UniversalCryptoDecryptor.cs

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using System;
using System.Security.Cryptography;
 
namespace Internal.Cryptography;
 
internal sealed class UniversalCryptoDecryptor : Internal.Cryptography.UniversalCryptoTransform
{
    private byte[] _heldoverCipher;
 
    private bool DepaddingRequired
    {
        get
        {
            switch (base.PaddingMode)
            {
            case PaddingMode.PKCS7:
            case PaddingMode.ANSIX923:
            case PaddingMode.ISO10126:
                return true;
            case PaddingMode.None:
            case PaddingMode.Zeros:
                return false;
            default:
                throw new CryptographicException(System.SR.Cryptography_UnknownPaddingMode);
            }
        }
    }
 
    public UniversalCryptoDecryptor(PaddingMode paddingMode, Internal.Cryptography.BasicSymmetricCipher basicSymmetricCipher)
        : base(paddingMode, basicSymmetricCipher)
    {
    }
 
    protected override int UncheckedTransformBlock(ReadOnlySpan<byte> inputBuffer, Span<byte> outputBuffer)
    {
        int num = 0;
        if (DepaddingRequired)
        {
            if (_heldoverCipher != null)
            {
                int num2 = base.BasicSymmetricCipher.Transform(_heldoverCipher, outputBuffer);
                outputBuffer = outputBuffer.Slice(num2);
                num += num2;
            }
            else
            {
                _heldoverCipher = new byte[base.InputBlockSize];
            }
            inputBuffer.Slice(inputBuffer.Length - _heldoverCipher.Length).CopyTo(_heldoverCipher);
            inputBuffer = inputBuffer.Slice(0, inputBuffer.Length - _heldoverCipher.Length);
        }
        if (inputBuffer.Length > 0)
        {
            num += base.BasicSymmetricCipher.Transform(inputBuffer, outputBuffer);
        }
        return num;
    }
 
    protected unsafe override int UncheckedTransformFinalBlock(ReadOnlySpan<byte> inputBuffer, Span<byte> outputBuffer)
    {
        if (inputBuffer.Length % base.PaddingSizeBytes != 0)
        {
            throw new CryptographicException(System.SR.Cryptography_PartialBlock);
        }
        byte[] array = null;
        int num = 0;
        try
        {
            Span<byte> span;
            ReadOnlySpan<byte> input;
            if (_heldoverCipher == null)
            {
                num = inputBuffer.Length;
                array = System.Security.Cryptography.CryptoPool.Rent(inputBuffer.Length);
                span = array.AsSpan(0, inputBuffer.Length);
                input = inputBuffer;
            }
            else
            {
                num = _heldoverCipher.Length + inputBuffer.Length;
                array = System.Security.Cryptography.CryptoPool.Rent(num);
                span = array.AsSpan(0, num);
                _heldoverCipher.AsSpan().CopyTo(span);
                inputBuffer.CopyTo(span.Slice(_heldoverCipher.Length));
                input = span;
            }
            int num2 = 0;
            fixed (byte* ptr = span)
            {
                Span<byte> span2 = span[..base.BasicSymmetricCipher.TransformFinal(input, span)];
                if (span2.Length > 0)
                {
                    num2 = GetPaddingLength(span2);
                    span2.Slice(0, num2).CopyTo(outputBuffer);
                }
            }
            Reset();
            return num2;
        }
        finally
        {
            if (array != null)
            {
                System.Security.Cryptography.CryptoPool.Return(array, num);
            }
        }
    }
 
    protected unsafe override byte[] UncheckedTransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)
    {
        if (DepaddingRequired)
        {
            byte[] array = System.Security.Cryptography.CryptoPool.Rent(inputCount + base.InputBlockSize);
            int num = 0;
            fixed (byte* ptr = array)
            {
                try
                {
                    num = UncheckedTransformFinalBlock(inputBuffer.AsSpan(inputOffset, inputCount), array);
                    return array.AsSpan(0, num).ToArray();
                }
                finally
                {
                    System.Security.Cryptography.CryptoPool.Return(array, num);
                }
            }
        }
        byte[] array2 = GC.AllocateUninitializedArray<byte>(inputCount);
        int num2 = UncheckedTransformFinalBlock(inputBuffer.AsSpan(inputOffset, inputCount), array2);
        return array2;
    }
 
    protected sealed override void Dispose(bool disposing)
    {
        if (disposing)
        {
            byte[] heldoverCipher = _heldoverCipher;
            _heldoverCipher = null;
            if (heldoverCipher != null)
            {
                Array.Clear(heldoverCipher);
            }
        }
        base.Dispose(disposing);
    }
 
    private void Reset()
    {
        if (_heldoverCipher != null)
        {
            Array.Clear(_heldoverCipher);
            _heldoverCipher = null;
        }
    }
 
    private int GetPaddingLength(ReadOnlySpan<byte> block)
    {
        int num = 0;
        switch (base.PaddingMode)
        {
        case PaddingMode.ANSIX923:
        {
            num = block[^1];
            if (num <= 0 || num > base.InputBlockSize)
            {
                throw new CryptographicException(System.SR.Cryptography_InvalidPadding);
            }
            for (int j = block.Length - num; j < block.Length - 1; j++)
            {
                if (block[j] != 0)
                {
                    throw new CryptographicException(System.SR.Cryptography_InvalidPadding);
                }
            }
            break;
        }
        case PaddingMode.ISO10126:
            num = block[^1];
            if (num <= 0 || num > base.InputBlockSize)
            {
                throw new CryptographicException(System.SR.Cryptography_InvalidPadding);
            }
            break;
        case PaddingMode.PKCS7:
        {
            num = block[^1];
            if (num <= 0 || num > base.InputBlockSize)
            {
                throw new CryptographicException(System.SR.Cryptography_InvalidPadding);
            }
            for (int i = block.Length - num; i < block.Length - 1; i++)
            {
                if (block[i] != num)
                {
                    throw new CryptographicException(System.SR.Cryptography_InvalidPadding);
                }
            }
            break;
        }
        case PaddingMode.None:
        case PaddingMode.Zeros:
            num = 0;
            break;
        default:
            throw new CryptographicException(System.SR.Cryptography_UnknownPaddingMode);
        }
        return block.Length - num;
    }
}