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// Copyright (C) 2024 Vaughn Nugent
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
using System;
using System.Threading;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using VNLib.Utils.Memory;
using VNLib.Utils.Cryptography.Noscrypt.Random;
using static VNLib.Utils.Cryptography.Noscrypt.NoscryptLibrary;
namespace VNLib.Utils.Cryptography.Noscrypt.Encryption
{
/// <summary>
/// The noscrypt util cipher wapper
/// </summary>
/// <param name="ctx"></param>
/// <param name="flags">Cipher creation flags</param>
/// <param name="version">The cipher specification version</param>
public sealed class NoscryptCipher(NCContext ctx, NoscryptCipherVersion version, NoscryptCipherFlags flags) : VnDisposeable
{
private IMemoryHandle<byte>? _ivBuffer;
private readonly nint _cipher = NCUtilCipher.Alloc(ctx, (uint)version, (uint)flags);
/// <summary>
/// The cipher standard version used by this instance
/// </summary>
public NoscryptCipherVersion Version => version;
/// <summary>
/// Gets the flags set for the cipher instance
/// </summary>
public uint GetFlags() => NCUtilCipher.GetFlags(ctx, _cipher);
/// <summary>
/// Gets the cipher's initilaization vector size (or nonce)
/// </summary>
/// <returns>The size of the IV in bytes</returns>
public int GetIvSize() => NCUtilCipher.GetIvSize(ctx, _cipher);
/// <summary>
/// Gets the internal heap buffer that holds the cipher's initalization
/// vector.
/// </summary>
/// <returns>The mutable span of the cipher's IV buffer</returns>
public Span<byte> IvBuffer
{
get => LazyInitializer.EnsureInitialized(ref _ivBuffer, AllocIvBuffer).Span;
}
/// <summary>
/// Sets the cipher's initialization vector to a random value using
/// the specified random source
/// </summary>
/// <param name="rng">The random source</param>
public void SetRandomIv(IRandomSource rng)
{
ArgumentNullException.ThrowIfNull(rng);
rng.GetRandomBytes(IvBuffer);
}
/// <summary>
/// Performs the cipher operation on the input data using the specified
/// local and remote keys.
/// </summary>
/// <param name="localKey">The secret key of the local user</param>
/// <param name="remoteKey">The public key of the remote user</param>
/// <param name="inputData">A pointer to the first byte in the buffer sequence</param>
/// <param name="inputSize">The size of the input buffer in bytes</param>
/// <exception cref="ArgumentNullException"></exception>
/// <remarks>
/// If the <see cref="NoscryptCipherFlags.Reusable"/> flag is
/// set, this function may be considered independent and called repeatedly.
/// </remarks>
public unsafe void Update(
ref readonly NCSecretKey localKey,
ref readonly NCPublicKey remoteKey,
ref readonly byte inputData,
uint inputSize
)
{
if (Unsafe.IsNullRef(in localKey))
{
throw new ArgumentNullException(nameof(localKey));
}
if (Unsafe.IsNullRef(in remoteKey))
{
throw new ArgumentNullException(nameof(remoteKey));
}
if (Unsafe.IsNullRef(in inputData))
{
throw new ArgumentNullException(nameof(inputData));
}
/*
* Initializing the cipher requires the context holding a pointer
* to the input data, so it has to be pinned in a fixed statment
* for the duration of the update operation.
*
* So init and update must be done as an atomic operation.
*
* If ciphers have the Reusable flag set this function may be called
* repeatedly. The results of this operation can be considered
* independent.
*/
fixed (byte* inputPtr = &inputData)
{
NCUtilCipher.InitCipher(ctx, _cipher, inputPtr, inputSize);
NCUtilCipher.Update(ctx, _cipher, in localKey, in remoteKey);
}
}
/// <summary>
/// Performs the cipher operation on the input data using the specified
/// local and remote keys.
/// </summary>
/// <param name="localKey">The secret key of the local user</param>
/// <param name="remoteKey">The public key of the remote user</param>
/// <param name="input">The buffer sequence to read the input data from</param>
/// <exception cref="ArgumentNullException"></exception>
public void Update(
ref readonly NCSecretKey localKey,
ref readonly NCPublicKey remoteKey,
ReadOnlySpan<byte> input
)
{
Update(
in localKey,
in remoteKey,
inputData: ref MemoryMarshal.GetReference(input), //If empty, null ref will throw
inputSize: (uint)input.Length
);
}
/// <summary>
/// Gets the size of the output buffer required to read the cipher output
/// </summary>
/// <returns>The size of the output in bytes</returns>
public int GetOutputSize() => checked((int)NCUtilCipher.GetOutputSize(ctx, _cipher));
/// <summary>
/// Reads the output data from the cipher into the specified buffer
/// </summary>
/// <param name="outputData">A reference to the first byte in the buffer sequence</param>
/// <param name="size">The size of the buffer sequence</param>
/// <returns>The number of bytes written to the buffer</returns>
/// <exception cref="ArgumentOutOfRangeException"></exception>
public int ReadOutput(ref byte outputData, int size)
{
ArgumentOutOfRangeException.ThrowIfLessThan(size, GetOutputSize());
return checked((int)NCUtilCipher.ReadOutput(ctx, _cipher, ref outputData, (uint)size));
}
/// <summary>
/// Reads the output data from the cipher into the specified buffer
/// </summary>
/// <param name="buffer">The buffer sequence to write output data to</param>
/// <returns>The number of bytes written to the buffer</returns>
/// <exception cref="ArgumentOutOfRangeException"></exception>
public int ReadOutput(Span<byte> buffer)
{
return ReadOutput(
ref MemoryMarshal.GetReference(buffer),
buffer.Length
);
}
private IMemoryHandle<byte> AllocIvBuffer()
{
//Use the context heap to allocate the internal iv buffer
MemoryHandle<byte> buffer = MemoryUtil.SafeAlloc<byte>(ctx.Heap, GetIvSize(), zero: true);
try
{
/*
* Assign the buffer reference to the cipher context
*
* NOTE: This pointer will be held as long as the cipher
* context is allocated. So the buffer must be held until
* the cipher is freed. Because of this an umnanaged heap
* buffer is required so we don't need to pin managed memory
* nor worry about the GC moving the buffer.
*/
NCUtilCipher.SetProperty(
ctx,
_cipher,
NC_ENC_SET_IV,
ref buffer.GetReference(),
(uint)buffer.Length
);
}
catch
{
buffer.Dispose();
throw;
}
return buffer;
}
///<inheritdoc/>
protected override void Free()
{
NCUtilCipher.Free(ctx, _cipher);
_ivBuffer?.Dispose();
}
}
}
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