ini

Utility/RsaKeyProvider.cs

@@ -0,0 +1,53 @@
+using System.Security.Cryptography;
+using System.Text;
+using Microsoft.IdentityModel.Tokens;
+
+namespace AuthHex.Utility;
+
+public class RsaKeyProvider
+{
+    private readonly RSA _rsa;
+
+    public RsaKeyProvider(string privateKeyXml)
+    {
+        _rsa = RSA.Create();
+        _rsa.FromXmlString(privateKeyXml);
+    }
+
+    public RsaSecurityKey GetPrivateKey()
+    {
+        var key = new RsaSecurityKey(_rsa);
+        var publicParameters = _rsa.ExportParameters(false);
+        key.KeyId = ComputeKeyId(publicParameters);
+        return key;
+    }
+
+    public RsaSecurityKey GetPublicKey()
+    {
+        var publicKeyRsa = RSA.Create();
+        var publicParameters = _rsa.ExportParameters(false);
+        publicKeyRsa.ImportParameters(publicParameters);
+
+        var key = new RsaSecurityKey(publicKeyRsa);
+        key.KeyId = ComputeKeyId(publicParameters);
+        return key;
+    }
+
+    private static string ComputeKeyId(RSAParameters publicParameters)
+    {
+        var modulus = publicParameters.Modulus ?? Array.Empty<byte>();
+        var exponent = publicParameters.Exponent ?? Array.Empty<byte>();
+        var payload = $"{Convert.ToBase64String(modulus)}.{Convert.ToBase64String(exponent)}";
+
+        var hash = SHA256.HashData(Encoding.UTF8.GetBytes(payload));
+        return Base64UrlEncoder.Encode(hash);
+    }
+
+    public static (string privateKey, string publicKey) GenerateKeys()
+    {
+        using var rsa = RSA.Create(2048);
+        var privateKey = rsa.ToXmlString(true);  // includes private key
+        var publicKey = rsa.ToXmlString(false);   // public key only
+        return (privateKey, publicKey);
+    }
+}