1 files changed, 234 insertions, 0 deletions
diff --git a/wrappers/dotnet/VNLib.Utils.Cryptography.Noscrypt/src/NostrEncryptedMessage.cs b/wrappers/dotnet/VNLib.Utils.Cryptography.Noscrypt/src/NostrEncryptedMessage.cs
new file mode 100644
index 0000000..c70839c
--- /dev/null
+++ b/wrappers/dotnet/VNLib.Utils.Cryptography.Noscrypt/src/NostrEncryptedMessage.cs
@@ -0,0 +1,234 @@
+// 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.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+using VNLib.Utils.Extensions;
+using VNLib.Utils.Memory;
+
+using static VNLib.Utils.Cryptography.Noscrypt.LibNoscrypt;
+
+namespace VNLib.Utils.Cryptography.Noscrypt
+{
+
+    public sealed class NostrEncryptedMessage(IEncryptionVersion version, INostrCrypto lib) : VnDisposeable
+    {
+        private readonly INostrCrypto library = lib;
+
+        private NCSecretKey _fromKey;
+        private NCPublicKey _toKey;       
+        private Buffer32 _nonce32;
+
+        /// <summary>
+        /// The message encryption version used by this instance
+        /// </summary>
+        public uint Version { get; } = version.Version;
+
+        /// <summary>
+        /// The message nonce created during encryption event
+        /// </summary>
+        public unsafe Span<byte> Nonce
+        {
+            get
+            {
+                Debug.Assert(NC_ENCRYPTION_NONCE_SIZE == sizeof(Buffer32));
+                return MemoryMarshal.CreateSpan(ref GetNonceRef(), sizeof(Buffer32));
+            }
+        }
+
+        /// <summary>
+        /// Gets the size of the buffer required to encrypt the specified data size
+        /// </summary>
+        /// <param name="dataSize">The size of the message raw plaintext message to send</param>
+        /// <returns>The minimum number of bytes required for message encryption output</returns>
+        /// <exception cref="NotSupportedException"></exception>
+        public int GetOutputBufferSize(int dataSize) 
+            => version.CalcBufferSize(dataSize);
+
+        /// <summary>
+        /// Sets the encryption secret key for the message
+        /// </summary>
+        /// <param name="secKey">The secret key buffer</param>
+        /// <returns>The current instance for chaining</returns>
+        /// <exception cref="ArgumentException"></exception>
+        public NostrEncryptedMessage SetSecretKey(ReadOnlySpan<byte> secKey) 
+            => SetSecretKey(in NCUtil.AsSecretKey(secKey));
+
+        /// <summary>
+        /// Sets the encryption secret key for the message
+        /// </summary>
+        /// <param name="secKey">The secret key structure to copy</param>
+        /// <returns>The current instance for chaining</returns>
+        /// <exception cref="ArgumentException"></exception>
+        public NostrEncryptedMessage SetSecretKey(ref readonly NCSecretKey secKey)
+        {
+            MemoryUtil.CloneStruct(in secKey, ref _fromKey);
+            return this;
+        }
+
+        /// <summary>
+        /// Assigns the public key used to encrypt the message as the 
+        /// receiver of the message
+        /// </summary>
+        /// <param name="pubKey">The user's public key receiving the message</param>
+        /// <returns>The current instance for chaining</returns>
+        /// <exception cref="ArgumentException"></exception>
+        public NostrEncryptedMessage SetPublicKey(ReadOnlySpan<byte> pubKey) 
+            => SetPublicKey(in NCUtil.AsPublicKey(pubKey));
+
+        /// <summary>
+        /// Assigns the public key used to encrypt the message as the 
+        /// receiver of the message
+        /// </summary>
+        /// <param name="pubKey">The user's public key receiving the message</param>
+        /// <returns>The current instance for chaining</returns>
+        /// <exception cref="ArgumentException"></exception>
+        public NostrEncryptedMessage SetPublicKey(ref readonly NCPublicKey pubKey)
+        {
+            MemoryUtil.CloneStruct(in pubKey, ref _toKey);
+            return this;
+        }
+
+        /// <summary>
+        /// Assigns the nonce to the message. Must be <see cref="NC_ENCRYPTION_NONCE_SIZE"/>
+        /// in length
+        /// </summary>
+        /// <param name="nonce">The nonce value to copy</param>
+        /// <returns>The current instance for chaining</returns>
+        /// <exception cref="ArgumentException"></exception>
+        public NostrEncryptedMessage SetNonce(ReadOnlySpan<byte> nonce)
+        {
+            MemoryUtil.CopyStruct(nonce, ref _nonce32);
+            return this;
+        }
+
+        /// <summary>
+        /// Assigns a random nonce using the specified random source
+        /// </summary>
+        /// <param name="rng">The random source to genrate a random nonce from</param>
+        /// <returns>The current instance for chaining</returns>
+        public NostrEncryptedMessage SetRandomNonce(IRandomSource rng)
+        {
+            rng.GetRandomBytes(Nonce);
+            return this;
+        }
+
+        /// <summary>
+        /// Encrypts the plaintext message and writes the encrypted message to the
+        /// specified buffer, along with a 32 byte mac of the message
+        /// </summary>
+        /// <param name="plaintext">The plaintext data to encrypt</param>
+        /// <param name="message">The message output buffer to write encrypted data to</param>
+        /// <param name="macOut32">A buffer to write the computed message mac to</param>
+        /// <returns>The number of bytes writtn to the message output buffer</returns>
+        /// <remarks>
+        /// The message buffer must be at-least the size of the output buffer, and it is not 
+        /// initialized before the encryption operation.
+        /// </remarks>
+        /// <exception cref="ArgumentOutOfRangeException"></exception>
+        public int EncryptMessage(ReadOnlySpan<byte> plaintext, Span<byte> message, Span<byte> macOut32)
+        {
+            return Version switch
+            {
+                NC_ENC_VERSION_NIP44 => EncryptNip44(plaintext, message, macOut32),
+                _ => throw new NotSupportedException("NIP04 encryption is not supported"),
+            };
+        }
+
+        private int EncryptNip44(ReadOnlySpan<byte> plaintext, Span<byte> message, Span<byte> macOut32)
+        {
+            int payloadSize = GetOutputBufferSize(plaintext.Length);
+
+            ArgumentOutOfRangeException.ThrowIfZero(plaintext.Length, nameof(plaintext));
+            ArgumentOutOfRangeException.ThrowIfZero(message.Length, nameof(message));
+            ArgumentOutOfRangeException.ThrowIfLessThan(message.Length, payloadSize, nameof(message));
+            ArgumentOutOfRangeException.ThrowIfLessThan(macOut32.Length, NC_ENCRYPTION_MAC_SIZE, nameof(macOut32));
+
+            /*
+             * Alloc temp buffer to copy formatted payload to data to for the encryption
+             * operation. Encryption will write directly to the message buffer
+             */
+
+            using UnsafeMemoryHandle<byte> ptPayloadBuf = MemoryUtil.UnsafeAllocNearestPage<byte>(payloadSize, true);
+            using UnsafeMemoryHandle<byte> hmacKeyBuf = MemoryUtil.UnsafeAlloc<byte>(NC_HMAC_KEY_SIZE, true);
+            Debug.Assert(hmacKeyBuf.Length == NC_HMAC_KEY_SIZE);
+
+            Nip44Util.FormatBuffer(plaintext, ptPayloadBuf.Span, false);
+
+            library.EncryptNip44(
+                in _fromKey,
+                in _toKey,
+                in GetNonceRef(),
+                in ptPayloadBuf.GetReference(),
+                ref MemoryMarshal.GetReference(message),
+                (uint)payloadSize,                  //IMPORTANT: Format buffer will pad the buffer to the exact size
+                ref hmacKeyBuf.GetReference()       //Must set the hmac key buffer
+            );
+
+            //Safe to clear the plain text copy buffer
+            MemoryUtil.InitializeBlock(
+                ref ptPayloadBuf.GetReference(),
+                ptPayloadBuf.GetIntLength()
+            );
+
+
+            //Compute message mac, key should be set by the encryption operation
+            library.ComputeMac(
+                in hmacKeyBuf.GetReference(),
+                in MemoryMarshal.GetReference(message),
+                (uint)payloadSize,  //Again set exact playload size
+                ref MemoryMarshal.GetReference(macOut32)
+            );
+
+            //Safe to clear the hmac key buffer
+            MemoryUtil.InitializeBlock(
+                ref hmacKeyBuf.GetReference(),
+                hmacKeyBuf.GetIntLength()
+            );
+
+            return payloadSize;
+        }
+
+        private ref byte GetNonceRef() => ref Unsafe.As<Buffer32, byte>(ref _nonce32);      
+
+        protected override void Free()
+        {
+            //Zero all internal memory
+            MemoryUtil.ZeroStruct(ref _fromKey);
+            MemoryUtil.ZeroStruct(ref _toKey);
+            MemoryUtil.ZeroStruct(ref _nonce32);
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref="NostrEncryptedMessage"/> with the nip44 encryption
+        /// method.
+        /// </summary>
+        /// <param name="lib">The nostr crypto implementation instance to use</param>
+        /// <returns>The intialzied message instance</returns>
+        public static NostrEncryptedMessage CreateNip44Cipher(INostrCrypto lib) 
+            => new(NCNip44EncryptionVersion.Instance, lib);
+       
+
+        [StructLayout(LayoutKind.Sequential, Size = 32)]
+        unsafe struct Buffer32
+        {
+            fixed byte value[32];
+        }
+    }
+
+}