过滤xss攻击的方法：
XSS过滤器示例代码：
package com.devframe.filter;import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;public class XssFilter implements Filter {@Override
public void init(FilterConfig config) {
}@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
XssHttpServletRequestWrapper xssRequest = new XssHttpServletRequestWrapper(
(HttpServletRequest) request);
chain.doFilter(xssRequest, response);
}@Override
public void destroy() {
}}
request进行XSS过滤，代码：
package com.devframe.filter;import org.apache.commons.io.IOUtils;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.util.StringUtils;import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.util.LinkedHashMap;
import java.util.Map;public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper {
private HttpServletRequest orgRequest;
private final static HTMLFilter HTML_FILTER = new HTMLFilter();
XssHttpServletRequestWrapper(HttpServletRequest request) throws IllegalArgumentException {
super(request);
orgRequest = request;
}@Override
public ServletInputStream getInputStream() throws IOException {
//非json类型，直接返回
if(!super.getHeader(HttpHeaders.CONTENT_TYPE).equalsIgnoreCase(MediaType.APPLICATION_JSON_VALUE)){
return super.getInputStream();
}//为空，直接返回
String json = IOUtils.toString(super.getInputStream(), "utf-8");
if (!StringUtils.hasText(json)) {
return super.getInputStream();
}//xss过滤
json = xssEncode(json);
final ByteArrayInputStream bis = new ByteArrayInputStream(json.getBytes("utf-8"));
return new ServletInputStream() {
@Override
public boolean isFinished() {
return true;
}@Override
public boolean isReady() {
return true;
}@Override
public void setReadListener(ReadListener readListener) {
}@Override
public int read() {
return bis.read();
}
};
}
@Override
public String getParameter(String name) {
String value = super.getParameter(xssEncode(name));
if (StringUtils.hasText(value)) {
value = xssEncode(value);
}
return value;
}
@Override
public String[] getParameterValues(String name) {
String[] parameters = super.getParameterValues(name);
if (parameters == null || parameters.length == 0) {
return null;
}for (int i = 0; i < parameters.length; i++) {
parameters[i] = xssEncode(parameters[i]);
}
return parameters;
}
@Override
public Map<String,String[]> getParameterMap() {
Map<String,String[]> map = new LinkedHashMap<>();
Map<String,String[]> parameters = super.getParameterMap();
for (String key : parameters.keySet()) {
String[] values = parameters.get(key);
for (int i = 0; i < values.length; i++) {
values[i] = xssEncode(values[i]);
}
map.put(key, values);
}
return map;
}
@Override
public String getHeader(String name) {
String value = super.getHeader(xssEncode(name));
if (StringUtils.hasText(value)) {
value = xssEncode(value);
}
return value;
}private String xssEncode(String input) {
return HTML_FILTER.filter(input);
}
public HttpServletRequest getOrgRequest() {
return orgRequest;
}
public static HttpServletRequest getOrgRequest(HttpServletRequest request) {
if (request instanceof XssHttpServletRequestWrapper) {
return ((XssHttpServletRequestWrapper) request).getOrgRequest();
}
return request;
}
}
XSS过滤工具类，示例代码：
package com.devframe.filter;import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.logging.Logger;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public final class HTMLFilter {
private static final int REGEX_FLAGS_SI = Pattern.CASE_INSENSITIVE | Pattern.DOTALL;
private static final Pattern P_COMMENTS = Pattern.compile("<!--(.*?)-->", Pattern.DOTALL);
private static final Pattern P_COMMENT = Pattern.compile("^!--(.*)--$", REGEX_FLAGS_SI);
private static final Pattern P_TAGS = Pattern.compile("<(.*?)>", Pattern.DOTALL);
private static final Pattern P_END_TAG = Pattern.compile("^/([a-z0-9]+)", REGEX_FLAGS_SI);
private static final Pattern P_START_TAG = Pattern.compile("^([a-z0-9]+)(.*?)(/?)$", REGEX_FLAGS_SI);
private static final Pattern P_QUOTED_ATTRIBUTES = Pattern.compile("([a-z0-9]+)=([\"'])(.*?)\\2", REGEX_FLAGS_SI);
private static final Pattern P_UNQUOTED_ATTRIBUTES = Pattern.compile("([a-z0-9]+)(=)([^\"\\s']+)", REGEX_FLAGS_SI);
private static final Pattern P_PROTOCOL = Pattern.compile("^([^:]+):", REGEX_FLAGS_SI);
private static final Pattern P_ENTITY = Pattern.compile("&#(\\d+);?");
private static final Pattern P_ENTITY_UNICODE = Pattern.compile("&#x([0-9a-f]+);?");
private static final Pattern P_ENCODE = Pattern.compile("%([0-9a-f]{2});?");
private static final Pattern P_VALID_ENTITIES = Pattern.compile("&([^&;]*)(?=(;|&|$))");
private static final Pattern P_VALID_QUOTES = Pattern.compile("(>|^)([^<]+?)(<|$)", Pattern.DOTALL);
private static final Pattern P_END_ARROW = Pattern.compile("^>");
private static final Pattern P_BODY_TO_END = Pattern.compile("<([^>]*?)(?=<|$)");
private static final Pattern P_XML_CONTENT = Pattern.compile("(^|>)([^<]*?)(?=>)");
private static final Pattern P_STRAY_LEFT_ARROW = Pattern.compile("<([^>]*?)(?=<|$)");
private static final Pattern P_STRAY_RIGHT_ARROW = Pattern.compile("(^|>)([^<]*?)(?=>)");
private static final Pattern P_AMP = Pattern.compile("&");
private static final Pattern P_QUOTE = Pattern.compile("<");
private static final Pattern P_LEFT_ARROW = Pattern.compile("<");
private static final Pattern P_RIGHT_ARROW = Pattern.compile(">");
private static final Pattern P_BOTH_ARROWS = Pattern.compile("<>");// @xxx could grow large... maybe use sesat's ReferenceMap
private static final ConcurrentMap<String,Pattern> P_REMOVE_PAIR_BLANKS = new ConcurrentHashMap<String, Pattern>();
private static final ConcurrentMap<String,Pattern> P_REMOVE_SELF_BLANKS = new ConcurrentHashMap<String, Pattern>();
private final Map<String, List<String>> vAllowed;
private final Map<String, Integer> vTagCounts = new HashMap<String, Integer>();
private final String[] vSelfClosingTags;
private final String[] vNeedClosingTags;
private final String[] vDisallowed;
private final String[] vProtocolAtts;
private final String[] vAllowedProtocols;
private final String[] vRemoveBlanks;
private final String[] vAllowedEntities;
private final boolean stripComment;
private final boolean encodeQuotes;
private boolean vDebug = false;
private final boolean alwaysMakeTags;
public HTMLFilter() {
vAllowed = new HashMap<>();final ArrayList<String> a_atts = new ArrayList<String>();
a_atts.add("href");
a_atts.add("target");
vAllowed.put("a", a_atts);final ArrayList<String> img_atts = new ArrayList<String>();
img_atts.add("src");
img_atts.add("width");
img_atts.add("height");
img_atts.add("alt");
vAllowed.put("img", img_atts);final ArrayList<String> no_atts = new ArrayList<String>();
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"};
vDisallowed = new String[]{};
vAllowedProtocols = new String[]{"http", "mailto", "https"}; // no ftp.
vProtocolAtts = new String[]{"src", "href"};
vRemoveBlanks = new String[]{"a", "b", "strong", "i", "em"};
vAllowedEntities = new String[]{"amp", "gt", "lt", "quot"};
stripComment = true;
encodeQuotes = true;
alwaysMakeTags = true;
}
public HTMLFilter(final boolean debug) {
this();
vDebug = debug;}
public HTMLFilter(final Map<String,Object> conf) {assert conf.containsKey("vAllowed") : "configuration requires vAllowed";
assert conf.containsKey("vSelfClosingTags") : "configuration requires vSelfClosingTags";
assert conf.containsKey("vNeedClosingTags") : "configuration requires vNeedClosingTags";
assert conf.containsKey("vDisallowed") : "configuration requires vDisallowed";
assert conf.containsKey("vAllowedProtocols") : "configuration requires vAllowedProtocols";
assert conf.containsKey("vProtocolAtts") : "configuration requires vProtocolAtts";
assert conf.containsKey("vRemoveBlanks") : "configuration requires vRemoveBlanks";
assert conf.containsKey("vAllowedEntities") : "configuration requires vAllowedEntities";vAllowed = Collections.unmodifiableMap((HashMap<String, List<String>>) conf.get("vAllowed"));
vSelfClosingTags = (String[]) conf.get("vSelfClosingTags");
vNeedClosingTags = (String[]) conf.get("vNeedClosingTags");
vDisallowed = (String[]) conf.get("vDisallowed");
vAllowedProtocols = (String[]) conf.get("vAllowedProtocols");
vProtocolAtts = (String[]) conf.get("vProtocolAtts");
vRemoveBlanks = (String[]) conf.get("vRemoveBlanks");
vAllowedEntities = (String[]) conf.get("vAllowedEntities");
stripComment = conf.containsKey("stripComment") ? (Boolean) conf.get("stripComment") : true;
encodeQuotes = conf.containsKey("encodeQuotes") ? (Boolean) conf.get("encodeQuotes") : true;
alwaysMakeTags = conf.containsKey("alwaysMakeTags") ? (Boolean) conf.get("alwaysMakeTags") : true;
}private void reset() {
vTagCounts.clear();
}private void debug(final String msg) {
if (vDebug) {
Logger.getAnonymousLogger().info(msg);
}
}//---------------------------------------------------------------
// my versions of some PHP library functions
public static String chr(final int decimal) {
return String.valueOf((char) decimal);
}public static String htmlSpecialChars(final String s) {
String result = s;
result = regexReplace(P_AMP, "&", result);
result = regexReplace(P_QUOTE, """, result);
result = regexReplace(P_LEFT_ARROW, "<", result);
result = regexReplace(P_RIGHT_ARROW, ">", result);
return result;
}//---------------------------------------------------------------
public String filter(final 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;
}public boolean isAlwaysMakeTags(){
return alwaysMakeTags;
}public boolean isStripComments(){
return stripComment;
}private String escapeComments(final String s) {
final Matcher m = P_COMMENTS.matcher(s);
final StringBuffer buf = new StringBuffer();
if (m.find()) {
final String match = m.group(1); //(.*?)
m.appendReplacement(buf, Matcher.quoteReplacement("<!--" + htmlSpecialChars(match) + "-->"));
}
m.appendTail(buf);return buf.toString();
}private String balanceHTML(String s) {
if (alwaysMakeTags) {
//
// try and form html
//
s = regexReplace(P_END_ARROW, "", s);
s = regexReplace(P_BODY_TO_END, "<$1>", s);
s = regexReplace(P_XML_CONTENT, "$1<$2", s);} else {
//
// escape stray brackets
//
s = regexReplace(P_STRAY_LEFT_ARROW, "<$1", s);
s = regexReplace(P_STRAY_RIGHT_ARROW, "$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 = regexReplace(P_BOTH_ARROWS, "", s);
}return s;
}private String checkTags(String s) {
Matcher m = P_TAGS.matcher(s);final StringBuffer buf = new StringBuffer();
while (m.find()) {
String replaceStr = m.group(1);
replaceStr = processTag(replaceStr);
m.appendReplacement(buf, Matcher.quoteReplacement(replaceStr));
}
m.appendTail(buf);s = buf.toString();// these get tallied in processTag
// (remember to reset before subsequent calls to filter method)
for (String key : vTagCounts.keySet()) {
for (int ii = 0; ii < vTagCounts.get(key); ii++) {
s += "</" + key + ">";
}
}return s;
}private String processRemoveBlanks(final String s) {
String result = s;
for (String tag : vRemoveBlanks) {
if(!P_REMOVE_PAIR_BLANKS.containsKey(tag)){
P_REMOVE_PAIR_BLANKS.putIfAbsent(tag, Pattern.compile("<" + tag + "(\\s[^>]*)?></" + tag + ">"));
}
result = regexReplace(P_REMOVE_PAIR_BLANKS.get(tag), "", result);
if(!P_REMOVE_SELF_BLANKS.containsKey(tag)){
P_REMOVE_SELF_BLANKS.putIfAbsent(tag, Pattern.compile("<" + tag + "(\\s[^>]*)?/>"));
}
result = regexReplace(P_REMOVE_SELF_BLANKS.get(tag), "", result);
}return result;
}private static String regexReplace(final Pattern regex_pattern, final String replacement, final String s) {
Matcher m = regex_pattern.matcher(s);
return m.replaceAll(replacement);
}private String processTag(final String s) {
// ending tags
Matcher m = P_END_TAG.matcher(s);
if (m.find()) {
final String name = m.group(1).toLowerCase();
if (allowed(name)) {
if (!inArray(name, vSelfClosingTags)) {
if (vTagCounts.containsKey(name)) {
vTagCounts.put(name, vTagCounts.get(name) - 1);
return "</" + name + ">";
}
}
}
}// starting tags
m = P_START_TAG.matcher(s);
if (m.find()) {
final String name = m.group(1).toLowerCase();
final String body = m.group(2);
String ending = m.group(3);//debug( "in a starting tag, name='" + name + "'; body='" + body + "'; ending='" + ending + "'" );
if (allowed(name)) {
String params = "";final Matcher m2 = P_QUOTED_ATTRIBUTES.matcher(body);
final Matcher m3 = P_UNQUOTED_ATTRIBUTES.matcher(body);
final List<String> paramNames = new ArrayList<String>();
final List<String> paramValues = new ArrayList<String>();
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 (allowedAttribute(name, 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
m = P_COMMENT.matcher(s);
if (!stripComment && m.find()) {
return "<" + m.group() + ">";
}return "";
}private String processParamProtocol(String s) {
s = decodeEntities(s);
final Matcher m = P_PROTOCOL.matcher(s);
if (m.find()) {
final 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;
}private String decodeEntities(String s) {
StringBuffer buf = new StringBuffer();Matcher m = P_ENTITY.matcher(s);
while (m.find()) {
final String match = m.group(1);
final int decimal = Integer.decode(match).intValue();
m.appendReplacement(buf, Matcher.quoteReplacement(chr(decimal)));
}
m.appendTail(buf);
s = buf.toString();buf = new StringBuffer();
m = P_ENTITY_UNICODE.matcher(s);
while (m.find()) {
final String match = m.group(1);
final int decimal = Integer.valueOf(match, 16).intValue();
m.appendReplacement(buf, Matcher.quoteReplacement(chr(decimal)));
}
m.appendTail(buf);
s = buf.toString();buf = new StringBuffer();
m = P_ENCODE.matcher(s);
while (m.find()) {
final String match = m.group(1);
final int decimal = Integer.valueOf(match, 16).intValue();
m.appendReplacement(buf, Matcher.quoteReplacement(chr(decimal)));
}
m.appendTail(buf);
s = buf.toString();s = validateEntities(s);
return s;
}private String validateEntities(final String s) {
StringBuffer buf = new StringBuffer();// validate entities throughout the string
Matcher m = P_VALID_ENTITIES.matcher(s);
while (m.find()) {
final String one = m.group(1); //([^&;]*)
final String two = m.group(2); //(?=(;|&|$))
m.appendReplacement(buf, Matcher.quoteReplacement(checkEntity(one, two)));
}
m.appendTail(buf);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); //(<|$)
m.appendReplacement(buf, Matcher.quoteReplacement(one + regexReplace(P_QUOTE, """, 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));
}
}
在web.xml配置filter的使用示例：
<filter>
<filter-name>xssFilter</filter-name>
<filter-class>com.devframe.filter.XssFilter</filter-class>
</filter><filter-mapping>
<filter-name>xssFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
