OF-1335: Don't strip namespaces everywhere.

Openfire prevents the need to re-scope XML (as described in RFC 6120 section 4.8.3) by
pre-emptively remove certain namespaces (such as 'jabber:client' and 'jabber:server').
It should not, however, remove these namespaces everywhere. This commit prevents such
removal in places other than the first and second level elements (typically: stream
and stanza elements).

src/java/org/dom4j/io/XMPPPacketReader.java

@@ -16,6 +16,8 @@ import org.xmlpull.v1.XmlPullParserFactory;
 
 import java.io.*;
 import java.net.URL;
+import java.util.Arrays;
+import java.util.Collection;
 
 /**
  * <p><code>XMPPPacketReader</code> is a Reader of DOM4J documents that
@@ -54,6 +56,15 @@ public class XMPPPacketReader {
      */
     private long lastActive = System.currentTimeMillis();
 
+    /**
+     * Stream of various endpoints (eg: s2s, c2s) use different default namespaces. To be able to use a stanza that's
+     * parsed on one type of endpoint in the context of another endpoint, we explicitly ignore these namespaced. This
+     * allows us to forward, for instance, a stanza received via C2S (which has the "jabber:client" default namespace)
+     * on a S2S stream (which has the "jabber:server" default namespace).
+     *
+     * @see <a href="https://xmpp.org/rfcs/rfc6120.html#streams-ns-xmpp">RFC 6120, 4.8.3. XMPP Content Namespaces</a>
+     */
+    public static final Collection<String> IGNORED_NAMESPACE_ON_STANZA = Arrays.asList( "jabber:client", "jabber:server", "jabber:connectionmanager", "jabber:component:accept", "http://jabber.org/protocol/httpbind" );
 
     public XMPPPacketReader() {
     }
@@ -364,15 +375,13 @@ public class XMPPPacketReader {
                 }
                 case XmlPullParser.START_TAG: {
                     QName qname = (pp.getPrefix() == null) ? df.createQName(pp.getName(), pp.getNamespace()) : df.createQName(pp.getName(), pp.getPrefix(), pp.getNamespace());
-                    Element newElement = null;
-                    // Do not include the namespace if this is the start tag of a new packet
-                    // This avoids including "jabber:client", "jabber:server" or
-                    // "jabber:component:accept"
-                    if ("jabber:client".equals(qname.getNamespaceURI()) ||
-                            "jabber:server".equals(qname.getNamespaceURI()) ||
-                            "jabber:connectionmanager".equals(qname.getNamespaceURI()) ||
-                            "jabber:component:accept".equals(qname.getNamespaceURI()) ||
-                            "http://jabber.org/protocol/httpbind".equals(qname.getNamespaceURI())) {
+                    Element newElement;
+
+                    // Do not qualify stanza element with certain namespaces. This makes those stanzas re-usable between,
+                    // for example, c2s and s2s. This code prevents such qualification only for elements that have no
+                    // default namespace declared
+                    final boolean defaultNamespaceDeclared = parent == null || !parent.getNamespaceForPrefix("").getURI().equals("");
+                    if ( !defaultNamespaceDeclared && IGNORED_NAMESPACE_ON_STANZA.contains( qname.getNamespaceURI() ) ) {
                         newElement = df.createElement(pp.getName());
                     }
                     else {
@@ -381,9 +390,13 @@ public class XMPPPacketReader {
                     int nsStart = pp.getNamespaceCount(pp.getDepth() - 1);
                     int nsEnd = pp.getNamespaceCount(pp.getDepth());
                     for (int i = nsStart; i < nsEnd; i++) {
-                        if (pp.getNamespacePrefix(i) != null) {
-                            newElement
-                                    .addNamespace(pp.getNamespacePrefix(i), pp.getNamespaceUri(i));
+                        final String namespacePrefix = pp.getNamespacePrefix( i );
+                        final String namespaceUri = pp.getNamespaceUri( i );
+                        if ( namespacePrefix != null ) {
+                            newElement.addNamespace( namespacePrefix, namespaceUri );
+                        } else if ( !( pp.getDepth() <= 2 && IGNORED_NAMESPACE_ON_STANZA.contains(namespaceUri) ) ) {
+                            // Do not include certain default namespace on the root-element ('stream') or stanza level. This makes stanzas re-usable between, for example, c2s and s2s.
+                            newElement.addNamespace( "", namespaceUri );
                         }
                     }
                     for (int i = 0; i < pp.getAttributeCount(); i++) {

src/test/java/dom/io/XMPPPacketReaderTest.java

+/*
+ * Copyright (C) 2017 Ignite Realtime Foundation. All rights reserved.
+ *
+ * Licensed 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 dom.io;
+
+import org.dom4j.Document;
+import org.dom4j.io.XMPPPacketReader;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.StringReader;
+
+/**
+ * Unit tests that verify the functionality of {@link XMPPPacketReader}
+ *
+ * @author Guus der Kinderen, guus.der.kinderen@gmail.com
+ */
+public class XMPPPacketReaderTest
+{
+    private XMPPPacketReader packetReader;
+
+    @Before
+    public void setup()
+    {
+        packetReader = new XMPPPacketReader();
+    }
+
+    /**
+     * Check if the 'jabber:client' default namespace declaration is stripped from a stream tag.
+     *
+     * Openfire strips this namespace (among others) to make the resulting XML 're-usable', in context of the
+     * implementation note in RFC 6120, section 4.8.3.
+     *
+     * @see <a href="https://xmpp.org/rfcs/rfc6120.html#streams-ns-xmpp">RFC 6120, 4.8.3. XMPP Content Namespaces</a>
+     */
+    @Test
+    public void testStripContentNamespace() throws Exception
+    {
+        // Setup fixture.
+        final String input = "<stream:stream to='example.com' xmlns='jabber:client' xmlns:stream='http://etherx.jabber.org/streams' version='1.0'><message from='juliet@example.com' to='romeo@example.net' xml:lang='en'><body>Art thou not Romeo, and a Montague?</body></message></stream:stream>";
+
+        // Execute system under test.
+        final Document result = packetReader.read( new StringReader( input ) );
+
+        // Verify result.
+        Assert.assertFalse( result.asXML().contains( "jabber:client" ) );
+    }
+
+    /**
+     * Check if the 'jabber:client' default namespace declaration is stripped from a stanza.
+     *
+     * Openfire strips this namespace (among others) to make the resulting XML 're-usable', in context of the
+     * implementation note in RFC 6120, section 4.8.3.
+     *
+     * @see <a href="https://xmpp.org/rfcs/rfc6120.html#streams-ns-xmpp">RFC 6120, 4.8.3. XMPP Content Namespaces</a>
+     */
+    @Test
+    public void testStripPrefixFreeCanonicalization() throws Exception
+    {
+        // Setup fixture.
+        final String input = "<stream:stream to='example.com' xmlns:stream='http://etherx.jabber.org/streams' version='1.0'><message xmlns='jabber:client' from='juliet@example.com' to='romeo@example.net' xml:lang='en'><body>Art thou not Romeo, and a Montague?</body></message></stream:stream>";
+
+        // Execute system under test.
+        final Document result = packetReader.read( new StringReader( input ) );
+
+        // Verify result.
+        Assert.assertFalse( result.asXML().contains( "jabber:client" ) );
+    }
+
+    /**
+     * Check that the 'jabber:client' default namespace declaration is explicitly _not_ stripped from a child element
+     * of a stanza.
+     *
+     * Openfire strips this namespace (among others) to make the resulting XML 're-usable', in context of the
+     * implementation note in RFC 6120, section 4.8.3.
+     *
+     * @see <a href="https://issues.igniterealtime.org/browse/OF-1335">Issue OF-1335: Forwarded messages rewritten to default namespace over S2S</a>
+     * @see <a href="https://xmpp.org/rfcs/rfc6120.html#streams-ns-xmpp">RFC 6120, 4.8.3. XMPP Content Namespaces</a>
+     */
+    @Test
+    public void testAvoidStrippingInternalContentNamespace() throws Exception
+    {
+        // Setup fixture
+        final String input =
+            "<stream:stream xmlns:stream='http://etherx.jabber.org/streams' to='example.com' version='1.0'>" +
+            "  <message xmlns='jabber:client'>" +
+            "    <other xmlns='something:else'>" +
+            "      <message xmlns='jabber:client'/>" +
+            "    </other>" +
+            "  </message>" +
+            "</stream:stream>";
+
+        final Document result = packetReader.read( new StringReader( input ) );
+
+        // Verify result.
+        Assert.assertFalse( "'jabber:client' should not occur before 'something:else'", result.asXML().substring( 0, result.asXML().indexOf("something:else") ).contains( "jabber:client" ) );
+        Assert.assertTrue( "'jabber:client' should occur after 'something:else'", result.asXML().substring( result.asXML().indexOf("something:else") ).contains( "jabber:client" ) );
+    }
+
+    /**
+     * Check that the 'jabber:client' default namespace declaration is explicitly _not_ stripped from a child element
+     * of a stanza.
+     *
+     * Openfire strips this namespace (among others) to make the resulting XML 're-usable', in context of the
+     * implementation note in RFC 6120, section 4.8.3.
+     *
+     * @see <a href="https://issues.igniterealtime.org/browse/OF-1335">Issue OF-1335: Forwarded messages rewritten to default namespace over S2S</a>
+     * @see <a href="https://xmpp.org/rfcs/rfc6120.html#streams-ns-xmpp">RFC 6120, 4.8.3. XMPP Content Namespaces</a>
+     */
+    @Test
+    public void testAvoidStrippingPrefixFreeCanonicalization() throws Exception
+    {
+        // Setup fixture
+        final String input =
+            "<stream:stream xmlns='jabber:client' xmlns:stream='http://etherx.jabber.org/streams' to='example.com' version='1.0'>" +
+                "  <message>" +
+                "    <other xmlns='something:else'>" +
+                "      <message xmlns='jabber:client'/>" +
+                "    </other>" +
+                "  </message>" +
+                "</stream:stream>";
+
+        final Document result = packetReader.read( new StringReader( input ) );
+
+        // Verify result.
+        Assert.assertFalse( "'jabber:client' should not occur before 'something:else'", result.asXML().substring( 0, result.asXML().indexOf("something:else") ).contains( "jabber:client" ) );
+        Assert.assertTrue( "'jabber:client' should occur after 'something:else'", result.asXML().substring( result.asXML().indexOf("something:else") ).contains( "jabber:client" ) );
+    }
+}