1 files changed, 90 insertions, 0 deletions
diff --git a/Plugins.Essentials/src/Accounts/INonce.cs b/Plugins.Essentials/src/Accounts/INonce.cs
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+++ b/Plugins.Essentials/src/Accounts/INonce.cs
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+/*
+* Copyright (c) 2022 Vaughn Nugent
+* 
+* Library: VNLib
+* Package: VNLib.Plugins.Essentials
+* File: INonce.cs 
+*
+* INonce.cs is part of VNLib.Plugins.Essentials which is part of the larger 
+* VNLib collection of libraries and utilities.
+*
+* VNLib.Plugins.Essentials 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.
+*
+* VNLib.Plugins.Essentials 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 VNLib.Utils;
+using VNLib.Utils.Memory;
+
+namespace VNLib.Plugins.Essentials.Accounts
+{
+    /// <summary>
+    /// Represents a object that performs storage and computation of nonce values
+    /// </summary>
+    public interface INonce
+    {
+        /// <summary>
+        /// Generates a random nonce for the current instance and 
+        /// returns a base32 encoded string.
+        /// </summary>
+        /// <param name="buffer">The buffer to write a copy of the nonce value to</param>
+        void ComputeNonce(Span<byte> buffer);
+        /// <summary>
+        /// Compares the raw nonce bytes to the current nonce to determine 
+        /// if the supplied nonce value is valid
+        /// </summary>
+        /// <param name="nonceBytes">The binary value of the nonce</param>
+        /// <returns>True if the nonce values are equal, flase otherwise</returns>
+        bool VerifyNonce(ReadOnlySpan<byte> nonceBytes);
+    }
+
+    /// <summary>
+    /// Provides INonce extensions for computing/verifying nonce values
+    /// </summary>
+    public static class NonceExtensions
+    {
+        /// <summary>
+        /// Computes a base32 nonce of the specified size and returns a string
+        /// representation
+        /// </summary>
+        /// <param name="nonce"></param>
+        /// <param name="size">The size (in bytes) of the nonce</param>
+        /// <returns>The base32 string of the computed nonce</returns>
+        public static string ComputeNonce<T>(this T nonce, int size) where T: INonce
+        {
+            //Alloc bin buffer
+            using UnsafeMemoryHandle<byte> buffer = Memory.UnsafeAlloc<byte>(size);
+            //Compute nonce
+            nonce.ComputeNonce(buffer.Span);
+            //Return base32 string
+            return VnEncoding.ToBase32String(buffer.Span, false);
+        }
+        /// <summary>
+        /// Compares the base32 encoded nonce value against the previously
+        /// generated nonce
+        /// </summary>
+        /// <param name="nonce"></param>
+        /// <param name="base32Nonce">The base32 encoded nonce string</param>
+        /// <returns>True if the nonce values are equal, flase otherwise</returns>
+        public static bool VerifyNonce<T>(this T nonce, ReadOnlySpan<char> base32Nonce) where T : INonce
+        {
+            //Alloc bin buffer
+            using UnsafeMemoryHandle<byte> buffer = Memory.UnsafeAlloc<byte>(base32Nonce.Length);
+            //Decode base32 nonce
+            ERRNO count = VnEncoding.TryFromBase32Chars(base32Nonce, buffer.Span);
+            //Verify nonce
+            return nonce.VerifyNonce(buffer.Span[..(int)count]);
+        }
+    }
+}