stuff

Femto.Modules.Auth/Models/Password.cs

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+using System.Text;
+using Geralt;
+using JetBrains.Annotations;
+
+namespace Femto.Modules.Auth.Models;
+
+internal class Password
+{
+    private const int Iterations = 3;
+    private const int MemorySize = 67108864;
+    
+    public byte[] Hash { get; private set; }
+    
+    public byte[] Salt { get; private set; }
+    
+    [UsedImplicitly]
+    private Password() {}
+    
+    public Password(string password)
+    {
+        this.Salt = ComputeSalt();
+        this.Hash = ComputePasswordHash(password, Salt);
+    }
+
+    public bool Check(string password)
+    {
+        var matches = Argon2id.VerifyHash(
+            Hash,
+            Combine(password, Salt)
+        );
+
+        if (!matches)
+            return false;
+
+        if (Argon2id.NeedsRehash(Hash, Iterations, MemorySize))
+        {
+            this.Salt = ComputeSalt();
+            this.Hash = ComputePasswordHash(password, Salt);
+        }
+
+        return true;
+    }
+    
+    private static byte[] ComputeSalt() => System.Security.Cryptography.RandomNumberGenerator.GetBytes(32);
+    
+    private static byte[] ComputePasswordHash(string password, byte[] salt)
+    {
+        var hash = new byte[128];
+        try
+        {
+            Argon2id.ComputeHash(hash, Combine(password, salt), Iterations, MemorySize);
+        }
+        catch (Exception e)
+        {
+            throw new SetPasswordError("Failed to hash password", e);
+        }
+
+        return hash;
+    }
+
+    private static byte[] Combine(string password, byte[] salt)
+    {
+        var passwordBytes = Encoding.UTF8.GetBytes(password);
+        var hashInput = new byte[passwordBytes.Length + salt.Length];
+        passwordBytes.CopyTo(hashInput, 0);
+        salt.CopyTo(hashInput, passwordBytes.Length);
+        
+        return hashInput;
+    }
+}