fix: pkcs12 signing

TODO: add PEM support and use page number

src/main/java/org/apache/pdfbox/examples/util/ConnectedInputStream.java

@@ -0,0 +1,82 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.pdfbox.examples.util;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.HttpURLConnection;
+
+/**
+ * Delegate class to close the connection when the class gets closed.
+ *
+ * @author Tilman Hausherr
+ */
+public class ConnectedInputStream extends InputStream {
+    HttpURLConnection con;
+    InputStream is;
+
+    public ConnectedInputStream(HttpURLConnection con, InputStream is) {
+        this.con = con;
+        this.is = is;
+    }
+
+    @Override
+    public int read() throws IOException {
+        return is.read();
+    }
+
+    @Override
+    public int read(byte[] b) throws IOException {
+        return is.read(b);
+    }
+
+    @Override
+    public int read(byte[] b, int off, int len) throws IOException {
+        return is.read(b, off, len);
+    }
+
+    @Override
+    public long skip(long n) throws IOException {
+        return is.skip(n);
+    }
+
+    @Override
+    public int available() throws IOException {
+        return is.available();
+    }
+
+    @Override
+    public synchronized void mark(int readlimit) {
+        is.mark(readlimit);
+    }
+
+    @Override
+    public synchronized void reset() throws IOException {
+        is.reset();
+    }
+
+    @Override
+    public boolean markSupported() {
+        return is.markSupported();
+    }
+
+    @Override
+    public void close() throws IOException {
+        is.close();
+        con.disconnect();
+    }
+}