xss过滤编码

package com.ipr.common.util;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
*
* Apr 27, 2012 描述: Java防止跨站攻击的
*/
public class HTMLInputFilter {
/**
* flag determining whether to try to make tags when presented with
* "unbalanced" angle brackets (e.g. "" becomes " text
* "). If set to false, unbalanced angle brackets will be html escaped.
*/
protected static final boolean ALWAYS_MAKE_TAGS = true;

/**
* flag determing whether comments are allowed in input String.
*/
protected static final boolean STRIP_COMMENTS = true;

/** regex flag union representing /si modifiers in php * */
protected static final int REGEX_FLAGS_SI = Pattern.CASE_INSENSITIVE | Pattern.DOTALL;

/**
* set of allowed html elements, along with allowed attributes for each
* element *
*/
protected Map> vAllowed;

/** counts of open tags for each (allowable) html element * */
protected Map vTagCounts;

/** html elements which must always be self-closing (e.g. "") * */
protected String[] vSelfClosingTags;

/**
* html elements which must always have separate opening and closing tags
* (e.g. "") *
*/
protected String[] vNeedClosingTags;

/** attributes which should be checked for valid protocols * */
protected String[] vProtocolAtts;

/** allowed protocols * */
protected String[] vAllowedProtocols;

/**
* tags which should be removed if they contain no content (e.g. ""
* or "") *
*/
protected String[] vRemoveBlanks;

/** entities allowed within html markup * */
protected String[] vAllowedEntities;

protected boolean vDebug;

private static HTMLInputFilter filter;

public HTMLInputFilter() {
this(false);
}

public HTMLInputFilter(boolean debug) {
vDebug = debug;

vAllowed = new HashMap>();
vTagCounts = new HashMap();

ArrayList a_atts = new ArrayList();
a_atts.add("href");
a_atts.add("target");
vAllowed.put("a", a_atts);

ArrayList img_atts = new ArrayList();
img_atts.add("src");
img_atts.add("width");
img_atts.add("height");
img_atts.add("alt");
vAllowed.put("img", img_atts);

ArrayList no_atts = new ArrayList();
vAllowed.put("b", no_atts);
vAllowed.put("strong", no_atts);
vAllowed.put("i", no_atts);
vAllowed.put("em", no_atts);

vSelfClosingTags = new String[] { "img" };
vNeedClosingTags = new String[] { "a", "b", "strong", "i", "em" };
vAllowedProtocols = new String[] { "http", "mailto" }; // no ftp.
vProtocolAtts = new String[] { "src", "href" };
vRemoveBlanks = new String[] { "a", "b", "strong", "i", "em" };
vAllowedEntities = new String[] { "amp", "gt", "lt", "quot" };
}

protected void reset() {
vTagCounts = new HashMap();
}

protected void debug(String msg) {
if (vDebug)
System.out.println(msg);
}

// ---------------------------------------------------------------
// my versions of some PHP library functions

private String chr(int decimal) {
return String.valueOf((char) decimal);
}

private String htmlSpecialChars(String s) {
s = s.replaceAll("&", "&");
s = s.replaceAll("\"", """);
s = s.replaceAll("<", "<");
s = s.replaceAll(">", ">");
return s;
}

// ---------------------------------------------------------------

/**
* given a user submitted input String, filter out any invalid or restricted
* html.
*
* @param input
* text (i.e. submitted by a user) than may contain html
* @return "clean" version of input, with only valid, whitelisted html
* elements allowed
*/
public synchronized String filter(String input) {
reset();
String s = input;

debug("************************************************");
debug(" INPUT: " + input);

s = escapeComments(s);
debug(" escapeComments: " + s);

s = balanceHTML(s);
debug(" balanceHTML: " + s);

s = checkTags(s);
debug(" checkTags: " + s);

s = processRemoveBlanks(s);
debug("processRemoveBlanks: " + s);

s = validateEntities(s);
debug(" validateEntites: " + s);
debug("************************************************\n\n");
return s;
}

protected String escapeComments(String s) {
Pattern p = Pattern.compile("", Pattern.DOTALL);
Matcher m = p.matcher(s);
StringBuffer buf = new StringBuffer();
if (m.find()) {
String match = m.group(1); // (.*?)
m.appendReplacement(buf, "");
}
m.appendTail(buf);

return buf.toString();
}

protected String balanceHTML(String s) {
if (ALWAYS_MAKE_TAGS) {
//
// try and form html
//
s = regexReplace("^>", "", s);
s = regexReplace("<([^>]*?)(?=<|$)", "<$1>", s);
s = regexReplace("(^|>)([^<]*?)(?=>)", "$1<$2", s);

} else {
//
// escape stray brackets
//
s = regexReplace("<([^>]*?)(?=<|$)", "<$1", s);
s = regexReplace("(^|>)([^<]*?)(?=>)", "$1$2><", s);

//
// the last regexp causes '<>' entities to appear
// (we need to do a lookahead assertion so that the last bracket can
// be used in the next pass of the regexp)
//
s = s.replaceAll("<>", "");
}
return s;
}

protected String checkTags(String s) {
Pattern p = Pattern.compile("<(.*?)>", Pattern.DOTALL);
Matcher m = p.matcher(s);

StringBuffer buf = new StringBuffer();
while (m.find()) {
String replaceStr = m.group(1);
replaceStr = processTag(replaceStr);
m.appendReplacement(buf, replaceStr);
}
m.appendTail(buf);

s = buf.toString();

// these get tallied in processTag
// (remember to reset before subsequent calls to filter method)
//内容不补齐 2012-4-27
// for (String key : vTagCounts.keySet()) {
// for (int ii = 0; ii < vTagCounts.get(key); ii++) {
// s += "";
// }
// }

return s;
}

protected String processRemoveBlanks(String s) {
for (String tag : vRemoveBlanks) {
s = regexReplace("<" + tag + "(\\s[^>]*)?>", "", s);
s = regexReplace("<" + tag + "(\\s[^>]*)?/>", "", s);
}

return s;
}

protected String regexReplace(String regex_pattern, String replacement,
String s) {
Pattern p = Pattern.compile(regex_pattern);
Matcher m = p.matcher(s);
return m.replaceAll(replacement);
}

protected String processTag(String s) {
// ending tags
Pattern p = Pattern.compile("^/([a-z0-9]+)", REGEX_FLAGS_SI);
Matcher m = p.matcher(s);
if (m.find()) {
String name = m.group(1).toLowerCase();
if (vAllowed.containsKey(name)) {
if (!inArray(name, vSelfClosingTags)) {
if (vTagCounts.containsKey(name)) {
vTagCounts.put(name, vTagCounts.get(name) - 1);
return "";
}
}
}
}

// starting tags
p = Pattern.compile("^([a-z0-9]+)(.*?)(/?)$", REGEX_FLAGS_SI);
m = p.matcher(s);
if (m.find()) {
String name = m.group(1).toLowerCase();
String body = m.group(2);
String ending = m.group(3);

// debug( "in a starting tag, name='" + name + "'; body='" + body +
// "'; ending='" + ending + "'" );
if (vAllowed.containsKey(name)) {
String params = "";

Pattern p2 = Pattern.compile("([a-z0-9]+)=([\"'])(.*?)\\2",
REGEX_FLAGS_SI);
Pattern p3 = Pattern.compile("([a-z0-9]+)(=)([^\"\\s']+)",
REGEX_FLAGS_SI);
Matcher m2 = p2.matcher(body);
Matcher m3 = p3.matcher(body);
List paramNames = new ArrayList();
List paramValues = new ArrayList();
while (m2.find()) {
paramNames.add(m2.group(1)); // ([a-z0-9]+)
paramValues.add(m2.group(3)); // (.*?)
}
while (m3.find()) {
paramNames.add(m3.group(1)); // ([a-z0-9]+)
paramValues.add(m3.group(3)); // ([^\"\\s']+)
}

String paramName, paramValue;
for (int ii = 0; ii < paramNames.size(); ii++) {
paramName = paramNames.get(ii).toLowerCase();
paramValue = paramValues.get(ii);

// debug( "paramName='" + paramName + "'" );
// debug( "paramValue='" + paramValue + "'" );
// debug( "allowed? " + vAllowed.get( name ).contains(
// paramName ) );

if (vAllowed.get(name).contains(paramName)) {
if (inArray(paramName, vProtocolAtts)) {
paramValue = processParamProtocol(paramValue);
}
params += " " + paramName + "=\"" + paramValue + "\"";
}
}

if (inArray(name, vSelfClosingTags)) {
ending = " /";
}

if (inArray(name, vNeedClosingTags)) {
ending = "";
}

if (ending == null || ending.length() < 1) {
if (vTagCounts.containsKey(name)) {
vTagCounts.put(name, vTagCounts.get(name) + 1);
} else {
vTagCounts.put(name, 1);
}
} else {
ending = " /";
}
return "<" + name + params + ending + ">";
} else {
return "";
}
}

// comments
p = Pattern.compile("^!--(.*)--$", REGEX_FLAGS_SI);
m = p.matcher(s);
if (m.find()) {
String comment = m.group();
if (STRIP_COMMENTS) {
return "";
} else {
return "<" + comment + ">";
}
}

return "";
}

protected String processParamProtocol(String s) {
s = decodeEntities(s);
Pattern p = Pattern.compile("^([^:]+):", REGEX_FLAGS_SI);
Matcher m = p.matcher(s);
if (m.find()) {
String protocol = m.group(1);
if (!inArray(protocol, vAllowedProtocols)) {
// bad protocol, turn into local anchor link instead
s = "#" + s.substring(protocol.length() + 1, s.length());
if (s.startsWith("#//"))
s = "#" + s.substring(3, s.length());
}
}

return s;
}

protected String decodeEntities(String s) {
StringBuffer buf = new StringBuffer();

Pattern p = Pattern.compile("&#(\\d+);?");
Matcher m = p.matcher(s);
while (m.find()) {
String match = m.group(1);
int decimal = Integer.decode(match).intValue();
m.appendReplacement(buf, chr(decimal));
}
m.appendTail(buf);
s = buf.toString();

buf = new StringBuffer();
p = Pattern.compile("&#x([0-9a-f]+);?");
m = p.matcher(s);
while (m.find()) {
String match = m.group(1);
int decimal = Integer.decode(match).intValue();
m.appendReplacement(buf, chr(decimal));
}
m.appendTail(buf);
s = buf.toString();

buf = new StringBuffer();
p = Pattern.compile("%([0-9a-f]{2});?");
m = p.matcher(s);
while (m.find()) {
String match = m.group(1);
int decimal = Integer.decode(match).intValue();
m.appendReplacement(buf, chr(decimal));
}
m.appendTail(buf);
s = buf.toString();

s = validateEntities(s);
return s;
}

protected String validateEntities(String s) {
// validate entities throughout the string
// Pattern p = Pattern.compile("&([^&;]*)(?=(;|&|$))");
// Matcher m = p.matcher(s);
// if (m.find()) {
// String one = m.group(1); // ([^&;]*)
// String two = m.group(2); // (?=(;|&|$))
// s = checkEntity(one, two);
// }

// validate quotes outside of tags
Pattern p = Pattern.compile("(>|^)([^<]+?)(<|$)", Pattern.DOTALL);
Matcher m = p.matcher(s);
StringBuffer buf = new StringBuffer();
if (m.find()) {
String one = m.group(1); // (>|^)
String two = m.group(2); // ([^<]+?)
String three = m.group(3); // (<|$)
m.appendReplacement(buf, one + two.replaceAll("\"", """)
+ three);
}
m.appendTail(buf);

return s;
}

protected String checkEntity(String preamble, String term) {
if (!term.equals(";")) {
return "&" + preamble;
}

if (isValidEntity(preamble)) {
return "&" + preamble;
}

return "&" + preamble;
}

protected boolean isValidEntity(String entity) {
return inArray(entity, vAllowedEntities);
}

private boolean inArray(String s, String[] array) {
for (String item : array)
if (item != null && item.equals(s))
return true;

return false;
}

/**
* 作者: huangqj
* 版本: Apr 27, 2012 11:31:51 AM v1.0
* 日期: Apr 27, 2012
* 参数: @param str
* 参数: @return
* 描述: 过滤
*/
public static String doFilter(String str){
if(str == null || str.trim().length() == 0)
return null;

if(filter == null){
filter = new HTMLInputFilter();
}
String filteredInput = filter.filter(str);
return filteredInput;
}

public static void main(String args[]){
String result = HTMLInputFilter.doFilter("");
System.out.println(result);
// result = HTMLInputFilter.doFilter("");
// System.out.println(result);
}
}