Java项目中XSS过滤器的使用方法。
简单介绍：
XSS : 跨站脚本攻击(Cross Site Scripting)，为不和层叠样式表(Cascading Style Sheets, CSS)的缩写混淆，故将跨站脚本攻击缩写为XSS。恶意攻击者往Web页面里插入恶意html代码，当用户浏览该页之时，嵌入其中Web里面的html代码会被执行，从而达到恶意攻击用户的特殊目的。
sql注入
所谓SQL注入，就是通过把SQL命令插入到Web表单提交或输入域名或页面请求的查询字符串，最终达到欺骗服务器执行恶意的SQL命令。具体来说，它是利用现有应用程序，将（恶意）的SQL命令注入到后台数据库引擎执行的能力，它可以通过在Web表单中输入（恶意）SQL语句得到一个存在安全漏洞的网站上的数据库，而不是按照设计者意图去执行SQL语句。
实现方式，共三步：
第一步：配置web.xml
<filter> <filter-name>xssFilter</filter-name> <filter-class>com.wfcm.xss.XssFilter</filter-class> </filter> <filter-mapping> <filter-name>xssFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>
第二步：过滤工具类
1.XSSFilter.java
package com.wfcm.xss; import javax.servlet.*; import javax.servlet.http.HttpServletRequest; import java.io.IOException; /** * xss过滤 * @author xlf * @email xlfbe696@gmail.com * @date 2017年4月19日 上午10:41:42 */ public class XssFilter implements Filter { @Override public void init(FilterConfig config) throws ServletException { } 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() { } }
2.XssHttpServletRequestWrapper
package com.wfcm.xss; import org.apache.commons.lang.StringEscapeUtils; import org.apache.commons.lang.StringUtils; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletRequestWrapper; import java.util.LinkedHashMap; import java.util.Map; public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper { // 没被包装过的HttpServletRequest（特殊场景，需求自己过滤） HttpServletRequest orgRequest; // html过滤 private final static HTMLFilter htmlFilter = new HTMLFilter(); public XssHttpServletRequestWrapper(HttpServletRequest request) { super(request); orgRequest = request; } @Override public String getParameter(String name) { String value = super.getParameter(xssEncode(name)); if (StringUtils.isNotBlank(value)) { value =xssEncode(value); } //SQL注入检查 // value = SQLFilter.sqlInject(value); value = SQLFilter.sqlInject(value); return StringEscapeUtils.unescapeHtml(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]); //SQL注入检查 // parameters[i] = SQLFilter.sqlInject(parameters[i]); parameters[i] = SQLFilter.sqlInject(parameters[i]); parameters[i] = StringEscapeUtils.unescapeHtml(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]); //SQL注入检查 // values[i] = SQLFilter.sqlInject(values[i]); values[i] = SQLFilter.sqlInject(values[i]); values[i] = StringEscapeUtils.unescapeHtml(values[i]); } map.put(key, values); } return map; } @Override public String getHeader(String name) { String value = super.getHeader(xssEncode(name)); if (StringUtils.isNotBlank(value)) { value = xssEncode(value); } //SQL注入检查 // value = SQLFilter.sqlInject(value); value = SQLFilter.sqlInject(value); return StringEscapeUtils.unescapeHtml(value); } private String xssEncode(String input) { return htmlFilter.filter(input); } /** * 获取最原始的request */ public HttpServletRequest getOrgRequest() { return orgRequest; } /** * 获取最原始的request */ public static HttpServletRequest getOrgRequest(HttpServletRequest request) { if (request instanceof XssHttpServletRequestWrapper) { return ((XssHttpServletRequestWrapper) request).getOrgRequest(); } return request; } }
3.HTMLFilter
package com.wfcm.xss; import java.util.ArrayList; import java.util.Collections; import java.util.HashMap; import java.util.List; import java.util.Map; 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; /** * * HTML filtering utility for protecting against XSS (Cross Site Scripting). * * This code is licensed LGPLv3 * * This code is a Java port of the original work in PHP by Cal Hendersen. * http://code.iamcal.com/php/lib_filter/ * * The trickiest part of the translation was handling the differences in regex handling * between PHP and Java. These resources were helpful in the process: * * http://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.html * http://us2.php.net/manual/en/reference.pcre.pattern.modifiers.php * http://www.regular-expressions.info/modifiers.html * * A note on naming conventions: instance variables are prefixed with a "v"; global * constants are in all caps. * * Sample use: * String input = ... * String clean = new HTMLFilter().filter( input ); * * The class is not thread safe. Create a new instance if in doubt. * * If you find bugs or have suggestions on improvement (especially regarding * performance), please contact us. The latest version of this * source, and our contact details, can be found at http://xss-html-filter.sf.net * * @author Joseph O'Connell * @author Cal Hendersen * @author Michael Semb Wever */ public class HTMLFilter { /** regex flag union representing /si modifiers in php **/ 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("<>"); private static final Pattern P_DOUBLE_QUOT = 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>(); /** set of allowed html elements, along with allowed attributes for each element **/ private final Map<String, List<String>> vAllowed; /** counts of open tags for each (allowable) html element **/ private final Map<String, Integer> vTagCounts = new HashMap<String, Integer>(); /** html elements which must always be self-closing (e.g. "<img />") **/ private final String[] vSelfClosingTags; /** html elements which must always have separate opening and closing tags (e.g. "<b></b>") **/ private final String[] vNeedClosingTags; /** set of disallowed html elements **/ private final String[] vDisallowed; /** attributes which should be checked for valid protocols **/ private final String[] vProtocolAtts; /** allowed protocols **/ private final String[] vAllowedProtocols; /** tags which should be removed if they contain no content (e.g. "<b></b>" or "<b />") **/ private final String[] vRemoveBlanks; /** entities allowed within html markup **/ private final String[] vAllowedEntities; /** flag determining whether comments are allowed in input String. */ private final boolean stripComment; private final boolean encodeQuotes; private boolean vDebug = false; /** * flag determining whether to try to make tags when presented with "unbalanced" * angle brackets (e.g. "<b text </b>" becomes "<b> text </b>"). If set to false, * unbalanced angle brackets will be html escaped. */ private final boolean alwaysMakeTags; /** Default constructor. * */ 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; } /** Set debug flag to true. Otherwise use default settings. See the default constructor. * * @param debug turn debug on with a true argument */ public HTMLFilter(final boolean debug) { this(); vDebug = debug; } /** Map-parameter configurable constructor. * * @param conf map containing configuration. keys match field names. */ 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; } //--------------------------------------------------------------- /** * 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 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("************************************************ "); 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)); } }
4.SQLFilter
package com.wfcm.xss; import org.apache.commons.lang.StringUtils; import com.wfcm.utils.RRException; /** * sql过滤 * * @author xlf * @email xlfbe696@gmail.com * @date 2017年4月19日 上午10:41:25 */ public class SQLFilter { /** * SQL注入过滤 * * @param str * 待验证的字符串 */ public static String sqlInject(String str) { if (StringUtils.isBlank(str)) { return null; } // 去掉'|"|;|字符 str = StringUtils.replace(str, "'", ""); str = StringUtils.replace(str, """, ""); str = StringUtils.replace(str, ";", ""); str = StringUtils.replace(str, "\", ""); // 转换成小写 str = str.toLowerCase(); // 非法字符 String[] keywords = { "master", "truncate", "insert", "select", "delete", "update", "declare", "alert", "create", "drop" }; // 判断是否包含非法字符 for (String keyword : keywords) { if (str.equals(keyword)) { throw new RRException("包含非法字符", 1); } } return str; } }
第三步：大功告成！！