570 lines
19 KiB
Plaintext
570 lines
19 KiB
Plaintext
package com.securityControl.common.core.utils.html;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.concurrent.ConcurrentMap;
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import java.util.regex.Matcher;
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import java.util.regex.Pattern;
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/**
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* HTML过滤器，用于去除XSS漏洞隐患。
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*
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* @author czc
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*/
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public final class HTMLFilter
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{
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/**
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* regex flag union representing /si modifiers in php
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**/
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private static final int REGEX_FLAGS_SI = Pattern.CASE_INSENSITIVE | Pattern.DOTALL;
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private static final Pattern P_COMMENTS = Pattern.compile("<!--(.*?)-->", Pattern.DOTALL);
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private static final Pattern P_COMMENT = Pattern.compile("^!--(.*)--$", REGEX_FLAGS_SI);
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private static final Pattern P_TAGS = Pattern.compile("<(.*?)>", Pattern.DOTALL);
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private static final Pattern P_END_TAG = Pattern.compile("^/([a-z0-9]+)", REGEX_FLAGS_SI);
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private static final Pattern P_START_TAG = Pattern.compile("^([a-z0-9]+)(.*?)(/?)$", REGEX_FLAGS_SI);
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private static final Pattern P_QUOTED_ATTRIBUTES = Pattern.compile("([a-z0-9]+)=([\"'])(.*?)\\2", REGEX_FLAGS_SI);
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private static final Pattern P_UNQUOTED_ATTRIBUTES = Pattern.compile("([a-z0-9]+)(=)([^\"\\s']+)", REGEX_FLAGS_SI);
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private static final Pattern P_PROTOCOL = Pattern.compile("^([^:]+):", REGEX_FLAGS_SI);
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private static final Pattern P_ENTITY = Pattern.compile("&#(\\d+);?");
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private static final Pattern P_ENTITY_UNICODE = Pattern.compile("&#x([0-9a-f]+);?");
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private static final Pattern P_ENCODE = Pattern.compile("%([0-9a-f]{2});?");
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private static final Pattern P_VALID_ENTITIES = Pattern.compile("&([^&;]*)(?=(;|&|$))");
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private static final Pattern P_VALID_QUOTES = Pattern.compile("(>|^)([^<]+?)(<|$)", Pattern.DOTALL);
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private static final Pattern P_END_ARROW = Pattern.compile("^>");
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private static final Pattern P_BODY_TO_END = Pattern.compile("<([^>]*?)(?=<|$)");
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private static final Pattern P_XML_CONTENT = Pattern.compile("(^|>)([^<]*?)(?=>)");
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private static final Pattern P_STRAY_LEFT_ARROW = Pattern.compile("<([^>]*?)(?=<|$)");
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private static final Pattern P_STRAY_RIGHT_ARROW = Pattern.compile("(^|>)([^<]*?)(?=>)");
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private static final Pattern P_AMP = Pattern.compile("&");
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private static final Pattern P_QUOTE = Pattern.compile("\"");
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private static final Pattern P_LEFT_ARROW = Pattern.compile("<");
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private static final Pattern P_RIGHT_ARROW = Pattern.compile(">");
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private static final Pattern P_BOTH_ARROWS = Pattern.compile("<>");
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// @xxx could grow large... maybe use sesat's ReferenceMap
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private static final ConcurrentMap<String, Pattern> P_REMOVE_PAIR_BLANKS = new ConcurrentHashMap<>();
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private static final ConcurrentMap<String, Pattern> P_REMOVE_SELF_BLANKS = new ConcurrentHashMap<>();
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/**
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* set of allowed html elements, along with allowed attributes for each element
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**/
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private final Map<String, List<String>> vAllowed;
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/**
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* counts of open tags for each (allowable) html element
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**/
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private final Map<String, Integer> vTagCounts = new HashMap<>();
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/**
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* html elements which must always be self-closing (e.g. "<img />")
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**/
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private final String[] vSelfClosingTags;
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/**
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* html elements which must always have separate opening and closing tags (e.g. "<b></b>")
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**/
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private final String[] vNeedClosingTags;
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/**
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* set of disallowed html elements
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**/
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private final String[] vDisallowed;
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/**
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* attributes which should be checked for valid protocols
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**/
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private final String[] vProtocolAtts;
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/**
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* allowed protocols
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**/
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private final String[] vAllowedProtocols;
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/**
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* tags which should be removed if they contain no content (e.g. "<b></b>" or "<b />")
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**/
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private final String[] vRemoveBlanks;
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/**
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* entities allowed within html markup
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**/
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private final String[] vAllowedEntities;
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/**
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* flag determining whether comments are allowed in input String.
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*/
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private final boolean stripComment;
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private final boolean encodeQuotes;
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/**
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* flag determining whether to try to make tags when presented with "unbalanced" angle brackets (e.g. "<b text </b>"
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* becomes "<b> text </b>"). If set to false, unbalanced angle brackets will be html escaped.
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*/
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private final boolean alwaysMakeTags;
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/**
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* Default constructor.
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*/
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public HTMLFilter()
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{
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vAllowed = new HashMap<>();
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final ArrayList<String> a_atts = new ArrayList<>();
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a_atts.add("href");
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a_atts.add("target");
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vAllowed.put("a", a_atts);
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final ArrayList<String> img_atts = new ArrayList<>();
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img_atts.add("src");
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img_atts.add("width");
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img_atts.add("height");
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img_atts.add("alt");
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vAllowed.put("img", img_atts);
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final ArrayList<String> no_atts = new ArrayList<>();
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vAllowed.put("b", no_atts);
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vAllowed.put("strong", no_atts);
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vAllowed.put("i", no_atts);
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vAllowed.put("em", no_atts);
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vSelfClosingTags = new String[] { "img" };
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vNeedClosingTags = new String[] { "a", "b", "strong", "i", "em" };
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vDisallowed = new String[] {};
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vAllowedProtocols = new String[] { "http", "mailto", "https" }; // no ftp.
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vProtocolAtts = new String[] { "src", "href" };
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vRemoveBlanks = new String[] { "a", "b", "strong", "i", "em" };
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vAllowedEntities = new String[] { "amp", "gt", "lt", "quot" };
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stripComment = true;
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encodeQuotes = true;
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alwaysMakeTags = false;
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}
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/**
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* Map-parameter configurable constructor.
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*
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* @param conf map containing configuration. keys match field names.
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*/
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@SuppressWarnings("unchecked")
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public HTMLFilter(final Map<String, Object> conf)
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{
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assert conf.containsKey("vAllowed") : "configuration requires vAllowed";
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assert conf.containsKey("vSelfClosingTags") : "configuration requires vSelfClosingTags";
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assert conf.containsKey("vNeedClosingTags") : "configuration requires vNeedClosingTags";
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assert conf.containsKey("vDisallowed") : "configuration requires vDisallowed";
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assert conf.containsKey("vAllowedProtocols") : "configuration requires vAllowedProtocols";
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assert conf.containsKey("vProtocolAtts") : "configuration requires vProtocolAtts";
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assert conf.containsKey("vRemoveBlanks") : "configuration requires vRemoveBlanks";
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assert conf.containsKey("vAllowedEntities") : "configuration requires vAllowedEntities";
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vAllowed = Collections.unmodifiableMap((HashMap<String, List<String>>) conf.get("vAllowed"));
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vSelfClosingTags = (String[]) conf.get("vSelfClosingTags");
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vNeedClosingTags = (String[]) conf.get("vNeedClosingTags");
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vDisallowed = (String[]) conf.get("vDisallowed");
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vAllowedProtocols = (String[]) conf.get("vAllowedProtocols");
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vProtocolAtts = (String[]) conf.get("vProtocolAtts");
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vRemoveBlanks = (String[]) conf.get("vRemoveBlanks");
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vAllowedEntities = (String[]) conf.get("vAllowedEntities");
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stripComment = conf.containsKey("stripComment") ? (Boolean) conf.get("stripComment") : true;
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encodeQuotes = conf.containsKey("encodeQuotes") ? (Boolean) conf.get("encodeQuotes") : true;
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alwaysMakeTags = conf.containsKey("alwaysMakeTags") ? (Boolean) conf.get("alwaysMakeTags") : true;
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}
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private void reset()
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{
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vTagCounts.clear();
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}
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// ---------------------------------------------------------------
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// my versions of some PHP library functions
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public static String chr(final int decimal)
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{
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return String.valueOf((char) decimal);
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}
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public static String htmlSpecialChars(final String s)
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{
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String result = s;
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result = regexReplace(P_AMP, "&", result);
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result = regexReplace(P_QUOTE, """, result);
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result = regexReplace(P_LEFT_ARROW, "<", result);
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result = regexReplace(P_RIGHT_ARROW, ">", result);
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return result;
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}
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// ---------------------------------------------------------------
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/**
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* given a user submitted input String, filter out any invalid or restricted html.
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*
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* @param input text (i.e. submitted by a user) than may contain html
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* @return "clean" version of input, with only valid, whitelisted html elements allowed
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*/
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public String filter(final String input)
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{
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reset();
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String s = input;
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s = escapeComments(s);
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s = balanceHTML(s);
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s = checkTags(s);
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s = processRemoveBlanks(s);
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// s = validateEntities(s);
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return s;
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}
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public boolean isAlwaysMakeTags()
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{
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return alwaysMakeTags;
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}
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public boolean isStripComments()
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{
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return stripComment;
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}
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private String escapeComments(final String s)
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{
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final Matcher m = P_COMMENTS.matcher(s);
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final StringBuffer buf = new StringBuffer();
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if (m.find())
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{
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final String match = m.group(1); // (.*?)
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m.appendReplacement(buf, Matcher.quoteReplacement("<!--" + htmlSpecialChars(match) + "-->"));
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}
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m.appendTail(buf);
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return buf.toString();
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}
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private String balanceHTML(String s)
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{
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if (alwaysMakeTags)
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{
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//
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// try and form html
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//
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s = regexReplace(P_END_ARROW, "", s);
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// 不追加结束标签
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s = regexReplace(P_BODY_TO_END, "<$1>", s);
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s = regexReplace(P_XML_CONTENT, "$1<$2", s);
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}
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else
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{
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//
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// escape stray brackets
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//
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s = regexReplace(P_STRAY_LEFT_ARROW, "<$1", s);
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s = regexReplace(P_STRAY_RIGHT_ARROW, "$1$2><", s);
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//
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// the last regexp causes '<>' entities to appear
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// (we need to do a lookahead assertion so that the last bracket can
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// be used in the next pass of the regexp)
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//
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s = regexReplace(P_BOTH_ARROWS, "", s);
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}
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return s;
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}
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private String checkTags(String s)
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{
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Matcher m = P_TAGS.matcher(s);
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final StringBuffer buf = new StringBuffer();
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while (m.find())
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{
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String replaceStr = m.group(1);
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replaceStr = processTag(replaceStr);
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m.appendReplacement(buf, Matcher.quoteReplacement(replaceStr));
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}
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m.appendTail(buf);
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// these get tallied in processTag
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// (remember to reset before subsequent calls to filter method)
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final StringBuilder sBuilder = new StringBuilder(buf.toString());
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for (String key : vTagCounts.keySet())
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{
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for (int ii = 0; ii < vTagCounts.get(key); ii++)
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{
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sBuilder.append("</").append(key).append(">");
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}
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}
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s = sBuilder.toString();
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return s;
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}
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private String processRemoveBlanks(final String s)
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{
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String result = s;
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for (String tag : vRemoveBlanks)
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{
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if (!P_REMOVE_PAIR_BLANKS.containsKey(tag))
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{
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P_REMOVE_PAIR_BLANKS.putIfAbsent(tag, Pattern.compile("<" + tag + "(\\s[^>]*)?></" + tag + ">"));
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}
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result = regexReplace(P_REMOVE_PAIR_BLANKS.get(tag), "", result);
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if (!P_REMOVE_SELF_BLANKS.containsKey(tag))
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{
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P_REMOVE_SELF_BLANKS.putIfAbsent(tag, Pattern.compile("<" + tag + "(\\s[^>]*)?/>"));
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}
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result = regexReplace(P_REMOVE_SELF_BLANKS.get(tag), "", result);
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}
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return result;
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}
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private static String regexReplace(final Pattern regex_pattern, final String replacement, final String s)
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{
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Matcher m = regex_pattern.matcher(s);
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return m.replaceAll(replacement);
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}
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private String processTag(final String s)
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{
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// ending tags
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Matcher m = P_END_TAG.matcher(s);
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if (m.find())
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{
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final String name = m.group(1).toLowerCase();
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if (allowed(name))
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{
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if (!inArray(name, vSelfClosingTags))
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{
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if (vTagCounts.containsKey(name))
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{
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vTagCounts.put(name, vTagCounts.get(name) - 1);
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return "</" + name + ">";
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}
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}
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}
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}
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// starting tags
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m = P_START_TAG.matcher(s);
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if (m.find())
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{
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final String name = m.group(1).toLowerCase();
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final String body = m.group(2);
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String ending = m.group(3);
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// debug( "in a starting tag, name='" + name + "'; body='" + body + "'; ending='" + ending + "'" );
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if (allowed(name))
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{
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final StringBuilder params = new StringBuilder();
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final Matcher m2 = P_QUOTED_ATTRIBUTES.matcher(body);
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final Matcher m3 = P_UNQUOTED_ATTRIBUTES.matcher(body);
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final List<String> paramNames = new ArrayList<>();
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final List<String> paramValues = new ArrayList<>();
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while (m2.find())
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{
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paramNames.add(m2.group(1)); // ([a-z0-9]+)
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paramValues.add(m2.group(3)); // (.*?)
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}
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while (m3.find())
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{
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paramNames.add(m3.group(1)); // ([a-z0-9]+)
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paramValues.add(m3.group(3)); // ([^\"\\s']+)
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}
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String paramName, paramValue;
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for (int ii = 0; ii < paramNames.size(); ii++)
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{
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paramName = paramNames.get(ii).toLowerCase();
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paramValue = paramValues.get(ii);
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// debug( "paramName='" + paramName + "'" );
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// debug( "paramValue='" + paramValue + "'" );
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// debug( "allowed? " + vAllowed.get( name ).contains( paramName ) );
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if (allowedAttribute(name, paramName))
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{
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if (inArray(paramName, vProtocolAtts))
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{
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paramValue = processParamProtocol(paramValue);
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}
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params.append(' ').append(paramName).append("=\\\"").append(paramValue).append("\\\"");
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}
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}
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if (inArray(name, vSelfClosingTags))
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{
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ending = " /";
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}
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if (inArray(name, vNeedClosingTags))
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{
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ending = "";
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}
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if (ending == null || ending.length() < 1)
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{
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if (vTagCounts.containsKey(name))
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{
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vTagCounts.put(name, vTagCounts.get(name) + 1);
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}
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else
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{
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vTagCounts.put(name, 1);
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}
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}
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else
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{
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ending = " /";
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}
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return "<" + name + params + ending + ">";
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}
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else
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{
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return "";
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}
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}
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// comments
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m = P_COMMENT.matcher(s);
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if (!stripComment && m.find())
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{
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return "<" + m.group() + ">";
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}
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return "";
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}
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private String processParamProtocol(String s)
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{
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s = decodeEntities(s);
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final Matcher m = P_PROTOCOL.matcher(s);
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if (m.find())
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{
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final String protocol = m.group(1);
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if (!inArray(protocol, vAllowedProtocols))
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{
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// bad protocol, turn into local anchor link instead
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s = "#" + s.substring(protocol.length() + 1);
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if (s.startsWith("#//"))
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{
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s = "#" + s.substring(3);
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}
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}
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}
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return s;
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}
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private String decodeEntities(String s)
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{
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StringBuffer buf = new StringBuffer();
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Matcher m = P_ENTITY.matcher(s);
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while (m.find())
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{
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final String match = m.group(1);
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final int decimal = Integer.decode(match).intValue();
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m.appendReplacement(buf, Matcher.quoteReplacement(chr(decimal)));
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}
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m.appendTail(buf);
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s = buf.toString();
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buf = new StringBuffer();
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m = P_ENTITY_UNICODE.matcher(s);
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while (m.find())
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{
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final String match = m.group(1);
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final int decimal = Integer.valueOf(match, 16).intValue();
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m.appendReplacement(buf, Matcher.quoteReplacement(chr(decimal)));
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}
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m.appendTail(buf);
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s = buf.toString();
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buf = new StringBuffer();
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m = P_ENCODE.matcher(s);
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while (m.find())
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{
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final String match = m.group(1);
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final int decimal = Integer.valueOf(match, 16).intValue();
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m.appendReplacement(buf, Matcher.quoteReplacement(chr(decimal)));
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}
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m.appendTail(buf);
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s = buf.toString();
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s = validateEntities(s);
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return s;
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}
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private String validateEntities(final String s)
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{
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StringBuffer buf = new StringBuffer();
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// validate entities throughout the string
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Matcher m = P_VALID_ENTITIES.matcher(s);
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while (m.find())
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{
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final String one = m.group(1); // ([^&;]*)
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final String two = m.group(2); // (?=(;|&|$))
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m.appendReplacement(buf, Matcher.quoteReplacement(checkEntity(one, two)));
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}
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m.appendTail(buf);
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|
||
return encodeQuotes(buf.toString());
|
||
}
|
||
|
||
private String encodeQuotes(final String s)
|
||
{
|
||
if (encodeQuotes)
|
||
{
|
||
StringBuffer buf = new StringBuffer();
|
||
Matcher m = P_VALID_QUOTES.matcher(s);
|
||
while (m.find())
|
||
{
|
||
final String one = m.group(1); // (>|^)
|
||
final String two = m.group(2); // ([^<]+?)
|
||
final String three = m.group(3); // (<|$)
|
||
// 不替换双引号为"，防止json格式无效 regexReplace(P_QUOTE, """, two)
|
||
m.appendReplacement(buf, Matcher.quoteReplacement(one + two + three));
|
||
}
|
||
m.appendTail(buf);
|
||
return buf.toString();
|
||
}
|
||
else
|
||
{
|
||
return s;
|
||
}
|
||
}
|
||
|
||
private String checkEntity(final String preamble, final String term)
|
||
{
|
||
|
||
return ";".equals(term) && isValidEntity(preamble) ? '&' + preamble : "&" + preamble;
|
||
}
|
||
|
||
private boolean isValidEntity(final String entity)
|
||
{
|
||
return inArray(entity, vAllowedEntities);
|
||
}
|
||
|
||
private static boolean inArray(final String s, final String[] array)
|
||
{
|
||
for (String item : array)
|
||
{
|
||
if (item != null && item.equals(s))
|
||
{
|
||
return true;
|
||
}
|
||
}
|
||
return false;
|
||
}
|
||
|
||
private boolean allowed(final String name)
|
||
{
|
||
return (vAllowed.isEmpty() || vAllowed.containsKey(name)) && !inArray(name, vDisallowed);
|
||
}
|
||
|
||
private boolean allowedAttribute(final String name, final String paramName)
|
||
{
|
||
return allowed(name) && (vAllowed.isEmpty() || vAllowed.get(name).contains(paramName));
|
||
}
|
||
} |