簡述Xss
一，什麼是Xss 攻擊
百度百科：
XSS攻擊通常指的是透過利用網頁開發時留下的漏洞，透過巧妙的方法注入惡意指令程式碼到網頁，使使用者載入並執行攻擊者惡意製造的網頁程式。這些惡意網頁程式通常是JavaScript，但實際上也可以包括Java、 VBScript、ActiveX、 Flash 或者甚至是普通的HTML。攻擊成功後，攻擊者可能得到包括但不限於更高的許可權（如執行一些操作）、私密網頁內容、會話和cookie等各種內容。
目前,XSS是駭客最常用來攻擊網際網路的技術之一,其對網際網路安全的危害性在國際排名第二,它是利用Web站點,把病毒混入文字,意圖矇蔽計算機中資訊保安系統的"眼睛",對原網站程式碼進行攻擊,盜取人們的資訊
通俗解釋：
這裡舉一個簡單的例子，就是留言板。我們知道留言板通常的任務就是把使用者留言的內容展示出來。正常情況下，使用者的留言都是正常的語言文字，留言板顯示的內容也就沒毛病。然而這個時候如果有人不按套路出牌，在留言內容中丟進去一行
<script>alert(“hey!you are attacked”)</script>
那麼留言板介面的網頁程式碼就會變成形如以下：
<html>
<head>
<title>留言板</title>
</head>
<body>
<div id=”board”
<script>alert(“hey!you are attacked”)</script>
</div>
</body>
</html>
那麼這個時候問題就來了，當瀏覽器解析到使用者輸入的程式碼那一行時會發生什麼呢？答案很顯然，瀏覽器並不知道這些程式碼改變了原本程式的意圖，會照做彈出一個資訊框。就像這樣。
二，Xss的危害
其實歸根結底，XSS的攻擊方式就是想辦法“教唆”使用者的瀏覽器去執行一些這個網頁中原本不存在的前端程式碼。達到對網頁的攻擊。
儘管一個資訊框突然彈出來並不怎麼友好，但也不至於會造成什麼真實傷害啊。的確如此，但要說明的是，這裡拿資訊框說事僅僅是為了舉個例子，真正的駭客攻擊在XSS中除非惡作劇，不然是不會在惡意植入程式碼中寫上alert（“say something”）的。
在真正的應用中，XSS攻擊可以乾的事情還有很多，這裡舉兩個例子。
竊取網頁瀏覽中的cookie值
在網頁瀏覽中我們常常涉及到使用者登入，登入完畢之後服務端會返回一個cookie值。這個cookie值相當於一個令牌，拿著這張令牌就等同於證明了你是某個使用者。
如果你的cookie值被竊取，那麼攻擊者很可能能夠直接利用你的這張令牌不用密碼就登入你的賬戶。如果想要透過script指令碼獲得當前頁面的cookie值，通常會用到document.cookie。
試想下如果像空間說說中能夠寫入xss攻擊語句，那豈不是看了你說說的人的號你都可以登入（不過某些廠商的cookie有其他驗證措施如：Http-Only保證同一cookie不能被濫用）
劫持流量實現惡意跳轉
這個很簡單，就是在網頁中想辦法插入一句像這樣的語句：
<script>window.location.href="http://www.baidu.com";</script>
那麼所訪問的網站就會被跳轉到百度的首頁。
Xss攻擊方式
- 大小寫繞過
例如：
這個繞過方式的出現是因為網站僅僅只過濾了標籤(Script)，而沒有考慮標籤中的大小寫並不影響瀏覽器的解釋所致。具體的方式就像這樣：
http://192.168.1.102/xss/example2.php?name=<sCript>alert("hey!")</scRipt>
- 利用過濾後返回語句再次構成攻擊語句來繞過
- 並不是只有script標籤才可以插入程式碼
我們利用如下方式：
[http://192.168.1.102/xss/example4.php?name=
src='w.123' onerror='alert("hey!")'>
就可以再次愉快的彈窗。原因很簡單，我們指定的圖片地址根本不存在也就是一定會發生錯誤，這時候onerror裡面的程式碼自然就得到了執行。
以下列舉幾個常用的可插入程式碼的標籤。
<a onmousemove=’do something here’>
當使用者滑鼠移動時即可執行程式碼
<div onmouseover=‘do something here’>
當使用者滑鼠在這個塊上面時即可執行（可以配合weight等引數將div覆蓋頁面，滑鼠不劃過都不行）
- 編碼指令碼程式碼繞過關鍵字過濾
有的時候，伺服器往往會對程式碼中的關鍵字（如alert）進行過濾，這個時候我們可以嘗試將關鍵字進行編碼後再插入，不過直接顯示編碼是不能被瀏覽器執行的，我們可以用另一個語句eval（）來實現。eval()會將編碼過的語句解碼後再執行，簡直太貼心了。
例如alert(1)編碼過後就是
\u0061\u006c\u0065\u0072\u0074(1)
所以構建出來的攻擊語句如下：
http://192.168.1.102/xss/example5.php?name=eval(\u0061\u006c\u0065\u0072\u0074(1))
- 主動閉合標籤實現注入程式碼
- 組合各種方式
Xss 的防範手段
- 首先是過濾。對諸如(script、img、a)等標籤進行過濾。
- 其次是編碼。像一些常見的符號，如<>在輸入的時候要對其進行轉換編碼，這樣做瀏覽器是不會對該標籤進行解釋執行的，同時也不影響顯示效果。
- 最後是限制。透過以上的案例我們不難發現xss攻擊要能達成往往需要較長的字串，因此對於一些可以預期的輸入可以透過限制長度強制截斷來進行防禦。
Spring Boot 防 Xss 程式碼攻擊
從上面可以知道，Xss 攻擊是對入參或者說輸出進行修改，劫持內容達到目的。因此我們需要對整個系統的提交進行過濾和轉義。
spring boot 防範 XSS 攻擊可以使用過濾器，對內容進行轉義，過濾。
這裡就採用Spring boot+Filter的方式實現一個Xss的全域性過濾器
Spring boot實現一個Xss過濾器, 常用的有兩種方式:
第一種：
- 自定義過濾器
- 重寫HttpServletRequestWrapper、重寫getHeader()、getParameter()、getParameterValues()、getInputStream()實現對傳統“鍵值對”傳參方式的過濾
- 重寫getInputStream()實現對Json方式傳參的過濾,也就是@RequestBody引數
第二種：
- 自定義序列化器, 對MappingJackson2HttpMessageConverter 的objectMapper做設定.
重寫JsonSerializer.serialize()實現對出參的過濾 (PS: 資料原樣儲存, 取出來的時候轉義)
重寫JsonDeserializer.deserialize()實現對入參的過濾 (PS: 資料轉義後儲存)
防 XSS 攻擊流程圖
程式碼編寫流程圖：
自定義過濾器
public class XssFilter implements Filter
{
/**
* 排除連結
*/
public List<String> excludes = new ArrayList<>();
@Override
public void init(FilterConfig filterConfig) throws ServletException
{
String tempExcludes = filterConfig.getInitParameter("excludes");
if (StringUtils.isNotEmpty(tempExcludes))
{
String[] url = tempExcludes.split(",");
for (int i = 0; url != null && i < url.length; i++)
{
excludes.add(url[i]);
}
}
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException
{
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse resp = (HttpServletResponse) response;
if (handleExcludeURL(req, resp))
{
// 傳遞過濾器
chain.doFilter(request, response);
return;
}
XssHttpServletRequestWrapper xssRequest = new XssHttpServletRequestWrapper((HttpServletRequest) request);
chain.doFilter(xssRequest, response);
}
private boolean handleExcludeURL(HttpServletRequest request, HttpServletResponse response)
{
String url = request.getServletPath();
String method = request.getMethod();
// GET DELETE 不過濾
if (method == null || HttpMethod.GET.matches(method) || HttpMethod.DELETE.matches(method))
{
return true;
}
return StringUtils.matches(url, excludes);
}
@Override
public void destroy()
{
}
}
上面自定義過濾器需要到的StringUtils 工具類
/**
* 查詢指定字串是否匹配指定字串列表中的任意一個字串
*
* @param str 指定字串
* @param strs 需要檢查的字串陣列
* @return 是否匹配
*/
public static boolean matches(String str, List<String> strs)
{
if (isEmpty(str) || isEmpty(strs))
{
return false;
}
for (String pattern : strs)
{
if (isMatch(pattern, str))
{
return true;
}
}
return false;
}
/**
* 判斷url是否與規則配置:
* ? 表示單個字元;
* * 表示一層路徑內的任意字串，不可跨層級;
* ** 表示任意層路徑;
*
* @param pattern 匹配規則
* @param url 需要匹配的url
* @return
*/
public static boolean isMatch(String pattern, String url)
{
AntPathMatcher matcher = new AntPathMatcher();
return matcher.match(pattern, url);
}
Xss 過濾處理
/**
* XSS過濾處理
*
* @author lh
*/
public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper
{
/**
* @param request
*/
public XssHttpServletRequestWrapper(HttpServletRequest request)
{
super(request);
}
// 重寫獲取引數進行轉義
@Override
public String[] getParameterValues(String name)
{
String[] values = super.getParameterValues(name);
if (values != null)
{
int length = values.length;
String[] escapesValues = new String[length];
for (int i = 0; i < length; i++)
{
// 防xss攻擊和過濾前後空格
escapesValues[i] = EscapeUtil.clean(values[i]).trim();
}
return escapesValues;
}
return super.getParameterValues(name);
}
@Override
public ServletInputStream getInputStream() throws IOException
{
// 非json型別，直接返回
if (!isJsonRequest())
{
return super.getInputStream();
}
// 為空，直接返回
String json = IOUtils.toString(super.getInputStream(), "utf-8");
if (StringUtils.isEmpty(json))
{
return super.getInputStream();
}
// xss過濾
json = EscapeUtil.clean(json).trim();
byte[] jsonBytes = json.getBytes("utf-8");
final ByteArrayInputStream bis = new ByteArrayInputStream(jsonBytes);
return new ServletInputStream()
{
@Override
public boolean isFinished()
{
return true;
}
@Override
public boolean isReady()
{
return true;
}
@Override
public int available() throws IOException
{
return jsonBytes.length;
}
@Override
public void setReadListener(ReadListener readListener)
{
}
@Override
public int read() throws IOException
{
return bis.read();
}
};
}
/**
* 是否是Json請求
*
* @param request
*/
public boolean isJsonRequest()
{
String header = super.getHeader(HttpHeaders.CONTENT_TYPE);
return StringUtils.startsWithIgnoreCase(header, MediaType.APPLICATION_JSON_VALUE);
}
}
轉義Html字元
Clean 方法
public static String clean(String content)
{
return new HTMLFilter().filter(content);
}
HTML 過濾器
/**
* HTML過濾器，用於去除XSS漏洞隱患。
*
* @author lh
*/
public final 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("<>");
// @xxx could grow large... maybe use sesat's ReferenceMap
private static final ConcurrentMap<String, Pattern> P_REMOVE_PAIR_BLANKS = new ConcurrentHashMap<>();
private static final ConcurrentMap<String, Pattern> P_REMOVE_SELF_BLANKS = new ConcurrentHashMap<>();
/**
* 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<>();
/**
* 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;
/**
* 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<>();
a_atts.add("href");
a_atts.add("target");
vAllowed.put("a", a_atts);
final ArrayList<String> 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);
final ArrayList<String> 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" };
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 = false;
}
/**
* Map-parameter configurable constructor.
*
* @param conf map containing configuration. keys match field names.
*/
@SuppressWarnings("unchecked")
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();
}
// ---------------------------------------------------------------
// 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;
s = escapeComments(s);
s = balanceHTML(s);
s = checkTags(s);
s = processRemoveBlanks(s);
// s = validateEntities(s);
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);
// 不追加結束標籤
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);
// these get tallied in processTag
// (remember to reset before subsequent calls to filter method)
final StringBuilder sBuilder = new StringBuilder(buf.toString());
for (String key : vTagCounts.keySet())
{
for (int ii = 0; ii < vTagCounts.get(key); ii++)
{
sBuilder.append("</").append(key).append(">");
}
}
s = sBuilder.toString();
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))
{
final StringBuilder params = new StringBuilder();
final Matcher m2 = P_QUOTED_ATTRIBUTES.matcher(body);
final Matcher m3 = P_UNQUOTED_ATTRIBUTES.matcher(body);
final List<String> paramNames = new ArrayList<>();
final List<String> 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 (allowedAttribute(name, paramName))
{
if (inArray(paramName, vProtocolAtts))
{
paramValue = processParamProtocol(paramValue);
}
params.append(' ').append(paramName).append("=\\\"").append(paramValue).append("\\\"");
}
}
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);
if (s.startsWith("#//"))
{
s = "#" + s.substring(3);
}
}
}
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); // (<|$)
// 不替換雙引號為"，防止json格式無效 regexReplace(P_QUOTE, """, two)
m.appendReplacement(buf, Matcher.quoteReplacement(one + two + three));
}
m.appendTail(buf);
return buf.toString();
}
else
{
return s;
}
}
private String checkEntity(final String preamble, final String term)
{
return ";".equals(term) && isValidEntity(preamble) ? '&' + preamble : "&" + preamble;
}
private boolean isValidEntity(final String entity)
{
return inArray(entity, vAllowedEntities);
}
private static boolean inArray(final String s, final String[] array)
{
for (String item : array)
{
if (item != null && item.equals(s))
{
return true;
}
}
return false;
}
private boolean allowed(final String name)
{
return (vAllowed.isEmpty() || vAllowed.containsKey(name)) && !inArray(name, vDisallowed);
}
private boolean allowedAttribute(final String name, final String paramName)
{
return allowed(name) && (vAllowed.isEmpty() || vAllowed.get(name).contains(paramName));
}
}
註冊配置過濾器bean
註冊bean
@Configuration
public class FilterConfig
{
@Value("${xss.excludes}")
private String excludes;
@Value("${xss.urlPatterns}")
private String urlPatterns;
@SuppressWarnings({ "rawtypes", "unchecked" })
@Bean
@ConditionalOnProperty(value = "xss.enabled", havingValue = "true")
public FilterRegistrationBean xssFilterRegistration()
{
FilterRegistrationBean registration = new FilterRegistrationBean();
registration.setDispatcherTypes(DispatcherType.REQUEST);
registration.setFilter(new XssFilter());
//新增過濾路徑
registration.addUrlPatterns(StringUtils.split(urlPatterns, ","));
registration.setName("xssFilter");
registration.setOrder(FilterRegistrationBean.HIGHEST_PRECEDENCE);
//設定初始化引數
Map<String, String> initParameters = new HashMap<String, String>();
initParameters.put("excludes", excludes);
registration.setInitParameters(initParameters);
return registration;
}
@SuppressWarnings({ "rawtypes", "unchecked" })
@Bean
public FilterRegistrationBean someFilterRegistration()
{
FilterRegistrationBean registration = new FilterRegistrationBean();
registration.setFilter(new RepeatableFilter());
registration.addUrlPatterns("/*");
registration.setName("repeatableFilter");
registration.setOrder(FilterRegistrationBean.LOWEST_PRECEDENCE);
return registration;
}
}
檔案配置：
# 防止XSS攻擊
xss:
# 過濾開關
enabled: true
# 排除連結（多個用逗號分隔）
excludes: /system/notice
# 匹配連結
urlPatterns: /system/*,/monitor/*,/tool/*
這個時候就可以了，我們就可以進行測試了
轉義和反轉義工具
/**
* 轉義和反轉義工具類
*
* @author lh
*/
public class EscapeUtil
{
public static final String RE_HTML_MARK = "(<[^<]*?>)|(<[\\s]*?/[^<]*?>)|(<[^<]*?/[\\s]*?>)";
private static final char[][] TEXT = new char[64][];
static
{
for (int i = 0; i < 64; i++)
{
TEXT[i] = new char[] { (char) i };
}
// special HTML characters
TEXT['\''] = "'".toCharArray(); // 單引號
TEXT['"'] = """.toCharArray(); // 雙引號
TEXT['&'] = "&".toCharArray(); // &符
TEXT['<'] = "<".toCharArray(); // 小於號
TEXT['>'] = ">".toCharArray(); // 大於號
}
/**
* 轉義文字中的HTML字元為安全的字元
*
* @param text 被轉義的文字
* @return 轉義後的文字
*/
public static String escape(String text)
{
return encode(text);
}
/**
* 還原被轉義的HTML特殊字元
*
* @param content 包含轉義符的HTML內容
* @return 轉換後的字串
*/
public static String unescape(String content)
{
return decode(content);
}
/**
* 清除所有HTML標籤，但是不刪除標籤內的內容
*
* @param content 文字
* @return 清除標籤後的文字
*/
public static String clean(String content)
{
return new HTMLFilter().filter(content);
}
/**
* Escape編碼
*
* @param text 被編碼的文字
* @return 編碼後的字元
*/
private static String encode(String text)
{
if (StringUtils.isEmpty(text))
{
return StringUtils.EMPTY;
}
final StringBuilder tmp = new StringBuilder(text.length() * 6);
char c;
for (int i = 0; i < text.length(); i++)
{
c = text.charAt(i);
if (c < 256)
{
tmp.append("%");
if (c < 16)
{
tmp.append("0");
}
tmp.append(Integer.toString(c, 16));
}
else
{
tmp.append("%u");
if (c <= 0xfff)
{
// issue#I49JU8@Gitee
tmp.append("0");
}
tmp.append(Integer.toString(c, 16));
}
}
return tmp.toString();
}
/**
* Escape解碼
*
* @param content 被轉義的內容
* @return 解碼後的字串
*/
public static String decode(String content)
{
if (StringUtils.isEmpty(content))
{
return content;
}
StringBuilder tmp = new StringBuilder(content.length());
int lastPos = 0, pos = 0;
char ch;
while (lastPos < content.length())
{
pos = content.indexOf("%", lastPos);
if (pos == lastPos)
{
if (content.charAt(pos + 1) == 'u')
{
ch = (char) Integer.parseInt(content.substring(pos + 2, pos + 6), 16);
tmp.append(ch);
lastPos = pos + 6;
}
else
{
ch = (char) Integer.parseInt(content.substring(pos + 1, pos + 3), 16);
tmp.append(ch);
lastPos = pos + 3;
}
}
else
{
if (pos == -1)
{
tmp.append(content.substring(lastPos));
lastPos = content.length();
}
else
{
tmp.append(content.substring(lastPos, pos));
lastPos = pos;
}
}
}
return tmp.toString();
}
public static void main(String[] args)
{
String html = "<script>alert(1);</script>";
String escape = EscapeUtil.escape(html);
// String html = "<scr<script>ipt>alert(\"XSS\")</scr<script>ipt>";
// String html = "<123";
// String html = "123>";
System.out.println("clean: " + EscapeUtil.clean(html));
System.out.println("escape: " + escape);
System.out.println("unescape: " + EscapeUtil.unescape(escape));
}
測試類
Controller 測試類
@Slf4j
@RestController
public class XssController {
//鍵值對
@PostMapping("xssFilter")
public String xssFilter(String name, String info) {
log.error(name + "---" + info);
return name + "---" + info;
}
//實體
@PostMapping("modelXssFilter")
public People modelXssFilter(@RequestBody UserEntity user) {
log.error(user.getUserName() + "---" + user.getMobile());
return user;
}
//不轉義
@PostMapping("open/xssFilter")
public String openXssFilter(String name) {
return name;
}
//不轉義2
@PostMapping("open2/xssFilter")
public String open2XssFilter(String name) {
return name;
}
// 這裡最好單獨建立實體，這裡這裡只是演示
@ApiModel(value = "UserEntity", description = "使用者實體")
class UserEntity
{
@ApiModelProperty("使用者ID")
private Integer userId;
@ApiModelProperty("使用者名稱稱")
private String username;
@ApiModelProperty("使用者密碼")
private String password;
@ApiModelProperty("使用者手機")
private String mobile;
public UserEntity()
{
}
public UserEntity(Integer userId, String username, String password, String mobile)
{
this.userId = userId;
this.username = username;
this.password = password;
this.mobile = mobile;
}
public Integer getUserId()
{
return userId;
}
public void setUserId(Integer userId)
{
this.userId = userId;
}
public String getUsername()
{
return username;
}
public void setUsername(String username)
{
this.username = username;
}
public String getPassword()
{
return password;
}
public void setPassword(String password)
{
this.password = password;
}
public String getMobile()
{
return mobile;
}
public void setMobile(String mobile)
{
this.mobile = mobile;
}
}
}
總結
到這裡spring boot 結合過濾器實現對Xss 攻擊的防範就實現了，Xss 攻擊總體來說危害還是挺大，對網站安全有較大風險，容易造成個人，公司等損失。
Xss 是較為平常的攻擊，我們對網站，資料安全始終在奮進和最佳化的路上，確保網路環境安全，乾淨。
上面的攻擊手法大家可不要對其他網站進行嘗試哦！保護網路環境，平安你我他。
另外感謝大家的閱讀：有任何問題，錯誤，想法歡迎大家留言評論。