Implement IKeyManager

Akari.Prototype.Server/Utils/Security.cs

@@ -1,6 +1,7 @@
 using Isopoh.Cryptography.Argon2;
 using Isopoh.Cryptography.SecureArray;
 using System;
+using System.Buffers.Binary;
 using System.Collections.Generic;
 using System.Linq;
 using System.Security.Cryptography;
@@ -75,5 +76,60 @@ namespace Akari.Prototype.Server.Utils
         {
             return Argon2idDeriveBytes(Encoding.UTF8.GetBytes(password), Encoding.UTF8.GetBytes(salt), length, clear, threads);
         }
+
+        // Source: https://stackoverflow.com/a/60891115/7465768
+        public static byte[] AesGcmEncrypt(AesGcm key, Span<byte> plain)
+        {
+            // Get parameter sizes
+            int nonceSize = AesGcm.NonceByteSizes.MaxSize;
+            int tagSize = AesGcm.TagByteSizes.MaxSize;
+            int cipherSize = plain.Length;
+
+            // We write everything into one big array for easier encoding
+            int encryptedDataLength = 4 + nonceSize + 4 + tagSize + cipherSize;
+            Span<byte> encryptedData = encryptedDataLength < 1024
+                                     ? stackalloc byte[encryptedDataLength]
+                                     : new byte[encryptedDataLength];
+
+            // Copy parameters
+            BinaryPrimitives.WriteInt32LittleEndian(encryptedData.Slice(0, 4), nonceSize);
+            BinaryPrimitives.WriteInt32LittleEndian(encryptedData.Slice(4 + nonceSize, 4), tagSize);
+
+            var nonce = encryptedData.Slice(4, nonceSize);
+            var tag = encryptedData.Slice(4 + nonceSize + 4, tagSize);
+            var cipherBytes = encryptedData.Slice(4 + nonceSize + 4 + tagSize, cipherSize);
+
+            // Generate secure nonce
+            RandomNumberGenerator.Fill(nonce);
+
+            // Encrypt
+            key.Encrypt(nonce, plain, cipherBytes, tag);
+
+            // Encode for transmission
+            return encryptedData.ToArray();
+        }
+
+        public static byte[] AesGcmDecrypt(AesGcm key, Span<byte> encryptedData)
+        {
+            // Extract parameter sizes
+            int nonceSize = BinaryPrimitives.ReadInt32LittleEndian(encryptedData.Slice(0, 4));
+            int tagSize = BinaryPrimitives.ReadInt32LittleEndian(encryptedData.Slice(4 + nonceSize, 4));
+            int cipherSize = encryptedData.Length - 4 - nonceSize - 4 - tagSize;
+
+            // Extract parameters
+            var nonce = encryptedData.Slice(4, nonceSize);
+            var tag = encryptedData.Slice(4 + nonceSize + 4, tagSize);
+            var cipherBytes = encryptedData.Slice(4 + nonceSize + 4 + tagSize, cipherSize);
+
+            // Decrypt
+            Span<byte> plainBytes = cipherSize < 1024
+                                  ? stackalloc byte[cipherSize]
+                                  : new byte[cipherSize];
+
+            key.Decrypt(nonce, cipherBytes, tag, plainBytes);
+
+            // Convert plain bytes back into string
+            return plainBytes.ToArray();
+        }
     }
 }