289 lines
9.9 KiB
Java
289 lines
9.9 KiB
Java
/**
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*
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* Copyright 2020 Paul Schaub
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.jivesoftware.smackx.stanza_content_encryption.element;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.Collections;
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import java.util.Date;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Set;
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import javax.xml.namespace.QName;
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import org.jivesoftware.smack.packet.ExtensionElement;
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import org.jivesoftware.smack.packet.XmlEnvironment;
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import org.jivesoftware.smack.util.Objects;
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import org.jivesoftware.smack.util.XmlStringBuilder;
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import org.jivesoftware.smackx.address.packet.MultipleAddresses;
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import org.jivesoftware.smackx.hints.element.MessageProcessingHint;
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import org.jivesoftware.smackx.sid.element.StanzaIdElement;
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import org.jxmpp.jid.Jid;
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/**
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* Extension element that holds the payload element, as well as a list of affix elements.
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* In SCE, the XML representation of this element is what will be encrypted using the encryption mechanism of choice.
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*/
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public class ContentElement implements ExtensionElement {
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private static final String NAMESPACE_UNVERSIONED = "urn:xmpp:sce";
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public static final String NAMESPACE_0 = NAMESPACE_UNVERSIONED + ":0";
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public static final String NAMESPACE = NAMESPACE_0;
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public static final String ELEMENT = "content";
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public static final QName QNAME = new QName(NAMESPACE, ELEMENT);
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private final PayloadElement payload;
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private final List<AffixElement> affixElements;
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ContentElement(PayloadElement payload, List<AffixElement> affixElements) {
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this.payload = payload;
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this.affixElements = Collections.unmodifiableList(affixElements);
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}
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/**
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* Return the {@link PayloadElement} which holds the sensitive payload extensions.
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*
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* @return payload element
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*/
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public PayloadElement getPayload() {
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return payload;
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}
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/**
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* Return a list of affix elements.
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* Those are elements that need to be verified upon reception by the encryption mechanisms implementation.
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*
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* @see <a href="https://xmpp.org/extensions/xep-0420.html#affix_elements">
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* XEP-0420: Stanza Content Encryption - §4. Affix Elements</a>
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*
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* @return list of affix elements
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*/
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public List<AffixElement> getAffixElements() {
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return affixElements;
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}
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@Override
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public String getNamespace() {
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return NAMESPACE;
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}
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@Override
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public String getElementName() {
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return ELEMENT;
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}
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@Override
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public XmlStringBuilder toXML(XmlEnvironment xmlEnvironment) {
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XmlStringBuilder xml = new XmlStringBuilder(this).rightAngleBracket();
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xml.append(affixElements);
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xml.append(payload);
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return xml.closeElement(this);
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}
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@Override
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public QName getQName() {
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return QNAME;
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}
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/**
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* Return a {@link Builder} that can be used to build the {@link ContentElement}.
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* @return builder
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*/
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public static Builder builder() {
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return new Builder();
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}
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public static final class Builder {
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private static final Set<String> BLACKLISTED_NAMESPACES = Collections.singleton(MessageProcessingHint.NAMESPACE);
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private static final Set<QName> BLACKLISTED_QNAMES = Collections.unmodifiableSet(new HashSet<>(Arrays.asList(
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StanzaIdElement.QNAME,
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MultipleAddresses.QNAME
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)));
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private FromAffixElement from = null;
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private TimestampAffixElement timestamp = null;
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private RandomPaddingAffixElement rpad = null;
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private final List<AffixElement> otherAffixElements = new ArrayList<>();
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private final List<ExtensionElement> payloadItems = new ArrayList<>();
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private Builder() {
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}
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/**
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* Add an affix element of type 'to' which addresses one recipient.
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* The jid in the 'to' element SHOULD be a bare jid.
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*
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* @param jid jid
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* @return builder
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*/
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public Builder addTo(Jid jid) {
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return addTo(new ToAffixElement(jid));
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}
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/**
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* Add an affix element of type 'to' which addresses one recipient.
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*
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* @param to affix element
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* @return builder
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*/
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public Builder addTo(ToAffixElement to) {
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this.otherAffixElements.add(Objects.requireNonNull(to, "'to' affix element MUST NOT be null."));
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return this;
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}
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/**
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* Set the senders jid as a 'from' affix element.
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*
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* @param jid jid of the sender
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* @return builder
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*/
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public Builder setFrom(Jid jid) {
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return setFrom(new FromAffixElement(jid));
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}
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/**
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* Set the senders jid as a 'from' affix element.
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*
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* @param from affix element
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* @return builder
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*/
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public Builder setFrom(FromAffixElement from) {
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this.from = Objects.requireNonNull(from, "'form' affix element MUST NOT be null.");
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return this;
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}
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/**
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* Set the given date as a 'time' affix element.
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*
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* @param date timestamp as date
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* @return builder
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*/
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public Builder setTimestamp(Date date) {
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return setTimestamp(new TimestampAffixElement(date));
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}
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/**
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* Set the timestamp of the message as a 'time' affix element.
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*
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* @param timestamp timestamp affix element
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* @return builder
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*/
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public Builder setTimestamp(TimestampAffixElement timestamp) {
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this.timestamp = Objects.requireNonNull(timestamp, "'time' affix element MUST NOT be null.");
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return this;
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}
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/**
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* Set some random length random content padding.
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*
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* @return builder
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*/
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public Builder setRandomPadding() {
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this.rpad = new RandomPaddingAffixElement();
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return this;
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}
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/**
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* Set the given string as padding.
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* The padding should be of length between 1 and 200 characters.
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*
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* @param padding padding string
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* @return builder
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*/
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public Builder setRandomPadding(String padding) {
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return setRandomPadding(new RandomPaddingAffixElement(padding));
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}
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/**
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* Set a padding affix element.
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*
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* @param padding affix element
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* @return builder
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*/
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public Builder setRandomPadding(RandomPaddingAffixElement padding) {
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this.rpad = Objects.requireNonNull(padding, "'rpad' affix element MUST NOT be empty.");
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return this;
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}
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/**
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* Add an additional, SCE profile specific affix element.
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*
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* @param customAffixElement additional affix element
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* @return builder
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*/
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public Builder addFurtherAffixElement(AffixElement customAffixElement) {
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this.otherAffixElements.add(Objects.requireNonNull(customAffixElement,
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"Custom affix element MUST NOT be null."));
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return this;
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}
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/**
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* Add a payload item as child element of the payload element.
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* There are some items that are not allowed as payload.
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* Adding those will throw an exception.
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*
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* @see <a href="https://xmpp.org/extensions/xep-0420.html#server-processed">
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* XEP-0420: Stanza Content Encryption - §9. Server-processed Elements</a>
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*
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* @param payloadItem extension element
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* @return builder
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* @throws IllegalArgumentException in case an extension element from the blacklist is added.
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*/
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public Builder addPayloadItem(ExtensionElement payloadItem) {
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Objects.requireNonNull(payloadItem, "Payload item MUST NOT be null.");
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this.payloadItems.add(checkForIllegalPayloadsAndPossiblyThrow(payloadItem));
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return this;
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}
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/**
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* Construct a content element from this builder.
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*
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* @return content element
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*/
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public ContentElement build() {
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List<AffixElement> allAffixElements = collectAffixElements();
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PayloadElement payloadElement = new PayloadElement(payloadItems);
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return new ContentElement(payloadElement, allAffixElements);
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}
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private static ExtensionElement checkForIllegalPayloadsAndPossiblyThrow(ExtensionElement payloadItem) {
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QName qName = payloadItem.getQName();
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if (BLACKLISTED_QNAMES.contains(qName)) {
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throw new IllegalArgumentException("Element identified by " + qName +
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" is not allowed as payload item. See https://xmpp.org/extensions/xep-0420.html#server-processed");
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}
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String namespace = payloadItem.getNamespace();
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if (BLACKLISTED_NAMESPACES.contains(namespace)) {
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throw new IllegalArgumentException("Elements of namespace '" + namespace +
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"' are not allowed as payload items. See https://xmpp.org/extensions/xep-0420.html#server-processed");
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}
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return payloadItem;
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}
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private List<AffixElement> collectAffixElements() {
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List<AffixElement> allAffixElements = new ArrayList<>(Arrays.asList(rpad, from, timestamp));
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allAffixElements.addAll(otherAffixElements);
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return allAffixElements;
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}
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}
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}
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