
    public override byte[] GetSignatureAlgorithmIdentifier(HashAlgorithmName hashAlgorithm)
    {
        string oidValue;
        if (hashAlgorithm == HashAlgorithmName.SHA256)
        {
            oidValue = "1.2.840.10045.4.3.2";
        }
        else if (hashAlgorithm == HashAlgorithmName.SHA384)
        {
            oidValue = "1.2.840.10045.4.3.3";
        }
        else
        {
            if (!(hashAlgorithm == HashAlgorithmName.SHA512))
            {
                throw new ArgumentOutOfRangeException("hashAlgorithm", hashAlgorithm, System.SR.Format(System.SR.Cryptography_UnknownHashAlgorithm, hashAlgorithm.Name));
            }
            oidValue = "1.2.840.10045.4.3.4";
        }
        AsnWriter asnWriter = new AsnWriter(AsnEncodingRules.DER);
        asnWriter.PushSequence();
        asnWriter.WriteObjectIdentifier(oidValue);
        asnWriter.PopSequence();
        return asnWriter.Encode();
    }
 
    public override byte[] SignData(byte[] data, HashAlgorithmName hashAlgorithm)
    {
        byte[] array = _key.SignData(data, hashAlgorithm);
        return Internal.Cryptography.AsymmetricAlgorithmHelpers.ConvertIeee1363ToDer(array);
    }
 
    protected override PublicKey BuildPublicKey()
    {
        ECParameters eCParameters = _key.ExportParameters(includePrivateParameters: false);
        if (!eCParameters.Curve.IsNamed)
        {
            throw new InvalidOperationException(System.SR.Cryptography_ECC_NamedCurvesOnly);
        }
        string text = eCParameters.Curve.Oid.Value;
        if (string.IsNullOrEmpty(text))
        {
            string friendlyName = eCParameters.Curve.Oid.FriendlyName;
            text = friendlyName switch
            {
                "nistP256" => "1.2.840.10045.3.1.7", 
                "nistP384" => "1.3.132.0.34", 
                "nistP521" => "1.3.132.0.35", 
                _ => new Oid(friendlyName).Value, 
            };
        }
        AsnWriter asnWriter = new AsnWriter(AsnEncodingRules.DER);
        asnWriter.WriteObjectIdentifier(text);
        byte[] rawData = asnWriter.Encode();
        byte[] array = new byte[1 + eCParameters.Q.X.Length + eCParameters.Q.Y.Length];
        array[0] = 4;
        Buffer.BlockCopy(eCParameters.Q.X, 0, array, 1, eCParameters.Q.X.Length);
        Buffer.BlockCopy(eCParameters.Q.Y, 0, array, 1 + eCParameters.Q.X.Length, eCParameters.Q.Y.Length);
        Oid ecPublicKeyOid = System.Security.Cryptography.Oids.EcPublicKeyOid;
        return new PublicKey(ecPublicKeyOid, new AsnEncodedData(ecPublicKeyOid, rawData), new AsnEncodedData(ecPublicKeyOid, array));
    }
}