Add DeviceTokenService (random token, SHA-256 hash, fixed-time verify)

2026-06-11 18:48:39 +00:00
parent 3e9c245bb3
commit b862bf6f0f
2 changed files with 72 additions and 0 deletions
@@ -0,0 +1,36 @@
+using System.Security.Cryptography;
+using System.Text;
+
+namespace backend.Devices;
+
+public class DeviceTokenService
+{
+    public (string Plaintext, string Hash) Generate()
+    {
+        Span<byte> bytes = stackalloc byte[32];
+        RandomNumberGenerator.Fill(bytes);
+        var plaintext = Base64UrlEncode(bytes);
+        return (plaintext, Hash(plaintext));
+    }
+
+    public string Hash(string plaintext)
+    {
+        Span<byte> hash = stackalloc byte[32];
+        SHA256.HashData(Encoding.UTF8.GetBytes(plaintext), hash);
+        return Convert.ToHexString(hash);
+    }
+
+    public bool Verify(string plaintext, string expectedHash)
+    {
+        var actual = Hash(plaintext);
+        return CryptographicOperations.FixedTimeEquals(
+            Encoding.UTF8.GetBytes(actual),
+            Encoding.UTF8.GetBytes(expectedHash));
+    }
+
+    private static string Base64UrlEncode(ReadOnlySpan<byte> bytes)
+        => Convert.ToBase64String(bytes)
+            .TrimEnd('=')
+            .Replace('+', '-')
+            .Replace('/', '_');
+}