RSAKeyFormatHelper.cs

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using System.Formats.Asn1;
using System.Security.Cryptography.Asn1;
 
namespace System.Security.Cryptography;
 
internal static class RSAKeyFormatHelper
{
    private static readonly string[] s_validOids = new string[1] { "1.2.840.113549.1.1.1" };
 
    internal static void FromPkcs1PrivateKey(ReadOnlyMemory<byte> keyData, in AlgorithmIdentifierAsn algId, out RSAParameters ret)
    {
        RSAPrivateKeyAsn rSAPrivateKeyAsn = RSAPrivateKeyAsn.Decode(keyData, AsnEncodingRules.BER);
        if (!algId.HasNullEquivalentParameters())
        {
            throw new CryptographicException(System.SR.Cryptography_Der_Invalid_Encoding);
        }
        if (rSAPrivateKeyAsn.Version > 0)
        {
            throw new CryptographicException(System.SR.Format(System.SR.Cryptography_RSAPrivateKey_VersionTooNew, rSAPrivateKeyAsn.Version, 0));
        }
        byte[] array = rSAPrivateKeyAsn.Modulus.ToByteArray(isUnsigned: true, isBigEndian: true);
        int length = (array.Length + 1) / 2;
        ret = new RSAParameters
        {
            Modulus = array,
            Exponent = rSAPrivateKeyAsn.PublicExponent.ToByteArray(isUnsigned: true, isBigEndian: true),
            D = rSAPrivateKeyAsn.PrivateExponent.ExportKeyParameter(array.Length),
            P = rSAPrivateKeyAsn.Prime1.ExportKeyParameter(length),
            Q = rSAPrivateKeyAsn.Prime2.ExportKeyParameter(length),
            DP = rSAPrivateKeyAsn.Exponent1.ExportKeyParameter(length),
            DQ = rSAPrivateKeyAsn.Exponent2.ExportKeyParameter(length),
            InverseQ = rSAPrivateKeyAsn.Coefficient.ExportKeyParameter(length)
        };
    }
 
    internal static void ReadRsaPublicKey(ReadOnlyMemory<byte> keyData, in AlgorithmIdentifierAsn algId, out RSAParameters ret)
    {
        RSAPublicKeyAsn rSAPublicKeyAsn = RSAPublicKeyAsn.Decode(keyData, AsnEncodingRules.BER);
        ret = new RSAParameters
        {
            Modulus = rSAPublicKeyAsn.Modulus.ToByteArray(isUnsigned: true, isBigEndian: true),
            Exponent = rSAPublicKeyAsn.PublicExponent.ToByteArray(isUnsigned: true, isBigEndian: true)
        };
    }
 
    internal static ReadOnlyMemory<byte> ReadSubjectPublicKeyInfo(ReadOnlyMemory<byte> source, out int bytesRead)
    {
        return KeyFormatHelper.ReadSubjectPublicKeyInfo(s_validOids, source, out bytesRead);
    }
 
    internal static ReadOnlyMemory<byte> ReadPkcs8(ReadOnlyMemory<byte> source, out int bytesRead)
    {
        return KeyFormatHelper.ReadPkcs8(s_validOids, source, out bytesRead);
    }
 
    internal static AsnWriter WriteSubjectPublicKeyInfo(ReadOnlySpan<byte> pkcs1PublicKey)
    {
        AsnWriter asnWriter = new AsnWriter(AsnEncodingRules.DER);
        asnWriter.PushSequence();
        WriteAlgorithmIdentifier(asnWriter);
        asnWriter.WriteBitString(pkcs1PublicKey);
        asnWriter.PopSequence();
        return asnWriter;
    }
 
    internal static AsnWriter WritePkcs8PrivateKey(ReadOnlySpan<byte> pkcs1PrivateKey, AsnWriter copyFrom = null)
    {
        AsnWriter asnWriter = new AsnWriter(AsnEncodingRules.BER);
        using (asnWriter.PushSequence())
        {
            asnWriter.WriteInteger(0L);
            WriteAlgorithmIdentifier(asnWriter);
            if (copyFrom != null)
            {
                using (asnWriter.PushOctetString())
                {
                    copyFrom.CopyTo(asnWriter);
                }
            }
            else
            {
                asnWriter.WriteOctetString(pkcs1PrivateKey);
            }
        }
        return asnWriter;
    }
 
    private static void WriteAlgorithmIdentifier(AsnWriter writer)
    {
        writer.PushSequence();
        writer.WriteObjectIdentifier("1.2.840.113549.1.1.1");
        writer.WriteNull();
        writer.PopSequence();
    }
 
    internal static AsnWriter WritePkcs1PublicKey(in RSAParameters rsaParameters)
    {
        if (rsaParameters.Modulus == null || rsaParameters.Exponent == null)
        {
            throw new CryptographicException(System.SR.Cryptography_InvalidRsaParameters);
        }
        AsnWriter asnWriter = new AsnWriter(AsnEncodingRules.DER);
        asnWriter.PushSequence();
        asnWriter.WriteKeyParameterInteger(rsaParameters.Modulus);
        asnWriter.WriteKeyParameterInteger(rsaParameters.Exponent);
        asnWriter.PopSequence();
        return asnWriter;
    }
 
    internal static AsnWriter WritePkcs1PrivateKey(in RSAParameters rsaParameters)
    {
        if (rsaParameters.Modulus == null || rsaParameters.Exponent == null)
        {
            throw new CryptographicException(System.SR.Cryptography_InvalidRsaParameters);
        }
        if (rsaParameters.D == null || rsaParameters.P == null || rsaParameters.Q == null || rsaParameters.DP == null || rsaParameters.DQ == null || rsaParameters.InverseQ == null)
        {
            throw new CryptographicException(System.SR.Cryptography_NotValidPrivateKey);
        }
        AsnWriter asnWriter = new AsnWriter(AsnEncodingRules.DER);
        asnWriter.PushSequence();
        asnWriter.WriteInteger(0L);
        asnWriter.WriteKeyParameterInteger(rsaParameters.Modulus);
        asnWriter.WriteKeyParameterInteger(rsaParameters.Exponent);
        asnWriter.WriteKeyParameterInteger(rsaParameters.D);
        asnWriter.WriteKeyParameterInteger(rsaParameters.P);
        asnWriter.WriteKeyParameterInteger(rsaParameters.Q);
        asnWriter.WriteKeyParameterInteger(rsaParameters.DP);
        asnWriter.WriteKeyParameterInteger(rsaParameters.DQ);
        asnWriter.WriteKeyParameterInteger(rsaParameters.InverseQ);
        asnWriter.PopSequence();
        return asnWriter;
    }
 
    internal static void ReadEncryptedPkcs8(ReadOnlySpan<byte> source, ReadOnlySpan<char> password, out int bytesRead, out RSAParameters key)
    {
        KeyFormatHelper.ReadEncryptedPkcs8(s_validOids, source, password, (KeyFormatHelper.KeyReader<RSAParameters>)FromPkcs1PrivateKey, out bytesRead, out key);
    }
 
    internal static void ReadEncryptedPkcs8(ReadOnlySpan<byte> source, ReadOnlySpan<byte> passwordBytes, out int bytesRead, out RSAParameters key)
    {
        KeyFormatHelper.ReadEncryptedPkcs8(s_validOids, source, passwordBytes, (KeyFormatHelper.KeyReader<RSAParameters>)FromPkcs1PrivateKey, out bytesRead, out key);
    }
}