Fix premature initialization of 'client crendentials'

Author: cincuranet

Provider/src/FirebirdSql.Data.FirebirdClient/Client/Managed/SspiHelper.cs

@@ -297,12 +297,6 @@ public SspiHelper(string securityPackage, string remotePrincipal)
 		{
 			_securityPackage = securityPackage;
 			_remotePrincipal = remotePrincipal;
-			_clientCredentials = new SecHandle();
-			var resCode = AcquireCredentialsHandle(null, securityPackage, SECPKG_CRED_OUTBOUND,
-				IntPtr.Zero, IntPtr.Zero, 0, IntPtr.Zero,
-				out _clientCredentials, out var expiry);
-			if (resCode != SEC_E_OK)
-				throw new Exception($"{nameof(AcquireCredentialsHandle)} failed");
 		}
 
 		#endregion
@@ -317,6 +311,7 @@ public byte[] InitializeClientSecurity()
 		{
 			EnsureDisposed();
 			CloseClientContext();
+			InitializeClientCredentials();
 			_clientContext = new SecHandle();
 			var clientTokenBuf = new SecBufferDesc(MAX_TOKEN_SIZE);
 			try
@@ -423,6 +418,16 @@ private void Dispose(bool disposing)
 			}
 		}
 
+		private void InitializeClientCredentials()
+		{
+			_clientCredentials = new SecHandle();
+			var resCode = AcquireCredentialsHandle(null, _securityPackage, SECPKG_CRED_OUTBOUND,
+				IntPtr.Zero, IntPtr.Zero, 0, IntPtr.Zero,
+				out _clientCredentials, out var expiry);
+			if (resCode != SEC_E_OK)
+				throw new Exception($"{nameof(AcquireCredentialsHandle)} failed");
+		}
+
 		private void CloseClientContext()
 		{
 			if (!_clientContext.IsInvalid)