Add support for XEP-0420: Stanza Content Encryption

documentation/extensions/index.md

@@ -123,6 +123,7 @@ Experimental Smack Extensions and currently supported XEPs of smack-experimental
 | [Consistent Color Generation](consistent_colors.md)       | [XEP-0392](https://xmpp.org/extensions/xep-0392.html)  | 0.6.0     | Generate consistent colors for identifiers like usernames to provide a consistent user experience. |
 | [Message Markup](messagemarkup.md)                        | [XEP-0394](https://xmpp.org/extensions/xep-0394.html)  | 0.1.0     | Style message bodies while keeping body and markup information separated. |
 | DNS Queries over XMPP (DoX)                               | [XEP-0418](https://xmpp.org/extensions/xep-0418.html)  | 0.1.0     | Send DNS queries and responses over XMPP. |
+| Stanza Content Encryption                                 | [XEP-0420](https://xmpp.org/extensions/xep-0420.html)  | 0.3.0     | End-to-end encryption of arbitrary extension elements. Smack provides elements and providers to be used by encryption mechanisms. |
 | Message Fastening                                         | [XEP-0422](https://xmpp.org/extensions/xep-0422.html)  | 0.1.1     | Mark payloads on a message to be logistically fastened to a previous message. |
 | Message Retraction                                        | [XEP-0424](https://xmpp.org/extensions/xep-0424.html)  | 0.2.0     | Mark messages as retracted. |
 | Fallback Indication                                       | [XEP-0428](https://xmpp.org/extensions/xep-0428.html)  | 0.1.0     | Declare body elements of a message as ignorable fallback for naive legacy clients. |

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/element/AffixElement.java

@@ -0,0 +1,29 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.element;
+
+import org.jivesoftware.smack.packet.Element;
+
+/**
+ * Interface that marks elements that may be used as affix elements inside a {@link ContentElement}.
+ *
+ * @see <a href="https://xmpp.org/extensions/xep-0420.html#affix_elements">
+ *     XEP-0420: Stanza Content Encryption - §4. Affix Elements</a>
+ */
+public interface AffixElement extends Element {
+
+}

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/element/AffixExtensionElement.java

@@ -0,0 +1,32 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.element;
+
+import org.jivesoftware.smack.packet.ExtensionElement;
+
+/**
+ * Affix element that is identified by element name and namespace.
+ * You should extend this interface with your custom affix extension elements
+ * and also provide a {@link org.jivesoftware.smackx.stanza_content_encryption.provider.AffixExtensionElementProvider}
+ * for them.
+ *
+ * @see <a href="https://xmpp.org/extensions/xep-0420.html#affix_elements">
+ *     XEP-0420: Stanza Content Encryption - §4. Affix Elements</a>
+ */
+public interface AffixExtensionElement extends ExtensionElement, AffixElement {
+
+}

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/element/ContentElement.java

@@ -0,0 +1,288 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.element;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Date;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import javax.xml.namespace.QName;
+
+import org.jivesoftware.smack.packet.ExtensionElement;
+import org.jivesoftware.smack.packet.XmlEnvironment;
+import org.jivesoftware.smack.util.Objects;
+import org.jivesoftware.smack.util.XmlStringBuilder;
+import org.jivesoftware.smackx.address.packet.MultipleAddresses;
+import org.jivesoftware.smackx.hints.element.MessageProcessingHint;
+import org.jivesoftware.smackx.sid.element.StanzaIdElement;
+
+import org.jxmpp.jid.Jid;
+
+/**
+ * Extension element that holds the payload element, as well as a list of affix elements.
+ * In SCE, the XML representation of this element is what will be encrypted using the encryption mechanism of choice.
+ */
+public class ContentElement implements ExtensionElement {
+
+    private static final String NAMESPACE_UNVERSIONED = "urn:xmpp:sce";
+    public static final String NAMESPACE_0 = NAMESPACE_UNVERSIONED + ":0";
+    public static final String NAMESPACE = NAMESPACE_0;
+    public static final String ELEMENT = "content";
+    public static final QName QNAME = new QName(NAMESPACE, ELEMENT);
+
+    private final PayloadElement payload;
+    private final List<AffixElement> affixElements;
+
+    ContentElement(PayloadElement payload, List<AffixElement> affixElements) {
+        this.payload = payload;
+        this.affixElements = Collections.unmodifiableList(affixElements);
+    }
+
+    /**
+     * Return the {@link PayloadElement} which holds the sensitive payload extensions.
+     *
+     * @return payload element
+     */
+    public PayloadElement getPayload() {
+        return payload;
+    }
+
+    /**
+     * Return a list of affix elements.
+     * Those are elements that need to be verified upon reception by the encryption mechanisms implementation.
+     *
+     * @see <a href="https://xmpp.org/extensions/xep-0420.html#affix_elements">
+     *     XEP-0420: Stanza Content Encryption - §4. Affix Elements</a>
+     *
+     * @return list of affix elements
+     */
+    public List<AffixElement> getAffixElements() {
+        return affixElements;
+    }
+
+    @Override
+    public String getNamespace() {
+        return NAMESPACE;
+    }
+
+    @Override
+    public String getElementName() {
+        return ELEMENT;
+    }
+
+    @Override
+    public XmlStringBuilder toXML(XmlEnvironment xmlEnvironment) {
+        XmlStringBuilder xml = new XmlStringBuilder(this).rightAngleBracket();
+        xml.append(affixElements);
+        xml.append(payload);
+        return xml.closeElement(this);
+    }
+
+    @Override
+    public QName getQName() {
+        return QNAME;
+    }
+
+    /**
+     * Return a {@link Builder} that can be used to build the {@link ContentElement}.
+     * @return builder
+     */
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    public static final class Builder {
+        private static final Set<String> BLACKLISTED_NAMESPACES = Collections.singleton(MessageProcessingHint.NAMESPACE);
+        private static final Set<QName> BLACKLISTED_QNAMES = Collections.unmodifiableSet(new HashSet<>(Arrays.asList(
+                StanzaIdElement.QNAME,
+                MultipleAddresses.QNAME
+        )));
+
+        private FromAffixElement from = null;
+        private TimestampAffixElement timestamp = null;
+        private RandomPaddingAffixElement rpad = null;
+
+        private final List<AffixElement> otherAffixElements = new ArrayList<>();
+        private final List<ExtensionElement> payloadItems = new ArrayList<>();
+
+        private Builder() {
+
+        }
+
+        /**
+         * Add an affix element of type 'to' which addresses one recipient.
+         * The jid in the 'to' element SHOULD be a bare jid.
+         *
+         * @param jid jid
+         * @return builder
+         */
+        public Builder addTo(Jid jid) {
+            return addTo(new ToAffixElement(jid));
+        }
+
+        /**
+         * Add an affix element of type 'to' which addresses one recipient.
+         *
+         * @param to affix element
+         * @return builder
+         */
+        public Builder addTo(ToAffixElement to) {
+            this.otherAffixElements.add(Objects.requireNonNull(to, "'to' affix element MUST NOT be null."));
+            return this;
+        }
+
+        /**
+         * Set the senders jid as a 'from' affix element.
+         *
+         * @param jid jid of the sender
+         * @return builder
+         */
+        public Builder setFrom(Jid jid) {
+            return setFrom(new FromAffixElement(jid));
+        }
+
+        /**
+         * Set the senders jid as a 'from' affix element.
+         *
+         * @param from affix element
+         * @return builder
+         */
+        public Builder setFrom(FromAffixElement from) {
+            this.from = Objects.requireNonNull(from, "'form' affix element MUST NOT be null.");
+            return this;
+        }
+
+        /**
+         * Set the given date as a 'time' affix element.
+         *
+         * @param date timestamp as date
+         * @return builder
+         */
+        public Builder setTimestamp(Date date) {
+            return setTimestamp(new TimestampAffixElement(date));
+        }
+
+        /**
+         * Set the timestamp of the message as a 'time' affix element.
+         *
+         * @param timestamp timestamp affix element
+         * @return builder
+         */
+        public Builder setTimestamp(TimestampAffixElement timestamp) {
+            this.timestamp = Objects.requireNonNull(timestamp, "'time' affix element MUST NOT be null.");
+            return this;
+        }
+
+        /**
+         * Set some random length random content padding.
+         *
+         * @return builder
+         */
+        public Builder setRandomPadding() {
+            this.rpad = new RandomPaddingAffixElement();
+            return this;
+        }
+
+        /**
+         * Set the given string as padding.
+         * The padding should be of length between 1 and 200 characters.
+         *
+         * @param padding padding string
+         * @return builder
+         */
+        public Builder setRandomPadding(String padding) {
+            return setRandomPadding(new RandomPaddingAffixElement(padding));
+        }
+
+        /**
+         * Set a padding affix element.
+         *
+         * @param padding affix element
+         * @return builder
+         */
+        public Builder setRandomPadding(RandomPaddingAffixElement padding) {
+            this.rpad = Objects.requireNonNull(padding, "'rpad' affix element MUST NOT be empty.");
+            return this;
+        }
+
+        /**
+         * Add an additional, SCE profile specific affix element.
+         *
+         * @param customAffixElement additional affix element
+         * @return builder
+         */
+        public Builder addFurtherAffixElement(AffixElement customAffixElement) {
+            this.otherAffixElements.add(Objects.requireNonNull(customAffixElement,
+                    "Custom affix element MUST NOT be null."));
+            return this;
+        }
+
+        /**
+         * Add a payload item as child element of the payload element.
+         * There are some items that are not allowed as payload.
+         * Adding those will throw an exception.
+         *
+         * @see <a href="https://xmpp.org/extensions/xep-0420.html#server-processed">
+         *     XEP-0420: Stanza Content Encryption - §9. Server-processed Elements</a>
+         *
+         * @param payloadItem extension element
+         * @return builder
+         * @throws IllegalArgumentException in case an extension element from the blacklist is added.
+         */
+        public Builder addPayloadItem(ExtensionElement payloadItem) {
+            Objects.requireNonNull(payloadItem, "Payload item MUST NOT be null.");
+            this.payloadItems.add(checkForIllegalPayloadsAndPossiblyThrow(payloadItem));
+            return this;
+        }
+
+        /**
+         * Construct a content element from this builder.
+         *
+         * @return content element
+         */
+        public ContentElement build() {
+            List<AffixElement> allAffixElements = collectAffixElements();
+            PayloadElement payloadElement = new PayloadElement(payloadItems);
+            return new ContentElement(payloadElement, allAffixElements);
+        }
+
+        private static ExtensionElement checkForIllegalPayloadsAndPossiblyThrow(ExtensionElement payloadItem) {
+            QName qName = payloadItem.getQName();
+            if (BLACKLISTED_QNAMES.contains(qName)) {
+                throw new IllegalArgumentException("Element identified by " + qName +
+                        " is not allowed as payload item. See https://xmpp.org/extensions/xep-0420.html#server-processed");
+            }
+
+            String namespace = payloadItem.getNamespace();
+            if (BLACKLISTED_NAMESPACES.contains(namespace)) {
+                throw new IllegalArgumentException("Elements of namespace '" + namespace +
+                        "' are not allowed as payload items. See https://xmpp.org/extensions/xep-0420.html#server-processed");
+            }
+
+            return payloadItem;
+        }
+
+        private List<AffixElement> collectAffixElements() {
+            List<AffixElement> allAffixElements = new ArrayList<>(Arrays.asList(rpad, from, timestamp));
+            allAffixElements.addAll(otherAffixElements);
+            return allAffixElements;
+        }
+    }
+}

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/element/FromAffixElement.java

@@ -0,0 +1,33 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.element;
+
+import org.jxmpp.jid.Jid;
+
+public class FromAffixElement extends JidAffixElement {
+
+    public static final String ELEMENT = "from";
+
+    public FromAffixElement(Jid jid) {
+        super(jid);
+    }
+
+    @Override
+    public String getElementName() {
+        return ELEMENT;
+    }
+}

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/element/JidAffixElement.java

@@ -0,0 +1,57 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.element;
+
+import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.XmlEnvironment;
+import org.jivesoftware.smack.util.EqualsUtil;
+import org.jivesoftware.smack.util.Objects;
+import org.jivesoftware.smack.util.XmlStringBuilder;
+
+import org.jxmpp.jid.Jid;
+
+public abstract class JidAffixElement implements NamedElement, AffixElement {
+
+    public static final String ATTR_JID = "jid";
+
+    private final Jid jid;
+
+    public JidAffixElement(Jid jid) {
+        this.jid = Objects.requireNonNull(jid, "Value of 'jid' MUST NOT be null.");
+    }
+
+    public Jid getJid() {
+        return jid;
+    }
+
+    @Override
+    public XmlStringBuilder toXML(XmlEnvironment xmlEnvironment) {
+        return new XmlStringBuilder(this)
+                .attribute(ATTR_JID, getJid())
+                .closeEmptyElement();
+    }
+
+    @Override
+    public final boolean equals(Object obj) {
+        return EqualsUtil.equals(this, obj, (e, o) -> e.append(getJid(), o.getJid()).append(getElementName(), o.getElementName()));
+    }
+
+    @Override
+    public final int hashCode() {
+        return (getElementName() + getJid().toString()).hashCode();
+    }
+}

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/element/PayloadElement.java

@@ -0,0 +1,52 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.element;
+
+import java.util.Collections;
+import java.util.List;
+
+import org.jivesoftware.smack.packet.ExtensionElement;
+import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.XmlEnvironment;
+import org.jivesoftware.smack.util.XmlStringBuilder;
+
+public class PayloadElement implements NamedElement {
+
+    public static final String ELEMENT = "payload";
+
+    private final List<ExtensionElement> payloadElements;
+
+    public PayloadElement(List<ExtensionElement> payloadElements) {
+        this.payloadElements = Collections.unmodifiableList(payloadElements);
+    }
+
+    public List<ExtensionElement> getItems() {
+        return payloadElements;
+    }
+
+    @Override
+    public String getElementName() {
+        return ELEMENT;
+    }
+
+    @Override
+    public XmlStringBuilder toXML(XmlEnvironment xmlEnvironment) {
+        XmlStringBuilder xml = new XmlStringBuilder(this).rightAngleBracket();
+        xml.append(payloadElements);
+        return xml.closeElement(this);
+    }
+}

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/element/RandomPaddingAffixElement.java

@@ -0,0 +1,75 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.element;
+
+import java.security.SecureRandom;
+
+import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.XmlEnvironment;
+import org.jivesoftware.smack.util.EqualsUtil;
+import org.jivesoftware.smack.util.RandomUtil;
+import org.jivesoftware.smack.util.StringUtils;
+import org.jivesoftware.smack.util.XmlStringBuilder;
+
+public class RandomPaddingAffixElement implements NamedElement, AffixElement {
+
+    private static final int minPaddingLength = 1;
+    private static final int maxPaddingLength = 200;
+    public static final String ELEMENT = "rpad";
+
+    private final String padding;
+
+    public RandomPaddingAffixElement(String padding) {
+        this.padding = StringUtils.escapeForXmlText(
+                StringUtils.requireNotNullNorEmpty(padding, "Value of 'rpad' MUST NOT be null nor empty."))
+                .toString();
+    }
+
+    public RandomPaddingAffixElement() {
+        this(StringUtils.randomString(randomPaddingLength(), new SecureRandom()));
+    }
+
+    private static int randomPaddingLength() {
+        return minPaddingLength + RandomUtil.nextSecureRandomInt(maxPaddingLength - minPaddingLength);
+    }
+
+    public String getPadding() {
+        return padding;
+    }
+
+    @Override
+    public String getElementName() {
+        return ELEMENT;
+    }
+
+    @Override
+    public XmlStringBuilder toXML(XmlEnvironment xmlEnvironment) {
+        return new XmlStringBuilder(this).rightAngleBracket()
+                .append(getPadding())
+                .closeElement(this);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        return EqualsUtil.equals(this, obj, (e, o) -> e.append(getPadding(), o.getPadding()));
+    }
+
+    @Override
+    public int hashCode() {
+        return getPadding().hashCode();
+    }
+}

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/element/TimestampAffixElement.java

@@ -0,0 +1,63 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.element;
+
+import java.util.Date;
+
+import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.XmlEnvironment;
+import org.jivesoftware.smack.util.EqualsUtil;
+import org.jivesoftware.smack.util.Objects;
+import org.jivesoftware.smack.util.XmlStringBuilder;
+
+public class TimestampAffixElement implements NamedElement, AffixElement {
+
+    public static final String ELEMENT = "time";
+    public static final String ATTR_STAMP = "stamp";
+
+    private final Date timestamp;
+
+    public TimestampAffixElement(Date timestamp) {
+        this.timestamp = Objects.requireNonNull(timestamp, "Date must not be null.");
+    }
+
+    public Date getTimestamp() {
+        return timestamp;
+    }
+
+    @Override
+    public String getElementName() {
+        return ELEMENT;
+    }
+
+    @Override
+    public CharSequence toXML(XmlEnvironment xmlEnvironment) {
+        return new XmlStringBuilder(this)
+                .attribute(ATTR_STAMP, getTimestamp())
+                .closeEmptyElement();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        return EqualsUtil.equals(this, obj, (e, o) -> e.append(getTimestamp(), o.getTimestamp()));
+    }
+
+    @Override
+    public int hashCode() {
+        return timestamp.hashCode();
+    }
+}

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/element/ToAffixElement.java

@@ -0,0 +1,34 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.element;
+
+import org.jxmpp.jid.Jid;
+
+public class ToAffixElement extends JidAffixElement {
+
+    public static final String ELEMENT = "to";
+
+    public ToAffixElement(Jid jid) {
+        super(jid);
+    }
+
+    @Override
+    public String getElementName() {
+        return ELEMENT;
+    }
+
+}

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/element/package-info.java

@@ -0,0 +1,20 @@
+/**
+ *
+ * Copyright 2018 Paul Schaub
+ *
+ * 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.
+ */
+/**
+ * Smack's API for XEP-0420: Stanza Content Encryption: Element classes.
+  */
+package org.jivesoftware.smackx.stanza_content_encryption.element;

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/package-info.java

@@ -0,0 +1,22 @@
+/**
+ *
+ * Copyright 2018 Paul Schaub
+ *
+ * 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.
+ */
+/**
+ * Smack's API for XEP-0420: Stanza Content Encryption.
+ *
+ * @see <a href="https://xmpp.org/extensions/xep-0420.html">XEP-0420: Stanza Content Encryption</a>
+  */
+package org.jivesoftware.smackx.stanza_content_encryption;

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/provider/AffixExtensionElementProvider.java

@@ -0,0 +1,29 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.provider;
+
+import org.jivesoftware.smack.provider.ExtensionElementProvider;
+import org.jivesoftware.smackx.stanza_content_encryption.element.AffixExtensionElement;
+
+/**
+ * Abstract class that needs to be extended by provider classes that parse out affix extension elements.
+ *
+ * @param <AE> affix extension element.
+ */
+public abstract class AffixExtensionElementProvider<AE extends AffixExtensionElement> extends ExtensionElementProvider<AE> {
+
+}

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/provider/ContentElementProvider.java

@@ -0,0 +1,137 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.provider;
+
+import java.io.IOException;
+import java.util.Date;
+
+import org.jivesoftware.smack.packet.ExtensionElement;
+import org.jivesoftware.smack.packet.XmlEnvironment;
+import org.jivesoftware.smack.parsing.SmackParsingException;
+import org.jivesoftware.smack.provider.ExtensionElementProvider;
+import org.jivesoftware.smack.util.PacketParserUtils;
+import org.jivesoftware.smack.util.ParserUtils;
+import org.jivesoftware.smack.xml.XmlPullParser;
+import org.jivesoftware.smack.xml.XmlPullParserException;
+import org.jivesoftware.smackx.stanza_content_encryption.element.AffixElement;
+import org.jivesoftware.smackx.stanza_content_encryption.element.ContentElement;
+import org.jivesoftware.smackx.stanza_content_encryption.element.FromAffixElement;
+import org.jivesoftware.smackx.stanza_content_encryption.element.PayloadElement;
+import org.jivesoftware.smackx.stanza_content_encryption.element.RandomPaddingAffixElement;
+import org.jivesoftware.smackx.stanza_content_encryption.element.TimestampAffixElement;
+import org.jivesoftware.smackx.stanza_content_encryption.element.ToAffixElement;
+
+import org.jxmpp.jid.impl.JidCreate;
+import org.jxmpp.stringprep.XmppStringprepException;
+
+public class ContentElementProvider extends ExtensionElementProvider<ContentElement> {
+
+    @Override
+    public ContentElement parse(XmlPullParser parser, int initialDepth, XmlEnvironment xmlEnvironment)
+            throws XmlPullParserException, IOException, SmackParsingException {
+        ContentElement.Builder builder = ContentElement.builder();
+
+        while (true) {
+            XmlPullParser.Event tag = parser.next();
+            if (tag == XmlPullParser.Event.START_ELEMENT) {
+                String name = parser.getName();
+                switch (name) {
+                    case ToAffixElement.ELEMENT:
+                        parseToAffix(parser, builder);
+                        break;
+
+                    case FromAffixElement.ELEMENT:
+                        parseFromAffix(parser, builder);
+                        break;
+
+                    case TimestampAffixElement.ELEMENT:
+                        parseTimestampAffix(parser, builder);
+                        break;
+
+                    case RandomPaddingAffixElement.ELEMENT:
+                        parseRPadAffix(parser, builder);
+                        break;
+
+                    case PayloadElement.ELEMENT:
+                        parsePayload(parser, xmlEnvironment, builder);
+                        break;
+
+                    default:
+                        parseCustomAffix(parser, xmlEnvironment, builder);
+                        break;
+                }
+            } else if (tag == XmlPullParser.Event.END_ELEMENT) {
+                if (parser.getDepth() == initialDepth) {
+                    break;
+                }
+            }
+        }
+        return builder.build();
+    }
+
+    private static void parseCustomAffix(XmlPullParser parser, XmlEnvironment outerXmlEnvironment, ContentElement.Builder builder)
+            throws XmlPullParserException, IOException, SmackParsingException {
+        String name = parser.getName();
+        String namespace = parser.getNamespace();
+
+        AffixElement element = (AffixElement) PacketParserUtils.parseExtensionElement(name, namespace, parser, outerXmlEnvironment);
+        builder.addFurtherAffixElement(element);
+    }
+
+    private static void parsePayload(XmlPullParser parser, XmlEnvironment outerXmlEnvironment, ContentElement.Builder builder)
+            throws IOException, XmlPullParserException, SmackParsingException {
+        final int initialDepth = parser.getDepth();
+        while (true) {
+            XmlPullParser.Event tag = parser.next();
+
+            if (tag == XmlPullParser.Event.START_ELEMENT) {
+                String name = parser.getName();
+                String namespace = parser.getNamespace();
+                ExtensionElement element = PacketParserUtils.parseExtensionElement(name, namespace, parser, outerXmlEnvironment);
+                builder.addPayloadItem(element);
+            }
+
+            if (tag == XmlPullParser.Event.END_ELEMENT && parser.getDepth() == initialDepth) {
+                return;
+            }
+        }
+    }
+
+    private static void parseRPadAffix(XmlPullParser parser, ContentElement.Builder builder)
+            throws IOException, XmlPullParserException {
+        builder.setRandomPadding(parser.nextText());
+    }
+
+    private static void parseTimestampAffix(XmlPullParser parser, ContentElement.Builder builder)
+            throws SmackParsingException.SmackTextParseException {
+        Date timestamp = ParserUtils.getDateFromXep82String(
+                parser.getAttributeValue("", TimestampAffixElement.ATTR_STAMP));
+        builder.setTimestamp(timestamp);
+    }
+
+    private static void parseFromAffix(XmlPullParser parser, ContentElement.Builder builder)
+            throws XmppStringprepException {
+        String jidString = parser.getAttributeValue("", FromAffixElement.ATTR_JID);
+        builder.setFrom(JidCreate.from(jidString));
+    }
+
+    private static void parseToAffix(XmlPullParser parser, ContentElement.Builder builder)
+            throws XmppStringprepException {
+        String jidString = parser.getAttributeValue("", ToAffixElement.ATTR_JID);
+        builder.addTo(JidCreate.from(jidString));
+    }
+}

smack-experimental/src/main/java/org/jivesoftware/smackx/stanza_content_encryption/provider/package-info.java

@@ -0,0 +1,20 @@
+/**
+ *
+ * Copyright 2018 Paul Schaub
+ *
+ * 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.
+ */
+/**
+ * Smack's API for XEP-0420: Stanza Content Encryption: Provider classes.
+  */
+package org.jivesoftware.smackx.stanza_content_encryption.provider;

smack-experimental/src/main/resources/org.jivesoftware.smack.experimental/experimental.providers

@@ -292,6 +292,13 @@
       <className>org.jivesoftware.smackx.dox.provider.DnsIqProvider</className>
     </iqProvider>
 
+    <!-- XEP-0420: Stanza Content Encryption (SCE) -->
+    <extensionProvider>
+      <elementName>content</elementName>
+      <namespace>urn:xmpp:sce:0</namespace>
+      <className>org.jivesoftware.smackx.stanza_content_encryption.provider.ContentElementProvider</className>
+    </extensionProvider>
+
     <!-- XEP-0422: Message Fastening -->
     <extensionProvider>
       <elementName>apply-to</elementName>

smack-experimental/src/test/java/org/jivesoftware/smackx/stanza_content_encryption/element/AffixElementsTest.java

@@ -0,0 +1,156 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.element;
+
+import static org.jivesoftware.smack.test.util.XmlAssertUtil.assertXmlSimilar;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.text.ParseException;
+import java.util.Date;
+
+import org.junit.jupiter.api.Test;
+import org.jxmpp.jid.EntityBareJid;
+import org.jxmpp.jid.impl.JidCreate;
+import org.jxmpp.util.XmppDateTime;
+
+public class AffixElementsTest {
+
+    public static final EntityBareJid JID_HOUSTON = JidCreate.entityBareFromOrThrowUnchecked("missioncontrol@houston.nasa.gov");
+    public static final EntityBareJid JID_OPPORTUNITY = JidCreate.entityBareFromOrThrowUnchecked("opportunity@mars.planet");
+
+    /**
+     * Test serialization of 'to' affix element.
+     *
+     * @see <a href="https://xmpp.org/extensions/xep-0420.html#example-1">XEP-420 Example 1</a>
+     */
+    @Test
+    public void testToAffixElement() {
+        ToAffixElement to = new ToAffixElement(JID_HOUSTON);
+        String expectedXml = "<to jid='missioncontrol@houston.nasa.gov'/>";
+
+        assertXmlSimilar(expectedXml, to.toXML());
+        assertEquals(JID_HOUSTON, to.getJid());
+    }
+
+    @Test
+    public void testToAffixElementEquals() {
+        ToAffixElement to1 = new ToAffixElement(JID_HOUSTON);
+        ToAffixElement to2 = new ToAffixElement(JID_HOUSTON);
+
+        assertEquals(to1, to2);
+        assertEquals(to1, to1);
+        assertEquals(to1.hashCode(), to2.hashCode());
+        assertFalse(to1.equals(null));
+    }
+
+    @Test
+    public void toElementNullArgThrows() {
+        assertThrows(IllegalArgumentException.class, () -> new ToAffixElement(null));
+    }
+
+    /**
+     * Test serialization of 'from' affix element.
+     *
+     * @see <a href="https://xmpp.org/extensions/xep-0420.html#example-1">XEP-420 Example 1</a>
+     */
+    @Test
+    public void testFromAffixElement() {
+        FromAffixElement from = new FromAffixElement(JID_OPPORTUNITY);
+        String expectedXml = "<from jid='opportunity@mars.planet'/>";
+
+        assertXmlSimilar(expectedXml, from.toXML());
+        assertEquals(JID_OPPORTUNITY, from.getJid());
+    }
+
+    @Test
+    public void testFromAffixElementEquals() {
+        FromAffixElement from1 = new FromAffixElement(JID_HOUSTON);
+        FromAffixElement from2 = new FromAffixElement(JID_HOUSTON);
+
+        assertEquals(from1, from2);
+        assertEquals(from1, from1);
+        assertEquals(from1.hashCode(), from2.hashCode());
+        assertFalse(from1.equals(null));
+    }
+
+    @Test
+    public void fromElementNullArgThrows() {
+        assertThrows(IllegalArgumentException.class, () -> new FromAffixElement(null));
+    }
+
+    @Test
+    public void testTimestampAffixElement() throws ParseException {
+        Date date = XmppDateTime.parseDate("2004-01-25T05:05:00.000+00:00");
+        TimestampAffixElement timestamp = new TimestampAffixElement(date);
+        String expectedXml = "<time stamp='2004-01-25T05:05:00.000+00:00'/>";
+
+        assertXmlSimilar(expectedXml, timestamp.toXML());
+        assertEquals(date, timestamp.getTimestamp());
+    }
+
+    @Test
+    public void timestampElementNullArgThrows() {
+        assertThrows(IllegalArgumentException.class, () -> new TimestampAffixElement(null));
+    }
+
+    @Test
+    public void testTimestampElementEquals() throws ParseException {
+        TimestampAffixElement t1 = new TimestampAffixElement(XmppDateTime.parseDate("2004-01-25T05:05:00.000+00:00"));
+        TimestampAffixElement t2 = new TimestampAffixElement(t1.getTimestamp());
+
+        assertEquals(t1, t2);
+        assertEquals(t1, t1);
+        assertEquals(t1.hashCode(), t2.hashCode());
+        assertFalse(t1.equals(null));
+    }
+
+    @Test
+    public void testRandomPaddingElement() {
+        RandomPaddingAffixElement rpad = new RandomPaddingAffixElement();
+
+        assertNotNull(rpad.getPadding());
+        assertTrue(rpad.getPadding().length() < 200);
+    }
+
+    @Test
+    public void testRandomPaddingEquals() {
+        RandomPaddingAffixElement rpad1 = new RandomPaddingAffixElement();
+        RandomPaddingAffixElement rpad2 = new RandomPaddingAffixElement(rpad1.getPadding());
+
+        assertEquals(rpad1, rpad2);
+        assertEquals(rpad1, rpad1);
+        assertEquals(rpad1.hashCode(), rpad2.hashCode());
+        assertFalse(rpad1.equals(null));
+    }
+
+    @Test
+    public void testRandomPaddingSerialization() {
+        RandomPaddingAffixElement rpad = new RandomPaddingAffixElement();
+        String expectedXml = "<rpad>" + rpad.getPadding() + "</rpad>";
+
+        assertXmlSimilar(expectedXml, rpad.toXML());
+    }
+
+    @Test
+    public void rpadElementNullArgThrows() {
+        assertThrows(IllegalArgumentException.class, () -> new RandomPaddingAffixElement(null));
+    }
+}

smack-experimental/src/test/java/org/jivesoftware/smackx/stanza_content_encryption/element/ContentElementTest.java

@@ -0,0 +1,81 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.element;
+
+import static org.jivesoftware.smack.test.util.XmlAssertUtil.assertXmlSimilar;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.text.ParseException;
+import java.util.Collections;
+
+import org.jivesoftware.smack.packet.Message;
+import org.jivesoftware.smackx.hints.element.StoreHint;
+import org.jivesoftware.smackx.sid.element.StanzaIdElement;
+
+import org.junit.jupiter.api.Test;
+import org.jxmpp.util.XmppDateTime;
+
+public class ContentElementTest {
+
+    @Test
+    public void testContentElement() throws ParseException {
+        Message.Body body = new Message.Body("en", "My battery is low and it’s getting dark"); // :'(
+
+        ContentElement contentElement = ContentElement.builder()
+                .addPayloadItem(body)
+                .setFrom(AffixElementsTest.JID_OPPORTUNITY)
+                .addTo(AffixElementsTest.JID_HOUSTON)
+                .setTimestamp(XmppDateTime.parseXEP0082Date("2018-06-10T00:00:00.000+00:00"))
+                .setRandomPadding("RANDOMPADDING")
+                .build();
+
+        String expectedXml = "" +
+                "<content xmlns='urn:xmpp:sce:0'>" +
+                "  <to jid='missioncontrol@houston.nasa.gov'/>" +
+                "  <from jid='opportunity@mars.planet'/>" +
+                "  <time stamp='2018-06-10T00:00:00.000+00:00'/>" +
+                "  <rpad>RANDOMPADDING</rpad>" +
+                "  <payload>" +
+                "    <body xmlns='jabber:client' xml:lang='en'>My battery is low and it’s getting dark</body>" +
+                "  </payload>" +
+                "</content>";
+
+        assertXmlSimilar(expectedXml, contentElement.toXML());
+        assertEquals(Collections.singletonList(body), contentElement.getPayload().getItems());
+
+        assertEquals(4, contentElement.getAffixElements().size());
+        assertTrue(contentElement.getAffixElements().contains(new ToAffixElement(AffixElementsTest.JID_HOUSTON)));
+        assertTrue(contentElement.getAffixElements().contains(new FromAffixElement(AffixElementsTest.JID_OPPORTUNITY)));
+        assertTrue(contentElement.getAffixElements().contains(
+                new TimestampAffixElement(XmppDateTime.parseXEP0082Date("2018-06-10T00:00:00.000+00:00"))));
+        assertTrue(contentElement.getAffixElements().contains(new RandomPaddingAffixElement("RANDOMPADDING")));
+    }
+
+    @Test
+    public void stanzaIdForbiddenInContentElementPayload() {
+        assertThrows(IllegalArgumentException.class,
+                () -> ContentElement.builder().addPayloadItem(new StanzaIdElement("alice@wonderland.lit")));
+    }
+
+    @Test
+    public void processingHintsForbiddenInContentElementPayload() {
+        assertThrows(IllegalArgumentException.class,
+                () -> ContentElement.builder().addPayloadItem(StoreHint.INSTANCE));
+    }
+}

smack-experimental/src/test/java/org/jivesoftware/smackx/stanza_content_encryption/provider/ContentElementProviderTest.java

@@ -0,0 +1,84 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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 org.jivesoftware.smackx.stanza_content_encryption.provider;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.IOException;
+
+import org.jivesoftware.smack.packet.Message;
+import org.jivesoftware.smack.packet.StandardExtensionElement;
+import org.jivesoftware.smack.parsing.SmackParsingException;
+import org.jivesoftware.smack.test.util.TestUtils;
+import org.jivesoftware.smack.util.ParserUtils;
+import org.jivesoftware.smack.xml.XmlPullParserException;
+import org.jivesoftware.smackx.stanza_content_encryption.element.ContentElement;
+import org.jivesoftware.smackx.stanza_content_encryption.element.FromAffixElement;
+import org.jivesoftware.smackx.stanza_content_encryption.element.RandomPaddingAffixElement;
+import org.jivesoftware.smackx.stanza_content_encryption.element.TimestampAffixElement;
+import org.jivesoftware.smackx.stanza_content_encryption.element.ToAffixElement;
+
+import org.junit.jupiter.api.Test;
+import org.jxmpp.jid.impl.JidCreate;
+
+public class ContentElementProviderTest {
+
+    @Test
+    public void testParsing() throws XmlPullParserException, IOException, SmackParsingException {
+        String xml = "" +
+                "<content xmlns='urn:xmpp:sce:0'>\n" +
+                "  <payload>\n" +
+                "    <body xmlns='jabber:client'>Have you seen that new movie?</body>\n" +
+                "    <x xmlns='jabber:x:oob'>\n" +
+                "      <url>https://en.wikipedia.org/wiki/Fight_Club#Plot</url>\n" +
+                "    </x>\n" +
+                "  </payload>\n" +
+                "  <from jid='ladymacbeth@shakespear.lit/castle'/>\n" +
+                "  <to jid='doctor@shakespeare.lit/pda'/>\n" +
+                "  <time stamp='1993-10-12T03:13:10.000+00:00'/>\n" +
+                "  <rpad>A98D7KJF1ASDVG232sdff341</rpad>\n" +
+                "</content>";
+
+        ContentElementProvider provider = new ContentElementProvider();
+        ContentElement contentElement = provider.parse(TestUtils.getParser(xml));
+
+        assertNotNull(contentElement);
+
+        assertEquals(4, contentElement.getAffixElements().size());
+        assertTrue(contentElement.getAffixElements().contains(
+                new FromAffixElement(JidCreate.from("ladymacbeth@shakespear.lit/castle"))));
+        assertTrue(contentElement.getAffixElements().contains(
+                new ToAffixElement(JidCreate.from("doctor@shakespeare.lit/pda"))));
+        assertTrue(contentElement.getAffixElements().contains(
+                new TimestampAffixElement(ParserUtils.getDateFromXep82String("1993-10-12T03:13:10.000+00:00"))));
+        assertTrue(contentElement.getAffixElements().contains(
+                new RandomPaddingAffixElement("A98D7KJF1ASDVG232sdff341")));
+
+        assertEquals(2, contentElement.getPayload().getItems().size());
+
+        assertTrue(contentElement.getPayload().getItems().get(0) instanceof Message.Body);
+        Message.Body body = (Message.Body) contentElement.getPayload().getItems().get(0);
+        assertEquals("Have you seen that new movie?", body.getMessage());
+
+        StandardExtensionElement oob = (StandardExtensionElement) contentElement.getPayload().getItems().get(1);
+        assertEquals("x", oob.getElementName());
+        assertEquals("jabber:x:oob", oob.getNamespace());
+        assertEquals("https://en.wikipedia.org/wiki/Fight_Club#Plot", oob.getFirstElement("url").getText());
+    }
+}