⚗️ Activity pub

DysonNetwork.Sphere/ActivityPub/ActivityPubKeyService.cs

@@ -0,0 +1,91 @@
+using System.Security.Cryptography;
+using System.Security.Cryptography.X509Certificates;
+using System.Text;
+
+namespace DysonNetwork.Sphere.ActivityPub;
+
+public class ActivityPubKeyService(ILogger<ActivityPubKeyService> logger)
+{
+    public (string privateKeyPem, string publicKeyPem) GenerateKeyPair()
+    {
+        using var rsa = RSA.Create(2048);
+        
+        var privateKey = rsa.ExportRSAPrivateKey();
+        var publicKey = rsa.ExportRSAPublicKey();
+        
+        var privateKeyPem = ConvertToPem(privateKey, "RSA PRIVATE KEY");
+        var publicKeyPem = ConvertToPem(publicKey, "PUBLIC KEY");
+        
+        logger.LogInformation("Generated new RSA key pair for ActivityPub");
+        
+        return (privateKeyPem, publicKeyPem);
+    }
+
+    public string Sign(string privateKeyPem, string dataToSign)
+    {
+        using var rsa = CreateRsaFromPrivateKeyPem(privateKeyPem);
+        var signature = rsa.SignData(
+            Encoding.UTF8.GetBytes(dataToSign),
+            HashAlgorithmName.SHA256,
+            RSASignaturePadding.Pkcs1
+        );
+        return Convert.ToBase64String(signature);
+    }
+
+    public bool Verify(string publicKeyPem, string data, string signatureBase64)
+    {
+        try
+        {
+            using var rsa = CreateRsaFromPublicKeyPem(publicKeyPem);
+            var signature = Convert.FromBase64String(signatureBase64);
+            return rsa.VerifyData(
+                Encoding.UTF8.GetBytes(data),
+                signature,
+                HashAlgorithmName.SHA256,
+                RSASignaturePadding.Pkcs1
+            );
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "Failed to verify signature");
+            return false;
+        }
+    }
+
+    private static string ConvertToPem(byte[] keyData, string keyType)
+    {
+        var sb = new StringBuilder();
+        sb.AppendLine($"-----BEGIN {keyType}-----");
+        sb.AppendLine(Convert.ToBase64String(keyData));
+        sb.AppendLine($"-----END {keyType}-----");
+        return sb.ToString();
+    }
+
+    private static RSA CreateRsaFromPrivateKeyPem(string privateKeyPem)
+    {
+        var rsa = RSA.Create();
+        
+        var lines = privateKeyPem.Split('\n')
+            .Where(line => !line.StartsWith("-----") && !string.IsNullOrWhiteSpace(line))
+            .ToArray();
+        
+        var keyBytes = Convert.FromBase64String(string.Join("", lines));
+        rsa.ImportRSAPrivateKey(keyBytes, out _);
+        
+        return rsa;
+    }
+
+    private static RSA CreateRsaFromPublicKeyPem(string publicKeyPem)
+    {
+        var rsa = RSA.Create();
+        
+        var lines = publicKeyPem.Split('\n')
+            .Where(line => !line.StartsWith("-----") && !string.IsNullOrWhiteSpace(line))
+            .ToArray();
+        
+        var keyBytes = Convert.FromBase64String(string.Join("", lines));
+        rsa.ImportRSAPublicKey(keyBytes, out _);
+        
+        return rsa;
+    }
+}