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/*
This file is part of the iText (R) project.
Copyright (c) 1998-2021 iText Group NV
Authors: iText Software.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License version 3
as published by the Free Software Foundation with the addition of the
following permission added to Section 15 as permitted in Section 7(a):
FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
OF THIRD PARTY RIGHTS
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program; if not, see http://www.gnu.org/licenses or write to
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*/
package com.itextpdf.styledxmlparser.jsoup.safety;
import com.itextpdf.styledxmlparser.jsoup.Jsoup;
import com.itextpdf.styledxmlparser.jsoup.helper.Validate;
import com.itextpdf.styledxmlparser.jsoup.nodes.Attribute;
import com.itextpdf.styledxmlparser.jsoup.nodes.Attributes;
import com.itextpdf.styledxmlparser.jsoup.nodes.DataNode;
import com.itextpdf.styledxmlparser.jsoup.nodes.Document;
import com.itextpdf.styledxmlparser.jsoup.nodes.Element;
import com.itextpdf.styledxmlparser.jsoup.nodes.Node;
import com.itextpdf.styledxmlparser.jsoup.nodes.TextNode;
import com.itextpdf.styledxmlparser.jsoup.parser.Tag;
import com.itextpdf.styledxmlparser.jsoup.select.NodeTraversor;
import com.itextpdf.styledxmlparser.jsoup.select.NodeVisitor;
/**
* The whitelist based HTML cleaner. Use to ensure that end-user provided HTML contains only the elements and attributes
* that you are expecting; no junk, and no cross-site scripting attacks!
*
* The HTML cleaner parses the input as HTML and then runs it through a white-list, so the output HTML can only contain
* HTML that is allowed by the whitelist.
*
* It is assumed that the input HTML is a body fragment; the clean methods only pull from the source's body, and the
* canned white-lists only allow body contained tags.
*
* Rather than interacting directly with a Cleaner object, generally see the {@code clean} methods in {@link Jsoup}.
*/
public class Cleaner {
private Whitelist whitelist;
/**
* Create a new cleaner, that sanitizes documents using the supplied whitelist.
* @param whitelist white-list to clean with
*/
public Cleaner(Whitelist whitelist) {
Validate.notNull(whitelist);
this.whitelist = whitelist;
}
/**
* Creates a new, clean document, from the original dirty document, containing only elements allowed by the whitelist.
* The original document is not modified. Only elements from the dirt document's body are used.
* @param dirtyDocument Untrusted base document to clean.
* @return cleaned document.
*/
public Document clean(Document dirtyDocument) {
Validate.notNull(dirtyDocument);
Document clean = Document.createShell(dirtyDocument.baseUri());
if (dirtyDocument.body() != null) // frameset documents won't have a body. the clean doc will have empty body.
copySafeNodes(dirtyDocument.body(), clean.body());
return clean;
}
/**
* Determines if the input document is valid, against the whitelist. It is considered valid if all the tags and attributes
* in the input HTML are allowed by the whitelist.
*
* This method can be used as a validator for user input forms. An invalid document will still be cleaned successfully
* using the {@link #clean(Document)} document. If using as a validator, it is recommended to still clean the document
* to ensure enforced attributes are set correctly, and that the output is tidied.
*
* @param dirtyDocument document to test
* @return true if no tags or attributes need to be removed; false if they do
*/
public boolean isValid(Document dirtyDocument) {
Validate.notNull(dirtyDocument);
Document clean = Document.createShell(dirtyDocument.baseUri());
int numDiscarded = copySafeNodes(dirtyDocument.body(), clean.body());
return numDiscarded == 0;
}
/**
* Iterates the input and copies trusted nodes (tags, attributes, text) into the destination.
*/
private final class CleaningVisitor implements NodeVisitor {
int numDiscarded = 0;
final Element root;
Element destination; // current element to append nodes to
CleaningVisitor(Element root, Element destination) {
this.root = root;
this.destination = destination;
}
public void head(Node source, int depth) {
if (source instanceof Element) {
Element sourceEl = (Element) source;
if (whitelist.isSafeTag(sourceEl.tagName())) { // safe, clone and copy safe attrs
ElementMeta meta = createSafeElement(sourceEl);
Element destChild = meta.el;
destination.appendChild(destChild);
numDiscarded += meta.numAttribsDiscarded;
destination = destChild;
} else if (source != root) { // not a safe tag, so don't add. don't count root against discarded.
numDiscarded++;
}
} else if (source instanceof TextNode) {
TextNode sourceText = (TextNode) source;
TextNode destText = new TextNode(sourceText.getWholeText(), source.baseUri());
destination.appendChild(destText);
} else if (source instanceof DataNode && whitelist.isSafeTag(source.parent().nodeName())) {
DataNode sourceData = (DataNode) source;
DataNode destData = new DataNode(sourceData.getWholeData(), source.baseUri());
destination.appendChild(destData);
} else { // else, we don't care about comments, xml proc instructions, etc
numDiscarded++;
}
}
public void tail(Node source, int depth) {
if (source instanceof Element && whitelist.isSafeTag(source.nodeName())) {
destination = (Element) destination.parent(); // would have descended, so pop destination stack
}
}
}
private int copySafeNodes(Element source, Element dest) {
CleaningVisitor cleaningVisitor = new CleaningVisitor(source, dest);
NodeTraversor traversor = new NodeTraversor(cleaningVisitor);
traversor.traverse(source);
return cleaningVisitor.numDiscarded;
}
private ElementMeta createSafeElement(Element sourceEl) {
String sourceTag = sourceEl.tagName();
Attributes destAttrs = new Attributes();
Element dest = new Element(Tag.valueOf(sourceTag), sourceEl.baseUri(), destAttrs);
int numDiscarded = 0;
Attributes sourceAttrs = sourceEl.attributes();
for (Attribute sourceAttr : sourceAttrs) {
if (whitelist.isSafeAttribute(sourceTag, sourceEl, sourceAttr))
destAttrs.put(sourceAttr);
else
numDiscarded++;
}
Attributes enforcedAttrs = whitelist.getEnforcedAttributes(sourceTag);
destAttrs.addAll(enforcedAttrs);
return new ElementMeta(dest, numDiscarded);
}
private static class ElementMeta {
Element el;
int numAttribsDiscarded;
ElementMeta(Element el, int numAttribsDiscarded) {
this.el = el;
this.numAttribsDiscarded = numAttribsDiscarded;
}
}
}