UniversalCryptoEncryptor.cs

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using System;
using System.Security.Cryptography;
 
namespace Internal.Cryptography;
 
internal sealed class UniversalCryptoEncryptor : UniversalCryptoTransform
{
    public UniversalCryptoEncryptor(PaddingMode paddingMode, BasicSymmetricCipher basicSymmetricCipher)
        : base(paddingMode, basicSymmetricCipher)
    {
    }
 
    protected override int UncheckedTransformBlock(ReadOnlySpan<byte> inputBuffer, Span<byte> outputBuffer)
    {
        return base.BasicSymmetricCipher.Transform(inputBuffer, outputBuffer);
    }
 
    protected override int UncheckedTransformFinalBlock(ReadOnlySpan<byte> inputBuffer, Span<byte> outputBuffer)
    {
        int length = PadBlock(inputBuffer, outputBuffer);
        return base.BasicSymmetricCipher.TransformFinal(outputBuffer.Slice(0, length), outputBuffer);
    }
 
    protected override byte[] UncheckedTransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)
    {
        byte[] array = GC.AllocateUninitializedArray<byte>(GetCiphertextLength(inputCount));
        int num = UncheckedTransformFinalBlock(inputBuffer.AsSpan(inputOffset, inputCount), array);
        return array;
    }
 
    public override bool TransformOneShot(ReadOnlySpan<byte> input, Span<byte> output, out int bytesWritten)
    {
        int ciphertextLength = GetCiphertextLength(input.Length);
        if (output.Length < ciphertextLength)
        {
            bytesWritten = 0;
            return false;
        }
        Span<byte> span = output[..PadBlock(input, output)];
        bytesWritten = base.BasicSymmetricCipher.TransformFinal(span, span);
        return true;
    }
 
    private int GetCiphertextLength(int plaintextLength)
    {
        int result;
        int num = Math.DivRem(plaintextLength, base.PaddingSizeBytes, out result) * base.PaddingSizeBytes;
        switch (base.PaddingMode)
        {
        case PaddingMode.None:
            if (result != 0)
            {
                throw new CryptographicException(System.SR.Cryptography_PartialBlock);
            }
            goto IL_004c;
        case PaddingMode.Zeros:
            if (result == 0)
            {
                goto IL_004c;
            }
            goto case PaddingMode.PKCS7;
        case PaddingMode.PKCS7:
        case PaddingMode.ANSIX923:
        case PaddingMode.ISO10126:
            return checked(num + base.PaddingSizeBytes);
        default:
            {
                throw new CryptographicException(System.SR.Cryptography_UnknownPaddingMode);
            }
            IL_004c:
            return plaintextLength;
        }
    }
 
    private int PadBlock(ReadOnlySpan<byte> block, Span<byte> destination)
    {
        int length = block.Length;
        int num = length % base.PaddingSizeBytes;
        int num2 = base.PaddingSizeBytes - num;
        switch (base.PaddingMode)
        {
        case PaddingMode.None:
            if (num != 0)
            {
                throw new CryptographicException(System.SR.Cryptography_PartialBlock);
            }
            if (destination.Length < length)
            {
                throw new ArgumentException(System.SR.Argument_DestinationTooShort, "destination");
            }
            block.CopyTo(destination);
            return length;
        case PaddingMode.ANSIX923:
        {
            int num4 = length + num2;
            if (destination.Length < num4)
            {
                throw new ArgumentException(System.SR.Argument_DestinationTooShort, "destination");
            }
            block.CopyTo(destination);
            destination.Slice(length, num2 - 1).Clear();
            destination[length + num2 - 1] = (byte)num2;
            return num4;
        }
        case PaddingMode.ISO10126:
        {
            int num6 = length + num2;
            if (destination.Length < num6)
            {
                throw new ArgumentException(System.SR.Argument_DestinationTooShort, "destination");
            }
            block.CopyTo(destination);
            RandomNumberGenerator.Fill(destination.Slice(length, num2 - 1));
            destination[length + num2 - 1] = (byte)num2;
            return num6;
        }
        case PaddingMode.PKCS7:
        {
            int num5 = length + num2;
            if (destination.Length < num5)
            {
                throw new ArgumentException(System.SR.Argument_DestinationTooShort, "destination");
            }
            block.CopyTo(destination);
            destination.Slice(length, num2).Fill((byte)num2);
            return num5;
        }
        case PaddingMode.Zeros:
        {
            if (num2 == base.PaddingSizeBytes)
            {
                num2 = 0;
            }
            int num3 = length + num2;
            if (destination.Length < num3)
            {
                throw new ArgumentException(System.SR.Argument_DestinationTooShort, "destination");
            }
            block.CopyTo(destination);
            destination.Slice(length, num2).Clear();
            return num3;
        }
        default:
            throw new CryptographicException(System.SR.Cryptography_UnknownPaddingMode);
        }
    }
}