安全漏洞描述
恶意攻击者往Web页面里插入恶意Script代码，当用户浏览该页时，嵌入其中Web里面的Script代码会被执行，进而窃取到管理员用户权限等。
风险等级：高
解决办法
- 对网页端输入的特殊字符过滤 建议过滤的关键字为： [1]’单引号
[2]”双引号
[3]/斜杠
[4]反斜杠
[5])括号
[6];分号
[7][中括号
[8]<尖括号
[9]>尖括号
比如把<编码为< - 在cookie中加入httponly属性可以在一定程度上保护用户的cookie，减少出现XSS时损失。
一段简易的字符过滤程序
function htmlEncode(str){
var s = "";
if (str.length == 0) return "";
s = str.replace(/&/g, "&");
s = s.replace(//g, ">");
s = s.replace(/ /g, " ");
s = s.replace(/\'/g, "'");
s = s.replace(/\"/g, """);
return s;
}
- 在服务端增加filter过滤
通过自定义filter的方式拦截过滤请求
public class XssFilter implements Filter
{
/**
* 排除链接
*/
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))
{
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 不过滤
if (method == null || HttpMethod.GET.matches(method) || HttpMethod.DELETE.matches(method))
{
return true;
}
return StringUtils.matches(url, excludes);
}
}
在wrapper里过滤参数
public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper
{
/**
* @param request
*/
public XssHttpServletRequestWrapper(HttpServletRequest request)
{
super(request);
}
@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攻击和过滤前后空格
escapesValues[i] = EscapeUtil.clean(values[i]).trim();
}
return escapesValues;
}
return super.getParameterValues(name);
}
@Override
public ServletInputStream getInputStream() throws IOException
{
// 非json类型，直接返回
if (!isJsonRequest())
{
return super.getInputStream();
}
// 为空，直接返回
String json = IOUtils.toString(super.getInputStream(), "utf-8");
if (StringUtils.isEmpty(json))
{
return super.getInputStream();
}
// xss过滤
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请求
*
* @param request
*/
public boolean isJsonRequest()
{
String header = super.getHeader(HttpHeaders.CONTENT_TYPE);
return StringUtils.startsWithIgnoreCase(header, MediaType.APPLICATION_JSON_VALUE);
}
}
xssUtil
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(); // 单引号
TEXT['"'] = """.toCharArray(); // 双引号
TEXT['&'] = "&".toCharArray(); // &符
TEXT['<'] = "<".toCharArray(); // 小于号
TEXT['>'] = ">".toCharArray(); // 大于号
}
/**
* 转义文本中的HTML字符为安全的字符
*
* @param text 被转义的文本
* @return 转义后的文本
*/
public static String escape(String text)
{
return encode(text);
}
/**
* 还原被转义的HTML特殊字符
*
* @param content 包含转义符的HTML内容
* @return 转换后的字符串
*/
public static String unescape(String content)
{
return decode(content);
}
/**
* 清除所有HTML标签，但是不删除标签内的内容
*
* @param content 文本
* @return 清除标签后的文本
*/
public static String clean(String content)
{
return new HTMLFilter().filter(content);
}
/**
* Escape编码
*
* @param text 被编码的文本
* @return 编码后的字符
*/
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解码
*
* @param content 被转义的内容
* @return 解码后的字符串
*/
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 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);
// 不追加结束标签
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));
}
}
前后端组合使用，可解决xss问题
安全无小事！！！
文档信息
- 本文作者：寒澈
- 本文链接：https://www.hancher.top/2023/06/21/reactive_xss/
- 版权声明：自由转载-非商用-非衍生-保持署名（创意共享3.0许可证）