ChaCha20Poly1305.cs

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using System.Diagnostics.CodeAnalysis;
using System.Runtime.Versioning;
using Internal.Cryptography;
using Internal.NativeCrypto;
 
namespace System.Security.Cryptography;
 
[UnsupportedOSPlatform("browser")]
[UnsupportedOSPlatform("ios")]
[UnsupportedOSPlatform("tvos")]
public sealed class ChaCha20Poly1305 : IDisposable
{
    private SafeKeyHandle _keyHandle;
 
    public static bool IsSupported => BCryptAeadHandleCache.IsChaCha20Poly1305Supported;
 
    public ChaCha20Poly1305(ReadOnlySpan<byte> key)
    {
        ThrowIfNotSupported();
        CheckKeySize(key.Length);
        ImportKey(key);
    }
 
    public ChaCha20Poly1305(byte[] key)
    {
        ThrowIfNotSupported();
        if (key == null)
        {
            throw new ArgumentNullException("key");
        }
        CheckKeySize(key.Length);
        ImportKey(key);
    }
 
    private static void CheckKeySize(int keySizeInBytes)
    {
        if (keySizeInBytes != 32)
        {
            throw new CryptographicException(System.SR.Cryptography_InvalidKeySize);
        }
    }
 
    public void Encrypt(byte[] nonce, byte[] plaintext, byte[] ciphertext, byte[] tag, byte[]? associatedData = null)
    {
        AeadCommon.CheckArgumentsForNull(nonce, plaintext, ciphertext, tag);
        Encrypt((ReadOnlySpan<byte>)nonce, (ReadOnlySpan<byte>)plaintext, (Span<byte>)ciphertext, (Span<byte>)tag, (ReadOnlySpan<byte>)associatedData);
    }
 
    public void Encrypt(ReadOnlySpan<byte> nonce, ReadOnlySpan<byte> plaintext, Span<byte> ciphertext, Span<byte> tag, ReadOnlySpan<byte> associatedData = default(ReadOnlySpan<byte>))
    {
        CheckParameters(plaintext, ciphertext, nonce, tag);
        EncryptCore(nonce, plaintext, ciphertext, tag, associatedData);
    }
 
    public void Decrypt(byte[] nonce, byte[] ciphertext, byte[] tag, byte[] plaintext, byte[]? associatedData = null)
    {
        AeadCommon.CheckArgumentsForNull(nonce, plaintext, ciphertext, tag);
        Decrypt((ReadOnlySpan<byte>)nonce, (ReadOnlySpan<byte>)ciphertext, (ReadOnlySpan<byte>)tag, (Span<byte>)plaintext, (ReadOnlySpan<byte>)associatedData);
    }
 
    public void Decrypt(ReadOnlySpan<byte> nonce, ReadOnlySpan<byte> ciphertext, ReadOnlySpan<byte> tag, Span<byte> plaintext, ReadOnlySpan<byte> associatedData = default(ReadOnlySpan<byte>))
    {
        CheckParameters(plaintext, ciphertext, nonce, tag);
        DecryptCore(nonce, ciphertext, tag, plaintext, associatedData);
    }
 
    private static void CheckParameters(ReadOnlySpan<byte> plaintext, ReadOnlySpan<byte> ciphertext, ReadOnlySpan<byte> nonce, ReadOnlySpan<byte> tag)
    {
        if (plaintext.Length != ciphertext.Length)
        {
            throw new ArgumentException(System.SR.Cryptography_PlaintextCiphertextLengthMismatch);
        }
        if (nonce.Length != 12)
        {
            throw new ArgumentException(System.SR.Cryptography_InvalidNonceLength, "nonce");
        }
        if (tag.Length != 16)
        {
            throw new ArgumentException(System.SR.Cryptography_InvalidTagLength, "tag");
        }
    }
 
    private static void ThrowIfNotSupported()
    {
        if (!IsSupported)
        {
            throw new PlatformNotSupportedException(System.SR.Format(System.SR.Cryptography_AlgorithmNotSupported, "ChaCha20Poly1305"));
        }
    }
 
    [MemberNotNull("_keyHandle")]
    private void ImportKey(ReadOnlySpan<byte> key)
    {
        _keyHandle = global::Interop.BCrypt.BCryptImportKey(BCryptAeadHandleCache.ChaCha20Poly1305, key);
    }
 
    private void EncryptCore(ReadOnlySpan<byte> nonce, ReadOnlySpan<byte> plaintext, Span<byte> ciphertext, Span<byte> tag, ReadOnlySpan<byte> associatedData = default(ReadOnlySpan<byte>))
    {
        AeadCommon.Encrypt(_keyHandle, nonce, associatedData, plaintext, ciphertext, tag);
    }
 
    private void DecryptCore(ReadOnlySpan<byte> nonce, ReadOnlySpan<byte> ciphertext, ReadOnlySpan<byte> tag, Span<byte> plaintext, ReadOnlySpan<byte> associatedData = default(ReadOnlySpan<byte>))
    {
        AeadCommon.Decrypt(_keyHandle, nonce, associatedData, ciphertext, tag, plaintext, clearPlaintextOnFailure: true);
    }
 
    public void Dispose()
    {
        _keyHandle.Dispose();
    }
}