Saving

PrivaPub/StaticServices/PasswordHasher.cs

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+using Microsoft.Extensions.Options;
+
+using System.Security.Cryptography;
+
+namespace PrivaPub.StaticServices
+{
+	public sealed class PasswordHasher : IPasswordHasher
+	{
+		private const int SaltSize = 16;
+		private const int KeySize = 32;
+		private HashingOptions Options { get; }
+
+		public PasswordHasher(IOptionsMonitor<HashingOptions> options)
+		{
+			Options = options.CurrentValue;
+		}
+
+		public (bool verified, bool needsUpgrade) Check(string hash, string password)
+		{
+			var parts = hash.Split('~', 3);
+
+			if (parts.Length != 3)
+				throw new FormatException("Unexpected hash format.");
+
+			var iterations = Convert.ToInt32(parts[2]);
+			var salt = Convert.FromBase64String(parts[1]);
+			var key = Convert.FromBase64String(parts[0]);
+
+			var needsUpgrade = iterations != Options.Iterations;
+
+			using (var algorithm = new Rfc2898DeriveBytes(password, salt, iterations, HashAlgorithmName.SHA512))
+			{
+				var keyToCheck = algorithm.GetBytes(KeySize);
+				var verified = keyToCheck.SequenceEqual(key);
+				return (verified, needsUpgrade);
+			}
+		}
+
+		public string Hash(string password)
+		{
+			using (var algorithm = new Rfc2898DeriveBytes(password, SaltSize, Options.Iterations, HashAlgorithmName.SHA512))
+			{
+				var key = Convert.ToBase64String(algorithm.GetBytes(KeySize));
+				var salt = Convert.ToBase64String(algorithm.Salt);
+				return $"{key}~{salt}~{Options.Iterations}";
+			}
+		}
+	}
+
+	public sealed class HashingOptions
+	{
+		public int Iterations { get; set; } = 9789;
+	}
+}